Induction of Genotype Cross-Reactive, Hepatitis C Virus-Specific, Cell-Mediated Immunity in DNA-Vaccinated Mice

Abstract

A universal hepatitis C virus (HCV) vaccine should elicit multiantigenic, multigenotypic responses, which are more likely to protect against challenge with the range of genotypes and subtypes circulating in the community. A vaccine cocktail and vaccines encoding consensus HCV sequences are attractive approaches to achieve this goal. Consequently, in a series of mouse vaccination studies, we compared the immunogenicity of a DNA vaccine encoding a consensus HCV nonstructural 5B (NS5B) protein to that of a cocktail of DNA plasmids encoding the genotype 1b (Gt1b) and Gt3a NS5B proteins. To complement this study, we assessed responses to a multiantigenic cocktail regimen by comparing a DNA vaccine cocktail encoding Gt1b and Gt3a NS3, NS4, and NS5B proteins to a single-genotype NS3/4/5B DNA vaccine. To thoroughly evaluate cytotoxic T lymphocyte (CTL) and T helper (Th) cell responses against Gt1b and Gt3a HCV peptide-pulsed target cells, we exploited a novel fluorescent-target array (FTA). FTA and enzyme-linked immunosorbent spot (ELISpot) analyses collectively indicated that the cocktail regimens elicited higher responses to Gt1b and Gt3a NS5B proteins than those with the consensus vaccine, while the multiantigenic DNA cocktail significantly increased the responses to NS3 and NS5B compared to those elicited by the single-genotype vaccines. Thus, a DNA cocktail vaccination regimen is more effective than a consensus vaccine or a monovalent vaccine at increasing the breadth of multigenotypic T cell responses, which has implications for the development of vaccines for communities where multiple HCV genotypes circulate. Despite the development of highly effective direct-acting antivirals (DAA), infections with hepatitis C virus (HCV) continue, particularly in countries where the supply of DAA is limited. Furthermore, patients who eliminate the virus as a result of DAA therapy can still be reinfected. Thus, a vaccine for HCV is urgently required, but the heterogeneity of HCV strains makes the development of a universal vaccine difficult. To address this, we developed a novel cytolytic DNA vaccine which elicits robust cell-mediated immunity (CMI) to the nonstructural (NS) proteins in vaccinated animals. We compared the immune responses against genotypes 1 and 3 that were elicited by a consensus DNA vaccine or a DNA vaccine cocktail and showed that the cocktail induced higher levels of CMI to the NS proteins of both genotypes. This study suggests that a universal HCV vaccine can most readily be achieved by use of a DNA vaccine cocktail.

Genetically Modified Mouse Mesenchymal Stem Cells Expressing Non-Structural Proteins of Hepatitis C Virus Induce Effective Immune Response

“…Thus, when immunizing with mMSCs, we achieve a functionally active T-cell response to several HCV proteins simultaneously, including different genotypes. This result is very important as an HCV vaccine should elicit multiantigenic, multigenotypic responses that should protect against challenge with the range of genotypes and subtypes circulating in the community [29]. We also hope that usage of more conserved viral proteins (i.e.…”

“…The non-structural proteins are considered as the dominant targets for CD8+ and CD4+ cells [27]. A robust HCV-specific CD8+ and CD4+ T cell responses to the non-structural proteins has the potential to restrict infection, eliminate virus-infected cells after challenge, and prevent persistent infection at the very least [29].…”

A Hepatitis C Virus DNA Vaccine Encoding a Secreted, Oligomerized Form of Envelope Proteins Is Highly Immunogenic and Elicits Neutralizing Antibodies in Vaccinated Mice

“…The frequency of mouse IFN-γ secreting E1 or E2-specific T cells was measured by ELISpot assay as described previously (49,51). Briefly, red blood cell-depleted splenocytes from vaccinated mice, at 5 × 10 5 cells per well, were stimulated with 4 µg/ml of either E1 or E2 peptides ( peptides, respectively.…”

“…We have previously developed novel DNA vaccines capable of generating robust CD4 + and CD8 + T cell responses against NS proteins 3, 4A, 4B, and 5B (51, 52) similar to those observed during resolution of acute HCV infection. We also recently showed that a multigenotypic DNA cocktail vaccine encoding gt1b NS5B proteins and gt3a induced higher CMI responses to gt1b and gt3a NS5B proteins than a DNA vaccine encoding a global consensus sequence (49), while a multiantigenic DNA vaccine cocktail encoding gt1b and gt3a NS3, NS4, and NS5B proteins significantly improved the responses to NS3 and NS5B compared to those induced by the individual-genotype vaccines (49). Further experiments should be conducted to assess whether a DNA cocktail vaccine comprising the envelope constructs reported in this study in combination with the DNA vaccine encoding NS proteins can elicit both anti-E1E2 NAb and CMI responses to the NS proteins.…”

“…However, DNA vaccines often induce poor immune responses in large animals despite being effective in mice (45), and require adjuvants for maximum effect (46). Co-administration or co-expression of a DNA vaccine with a plasmid encoding immunomodulatory proteins, such as interleukin (IL)-12 (48) or cytolytic adjuvants such as perforin (49)(50)(51)(52)(53) represent strategies employed to boost antigen-specific immunity following DNA vaccination.…”