Structural and functional studies of OmpA from salmonella enterica typhimurium: A novel B-cell immunomodulator and therapeutic target

Abstract

Salmonella enterica serovar Typhimurium is a Gram-negative bacterium that causes gastrointestinal infections and is associated with rising antibiotic resistance worldwide. Increasing antibiotic resistance necessitates the exploration of alternative therapeutic approaches that target the virulence mechanisms of Salmonella. Among these, outer membrane proteins (OMPs) and outer membrane vesicles (OMVs) play a crucial role in mediating host-pathogen interaction, immune invasion, and pathogenesis. Notably, OmpA plays a significant role in these processes; however, its structure-function relationship and potential for immunomodulation are still not fully understood. To investigate the structural analysis of OmpA, we initially conducted a computational analysis that revealed a conserved β-barrel architecture of OmpA within the Enterobacteriaceae family. Furthermore, due to its β-sheet-rich structure, recombinant OmpA tends to form inclusion bodies during overexpression. To mitigate this, we used a high pH buffer for solubilization followed by refolding with LDAO. This approach effectively preserved the protein’s native structure, which was confirmed through CD spectroscopy and tryptophan fluorometry. Additionally, immunoinformatic analysis identified multiple conserved B- and T-cell epitopes, further supporting OmpA's potential as a subunit vaccine.