# Viral diversity influences T-cell responses to enteric human adenoviruses F40 and F41

## TL;DR

The study explores how T-cell responses to human adenoviruses F40 and F41 are influenced by viral diversity and MHC binding of viral peptides.

## Contribution

The study identifies conserved and genotype-specific MHC Class I epitopes in HAdV-F40 and F41, offering insights for vaccine design.

## Key findings

- Multiple predicted Class I epitopes were found shared between HAdV species C and F, and some unique to species F.
- IFN-γ and IL-2 responses to HAdV-F were observed in healthy donors from the UK.
- 11 out of 16 F41 hexon peptides elicited IFN-γ responses in healthy donor PBMC.

## Abstract

Background: Human enteric species F adenoviruses are a leading cause of diarrhoea-associated paediatric morbidity and mortality worldwide. The cellular immune response (antigen-specific cytotoxic T cells and secreted cytokines) to human adenovirus (HAdV) infection is known to ameliorate symptoms and is critical for viral clearance. We hypothesized that the capsid proteins (hexon and penton) of HAdV-F40 and 41 (F40, F41) are evolving to escape cellular immune responses. Major histocompatibility complex (MHC) binding of viral peptides is a key step in the presentation of peptide–MHC complexes which activate the T-cell receptor and the cytotoxic T-cell response. Methods: Using global HAdV genomic data, we predicted MHC–peptide binding within the hexon and penton proteins of F40 and F41. We focused on MHC Class I alleles common in the UK and Kenya and identified predicted MHC Class I epitopes. Eight predicted epitope pairs from the F41 hexon were synthesized as 15-mer peptides, comparing the wildtype (1970 F41 reference) to the variant (2019–22) sequences. Cellular interferon gamma (IFN-γ) responses to these epitopes were measured in healthy donors using FluoroSpot assays. Results: We identified multiple predicted Class I epitopes shared between HAdV species C and F, but also unique to species F, and epitopes unique to each genotype. We show that IFN-γ and IL-2 (interleukin 2) peripheral blood mononuclear cell (PBMC) responses to HAdV-F are ubiquitous among healthy adult donors from Cambridge, UK. Among predicted Class I epitopes within the F41 hexon, 11/16 peptides elicited donor positive IFN-γ responses from healthy donor PBMC (at least one epitope from seven out of eight peptide pairs). Conclusions: The hexon and penton proteins of HAdV-F-40 and F41 are predicted to contain a number of genotype-specific, but conserved, Class I epitopes which could be used to inform future vaccine design. Using the hexon of F41 as a case study, we show that predicted T-cell epitopes in emergent strains are able to elicit an inflammatory cytokine response from healthy donor PBMC. The role of T-cell recognition in driving enteric adenovirus evolution deserves further consideration.