Investigating the pro-inflammatory role of a secreted protein MbovP537 from Mycoplasma bovis: Potential as a diagnostic marker

Mycoplasma bovis causes significant economic losses in cattle production, yet its pathogenic mechanisms remain incompletely understood. In this study, we characterize MbovP537 as a novel virulence factor and diagnostic marker for M. bovis. Bioinformatic analysis confirmed its identity as a secreted aromatic cluster surface protein (296 aa) with high antigenicity (VaxiJen score: 1.45). Recombinant MbovP537 (rMbovP537) exhibited strong immunogenicity in indirect ELISA, demonstrating 93.3 % sensitivity and 96.7 % specificity (AUC = 0.95) in detecting natural infections in cattle. Functional analysis revealed that deletion of MbovP537 abolished bacterial adhesion (5.6-fold reduction vs. wild-type, P < 0.001) without affecting growth, while attenuating proinflammatory responses (P < 0.001) in BoMac cells. Complementation partially restored both adhesion and inflammation. Crucially, endotoxin-free rMbovP537 directly triggered dose-dependent upregulation of IL-1β, IL-6, and IL-8 (P < 0.001 at 10 μg/mL), In contrast, the anti-inflammatory cytokines IL-4 and IL-10 were not significantly affected. These results indicated that MbovP537 may be essential for host colonization and immunopathology, while its diagnostic performance supports its potential applications in serological testing.