Aging Dampens the Intestinal Innate Immune Response during Severe Clostridioides difficile Infection and Is Associated with Altered Cytokine Levels and Granulocyte Mobilization

Abstract

Clostridioides (formerly Clostridium) difficile is the most common cause of hospital-acquired infection, and advanced age is a risk factor for C. difficile infection. Disruption of the intestinal microbiota and immune responses contribute to host susceptibility and severity of C. difficile infection. However, the specific impact of aging on immune responses during C. difficile infection remains to be well described. This study explores the effect of age on cellular and cytokine immune responses during C. difficile infection. Young mice (2 to 3 months old) and aged mice (22 to 28 months old) were rendered susceptible to C. difficile infection with the antibiotic cefoperazone and then infected with C. difficile strains with varied disease-causing potentials. We observe that the host age and the infecting C. difficile strain influenced the severity of disease associated with infection. Tissue-specific CD45+ immune cell responses occurred at the time of peak disease severity in the ceca and colons of all mice infected with a high-virulence strain of C. difficile; however, significant deficits in intestinal neutrophils and eosinophils were detected in aged mice, with a corresponding decrease in circulating CXCL1, an important neutrophil recruiter and activator. Interestingly, this lack of intestinal granulocyte response in aged mice during severe C. difficile infection was accompanied by a simultaneous increase in circulating white blood cells, granulocytes, and interleukin 17A (IL-17A). These findings demonstrate that age-related alterations in neutrophils and eosinophils and systemic cytokine and chemokine responses are associated with severe C. difficile infection and support a key role for intestinal eosinophils in mitigating C. difficile-mediated disease severity.

Intestinal inflammation and altered gut microbiota associated with inflammatory bowel disease renders mice susceptible toClostridioides difficilecolonization and infection

“…The lower rate of C. difficile colonization in IBD we observed suggests that intestinal inflammation may stochastically shape the gut microbiota may be stochastic, whereas alterations in gut microbiota following antibiotic treatment is more predictable, given the specificity of these drugs. We have previously shown that in the setting of advanced age, representing a distinct immune-and microbiota-altered host state that increases risk for C. difficile infection, CDI results in age-related alterations in neutrophil and eosinophil responses in mice (25). While we found no significant difference in neutrophil responses in mice with IBD-induced or antibiotic-induced CDI, IBD was associated with differences in eosinophil response compared to CDI following antibiotic use.…”

“…To determine a correct dose of C. difficile spores per challenge, viable spores in each inoculum were enumerated by plating for colony-forming units (CFU) per mL on pre-reduced taurocholate cycloserine cefoxitin fructose agar (TCCFA). TCCFA was prepared as previously described (25).…”

“…Formalin-fixed tissue sections prepared from cecum and colon were H&E stained and evaluated by a blinded animal pathologist. Histopathologic damage in each tissue was scored using epithelial destruction, immune cell infiltration, and edema on a 4-point scale for each category and the sum of these scores determined the histological score (22,25,28). https://github.com/AbernathyClose/AbernathyClose_IbdCdi_mBio_2020.…”

Teaching old mice new tricks: the utility of aged mouse models of C. difficile infection to study pathogenesis and rejuvenate immune response

“…One method would be to utilize gnotobiotic mice that do not possess a normal microbiome, 16 while another method would be to utilize antibiotics to disrupt the normal intestinal microbiome. 17–20 Different antibiotic regimens (combination antibiotic cocktail, 17–19 and cefoperazone 20 ) were utilized in different models, while the age of the mice also differed from model to model. In this paper, we reviewed the features of each animal model and the key findings from the studies.…”

“… 31 Abernathy-Close et al utilized aged mice that were the oldest among the published studies (22–28 months old) and also bred in the same facility as young mice (2–3 months old). 20 In addition to a different antibiotic treatment, two different strains, VPI10463 and 630, were used to explore the impact of aging on CDI outcomes by infecting with strains of different virulence. 20 VPI10463, as described above, is a highly toxigenic strain that produces high levels of both toxin A and B, while 630, which is a clinical strain isolated from a patient, is considered low virulence due to the lower levels of toxin production.…”