In VivoPhysiological and Transcriptional Profiling Reveals Host Responses to Clostridium difficile Toxin A and Toxin B

Abstract

Toxin A (TcdA) and toxin B (TcdB) of Clostridium difficile cause gross pathological changes (e.g., inflammation, secretion, and diarrhea) in the infected host, yet the molecular and cellular pathways leading to observed host responses are poorly understood. To address this gap, we evaluated the effects of single doses of TcdA and/or TcdB injected into the ceca of mice, and several endpoints were analyzed, including tissue pathology, neutrophil infiltration, epithelial-layer gene expression, chemokine levels, and blood cell counts, 2, 6, and 16 h after injection. In addition to confirming TcdA's gross pathological effects, we found that both TcdA and TcdB resulted in neutrophil infiltration. Bioinformatics analyses identified altered expression of genes associated with the metabolism of lipids, fatty acids, and detoxification; small GTPase activity; and immune function and inflammation. Further analysis revealed transient expression of several chemokines (e.g., Cxcl1 and Cxcl2). Antibody neutralization of CXCL1 and CXCL2 did not affect TcdA-induced local pathology or neutrophil infiltration, but it did decrease the peripheral blood neutrophil count. Additionally, low serum levels of CXCL1 and CXCL2 corresponded with greater survival. Although TcdA induced more pronounced transcriptional changes than TcdB and the upregulated chemokine expression was unique to TcdA, the overall transcriptional responses to TcdA and TcdB were strongly correlated, supporting differences primarily in timing and potency rather than differences in the type of intracellular host response. In addition, the transcriptional data revealed novel toxin effects (e.g., altered expression of GTPase-associated and metabolic genes) underlying observed physiological responses to C. difficile toxins.

The role of purified Clostridium difficile glucosylating toxins in disease pathogenesis utilizing a murine cecum injection model

“…1 and 3). This further supports that TcdA was more potent than TcdB in this model, although the host transcriptional responses to TcdA and TcdB are reportedly similar [43]. But the rapid death caused by TcdA may also be due to shock; however, a few of the mice treated with the highest dose of TcdA quickly produced watery diarrhea which may have flushed out some of the excess toxin and allowed them to survive for a few extra hours, but they still succumbed to death in less than 48 h like those receiving a fifth of the dose.…”

Interleukin-22 Regulates the Complement System to Promote Resistance against Pathobionts after Pathogen-Induced Intestinal Damage

“…Neutrophils isolated from Il22 −/− and WT mice showed a similar bactericidal activity (Figure S5B), indicating that IL-22 does not affect the bactericidal activity of neutrophils. To further study the immune responses elicited by IL-22, we reviewed the GEO dataset (accession GDS3226 and GSE44091) of gene expression in IL-22-treated or TcdA and TcdB toxins-treated murine intestines (Zheng et al ., 2008; D‧Auria et al ., 2013). In addition to genes known to be induced by IL-22, such as S100 proteins and acute phase proteins (Liang et al ., 2010; Sonnenberg et al ., 2012), analysis of the datasets revealed increased expression of complement factor C3 in IL-22- and TcdA/TcdB toxins-treated mice (Figure S5 C and D).…”

Glucosyltransferase activity ofClostridium difficileToxin B is essential for disease pathogenesis

“…We further used acute murine CDI model 9 In summary, by using two independent animal intestinal disease models, we consistently demonstrated that TcdB in vivo potency is critically dependent on the glucosyltransferase activity. These results are consistent with our previous studies using systemic toxemia model 10,11 .…”