Mycobacterial carbohydrate antigens for serological testing of patients with leprosy

To determine whether quantitation of antibodies to mycobacterial carbohydrate determinants would be valuable in serodiagnosis and monitoring of leprosy, we tested serum IgM antibody to Mycobacterium leprae phenolic glycolipid I and IgM and IgG antibodies to Mycobacterium tuberculosis and M. leprae lipoarabinomannan (LAM) by enzyme-linked immunosorbent assay. Seventy-one percent of patients with paucibacillary disease and 85.5% of patients with multibacillary disease were positive for at least one of the three antibodies. The 15% of antibody-negative patients with multibacillary disease were mostly long-term-treated patients, with inactive disease by biopsy. There was excellent agreement between M. tuberculosis LAM and M. leprae LAM in detection of antibodies. Bacillary index and levels of both IgG and IgM antibodies to LAM were positively correlated when all patients were analyzed. When patients with a history of erythema nodosum leprosum (ENL) were analyzed separately, there was no correlation between IgM or IgG antibody to LAM and bacillary index, a result suggesting a possible role for LAM in the pathogenesis of ENL.