Immunoinformatics-based identification of highly conserved cytotoxic T-cell epitopes in polyprotein pp220 of african swine fever virus

Background: High mortality rate of pigs peaked in 2020 due to the re-emergence of a deadly African swine fever virus (ASFV) which has led to transcontinental outbreaks in Europe, reportedly from 2014 to 2019, and in Asia and the Pacific from 2018–2020. Given the huge socioeconomic consequences of the disease, vaccines that will prime the immunity of swine against this pathogen is a dire necessity. Methods: In silico identification and characterization of highly conserved cytotoxic T-cell (CD8+) epitopes derived from one of its structural proteins, pp220, were analyzed. Protein sequences of pp220 were retrieved and clustered to obtain highly conserved sequences. Cross-reactive epitopes were filtered out, and the remaining epitopes were docked with swine leukocyte antigen-1*0401 (SLA-1*0401). Furthermore, the epitope stability was determined by comparing binding energy, dissociation constant, and eigenvalues of the epitopes with the values of positive control, influenza-epitope complex. Results: This study showed that 20 highly conserved epitopes promiscuously bind to two or more SLAs and 9 of which epitopes (ALDLSLIGF, QIYKTLLEY, FLNKSTQAY, IADAINQEF, IINPSITEY, AINTFMYYY, SLYPTQFDY, RSNPGSFYW, and RLDRKHILM) that were validated exhibit potential immunogenicity based on the acceptable binding energy, dissociation constant, and eigenvalues. Conclusion: This study has identified epitopes that show high conservancy, reducing the chance of epitope immune evasion. It is anticipated that the identified epitopes must be further evaluated as a potential immunotherapeutic agent in developing an epitope-based vaccine against ASFV.