The Centers for Disease Control and Prevention estimate that every year 1 in 6 Americans suffers from an episode of gastrointestinal infection. Approximately 10% of those may subsequently develop post-infection irritable bowel syndrome (PI-IBS), a three- to four-fold greater risk than unexposed individuals studied over the same time period. The symptoms of PI-IBS can persist up to 8 years after the infection. Campylobacter, a leading cause of bacterial enterocolitis in the U.S. and around the world, has been associated with PI-IBS development. The military population, especially those deployed to Southeast Asia, is particularly at risk for Campylobacter infection. A three- to four-fold increased risk of PI-IBS was seen in the military population as well. Interestingly, presence of psychological stress at the time of infection has been strongly associated with PI-IBS development both in civilian and military populations.Several factors make the study of PI-IBS highly significant and likely to provide mechanistic insights into IBS in general: (i) The de novo onset of symptoms in PI-IBS allows studying its onset, progression, and natural history. (ii) The PI-IBS population is much more homogenous in phenotype than the general IBS population. (iii) Individuals exposed to the same agent, but who do not develop IBS, are excellent controls. Despite the originally published reports of PI-IBS >50 years ago and extensive epidemiological literature, the mechanistic understanding of PI-IBS is lacking. The host epithelium provides the primary site of defense and mediates downstream signaling in response to a pathogenic attack. Campylobacter attaches, invades, and translocates through epithelial cells. Psychological stress and stress hormones can attenuate the epithelial barrier and secretory mechanisms in a sex-dependent manner. Thus, it is plausible that epithelial changes associated with sex and psychological stress creates a milieu for Campylobacter to cause molecular changes that can play a role in subsequent development of PI-IBS. To study this, we plan to develop colonoids from crypts obtained from sigmoid colonic biopsies from human volunteers from both sexes and with or without the presence of chronic psychological stress. In addition to colonocytes, the colonoids contain other specialized cell types (mucin-producing goblet cells and serotonin-producing enteroendocrine cells) and mimic the complex architectural microenvironment seen in a differentiated human epithelial surface. These offer a distinct and novel platform for host environment and studying interactions with the pathogen. Our hypothesis is that human colonoids modeling high-risk patients for PI-IBS have a characteristic molecular and physiological response during acute C. jejuni infection with PI-IBS causing strains. We plan to study C. jejuni infection using strains that are known to cause PI-IBS. To identify molecular targets and pathways associated with C. jejuni infection, we plan to combine deep sequencing of the host transcriptome (RNA seq) with an assay of host proteins (proteomics). Aptamer-based assays now allow identification of >1,300 human proteins, which provides a unique opportunity to study broader changes in human proteins. Combined with host transcriptomics, this will enable discovery of molecules that can be used for targeted work and designing therapeutic interventions. We plan to recruit 20 volunteers (12 females, 8 males), which will be sufficient to compare changes across the stress state (females without stress [n=6], females with stress [n=6], males without stress [n=4], and males with stress [n=4]).The proposal is novel and aimed at discovery: (i) first use of colonoids to study C. jejuni infection; (ii) development of colonoids with specific host characteristics, i.e., sex and psychological stress; (iii) use of C. jejuni strains that have been known to cause PI-IBS; and (iv) use of next-generation sequencing of human transcriptome and proteome, which has not been done in response to C. jejuni infection. The proposal aligns with “Diarrheal diseases” in the Fiscal Year 2017 Peer Reviewed Medical Research Program areas of interest and studies “host responses,” which is a specific area of encouragement. In the short term, it will advance mechanistic science in the context of C. jejuni infection associated PI-IBS development. Additionally, it will test a novel platform to study variations in host biology (colonoids) that can be potentially used across the spectrum of intestinal disorders. Paving the way for identification of molecular targets for future work and development of preventative and treatment approaches using these targets will be the primary long-term outcome. In addition, a proteomic-based approach will likely allow biomarker discovery that can be used to identify persons at “high risk” for developing C. jejuni PI-IBS.
|Effective start/end date||9/1/18 → 2/29/20|
- Congressionally Directed Medical Research Programs: $317,914.00