Pathway analysis of the intestinal transcriptome of mice rescued from sepsis via a fecal microbiota transplant demonstrates a role for IL22.
Monika Krezalek; Jennifer DeFazio; Sangman Kim; Nikolai Khodarev; Alexander Zaborin; Scott Christley; Baddr Shakhsheer; Kristina Guyton; Bana Jabri; Olga Zaborina; John Alverdy, The University of Chicago
Post-surgical sepsis due to hospital acquired pathogens (PSS-HAP) is one of the most common causes of death in the surgical ICU. We recently demonstrated that PSS-HAP pathogenesis is driven by a critical loss of the intestinal “microbiome” leading to systemic immune dysregulation and mortality which can be reversed by a fecal microbiota transplant (FMT).Hypothesis:
Here we hypothesize that the rescue effect of FMT is mediated in part by its ability to suppress IL-22.Methods:
We modeled lethal gut-derived sepsis using mice subjected to a 30% hepatectomy followed by cecal inoculation with HAPs consisting of a multi-drug resistant human pathogen community isolated from the stool of a septic ICU patient. Mice showing signs of sepsis on POD1 were administered a fecal microbiota transplant (FMT) consisting of homogenized pooled mouse cecal contents versus control material consisting of autoclaved (AC) pooled cecal contents. Whole-genome transcriptional profiling was performed on cecal tissues using Illumina MouseRef-8 v2 arrays with functional analysis of differentially expressed genes using Ingenuity™ pathway analysis and DAVID software.Results:
In the control AC group we noted systemic activation of pathways associated with adaptive and innate immunity, including TLR4/Myd88-dependent pro-inflammatory pathways. These pathways were significantly associated with over-expression of up-stream pro-inflammatory mediators: IL-1ß (13 fold), TNF α (43 fold) and IL-17A (60 fold). We also noted increased expression of STAT3 (2.5 fold) and its downstream target genes (up to 140 fold). Treatment by FMT led to significant attenuation of these pathways on POD2 compared to AC. Given that STAT3 controls IL-22 expression and given the known relationship of IL-22 production to TLR4 signaling, we directly assayed IL-22 in these experiments via ELISA and qRT-PCR and observed that FMT suppresses IL-22 production compared to AC controls (2.5 and 8 fold reduction via ELISA and qRT- PCR respectively p<0.01). In order to determine the role of IL-22 in the FMT-mediated rescue effect, we treated septic mice with anti-IL22 antibody on POD1 and observed a significant reduction in mortality (AC=73%, anti-IL-22= 40% p<0.01), although FMT provided the lowest mortality (13%) p<0.001, n=15/group).Conclusions:
Taken together, these studies suggest that FMT can rescue mice from severe post- surgical sepsis due to hospital acquired pathogens via mechanisms involving, in part, IL-22 expression.