Temperature-dependent protease LasB from Aeromonas hydrophila PS-1 contributes to enteritis and pyroptosis-like injury in Pelodiscus sinensis

Temperature can profoundly alter host-pathogen interactions in ectothermic animals and thereby influence the severity of infectious disease. The Chinese soft-shelled turtle (Pelodiscus sinensis), an economically important aquaculture species, is susceptible to bacterial infections, with Aeromonas hydrophila representing a major pathogen. This study investigated the temperature dependence of A. hydrophila virulence in P. sinensis and identified LasB as a temperature-responsive virulence factor that promotes pyroptotic injury in intestinal fibroblast-like cells. Notably, lasB expression varied markedly with temperature and reached its highest level at 35℃. Deletion of lasB attenuated cytotoxicity toward intestinal fibroblast-like cells, as evidenced by reduced cellular damage and lactate dehydrogenase (LDH) release. Transcriptomic profiling further revealed that lasB knockout suppressed infection-induced activation of inflammatory pathways and diminished the upregulation of pyroptosis-related genes, including GSDMA, NLRP3, IL-1β, and IL-18. Consistent with the cellular findings, loss of lasB significantly reduced the pathogenicity of A. hydrophila in P. sinensis, with the strongest attenuation observed at 35℃. These results indicated that LasB played an important role in the pathogenicity of A. hydrophila, and its virulence is closely related to temperature.