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Three percent of the world's population is chronically infected with the hepatitis C virus (HCV) and at risk of developing liver cancer. Effective cellular immune responses are deemed essential for spontaneous resolution of acute hepatitis C and long-term protection. Here we describe a new T-cell HCV genetic vaccine capable of protecting chimpanzees from acute hepatitis induced by challenge with heterologous virus. Suppression of acute viremia in vaccinated chimpanzees occurred as a result of massive expansion of peripheral and intrahepatic HCV-specific CD8+ T lymphocytes that cross-reacted with vaccine and virus epitopes. These findings show that it is possible to elicit effective immunity against heterologous HCV strains by stimulating only the cellular arm of the immune system, and suggest a path for new immunotherapy against highly variable human pathogens like HCV, HIV or malaria, which can evade humoral responses. [ABSTRACT FROM AUTHOR]

Although clonal expansion is a hallmark of adaptive immunity, the location(s) where antigen‐responding T cells enter cell cycle and complete it have been poorly explored. This lack of knowledge stems partially from the limited experimental approaches available. By using Ki67 plus DNA staining and a novel strategy for flow cytometry analysis, we distinguished antigen‐specific CD8 T cells in G0, in G1 and in S‐G2/M phases of cell cycle after intramuscular vaccination of BALB/c mice with antigen‐expressing viral vectors. Antigen‐specific cells in S‐G2/M were present at early times after vaccination in lymph nodes (LNs), spleen and, surprisingly, also in the blood, which is an unexpected site for cycling of normal non‐leukaemic cells. Most proliferating cells had high scatter profile and were undetected by current criteria of analysis, which under‐estimated up to 6 times antigen‐specific cell frequency in LNs. Our discovery of cycling antigen‐specific CD8 T cells in the blood opens promising translational perspectives. [ABSTRACT FROM AUTHOR]

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) posed a threat to public health and the global economy, necessitating the development of various vaccination strategies. Mutations in the SPIKE protein gene, a crucial component of mRNA and adenovirus-based vaccines, raised concerns about vaccine efficacy, prompting the need for rapid vaccine updates. To address this, we leveraged PeptiCRAd, an oncolytic vaccine based on tumor antigen decorated oncolytic adenoviruses, creating a vaccine platform called PeptiVAX. First, we identified multiple CD8 T-cell epitopes from highly conserved regions across coronaviruses, expanding the range of T-cell responses to non-SPIKE proteins. We designed short segments containing the predicted epitopes presented by common HLA-Is in the global population. Testing the immunogenicity, we characterized T-cell responses to candidate peptides in peripheral blood mononuclear cells (PBMCs) from pre-pandemic healthy donors and ICU patients. As a proof of concept in mice, we selected a peptide with epitopes predicted to bind to murine MHC-I haplotypes. Our technology successfully elicited peptide-specific T-cell responses, unaffected by the use of unarmed adenoviral vectors or adeno-based vaccines encoding SPIKE. In conclusion, PeptiVAX represents a fast and adaptable SARS-CoV-2 vaccine delivery system that broadens T-cell responses beyond the SPIKE protein, offering potential benefits for vaccine effectiveness. [ABSTRACT FROM AUTHOR]

Mucosal-associated invariant T (MAIT) cells are innate sensors of viruses and can augment early immune responses and contribute to protection. We hypothesized that MAIT cells may have inherent adjuvant activity in vaccine platforms that use replication-incompetent adenovirus vectors. In mice and humans, ChAdOx1 (chimpanzee adenovirus Ox1) immunization robustly activated MAIT cells. Activation required plasmacytoid dendritic cell (pDC)–derived interferon (IFN)–a and monocyte-derived interleukin-18. IFN-a–induced, monocyte-derived tumor necrosis factor was also identified as a key secondary signal. All three cytokines were required in vitro and in vivo. Activation of MAIT cells positively correlated with vaccine-induced T cell responses in human volunteers and MAIT cell–deficient mice displayed impaired CD8+ T cell responses to multiple vaccine-encoded antigens. Thus, MAIT cells contribute to the immunogenicity of adenovirus vectors, with implications for vaccine design. [ABSTRACT FROM AUTHOR]

Rabies, caused by RNA viruses in the Genus Lyssavirus, is the most fatal of all infectious diseases. This neglected zoonosis remains a major public health problem in developing countries, causing the death of an estimated 25,000–159,000 people each year, with more than half of them in children. The high incidence of human rabies in spite of effective vaccines is mainly linked to the lack of compliance with the complicated administration schedule, inadequacies of the community public health system for local administration by the parenteral route and the overall costs of the vaccine. The goal of our work was the development of a simple, affordable and effective vaccine strategy to prevent human rabies virus infection. This next generation vaccine is based on a replication-defective chimpanzee adenovirus vector belonging to group C, ChAd155-RG, which encodes the rabies glycoprotein (G). We demonstrate here that a single dose of this vaccine induces protective efficacy in a murine model of rabies challenge and elicits strong and durable neutralizing antibody responses in vaccinated non-human primates. Importantly, we demonstrate that one dose of a commercial rabies vaccine effectively boosts the neutralizing antibody responses induced by ChAd155-RG in vaccinated monkeys, showing the compatibility of the novel vectored vaccine with the current post-exposure prophylaxis in the event of rabies virus exposure. Finally, we demonstrate that antibodies induced by ChAd155-RG can also neutralize European bat lyssaviruses 1 and 2 (EBLV-1 and EBLV-2) found in bat reservoirs. Author summary: Rabies still remains a neglected zoonosis after a long history of vaccination. Considering the severity of the disease and its continued high incidence in low-income countries, the development of a next generation vaccine is warranted. We utilized a group C, replication-defective chimpanzee adenovirus vector to develop a novel vaccine against rabies. Mice vaccinated with ChAd155-RG survived after rabies infection and non-human primates injected with a single dose of this vaccine developed strong and durable neutralizing antibody responses which could be effectively boosted with a licensed vaccine, demonstrating the compatibility of the novel vectored vaccine with the current post-exposure prophylaxis in the event of rabies virus exposure. Importantly, we show that ChAd155-RG induced neutralizing antibodies can neutralize also lyssavirus species (EBLV-1 and EBLV-2) found in bat reservoirs. These studies paved the way to the clinical testing of the ChAd155-RG based rabies vaccine as a single-dose, low cost, preventative rabies vaccine candidate. [ABSTRACT FROM AUTHOR]

So far, only three small outdated studies have investigated hepatitis C virus (HCV) incidence and risk factors among illicit drug users (DUs) in Italy. Thus, during 2007-2010, we conducted a prospective cohort study among DUs attending 17 Italian rehabilitation centers serving urban areas. Two hundred eighty-four HCV-uninfected DUs were prospectively followed by interview and anti-HCV antibody and RNA testing every 6 months. Incidence was calculated using the person-years method. Infection predictors were assessed by time-dependent Cox analysis. Participants were mostly male (83.4%), under opioid substitution therapy (OST) (78.9%), non-injecting DUs (67.9%), and with a mean age of 30.8. Ninety-one of 224 DUs initially under OST interrupted treatment during the follow-up. Overall HCV incidence was 5.83/100 person-years at risk (PYAR) [95% confidence intervals (CI), 3.63-9.38]. The incidence did not significantly differ according the participants' sociodemographic characteristics or the degree of urbanization of the towns involved in the study. The incidence was higher for DUs under than for those not under OST (6.23 vs 4.50/100 PYAR; p = 0.681). Incidence was also higher for those with than for those without OST interruption (7.17 vs 5.04/100 PYAR; p = 0.55). However, all these differences were non-significant. At last follow-up visit, a significant decrease in frequency of sharing equipment for preparation/using drugs (by injection or not) was observed by analyzing either the whole cohort or DUs under OST only. Anti-HCV seroconversion resulted independently associated with sharing drug preparation/use equipment, backloading, having a HCV-positive sexual partner, or household and (marginally) intravenous injection. In this study, HCV incidence was non-negligible and OST seemed to lack effectiveness in reducing it. In Italy, implementation of combined harm reduction interventions and antiviral treatment of chronically infected DUs would be needed. [ABSTRACT FROM AUTHOR]

The low number of envelope (Env) spikes presented on native HIV-1 particles is a major impediment for HIV-1 prophylactic vaccine development. We designed virus-like particle encoding adenoviral vectors utilizing SIVmac239 Gag as an anchor for full length and truncated HIV-1 M consensus Env. Truncated Env overexpressed VRC01 and 17b binding antigen on the surface of transduced cells while the full length Env vaccine presented more and similar amounts of antigen binding to the trimer conformation sensitive antibodies PGT151 and PGT145, respectively. The adenoviral vectors were used to prime Balb/c mice followed by sequential boosting with chimpanzee type 63, and chimpanzee type 3 adenoviral vectors encoding SIVmac239 Gag and full length consensus Env. Both vaccine regimens induced increasing titers of binding antibody responses after each immunization, and significant differences in immune responses between the two groups were observed after the final immunization. Full length Env priming skewed antibody responses towards gp41, while truncated Env priming induced responses primarily targeting gp120 containing and derived antigens. Importantly, no differences in neutralizing antibody responses were found between the different priming regimens as both induced high titered tier 1 neutralizing antibodies, but no tier 2 antibodies, possibly reflecting the similar presentation of trimer specific antibody epitopes. The described vaccine regimens provide insight into the effects of the HIV-1 Env cytoplasmic tail on epitope presentation and subsequent immune responses, which is relevant for the interpretation of current clinical trials that are using truncated Env as an immunogen. The regimens described here provide similar neutralization titers, and thus are useful for investigating the importance of specificity in non-neutralizing antibody mediated protection against viral challenge. [ABSTRACT FROM AUTHOR]

Recombinant adenoviral vectors (rAds) are lead vaccine candidates for protection against a variety of pathogens, including Ebola, HIV, tuberculosis, and malaria, due to their ability to potently induce T cell immunity in humans. However, the ability to induce protective cellular immunity varies among rAds. Here, we assessed the mechanisms that control the potency of CD8 Tcell responses in murine models following vaccination with human-, chimpanzee-, and simian-derived rAds encoding SIV-Gag antigen (Ag). After rAd vaccination, we quantified Ag expression and performed expression profiling of innate immune response genes in the draining lymph node. Human-derived rAd5 and chimpanzee-derived chAd3 were the most potent rAds and induced high and persistent Ag expression with low innate gene activation, while less potent rAds induced less Ag expression and robustly induced innate immunity genes that were primarily associated with IFN signaling. Abrogation of type I IFN or stimulator of IFN genes (STING) signaling increased Ag expression and accelerated CD8 T cell response kinetics but did not alter memory responses or protection. These findings reveal that the magnitude of rAd-induced memory CD8 T cell immune responses correlates with Ag expression but is independent of IFN and STING and provide criteria for optimizing protective CD8 T cell immunity with rAd vaccines. [ABSTRACT FROM AUTHOR]

Ebolavirus disease causes high mortality, and the current outbreak has spread unabated through West Africa. Human adenovirus type 5 vectors (rAd5) encoding ebolavirus glycoprotein (GP) generate protective immunity against acute lethal Zaire ebolavirus (EBOV) challenge in macaques, but fail to protect animals immune to Ad5, suggesting natural Ad5 exposure may limit vaccine efficacy in humans. Here we show that a chimpanzee-derived replication-defective adenovirus (ChAd) vaccine also rapidly induced uniform protection against acute lethal EBOV challenge in macaques. Because protection waned over several months, we boosted ChAd3 with modified vaccinia Ankara (MVA) and generated, for the first time, durable protection against lethal EBOV challenge. [ABSTRACT FROM AUTHOR]

The orthodox role of the invariant chain (CD74; Ii) is in antigen presentation to CD4+ T cells, but enhanced CD8+ T cells responses have been reported after vaccination with vectored viral vaccines encoding a fusion of Ii to the antigen of interest. In this study we assessed whether fusion of the malarial antigen, ME-TRAP, to Ii could increase the vaccine-induced CD8+ T cell response. Following single or heterologous prime-boost vaccination of mice with a recombinant chimpanzee adenovirus vector, ChAd63, or recombinant modified vaccinia virus Ankara (MVA), higher frequencies of antigen-specific CD4+ and CD8+ T cells were observed, with the largest increases observed following a ChAd63-MVA heterologous prime-boost regimen. Studies in non-human primates confirmed the ability of Ii-fusion to augment the T cell response, where a 4-fold increase was maintained up to 11 weeks after the MVA boost. Of the numerous different approaches explored to increase vectored vaccine induced immunogenicity over the years, fusion to the invariant chain showed a consistent enhancement in CD8+ T cell responses across different animal species and may therefore find application in the development of vaccines against human malaria and other diseases where high levels of cell-mediated immunity are required. [ABSTRACT FROM AUTHOR]

Despite the recent progress in the development of new antiviral agents, hepatitis C virus (HCV) infection remains a major global health problem, and there is a need for a preventive vaccine. We previously reported that adenoviral vectors expressing HCV nonstructural proteins elicit protective T cell responses in chimpanzees and were immunogenic in healthy volunteers. Furthermore, recombinant HCV E1E2 protein formulated with adjuvant MF59 induced protective antibody responses in chimpanzees and was immunogenic in humans. To develop an HCV vaccine capable of inducing both T cell and antibody responses, we constructed adenoviral vectors expressing full-length and truncated E1E2 envelope glycoproteins from HCV genotype 1b. Heterologous prime-boost immunization regimens with adenovirus and recombinant E1E2 glycoprotein (genotype 1a) plus MF59 were evaluated in mice and guinea pigs. Adenovirus prime and protein boost induced broad HCV-specific CD8+ and CD4+ T cell responses and functional Th1-type IgG responses. Immune sera neutralized luciferase reporter pseudoparticles expressing HCV envelope glycoproteins (HCVpp) and a diverse panel of recombinant cell culture-derived HCV (HCVcc) strains and limited cellto- cell HCV transmission. This study demonstrated that combining adenovirus vector with protein antigen can induce strong antibody and T cell responses that surpass immune responses achieved by either vaccine alone. [ABSTRACT FROM AUTHOR]

Despite viral vectors being potent inducers of antigen-specific T cells, strategies to further improve their immunogenicity are actively pursued. Of the numerous approaches investigated, fusion of the encoded antigen to major histocompatibility complex class II-associated invariant chain (Ii) has been reported to enhance CD8+ T-cell responses. We have previously shown that adenovirus vaccine encoding nonstructural (NS) hepatitis C virus (HCV) proteins induces potent T-cell responses in humans. However, even higher T-cell responses might be required to achieve efficacy against different HCV genotypes or therapeutic effect in chronically infected HCV patients. In this study, we assessed fusion of the HCV NS antigen to murine and human Ii expressed by the chimpanzee adenovirus vector ChAd3 or recombinant modified vaccinia Ankara in mice and nonhuman primates (NHPs). A dramatic increase was observed in outbred mice in which vaccination with ChAd3 expressing the fusion antigen resulted in a 10-fold increase in interferon-γ+ CD8+ T cells. In NHPs, CD8+ T-cell responses were enhanced and accelerated with vectors encoding the Ii-fused antigen. These data show for the first time that the enhancement induced by vector vaccines encoding li-fused antigen was not species specific and can be translated from mice to NHPs, opening the way for testing in humans. [ABSTRACT FROM AUTHOR]

Hepatitis C virus (HCV) is endemic in many countries due to its high propensity for establishing persistence. The presence of HCV-specific T cells in subjects repeatedly exposed to HCV who test negative for HCV RNA and antibodies and who do not have any history of HCV infection has been interpreted as T cell-mediated protection. Here, we show in nonhuman primates that repeated exposure to human plasma with trace amounts of HCV induced HCV-specific T cells without seroconversion and systemic viremia but did not protect upon subsequent HCV challenge. Rather, HCV-specific recall and de novo T cell responses, as well as intrahepatic T cell recruitment and interferon-γ (IFN-γ) production, were suppressed upon HCV challenge, concomitant with quantitative and qualitative changes in regulatory T cells (Treg cells) that occurred after subinfectious HCV exposure and increased after HCV challenge. In vitro Treg cell depletion restored HCV-specific T cell responses. Thus, T cells primed by trace amounts of HCV do not generate effective recall responses upon subsequent HCV infection. Subinfectious HCV exposure predisposes to Treg cell expansion, which suppresses effector T cells during subsequent infection. Strategies to reverse this exposure-induced immune suppression should be examined to aid in the development of T cell−based vaccines against HCV and other endemic pathogens. [ABSTRACT FROM AUTHOR]

IL28B.rs12979860 CC genotype has been associated with spontaneous clearance of hepatitis C virus (HCV). This prospective study suggests a relationship between CC genotype, HCV-specific T-cell response, and acute disease resolution, thus suggesting a possible important role of cell-mediated immunity in favoring HCV clearance in CC patients.Background. A single-nucleotide polymorphism (SNP; rs12979860) near the IL28B gene has been associated with spontaneous and treatment-induced hepatitis C virus clearance. We investigated predictors of spontaneous disease resolution in a cohort of patients with acute hepatitis C (AHC), analyzing epidemiological, clinical and virological parameters together with IL28B.rs12979860 genotypes and cell-mediated immunity (CMI).Methods. Fifty-six symptomatic AHC patients were enrolled and followed prospectively. CMI was measured in 31 patients at multiple time points by interferon-γ enzyme-linked immunospot assay and was correlated to the IL28B.rs12979860 SNP.Results. Eighteen patients had a self-limiting AHC that was associated with female sex (P = .028), older age (P = .018), alanine aminotransferase level >1000 U/L (P = .027), total bilirubin level >7 mg/dL (P = .036), and IL28B.rs12979860 genotype CC (P = .030). In multivariate analysis, only CC genotype was independently associated with self-limiting AHC (odds ratio, 5.3; 95% confidence interval, 1.1–26.5). Patients with the CC genotype with self-limiting AHC had a stronger (P = .02) and broader (P = .013) CMI than patients with the CT genotype with chronically evolving AHC. In patients with chronically evolving disease, CC genotype was associated with a broader CMI compared to CT genotype (P = .028). A negative CMI was more frequently associated with CT genotype among persistently infected patients (P = .043) and with persistent infection among CT patients (P = .033).Conclusions. Self-limiting AHC was independently associated with CC genotype. The correlation between IL28B.rs12979860 genotypes and CMI is suggestive of a possible important role of CMI in favoring hepatitis C virus clearance in CC patients. [ABSTRACT FROM PUBLISHER]

Background & Aims: The lack of consensus on the optimal timing, regimen, and duration of treatment, in patients with acute HCV infection, stimulates the research on both favourable outcome predictors and individualized treatment regimens. This study aimed at investigating the impact of IL28B SNP rs12979860 alone or in combination with HLA class II alleles in both predicting spontaneous viral clearance and individualizing treatment strategies for patients with HCV persistence, after acute HCV exposure. Methods: 178 patients with AHC, consecutively treated with interferon alone or in combination with ribavirin, starting within or after 48weeks from the diagnosis of AHC, were tested for IL28B SNPs and HLA class II alleles. Results: Spontaneous viral clearance was achieved in 28% of 169 patients available for genetic testing. Factors associated with HCV elimination were jaundice (OR 2.75, 95% CI 1.31–5.77) and IL28B CC (OR 3.87, CI 1.71–8.51), but not HLA alleles. In CT/TT patients without jaundice, NPV for virus persistence was 98%. In patients with IL28B CT/TT, starting treatment 48weeks after the onset was significantly associated with lower rates of response (28% vs. 100%, p =0.027). By contrast, no significant differences in the rate of SVR were observed for CC carriers who started treatment later (65% vs. 85%, p =1.0). Conclusions: In patients with acute HCV hepatitis, lack of viral clearance may be predicted by absence of jaundice and IL28B CT/TT genotype; in patients with these characteristics, treatment needs to be started immediately. [Copyright &y& Elsevier]

Recombinant adenoviral vectors (rAds) are the most potent recombinant vaccines for eliciting CD8+ T cell-mediated immunity in humans; however, prior exposure from natural adenoviral infection can decrease such responses. In this study we show low seroreactivity in humans against simian- (sAd11, sAd16) or chimpanzee-derived (chAd3, chAd63) compared with human-derived (rAd5, rAd28, rAd35) vectors across multiple geographic regions. We then compared the magnitude, quality, phenotype, and protective capacity of CD8+ T cell responses in mice vaccinated with rAds encoding SIV Gag. Using a dose range (1 × 107-109 particle units), we defined a hierarchy among rAd vectors based on the magnitude and protective capacity of CD8+ T cell responses, from most to least, as: rAd5 and chAd3, rAd28 and sAd11, chAd63, sAd16, and rAd35. Selection of rAd vector or dose could modulate the proportion and/or frequency of IFN-γ+TNF-α+IL-2+ and KLRG1+CD127-CD8+ T cells, but strikingly ~30-80% of memory CD8+ T cells coexpressed CD127 and KLRG1. To further optimize CD8+ T cell responses, we assessed rAds as part of prime-boost regimens. Mice primed with rAds and boosted with NYVAC generated Gag-specific responses that approached ~60% of total CD8+ T cells at peak. Alternatively, priming with DNA or rAd28 and boosting with rAd5 or chAd3 induced robust and equivalent CD8+ T cell responses compared with prime or boost alone. Collectively, these data provide the immunologic basis for using specific rAd vectors alone or as part of prime-boost regimens to induce CD8+ T cells for rapid effector function or robust long-term memory, respectively. [ABSTRACT FROM AUTHOR]

Background & Aims: Hepatitis C virus (HCV)-induced end-stage liver disease is currently the major indication for liver transplantation in the Western world. After transplantation, the donor liver almost inevitably becomes infected by the circulating virus and disease progression is accelerated in immune suppressed transplant patients. The current standard therapy, based on pegylated interferon and ribavirin, induces severe side effects and is often ineffective in this population. Therefore, new strategies to prevent graft re-infection are urgently needed. We have previously shown that monoclonal antibodies (mAbs) against the HCV co-receptor scavenger receptor class B type I (SR-BI/Cla1) inhibit infection by different HCV genotypes in cell culture. Methods: Using phage display libraries, we have generated a large set of novel human mAbs against SR-BI and evaluated their effectiveness in preventing HCV infection and direct cell-to-cell spread in vitro and in vivo using uPA-SCID mice with a humanized liver. Results: Eleven human monoclonal antibodies were generated that specifically recognize SR-BI. Two antibodies, mAb8 and mAb151, displayed the highest binding and inhibitory properties and also interfered with direct cell-to-cell spread in vitro. Studies in humanized mice showed that both antibodies were capable of preventing HCV infection and could block intrahepatic spread and virus amplification when administered 3days after infection. Interestingly, anti-SR-BI therapy was effective against an HCV variant that escaped the control of the adaptive immune response in a liver transplant patient. Conclusions: The anti-SR-BI mAbs generated in this study may represent novel therapeutic tools to prevent HCV re-infection of liver allografts. [Copyright &y& Elsevier]

Abstract: Malaria is a major health problem as nearly half of the human population is exposed to this parasite causing around 600 million clinical cases annually. Prime-boost regimes using simian adenoviral vectors and MVA expressing the clinically relevant Plasmodium falciparum ME.TRAP antigen have shown outstanding protective efficacy in mouse models. We now extend those observations to macaque monkeys. Immunisation with AdCh63 elicited a median response of 869 IFN-γ SFC/million PBMCs to ME.TRAP and responses were boosted by MVA to reach 5256 SFC/million PBMCs, increasing at the same time the breadth of the T cell responses to cover the complete ME.TRAP antigen. Intramuscular vaccination was more immunogenic than the intradermal route, and MVA could be used repeatedly for up to 3 times to boost adenovirus-primed responses. An interval of 16 weeks between repeated MVA injections was optimal to enhance cytokine production by T cells and improve the CD8 multifunctional responses. Antibodies to TRAP were exceptionally high and maintained for a long period of time after the prime-boost regime. These results in non-human primates highlight the potential of this vaccination regime and encourage its future use in clinical trials. [ABSTRACT FROM AUTHOR]

Abstract: The ability of HCV to mutate in response to cytotoxic T lymphocyte (CTL) pressure is increasingly recognized, but the influence of such a mechanism in viral persistence and final disease outcome has not been ascertained. In this study, we performed a detailed longitudinal analysis of cell mediated immunity and HCV evolution in two self limiting and two chronically evolving HCV acutely infected patients, one of whom transiently controlled viremia. Aminoacid mutations in immunodominant regions of viruses were observed in all patients, although they conferred viral escape from CTL responses only in chronically infected individuals. Resurgence of viremia coincided with the replacement of the original virus quasispecies with mutant viruses that had escaped recognition by primary CD8+ T cell responses and infection persisted in the presence of variant viruses which were less efficiently recognized by preexisting and de novo induced T cell responses. [Copyright &y& Elsevier]

Peripheral blood T-cell responses are used as biomarkers in hepatitis C virus (HCV) vaccine trials. However, it is not clear how T-cell responses in the blood correlate with those in the liver, the infection site. By studying serial liver and blood samples of five vaccinated and five mock-vaccinated control chimpanzees during acute HCV infection, we demonstrate a correlation between HCV-specific CD8 T-cell responses in the blood and molecular and functional markers of T-cell responses in the liver. Thus, HCV-specific CD8 T-cell responses in the blood are valid markers for intrahepatic T-cell activity. [ABSTRACT FROM AUTHOR]

Background/Aims: Several studies suggest that the evolutionary rate of HVR1 sequence in acute HCV hepatitis derives from the action of a continuous immune-driven positive selection. However, these studies have not been performed examining the relationship between HVR1 evolution and the development of specific immunity to autologous HVR1 sequences. Methods: We performed a longitudinal analysis of HVR1 sequences and specific antibodies and CD4+ T cells in ten HCV acutely infected patients with different clinical outcomes (recovery versus persistence). Results: We showed that although both recovered and chronically evolving individuals developed IFN-γ+ T cells specific for Core and NS sequences, HVR1-specific CD4+ T cells were detected only in patients clearing the virus. On the contrary, all patients displayed anti-HVR1 antibodies that recognized sequences exclusively carried by autologous viruses. Measurements of genetic diversity and the number of non-synonymous per synonymous substitutions within HVR1 sequences before and after antibody appearance showed an increase of these parameters only in concomitance with the appearance of anti-HVR1 antibodies. Conclusions: The evidence that anti-HVR1 antibodies favor HVR1 variant selection suggests that viral complexity in chronically infected patients could represent a virus adaptive strategy to escape the continuous selective process mediated by anti-HVR1 antibodies. [Copyright &y& Elsevier]

Success in resolving hepatitis C virus (HCV) infection has been correlated to vigorous, multispecific, and sustained CD8+ T-cell response in humans and chimpanzees. The efficacy of inducing T-cell-mediated immunity by recombinant serotype 5 adenovirus vector has been proven in many animal models of infectious diseases, but its immunogenicity can be negatively influenced by preexisting immunity against the vector itself. To evaluate the less prevalent adenovirus serotype 6 (Ad6) as an alternative vector for and HCV vaccine development, we have generated serotype 5 and 6 adenoviral vectors directing expression of the nonstructural region of HCV (MRKAd5-NSmut and MRKAd6-NSmut). Immunogenicity studies in mice showed that the two vectors induced comparable T-cell responses but that only MRKAd6-NSmut was not suppressed in the presence of anti-Ad5 immunity. In contrast, preexisting anti-Ad5 immunity dramatically blunted the immunogenicity of the serotype 5-based HCV vector. Furthermore, MRKAd6-NSmut showed equivalent potency, breadth, and longevity of HCV-specific T-cell responses in rhesus macaques as the corresponding Ad5-based vector over a wide range of doses and was capable of boosting DNA-primed animals even if administered at low doses. These data support the use of the MRKAd6-NSmut for anti-HCV immunotherapy and, more generally, for the Ad6 serotype as a better genetic vaccine vehicle than Ad5. [ABSTRACT FROM AUTHOR]

Reference 1 Napolitano F, Merone R, Abbate A, Ammendola V, Horncastle E, Lanzaro F, et al. (2020) A next generation vaccine against human rabies based on a single dose of a chimpanzee adenovirus vector serotype C. PLoS Negl Trop Dis14(7): e0008459. https://doi.org/10.1371/journal.pntd.0008459, 32667913 The twelfth author's name is spelled incorrectly. [Extracted from the article]

• Viral vectored vaccines against infectious diseases: clinical and immunological data. • Use of viral vectors for heterologous prime/boost regimens. • Viral vectors as a tool for vaccine preparedness. • Renaissance of cancer vaccines and the use of viral vectors. • Oncolytic viruses as 'endovaccines'. Since the discovery in 1796 by Edward Jenner of vaccinia virus as a way to prevent and finally eradicate smallpox, the concept of using a virus to fight another virus has evolved into the current approaches of viral vectored genetic vaccines. In recent years, key improvements to the vaccinia virus leading to a safer version (Modified Vaccinia Ankara, MVA) and the discovery that some viruses can be used as carriers of heterologous genes encoding for pathological antigens of other infectious agents (the concept of 'viral vectors') has spurred a new wave of clinical research potentially providing for a solution for the long sought after vaccines against major diseases such as HIV, TB, RSV and Malaria, or emerging infectious diseases including those caused by filoviruses and coronaviruses. The unique ability of some of these viral vectors to stimulate the cellular arm of the immune response and, most importantly, T lymphocytes with cell killing activity, has also reawakened the interest toward developing therapeutic vaccines against chronic infectious diseases and cancer. To this end, existing vectors such as those based on Adenoviruses have been improved in immunogenicity and efficacy. Along the same line, new vectors that exploit viruses such as Vesicular Stomatitis Virus (VSV), Measles Virus (MV), Lymphocytic choriomeningitis virus (LCMV), cytomegalovirus (CMV), and Herpes Simplex Virus (HSV), have emerged. Furthermore, technological progress toward modifying their genome to render some of these vectors incompetent for replication has increased confidence toward their use in infant and elderly populations. Lastly, their production process being the same for every product has made viral vectored vaccines the technology of choice for rapid development of vaccines against emerging diseases and for 'personalised' cancer vaccines where there is an absolute need to reduce time to the patient from months to weeks or days. Here we review the recent developments in viral vector technologies, focusing on novel vectors based on primate derived Adenoviruses and Poxviruses, Rhabdoviruses, Paramixoviruses, Arenaviruses and Herpesviruses. We describe the rationale for, immunologic mechanisms involved in, and design of viral vectored gene vaccines under development and discuss the potential utility of these novel genetic vaccine approaches in eliciting protection against infectious diseases and cancer. [ABSTRACT FROM AUTHOR]

Background The development of a safe and effective vaccine to prevent chronic hepatitis C virus (HCV) infection is a critical component of elimination efforts, providing the rationale for the first HCV vaccine efficacy trial. Methods In a randomized, multicenter, double-blind, placebo-controlled efficacy trial (NCT01436357), we evaluated a recombinant chimpanzee adenovirus 3 vector vaccine prime followed by a recombinant modified vaccinia Ankara boost, both encoding nonstructural proteins of HCV. HCV-uninfected adults 18–45 years old at-risk for HCV infection due to injection drug use were randomized to receive the prime-boost regimen or placebo at Days 0 and 56. Trial participants were monitored for vaccine reactogenicity, adverse events, and HCV viremia. Vaccine safety, immunogenicity, and efficacy against progression to chronic HCV infection were assessed. Results A total of 455 subjects received the prime-boost regimen or two doses of placebo, with 202 and 199 in the respective groups included in the according-to-protocol efficacy cohort. Overall incidence of infection was 14.1 infections per 100 person-years. There were no differences in development of chronic infection between vaccine and placebo arms, with 14 chronically infected subjects in each group. Specifically, the vaccine efficacy in preventing chronic infection was −0.53 (95% confidence interval [CI], −2.5 to 0.34). Of vaccinated subjects, 78% generated T-cell responses to ≥1 vaccine-encoded HCV antigens. The vaccine was generally safe and well tolerated with no serious vaccine-related adverse events. There were more solicited reports of adverse events after either injection in the vaccine group (81%) than in the placebo group (59%), with the difference mainly due to injection-site reactions. Serious adverse events and deaths occurred with similar frequencies in the two groups. Conclusion A randomized, placebo controlled, Phase I/II trial of a prime-boost vaccine to prevent chronic HCV infection was completed in an at-risk population, demonstrating the feasibility of conducting rigorous vaccine research in people who inject drugs. The regimen elicited robust immune responses without evident safety concerns, but did not provide protection against chronic HCV infection. Disclosures Ventzislav Vassilev, PhD, GlaxoSmithKlein Vaccines (Employee), Lan Lin, MD, GlaxoSmithKlein Vaccines (Employee), Alfredo Nicosia, PhD, ReiThera (Employee, Shareholder), Antonella Folgori, PhD, ReiThera (Employee), ReiThera (Employee, Shareholder. Other Authors: No reported disclosures. [ABSTRACT FROM AUTHOR]

Given the failures of nonreplicating vaccines against chronic hepatitis C virus (HCV) infection, we hypothesized that a replicating viral vector may provide protective immunity. Four chimpanzees were immunized transdermally twice with recombinant vaccinia viruses (rVV) expressing HCV genes. After challenge with 24 50% chimpanzee infective doses of homologous HCV, the two control animals that had received only the parental VV developed chronic HCV infection. All four immunized animals resolved HCV infection. The difference in the rate of chronicity between the immunized and the control animals was close to statistical significance (P = 0.067). Immunized animals developed vigorous gamma interferon enzyme-linked immunospot responses and moderate proliferative responses. To investigate cross-genotype protection, the immunized recovered chimpanzees were challenged with a pool of six major HCV genotypes. During the acute phase after the multigenotype challenge, all animals had high-titer viremia in which genotype 4 dominated (87%), followed by genotype 5 (13%). However, after fluctuating low-level viremia, the viremia finally turned negative or persisted at very low levels. This study suggests the potential efficacy of replicating recombinant vaccinia virus-based immunization against chronic HCV infection. [ABSTRACT FROM AUTHOR]