Immunoinformatics analysis and evaluation of recombinant chimeric triple antigen toxoid (r-HAB) against Staphylococcus aureus toxaemia in mouse model

Staphylococcus aureus is a serious pathogen unleashing its virulence through several classes of exotoxins such as hemolysins and enterotoxins. In this study, we designed a novel multi-antigen subunit vaccine which can induce innate, humoral and cellular immune responses. Alpha hemolysin, enterotoxins A and B were selected as protective antigens for combining into a triple antigen chimeric protein (HAB). Immunoinformatics analysis predicted HAB protein as a suitable vaccine candidate for inducing both humoral and cellular immune responses. Tertiary structure of the HAB protein was predicted and validated through computational approaches. Docking studies were performed between the HAB protein and mice TLR2 receptor. Furthermore, we constructed and generated recombinant HAB (r-HAB) protein in E. coli and studied its toxicity, immunogenicity and protective efficacy in a mouse model. Triple antigen chimeric protein (r-HAB) was found to be highly immunogenic in mouse as the anti-r-HAB hyperimmune serum was strongly reactive to all three native exotoxins on Western blot. In vitro toxin neutralization assay using anti-r-HAB antibodies demonstrated > 75% neutralization of toxins on RAW 264.7 cell line. Active immunization with r-HAB toxoid gave similar to 83% protection against 2 x lethal dosage of secreted exotoxins. The protection was mediated by induction of strong antibody responses that neutralized the toxins. Passive immunization with anti-r-HAB antibodies gave similar to 50% protection from lethal challenge. In conclusion, in vitro and in vivo testing of r-HAB found the molecule to be nontoxic, highly immunogenic and induced excellent protection towards native toxins in actively immunized and partial protection to passively immunized mice groups.

Automated summary

A novel multi-antigen subunit vaccine was designed, incorporating three protective antigens and validated through immunoinformatics analysis and computational approaches. The recombinant HAB protein (r-HAB) showed high immunogenicity in mice, inducing strong antibody responses and excellent protection against native toxins.