PROJECT SUMMARY/ABSTRACT Clostridium difficile infection (CDI) is the single most common cause of infectious antibiotic-induced diarrhea. The primary virulence factors that are known to cause CDI are the two toxins: TcdA and TcdB. These toxins incite intense inflammation of the intestinal tissue and in severe cases, of the systemic circulation. Adenosine is released in increased amounts during tissue injury and its action is mediated by four receptors—A1, A2A, A2B and A3 adenosine receptors (AR). We have shown that TcdA and TcdB upregulate A2BAR and to lesser extent, A2AAR, transcript expression in a human intestinal cell line. Inhibition or deletion of A2BARs decreases TcdA-induced secretion and mucosal injury in ileal loops and in infected mice. While both A2AARs and A2BARs are known to be present in immune cells, gut epithelial cells express higher levels of A2BAR transcript than other cell types. We hypothesize that adenosine, through its interactions with A2BAR and A2AAR, modulates host responses to C. difficile toxins. Pharmacologic manipulation of these adenosine receptors will ameliorate toxin-induced epithelial injury and improve outcomes during infection. In this proposal, we shall determine how A2BAR inhibition regulates the local inflammatory responses to C. difficile toxins in primary human intestinal tissue (Aim 1). We shall also determine how A2AAR activation modulates systemic inflammatory responses to C. difficile toxins in human neutrophils (Aim 2). This research plan will provide insight into how A2AAR and A2BAR signaling mediate host immune responses to C. difficile toxins and how manipulation of these receptors may provide novel, non-antimicrobial, host-directed approaches to treating CDI.

PROJECT NARRATIVE Clostridium difficile infection is the leading cause of antibiotic-associated diarrhea worldwide. Antibiotic administration is the mainstay of treatment but is associated with high incidence of relapse. Our research explores how controlling adenosine receptor activity during intestinal tissue inflammation and damage caused by C. difficile toxins can improve diarrhea and outcome of treatment.