Hepatitis C virus (HCV) infection is a major worldwide problem. Chronic hepatitis C is recognized as one of the major causes of cirrhosis, hepatocellular carcinoma, and liver failure. Although new, directly acting antiviral therapies are suggested to overcome the low efficacy and adverse effects observed for the current standard of treatment, an effective vaccine would be the only way to certainly eradicate HCV infection. Recently, polyhydroxybutyrate beads produced by engineered Escherichia coli showed efficacy as a vaccine delivery system. Here, an endotoxin-free E. coli strain ( Hepatitis C virus (HCV) is an etiologic agent of chronic hepatitis C (1). Chronic HCV infection affects more than 170 million people worldwide and is responsible for approximately 350,000 deaths each year (2). Viral exposure results in acute disease in a small proportion of cases, while the majority (80%) progress to chronic infection, causing liver inflammation that slowly progresses to cirrhosis, liver failure, hepatocellular carcinoma, and death (3).Despite a substantial decline in HCV transmission due to improved prevention strategies and the introduction of new and powerful targeted therapies, hepatitis C remains a huge health problem, justifying further endeavors to develop new vaccines. Indeed, the pool of asymptomatic chronic HCV carriers who represent an infectious reservoir will remain substantial for many years. Less than 30% of patients with chronic hepatitis C are aware of the infection, and only about 10% of patients are currently treated (4, 5). Therefore, even if new antivirals could cure 90% of patients, there would still be a considerable percentage of patients who would be excluded (6). Hence, development of a vaccine to prevent infection or to at least prevent progression to chronicity represents a significant unmet medical need and is of high priority.Since 1% of infected patients show an immune response clearing the infection and the rate of spontaneous resolution is higher in the case of reinfected patients, this demonstrates that the induction of protective immunity which prevents development of chronic disease is a feasible goal for the development of a preventive vaccine against HCV (7,8).The role of HCV-specific T cell responses in the outcome of primary HCV infection has been widely studied, although a single correlate of protection has not been determined. However, it is known that this type of immune response is a determinant in the clearance of the virus. Comparative studies in humans and chimpanzees have shown that widespread and long-lasting CD8 ϩ and CD4 ϩ T cell responses against multiple HCV regions are linked to spontaneous viral clearance (9, 10).However, there is also strong evidence that rapid induction of high-titer cross-neutralizing antibodies targeting HCV envelope proteins correlates with viral clearance and protects against reinfection (11, 12). Therefore, an optimal HCV vaccine probably needs to elicit broad cross-reactive cellular immune responses together with cross-neutralizing antibo...

The eradication of hepatitis C virus (HCV) infection is a public health priority. Despite the efficiency of treatment with direct-acting antivirals, the high cost of the therapy and the lack of accurate data about the HCV-infected population worldwide constitute important factors hampering this task. Hence, an affordable preventive vaccine is still necessary for reducing transmission and the future disease burden globally. In this work, chimeric proteins (EnvCNS3 and NS3EnvCo) encompassing conserved and immunogenic epitopes from the HCV core, E1, E2 and NS3 proteins were produced in Escherichia coli, and their immunogenicity was evaluated in BALB/c mice. The impact of recombinant HCV E2.680 protein and oligodeoxynucleotide 39M (ODN39M) on the immune response to chimeric proteins was also assessed. Immunization with chimeric proteins mixed with E2.680 enhanced the antibody and cellular response against HCV antigens and chimeric proteins. Interestingly, the combination of NS3EnvCo with E2.680 and ODN39M as adjuvant elicited a potent antibody response characterized by an increase in antibodies of the IgG2a subclass against E2.680, NS3 and chimeric proteins, suggesting the induction of a Th1-type response. Moreover, a cytotoxic T lymphocyte response and a broad response of IFN-γ-secreting cells against HCV antigens were induced with this formulation as well. This T cell response was able to protect vaccinated mice against challenge with a surrogate model based on HCV recombinant vaccinia virus. Overall, the vaccine candidate NS3EnvCo/E2.680/ODN39M might constitute an effective immunogen against HCV with potential for reducing the likelihood of viral persistence.

Background: The papaya mosaic virus (PapMV) vaccine platform is a rod-shaped nanoparticle made of the recombinant PapMV coat protein (CP) self-assembled around a noncoding single-stranded RNA (ssRNA) template. The PapMV nanoparticle induces innate immunity through stimulation of the Toll-like receptors (TLR) 7 and 8. The display of the vaccine antigen at the surface of the nanoparticle, associated with the co-stimulation signal via TLR7/8, ensures a strong stimulation of the immune response, which is ideal for the development of candidate vaccines. In this study, we assess the impact of where the peptide antigen is fused, whether at the surface or at the extremities of the nanoparticles, on the immune response directed to that antigen. Methods: Two different peptides from influenza A virus were used as model antigens. The conserved M2e peptide, derived from the matrix protein 2 was chosen as the B-cell epitope, and a peptide derived from the nucleocapsid was chosen as the cytotoxic T lymphocytes (CTL) epitope. These peptides were coupled at two different positions on the PapMV CP, the N- (PapMV-N) or the C-terminus (PapMV-C), using the transpeptidase activity of Sortase A (SrtA). The immune responses, both humoral and CD8+ T-cell-mediated, directed to the peptide antigens in the two different fusion contexts were analyzed and compared. The impact of coupling density at the surface of the nanoparticle was also investigated. Conclusions: The results demonstrate that coupling of the peptide antigens at the N-terminus (PapMV-N) of the PapMV CP led to an enhanced immune response to the coupled peptide antigens as compared to coupling to the C-terminus. The difference between the two vaccine platforms is linked to the enhanced capacity of the PapMV-N vaccine platform to stimulate TLR7/8. We also demonstrated that the strength of the immune response increases with the density of coupling at the surface of the nanoparticles.

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