Role of host glycosylation in susceptibility to C. difficile infection

Clostridioides difficile (CD) is a gram-positive anaerobic and spore-forming bacterium that causes diarrhea and colitis. It is the leading cause of nosocomial antibiotic-associated diarrhea in adults that have high levels of recurrence and mortality. Toxin A and B (TcdA/TcdB) are the main CD virulence factors that cause cytotoxic effects and inflammation. Gastrointestinal tract expresses substantial amount of glycan structures and glyconconjugates which is an important factor contributing to the composition and physiology of intestinal microbiota. These glycoconjugates were utilized by intestinal microbiota and pathogens for microbial attachment site and as nutrients. Therefore, variation in host glycosylation can mediate susceptibility to intestinal inflammation such as to enteric pathogens. The glycosyltransferase gene b4galnt2 encodes a beta-1,4-N-acetylgalactosaminyltransferase known to catalyze the last step in the biosynthesis of the Sd(a) and Cad blood group antigens and is expressed in the GI tract of most mammals, including humans. Loss of B4galnt2 expression is associated with altered intestinal microbiota composition. In our previous study, we found B4galnt2 intestinal expression was strongly associated with increased susceptibility to Salmonella infection which is microbiota dependent. However, in our current study, B4galnt2-deficient mice showed increased susceptibility to CD infection. B4galnt2-deficient mice showed significantly higher bacterial loads and increased level of lipocalin-2 as well as inflammation score. Ex vivo experiments using intestinal crypt organoids derived from wild type and B4galnt2 deficient mice showed higher cell death in organoid from B4galnt2-/- after CD culture filtrate and CD toxin TcdA treatment. Our preliminary experiments showed that glycosylation can influence the signal activation such as ERK 1/2, p38/MK2 and JNK1 after CD toxins treatment.

Thus, glycosylation can influence to the regulation of signal transduction particularly upon bacterial infection.