A bispecific antibody based assay shows potential for detecting tuberculosis in resource constrained laboratory settings

• Published in: PloS one 2012-02, Vol.7 (2), p.e32340-e32340
• Main Authors: Sarkar, Susmita, Tang, Xinli L, Das, Dipankar, Spencer, John S, Lowary, Todd L, Suresh, Mavanur R
• Format: Article
• Language: English
• Subjects: Accuracy; Animals; Antibodies, Bispecific - immunology; Antibodies, Monoclonal - isolation & purification; Antigens; Antigens, Bacterial - immunology; Assaying; Biology; Biotin - metabolism; Bispecific antibodies; Blotting, Western; Body fluids; Cattle; Cell culture; Cell Line; Cell walls; Clinical Laboratory Techniques - methods; Confidence intervals; Disease transmission; Drug resistance; Drug therapy; Electrophoresis, Polyacrylamide Gel; Emergence; Enzyme-Linked Immunosorbent Assay - methods; Enzymes; Health aspects; Health Resources; Health risks; HIV; Horseradish peroxidase; Human immunodeficiency virus; Humans; Immunoassay; Immunoglobulins; Infections; Limit of Detection; Lipopolysaccharides - immunology; Medical diagnosis; Medical research; Medical treatment; Microscopy; Monoclonal antibodies; Multidrug resistance; Mycobacterium tuberculosis - immunology; Peroxidase; Pharmaceutical sciences; Pharmacy; Public health; Rabbits; Rats; Sensitivity and Specificity; Serum Albumin, Bovine - metabolism; Sputum; Staining and Labeling; Tuberculosis; Tuberculosis - diagnosis; Tuberculosis - immunology; Tuberculosis - microbiology; Urine
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0032340

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.