Design of a multi-epitope vaccine against intestinal parasites associated with colorectal cancer using immunoinformatics approaches

The increasing prevalence of gastrointestinal infections caused by Cryptosporidium parvum and Schistosoma mansoni, coupled with the lack of definitive treatments, underscores the need for vaccine development to prevent infection-related cancers. Using experimentally validated epitopes for vaccine development enhances confidence in inducing strong and durable immune responses compared to predicted epitopes, which require lab validation. In this study, we employed a unique computational strategy using 197 experimentally validated epitopes of C. parvum and S. mansoni obtained from the IEDB database. After applying homology filters against human proteome and microbiome sequences and conducting HLA population coverage analysis, we chose seven cytotoxic T lymphocyte (CTL), seven helper T cell (HTL), and five B-cell epitopes. These were combined with an RpfE adjuvant and appropriate linkers to design a highly immunogenic chimeric antigen with broad global coverage, optimized for stability, solubility, and manufacturability. Molecular docking revealed strong binding affinities of CTL and HTL epitopes to their respective HLA alleles. Immune simulations demonstrated the multi-epitope antigen's ability to elicit both innate and adaptive immune responses. Docking of the vaccine construct with immune receptors (TLR2-TLR1 and TLR4-MD2) yielded significant scores of - 179.8 ± 4.5 and - 191.5 ± 3.4 kcal/mol, respectively. Molecular dynamics simulations verified the structural stability of vaccine-receptor complexes, while binding free energy calculations reinforced their strong affinities. Finally, in silico cloning validated the vaccine's potential for efficient E. coli expression. These computational findings support the construct as a promising vaccine candidate against C. parvum and S. mansoni, warranting further experimental validation.