Serological Analysis of Human Tuberculosis by an ELISA with Mycobacterial Antigen 60

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Abstract
An ELISA method for detecting serum antibodies against A60, an antigen prepared from the cytoplasm of Mycobacterium bovis BCG, has been applied to 385 subjects, namely 197 controls (neonates, healthy adults, and tuberculin negative, nontuberculous patients), and 188 subjects at various stages of tuberculous infection and disease. Most IgM determinations gave negative results. While the neonates and normal adults had titers of IgG anti-A60 antibodies below the cut off value, wide variations in antibody liters were observed among the various types of subjects infected by M. tuberculosis. The results obtained with nontuberculous subjects were: 100% negative IgG in neonates and healthy adult individuals and 6.4% “false positive” cases among 124 non-tuberculous patients. The percentage of serologically positive cases of tuberculosis was: 5.9% in latent active primary forms, 42.8% in patent active primary forms, and 82.8% in active postprimary forms. Tuberculous infections had a positivity rate of 14.7%, while inactive postprimary tuberculosis had a positivity rate of 50%. The results obtained with A60 can favourably be compared with other serum ELISA tests for tuberculous antibodies against purified or semipurified mycobacterial antigens. Anti-A60 ELISA IgG antibody test can be useful to monitor the kinetics of humoral immunological response during tuberculous infection, disease and chemotherapy. A positive IgG ELISA test may support the diagnosis of active tuberculous disease.