Exploratory immunoinformatic and single-donor ex vivo evaluation of methicillin-resistant Staphylococcus aureus virulence-factor peptide combinations in burn-associated bacteraemia: Implications for MRSA vaccine development

This exploratory two-stage study combined immunoinformatic screening with ex vivo peripheral blood mononuclear cell (PBMC) stimulation from one 38-year-old man with a mid-deep dermal burn injury involving 35% total body surface area (TBSA) and confirmed methicillin-resistant Staphylococcus aureus (MRSA) bacteremia. Upstream candidate selection incorporated S. aureus /MRSA sequence matching and conservation screening against a nonredundant S. aureus pangenome comprising 1,038 GenBank genomes, together with antigenicity, predicted safety, and structural accessibility. Four predicted non-toxic, non-allergenic peptides (A1, A2, B, and H) were tested alone and in combinations for 72 h at 5 µg/mL per peptide using five technical replicate wells per condition. One-way ANOVA with Duncan post hoc testing showed that A2-B-H produced the broadest response profile, including higher CD33+CD38+ (+73%, p < 0.01), CD20+ (+42%, p < 0.01), and IL-4 (+37%, p < 0.01). A1-H yielded the highest CD3+CD16+ (+43%, p < 0.05) and TNF-α (+65%, p < 0.05), whereas A2-H produced the highest total IgG (+31%, p < 0.05). The integrated immunological score ranked A2-B-H highest (16.3/20). These findings support A2-B-H as the leading combination for subsequent functional and translational validation.