Peptidase PepP is a novel virulence factor of Campylobacter jejuni contributing to murine campylobacteriosis

Markus M Heimesaat,Anna-Maria Schmidt,Soraya Mousavi,Ulrike Escher,Nicole Tegtmeyer,Silja Wessler,Gabriele Gadermaier,Peter Briza,Dirk Hofreuter,Stefan Bereswill,Steffen Backert

doi:10.1080/19490976.2020.1770017

Abstract

ABSTRACT Mechanisms of host–pathogen interactions resulting in immunopathological responses upon human Campylobacter jejuni infection are not completely understood, but the recent availability of murine infection models mimicking key features of campylobacteriosis helps solving this dilemma. During a screen for proteases expressed by C. jejuni, we identified a peptidase of the M24 family as a potential novel virulence factor, which was named PepP. The gene is strongly conserved in various Campylobacter species. A constructed deletion mutant ΔpepP of C. jejuni strain 81–176 grew as efficiently compared to isogenic wild-type (WT) or pepP complemented bacteria. To shed light on the potential role of this protease in mediating immunopathological responses in the mammalian host, we perorally challenged microbiota-depleted IL-10−/- mice with these strains. All strains stably colonized the murine gastrointestinal tract with comparably high loads. Remarkably, pepP deficiency was associated with less severe induced malaise, with less distinct apoptotic and innate immune cell responses, but also with more pronounced proliferative/regenerative epithelial cell responses in the large intestine at d6post-infection. Furthermore, pro-inflammatory mediators were lower in the colon, ileum, and mesenteric lymph nodes of mice that had been challenged with the ΔpepP mutant compared to the WT or pepP complemented strains. This also held true for extra-intestinal organs including liver, kidneys, and lungs, and, strikingly, to systemic compartments. Taken together, protease PepP is a novel virulence determinant involved in mediating campylobacteriosis. The finding that apoptosis in the colon is significantly diminished in mice infected with the pepP mutant highlights the epithelial layer as the first and main target of PepP in the intestine.

Highlights

Foodborne diseases caused by Campylobacter, Salmonella, pathogenic Escherichia coli, and other enteropathogenic bacterial species represent signifi cant public health burdens, responsible for high rates of morbidity and mortality, especially in children.[1]
To identify the major proteases produced by C. jejuni, total bacterial lysate of strain 81–176 was separated on a preparative SDS-PAGE gel con taining embedded casein
Campylobacter jejuni infections are associated with strong inflammatory responses resulting in tissue damage within the human gut, which is mainly attrib uted to bacteria invading epithelial cells and traversing the intestinal barrier upon infection

Summary

Introduction

Foodborne diseases caused by Campylobacter, Salmonella, pathogenic Escherichia coli, and other enteropathogenic bacterial species represent signifi cant public health burdens, responsible for high rates of morbidity and mortality, especially in children.[1]. The patho gen enters the food chain via contaminated animal products, and consumption of contaminated poultry meat is a major recognized risk factor.[3] Typically, following oral uptake in humans, C. jejuni colonizes the mucus layer of the large intestine. While the infection can remain asymptomatic, possibly related to the immune status and low-dose or regular exposure,[4] the majority of sporadic exposure inci dents result in symptoms ranging from mild, selflimiting diarrhea to severe inflammatory bloody diar rhea, often accompanied by fever and abdominal pain This clinical manifestation of campylobacterio sis is practically indistinguishable from salmonellosis.[5] Infections with C. jejuni are potentially associated with serious sequelae, including Guillain–Barré syn drome, irritable bowel disease, and reactive arthritis.[6]

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