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Chronic hepatitis C viral infection subverts vaccine-induced T-cell immunity in humans.

ABSTRACT:

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Adenoviral vectors encoding hepatitis C virus (HCV) nonstructural (NS) proteins induce multispecific, high-magnitude, durable CD4(+) and CD8(+) T-cell responses in healthy volunteers. We assessed the capacity of these vaccines to induce functional HCV-specific immune responses and determine T-cell cross-reactivity to endogenous virus in patients with chronic HCV infection. HCV genotype 1-infected patients were vaccinated using heterologous adenoviral vectors (ChAd3-NSmut and Ad6-NSmut) encoding HCV NS proteins in a dose escalation, prime-boost regimen, with and without concomitant pegylated interferon-α/ribavirin therapy. Analysis of immune responses ex vivo used human leukocyte antigen class I pentamers, intracellular cytokine staining, and fine mapping in interferon-γ enzyme-linked immunospot assays. Cross-reactivity of T cells with population and endogenous viral variants was determined following viral sequence analysis. Compared to healthy volunteers, the magnitude of HCV-specific T-cell responses following vaccination was markedly reduced. CD8(+) HCV-specific T-cell responses were detected in 15/24 patients at the highest dose, whereas CD4(+) T-cell responses were rarely detectable. Analysis of the host circulating viral sequence showed that T-cell responses were rarely elicited when there was sequence homology between vaccine immunogen and endogenous virus. In contrast, T cells were induced in the context of genetic mismatch between vaccine immunogen and endogenous virus; however, these commonly failed to recognize circulating epitope variants and had a distinct partially functional phenotype. Vaccination was well tolerated but had no significant effect on HCV viral load.

Conclusion

Vaccination with potent HCV adenoviral vectored vaccines fails to restore T-cell immunity except where there is genetic mismatch between vaccine immunogen and endogenous virus; this highlights the major challenge of overcoming T-cell exhaustion in the context of persistent antigen exposure with implications for cancer and other persistent infections.

SUBMITTER: Kelly C

PROVIDER: S-EPMC4842008 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:To determine the relationship between host immunity and the characteristics of viral infection or nucleoside analogues (NAs) themselves in patients with chronic hepatitis B (CHB) receiving NA therapy.Fifty-two hepatitis B envelope antigen (HBeAg) positive CHB patients were enrolled and divided equally into two groups. One group received telbivudine (LDT, 600 mg/d), and the other group received lamivudine (LAM, 100 mg/d). Clinical, virological and immunological parameters were assessed at the baseline and at 4, 12, 24, 36 and 48 wk.Both groups achieved significant hepatitis B virus (HBV) replication inhibition and alanine aminotransferase normalization at 48 wk. At the baseline, compared to healthy controls, CHB patients had a lower circulating CD8 T cell frequency (29.44% ± 11.55% vs 37.17% ± 7.30%, P = 0.03) and higher frequencies of programmed death 1 positive CD8 T cells (PD-1+ CD8 T) (16.48% ± 10.82% vs 7.02% ± 3.62%, P = 0.0001) and CD4+ CD25+ FoxP3+ T regulatory cells (Tregs) (23.64% ± 9.38% vs 13.60% ± 6.06%, P = 0.001). On therapy, at the beginning 24 wk with the levels of hepatitis B virus deoxyribonucleic acid (HBV DNA) and HBeAg declining, the frequencies of PD-1+ CD8 T cells and Treg cells gradually and significantly declined at 12 and 24 wk in both therapy groups. At treatment week 4, patients treated with LDT had a lower frequency of PD-1+ CD8 T cells compared to patients treated with LAM (10.08% ± 6.83% vs 20.51% ± 20.96%, P = 0.02). The frequency of PD-1+ CD8 T cells in all of the CHB patients was significantly correlated with both the HBV DNA level (r = 0.45, P = 0.01) and HBeAg level (r = 0.47, P = 0.01) at treatment week 24, but the frequency of Treg cells was only significantly correlated with the HBeAg level (r = 0.44,P = 0.02). Furthermore, the ability of CD8 T cells to secrete pro-inflammatory cytokines was partially restored after 24 wk of therapy.NA-mediated HBV suppression could down-regulate the production of negative regulators of host immunity during the first 24 wk of therapy and could partially restore the ability of CD8 T cells to secrete pro-inflammatory cytokines. This immune modulating response may be correlated with the levels of both HBV DNA and HBeAg.

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Chronic hepatitis C viral infection subverts vaccine-induced T-cell immunity in humans.

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