Investigating the potential role of intimin/invasin in Aeromonas hydrophila virulence in Labeo rohita: a host-microbe interaction study

Aeromonas hydrophila is a primary bacterial pathogen affecting freshwater fish, including Labeo rohita (rohu), leading to significant losses in aquaculture. This study investigates the probable role of intimin/invasin, known virulence factors in several bacterial pathogens, in the pathogenesis of A. hydrophila in L. rohita. Using an in-silico approach, we explore the genetic and structural features of these proteins to predict their potential function in facilitating infection. We analysed the distribution of invasin and intimin across 53 A. hydrophila genomes and examined their physicochemical properties, including molecular weight and stability. Additionally, we evaluated the secondary structures to understand their functional roles in host-pathogen interactions. Using homology-based modelling, we generated 3D (tertiary) structures of invasin and intimin and selected the most suitable models for in silico docking experiments with all eight Rohu (Labeo rohita) {beta}-integrins-a crucial step in understanding their interactions with the fish (Rohu) host cells. Due to the unavailability of the crystal structure of Rohu {beta}-integrins, we performed homology-based modelling prior to the docking experiments. Our findings reveal that invasin and intimin are present in only 6 of the 53 A. hydrophila strains examined, primarily in highly virulent strains previously reported. Notably, invasin lacks disulfide bonds and beta turns. 3D modelling indicates a significant binding affinity of invasin with all human {beta}-integrins, suggesting a critical role in host-pathogen interactions.