Viral vectored hepatitis C virus vaccines generate pan-genotypic T cell responses to conserved subdominant epitopes. Issue 32 (6th July 2020)

• Record Type: Journal Article
• Authors: Donnison, Timothy; von Delft, Annette; Brown, Anthony; Swadling, Leo; Hutchings, Claire; Hanke, Tomáš; Chinnakannan, Senthil; Barnes, Eleanor
• Is Part Of: Vaccine. Volume 38:Issue 32(2020)
• Page Start: 5036
• Page End: 5048
• Publication Date: 2020-07-06
• Subjects: Universal HCV vaccine -- Adenovirus -- Conserved sequence -- Cross-reactive -- Invariant chain; Vaccines -- Periodicals; 615.372
• DOI: 10.1016/j.vaccine.2020.05.042
• Languages: English
• ISSNs: 0264-410X

Abstract

Highlights: Conserved segment HCV vaccines induce high magnitude CD4 + and CD8 + T cell responses in mice. Conserved segment HCV vaccines are as immunogenic as the gt1b HCV vaccine that was in human trials. Conserved segment HCV vaccine induced T cells target highly conserved epitopes across subtypes. These highly conserved epitopes are associated with spontaneous HCV resolution in humans. Adding the truncated shark invariant chain to the HCV immunogen increases the T cell response. Abstract: Background: Viral genetic variability presents a major challenge to the development of a prophylactic hepatitis C virus (HCV) vaccine. A promising HCV vaccine using chimpanzee adenoviral vectors (ChAd) encoding a genotype (gt) 1b non-structural protein (ChAd-Gt1b-NS) generated high magnitude T cell responses. However, these T cells showed reduced cross-recognition of dominant epitope variants and the vaccine has recently been shown to be ineffective at preventing chronic HCV. To address the challenge of viral diversity, we developed ChAd vaccines encoding HCV genomic sequences that are conserved between all major HCV genotypes and adjuvanted by truncated shark invariant chain (sIitr ). Methods: Age-matched female mice were immunised intramuscularly with ChAd (10 8 infectious units) encoding gt-1 and -3 (ChAd-Gt1/3) or gt-1 to -6 (ChAd-Gt1-6) conserved segments spanning the HCV proteome, or gt-1b (ChAd-Gt1b-NS control), with immunogenicity assessed 14-days post-vaccination. Results: Conserved segment vaccines, ChAd-Gt1/3 and ChAd-Gt1-6, generated high-magnitude, broad, and functional CD4 + and CD8 + T cell responses. Compared to the ChAd-Gt1b-NS vaccine, these vaccines generated significantly greater responses against conserved non-gt-1 antigens, including conserved subdominant epitopes that were not targeted by ChAd-Gt1b-NS. Epitopes targeted by the conserved segment HCV vaccine induced T cells, displayed 96.6% mean sequence homology between all HCV subtypes (100% sequence homology for the majority of genotype-1, -2, -4 sequences and 94% sequence homology for gt-3, -6, -7, and -8) in contrast to 85.1% mean sequence homology for epitopes targeted by ChAd-Gt1b-NS induced T cells. The addition of truncated shark invariant chain (sIitr ) increased the magnitude, breadth, and cross-reactivity of the T cell response. Conclusions: We have demonstrated that genetically adjuvanted ChAd vectored HCV T cell vaccines encoding genetic sequences conserved between genotypes are immunogenic, activating T cells that target subdominant conserved HCV epitopes. These pre-clinical studies support the use of conserved segment HCV T cell vaccines in human clinical trials.