Cross Reactive Cellular Immune Response to HCV Genotype 1 and 4 Antigens among Genotype 4 Exposed Subjects

<div><p>Background</p><p>Hepatitis C Virus (HCV) infection is a global health burden particularly in Egypt, where HCV genotype 4a (GT-4a) predominates. The prevention and control of HCV infection will remain a challenge until the development of an effective vaccine that protects against different genotypes. Several HCV GT-1-based vaccines are in different stages of clinical trials, but antigenic differences could make protection against other genotypes problematic. In this regard, data comparing the cell-mediated immune (CMI) response to different HCV genotypes are limited. We aimed to <i>ex vivo</i> investigate whether GT-1-based vaccine may protect against HCV GT-4 infections. This was carried out on samples collected from genotype 4 infected/exposed subjects.</p><p>Methods/Principal Findings</p><p>The CMI responses of 35 subjects; infected with HCV GT-4/or who had spontaneously-resolved the infection and 10 healthy control subjects; to two sets of seven HCV overlapping 15-mer peptide pools derived from both genotypes; and covering most of the viral proteins; were evaluated. This was carried out using an interferon gamma (IFNγ) enzyme-linked immunospot (ELISpot) assay. Peripheral blood mononuclear cells (PBMC) from 17 subjects (48%) responded to at least one peptide pool derived from GT-1b/GT-4a with 13 subjects responding to peptide pools from both genotypes. A strong correlation was found in the responses to both genotypes (<i>r</i> = 0.82, <i>p</i><0.001; 95% confidence interval = 0.562–0.933). The average IFNγ total spot forming cells (SFC)/10⁶ PBMC (±SE) from the responding subjects for GT-1b and GT-4a was 216±56 and 199±55, respectively (<i>p</i> = 0.833). Also, there were no significant differences between those who cleared their HCV infection or who remained HCV-RNA positive (<i>p</i> = 0.8).</p><p>Conclusion/Significance</p><p>Our data suggest that an effective GT-1b vaccine could protect from GT-4a infection. These data could help in HCV rationale vaccine design and efficacy studies and further our understanding of HCV cross protection against different genotypes.</p></div

High correlation between cell-mediated immune response to HCV-pooled peptides derived from genotypes 1b and 4a.

<p>PBMC isolated from Egyptians with chronic or resolved HCV infection were stimulated in triplicates with two sets of seven pooled overlapping 15-mer HCV genotype 1b, and genotype 4a peptide antigens (E2 through M) for 16 h as described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0101264#s2" target="_blank">Subjects and Methods</a> section. The total IFNγSFC recorded for each pool is shown for both genotypes. The total number of SFC for all responding donors to GT-4a pools was correlated with those from GT-1b in <b>Panel</b> (<b>A</b>) while that of resolved and chronic subjects are shown in <b>Panels</b> (<b>B</b>) and (<b>C</b>), respectively.</p

Demographic, clinical and laboratory characteristics of the study subjects.

<p>The subjects were classified as responders and non responders as defined in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0101264#s2" target="_blank">Subjects and Methods</a> section. Specifically, responders and non-responders are those individuals who elicited or failed to elicit a positive HCV-specific IFNγ response in the ELISpot assay to one to fourteen HCV G-1b, and 4a overlapping 15-mer peptide pools, respectively. Ten healthy subjects with no known exposure to HCV served as a control group.</p><p>*Mean ± SD.</p