Chlamydia trachomatis impairs T cell priming by inducing dendritic cell death

Area of Science:

• Immunology
• Microbiology
• Cell Biology

Background:

• Effective adaptive immunity against Chlamydia trachomatis is lacking, leading to chronic infections and disease.
• Dendritic cells (DCs) are vital for activating T cells during C. trachomatis infection.
• The impact of C. trachomatis on the T cell priming capabilities of DC subsets (cDC1s and cDC2s) is not well understood.

Purpose of the Study:

• To investigate how C. trachomatis affects the viability and T cell priming function of dendritic cell subsets.
• To elucidate the mechanisms of DC death induced by C. trachomatis.
• To determine if C. trachomatis-induced DC death contributes to immune evasion.

Main Methods:

• Utilized a mouse model of C. trachomatis infection.
• Assessed DC viability and apoptosis in vitro and in vivo.
• Performed co-culture experiments to evaluate T cell activation by infected DCs.
• Conducted RNA sequencing on DCs from infected mice.
• Validated findings using human DCs in vitro.

Main Results:

• C. trachomatis uptake reduced the viability of both cDC1 and cDC2 subsets, with cDC1s experiencing higher mortality.
• DC death was primarily apoptotic and dependent on Caspase-3/7 and Bak1/Bax.
• Infected DCs showed impaired T cell activation capacity, particularly affecting CD8+ T cell priming.
• RNA sequencing revealed upregulation of cell death pathways in DCs from infected mice.
• C. trachomatis induced cell death in human DCs.

Conclusions:

• C. trachomatis directly induces apoptosis in dendritic cells, compromising their ability to prime T cells.
• This pathogen-induced DC death may represent a strategy for C. trachomatis to evade the adaptive immune system.
• Understanding this mechanism could inform strategies to enhance host immunity against Chlamydia infections.