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Lymphatic filariasis (LF), a morbid disease caused by the tissue-invasive nematodes Wuchereria bancrofti, Brugia malayi, and Brugia timori, affects millions of people worldwide. Global eradication efforts have significantly reduced worldwide prevalence, but complete elimination has been hampered by limitations of current anti-filarial drugs and the lack of a vaccine. The goal of this study was to evaluate B. malayi intestinal UDP-glucuronosyltransferase (Bm-UGT) as a potential therapeutic target. To evaluate whether Bm-UGT is essential for adult filarial worms, we inhibited its expression using siRNA. This resulted in a 75% knockdown of Bm-ugt mRNA for 6 days and almost complete suppression of detectable Bm-UGT by immunoblot. Reduction in Bm-UGT expression resulted in decreased worm motility for 6 days, 70% reduction in microfilaria release from adult worms, and significant reduction in adult worm metabolism as detected by MTT assays. Because prior allergic-sensitization to a filarial antigen would be a contraindication for its use as a vaccine candidate, we tested plasma from infected and endemic normal populations for Bm-UGT-specific IgE using a luciferase immunoprecipitation assay. All samples (n = 35) tested negative. We then tested two commercially available medicines known to be broad inhibitors of UGTs, sulfinpyrazone and probenecid, for in vitro activity against B. malayi. There were marked macrofilaricidal effects at concentrations achievable in humans and very little effect on microfilariae. In addition, we observed that probenecid and sulfinpyrazone exhibit a synergistic macrofilaricidal effect when used in combination with albendazole. The results of this study demonstrate that Bm-UGT is an essential protein for adult worm survival. Lack of prior IgE sensitization in infected and endemic populations suggest it may be a feasible vaccine candidate. The finding that sulfinpyrazone and probenecid have in vitro effects against adult B. malayi worms suggests that these medications have promise as potential macrofilaricides in humans. [ABSTRACT FROM AUTHOR]

Zika virus (ZIKV) is a newly-identified infectious cause of congenital disease. Transplacental transfer of maternal IgG to the fetus plays an important role in preventing many neonatal infections. However, antibody transfer may also have negative consequences, such as mediating enhancement of flavivirus infections in early life, or trafficking of virus immune complexes to the fetal compartment. ZIKV infection produces placental pathology which could lead to impaired IgG transfer efficiency as occurs in other maternal infections, such as HIV-1 and malaria. In this study, we asked whether ZIKV infection during pregnancy impairs transplacental transfer of IgG. We enrolled pregnant women with fever or rash in a prospective cohort in Vitoria, Brazil during the recent ZIKV epidemic. ZIKV and dengue virus (DENV)-specific IgG, ZIKV and DENV neutralizing antibodies, and routine vaccine antigen-specific IgG were measured in maternal samples collected around delivery and 20 paired cord blood samples. We concluded that 8 of these mothers were infected with ZIKV during pregnancy and 12 were ZIKV-uninfected. The magnitude of flavivirus-specific IgG, neutralizing antibody, and vaccine-elicited IgG were highly correlated between maternal plasma and infant cord blood in both ZIKV-infected and -uninfected mother-infant pairs. Moreover, there was no difference in the magnitude of plasma flavivirus-specific IgG levels between mothers and infants regardless of ZIKV infection status. Our data suggests that maternal ZIKV infection during pregnancy does not impair the efficiency of placental transfer of flavivirus-specific, functional, and vaccine-elicited IgG. These findings have implications for the neonatal outomes of maternal ZIKV infection and optimal administration of antibody-based ZIKV vaccines and therapeutics. [ABSTRACT FROM AUTHOR]

Background: Schistosoma mansoni is one of the most common helminth infections affecting a large population of people in sub-Saharan Africa. This helminth infection is known to cause immunomodulation which has affected the efficacy of a number of vaccines. This study examined whether a chronic schistosoma infection has an effect on the immunogenicity of HPV vaccine which is currently administered to girls and women aged 9 to 24. Little is known about the immune responses of the HPV vaccine in individuals with chronic schistosomiasis. Methods: This study was carried out at the Institute of Primate Research (IPR) and involved an Olive baboon model. The experimental animals were randomly placed into three groups (n = 3–4); Two groups were infected with S. mansoni cercaria, and allowed to reach chronic stage (week 12 onwards), at week 13 and 14 post-infection, one group was treated with 80mg/kg of praziquantel (PZQ). Sixty four weeks post schistosoma infection, all groups received 2 doses of the Cervarix HPV vaccine a month apart. Specific immune responses to the HPV and parasite specific antigens were evaluated. Results: Animals with chronic S. mansoni infection elicited significantly reduced levels of HPV specific IgG antibodies 8 weeks after vaccination compared the PZQ treated and uninfected groups. There was no significant difference in cellular proliferation nor IL-4 and IFN-γ production in all groups. Conclusion: Chronic S. mansoni infection results in reduction of protective HPV specific IgG antibodies in a Nonhuman Primate model, suggesting a compromised effect of the vaccine. Treatment of schistosomiasis infection with PZQ prior to HPV vaccination, however, reversed this effect supporting anti-helminthic treatment before vaccination. [ABSTRACT FROM AUTHOR]

Bacillus anthracis and Yersinia pestis are zoonotic bacteria capable of causing severe and sometimes fatal infections in animals and humans. Although considered as diseases of antiquity in industrialized countries due to animal and public health improvements, they remain endemic in vast regions of the world disproportionally affecting the poor. These pathogens also remain a serious threat if deployed in biological warfare. A single vaccine capable of stimulating rapid protection against both pathogens would be an extremely advantageous public health tool. We produced multiple-antigen fusion proteins (MaF1 and MaF2) containing protective regions from B. anthracis protective antigen (PA) and lethal factor (LF), and from Y. pestis V antigen (LcrV) and fraction 1 (F1) capsule. The MaF2 sequence was also expressed from a plasmid construct (pDNA-MaF2). Immunogenicity and protective efficacy were investigated in mice following homologous and heterologous prime-boost immunization. Antibody responses were determined by ELISA and anthrax toxin neutralization assay. Vaccine efficacy was determined against lethal challenge with either anthrax toxin or Y. pestis. Both constructs elicited LcrV and LF-specific serum IgG, and MaF2 elicited toxin-neutralizing antibodies. Immunizations with MaF2 conferred 100% and 88% protection against Y. pestis and anthrax toxin, respectively. In contrast, pDNA-MaF2 conferred only 63% protection against Y. pestis and no protection against anthrax toxin challenge. pDNA-MaF2-prime MaF2-boost induced 75% protection against Y. pestis and 25% protection against anthrax toxin. Protection was increased by the molecular adjuvant CARDif. In conclusion, MaF2 is a promising multi-antigen vaccine candidate against anthrax and plague that warrants further investigation. [ABSTRACT FROM AUTHOR]

Background: To be transmitted to vertebrate hosts via the saliva of their vectors, arthropod-borne viruses have to cross several barriers in the mosquito body, including the midgut infection and escape barriers. Yellow fever virus (YFV) belongs to the genus Flavivirus, which includes human viruses transmitted by Aedes mosquitoes, such as dengue and Zika viruses. The live-attenuated YFV-17D vaccine has been used safely and efficiently on a large scale since the end of World War II. Early studies have shown, using viral titration from salivary glands of infected mosquitoes, that YFV-17D can infect Aedes aegypti midgut, but does not disseminate to other tissues. Methodology/Principal findings: Here, we re-visited this issue using a panel of techniques, such as RT-qPCR, Western blot, immunofluorescence and titration assays. We showed that YFV-17D replication was not efficient in Aedes aegypti midgut, as compared to the clinical isolate YFV-Dakar. Viruses that replicated in the midgut failed to disseminate to secondary organs. When injected into the thorax of mosquitoes, viruses succeeded in replicating into midgut-associated tissues, suggesting that, during natural infection, the block for YFV-17D replication occurs at the basal membrane of the midgut. Conclusions/Significance: The two barriers associated with Ae. aegypti midgut prevent YFV-17D replication. Our study contributes to our basic understanding of vector–pathogen interactions and may also aid in the development of non-transmissible live virus vaccines. [ABSTRACT FROM AUTHOR]

Genotype III (GIII) Japanese encephalitis virus (JEV) predominance has gradually been replaced by genotype I (GI) over the last 20 years in many Asian countries. This genotype shift raises concerns about the protective efficacy of Japanese encephalitis (JE) vaccines, as all of the currently licensed JE vaccines are derived from GIII strains. In this study, we conducted vaccination-challenge protection assays to evaluate the cross-protective efficacy of GI- or GIII-derived vaccines against the challenge of a heterologous genotype using a mouse challenge model. Titration of the neutralizing antibodies elicited by SA14-14-2 live-attenuated JE vaccine (SA14-14-2 vaccine), a GIII-derived vaccine, indicated that the titer of neutralizing antibodies specific to heterologous genotype GI stain was significantly lower than that specific to homologous genotype GIII strain in both pigs and mice immunized with the SA14-14-2 vaccine. Vaccination of mice with SA14-14-2 vaccine or a GIII-inactivated vaccine at high and medium doses completely protected vaccinated mice against challenge with the homologous genotype GIII strains, but failed to provide the vaccinated mice complete protection against the challenge of heterologous genotype GI strains. The protection rates against GI strain challenge were 60%–80%, showing that these vaccines were partially protective against GI strain challenge. Additionally, vaccination of mice with a GI-inactivated vaccine conferred 100% protection against the challenge of homologous genotype GI strains, but 50%–90% protection against the challenge of heterologous genotype GIII strains, showing a reduced protective efficacy of a GI-derived vaccine against GIII strain challenge. Overall, these observations demonstrated a partial cross-protection between GI and GIII strains and suggested a potential need for new JE vaccine strategies, including options like a bivalent vaccine, to control both genotype infection. [ABSTRACT FROM AUTHOR]

Background: Oral cholera vaccine (OCV) containing killed Vibrio cholerae O1 and O139 organisms (Bivalent-OCV; Biv-OCV) are playing a central role in global cholera control strategies. OCV is currently administered in a 2-dose regimen (day 0 and 14). There is a growing body of evidence that immune responses targeting the O-specific polysaccharide (OSP) of V. cholerae mediate protection against cholera. There are limited data on anti-OSP responses in recipients of Biv-OCV. We assessed serum antibody responses against O1 OSP, as well as antibody secreting cell (ASC) responses (a surrogate marker for mucosal immunity) and memory B cell responses in blood of adult recipients of Biv-OCV in Dhaka, Bangladesh. Methodology/Principal findings: We enrolled 30 healthy adults in this study and administered two doses of OCV (Shanchol) at days 0 and 14. Blood samples were collected before vaccination (day 0) and 7 days after each vaccination (day 7 and day 21), as well as on day 44. Serum responses were largely IgA with minimal IgG and IgM responses in this population. There was no appreciable boosting following day 14 vaccination. There were significant anti-OSP IgA ASC responses on day 7 following the first vaccination, but none after the second immunization. Anti-OSP IgA memory B cell responses were detectable 30 days after completion of the vaccination series, with no evident induction of IgG memory responses. In this population, anti-Ogawa OSP responses were more prominent than anti-Inaba responses, perhaps reflecting impact of previous exposure. Serum anti-OSP responses returned to baseline within 30 days of completing the vaccine series. Conclusion: Our results call into question the utility of the 2-dose regimen separated by 14 days in adults in cholera endemic areas, and also suggest that Biv-OCV-induced immune responses targeting OSP are largely IgA in this highly endemic cholera area. Studies in children in cholera-endemic areas need to be performed. Protective efficacy that extends for more than a month after vaccination presumably is mediated by direct mucosal immune response which is not assessed in this study. Our results suggest a single dose of OCV in adults in a cholera endemic zone may be sufficient to mediate at least short-term protection. [ABSTRACT FROM AUTHOR]

Nipah virus (NiV) is a highly pathogenic re-emerging virus that causes outbreaks in South East Asia. Currently, no approved and licensed vaccine or antivirals exist. Here, we investigated the efficacy of ChAdOx1 NiVB, a simian adenovirus-based vaccine encoding NiV glycoprotein (G) Bangladesh, in Syrian hamsters. Prime-only as well as prime-boost vaccination resulted in uniform protection against a lethal challenge with NiV Bangladesh: all animals survived challenge and we were unable to find infectious virus either in oral swabs, lung or brain tissue. Furthermore, no pathological lung damage was observed. A single-dose of ChAdOx1 NiVB also prevented disease and lethality from heterologous challenge with NiV Malaysia. While we were unable to detect infectious virus in swabs or tissue of animals challenged with the heterologous strain, a very limited amount of viral RNA could be found in lung tissue by in situ hybridization. A single dose of ChAdOx1 NiVB also provided partial protection against Hendra virus and passive transfer of antibodies elicited by ChAdOx1 NiVB vaccination partially protected Syrian hamsters against NiV Bangladesh. From these data, we conclude that ChAdOx1 NiVB is a suitable candidate for further NiV vaccine pre-clinical development. [ABSTRACT FROM AUTHOR]

Oral cholera vaccines (OCVs) are being increasingly employed, but current killed formulations generally require multiple doses and lack efficacy in young children. We recently developed a new live-attenuated OCV candidate (HaitiV) derived from a Vibrio cholerae strain isolated during the 2010 Haiti cholera epidemic. HaitiV exhibited an unexpected probiotic-like activity in infant rabbits, preventing intestinal colonization and disease by wild-type V. cholerae before the onset of adaptive immunity. However, it remained unknown whether HaitiV would behave similarly to other OCVs to stimulate adaptive immunity against V. cholerae. Here, we orally immunized adult germ-free female mice to test HaitiV’s immunogenicity. HaitiV safely and stably colonized vaccinated mice and induced known adaptive immune correlates of cholera protection within 14 days of administration. Pups born to immunized mice were protected against lethal challenges of both homologous and heterologous V. cholerae strains. Cross-fostering experiments revealed that protection was not dependent on vaccine colonization in or transmission to the pups. These findings demonstrate the protective immunogenicity of HaitiV and support its development as a new tool for limiting cholera. [ABSTRACT FROM AUTHOR]

Background: The liver fluke Opisthorchis viverrini infects several million people in Southeast Asia. Adult flukes live in the bile ducts of humans, where they cause hepatobiliary pathology, including cholangiocarcinoma. Here, we investigated the potential of extracellular vesicles (EVs) secreted by the fluke and defined recombinant proteins derived from EVs to generate protective immunity in a hamster vaccination-challenge model. Methodology/Principal findings: EVs isolated from the excretory-secretory products of O. viverrini and two recombinant EV surface proteins encoding the large extracellular loops (LEL) of Ov-TSP-2 (rOv-TSP-2) and Ov-TSP-3 (rOv-TSP-3) were adjuvanted and used to vaccinate hamsters intraperitoneally followed by challenge infection with O. viverrini metacercariae. The number of adult flukes recovered from hamsters immunized with EVs, rOv-TSP-2, rOv-TSP-3 and rOv-TSP-2+rOv-TSP-3 were significantly reduced compared to control animals vaccinated with adjuvant alone. The number of eggs per gram feces was also significantly reduced in hamsters vaccinated with rOv-TSP-2 compared to controls, but no significant differences were found in the other groups. The average length of worms recovered from hamsters vaccinated with EVs, rOv-TSP-2 and rOv-TSP-3 was significantly shorter than that of worms recovered from the control group. Anti-EV IgG levels in serum and bile were significantly higher in hamsters vaccinated with EVs compared to control hamsters both pre- and post-challenge. In addition, levels of anti-rOv-TSP antibodies in the serum and bile were significantly higher than control hamsters both pre- and post-challenge. Finally, antibodies against rOv-TSP-2 and rOv-TSP-3 blocked uptake of EVs by human primary cholangiocyte in vitro, providing a plausible mechanism by which these vaccines exert partial efficacy and reduce the intensity of O. viverrini infection. Conclusion/Significance: Liver fluke EVs and recombinant tetraspanins derived from the EV surface when administered to hamsters induce antibody responses that block EV uptake by target bile duct cells and exert partial efficacy and against O. viverrini challenge. [ABSTRACT FROM AUTHOR]

Background: Globally, vaccine-preventable diseases remain a significant cause of early childhood mortality despite concerted efforts to improve vaccine coverage. One reason for impaired protection may be the influence of prenatal exposure to parasitic antigens on the developing immune system. Prior research had shown a decrease in infant vaccine response after in utero parasite exposure among a maternal cohort without aggressive preventive treatment. This study investigated the effect of maternal parasitic infections on infant vaccination in a more recent setting of active anti-parasitic therapy. Methodology/Principal findings: From 2013–2015, 576 Kenyan women were tested in pregnancy for malaria, soil-transmitted helminths, filaria, and S. haematobium, with both acute and prophylactic antiparasitic therapies given. After birth, 567 infants received 10-valent S. pneumoniae conjugate vaccine and pentavalent vaccine for hepatitis B, pertussis, tetanus, H. influenzae type B (Hib) and C. diphtheriae toxoid (Dp-t) at 6, 10, and 14 weeks. Infant serum samples from birth, 10 and 14 weeks, and every six months until age three years, were analyzed using a multiplex bead assay to quantify IgG for Hib, Dp-t, and the ten pneumococcal serotypes. Antenatal parasitic prevalence was high; 461 women (80%) had at least one and 252 (43.6%) had two or more infections during their pregnancy, with the most common being malaria (44.6%), S. haematobium (43.9%), and hookworm (29.2%). Mixed models comparing influence of infection on antibody concentration revealed no effect of prenatal infection status for most vaccine outcomes. Prevalences of protective antibody concentrations after vaccination were similar among the prenatal exposure groups. Conclusions/Significance: These findings are in contrast with results from our prior cohort study performed when preventive anti-parasite treatment was less frequently given. The results suggest that the treatment of maternal infections in pregnancy may be able to moderate the previously observed effect of antenatal maternal infections on infant vaccine responses. [ABSTRACT FROM AUTHOR]

Background: Schistosoma infection is associated with immune modulation that can influence responses to non-schistosome antigens. Vaccine responses may be impaired in S. mansoni-infected individuals. We investigated effects of S. mansoni infection on responses to childhood measles catch-up immunisation and of praziquantel treatment on this outcome in a randomised trial. Methodology: The Immune Modulation and Childhood Immunisation (IMoChI) study was based in Entebbe, Uganda. Children aged 3–5 years (193 S. mansoni-infected and 61 uninfected) were enrolled. Infected children were randomised in a 1:1:1 ratio to receive praziquantel 2 weeks before, at time of, or 1 week after, measles catch-up immunisation. Plasma anti-measles IgG was measured at enrolment, 1 week and 24 weeks after measles immunisation. Primary outcomes were IgG levels and percentage of participants with levels considered protective against measles. Results: Anti-measles IgG levels increased following immunisation, but at 1 week post-immunisation S. mansoni-infected, compared to uninfected, children had lower levels of anti-measles IgG (adjusted geometric mean ratio (aGMR) 0.4 [95% CI 0.2–0.7]) and the percentage with protective antibody levels was also lower (adjusted odds ratio 0.1 [0–0.9]). Among S. mansoni-infected children, anti-measles IgG one week post-immunisation was higher among those treated with praziquantel than among those who were not yet treated (treatment before immunisation, aGMR 2.3 [1.5–4.8]; treatment at immunisation aGMR 1.8 [1.1–3.5]). At 24 weeks post-immunisation, IgG levels did not differ between the trial groups, but tended to be lower among previously-infected children who were still S mansoni stool-positive than among those who became stool-negative. Conclusions and significance: Our findings suggest that S. mansoni infection among pre-school children is associated with a reduced antibody response to catch-up measles immunisation, and that praziquantel treatment improves the response. S. mansoni infection may contribute to impaired vaccine responses in endemic populations; effective schistosomiasis control may be beneficial for vaccine efficacy. This should be further explored. Trial registration: . [ABSTRACT FROM AUTHOR]

Mayaro virus (MAYV) of the genus alphavirus is a mosquito-transmitted emerging infectious disease that causes an acute febrile illness, rash, headaches, and nausea that may turn into incapacitating, persistent arthralgias in some victims. Since its discovery in Trinidad in 1954, cases of MAYV infection have largely been confined there and to the northern countries of South America, but recently, MAYV cases have been reported in some island nations in the Caribbean Sea. Accompanying these reports is evidence that new vectors, including Aedes spp. mosquitos, recently implicated in the global spread of Zika and chikungunya viruses, are competent for MAYV transmission, which, if true, could facilitate the spread of MAYV beyond its current range. Despite its status as an emerging virus, there are no licensed vaccines to prevent MAYV infection nor therapeutics to treat it. Here, we describe the development and testing of a novel DNA vaccine, scMAYV-E, that encodes a synthetically-designed consensus MAYV envelope sequence. In vivo electroporation-enhanced immunization of mice with this vaccine induced potent humoral responses including neutralizing antibodies as well as robust T-cell responses to multiple epitopes in the MAYV envelope. Importantly, these scMAYV-E-induced immune responses protected susceptible mice from morbidity and mortality following a MAYV challenge. [ABSTRACT FROM AUTHOR]

The bivalent killed whole-cell oral cholera vaccine (BivWC) is being increasingly used to prevent cholera. The presence of O-antigen-specific memory B cells (MBC) has been associated with protective immunity against cholera, yet MBC responses have not been evaluated after BivWC vaccination. To address this knowledge gap, we measured V. cholerae O1-antigen MBC responses following BivWC vaccination. Adults in St. Marc, Haiti, received 2 doses of the BivWC vaccine, Shanchol, two weeks apart. Participants were invited to return at days 7, 21, 44, 90, 180 and 360 after the initial vaccination. Serum antibody and MBC responses were assessed at each time-point before and following vaccination. We observed that vaccination with BivWC resulted in significant O-antigen specific MBC responses to both Ogawa and Inaba serotypes that were detected by day 21 and remained significantly elevated over baseline for up to 12 months following vaccination. The BivWC oral cholera vaccine induces durable MBC responses to the V. cholerae O1-antigen. This suggests that long-term protection observed following vaccination with BivWC could be mediated or maintained by MBC responses. [ABSTRACT FROM AUTHOR]

Chikungunya fever (CHIKF) is an emerging infectious disease caused by an alphavirus transmitted by Aedes spp. mosquitoes. Because mosquito control programs are not highly efficient for outbreak containment, vaccines are essential to reduce the burden of disease. Although no licensed vaccine against CHIKF is yet available, many highly promising candidates are undergoing preclinical studies, and a few of them have been tested in human trials of phase 1 or 2. Here, we review recent findings regarding the need for a CHIKF vaccine and provide an update on vaccines nearing or having entered clinical trials. We also address needs to tackle bottlenecks to vaccine development—including scientific and financial barriers—and to accelerate the development of vaccines; several actions should be taken: (i) design efficacy trials to be conducted during the course of outbreaks; (ii) evaluate the opportunity for adopting the “animal rule”for demonstration of efficacy for regulatory purposes; (iii) strengthen the collective commitment of nations, international organizations, potential donors and industry; (iv) stimulate public and/or private partnerships to invest in vaccine development and licensure; and (v) identify potential markets for an effective and safe CHIKF vaccine. [ABSTRACT FROM AUTHOR]

Background: Urinary schistosomiasis, the result of infection by Schistosoma haematobium (Sh), remains a major global health concern. A schistosome vaccine could represent a breakthrough in schistosomiasis control strategies, which are presently based on treatment with praziquantel (PZQ). We report the safety and efficacy of the vaccine candidate recombinant 28-kDa glutathione S-transferase of Sh (rSh28GST) designated as Bilhvax, in a phase 3 trial conducted in Senegal. Methods and findings: After clearance of their ongoing schistosomiasis infection with two doses of PZQ, 250 children aged 6–9 years were randomized to receive three subcutaneous injections of either rSh28GST/Alhydrogel (Bilhvax group) or Alhydrogel alone (control group) at week 0 (W0), W4, and W8 and then a booster at W52 (one year after the first injection). PZQ treatment was given at W44, according to previous phase 2 results. The primary endpoint of the analysis was efficacy, evaluated as a delay of recurrence of urinary schistosomiasis, defined by a microhematuria associated with at least one living Sh egg in urine from baseline to W152. During the 152-week follow-up period, there was no difference between study arms in the incidence of serious adverse events. The median follow-up time for subjects without recurrence was 22.9 months for the Bilhvax group and 18.8 months for the control group (log-rank p = 0.27). At W152, 108 children had experienced at least one recurrence in the Bilhvax group versus 112 in the control group. Specific immunoglobulin (Ig)G1, IgG2, and IgG4, but not IgG3 or IgA titers, were increased in the vaccine group. Conclusions: While Bilhvax was immunogenic and well tolerated by infected children, a sufficient efficacy was not reached. The lack of effect may be the result of several factors, including interference by individual PZQ treatments administered each time a child was found infected, or the chosen vaccine-injection regimen favoring blocking IgG4 rather than protective IgG3 antibodies. These observations contrasting with results obtained in experimental models will help in the design of future trials. Trial registration: ClinicalTrials.gov [ABSTRACT FROM AUTHOR]

Background: Recent studies demonstrate that rabies post-exposure prophylaxis (RPEP) in international travelers is suboptimal, with only 5–20% of travelers receiving rabies immune globulin (RIG) in the country of exposure when indicated. We hypothesized that travelers may not be receiving RIG appropriately, and practices may vary between countries. We aim to describe the characteristics of travelers who received RIG and/or RPEP during travel. Methodology/Principal findings: We conducted a multi-center review of international travelers exposed to potentially rabid animals, collecting information on RPEP administration. Travelers who started RPEP before (Group A) and at (Group B) presentation to a GeoSentinel clinic during September 2014–July 2017 were included. We included 920 travelers who started RPEP. About two-thirds of Group A travelers with an indication for rabies immunoglobulin (RIG) did not receive it. Travelers exposed in Indonesia were less likely to receive RIG in the country of exposure (relative risk: 0.30; 95% confidence interval: 0.12–0.73; P = 0.01). Travelers exposed in Thailand [Relative risk (RR) 1.38, 95% Confidence Interval (95% CI): 1.0–1.8; P = 0.02], Sri Lanka (RR 3.99, 95% CI: 3.99–11.9; P = 0.013), and the Philippines (RR 19.95, 95% CI: 2.5–157.2; P = 0.01), were more likely to receive RIG in the country of exposure. Conclusions/Significance: This analysis highlights gaps in early delivery of RIG to travelers and identifies specific countries where travelers may be more or less likely to receive RIG. More detailed country-level information helps inform risk education of international travelers regarding appropriate rabies prevention. [ABSTRACT FROM AUTHOR]

Background: Approximately 59,000 people die from rabies worldwide annually. Haiti is one of the last remaining countries in the Western Hemisphere with endemic canine rabies. Canine-mediated rabies deaths are preventable with post-exposure prophylaxis (PEP): wound treatment, immunoglobulin, and vaccination. In countries where PEP is available, variability in healthcare seeking behaviors and lack of adherence to recommended treatment guidelines could also contribute to these deaths. Yet, few studies have addressed these issues. Methods: We examined animal-bite reporting and assessed adherence to treatment guidelines at nine healthcare facilities in Haiti. We analyzed individual-level, de-identified patient data (demographic characteristics, geographic location, healthcare facility type, vaccine administration, and bite injury information) using descriptive analyses and logistic regression to examine factors associated with receiving PEP. Findings: During the 6 month study period, we found 2.5 times more animal-bite case-patients than reported by the national surveillance system (690 versus 274). Of the 690 animal-bite patients identified, 498 (72%) sought care at six PEP providing facilities. Of the case-patients that sought care, 110 (22%) received at least one rabies vaccine. Of the 110 patients, 60 (55%) received all five doses. Delays were observed for three events: when patients presented to a facility after an animal-bite (3.0 days, range: 0–34 days), when patients received their fourth dose (16.1 days, range: 13–52 days), and when patients received their fifth dose (29 days, range: 26–52). When comparing vaccination status and patient characteristics, we found a significant association for bite location (p < .001), severity rank score (p < .001), geographic location (p < .001), and healthcare facility type (p = .002) with vaccination. Conclusion: High levels of underreporting identified here are of concern since vaccine distribution may, in part, be based on the number of animal-bite cases reported. Given that the Haitian government provides PEP to the population for free and we found animal-bite victims are seeking care in a timely manner─ reducing rabies deaths is an achievable goal. [ABSTRACT FROM AUTHOR]

Background: Estimates of current global rabies mortality range from 26,000 to 59,000 deaths per annum. Although pre-exposure prophylaxis using inactivated rabies virus vaccines (IRVs) is effective, it requires two to three doses and is regarded as being too expensive and impractical for inclusion in routine childhood immunization programmes. Methodology/ Principal findings: Here we report the development of a simian-adenovirus-vectored rabies vaccine intended to enable cost-effective population-wide pre-exposure prophylaxis against rabies. ChAdOx2 RabG uses the chimpanzee adenovirus serotype 68 (AdC68) backbone previously shown to achieve pre-exposure protection against rabies in non-human primates. ChAdOx2 differs from AdC68 in that it contains the human adenovirus serotype 5 (AdHu5) E4 orf6/7 region in place of the AdC68 equivalents, enhancing ease of manufacturing in cell lines which provide AdHu5 E1 proteins in trans. We show that immunogenicity of ChAdOx2 RabG in mice is comparable to that of AdC68 RabG and other adenovirus serotypes expressing rabies virus glycoprotein. High titers of rabies virus neutralizing antibody (VNA) are elicited after a single dose. The relationship between levels of VNA activity and rabies virus glycoprotein monomer-binding antibody differs after immunization with adenovirus-vectored vaccines and IRV vaccines, suggesting routes to further enhancement of the efficacy of the adenovirus-vectored candidates. We also demonstrate that ChAdOx2 RabG can be thermostabilised using a low-cost method suitable for clinical bio-manufacture and ambient-temperature distribution in tropical climates. Finally, we show that a dose-sparing effect can be achieved by formulating ChAdOx2 RabG with a simple chemical adjuvant. This approach could lower the cost of ChAdOx2 RabG and other adenovirus-vectored vaccines. Conclusions/ Significance: ChAdOx2 RabG may prove to be a useful tool to reduce the human rabies death toll. We have secured funding for Good Manufacturing Practice- compliant bio-manufacture and Phase I clinical trial of this candidate. [ABSTRACT FROM AUTHOR]

Dengue virus (DENV) is the causative agent of dengue fever and dengue hemorrhagic shock syndrome. Dengue vaccine development is challenging because of the need to induce protection against four antigenically distinct DENV serotypes. Recent studies indicate that tetravalent DENV vaccines must induce balanced, serotype-specific neutralizing antibodies to achieve durable protective immunity against all 4 serotypes. With the leading live attenuated tetravalent DENV vaccines, it has been difficult to achieve balanced and type-specific responses to each serotype, most likely because of unbalanced replication of vaccine viral strains. Here we evaluate a tetravalent DENV protein subunit vaccine, based on recombinant envelope protein (rE) adsorbed to the surface of poly (lactic-co-glycolic acid) (PLGA) nanoparticles for immunogenicity in mice. In monovalent and tetravalent formulations, we show that particulate rE induced higher neutralizing antibody titers compared to the soluble rE antigen alone. Importantly, we show the trend that tetravalent rE adsorbed to nanoparticles stimulated a more balanced serotype specific antibody response to each DENV serotype compared to soluble antigens. Our results demonstrate that tetravalent DENV subunit vaccines displayed on nanoparticles have the potential to overcome unbalanced immunity observed for leading live-attenuated vaccine candidates. [ABSTRACT FROM AUTHOR]

Background: In India, dengue disease is emerging as the most important vector borne public health problem due to rapid and unplanned urbanization, high human density and week management of the disease. Clinical cases are grossly underreported and not much information is available on prevalence and incidence of the disease. Methodology: A cross sectional, stratified, facility based, multistage cluster sampling was conducted between May 4 and June 27, 2017 in Pune city. A total of 1,434 participants were enrolled. The serum samples were tested for detection of historical dengue IgG antibodies by ELISA using the commercial Panbio Dengue IgG Indirect ELISA kit. Anti-dengue IgG-capture Panbio ELISA was used for detection of high titered antibodies to detect recent secondary infection. We used this data to estimate key transmission parameters like force of infection and basic reproductive number. A subset of 120 indirect ELISA positive samples was also tested for Plaque Reduction Neutralizing Antibodies for determining serotype-specific prevalence. Findings: Overall, 81% participants were infected with dengue virus (DENV) at least once if not more. The positivity was significantly different in different age groups. All the adults above 70 years were positive for DENV antibodies. Over 69% participants were positive for neutralizing antibodies against all 4 serotypes suggesting intense transmission of all DENV serotypes in Pune. Age-specific seroprevalence was consistent with long-term, endemic circulation of DENV. There was an increasing trend with age, from 21.6% among <36 months to 59.4% in age group 10–12 years. We estimate that 8.68% of the susceptible population gets infected by DENV each year resulting into more than 3,00,000 infections and about 47,000 to 59,000 cases per year. This transmission intensity is similar to that reported from other known hyper-endemic settings in Southeast Asia and the Americas but significantly lower than report from Chennai. Conclusions: Our study suggests that Pune city has high disease burden, all 4 serotypes are circulating, significant spatial heterogeneity in seroprevalence and suboptimal immunity in younger age groups. This would allow informed decisions to be made on management of dengue and introduction of upcoming dengue vaccines in the city. [ABSTRACT FROM AUTHOR]

Background: Canine leishmaniasis (CanL) is a zoonotic disease, caused by Leishmania infantum and transmitted by Phlebotomus perniciosus in the Mediterranean basin. Previously, an ELISA based on the P. perniciosus salivary protein SP03B was proposed as a valid tool to screen for canine exposure to sand fly bites across regions endemic for CanL. Although this approach is useful in laboratory settings, a practical tool for immediate application in the field is needed. In this study we propose the rSP03B sero-strip, the first immunochromatographic test (ICT) in the field of vector exposure able to rapidly screen dogs living in endemic areas for the presence of P. perniciosus and to aid in the evaluation of vector control programs. Methodology/Principal findings: The ICT was prepared using the bacterially expressed recombinant protein rSP03B as antigen. For test optimization, pre-immune sera from non-bitten laboratory-bred Beagles were used as negative controls. In order to validate the test, sera from laboratory-bred Beagles experimentally exposed to P. perniciosus bites were used as positive controls. Additionally, all samples were tested by ELISA using whole salivary gland homogenate (SGH) and the rSP03B protein as antigen. An almost perfect degree of agreement was found between the ICT and the SGH-ELISA. Furthermore, the newly proposed rSP03B sero-strip showed a sensitivity of 100% and a specificity of 86.79%. Conclusions/Significance: We developed a simple and rapid ICT based on the P. perniciosus rSP03B salivary protein, able to replace the standard ELISA used in previous studies. Our rSP03B sero-strip showed to be highly sensitive and specific in the detection of antibodies (IgG) against P. perniciosus saliva. In the future, this test can be employed during large-scale epidemiological studies of CanL in the Mediterranean area to evaluate the efficacy of vector control programs. [ABSTRACT FROM AUTHOR]

Background: Chikungunya virus (CHIKV) is the most common alphavirus infecting humans worldwide, causing acute and chronically debilitating arthralgia at a great economic expense. Methodology/Principal findings: To facilitate our study of CHIKV, we generated a mCherry tagged replication-competent chimeric virus, CHIKV 37997-mCherry. Single particle cryoEM demonstrated icosahedral organization of the chimeric virus and the display of mCherry proteins on virus surface. CHIKV 37997-mCherry is attenuated in both IFNαR knockout and wild-type mice. Strong anti-CHIKV and anti-mCherry antibody responses were induced in CHIKV 37997-mCherry infected mice. Conclusions/Significance: Our work suggests that chimeric alphaviruses displaying foreign antigen can serve as vaccines against both aphaviruses and other pathogens and diseases. [ABSTRACT FROM AUTHOR]

Background: To establish correlates of human immunity to the live plague vaccine (LPV), we analyzed parameters of cellular and antibody response to the plasminogen activator Pla of Y. pestis. This outer membrane protease is an essential virulence factor that is steadily expressed by Y. pestis. Methodology/Principal findings: PBMCs and sera were obtained from a cohort of naïve (n = 17) and LPV-vaccinated (n = 34) donors. Anti-Pla antibodies of different classes and IgG subclasses were determined by ELISA and immunoblotting. The analysis of antibody response was complicated with a strong reactivity of Pla with normal human sera. The linear Pla B-cell epitopes were mapped using a library of 15-mer overlapping peptides. Twelve peptides that reacted specifically with sera of vaccinated donors were found together with a major cross-reacting peptide IPNISPDSFTVAAST located at the N-terminus. PBMCs were stimulated with recombinant Pla followed by proliferative analysis and cytokine profiling. The T-cell recall response was pronounced in vaccinees less than a year post-immunization, and became Th17-polarized over time after many rounds of vaccination. Conclusions/Significance: The Pla protein can serve as a biomarker of successful vaccination with LPV. The diagnostic use of Pla will require elimination of cross-reactive parts of the antigen. [ABSTRACT FROM AUTHOR]

Background: This phase III clinical trial compared the immunogenicity and safety of a purified chick-embryo cell rabies vaccine (PCECV) administered according to a shortened post-exposure prophylaxis (PEP) 4-site/1-week intradermal regimen, compared with the currently recommended 2-site/Thai Red Cross (TRC). Methodology/Principal findings: This controlled, open-label, multi-center study (NCT02177032) enrolled healthy individuals ≥1 year of age, randomized into 4 groups to receive intradermal PCECV according to one of the 2 regimens, with or without human rabies immunoglobulin (HRIG) administration at first visit (in adults only). Rabies virus neutralizing antibody (RVNA) concentrations and percentages of participants with RVNA concentrations ≥0.5 IU/mL (considered as adequate concentrations following PEP) were assessed up to day (D) 365 post-first vaccination. Non-inferiority of the 4-site/1-week regimen to the 2-site/TRC regimen was demonstrated if at D49, the lower limit of the 95% confidence interval (CI) for the difference between groups in the percentage of participants with adequate RVNA concentrations was >-5%. Of the 443 participants receiving the 4-site/1-week regimen, 88 adults received HRIG; 442 participants received the 2-site/TRC regimen (88 with HRIG). All participants achieved adequate RVNA concentrations by D14. At D49, the difference in percentage of participants with adequate RVNA concentrations between the 4-site/1-week and the 2-site/TRC groups was -1 (95%CI: -2.4–0.0); thus, non-inferiority was concluded. RVNA geometric mean concentrations were 18 IU/mL in 4-site/1-week groups and 12 IU/mL in 2-site/TRC groups at D14, and subsequently declined in all groups. RVNA concentrations were consistently lower in adults with HRIG administration than in those without. The 2 regimens had similar safety profiles. Of the 15 serious adverse events reported in 4-site/1-week groups and 19 in 2-site/TRC groups, none were vaccination-related. Significance: The data suggest that the 4-site/1-week regimen might be an alternative to current recommendations, with potential benefits in terms of improved cost-efficiency and compliance to vaccination. [ABSTRACT FROM AUTHOR]

Background: Ebola virus (EBOV) caused more than 11,000 deaths during the 2013–2016 epidemic in West Africa without approved vaccines or immunotherapeutics. Despite its high lethality in some individuals, EBOV infection can produce little to no symptoms in others. A better understanding of the immune responses in individuals who experienced minimally symptomatic and asymptomatic infection could aid the development of more effective vaccines and antivirals against EBOV and related filoviruses. Methodology/Principle findings: Between August and November 2017, blood samples were collected from 19 study participants in Lagos, Nigeria, including 3 Ebola virus disease (EVD) survivors, 10 individuals with documented close contact with symptomatic EVD patients, and 6 control healthcare workers for a cross-sectional serosurvey and T cell analysis. The Lagos samples, as well as archived serum collected from healthy individuals living in surrounding areas of the 1976 Democratic Republic of Congo (DRC) epidemic, were tested for EBOV IgG using commercial enzyme-linked immunosorbent assays (ELISAs) and Western blots. We detected antibodies in 3 out of 3 Lagos survivors and identified 2 seropositive individuals not known to have ever been infected. Of the DRC samples tested, we detected antibodies in 9 out of 71 (12.7%). To characterize the T cell responses in the Lagos samples, we developed an anthrax toxin-based enzyme-linked immunospot (ELISPOT) assay. The seropositive asymptomatic individuals had T cell responses against EBOV nucleoprotein, matrix protein, and glycoprotein 1 that were stronger in magnitude compared to the survivors. Conclusion/Significance: Our data provide further evidence of EBOV exposure in individuals without EVD-like illness and, for the first time, demonstrate that these individuals have T cell responses that are stronger in magnitude compared to severe cases. These findings suggest that T cell immunity may protect against severe EVD, which has important implications for vaccine development. [ABSTRACT FROM AUTHOR]

In sub-Saharan Africa, invasive nontyphoidal Salmonella (iNTS) infections with serovars S. Enteritidis, S. Typhimurium and I 4,[],12:i:- are widespread in children < 5 years old. Development of an efficacious vaccine would provide an important public health tool to prevent iNTS disease in this population. Glycoconjugates of S. Enteritidis core and O-polysaccharide (COPS) coupled to the homologous serovar phase 1 flagellin protein (FliC) were previously shown to be immunogenic and protected adult mice against death following challenge with a virulent Malian S. Enteritidis blood isolate. This study extends these observations to immunization of mice in early life and also assesses protection with partial and full regimens. Anti-COPS and anti-FliC serum IgG titers were assessed in infant and adult mice after immunization with 1, 2 or 3 doses of S. Enteritidis COPS:FliC alone or co-formulated with aluminum hydroxide or monophosphoryl lipid A (MPL) adjuvants. S. Enteritidis COPS:FliC was immunogenic in both age groups, although the immune responses were quantitatively lower in infants. Kinetics of antibody production were similar for the native and adjuvanted formulations after three doses; conjugates formulated with MPL elicited significantly increased anti-COPS IgG titers in adult but not infant mice. Nevertheless, robust protection against S. Enteritidis challenge was seen for all three formulations when three doses were given either during infancy or as adults. We further found that significant protection could be achieved with two COPS:FliC doses, despite elicitation of modest serum anti-COPS IgG antibody titers. These findings guide potential immunization strategies that may be translated to develop a human pediatric iNTS vaccine for sub-Saharan Africa. [ABSTRACT FROM AUTHOR]

Rift Valley fever virus (RVFV) is an important mosquito-borne veterinary and human pathogen that has caused large outbreaks of severe disease throughout Africa and the Arabian Peninsula. Currently, no licensed vaccine or therapeutics exists to treat this potentially deadly disease. The explosive nature of RVFV outbreaks and the severe consequences of its accidental or intentional introduction into RVFV-free areas provide the impetus for the development of novel vaccine candidates for use in both livestock and humans. Rationally designed vaccine candidates using reverse genetics have been used to develop deletion mutants of two known RVFV virulence factors, the NSs and NSm genes. These recombinant viruses were demonstrated to be protective and immunogenic in rats, mice, and sheep, without producing clinical illness in these animals. Here, we expand upon those findings and evaluate the single deletion mutant (ΔNSs rRVFV) and double deletion mutant (ΔNSs-ΔNSm rRVFV) vaccine candidates in the common marmoset (Callithrix jacchus), a non-human primate (NHP) model resembling severe human RVF disease. We demonstrate that both the ΔNSs and ΔNSs-ΔNSm rRVFV vaccine candidates were found to be safe and immunogenic in the current study. The vaccinated animals received a single dose of vaccine that led to the development of a robust antibody response. No vaccine-induced adverse reactions, signs of clinical illness or infectious virus were detected in the vaccinated marmosets. All vaccinated animals that were subsequently challenged with RVFV were protected against viremia and liver disease. In summary, our results provide the basis for further development of the ΔNSs and ΔNSs-ΔNSm rRVFV as safe and effective human RVFV vaccines for this significant public health threat. [ABSTRACT FROM AUTHOR]

Rift Valley fever virus is an arbovirus that affects both livestock and humans throughout Africa and in the Middle East. Despite its endemicity throughout Africa, it is a rare event to identify an infected individual during the acute phase of the disease and an even rarer event to collect serial blood samples from the affected patient. Severely affected patients can present with hemorrhagic manifestations of disease. In this study we identified three Ugandan men with RVFV disease that was accompanied by hemorrhagic manifestations. Serial blood samples from these men were analyzed for a series of biomarkers specific for various aspects of human pathophysiology including inflammation, endothelial function and coagulopathy. There were significant differences between biomarker levels in controls and cases both early during the illness and after clearance of viremia. Positive correlation of viral load with markers of inflammation (IP-10, CRP, Eotaxin, MCP-2 and Granzyme B), markers of fibrinolysis (tPA and D-dimer), and markers of endothelial function (sICAM-1) were all noted. However, and perhaps most interesting given the fact that these individuals exhibited hemorrhagic manifestations of disease, was the finding of a negative correlation between viral load and P-selectin, ADAMTS13, and fibrinogen all of which are associated with coagulation pathways occurring on the endothelial surface. [ABSTRACT FROM AUTHOR]

Mosquitoes are incriminated as vectors for many crippling diseases, including malaria, West Nile fever, Dengue fever, and other neglected tropical diseases (NTDs). microRNAs (miRNAs) can interact with multiple target genes to elicit biological functions in the mosquitoes. However, characterization and function of individual miRNAs and their potential targets have not been fully determined to date. We conducted a systematic review of published literature following PRISMA guidelines. We summarize the information about miRNAs in mosquitoes to better understand their metabolism, development, and responses to microorganisms. Depending on the study, we found that miRNAs were dysregulated in a species-, sex-, stage-, and tissue/organ-specific manner. Aberrant miRNA expressions were observed in development, metabolism, host-pathogen interactions, and insecticide resistance. Of note, many miRNAs were down-regulated upon pathogen infection. The experimental studies have expanded the identification of miRNA target from the 3′ untranslated regions (UTRs) of mRNAs of mosquitoes to the 5′ UTRs of mRNAs of the virus. In addition, we discuss current trends in mosquito miRNA research and offer suggestions for future studies. [ABSTRACT FROM AUTHOR]

A reliable and effective human challenge model is needed to help down-select the most promising ETEC vaccines currently under development. Such a model would need to reliably induce diarrhea in a high proportion of volunteers using the lowest possible inoculum to maximize safety and sensitivity. Previously we validated a challenge model that utilized a dose of 2x107 CFU of ETEC strain H10407 (LT+, ST+, CFA/I+ and O78+) to induce attack rates for moderate to severe diarrhea (MSD) of ~60–70%. Here we detail efforts to further refine the model in an attempt to determine if a lower challenge dose of H10407 can be used. Thirty subjects were randomized 1:1 to receive an oral administration of H10407 at doses of 106 or 105 CFU in bicarbonate buffer. After challenge, subjects were monitored for signs and symptoms of enteric illness and stool samples were collected to detect shedding of the challenge strain. Systemic and mucosal immune responses were measured using serum, antibody in lymphocyte supernatant and fecal samples. The attack rate was 13.3% (2/15) and 26.7% (4/15) for MSD in the 105 and 106 groups, respectively. Four MSD cases met criteria for early antibiotic treatment. All subjects but one shed the challenge strain in fecal samples. The frequency and magnitude of anti-LT toxin, CFA/I and LPS O78 immune responses were antigen, dose, severity of diarrhea and shedding levels dependent. Notably, although of lower magnitude, there were considerable immune responses in the subjects with no diarrhea. This may indicate that immune responses to asymptomatic infections of ETEC in children in the endemic countries may contribute to protection. Based on this and our prior studies, we conclude that a dose of 2x107 H10407 remains the lowest practical dose for use in future volunteer studies evaluating candidate vaccines and other preventive or therapeutic ETEC interventions. Trial registration: ClinicalTrials.gov . [ABSTRACT FROM AUTHOR]

Background: Lymphocytic choriomeningitis virus (LCMV) causes a variety of diseases, including asymptomatic infections, meningitis, and congenital infections in the fetus of infected mother. The development of a safe and effective vaccine against LCMV is imperative. This study aims to develop a new candidate vaccine against LCMV using a recombinant replication-incompetent rabies virus (RV) vector. Methodology/Principal findings: In this study, we have generated a recombinant deficient RV expressing the LCMV glycoprotein precursor (GPC) (RVΔP-LCMV/GPC) which is lacking the RV-P gene. RVΔP-LCMV/GPC is able to propagate only in cells expressing the RV-P protein. In contrast, the LCMV-GPC can be expressed in general cells, which do not express RV-P protein. The ability of RVΔP-LCMV/GPC to protect mice from LCMV infection and induce cellular immunity was assessed. Mice inoculated intraperitoneally with RVΔP-LCMV/GPC showed higher survival rates (88.2%) than those inoculated with the parental recombinant RV-P gene-deficient RV (RVΔP) (7.7%) following a LCMV challenge. Neutralizing antibody (NAb) against LCMV was not induced, even in the sera of surviving mice. CD8+ T-cell depletion significantly reduced the survival rates of RVΔP-LCMV/GPC-inoculated mice after the LCMV challenge. These results suggest that CD8+ T cells play a major role in the observed protection against LCMV. In contrast, NAbs against RV were strongly induced in sera of mice inoculated with either RVΔP-LCMV/GPC or RVΔP. In safety tests, suckling mice inoculated intracerebrally with RVΔP-LCMV/GPC showed no symptoms. Conclusions/Significance: These results show RVΔP-LCMV/GPC might be a promising candidate vaccine with dual efficacy, protecting against both RV and LCMV. [ABSTRACT FROM AUTHOR]

Lymphatic filariasis, commonly known as elephantiasis, is a painful and profoundly disfiguring disease. Wuchreria bancrofti (Wb) is responsible for >90% of infections and the remainder are caused by Brugia spp. Mosquitoes of the genera Culex (in urban and semi-urban areas), Anopheles (in rural areas of Africa and elsewhere), and Aedes (in Pacific islands) are the major vectors of W. bancrofti. A preventive chemotherapy called mass drug administration (MDA), including albendazole with ivermectin or diethylcarbamazine citrate (DEC) is used in endemic areas. Vector control strategies such as residual insecticide spraying and long-lasting insecticidal nets are supplemental to the core strategy of MDA to enhance elimination efforts. However, increasing insecticide resistance in mosquitoes and drug resistance in parasite limit the effectiveness of existing interventions, and new measures are needed for mosquito population control and disruption of mosquito-parasite interactions to reduce transmission. Mosquito insulin signaling regulates nutrient metabolism and has been implicated in reduced prevalence and intensity of malaria parasite, Plasmodium falciparum, infection in mosquitoes. Currently no data are available to assess how insulin signaling in mosquitoes affects the development of multi-cellular parasites, such as filarial nematodes. Here, we show that insulin receptor knockdown in blood fed C. quinquefasciatus, the major vector of Wb in India, completely blocks the development of filarial nematode parasite to the infective L3 stage, and results in decreased ecdysteroid production and trypsin activity leading to fewer mosquito eggs. These data indicate that a functional mosquito insulin receptor (IR) is necessary for filarial parasite development and mosquito reproduction. Therefore, insulin signaling may represent a new target for the development of vector control or parasite blocking strategies. [ABSTRACT FROM AUTHOR]

Background: Cholera is an acute voluminous dehydrating diarrheal disease caused by toxigenic strains of Vibrio cholerae O1 and occasionally O139. A growing body of evidence indicates that immune responses targeting the O-specific polysaccharide (OSP) of V. cholerae are involved in mediating protection against cholera. We therefore assessed whether antibody responses against OSP occur after vaccination with live attenuated oral cholera vaccine CVD 103-HgR, and whether such responses correlate with protection against cholera. Methodology: We assessed adult North American volunteers (n = 46) who were vaccinated with 5 × 108 colony-forming units (CFU) of oral cholera vaccine CVD 103-HgR and then orally challenged with approximately 1 × 105 CFU of wild-type V. cholerae O1 El Tor Inaba strain N16961, either 10 or 90 days post-vaccination. Principal findings: Vaccination was associated with induction of significant serum IgM and IgA anti-OSP and vibriocidal antibody responses within 10 days of vaccination. There was significant correlation between anti-OSP and vibriocidal antibody responses. IgM and IgA anti-OSP responses on day 10 following vaccination were associated with lower post-challenge stool volume (r = −0.44, P = 0.002; r = −0.36, P = 0.01; respectively), and none of 27 vaccinees who developed a ≥1.5 fold increase in any antibody isotype targeting OSP on day 10 following vaccination compared to baseline developed moderate or severe cholera following experimental challenge, while 5 of 19 who did not develop such anti-OSP responses did (P = 0.01). Conclusion: Oral vaccination with live attenuated cholera vaccine CVD 103-HgR induces antibodies that target V. cholerae OSP, and these anti-OSP responses correlate with protection against diarrhea following experimental challenge with V. cholerae O1. Trial registration: ClinicalTrials.gov [ABSTRACT FROM AUTHOR]

Background: Chagas disease, also known as American Trypanosomiasis, is a chronic parasitic disease caused by the flagellated protozoan Trypanosoma cruzi that affects about 8 million people around the world where more than 25 million are at risk of contracting the infection. Despite of being endemic on 21 Latin-American countries, Chagas disease has become a global concern due to migratory movements. Unfortunately, available drugs for the treatment have several limitations and they are generally administered during the chronic phase of the infection, when its efficacy is considered controversial. Thus, prophylactic and/or therapeutic vaccines are emerging as interesting control alternatives. In this work, we proposed Trypanosoma cruzi 80 kDa prolyl oligopeptidase (Tc80) as a new antigen for vaccine development against Chagas disease. Methodology/Principal findings: In a murine model, we analyzed the immune response triggered by different immunization protocols based on Tc80 and evaluated their ability to confer protection against a challenge with the parasite. Immunized mice developed Tc80-specific antibodies which were able to carry out different functions such as: enzymatic inhibition, neutralization of parasite infection and complement-mediated lysis of trypomastigotes. Furthermore, vaccinated mice elicited strong cell-mediated immunity. Spleen cells from immunized mice proliferated and secreted Th1 cytokines (IL-2, IFN-γ and TNF-α) upon re-stimulation with rTc80. Moreover, we found Tc80-specific polyfunctional CD4 T cells, and cytotoxic T lymphocyte activity against one Tc80 MHC-I peptide. Immunization protocols conferred protection against a T. cruzi lethal challenge. Immunized groups showed a decreased parasitemia and higher survival rate compared with non-immunized control mice. Moreover, during the chronic phase of the infection, immunized mice presented: lower levels of myopathy-linked enzymes, parasite burden, electrocardiographic disorders and inflammatory cells. Conclusions/Significance: Considering that an early control of parasite burden and tissue damage might contribute to avoid the progression towards symptomatic forms of chronic Chagas disease, the efficacy of Tc80-based vaccines make this molecule a promising immunogen for a mono or multicomponent vaccine against T. cruzi infection. [ABSTRACT FROM AUTHOR]

Mosquito-borne Zika virus (ZIKV) typically causes a mild and self-limiting illness known as Zika fever. Since its recent emergence in 2014 in the American continent, ZIKV infection during pregnancy has been closely associated with a wide range of congenital abnormalities. To date, no vaccines or antivirals are publicly available. We developed Zika virus-like particles (VLPs) and evaluated their immunogenicity and protective efficacy in mouse models. ZIKV VLPs (ZIKVLPs) formulated with alum were injected into 6-8-week-old interferon deficient AG129 mice as well as wild type BALB/c mice. Control mice received PBS/alum. Animals were challenged with 200 PFU (>1000 AG129 LD50s) of ZIKV strain H/PF/2013. All vaccinated mice survived with no morbidity or weight loss while control animals either died at 9 days post challenge (AG129) or had increased viremia (BALB/c). Neutralizing antibodies were observed in all ZIKVLP vaccinated mice. The role of neutralizing antibodies in protecting mice was demonstrated by passive transfer. Our findings demonstrate the protective efficacy of the ZIKVLP vaccine and highlight the important role that neutralizing antibodies play in protection against ZIKV infection. [ABSTRACT FROM AUTHOR]

Background: Vibrio cholerae causes over 2 million cases of cholera and 90,000 deaths each year. Serosurveillance can be a useful tool for estimating the intensity of cholera transmission and prioritizing populations for cholera control interventions. Current methods involving venous blood draws and downstream specimen storage and transport methods pose logistical challenges in most settings where cholera strikes. To overcome these challenges, we developed methods for determining cholera-specific immune responses from dried blood spots (DBS). Methodology/principal findings: As conventional vibriocidal assay methods were unsuitable for DBS eluates from filter paper, we adopted a drop-plate culture method. We show that DBS collected from volunteers in South Sudan, and stored for prolonged periods in field conditions, retained functional vibriocidal antibodies, the titers of which correlated with paired serum titers determined by conventional spectrophotometric methods (r = 0.94, p = 0.00012). We also showed that eluates from DBS Serum Separator cards could be used with conventional spectrophotometric vibriocidal methods, and that they correlated with paired serum at a wide range of titers (r = 0.96, p<0.0001). Similarly, we used ELISA methods to show that V. cholerae O-specific polysaccharide antibody responses from DBS eluates correlated with results from paired serum for IgG (r = 0.85, p = 0.00006), IgM (r = 0.79, p = 0.00049) and IgA (r = 0.73, p = 0.0019), highlighting its potential for use in determination of isotype-specific responses. Storage of DBS cards at a range of temperatures did not change antibody responses. Conclusion: In conclusion, we have developed and demonstrated a proof-of-concept for assays utilizing DBS for assessing cholera-specific immune responses. [ABSTRACT FROM AUTHOR]

Background: Dengue is one of the fastest spreading vector-borne diseases, caused by four antigenically distinct dengue viruses (DENVs). Antibodies against DENVs are responsible for both protection as well as pathogenesis. A vaccine that is safe for and efficacious in all people irrespective of their age and domicile is still an unmet need. It is becoming increasingly apparent that vaccine design must eliminate epitopes implicated in the induction of infection-enhancing antibodies. Methodology/principal findings: We report a Pichia pastoris-expressed dengue immunogen, DSV4, based on DENV envelope protein domain III (EDIII), which contains well-characterized serotype-specific and cross-reactive epitopes. In natural infection, <10% of the total neutralizing antibody response is EDIII-directed. Yet, this is a functionally relevant domain which interacts with the host cell surface receptor. DSV4 was designed by in-frame fusion of EDIII of all four DENV serotypes and hepatitis B surface (S) antigen and co-expressed with unfused S antigen to form mosaic virus-like particles (VLPs). These VLPs displayed EDIIIs of all four DENV serotypes based on probing with a battery of serotype-specific anti-EDIII monoclonal antibodies. The DSV4 VLPs were highly immunogenic, inducing potent and durable neutralizing antibodies against all four DENV serotypes encompassing multiple genotypes, in mice and macaques. DSV4-induced murine antibodies suppressed viremia in AG129 mice and conferred protection against lethal DENV-4 virus challenge. Further, neither murine nor macaque anti-DSV4 antibodies promoted mortality or inflammatory cytokine production when passively transferred and tested in an in vivo dengue disease enhancement model of AG129 mice. Conclusions/significance: Directing the immune response to a non-immunodominant but functionally relevant serotype-specific dengue epitope of the four DENV serotypes, displayed on a VLP platform, can help minimize the risk of inducing disease-enhancing antibodies while eliciting effective tetravalent seroconversion. DSV4 has a significant potential to emerge as a safe, efficacious and inexpensive subunit dengue vaccine candidate. [ABSTRACT FROM AUTHOR]

Crimean-Congo haemorrhagic fever virus (CCHFV) is a member of the Orthonairovirus genus of the Nairoviridae family and is associated with haemorrhagic fever in humans. Although T lymphocyte responses are known to play a role in protection from and clearance of viral infections, specific T cell epitopes have yet to be identified for CCHFV following infection. A panel of overlapping peptides covering the CCHFV nucleoprotein and the structural glycoproteins, GN and GC, were screened by ELISpot assay to detect interferon gamma (IFN-γ) production in vitro by peripheral blood mononuclear cells from eleven survivors with previous laboratory confirmed CCHFV infection. Reactive peptides were located predominantly on the nucleoprotein, with only one survivor reacting to two peptides from the glycoprotein GC. No single epitope was immunodominant, however all but one survivor showed reactivity to at least one T cell epitope. The responses were present at high frequency and detectable several years after the acute infection despite the absence of continued antigenic stimulation. T cell depletion studies confirmed that IFN-γ production as detected using the ELISpot assay was mediated chiefly by CD8+ T cells. This is the first description of CD8+ T cell epitopic regions for CCHFV and provides confirmation of long-lived T cell responses in survivors of CCHFV infection. [ABSTRACT FROM AUTHOR]

Rabies is a neglected zoonotic disease that is preventable in humans by appropriate post-exposure prophylaxis (PEP). However, current PEP relies on polyclonal immune globulin products purified from pooled human (HRIG) or equine (ERIG) plasma that are either in chronic shortage or in association with safety concerns. Here, we present the development of an antibody cocktail, SYN023, made of two novel monoclonal antibodies (MAb) CTB011 and CTB012 that could serve as safer and more cost-effective alternatives to the current RIG products. Both CTB011 and CTB012 are humanized MAbs that bind to non-overlapping epitopes on the rabies virus (RABV) glycoprotein (G) with sub-nanomolar affinities. Sequence analysis revealed that many of the critical residues in binding are highly conserved across different species of lyssaviruses. When combined at a 1:1 ratio, CTB011/CTB012 exhibited neutralization capabilities equivalent or superior to HRIG against 10 North American street RABV isolates in vitro and 15 prevalent Chinese RABV strains in animal models. Finally, SYN023, at a dosage of 0.03 mg/kg, was able to offer the same degree of protection as standard HRIG administration (20 IU/kg) in Syrian hamsters challenged with a highly virulent bat (Tadarida brasiliensis) RABV variant. Taken together, the high-potency and broad-spectrum neutralization demonstrated by SYN023 make it an effective candidate for human rabies PEP consideration. [ABSTRACT FROM AUTHOR]

Although effective rabies virus vaccines have been existing for decades, each year, rabies virus infections still cause around 50.000 fatalities worldwide. Most of these cases occur in developing countries, where these vaccines are not available. The reasons for this are the prohibitive high costs of cell culture or egg grown rabies virus vaccines and the lack of a functional cold chain in many regions in which rabies virus is endemic. Here, we describe the excellent temperature resistance of a non-replicating mRNA based rabies virus vaccine encoding the rabies virus glycoprotein (RABV-G). Prolonged storage of the vaccine from -80°C to up to +70°C for several months did not impact the protective capacity of the mRNA vaccine. Efficacy after storage was demonstrated by the induction of rabies specific virus neutralizing antibodies and protection in mice against lethal rabies infection. Moreover, storing the vaccine at oscillating temperatures between +4° and +56°C for 20 cycles in order to simulate interruptions of the cold chain during vaccine transport, did not affect the vaccine’s immunogenicity and protective characteristics, indicating that maintenance of a cold chain is not essential for this vaccine. [ABSTRACT FROM AUTHOR]

The notion that previous infection by Leishmania spp. in endemic areas leads to robust anti-Leishmania immunity, supports vaccination as a potentially effective approach to prevent disease development. Nevertheless, to date there is no vaccine available for human leishmaniasis. We optimized and assessed in vivo the safety and immunogenicity of an innovative vaccine candidate against human visceral leishmaniasis (VL), consisting of Virus-Like Particles (VLP) loaded with three different recombinant proteins (LJL143 from Lutzomyia longipalpis saliva as the vector-derived (VD) component, and KMP11 and LeishF3+, as parasite-derived (PD) antigens) and adjuvanted with GLA-SE, a TLR4 agonist. No apparent adverse reactions were observed during the experimental time-frame, which together with the normal hematological parameters detected seems to point to the safety of the formulation. Furthermore, measurements of antigen-specific cellular and humoral responses, generally higher in immunized versus control groups, confirmed the immunogenicity of the vaccine formulation. Interestingly, the immune responses against the VD protein were reproducibly more robust than those elicited against leishmanial antigens, and were apparently not caused by immunodominance of the VD antigen. Remarkably, priming with the VD protein alone and boosting with the complete vaccine candidate contributed towards an increase of the immune responses to the PD antigens, assessed in the form of increased ex vivo CD4+ and CD8+ T cell proliferation against both the PD antigens and total Leishmania antigen (TLA). Overall, our immunogenicity data indicate that this innovative vaccine formulation represents a promising anti-Leishmania vaccine whose efficacy deserves to be tested in the context of the “natural infection”. [ABSTRACT FROM AUTHOR]

Rabies is an ancient neglected tropical disease that causes tens of thousands of human deaths and millions of cattle deaths annually. In order to develop a new vaccine for potential use in bats, a reservoir of rabies infection for humans and animals alike, an in silico antigen designer tool was used to create a mosaic glycoprotein (MoG) gene using available sequences from the rabies Phylogroup I glycoprotein. This sequence, which represents strains more likely to occur in bats, was cloned into raccoonpox virus (RCN) and the efficacy of this novel RCN-MoG vaccine was compared to RCN-G that expresses the glycoprotein gene from CVS-11 rabies or luciferase (RCN-luc, negative control) in mice and big brown bats (Eptesicus fuscus). Mice vaccinated and boosted intradermally with 1 x 107 plaque forming units (PFU) of each RCN-rabies vaccine construct developed neutralizing antibodies and survived at significantly higher rates than controls. No significant difference in antibody titers or survival was noted between rabies-vaccinated groups. Bats were vaccinated either oronasally (RCN-G, RCN-MoG) with 5x107 PFU or by topical application in glycerin jelly (RCN-MoG, dose 2x108 PFU), boosted (same dose and route) at 46 days post vaccination (dpv), and then challenged with wild-type big brown variant RABV at 65 dpv. Prior to challenge, 90% of RCN-G and 75% of RCN-MoG oronasally vaccinated bats had detectable levels of serum rabies neutralizing antibodies. Bats from the RCN-luc and topically vaccinated RCN-MoG groups did not have measurable antibody responses. The RCN-rabies constructs were highly protective and not significantly different from each other. RCN-MoG provided 100% protection (n = 9) when delivered oronasally and 83% protection (n = 6) when delivered topically; protection provided by the RCN-G construct was 70% (n = 10). All rabies-vaccinated bats survived at a significantly (P ≤ 0.02) higher rate than control bats (12%; n = 8). We have demonstrated the efficacy of a novel, in silico designed rabies MoG antigen that conferred protection from rabies challenge in mice and big brown bats in laboratory studies. With further development, topical or oronasal administration of the RCN-MoG vaccine could potentially mitigate rabies in wild bat populations, reducing spillover of this deadly disease into humans, domestic mammals, and other wildlife. [ABSTRACT FROM AUTHOR]

Paracoccidioidomycosis (PCM) is an infectious disease endemic to South America, caused by the thermally dimorphic fungi Paracoccidioides. Currently, there is no effective human vaccine that can be used in prophylactic or therapeutic regimes. We tested the hypothesis that the immunogenicity of the immunodominant CD4+ T-cell epitope (P10) of Paracoccidioides brasiliensis gp43 antigen might be significantly enhanced by using a hepatitis B virus-derived particle (VLP) as an antigen carrier. This chimera was administered to mice as a (His)6-purified protein (rPbT) or a replication-deficient human type 5 adenoviral vector (rAdPbT) in an immunoprophylaxis assay. The highly virulent Pb18 yeast strain was used to challenge our vaccine candidates. Fungal challenge evoked robust P10-specific memory CD4+ T cells secreting protective Th-1 cytokines in most groups of immunized mice. Furthermore, the highest level of fungal burden control was achieved when rAdPbT was inoculated in a homologous prime-boost regimen, with 10-fold less CFU recovering than in non-vaccinated mice. Systemic Pb18 spreading was only prevented when rAdPbT was previously inoculated. In summary, we present here VLP/P10 formulations as vaccine candidates against PCM, some of which have demonstrated for the first time their ability to prevent progression of this pernicious fungal disease, which represents a significant social burden in developing countries. [ABSTRACT FROM AUTHOR]

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne virus capable of causing a severe hemorrhagic fever disease in humans. There are currently no licensed vaccines to prevent CCHFV-associated disease. We developed a DNA vaccine expressing the M-segment glycoprotein precursor gene of CCHFV and assessed its immunogenicity and protective efficacy in two lethal mouse models of disease: type I interferon receptor knockout (IFNAR-/-) mice; and a novel transiently immune suppressed (IS) mouse model. Vaccination of mice by muscle electroporation of the M-segment DNA vaccine elicited strong antigen-specific humoral immune responses with neutralizing titers after three vaccinations in both IFNAR-/- and IS mouse models. To compare the protective efficacy of the vaccine in the two models, groups of vaccinated mice (7–10 per group) were intraperitoneally (IP) challenged with a lethal dose of CCHFV strain IbAr 10200. Weight loss was markedly reduced in CCHFV DNA-vaccinated mice as compared to controls. Furthermore, whereas all vector-control vaccinated mice succumbed to disease by day 5, the DNA vaccine protected >60% of the animals from lethal disease. Mice from both models developed comparable levels of antibodies, but the IS mice had a more balanced Th1/Th2 response to vaccination. There were no statistical differences in the protective efficacies of the vaccine in the two models. Our results provide the first comparison of these two mouse models for assessing a vaccine against CCHFV and offer supportive data indicating that a DNA vaccine expressing the glycoprotein genes of CCHFV elicits protective immunity against CCHFV. [ABSTRACT FROM AUTHOR]

The article discusses the authors' views on dengue diagnostics and their application for dengue surveillance in countries where the CYD-TDV vaccine has been implemented. The authors discuss the limitations of dengue diagnostics, techniques for flavivirus antibody detection, and an algorithm of dengue diagnostic testing after CYD-TDV dengue vaccine implementation in countries with a high burden of dengue.

In mid-2015, Salvador, Brazil, reported an outbreak of Guillain-Barré syndrome (GBS), coinciding with the introduction and spread of Zika virus (ZIKV). We found that GBS incidence during April–July 2015 among those ≥12 years of age was 5.6 cases/100,000 population/year and increased markedly with increasing age to 14.7 among those ≥60 years of age. We conducted interviews with 41 case-patients and 85 neighborhood controls and found no differences in demographics or exposures prior to GBS-symptom onset. A higher proportion of case-patients (83%) compared to controls (21%) reported an antecedent illness (OR 18.1, CI 6.9–47.5), most commonly characterized by rash, headache, fever, and myalgias, within a median of 8 days prior to GBS onset. Our investigation confirmed an outbreak of GBS, particularly in older adults, that was strongly associated with Zika-like illness and geo-temporally associated with ZIKV transmission, suggesting that ZIKV may result in severe neurologic complications. [ABSTRACT FROM AUTHOR]

Background: Pathogenesis of severe fever with thrombocytopenia syndrome (SFTS) has not been well described yet. Recent studies indicate that SFTSV could replicate in endothelial cells. Here we performed a case-control study to determine whether endothelial activation/dysfunction occurred in SFTSV infection and to identify the biomarkers reflecting endothelial dysfunction. Methodology/Principal findings: In a case-control study of 134 SFTS patients and 68 healthy controls, serum levels of plasminogen activator inhibitor 1, tissue plasminogen activator, P-selectin, platelet endothelial cell adhesion molecular, CD40 ligand, E-selectin, vascular endothelial growth factor A, serum amyloid antigen 1 (SAA-1) and vascular cell adhesion molecular 1 were significantly enhanced in the patients than the controls (all P<0.05), indicating the occurrence of endothelial activation/dysfunction in SFTS. The intercellular adhesion molecular 1 (ICAM-1) and SAA-1 at the convalescent phase were also significantly associated with severe patients, after adjusting for the potential confounders. The odds ratio was estimated to be 3.364 (95% CI 1.074–10.534) for ICAM-1, and 1.881 (95% CI 1.166–3.034) for SAA-1, respectively. Cutoff value of 1.1×107 pg/mL SAA-1 or 1.2×106 pg/mL ICAM-1 were found to have moderate power of predicting fatal cases. Conclusions: The endothelial dysfunction may be one of the pathogenic mechanism of SFTS. The serum levels of ICAM-1 and SAA-1 might be used to predict adverse outcome. [ABSTRACT FROM AUTHOR]

Ensuring the adequacy of response to rabies vaccination in dogs is important, particularly in the context of pet travel. Few studies have examined the factors associated with dogs’ failure to achieve an adequate antibody titer after vaccination (0.5 IU/ml). This study evaluated rabies antibody titers in dogs after primary vaccination. Dogs under one year of age whose serum was submitted to a reference laboratory for routine diagnostics, and which had no prior documented history of vaccination were enrolled (n = 8,011). Geometric mean titers (GMT) were calculated and univariate analysis was performed to assess factors associated with failure to achieve 0.5 IU/mL. Dogs vaccinated at >16 weeks of age had a significantly higher GMT compared to dogs vaccinated at a younger age (1.64 IU/ml, 1.57–1.72, ANOVA p < 0.01). There was no statistical difference in GMT between dogs vaccinated <12 weeks and dogs vaccinated 12–16 weeks (1.22 IU/ml and 1.21 IU/ml). The majority of dogs failed to reach an adequate titer within the first 3 days of primary vaccination; failure rates were also high if the interval from vaccination to titer check was greater than 90 days. Over 90% of dogs that failed primary vaccination were able to achieve adequate titers after booster vaccination. The ideal timing for blood draw is 8–30 days after primary vaccination. In the event of a failure, most dogs will achieve an adequate serologic response upon a repeat titer (in the absence of booster vaccination). Booster vaccination after failure provided the highest probability of an acceptable titer. [ABSTRACT FROM AUTHOR]

Few live attenuated vaccines protect against multiple serotypes of bacterial pathogen because host serotype-specific immune responses are limited to the serotype present in the vaccine strain. Here, immunization with a mutant of Shigella flexneri 2a protected guinea pigs against subsequent infection by S. dysenteriae type 1 and S. sonnei strains. This deletion mutant lacked the RNA-binding protein Hfq leading to increased expression of the type III secretion system via loss of regulation, resulting in attenuation of cell viability through repression of stress response sigma factors. Such increased antigen production and simultaneous attenuation were expected to elicit protective immunity against Shigella strains of heterologous serotypes. Thus, the vaccine potential of this mutant was tested in two guinea pig models of shigellosis. Animals vaccinated in the left eye showed fewer symptoms upon subsequent challenge via the right eye, and even survived subsequent intestinal challenge. In addition, oral vaccination effectively induced production of immunoglobulins without severe side effects, again protecting all animals against subsequent intestinal challenge with S. dysenteriae type 1 or S. sonnei strains. Antibodies against common virulence proteins and the O-antigen of S. flexneri 2a were detected by immunofluorescence microscopy. Reaction of antibodies with various strains, including enteroinvasive Escherichia coli, suggested that common virulence proteins induced protective immunity against a range of serotypes. Therefore, vaccination is expected to cover not only the most prevalent serotypes of S. sonnei and S. flexneri 2a, but also various Shigella strains, including S. dysenteriae type 1, which produces Shiga toxin. [ABSTRACT FROM AUTHOR]