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BACKGROUNDDisease due to dengue viruses is a growing global health threat, causing 100-400 million cases annually. An ideal dengue vaccine should demonstrate durable protection against all 4 serotypes in phase III efficacy trials, however the lack of circulating serotypes may lead to incomplete efficacy data. Controlled human infection models help downselect vaccine candidates and supply critical data to supplement efficacy trials. We evaluated the efficacy of a leading live-attenuated tetravalent dengue vaccine candidate, TV005, against infection with a newly established dengue serotype 3 or an established serotype 2 challenge virus.METHODSTwo randomized, controlled clinical trials were performed. In study 1, a total of 42 participants received TV005 or placebo (n = 21 each), and 6 months later, all were challenged with dengue 2 virus (rDEN2Δ30) at a dose of 103 PFU. In study 2, a total of 23 participants received TV005 and 20 received placebo, and 6 months later, all were challenged with 104 PFU dengue 3 virus (rDEN3Δ30). The study participants were closely monitored for safety, viremia, and immunologic responses. Infection, measured by post-challenge viremia, and the occurrence of rash and neutropenia were the primary endpoints. Secondary endpoints included safety, immunologic, and virologic profiles following vaccination with TV005 and subsequent challenge with the rDEN2Δ30 or rDEN3Δ30 strain.RESULTSTV005 was well tolerated and protected all vaccinated volunteers from viremia with DENV2 or DENV3 (none infected in either group). Placebo recipients had post-challenge viremia (100% in study 1, 85% in study 2), and all experienced rash following challenge with either serotype.CONCLUSIONSTV005 is a leading tetravalent dengue vaccine candidate that fully protected against infection with DENV2 and DENV3 in an established controlled human infection model.TRIAL REGISTRATIONClinicalTrials.gov NCT02317900 and NCT02873260.FUNDINGIntramural Research Program, NIH (contract HHSN272200900010C).

Background: Morbidity and mortality from dengue virus (DENV) is rapidly growing in the large populations of south Asia. Few formal evaluations of candidate dengue vaccine candidates have been undertaken in India, Pakistan, or Bangladesh. Tetravalent vaccines must be tested for safety and immunogenicity in all age groups and in those previously exposed and naive to DENV infections. TV005 is a live, attenuated tetravalent dengue vaccine. We evaluated the safety and immunogenicity of a single dose of TV005 across age groups in dengue-endemic Bangladesh., Methods: We performed a randomised, placebo-controlled age de-escalating clinical trial of TV005 at a single clinical site in dengue-endemic Dhaka, Bangladesh, following a technology transfer from the USA. Healthy (as determined by history, clinical examination, and safety laboratory test results) volunteers aged 1-50 years were randomly assigned 3:1 (stratified by four age groups) to receive a single dose of TV005 vaccine or placebo. Participants were followed up for 3 years. The study was double blind and was unmasked at day 180; outcome assessors, clinic staff, and volunteers remained blind throughout. Primary outcomes were safety, evaluated per-protocol as proportion of volunteers with solicited related adverse events of any severity through 28 days post dosing, and post-vaccination seropositivity by day 180 using serotype-specific neutralising antibodies (PRNT 50 ≥10). Secondary outcomes included viremia, impact of past dengue exposure, and durability of antibody responses. This study is registered with Clinicaltrials.gov, NCT02678455, and is complete., Findings: Between March 13, 2016, and Feb 14, 2017, 192 volunteers were enrolled into four age groups (adults [18-50 years; 20 male and 28 female], adolescents [11-17 years; 27 male and 21 female], children [5-10 years; 15 male and 33 female], and young children [1-4 years; 29 male and 19 female]) with 48 participant per group. All participants were Bangladeshi. Vaccination was well tolerated and most adverse events were mild. Rash was the most common vaccine-associated solicited adverse event, in 37 (26%) of 144 vaccine recipients versus six (12%) of 48 placebo recipients; followed by fever in seven (5% of 144) and arthralgias in seven (6% of 108), which were only observed in vaccine recipients. Post-vaccine, volunteers of all ages (n=142) were seropositive to most serotypes with 118 (83%) seropositive to DENV 1, 141 (99%) to DENV 2, 137 (96%) to DENV 3, and 124 (87%) to DENV 4, overall by day 180. Post-vaccination, viraemia was not consistently found and antibody titres were higher (10-15-fold for DENV 1-3 and 1·6-fold for DENV 4) in individuals with past dengue exposure compared with the dengue-naive participants (DENV 1 mean 480 [SD 4·0] vs 32 [2·4], DENV 2 1042 [3·2] vs 105 [3·1], DENV 3 1406 [2·8] vs 129 [4·7], and DENV 4 105 [3·3] vs 65 [3·1], respectively). Antibody titres to all serotypes remained stable in most adults (63-86%) after 3 years of follow-up. However, as expected for individuals without past exposure to dengue, titres for DENV 1, 3, and 4 waned by 3 years in the youngest (1-4 year old) cohort (69% seropositive for DENV 2 and 22-28% seropositive for DENV 1, 3, and 4)., Interpretation: With 3 years of follow-up, the single-dose tetravalent dengue vaccine, TV005, was well tolerated and immunogenic for all four serotypes in young children to adults, including individuals with no previous dengue exposure., Funding: National Institutes of Health-National Institute of Allergy and Infectious Diseases Intramural Research Program and Johns Hopkins University., Translation: For the Bangla translation of the abstract see Supplementary Materials section., Competing Interests: Declaration of interests M-CRW, KKP, MC, DMD, DMB, SAD, FN, and BDK are employed by the University of Vermont Larner College of Medicine (UVM), Burlington, VT, USA, which was the recipient of research funding from the National Institutes of Health (NIH) and Johns Hopkins University for this work. SSW is employed by the NIH, which partially funded this work. APD is employed by Johns Hopkins University, which receives funding from the NIH for dengue research. MSA, MA, SA, KG, FQ, and RH are employed by the icddr, b which received funding from UVM for the conduct of this research., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

About 20-25% of dengue virus (DENV) infections become symptomatic ranging from self-limiting fever to shock. Immune gene expression changes during progression to severe dengue have been documented in hospitalized patients; however, baseline or kinetic information is difficult to standardize in natural infection. Here we profile the host immunotranscriptome response in humans before, during, and after infection with a partially attenuated rDEN2Δ30 challenge virus (ClinicalTrials.gov NCT02021968). Inflammatory genes including type I interferon and viral restriction pathways are induced during DENV2 viremia and return to baseline after viral clearance, while others including myeloid, migratory, humoral, and growth factor immune regulation factors pathways are found at non-baseline levels post-viremia. Furthermore, pre-infection baseline gene expression is useful to predict rDEN2Δ30-induced immune responses and the development of rash. Our results suggest a distinct immunological profile for mild rDEN2Δ30 infection and offer new potential biomarkers for characterizing primary DENV infection.

The four-dengue virus (DENV) serotypes infect several hundred million people annually. For the greatest safety and efficacy, tetravalent DENV vaccines are designed to stimulate balanced protective immunity to all four serotypes. However, this has been difficult to achieve. Clinical trials with a leading vaccine demonstrated that unbalanced replication and immunodominance of one vaccine component over others can lead to low efficacy and vaccine enhanced severe disease. The Laboratory of Infectious Diseases at the National Institutes of Health has developed a live attenuated tetravalent DENV vaccine (TV003), which is currently being tested in phase 3 clinical trials. Here we report, our study to determine if TV003 stimulate balanced and serotype-specific (TS) neutralizing antibody (nAb) responses to each serotype. Serum samples from twenty-one dengue-naive individuals participated under study protocol CIR287 (ClinicalTrials.gov NCT02021968) are analyzed 6 months after vaccination. Most subjects (76%) develop TS nAbs to 3 or 4 DENV serotypes, indicating immunity is induced by each vaccine component. Vaccine-induced TS nAbs map to epitopes known to be targets of nAbs in people infected with wild type DENVs. Following challenge with a partially attenuated strain of DENV2, all 21 subjects are protected from the efficacy endpoints. However, some vaccinated individuals develop post challenge nAb boost, while others mount post-challenge antibody responses that are consistent with sterilizing immunity. TV003 vaccine induced DENV2 TS nAbs are associated with sterilizing immunity. Our results indicate that nAbs to TS epitopes on each serotype may be a better correlate than total levels of nAbs currently used for guiding DENV vaccine development.

Competing Interests: Competing interests: None declared.

The tetravalent live attenuated dengue vaccine candidate TV003 induces neutralizing antibodies against all four dengue virus serotypes (DENV1-DENV4) and protects against experimental challenge with DENV2 in humans. Here, we track vaccine viremia and B and T cell responses to this vaccination/challenge model to understand how vaccine viremia links adaptive immunity and development of protective antibody responses. TV003 viremia triggers an acute plasmablast response that, in combination with DENV-specific CD4 + T cells, correlates with serum neutralizing antibodies. TV003 vaccinees develop DENV2-reactive memory B cells, including serotype-specific and multivalent specificities in line with the composition of serum antibodies. There is no post-challenge plasmablast response in vaccinees, although stronger and earlier post-TV003 plasmablast responses associate with sterile humoral protection from DENV2 challenge. TV003 vaccine triggers plasmablasts and memory B cells, which, with support from CD4 + T cells, functionally link early vaccine viremia and the serum antibody responses., Competing Interests: The authors declare no competing interests., (© 2020 The Author(s).)

Objectives: There is an incomplete understanding of the host humoral immune response to severe acute respiratory syndrome (SARS)-coronavirus (CoV)-2, which underlies COVID-19, during acute infection. Host factors such as age and sex as well as the kinetics and functionality of antibody responses are important factors to consider as vaccine development proceeds. The receptor-binding domain of the CoV spike (RBD-S) protein mediates host cell binding and infection and is a major target for vaccine design to elicit neutralising antibodies., Methods: We assessed serum anti-SARS-CoV-2 RBD-S IgG, IgM and IgA antibodies by a two-step ELISA and neutralising antibodies in a cross-sectional study of hospitalised COVID-19 patients of varying disease severities. Anti-RBD-S IgG levels were also determined in asymptomatic seropositives., Results: We found equivalent levels of anti-RBD-S antibodies in male and female patients and no age-related deficiencies even out to 93 years of age. The anti-RBD-S response was evident as little as 6 days after onset of symptoms and for at least 5 weeks after symptom onset. Anti-RBD-S IgG, IgM and IgA responses were simultaneously induced within 10 days after onset, with anti-RBD-S IgG sustained over a 5-week period. Anti-RBD-S antibodies strongly correlated with neutralising activity. Lastly, anti-RBD-S IgG responses were higher in symptomatic COVID-19 patients during acute infection compared with asymptomatic seropositive donors., Conclusion: Our results suggest that anti-RBD-S IgG reflect functional immune responses to SARS-CoV-2, but do not completely explain age- and sex-related disparities in COVID-19 fatalities., Competing Interests: The authors declare no conflict of interest., (© 2020 The Authors. Clinical & Translational Immunology published by John Wiley & Sons Australia, Ltd on behalf of Australian and New Zealand Society for Immunology, Inc.)

New dengue vaccines are needed to prevent this globally expanding vector-borne disease. The V180 vaccine candidate consists of four recombinant, soluble, dengue virus envelope glycoproteins and has been previously evaluated in two clinical trials for safety and immunogenicity in Flavivirus -naive participants (NCT01477580 and NCT0093642). Here, we report on a randomized, placebo-controlled, double-blind study of the safety and immunogenicity of the V180 vaccine in subjects who have previously received the live attenuated tetravalent vaccine (LATV) developed by the National Institute of Allergy and Infectious Diseases (protocol #V180-002 [CIR-301]). The study was designed to evaluate whether this recombinant subunit vaccine could boost the neutralizing antibody responses induced by dengue LATV. Twenty participants who had previously received one or two doses of dengue LATV were randomized and received a single dose of V180 nonadjuvanted ( N = 8), V180 adjuvanted with Alhydrogel™ (aluminum hydroxide gel, Brenntag Biosector, Frederikssund, Denmark) ( N = 8), or placebo ( N = 4). Immunogenicity was measured using a plaque reduction neutralization test at days 1, 15, 28, and 180 after vaccination. In addition, vaccine safety (solicited and unsolicited adverse events) was assessed using a vaccination report card for 28 days following vaccination, and serious adverse events were captured from the time of informed consent through the final study visit at 6 months after vaccination. The results of the study demonstrate that the V180 vaccine is generally well tolerated and immunogenic in these dengue-seropositive volunteers.

Dengue virus (DENV) is a mosquito-borne flavivirus that causes serious human disease. The current lack of an effective vaccine to simultaneously protect against the four serotypes of DENV in seronegative individuals is a major unmet medical need. Further, the immunological basis for protective immunity in the setting of DENV infection or vaccination is not fully understood. Our team has developed a live attenuated tetravalent dengue virus vaccine that provides complete protection in a human model of dengue virus challenge. The goal of this study was to define, in the context of protective human vaccination, the quality of vaccine-induced DENV-specific CD8 + and CD4 + T cells and the temporal dynamics associated with their formation and maintenance. Multifunctional, DENV-specific CD8 + and CD4 + T cells developed 8-14 days after vaccination and were maintained for at least 6 months. Virus-specific CD8 T + cells were a mixture of effector memory T cells (T EM ) and effector memory T cells re-expressing CD45RA (T EMRA ), with T EM cells predominating until day 21 post-vaccination and T EMRA cells thereafter. The majority of virus-specific CD4 + T cells were T EM with a small fraction being T EMRA . The frequency of virus-specific CD8 + and CD4 + T cells were further skewed to the T EMRA phenotype following either a second dose of the tetravalent vaccine or challenge with a single serotype of DENV. Collectively, our study has defined the phenotypic profile of antiviral CD8 + and CD4 + T cells associated with protective immunity to DENV infection and the kinetics of their formation and maintenance., (Copyright © 2020 Graham, Eisenhauer, Diehl, Pierce, Whitehead, Durbin, Kirkpatrick, Sette, Weiskopf, Boyson and Botten.)

Evolving evidence indicates that platelets and megakaryocytes (MKs) have unexpected activities in inflammation and infection; whether viral infections upregulate biologically active, antiviral immune genes in platelets and MKs is unknown, however. We examined antiviral immune genes in these cells in dengue and influenza infections, viruses that are global public health threats. Using complementary biochemical, pharmacological, and genetic approaches, we examined the regulation and function of interferon-induced transmembrane protein 3 (IFITM3), an antiviral immune effector gene not previously studied in human platelets and MKs. IFITM3 was markedly upregulated in platelets isolated from patients during clinical influenza and dengue virus (DENV) infections. Lower IFITM3 expression in platelets correlated with increased illness severity and mortality in patients. Administering a live, attenuated DENV vaccine to healthy subjects significantly increased platelet IFITM3 expression. Infecting human MKs with DENV selectively increased type I interferons and IFITM3. Overexpression of IFITM3 in MKs was sufficient to prevent DENV infection. In naturally occurring, genetic loss-of-function studies, MKs from healthy subjects harboring a homozygous mutation in IFITM3 (rs12252-C, a common single-nucleotide polymorphism in areas of the world where DENV is endemic) were significantly more susceptible to DENV infection. DENV-induced MK secretion of interferons prevented infection of bystander MKs and hematopoietic stem cells. Thus, viral infections upregulate IFITM3 in human platelets and MKs, and IFITM3 expression is associated with adverse clinical outcomes. These observations establish, for the first time, that human MKs possess antiviral functions, preventing DENV infection of MKs and hematopoietic stem cells after local immune signaling.

Background: Acute viral infections induce a rapid and transient increase in antibody-secreting plasmablasts. At convalescence, memory B cells (MBC) and long-lived plasma cells (LLPC) are responsible for long-term humoral immunity. Following an acute viral infection, the specific properties and relationships between antibodies produced by these B cell compartments are poorly understood., Methods: We utilized a controlled human challenge model of primary dengue virus serotype 2 (DENV2) infection to study acute and convalescent B-cell responses., Findings: The level of DENV2 replication was correlated with the magnitude of the plasmablast response. Functional analysis of plasmablast-derived monoclonal antibodies showed that the DENV2-specific response was dominated by cells producing DENV2 serotype-specific antibodies. DENV2-neutralizing antibodies targeted quaternary structure epitopes centered on domain III of the viral envelope protein (EDIII). Functional analysis of MBC and serum antibodies from the same subjects six months post-challenge revealed maintenance of the serotype-specific response in both compartments. The serum response mainly targeted DENV2 serotype-specific epitopes on EDIII., Interpretation: Our data suggest overall functional alignment of DENV2-specific responses from the plasmablast, through the MBC and LLPC compartments following primary DENV2 inflection. These results provide enhanced resolution of the temporal and specificity of the B cell compartment in viral infection and serve as framework for evaluation of B cell responses in challenge models., Funding: This study was supported by the Bill and Melinda Gates Foundation and the National Institutes of Health., (Copyright © 2019. Published by Elsevier B.V.)

Infection caused by the four serotypes of dengue virus (DENV-1-4) is a leading cause of mosquito-borne disease. Clinically-severe dengue disease is more common when secondary dengue infection occurs following prior infection with a heterologous dengue serotype. Other flaviviruses such as yellow fever virus, Japanese encephalitis virus, and Zika virus, can also elicit antibodies which are cross-reactive to DENV. As candidate dengue vaccines become available in endemic settings and for individuals who have received other flavivirus vaccines, it is important to examine vaccine safety and immunogenicity in these flavivirus-experienced populations. We performed a randomized, controlled trial of the National Institutes of Health live attenuated tetravalent dengue vaccine candidate (TV003) in fifty-eight individuals with prior exposure to flavivirus infection or vaccine. As in prior studies of this vaccine in flavivirus-naive volunteers, flavivirus-experienced subjects received two doses of vaccine six months apart and were followed closely for clinical events, laboratory changes, viremia, and neutralizing antibody titers. TV003 was well tolerated with few adverse events other than rash, which was predominately mild. Following one dose, 87% of vaccinees had an antibody response to all four serotypes (tetravalent response), suggesting a robust immune response. In addition, 76% of vaccinees were viremic; mean peak titers ranged from 0.68–1.1 log10 PFU/mL and did not differ by serotype. The second dose of TV003 was not associated with viremia, rash, or a sustained boost in antibody titers indicating that a single dose of the vaccine is likely sufficient to prevent viral replication and thus protect against disease. In comparison to the viremia and neutralizing antibody response elicited by TV003 in flavivirus-naïve subjects from prior studies, we found that subjects who were flavivirus-exposed prior to vaccination exhibited slightly higher DENV-3 viremia, higher neutralizing antibody titers to DENV-2, -3, and -4, and a higher tetravalent response frequency after TV003 administration. In summary, we demonstrate that the NIH tetravalent dengue vaccine TV003 is well-tolerated in flavivirus-experienced individuals and elicits robust post-vaccination neutralizing antibody titers., Trial Registration: ClinicalTrials.gov NCT01506570.

West Nile virus (WNV) is a major cause of mosquito-borne illness in the United States. Human disease ranges from mild febrile illness to severe fatal neurologic infection. Adults aged >60 years are more susceptible to neuroinvasive disease accompanied by a high mortality rate or long-lasting neurologic sequelae. A chimeric live attenuated West Nile virus vaccine, rWN/DEN4Δ30, was shown to be safe and immunogenic in healthy adults aged 18-50 years. This study evaluated rWN/DEN4Δ30 in flavivirus-naive adults aged 50-65 years and found it to be safe and immunogenic. Outbreaks of WNV infection tend to be unpredictable, and a safe and effective vaccine will be an important public health tool., (© The Author 2016. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail journals.permissions@oup.com.)

Unlabelled: The ideal dengue vaccine will provide protection against all serotypes of dengue virus and will be economical and uncomplicated in its administration. To determine the ability of a single dose of the live attenuated tetravalent dengue vaccine TV003 to induce a suitable neutralizing antibody response, a placebo-controlled clinical trial was performed in 48 healthy adults who received 2 doses of vaccine or placebo administered 12 months apart. Evaluation of safety, vaccine viremia, and neutralizing antibody response after each dose indicated that the first dose of vaccine was capable of preventing infection with the second dose, thus indicating that multiple doses are unnecessary., Clinical Trials Registration: NCT01782300., (Published by Oxford University Press for the Infectious Diseases Society of America 2016. This work is written by (a) US Government employee(s) and is in the public domain in the US.)

A dengue human challenge model can be an important tool to identify candidate dengue vaccines that should be further evaluated in large efficacy trials in endemic areas. Dengue is responsible for about 390 million infections annually. Protective efficacy results for the most advanced dengue vaccine candidate (CYD) were disappointing despite its ability to induce neutralizing antibodies against all four dengue virus (DENV) serotypes. TV003 is a live attenuated tetravalent DENV vaccine currently in phase 2 evaluation. To better assess the protective efficacy of TV003, a randomized double-blind, placebo-controlled trial in which recipients of TV003 or placebo were challenged 6 months later with a DENV-2 strain, rDEN2Δ30, was conducted. The primary endpoint of the trial was protection against dengue infection, defined as rDEN2Δ30 viremia. Secondary endpoints were protection against rash and neutropenia. All 21 recipients of TV003 who were challenged with rDEN2Δ30 were protected from infection with rDEN2Δ30. None developed viremia, rash, or neutropenia after challenge. In contrast, 100% of the 20 placebo recipients who were challenged with rDEN2Δ30 developed viremia, 80% developed rash, and 20% developed neutropenia. TV003 induced complete protection against challenge with rDEN2Δ30 administered 6 months after vaccination. TV003 will be further evaluated in dengue-endemic areas. The controlled dengue human challenge model can accelerate vaccine development by evaluating the protection afforded by the vaccine, thereby eliminating poor candidates from further consideration before the initiation of large efficacy trials., (Copyright © 2016, American Association for the Advancement of Science.)

Background: The 4 serotypes of dengue virus, DENV-1-4, are the leading cause of arboviral disease globally. The ideal dengue vaccine would provide protection against all serotypes after a single dose., Methods: Two randomized, placebo-controlled trials were performed with 168 flavivirus-naive adults to demonstrate the safety and immunogenicity of a live attenuated tetravalent dengue vaccine (TV003), compared with those of a second tetravalent vaccine with an enhanced DENV-2 component (TV005), and to evaluate the benefit of a booster dose at 6 months. Safety data, viremia, and neutralizing antibody titers were evaluated., Results: A single dose of TV005 elicited a tetravalent response in 90% of vaccinees by 3 months after vaccination and a trivalent response in 98%. Compared with TV003, the higher-dose DENV-2 component increased the observed frequency of immunogenicity to DENV-2 in the TV005 trial. Both the first and second doses were well tolerated. Neither vaccine viremia, rash, nor a significant antibody boost were observed following a second dose., Conclusions: A single subcutaneous dose of TV005 dengue vaccine is safe and induces a tetravalent antibody response at an unprecedented frequency among vaccinees. A second dose has limited benefit and appears to be unnecessary. Studies to confirm these findings and assess vaccine efficacy will now move to populations in regions where DENV transmission is endemic., Clinical Trials Registration: NCT01072786 and NCT01436422., (© The Author 2015. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Background: Campylobacter jejuni is a common cause of diarrhea and is associated with serious postinfectious sequelae. Although symptomatic and asymptomatic infections are recognized, protective immunity is not well understood. Previous data suggests that interferon γ (IFN-γ) may be associated with protection. To better define the clinical and immunologic development of protective immunity to C. jejuni, we assessed the ability of an initial infection to prevent clinical illness after a second experimental infection., Methods: Subjects with no clinical or immunologic evidence of prior infection with C. jejuni received an initial challenge with C. jejuni CG8421 with rechallenge 3 months later. The primary endpoint was campylobacteriosis, as defined by diarrhea and/or systemic signs. Close inpatient monitoring was performed. Serum immunoglobulin A (IgA) and immunoglobulin G (IgG), fecal IgA, IgA antibody-secreting cells (ASCs), and IFN-γ production were evaluated. All subjects were treated with antibiotics and were clinically well at discharge., Results: Fifteen subjects underwent a primary infection with C. jejuni CG8421; 14 (93.3%) experienced campylobacteriosis. Eight subjects received the second challenge, and all experienced campylobacteriosis with similar severity. Immune responses after primary infection included serum IgA, IgG, ASC, and IFN-γ production. Responses were less robust after secondary infection., Conclusions: In naive healthy adults, a single infection with CG8421 did not protect against campylobacteriosis. Although protection has been demonstrated with other strains and after continuous environmental exposure, our work highlights the importance of prior immunity, repeated exposures, and strain differences in protective immunity to C. jejuni., Clinical Trials Registration: NCT01048112.

There are currently no vaccines or therapeutics to prevent dengue disease which ranges in severity from asymptomatic infections to life-threatening illness. The National Institute of Allergy and Infectious Diseases (NIAID) Division of Intramural Research has developed live, attenuated vaccines to each of the four dengue serotypes (DENV-1-DENV-4). Two doses (10PFU and 1000PFU) of three monovalent vaccines were tested in human clinical trials to compare safety and immunogenicity profiles. DEN4Δ30 had been tested previously at multiple doses. The three dengue vaccine candidates tested (DEN1Δ30, DEN2/4Δ30, and DEN3Δ30/31) were very infectious, each with a human infectious dose 50%≤ 10PFU. Further, infectivity rates ranged from 90 to 100% regardless of dose, excepting DEN2/4Δ30 which dropped from 100% at the 1000PFU dose to 60% at the 10PFU dose. Mean geometric peak antibody titers did not differ significantly between doses for DEN1Δ30 (92 ± 19 vs. 214 ± 97, p=0.08); however, significant differences were observed between the 10PFU and 1000PFU doses for DEN2/4Δ30, 19 ± 9 vs. 102 ± 25 (p=0.001), and DEN3Δ30/31, 119 ± 135 vs. 50 ± 50 (p=0.046). No differences in the incidences of rash, neutropenia, or viremia were observed between doses for any vaccines, though the mean peak titer of viremia for DEN1Δ30 was higher at the 1000PFU dose (0.5 ± 0 vs. 1.1 ± 0.1, p=0.007). These data demonstrate that a target dose of 1000PFU for inclusion of each dengue serotype into a tetravalent vaccine is likely to be safe and generate a balanced immune response for all serotypes., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Background: Dengue virus (DENV) causes hundreds of millions of infections annually. Four dengue serotypes exist, and previous infection with one serotype increases the likelihood of severe disease with a second, heterotypic DENV infection., Methods: In a randomized, placebo-controlled study, the safety and immunogenicity of 4 different admixtures of a live attenuated tetravalent (LATV) dengue vaccine were evaluated in 113 flavivirus-naive adults. Serum neutralizing antibody levels to all 4 dengue viruses were measured on days 0, 28, 42, and 180., Results: A single dose of each LATV admixture induced a trivalent or better neutralizing antibody response in 75%-90% of vaccinees. There was no significant difference in the incidence of adverse events between vaccinees and placebo-recipients other than rash. A trivalent or better response correlated with rash and with non-black race (P < .0001). Black race was significantly associated with a reduced incidence of vaccine viremia., Conclusions: TV003 induced a trivalent or greater antibody response in 90% of flavivirus-naive vaccinees and is a promising candidate for the prevention of dengue. Race was identified as a factor influencing the infectivity of the LATV viruses, reflecting observations of the effect of race on disease severity in natural dengue infection.

The Laboratory of Infectious Diseases at the National Institute of Allergy and Infectious Diseases, National Institutes of Health has been engaged in an effort to develop a safe, efficacious, and affordable live attenuated tetravalent dengue vaccine (LATV) for more than ten years. Numerous recombinant monovalent DENV vaccine candidates have been evaluated in the SCID-HuH-7 mouse and in rhesus macaques to identify those candidates with a suitable attenuation phenotype. In addition, the ability of these candidates to infect and disseminate in Aedes mosquitoes had also been determined. Those candidates that were suitably attenuated in SCID-HuH-7 mice, rhesus macaques, and mosquitoes were selected for further evaluation in humans. This review will describe the generation of multiple candidate vaccines directed against each DENV serotype, the preclinical and clinical evaluation of these candidates, and the process of selecting suitable candidates for inclusion in a LATV dengue vaccine., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

We report the first instance of macrolide resistance developing in vivo following appropriate antibiotic use in a healthy volunteer as a part of a controlled human infection with Campylobacter jejuni. In vivo development of macrolide resistance may be an important contributor to antibiotic resistance in C. jejuni.

The recrudescence of infection with Campylobacter jejuni after appropriate antibiotic treatment has not been previously reported in an immunocompetent adult. We present the complete clinical, microbiologic, and immunologic evaluation of a closely monitored healthy male with recrudescent C. jejuni infection occurring in the absence of immunodeficiency following experimental infection with a well-characterized strain. After antibiotic treatment, the initial infection was clinically cleared and microbiologically undetectable. Subsequently, two episodes of recrudescence occurred, with no change in in vitro antibiotic sensitivity being detected. The immune responses of the individual were compared to those of other participants in the experimental infection study: innate immune responses, including fecal cytokines and C-reactive protein, were intact; however, measures of Campylobacter-specific adaptive immune responses were absent, including serum antibodies, antibody-secreting cells, and in vitro gamma interferon responses. No primary or secondary immunodeficiency was identified. Recrudescent Campylobacter infections after treatment may be more common than has previously been appreciated. This work adds to our understanding of the human immune response to natural Campylobacter infection and reiterates the importance of pathogen-specific adaptive immune responses to this globally important pathogen.

Background: A robust human challenge model for Campylobacter jejuni is an important tool for the evaluation of candidate vaccines. The previously established model conveys a potential risk of Guillain-Barré syndrome attributable to lipooligosaccharide ganglioside mimicry. This work establishes a new C. jejuni human challenge model that uses a strain (CG8421) without ganglioside mimicry and that applies Campylobacter-specific cellular immunity screening to achieve high attack rates at lower inoculum doses., Methods: Healthy Campylobacter-naive adults participated in an open-label challenge trial. Participants were dosed with C. jejuni CG8421 and followed as inpatients. Pattern of illness, bacterial shedding, and immunologic responses were determined., Results: Following screening, 23 subjects received 1 X 10(6) or 1 X 10(5) colony-forming units of C. jejuni, with attack rates (percentage of patients who became ill) of 100% (1 X 10(6) colony-forming units) or 93% (1 X 10(5) colony-forming units). Every subject shed CG8421; the median time to diarrhea onset was 72.3 h (interquartile range, 53.9-99.9 h). Symptoms included abdominal cramps (74%), nausea (65%), and fever (39%). No major safety concerns occurred, including bacteremia, hypotension, or postinfectious sequelae. Unexpectedly, recrudescent infection occurred in 2 subjects (1 subject without Campylobacter-specific adaptive immune responses and 1 with azithromycin resistance acquired in vivo); both infections cleared after receipt of additional antibiotics. Cumulative Campylobacter-specific immune responses were as follows: serologic response occurred in 87% (immunoglobulin [Ig] A) and 48% (IgG) of subjects, in vitro interferon-gamma production occurred in 91% of subjects, and 96% of subjects had IgA antibody-secreting cells and fecal IgA detected., Conclusions: The C. jejuni CG8421 challenge model provides a safe and effective tool, without the risk of Guillain-Barré syndrome. The model demonstrates high attack rates after lower doses of challenge inoculum, provides further understanding of immunologic responses, and permits future investigation of candidate Campylobacter vaccines.

Purpose: To report three cases of central serous chorioretinopathy (CSC) likely related to the use of body-building products containing ephedra., Methods: Observational case series of three patients who presented with signs and symptoms of CSC. All cases had ocular coherence tomography and fluorescein angiograms to confirm the diagnosis. All admitted to current or previous use of ephedra containing products for body building. No patient had a history of current or prior use of steroids., Results: The first patient presented in 2005 with a 7-month history of bilateral CSC. On careful history, the patient admitted to the use of ephedra during body-building exercises. After discontinuation of the ephedra, his CSC resolved. The second and third patients presented in 2007. Both had pigmented epithelial detachments in both eyes secondary to CSC and atrophic changes suggestive of old, resolved CSC. The second patient had admitted to the use of ephedra 3 years previously and Patient 3 was currently using an ephedra-containing body-building product. After Patient 3 discontinued the ephedra, his CSC too resolved., Conclusion: We report three cases of CSC related to the use of ephedra-containing products. All three cases were chronic, atypical, and bilateral in nature with two of three cases resolving after the discontinuation of the ephedra. This may be related to the sympathomimetic properties of ephedra as reported by Michael et al for pseudoephedrine. Given these findings, we suggest that questioning about ephedra products become standard when taking histories in suspected CSC cases.

Measurement of skin blood flow is a sensitive marker of C-fiber neurovascular dysfunction. It precedes development of abnormalities in diabetes mellitus, correlates with in vivo indices of the metabolic syndrome, and may be a "benchmark" for future studies on agents to improve microvascular dysfunction in diabetes mellitus. Skin blood flow can be measured under basal and stimulated conditions. There are different methods of evaluation. Iontophoresis and microdialysis are novel methods of drug delivery and the latter may be used as a means of extracting analytes in the skin. Theses methods are not invasive (iontophoresis) or minimally invasive (microdialysis). They can be performed repeatedly and safely in most patients. The use of microdialysis may be limited by sampling only water-soluble molecules. An alternative to microdialysis is iontophoresis, which works better with polar molecules. A combination of microdialysis and iontophoresis techniques can be useful in assessment of the pharmacokinetics of polar and nonpolar agents and the physiology and pathophysiology of the skin neurovascular system.

The physical and chemical processes that lead to the preferential escape of hydrogen over deuterium in the Martian atmosphere are studied in detail using a one-dimensional photochemical model. Comparison of our theory with recent observations of HDO suggests that, averaged over the planet, Mars contains 0.2 m of crustal water that is exchangeable with the atmosphere. Our estimate is considerably lower than recent estimates of subsurface water on Mars based on geomorphological analysis of Viking images. The estimate can be reconciled if only a small fraction of crustal water can exchange with the atmosphere.