Synergistic Immunoenhancement of Recombinant Pbp2a Vaccine Candidate by Biogenic Selenium Nanoparticles and Mf59 Against Methicillin-Resistant Staphylococcus Aureus Publisher Pubmed



Daneshpajooh Rahmani M ; Yazdi MH ; Haghighat S ; Zarrinpanah T
Source: Current Microbiology Published:2026

Abstract

Methicillin-resistant Staphylococcus aureus remains a major global health concern due to its resistance to β-lactam and multiple other classes of antibiotics. Herein, we evaluated a recombinant penicillin-binding protein 2a (r-PBP2a) vaccine candidate formulated with biogenic selenium nanoparticles (SeNPs) and the MF59 adjuvant. While r-PBP2a was purified under denaturing conditions and subsequently refolded for use as an immunogen, biogenic selenium nanoparticles were prepared and characterized in terms of morphology, charge, and safety. Female BALB/c mice were assigned to experimental groups and immunized subcutaneously with formulations containing r-PBP2a+ SeNPs+ MF59, or r-PBP2a with MF59 alone. Control mice received sterile PBS or SeNPs + MF59. Booster vaccinations were performed on days 14 and 28. Serum samples were collected two weeks after final immunization for immunological evaluations, including ELISA-based quantification of total IgG, IgG1, and IgG2a, as well as cytokine levels (IFN-γ, IL-4, IL-12). Opsonophagocytic activity and protective efficacy against a lethal challenge of Methicillin-resistant Staphylococcus aureus COL strain (5 × 10⁸ CFU) were also evaluated. The r-PBP2a + MF59 + SeNPs group exhibited significantly higher IgG response (p < 0.0001 at all dilutions), enhanced cytokine secretion (IFN-γ: 125.1 pg/mL, IL-12: 21.8 pg/mL, IL-4: 20.3 pg/mL; all p < 0.0001 vs. controls), and superior opsonophagocytic activity (53.5% killing at 1:2 serum dilution) compared to r-PBP2a + MF59 and control groups. Following challenge, survival reached 78.5% in the r-PBP2a + MF59 + SeNPs group, 64.2% in r-PBP2a + MF59, and 0% in the control groups (p < 0.0001). Bacterial loads in liver, spleen, and kidney were significantly reduced in the r-PBP2a + MF59 + SeNPs group compared to control groups (p < 0.0001). Ultimately, these results demonstrate that incorporation of SeNPs into MF59-adjuvanted vaccines significantly augments both humoral and cellular immunity, providing enhanced protection against Methicillin-resistant Staphylococcus aureus infection in mice. This formulation makes a promising vaccine candidate for further preclinical studies; however, more studies are still required. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2026.