Detection of Mycobacterium leprae antigens in urine of leprosy patients by monoclonal-antibody-based sandwich immunoradiometric assay and avidin-biotin based immunoblotting

Abstract

Urine samples from 54 leprosy patients and 12 controls were tested for the presence of Mycobacterium leprae antigens using monoclonal-antibody-based sandwich immunoradiometric antigen-capture assay. Excettion of antigen was observed in the urine of patients with tuberculoid borderline and lepromatous types of leprosy. M. leprae-specific 12 kDa protein antigen was seen in the urine of 56% of leprosy patients. M. leprea quasi-specific 35 kDa protein antigen (immunodominant) in that of 33% of the patients and mycobacterial cross-reactive polysaccharide antigen of 30–40 kDa in the urine of 54% of the patients. At least one of these antigens was found in the urine of about 90% of the patients. None of the controls was positive for any of the antigens. It appears that weakly immunogenic antigens are excreted to a far greater extent than the strongly immunogenic one. The avidin-biotin based immunoblotting also revealed antigens in the urine of leprosy patients. The fact that about 90% of the patients showed some antigen positivity, as determined by monoclonal-antibody-based sandwich antigen-capture assay, may be of value in the diagnosis of leprosy, particularly the hitherto poorly diagnosed tuberculoid leprosy.