Reverse-vaccinology strategy for designing T-cell epitope candidates for Staphylococcus aureus endocarditis vaccine.

Staphylococcus aureus is an opportunistic pathogen causing various inflammatory diseases from skin and tissue local infections, to serious life threatening infections including endocarditis. Experimental models for endocarditis demonstrated that virulence factors of S. aureus, that are very important in infection of heart vegetations, are surface proteins which promote bacterial adherence. Until now, efforts to develop effective vaccines against S. aureus were unsuccessful, partly due to the fact that different vaccine formulations have targeted mainly B-cell immunity. Reverse vaccinology is applied here, in order to identify potential vaccine epitope candidates. The basic epitopes prediction strategy relied on detection of a common antigenic 9-mer epitope meant to be able to stimulate both the B-cell and T-cell mediated immunity. Ten surface exposed proteins were chosen for antigenicity testing. Using a web-based system, five T-cell epitopes corresponding to fibronectin binding protein A (FDFTLSNNV and YVDGYIETI), collagen adhesin (FSINYKTKI), serine-rich adhesin for platelets (LTFDSTNNT) and elastin binding protein (FAMDKSHPE) were selected as potential vaccine candidates. Epitopes sequences were found to be conserved among the different S. aureus genomes screened from NCBI GenBank. In vitro and in vivo immunological tests will be performed in order to validate the suitability of the epitopes for vaccine development.