CD4 T cell dysfunction is associated with bacterial recrudescence during chronic tuberculosis

Area of Science:

• Immunology
• Microbiology
• Infectious Diseases

Background:

• Mycobacterium tuberculosis infection is usually controlled by the immune system.
• The mechanisms underlying the failure of immunity and subsequent disease reactivation remain unclear.
• C57BL/6 mice model chronic Mycobacterium tuberculosis infection, eventually succumbing to the disease.

Purpose of the Study:

• To investigate the role of CD4 T cell dysfunction in Mycobacterium tuberculosis recrudescence.
• To understand why initially controlled tuberculosis infections progress to active disease.

Main Methods:

• Development of a reductionist model to study antigen-specific T cells during chronic infection.
• Analysis of CD4 T cell phenotype, including coinhibitory receptor expression and cytokine production.
• Single-cell RNA sequencing (scRNAseq) to assess T cell polyfunctionality in infected lungs.

Main Results:

• Evidence of CD4 T cell senescence and exhaustion in chronically infected C57BL/6 mice.
• Upregulation of coinhibitory receptors and loss of effector cytokine production by CD4 T cells.
• scRNAseq revealed a limited number of polyfunctional CD4 T cells in the lungs of chronically infected mice.

Conclusions:

• CD4 T cell dysfunction, characterized by senescence and exhaustion, is implicated in Mycobacterium tuberculosis recrudescence.
• This dysfunction may initiate a feed-forward loop exacerbating disease progression.
• Further research is needed to clarify the causal link between T cell dysfunction and disease reactivation.