Using omics to characterize the role of ArtAB toxin in Salmonella pathogenesis

Salmonella is a major cause of foodborne illness, hospitalization, and death worldwide. This high-priority pathogen produces multiple virulence factors that enable it to evade host immune defenses. Among these are AB₅ toxins, a family of multi-subunit secreted proteins known to be virulence factors in other Gram-negative bacteria. AB₅ toxins have been identified in both typhoidal and non-typhoidal Salmonella (NTS) serovars; however, their molecular role in pathogenesis in NTS remains poorly understood. We have previously purified an AB₅-like toxin, ArtAB, and its B₅ subunit (ArtB) from Salmonella Typhimurium. In this study, we treated Chinese hamster ovary (CHO) cells with ArtAB, ArtB, and other AB₅ toxins to examine cellular morphology, such as cell elongation or clustering. We also performed a cytotoxicity assay with 2-fold dilutions of ArtAB and ArtB on CHO cells. Based on these results, we treated CHO cells with 10 µg/mL of ArtAB and 7.25 µg/mL of ArtB (equimolar concentrations) for 4 hours, followed by mRNA sequencing and whole-cell proteomics to investigate differential gene and protein expression. Preliminary mRNA-seq results indicate that ArtAB significantly alters the expression of genes involved with transcription factors, cell signaling, intracellular transport of biomolecules, metabolism, and extracellular matrix remodeling. In contrast, ArtB behaves similarly to the buffer control (1X PBS + 5% glycerol) and does not significantly modulate gene expression. Proteomics analysis thus far supports these findings. Uniquely, enterotoxin B₅ subunits, such as cholera toxin B (CTB), are known to serve as both vaccine antigens and protein adjuvants. Further defining the cellular signaling pathways induced by these toxins is essential to understanding how they contribute to Salmonella pathogenesis and may lead to the development of more effective therapeutics and vaccines.