Assessment of possible diagnostic and prognostic markers of tuberculosis

Abstract

Tuberculosis (TB) remains one of the leading causes of death. Delayed diagnosis and treatment of TB as well as an emergence of drug-resistant TB are major problems in Thailand, which has a high burden of both TB and HIV infections. Assessment of possible diagnostic and prognostic markers of MTB infection is a priority.

The CHULA TB National Research University (NRU) prospective study was conducted at 3 large urban tertiary care hospitals. Patients who had suspected pulmonary (PTB) were enrolled. Expectorated sputum samples were sent for staining, mycobacterial culture, and the Xpert MTB/RIF. Peripheral blood mononuclear cells (PBMCs) were cryopreserved and archived and the CD25/CD134 (OX40) assay performed on thawed cells.

The Xpert MTB/RIF assay was evaluated for assay performance in comparison with AFB smear and culture as a gold standard and was found to be superior.

The diagnostic utility of measuring antigen specific immune response to TB infection, via the CD25/CD134 (OX40) assay was explored. This assay had high sensitivity and specificity in diagnosis of PTB with superior performance characteristics in the HIV-infected population.

The pattern of kinetics of recall immune responses to specific MTB antigens CD4 T cells immune response and of specific regulatory CD4 T cell responses to MTB (CD39Sp-T cells) were investigated in individuals receiving treatment for active PTB, with and without intercurrent HIV infection. We found the specific CD4 T cell responses and specific CD4 T cells regulatory responses to MTB were potentially differentially not completely restored, making patients more susceptible to reinfection post therapy in HIV co-infection and it is unlikely to be caused from TB induced immunosuppression.

Assessment of candidate biomarkers of Th1/Th2, inflammatory cytokines/chemokines and serum 25 – hydroxyvitamin D (25-OH Vitamin D) were performed at the time of TB diagnosis. Patients who died or were cured from TB were compared in a case control study to provide pilot data regarding the potential these analytes to act as biomarkers predictive of the outcome of TB treatment. The most promising biomarkers that identified mortality risk were IFN-γ, granzyme A and granzyme B. The roles of these granzymes need to be further explored as possible predictors of disease progression.