Campylobacter jejuni is a major cause of human intestinal illness worldwide, with an annual prevalence of over a million cases in the US. Although the acute stage of C. jejuni infection is characterized by CXCL8- mediated mucosal recruitment, activation, and transepithelial migration of polymorphonuclear neutrophils (PMNs) into the intestinal lumen, the interactions of PMNs with C. jejuni are incompletely understood. This is attributable to a lack of animal model that recapitulates acute C. jejuni intestinal infection and disease. PMNs can exert bacterial killing by releasing their nuclear DNA and antimicrobial effector molecules into the extracellular environment, so called neutrophil extracellular trap (NET). A membrane-associated DNaseI-like nuclease that causes double-strand DNA breaks is found in several clinically-important intestinal bacterial pathogens including C. jejuni. Treatment of C. jejuni with bile acid deoxycholate (DOC) releases the membrane-associated nuclease, while also enhancing epithelial cell invasion and CXCL8 production. Given that PMNs are critical to host innate defense in acute C. jejuni infection, and DOC-mediated release of C. jejuni nuclease can promote infection and inflammation, relevant animal models are critically needed to determine whether or not the nuclease of C. jejuni also mediates resistance to extracellular killing in NET and contributes to acute intestinal disease. We hypothesize that the release of C. jejuni membrane-associated nuclease by intestinal DOC contributes to disease by mediating resistance to bacterial killing in NET. We will test our hypothesis in 2 Specific Aims:
Aim 1 will determine the survival kinetics and PMN association of control and DOC-treated wild type C. jejuni and isogenic nuclease mutant strains incubated with PMNs in vitro.
Aim 2 will determine the kinetics of lesion development, survival, and PMN association of each C. jejuni strain in marmosets and fetal intestinal marmoset xenografts models. The inhibition of NET/rescue of nuclease mutant by recombinant nuclease, and inhibition of wild type phenotype by anti-nuclease antibodies also will be determined. The novel marmoset models of C. jejuni intestinal infection will provide tools necessary for hypothesis-driven analysis of a broadly conserved bacterial nuclease in resistance against host innate defense during acute intestinal infection by bacterial pathogens of major clinical importance.
Campylobacter jejuni is one of the leading causes of food- and water-borne human intestinal illness worldwide, with an estimated 2 million cases in the United States each year. Although polymorphonuclear neutrophils (PMNs) are critical components of the early response and resolution of intestinal infection caused by C. jejuni, little is known about their contribution to elimination of the bacteria and the significance of a nuclease toxin produced by C. jejuni in resistance against PMNs. This new exploratory research project will evaluate C. jejuni strains that have intact or altered production of nuclease toxin during co-incubation with human and mouse PMNs in vitro and in vivo in the context of acute intestinal infection of marmoset monkeys. It is expected that these model systems of acute bacterial intestinal infection will allow the development of more effective vaccines and therapeutic approaches for control of intestinal bacterial diseases of major clinical importance.
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