JOURNAL OF BACTERIOLOGY AND VIROLOGY ISSN:1598-2467(Print) 2093-0429(Online)

Mouse-adapted Helicobacter pylori (H. pylori) strains exhibit distinct abilities to colonize the mouse gastric environment, suggesting that strain-specific genetic factors contribute to host adaptation and immune interaction. This study aimed to find genetic determinants associated with mouse infectivity–based strain differences and to characterize their potential roles in immune modulation using in vitro functional assays. Comparative transcriptomic analyses were performed using microarrays to compare a mouse-infectious H. pylori strain (Hp52) with non- mouse-infectious strains (26695 and J99). Candidate genes were screened based on differential expression patterns associated with mouse infectivity phenotypes. Four genes—HPKB0346, HPKB0407 (acetyl-CoA synthetase), HPKB0424, and HPKB1443 (alanine dehydrogenase, ald)—were selected for further investigation based on their increased expression or strain-specific presence in Hp52. Targeted knockout mutants were generated in the Hp52 using a cross-over PCR and natural transformation. To evaluate immunomodulatory effects in vitro, mouse bone marrow-derived dendritic cells (BMDCs) were stimulated with wild-type or mutant strains, and the expression profiles of cytokines and activation markers were quantified by real-time qRT-PCR. Compared with the wild type, all knockout mutants induced significantly reduced expression of IFN-γ and MHC II in BMDCs. Notably, stimulation with the Δald mutant elicited increases in IL-1β, IL-6, and IL-10 expression indicating a distinct immunomodulatory profile. Collectively, these findings suggest that specific genetic factors identified through mouse infectivity–based screening, particularly ald, are associated with the modulation of dendritic cell responses in vitro and may contribute to host adaptation and immune regulation by H. pylori.