Ibler, A. E. | Search bioRxiv

bioRxiv2025

Typhoid toxin of Salmonella enterica induces ISG15 response mediating host cell survival and bacterial dissemination

The typhoid toxin is a secreted virulence factor of typhoidal serovars of the bacterial pathogen Salmonella enterica implicated in typhoid fever and chronic infections. The toxin causes a DNA damage response in human cells, characterised by cell-cycle arrest and cellular distension, resulting in cellular senescence and increased bacterial burden. To better understand host responses to typhoid toxin, we performed a transcriptomic analysis of intoxicated host cells and found that the toxin induced expression of genes relating to the type-I interferon response, including the ubiquitin-like protein ISG15. ISG15 was upregulated in a STING-dependent manner, reduced bacterial burden, and was found to be critical to host cell survival in response to the typhoid toxin and purified interferon. This highlights ISG15 as an important component of the host cell defence to the typhoid toxin.

microbiology↗

bioRxiv2022

Typhoid toxin hijacks Wnt5a to potentiate TGFβ-mediated senescence and Salmonella infection

Damage to our genome causes acute senescence in mammalian cells, which undergo growth arrest and release a secretome that elicits cell cycle arrest in bystander cells through the senescence-associated secretory phenotype (SASP). Thus, acute senescence is a powerful tumour suppressor. Salmonella enterica hijacks senescence through its typhoid toxin, which usurps unidentified factors in the stress secretome of senescent cells to mediate intracellular infections. Here, transcriptomics of toxin-induced senescent cells (txSCs) and proteomics of their secretome identified secreted ligands that activate the TGF{beta} pathway through SMAD transcription factors. The ligand Wnt5a established a self-amplifying positive feedback loop driving TGF{beta} signalling, which enforced autocrine senescence in txSCs and paracrine senescence in naive bystander cells by activation of DDRs. Wnt5a and GDF15 increased host cell susceptibility to infection. The study reveals how an innate defence against cancer is co-opted by a bacterial pathogen to cause widespread damage and mediate infections.

cell biology↗