Presence of Segmented Filamentous Bacteria in Human Children and Its Potential Role in the Modulation of Human Gut...

Area of Science:

• Microbiology
• Immunology
• Gastroenterology

Background:

• Segmented filamentous bacteria (SFB) are known commensals that interact with the host immune system.
• SFB colonization in mice promotes immune maturation, but their role in human gut immunity is less understood.
• Previous studies indicated SFB colonization in humans primarily occurs by 36 months of age and is difficult to detect later.

Purpose of the Study:

• To quantify SFB levels in human intestinal fluids.
• To investigate the correlation between SFB presence and host immune markers, specifically secretory IgA (sIgA) and Th17 pathway gene expression.
• To elucidate the role of SFB in the development of human gut immunity.

Main Methods:

• Quantitative PCR (qPCR) to measure SFB levels in intestinal fluids.
• Fluorescent in situ hybridization (FISH) and scanning electron microscopy (SEM) to visualize SFB morphology.
• Multiple displacement amplification PCR and mass spectrometry for SFB DNA and peptide identification.
• Analysis of secretory IgA (sIgA) titers and RT-qPCR for Th17 pathway gene expression in ileal biopsies.

Main Results:

• SFB constitute a small fraction of the total microbiota in SFB-positive individuals.
• A positive correlation was observed between SFB presence and total sIgA levels, particularly in children aged 8-36 months.
• SFB presence was associated with increased expression of Th17 pathway genes and upregulation of T and B cell receptor signaling pathways in ileal biopsies.

Conclusions:

• Segmented filamentous bacteria are rare members of the human gut microbiota.
• SFB presence is linked to elevated sIgA and Th17 immune responses in children.
• These findings suggest SFB play a significant role in the development of the human gut immune system.