We compare whole cell ELISA antigens (Mycobacterium leprae) and two specific antigens: PG-I, phenolic glycolipid I of M. leprae and M-BGG, a synthetic antigen representing the terminal sugar ofPG-1 for their effectiveness in detecting anti body during chemotherapy. By the end of the 1 st year of treatment, antibody levels to M-BGG had declined by 42% of the initial EL ISA values, by the end of the 2nd year by 61 % and at the end of 3 years by 68%. Declines of similar magnitude were seen with the other antigens. We examined these sera by RID for changes in levels of IgG, IgM and IgA antibodies. The levels of IgG remained abnormally high throughout the 3 years of antimicrobial therapy. The serum levels of IgM and IgA antibodies remained at the upper limits of normal range. The decline seen with antibody to M. leprae antigens was not reflected by a similar decline of serum immunoglobulin levels. Thus, application of ELISA monitoring during the course of treatment may be valuable in measuring the effectiveness of chemotherapy.

In order to determine the frequency of occurrence of antibodies to semisynthetic antigens of My cobacterium leprae in clinically healthy nonpatient populations and to establish a 'baseline' for comparison with antibody frequen cies in both patients with a history of leprosy and their contacts, ELISAs were conducted using representative sera from two areas: a leprosy endemic area, Cebu City, Philippines and a nonendemic area for leprosy Chicago, Illinois, USA. These sera were tested, by an indirect IgM ELISA, for the presence of antibodies reacting with fo ur semisynthetic antigens based on the phenolic glycolipid I antigen of M. leprae: ND-O-BSA (natural disaccharide with octyl linkage to bovine serum albumin), NT-O-BSA (natural trisaccharide with octyl linkage to BSA), ND-P-BSA (natural disaccharide with phenolic ring linkage to BSA) and NT-P-BSA (natural trisaccharide with phenolic ring linkage to BSA). Using an OD reading ;;. 0•16 as positive, the antigen with the lowest background seroreactivity was ND-O-BSA, which reacted with 5/398 (1'3%) sera from Cebu, and 3/426 (0,7%) sera from Chicago. A total of 10 (2'5%) of 398 sera from the endemic area reacted with at least one antigen and 5 (1'3%) sera reacted with all four semisynthetic antigens. Of the 426 sera fr om Chicago, 12 (2,8%) were reactive with at least one antigen and 3 (0'7%) were reactive with all four semisynthetic antigens. Mean ELISA values for the 22 positive sera for each antigen ranged from 0• 17 to O• 3 OD units, while the mean values for all sera in