Differential expression of CD57 in antigen-reactive CD4+ T cells between active and latent tuberculosis infection

- Ag-specific CD4+ T cells were analyzed to find prognostic biomarkers of TB.
- The frequency of CD57-expressing cells was higher in active compared to latent TB.
- Lower frequency of PD-1-expressing cells was found in active compared to latent TB.
- CD57 could be a promising candidate prognostic biomarker of latent TB.

The development of diagnostic tests that predict the progression of latent tuberculosis infection to active disease is pivotal for the eradication of tuberculosis. As an initial step to achieve this goal, our study's aim was to identify biomarkers that differentiate active from latent tuberculosis infection. We compared active and latent tuberculosis infection groups in terms of the precursor frequency, functional subset differentiation, and senescence/exhaustion surface marker expression of antigen-specific CD4+ T cells, which were defined as dividing cells upon their encountering with Mycobacterium (M.) tuberculosis antigens. Among several parameters shown to have statistically significant differences between the two groups, the frequency of CD57-expressing cells could differentiate effectively between active disease and latent infection. Our results suggest that the expression of CD57 in M. tuberculosis-reactive CD4+ T cells could be a promising candidate biomarker with which to identify individuals with latent tuberculosis infection prone to progression to active disease.