Host Epithelial Responses in Pathophysiology of Campylobacter jejuni Postinfection Irritable Bowel Syndrome

Diarrheal diseases are common in the U.S. and worldwide. Travelers to developing countries and military personnel are particularly at an increased risk of getting intestinal infection. Most patients recover completely from this illness; however, about 1 in 10 may develop a chronic intestinal condition called irritable bowel syndrome (IBS). Because it develops after infection, it is also referred to as post-infection IBS (PI-IBS). Patients with this condition have recurring abdominal pain and irregular bowel movements, mostly diarrhea or mixed diarrhea and constipation. Many patients with PI-IBS have symptoms even 8 years following the infection. These symptoms can have a significant impact on an individual's quality of life and productivity and can result in frequent healthcare seeking. It is estimated that ~15% of U.S. adults may suffer from IBS, with similar numbers seen worldwide. The scientific mechanisms for IBS are not well understood, and treatment options for IBS are limited and often not effective.

The interaction between infection and IBS provides an opportunity to discern the mechanisms associated with this disease process. Several studies have shown that women are at an increased risk for IBS and PI-IBS. Secondly, other studies have shown that the presence of psychological stress during infection can significantly increase the odds of PI-IBS development, although the reasons for this are not clear. Among bacterial infections, an organism, Campylobacter, is particularly common and has been repeatedly associated with PI-IBS development. The proposed study is geared to understand why certain individuals with Campylobacter infection have a higher risk of PI-IBS. There is no good animal model to study this infection, and it is difficult to study humans during infection. Most studies with Campylobacter have been done using cells derived from cancer patients and that can be grown indefinitely. However, this is not ideal, since these cells lack the complex architecture and cellular environment seen in the human intestinal cell lining. Thus, we plan to obtain small tissue samples from the colon of human volunteers, disintegrate these biopsies to obtain stem cells, and grow these into specialized structures called colonoids. These colonoids will then be infected with special strains of Campylobacter that we know have caused PI-IBS in other people. The colonoids we will develop will be from both men and women to determine the effects of sex and from those with or without chronic psychological stress to study the effects of stress. We plan to recruit and develop colonoids from tissues of 20 human volunteers. These 20 unique colonoids will be infected with 3 different C. jejuni strains or injected with a control solution. Several hours later, the colonoid tissue will be processed to obtain the RNA (to reflect expressed genes) and the proteins. This material will be analyzed using technology called next-generation sequencing, which can detect and quantify hundreds of thousands of genes and more than 1,300 human proteins. Additionally, we will examine how different strains of Campylobacter invade the cells in organoids and affect their integrity.

The information obtained from the proposed studies will allow us to understand how different C. jejuni strains can affect colonoids from distinct types of host volunteers (men/women, no stress/stress). We will be able to tell if there are specific genes and proteins that are affected regardless of host and bacterial type and if there are specific genes and proteins that are changed in colonoids from specific sex and in stress states. In addition to providing a list of genes and proteins, signaling pathways that occur in response to infection will be identified. The broader goal is to identify molecules for future dedicated work and use them to design platforms that can predict who may develop PI-IBS after an infection. These are called biomarkers and can be helpful in ascertaining and treating individuals to prevent the onset of PI-IBS.

The project addresses the Fiscal Year 2017 Peer Reviewed Medical Research Program topic area 'Diarrheal Diseases' and within that area aims to investigate host responses and develop therapies to treat acute bacterial and viral infections commonly associated with travel that often lead to chronic functional bowel and rheumatological disorders. In addition to civilians, Campylobacter is a common cause of diarrhea during deployment and has been associated with three-fold higher risk of PI-IBS in persons in the Armed Forces. Psychological stress is also common during deployment and has been shown to further magnify the PI-IBS risk. Thus, the project will directly study a disease important for our military personnel and help improve their health.