1. Expression of IFN-α is found to be lower after successful treatment of tuberculosis.
Evidence Rating Level: 2 (Good)
Tuberculosis (TB) is an infectious disease killing over 1 million people annually worldwide, caused by the bacterium M. tuberculosis (M.tb). The immune response to TB involves T cells that express signalling proteins known as interferons (IFNs). IFN-γ, a Type II interferon, is known to combat bacterial infections. But Type I IFNs (α and β) can both bolster and hinder the mechanisms that protect against infection. Although the immune response leads to many TB infections becoming dormant, 10% of these cases develop clinical TB later on. Past studies have shown that the increase in Type I IFNs precedes clinical TB onset. This study investigated the Type I IFN levels in Indian TB patients. The blood samples of patients with active TB were analyzed before treatment, and 29% of these patients provided samples following successful treatment. Samples from the patients’ healthy household contacts (HHCs) were also analyzed. Prior to treatment, IFN-β and γ levels were comparable between TB patients and their HHCs (median fold expression for IFN-β: TB = 0.030, HHC = 0.031; for IFN-γ: TB = 0.071, HHC = 0.79). Contrastingly, IFN-α expression was 3.5 folds higher (p<0.0001) at 0.8 median fold in TB patients and 0.23 median fold in HHCs. As well, IFN-α was reduced by 3 folds in successfully treated patients, from a median fold expression of 0.37 to 0.13 (p<0.001), and IFN-β was reduced 2 folds, from 0.04 to 0.02 (p<0.001). IFN-γ was unchanged. Overall, IFN-α can be an important prognostic marker for TB, since its levels decrease dramatically after successful TB treatment.
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