A porcine ligated loop model reveals new insight into the host immune response against Campylobacter jejuni

Authors: NEGRETTI, NICHOLAS - Washington State University; YE, YINYIN - Pacific Northwest National Laboratory; MALAVASI, LAIS - Washington State University; POKHAREL, SWECHHA - Washington State University; Huynh, Steven; Noh, Susan; KLIMA, CASSIDY - Canadian Food Inspection Agency; GOURLEY, CHRISTOPHER - Washington State University; RAGLE, CLAUDE - Washington State University; BOSE, SANTANU - Washington State University; Looft, Torey; Parker, Craig; CLAIR, GEREMY - Pacific Northwest National Laboratory; ADKINS, JOSHUA - Pacific Northwest National Laboratory; KONKEL, MICHAEL - Washington State University

Submitted to: Gut Microbes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2020
Publication Date: 9/4/2020
Citation: Negretti, N.M., Ye, Y., Malavasi, L.M., Pokharel, S.M., Huynh, S., Noh, S.M., Klima, C.L., Gourley, C.R., Ragle, C.A., Bose, S., Looft, T.P., Parker, C., Clair, G., Adkins, J.N., Konkel, M.E. 2020. A porcine ligated loop model reveals new insight into the host immune response against Campylobacter jejuni. Gut Microbes. 12(1). Article 1814121. https://doi.org/10.1080/19490976.2020.1814121.
DOI: https://doi.org/10.1080/19490976.2020.1814121

Interpretive Summary: Campylobacter jejuni is the leading bacterial cause of diarrhea worldwide due to its near-ubiquitous zoonotic association with poultry. The initiation of diarrheal disease is a multifactorial process involving the host immune system and the invading pathogen. Understanding the interplay between the host and pathogen is necessary for mitigating the impact of intestinal pathogens on human health. One of the outstanding questions is what factors drive the intestinal inflammation during the development of C. jejuni-mediated disease. Specifically, it is not known the extent to which the bacteria are responsible for the diarrheal symptoms via cell necrosis, or whether there is immune cell recruitment prior to tissue damage. We used a piglet ligated intestinal loop model to study the intestinal environment in response to C. jejuni to determine the stepwise process of inflammation that leads to diarrhea. Pigs were chosen as a modeling system due to the anatomical similarity of the pig intestine to the human intestine, and thus should help us understand the process of human disease. Using immunoassays and proteomic approaches, we found that neutrophils are most likely the predominant cell type recruited to the intestines of C. jejuni infected animals. The appearance of neutrophils also corresponds with increases of both IL-8 and TNF-', which are inflammatory cytokines. Compared to infection with the C. jejuni wild-type strain, infection with the noninvasive C. jejuni mutant resulted in a blunted inflammatory response, with less inflammatory cytokines and neutrophil markers. These findings indicate that intestinal inflammation is driven by C. jejuni virulence, and that resident intestinal cells precipitate the inflammatory response. Using this new disease model, we have developed a platform to study the early immune events during C. jejuni infection.

Technical Abstract: The symptoms of infectious diarrheal disease are mediated by the interplay between the host and pathogen. Campylobacter jejuni is the leading bacterial cause of diarrhea worldwide due to its near-ubiquitous zoonotic association with poultry. One of the outstanding questions is what factors drive the intestinal inflammation during the development of C. jejuni-mediated disease. Specifically, it is not known the extent to which the bacteria are responsible for the diarrheal symptoms via cell necrosis, or whether there is immune cell recruitment prior to tissue damage. To determine the stepwise process of inflammation that leads to diarrhea, we used a piglet ligated intestinal loop model to study the intestinal environment in response to C. jejuni. Pigs were chosen due to the anatomical similarity of the porcine intestine to the human intestine, as the basis of disease modeling is to understand the process of human disease. Using immunoassays and proteomic approaches, we found that neutrophils are most likely the predominant cell type recruited to the intestines of C. jejuni infected animals. In the lumen of the intestine, a number of neutrophil related proteins increased during C. jejuni infection, including proteins related to neutrophil migration (elastase and MMP9), actin reorganization and bacterial uptake (Cdc42, WAVE-2, and Arp2/3), and antimicrobial proteins (lipocalin-2, myeloperoxidase, S100A8, and S100A9). The appearance of neutrophils also corresponds with increases of both IL-8 and TNF-'. Compared to infection with the C. jejuni wild-type strain, infection with the noninvasive C. jejuni 'ciaD mutant resulted in a blunted inflammatory response, with less inflammatory cytokines and neutrophil markers. These findings indicate that intestinal inflammation is driven by C. jejuni virulence, and that resident intestinal cells precipitate the inflammatory response. Using this new disease model, we have developed a platform to study the early immune events during C. jejuni infection.