Salmonella enterica serovar Typhi impairs CD4 T cell responses by reducing antigen availability

Area of Science:

• Immunology
• Microbiology
• Genetics

Background:

• Salmonella enterica serovar Typhi causes typhoid fever, while S. Typhimurium causes gastroenteritis.
• S. Typhi possesses the TviA regulatory protein, absent in S. Typhimurium, which controls flagellin expression.

Purpose of the Study:

• To investigate the impact of TviA-mediated flagellin gene regulation on CD4 T cell responses during S. Typhimurium infection in a mouse model.

Main Methods:

• Introduction of the S. Typhi tviA gene into S. Typhimurium.
• Assessing dendritic cell antigen presentation to T cells in vitro.
• Analyzing T cell activation, proliferation, and bacterial dissemination in vivo.

Main Results:

• TviA expression in S. Typhimurium suppressed dendritic cell antigen presentation of flagellin.
• Reduced flagellin expression impaired naive CD4 T cell activation and proliferation in lymphoid tissues.
• This led to increased bacterial dissemination to the spleen.

Conclusions:

• TviA-mediated repression of flagellin expression in Salmonella reduces antigen availability.
• This mechanism weakens flagellin-specific CD4 T cell responses, potentially contributing to S. Typhi pathogenesis.