Strain-dependent immunomodulatory effects of probiotics in murine vaginal staphylococcosis: modulation of TLR2 and cytokine responses in macrophages

This study evaluated the strain-dependent immunomodulatory effects of lactic acid bacteria, specifically Lacticaseibacillus casei IMV B-7280 and Lactobacillus acidophilus IMV B-7279, as well as a multi-strain probiotic composition comprising L. casei IMV B-7280, Bifidobacterium animalis IMV B-7285, and B.animalis IMV B-7286, in a murine model of vaginal infection induced by Staphylococcus aureus 8325–4. Probiotic administration in Staphylococcus -infected mice promoted resolution of clinical signs of the infectious-inflammatory process and was associated with strain-specific clearance of S. aureus 8325–4 from the vagina compartment and peritoneal macrophages (PEMs). This was accompanied by the downregulation of TLR2, but not TLR4, expression in PEMs. These probiotics differentially modulated the cytokine profile and the functional activity of PEMs at the systemic level. Among all tested probiotics, L. casei IMV B-7280 was the most effective, normalizing the production of tumor necrosis factor alpha (TNF-α), respiratory burst, and phagocytic activity of PEMs. Furthermore, it significantly enhanced the production of interleukin-12 (IL-12) while reducing the excessive production of interleukin-6 (IL-6) and interleukin-10 (IL-10) by PEMs. These changes correlated with the restoration of the functional reserve of PEMs and more effective clearance of the pathogen. The multi-strain composition demonstrated moderate effects, whereas L. acidophilus IMV B-7279 showed limited efficacy. Thus, all the tested probiotics reduced the S. aureus 8325–4 burden within the vaginal compartment and PEMs with varying efficacy and alleviated the course of the infection. This therapeutic effect was associated with the downregulation of TLR2 expression in PEMs and characterized by the strain-specific modulation of the cytokine profile (TNF-α, IL-6, IL-10, and IL-12) and functional activity of PEMs. These findings highlight the importance of strain selection for targeted immunomodulation and support the development of personalized immunobiotic strategies.