Staphylococcal Enterotoxins Modulate Platelet Response During Storage of Platelet Concentrates and Impair Silkworm...

Platelet concentrates (PCs) are used to treat patients with platelet deficiencies. PCs are stored at 20-24 °C under agitation for up to 7 days to maintain platelet functionality, but these conditions are amenable for proliferation of contaminants such as Staphylococcus aureus, posing a risk for transfusion-transmitted infections. We investigated the contribution of staphylococcal enterotoxins (SEs) type G (SEG) and type H (SEH) to platelet activation, cytokine release, microRNA (miRNA) modulation, and in vivo virulence. PCs were inoculated with wildtype S. aureus CBS2016-05 or SE-deficient mutants (Δseg, Δseh, ΔΔsegh) and monitored during storage. Flow cytometry revealed progressive elevation of platelet activation markers CD62P and Annexin V in contaminated PCs, with significantly higher expression in wildtype compared to SE-mutant strains. Cytokine profiling demonstrated that SEs modulate pro- and anti-inflammatory mediators, notably CCL2, TGF-β1, IFN-γ, and TNF-α, implicating SEG in their regulation. Next-generation sequencing and RT-qPCR validation identified transient induction of immune-related microRNAs miR-98-5p, miR-146a-5p, miR-221-3p, miR-320a-3p, with SE-dependent expression patterns. In a silkworm infection model, wildtype S. aureus-contaminated PCs exhibited significantly higher lethality than SE-deficient strains, confirming toxin-mediated virulence. Collectively, these findings reveal that SEs exacerbate platelet activation and immune dysregulation during storage, enhancing bacterial pathogenicity. This study identifies platelet-derived cytokine and miRNA signatures as potential biomarkers of bacterial contamination and underscores the need to mitigate SE-driven platelet dysfunction to improve transfusion safety.