AUTHOR=Lee Jun Bong , Kim Se Kye , Han Dalmuri , Yoon Jang Won 

TITLE=Mutating both relA and spoT of enteropathogenic Escherichia coli E2348/69 attenuates its virulence and induces interleukin 6 in vivo

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1121715

DOI=10.3389/fmicb.2023.1121715

ISSN=1664-302X

ABSTRACT=<p>Here, we report for the first time that disrupting both <italic>relA</italic> and <italic>spoT</italic> genes in enteropathogenic <italic>Escherichia coli</italic> E2348/69 can attenuate its virulence and significantly induce interleukin 6 (IL-6) <italic>in vivo</italic>. Our experimental analyses demonstrated that an E2348/69 Δ<italic>relA</italic>Δ<italic>spoT</italic> double mutant strain derepressed the expression of type IV bundle forming pilus (BFP) and repressed the expression of glutamate decarboxylase (GAD) and locus of enterocyte effacement (LEE). Whole genome-scale transcriptomic analysis revealed that 1,564 EPEC genes were differentially expressed in the Δ<italic>relA</italic>Δ<italic>spoT</italic> double mutant strain (cut-off &gt; two-fold). Such depletion of <italic>relA</italic> and <italic>spoT</italic> attenuated the virulence of E2348/69 in a <italic>Caenorhabditis elegans</italic> infection model. Surprisingly, IL-6 was highly induced in porcine macrophages infected with the Δ<italic>relA</italic>Δ<italic>spoT</italic> double mutant strain compared to those with its wildtype strain. Coinciding with these <italic>in vitro</italic> results, <italic>in vivo</italic> murine peritoneal challenge assays showed high increase of IL-6 and improved bacterial clearance in response to infection by the Δ<italic>relA</italic>Δ<italic>spoT</italic> double mutant strain. Taken together, our data suggest that <italic>relA</italic> and <italic>spoT</italic> play an essential role in regulating biological processes during EPEC pathogenesis and that their depletion can affect host immune responses by inducing IL-6.</p>