Abstract
The re-emergence of tuberculosis (TB) as a global public health threat highlights the necessity of rapid, simple and inexpensive point-of-care detection of the disease. Early diagnosis of TB is vital not only for preventing the spread of the disease but also for timely initiation of treatment. The later in turn will reduce the possible emergence of multi-drug resistant strains of Mycobacterium tuberculosis. Lipoarabinomannan (LAM) is an important non-protein antigen of the bacterial cell wall, which is found to be present in different body fluids of infected patients including blood, urine and sputum. We have developed a bispecific monoclonal antibody with predetermined specificities towards the LAM antigen and a reporter molecule horseradish peroxidase (HRPO). The developed antibody was subsequently used to design a simple low cost immunoswab based assay to detect LAM antigen. The limit of detection for spiked synthetic LAM was found to be 5.0 ng/ml (bovine urine), 0.5 ng/ml (rabbit serum) and 0.005 ng/ml (saline) and that for bacterial LAM from M. tuberculosis H37Rv was found to be 0.5 ng/ml (rabbit serum). The assay was evaluated with 21 stored clinical serum samples (14 were positive and 7 were negative in terms of anti-LAM titer). In addition, all 14 positive samples were culture positive. The assay showed 100% specificity and 64% sensitivity (95% confidence interval). In addition to good specificity, the end point could be read visually within two hours of sample collection. The reported assay might be used as a rapid tool for detecting TB in resource constrained laboratory settings.
Highlights
In 2009, the World Health Organisation (WHO) reported 9.4 million cases of tuberculosis (TB) and 1.7 million deaths worldwide [1]
It should be noted that development of new diagnostics for TB has been emphasized as one of the six strategies in the WHO recommendations to combat the spread of the disease [3]
bovine serum albumin (BSA)-Hex (81.4 kDa) and BSA (66.3 kDa) were run on SDS-PAGE (Fig. 2A.) and transferred to nitrocellulose membrane, which was probed with purified CS-35 monoclonal antibodies (MAb) (2 mg/ml)
Summary
In 2009, the World Health Organisation (WHO) reported 9.4 million cases of tuberculosis (TB) and 1.7 million deaths worldwide [1]. In spite of the best efforts from the researchers round the globe, TB is the leading cause of death by a single, treatable infectious disease. In the last few decades, the situation of TB has worsened due to co-infection with the Human Immune Deficiency (HIV) virus and the emergence of multi-drug resistant (MDR) and extremely drug resistant (XDR) strains of M. tuberculosis. It should be noted that development of new diagnostics for TB has been emphasized as one of the six strategies in the WHO recommendations to combat the spread of the disease [3]
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