Development of an ELISA for detection of antibody in leprosy.

An ELISA system was developed for detection of antibodies in leprosy using whole cells of bacteria as an antigen. Whole cells of M. smegmatis, M. vaccae, M. scrofulaceum, M. leprae, C. diphtheriae, and C. xerosis were compared. M. smegmatis was the most reactive against lepromatous sera with OD492 readings 1.5 times and five times higher than the others. In addition, when M. smegmatis were coated to microtiter plates with a volatile ammonium acetate/carbonate buffer and air dried, the antigen coating was found to be three times more reactive than antigen coated with nonvolatile Na borate buffer. Autoclaving M. smegmatis increased the reactivity with lepromatous sera 1.4- to 2.3-fold. M. leprae was found to be 4-10 times more reactive than autoclaved M. smegmatis. Autoclaving M. leprae did not increase reactivity. Antibody titers of some lepromatous sera had endpoint titers of greater than 1:10,000. Both antihuman IgG and antihuman IgA, IgM, and IgG combined conjugates were found to be equally effective in detecting high levels of antibody in patients with multibacillary diseases.