Background: The analysis of phenotypic changes in blood-based immune biomarkers has been proposed as a novel, non-sputum approach to evaluate tuberculosis (TB) therapy success.

Objective: To analyze the expression of CD27, HLA-DR, CD38, and Ki-67 biomarkers in Mtb-specific CD4⁺ T-cells and validate their ability to monitor treatment outcome.

Methods: A total of 45 blood samples were collected at the beginning (<1 month since start), middle (between 2 and 4 months after start), and end (?6 months) of anti-TB therapy from 17 pulmonary TB patients. Peripheral blood mononuclear cells were stimulated with ESAT-6/CFP-10 or PPD antigens and labeled with antibodies against CD3, CD4, CD8, CD27, CD38, HLA-DR, IFN-?, Ki-67, and TNF-? for flow cytometry analysis.

Results: The percentage of CD27-, HLA-DR+, and Ki-67+ populations within Mtb-CD4+ T-cells (CD4+ cells producing IFN-? and/or TNF-? cytokines after ESAT-6/CFP-10 or PPD stimulation) was significantly decreased after completing anti-TB therapy for both stimuli (p<0.01 for CD27 and Ki-67, p<0.05 for HLA-DR). Data also shows that HLA-DR decrease was significant already by mid-therapy (p<0.01 for ESAT-6/CFP-10, p<0.05 for PPD), whereas CD27 decrease became significative after mid-therapy (p<0.05 for both stimuli). No significant decrease in CD38 expression was found during and after therapy.

Conclusions: CD27, HLA-DR, and Ki-67 markers on CD4+ specific T-cells are differentially expressed depending on treatment intake and its duration. Further studies are needed to validate this approach as a tool for disease and therapy management.