Bioinformatics analysis reveals four major hexon variants of human adenovirus type-3 (HAdV-3) as the potential strains for development of vaccine and siRNA-based therapeutics against HAdV-3 respiratory infections

Human adenovirus type 3 (HAdV-3) encompasses 15–87% of all adenoviral respiratory infections. The significant morbidity and mortality, especially among the neonates and immunosuppressed patients, demand the need for a vaccine or a targeted antiviral against this type. However, due to the existence of multiple hexon variants (3Hv-1 to 3Hv-25), the selection of vaccine strains of HAdV-3 is challenging. This study was designed to evaluate HAdV-3 hexon variants for the selection of potential vaccine candidates and the use of hexon gene as a target for designing siRNA that can be used as a therapy. Based on the data of worldwide distribution, duration of circulation, co-circulation and their percentage among all the variants, 3Hv-1 to 3Hv-4 were categorized as the major hexon variants. Phylogenetic analysis and the percentage of homology in the hypervariable regions followed by multi-sequence alignment, zPicture analysis and restriction enzyme analysis were carried out. In the phylogram, the variants were arranged in different clusters. The HVR encoding regions of hexon of 3Hv-1 to 3Hv-4 showed 16 point mutations resulting in 12 amino acids substitutions. The homology in HVRs was 81.81–100%. Therefore, the major hexon variants are substantially different from each other which justifies their inclusion as the potential vaccine candidates. Interestingly, despite the significant differences in the DNA sequence, there were many conserved areas in the HVRs, and we have designed functional siRNAs form those locations. We have also designed immunogenic vaccine peptide epitopes from the hexon protein using bioinformatics prediction tool. We hope that our developed siRNAs and immunogenic vaccine peptide epitopes could be used in the future development of siRNA-based therapy and designing a vaccine against HAdV-3.