Distinct T and innate-like lymphocyte reprogramming following lyophilized fecal microbiota transplantation in recurrent <i>C. difficile</i> infection.
This study provides preliminary insights into immune changes following LFMT in rCDI patients, but findings are based on a small sample and require further investigation.
Where it sits
this study against the rest of the fgl (fg loop peptide) corpusSummary and findings
This study examined immune reprogramming following lyophilized fecal microbiota transplantation (LFMT) in recurrent Clostridioides difficile infection (rCDI) patients. Flow cytometry was performed on 19 LFMT recipients and 18 controls, while single-cell RNA sequencing was conducted on two LFMT recipients. No significant changes were observed in flow cytometry results post-treatment.
Abstract
Fecal microbiota transplantation (FMT) is highly effective in preventing recurrent <i>Clostridioides difficile</i> infection (rCDI), yet its immunological mechanisms remain poorly defined. While bacterial engraftment and recovery of microbial diversity are central to FMT efficacy, accumulating evidence suggests that host immune reprogramming is involved. In murine models, regulatory CD4⁺ T cells are indispensable for clearing <i>C. difficile</i>. To address this mechanistic gap, we examined systemic immune reprogramming following FMT by performing flow cytometry and single-cell RNA sequencing (scRNA-seq) on a subset of successfully treated participants from a clinical trial comparing lyophilized FMT (LFMT) with lyophilized sterile fecal filtrate (LSFF, no live bacteria) for preventing rCDI. Flow cytometry was performed on peripheral mononuclear cells from 19 LFMT recipients and 18 LSFF recipients, and scRNA-seq analysis was performed on two LFMT recipients. Although flow cytometry results did not show significant changes in the assessed markers after rCDI resolution in either treatment group, exploratory scRNA-seq in the two LFMT recipients revealed distinct LFMT-associated transcriptional signatures across adaptive and innate-like lymphocyte populations. LFMT was associated with upregulated activation and regulatory genes (<i>CD69</i>, <i>STAT1</i>, <i>TOX</i>, <i>RORA</i>, <i>FOXP3</i>) in CD4⁺ and CD8⁺ T cells, suggesting enhanced immune regulation with reduced cytotoxic gene expression (<i>GZMB</i>, <i>PRF1</i>, <i>GNLY</i>). Innate-like lymphocytes displayed broad activation, with natural killer cells showing increased <i>KLRD1</i>, <i>PRF1</i>, and <i>IL2RB</i> and mucosal-associated invariant T cells (MAIT cells) upregulating <i>STAT1</i>, <i>JUN</i>, and <i>RORA</i> while downregulating <i>KLRB1</i> and <i>STAT3</i>. These transcriptional programs are consistent with recalibration of T cell homeostasis and innate-like lymphocyte activation, potentially driven by microbial restoration. Collectively, this exploratory study provides the first single-cell immune atlas of LFMT in rCDI, identifying coordinated activation of regulatory, effector, and innate immune pathways. Given the small sample size, these findings should be considered hypothesis-generating, requiring validation in larger cohorts.
Background
The study addresses the immunological mechanisms of fecal microbiota transplantation (FMT) in preventing recurrent Clostridioides difficile infection (rCDI). Previous research has established that bacterial engraftment and microbial diversity are crucial for FMT efficacy, but the role of host immune reprogramming remains unclear. Understanding these mechanisms is important for optimizing FMT and enhancing its effectiveness.
Methods
This study utilized flow cytometry and single-cell RNA sequencing (scRNA-seq) to analyze immune reprogramming in rCDI patients. A total of 19 LFMT recipients and 18 LSFF recipients were included for flow cytometry analysis. scRNA-seq was performed on a subset of two LFMT recipients. The primary outcome measures included changes in immune cell markers and transcriptional profiles.
Results
Flow cytometry results indicated no significant changes in immune markers post-treatment in either LFMT or LSFF groups. However, scRNA-seq analysis identified distinct transcriptional signatures associated with LFMT, including upregulation of genes related to immune activation and regulation in T cells.
Interpretation
The findings suggest that LFMT may lead to immune reprogramming, with enhanced regulatory pathways and reduced cytotoxic gene expression in T cells. However, the lack of significant changes in flow cytometry results raises questions about the clinical relevance of these findings. The small sample size and exploratory nature of the scRNA-seq analysis limit the conclusions that can be drawn, necessitating further validation in larger studies.
Key findings
- Flow cytometry did not show significant changes in assessed markers after rCDI resolution in either treatment group.
- Exploratory scRNA-seq revealed distinct LFMT-associated transcriptional signatures in adaptive and innate-like lymphocyte populations.
- LFMT was associated with upregulated activation and regulatory genes in CD4⁺ and CD8⁺ T cells.
- Natural killer cells showed increased KLRD1, PRF1, and IL2RB.
- Mucosal-associated invariant T cells upregulated STAT1, JUN, and RORA while downregulating KLRB1 and STAT3.
Limitations
- small sample size of 19 LFMT and 18 LSFF recipients
- exploratory nature of scRNA-seq analysis
- no significant changes observed in flow cytometry results
- results should be considered hypothesis-generating