Chlamydia overcomes multiple gastrointestinal barriers to achieve long-lasting colonization

Area of Science:

• Microbiology
• Immunology
• Gastroenterology

Background:

• Chlamydia trachomatis (CT) is a common sexually transmitted infection, but also frequently found in the human gastrointestinal (GI) tract.
• Chlamydia muridarum (CM), a model organism for CT, can colonize the mouse GI tract, offering insights into Chlamydia's adaptability.

Purpose of the Study:

• To investigate the distinct roles of plasmid and chromosomal genes in Chlamydia's gastrointestinal colonization.
• To understand the mechanisms Chlamydia employs to overcome host barriers in different segments of the GI tract.

Main Methods:

• Utilized Chlamydia muridarum (CM) mutants deficient in plasmid or specific chromosomal genes.
• Assessed the colonization efficiency of these mutants in different regions of the mouse gastrointestinal tract (upper vs. lower).
• Investigated the function of specific genes (Pgp3, TC0237/TC0668) in evading host immune responses (acid, CD4+ T cells, IFNγ).

Main Results:

• CM mutants lacking plasmid functions were defective in upper GI colonization.
• Mutants with chromosomal gene deficiencies were more impaired in lower GI colonization.
• Plasmid-encoded Pgp3 is essential for surviving stomach acid and small intestine CD4+ T cells.
• Chromosome-encoded TC0237/TC0668 are critical for evading large intestine innate lymphoid cell-secreted IFNγ.

Conclusions:

• Chlamydia employs a compartmentalized colonization strategy in the GI tract, utilizing plasmid genes for initial spread and chromosomal genes for sustained colonization.
• Specific Chlamydia genes (Pgp3 and TC0237/TC0668) are crucial for overcoming distinct host defense mechanisms in the stomach, small intestine, and large intestine.
• Findings enhance understanding of Chlamydia pathogenesis and the medical significance of gut colonization.