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

ABSTRACT: The symptoms of infectious diarrheal disease are mediated by a combination of a pathogen's virulence factors and the host immune system. 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 to what extent the bacteria are responsible for the diarrheal symptoms via intestinal cell necrosis versus immune cell initiated 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 response to C. jejuni. Pigs were chosen due to the anatomical similarity between the porcine and the human intestine. We found that the abundance of neutrophil related proteins increased in the intestinal lumen during C. jejuni infection, including proteins related to neutrophil migration (neutrophil elastase and MMP9), actin reorganization (Arp2/3), and antimicrobial proteins (lipocalin-2, myeloperoxidase, S100A8, and S100A9). The appearance of neutrophil proteins also corresponded with increases of the inflammatory cytokines IL-8 and TNF-α. 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 neutrophils are the predominant cell type responding to C. jejuni infection. We propose that this model can be used as a platform to study the early immune events during infection with intestinal pathogens.

SUBMITTER: Negretti NM

PROVIDER: S-EPMC7524355 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description: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-a. 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.

Project description:Campylobacter jejuni is a major cause of bacterial foodborne illness in humans worldwide. Bacterial entry into a host eukaryotic cell involves the initial steps of adherence and invasion, which generally activate several cell-signaling pathways that induce the activation of innate defense systems, which leads to the release of proinflammatory cytokines and induction of apoptosis. Recent studies have reported that the unfolded protein response (UPR), a system to clear unfolded proteins from the endoplasmic reticulum (ER), also participates in the activation of cellular defense mechanisms in response to bacterial infection. However, no study has yet investigated the role of UPR in C. jejuni infection. Hence, the aim of this study was to deduce the role of UPR signaling via induction of ER stress in the process of C. jejuni infection. The results suggest that C. jejuni infection suppresses global protein translation. Also, 12 h of C. jejuni infection induced activation of the eIF2α pathway and expression of the transcription factor CHOP. Interestingly, bacterial invasion was facilitated by knockdown of UPR-associated signaling factors and treatment with the ER stress inducers, thapsigargin and tunicamycin, decreased the invasive ability of C. jejuni. An investigation into the mechanism of UPR-mediated inhibition of C. jejuni invasion showed that UPR signaling did not affect bacterial adhesion to or survival in the host cells. Further, Salmonella Enteritidis or FITC-dextran intake were not regulated by UPR signaling. These results indicated that the effect of UPR on intracellular intake was specifically found in C. jejuni infection. These findings are the first to describe the role of UPR in C. jejuni infection and revealed the participation of a new signaling pathway in C. jejuni invasion. UPR signaling is involved in defense against the early step of C. jejuni invasion and thus presents a potential therapeutic target for the treatment of C. jejuni infection.

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

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