Role of alpha-crystallin, early-secreted antigenic target 6-kDa protein and culture filtrate protein 10 as novel diagnostic markers in osteoarticular tuberculosis

Osteoarticular tuberculosis constitutes about 3% of all tuberculosis cases. Early and accurate diagnosis of tuberculosis is a challenging problem especially in the case of osteoarticular tuberculosis owing to the lower number of bacilli. However, an accurate and timely diagnosis of the disease results in an improved efficacy of the given treatment. Besides the limitations of conventional methods, nowadays molecular diagnostic techniques have emerged as a major breakthrough for the early diagnosis of tuberculosis with high sensitivity and specificity. Alpha-crystallin is a dominantly expressed protein responsible for the long viability of the pathogen during the latent phase under certain stress conditions such as hypoxia and nitric oxide stress. Two other proteins—early secreted antigenic target-6 and culture filtrate protein-10—show high expression in the active infective phase of Mycobacterium tuberculosis. In this article, we focus on the different proteins expressed dominantly in latent/active tuberculosis, and which may be further used as prognostic biomarkers for diagnosing tuberculosis, both in latent and active phases.