Droplet digital PCR quantifies host inflammatory transcripts in feces reliably and reproducibly

Area of Science:

• Immunology
• Gastroenterology
• Molecular Biology

Background:

• The gut represents a critical interface for host-environment interactions and immune activity.
• Non-invasive methods for assessing gut immunological responses are currently limited.
• Fecal samples offer a proximity-based analyte for studying gut tissue responses.

Purpose of the Study:

• To develop and validate a non-invasive method for quantifying gut immune gene expression using fecal samples.
• To assess the feasibility of using droplet digital PCR (ddPCR) for analyzing host transcripts in stool.
• To establish a reliable method for interrogating the gut immune system through accessible samples.

Main Methods:

• Concentration of host transcripts from fecal specimens using bead-based affinity separation.
• Quantification of specific immune gene transcripts via droplet digital PCR (ddPCR).
• Normalization of transcript concentrations using Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as a reference gene.

Main Results:

• Host messenger RNA (mRNA) was detected in over 99% of 799 fecal samples analyzed from Malawian children.
• A detection threshold was established, showing high reproducibility (correlation coefficient >0.95) above 0.02 copies target/GAPDH.
• ddPCR provided higher transcript quantification than standard quantitative PCR (qPCR).
• Fecal sample preservation was simplified, not requiring immediate freezing or special additives.
• Measured immunoactive protein transcripts correlated with observed gut inflammation, validating the method's relevance.

Conclusions:

• This novel method enables non-invasive interrogation of gut gene expression from fecal samples.
• The technique is robust, reproducible, and offers a valuable tool for studying gut immunity and inflammation.
• Simplified sample handling and preservation enhance the practicality of this approach for field research.