JIANDONG HUANG, PhD: No financial relationships to disclose
Introduction/Rationale: Staphylococcus aureus is an opportunistic pathogen causing skin, soft tissue, and bloodstream infections, with high incidence in industrialized countries. Rising antibiotic resistance has complicated treatment as resistant strains spread beyond healthcare settings. Traditional vaccine targets include virulence factors such as ClfA and Hla. Recently, the lipoylated E2 subunit of pyruvate dehydrogenase (PDHC) from S. aureus was found to act as an immunosuppressant by blocking macrophage activation. Here, we show that immunization with PDHC confers robust protection against lethal S. aureus challenge in multiple animal models.
Methods: Recombinant PDHC was expressed in E. coli and purified via affinity chromatography. Mice and rabbits were immunized subcutaneously. Antibodies were detected by ELISA. Mice were challenged intravenously, intraperitoneally, or subcutaneously with S. aureus. RNA-seq and flow cytometry were used to assess immune responses.
Results: PDHC is >99% conserved among S. aureus strains and elicits strong humoral and cellular immunity. Vaccination protected against methicillin-sensitive and -resistant strains in multiple murine models. Protection in bloodstream infection did not require antibodies; B cell-deficient mice showed enhanced proinflammatory chemokine expression, indicating reliance on cellular immunity. γδ T cells were essential for bacterial clearance via neutrophil and macrophage activation, with increased Granzyme B expression post-infection. PDHC remained effective in mice with prior S. aureus exposure and formed self-assembling nanoparticulate structures. In rabbits, PDHC reduced skin abscess formation.
Conclusion: PDHC is a highly conserved, serotype-independent vaccine candidate that induces γδ T cell–mediated systemic immunity and protects against diverse S. aureus strains, including MRSA, even in previously exposed hosts.
