Evaluation of four semi-synthetic Mycobacterium leprae antigens with sera from healthy populations in endemic and non-endemic areas.

In order to determine the frequency of occurrence of antibodies to semisynthetic antigens of Mycobacterium leprae in clinically healthy nonpatient populations and to establish a 'baseline' for comparison with antibody frequencies 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 four 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 > or = 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 from 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 0.3 OD units, while the mean values for all sera in each area ranged from 0.01 to 0.04 OD units for all four antigens. Reactivity of 14 of the positive sera to some antigens, but not all four semisynthetic antigens, indicated that the carrier and linker arms might be associated with this background reactivity. Investigation of alternative linker arms and carriers is warranted. We conclude that nonspecific background reactivity to the semisynthetic antigens representing the PG-I molecule of M. leprae is 0.7-1.3%, based on a > or = 0.16 OD cutoff value. From these data it was concluded that reactivity in individuals free of leprosy was low enough to warrant use of these antigens in a diagnostic setting, such as screening household contacts and highly endemic populations. When incidence and prevalence of leprosy are low, testing with these antigens would not be cost effective, unless applied to high risk individuals.(ABSTRACT TRUNCATED AT 400 WORDS)

Evaluation of Mycobacterium leprae antigens in the monitoring of a dapsone-based chemotherapy of previously untreated lepromatous patients in Cebu, Philippines.

Thirty-five previously untreated lepromatous patients receiving dapsone-based therapy were monitored throughout their 5-year period of treatment by serology and by pathology. Sequentially collected sera were used to evaluate the usefulness of four Mycobacterium leprae antigens as used in ELISA to monitor the progress of their therapy. ELISA results were compared with each other and with bacterial load over the treatment period and with duration of treatment. The ELISAs, based on the measurement of IgM antibody reactivity to the two neoglycoproteins (NDO and NTO) representing the phenolic glycolipid antigen of M. leprae, were found to be the most effective in monitoring treatment. A whole M. leprae based ELISA was less efficient in monitoring treatment because it failed to measure antibodies in 8 out of 35 patients and because it provided consistently lower values than either NTO or NDO. The ELISA-inhibition test based on the detection of antibodies to a species-specific epitope on the 36 K antigen of M. leprae was less suitable because of persistent reactivity during therapy, consequently resulting in no significant correlation with ELISA reactivities to NTO or NDO.

Evaluation of Mycobacterium leprae antigens in the serological monitoring of a clofazimine-based chemotherapeutic study of dapsone resistant lepromatous leprosy patients in Cebu, Philippines.

Thirty-one dapsone resistant lepromatous leprosy patients receiving clofazimine based therapy were serologically monitored throughout their 5-year period of treatment. Sequentially collected sera were used to examine 4 Mycobacterium leprae antigens to evaluate their usefulness in ELISA's for monitoring the progress of their therapy. The ELISA results were compared with decline in bacterial load over the treatment period and with duration of treatment. In addition the ELISA's were compared with each other. The ELISA's based on the measurement of IgM antibodies to the two neoglycoproteins (NDO and NTO) representing the phenolic glycolipid antigen of M. leprae were found to be the most effective with regard to monitoring treatment. A whole M. leprae based ELISA was less efficient in monitoring treatment because it failed to measure antibodies in 5 out of 31 patients. The ELISA-inhibition test based on the detection of antibodies to a species-specific epitope on the 36 K antigen of M. leprae was less suitable because of persistent reactivity during therapy.

Spot test for detection of dapsone in urine: an assessment of its validity and interpretation in monitoring dapsone self-administration.

This study aimed to assess the validity and interpretation of the spot test for monitoring dapsone self-administration that employs filter paper impregnated with a modified Ehrlich's reagent. Urine specimens obtained from 20 volunteers, who took 100 mg dapsone for four days in succession, were investigated by this test. Findings indicate that spot tests will be negative after an average of three missed doses of dapsone, if compared with a standard of 5 micrograms dapsone per ml of urine. No negative spots are expected in fully compliant patients, and no positive spots are expected in patients who did not take dapsone for a week or longer. In the context of the treatment goal, it is argued that this degree of sensitivity makes the spot test a valid tool for the monitoring and management of patient compliance in leprosy control programs.

Evaluation of a new blood test for its potential to indicate leprosy infection prior to the appearance of clinical symptoms.

A test is described that utilized a laser nephelometric measure of the interaction between human serum and a leprosy biopsy suspension to demonstrate household contact with a leprosy index case. None of the test sera was from persons with clinical evidence of the disease. There was a 5:1 ratio of higher level reactors in sera from household contacts vs high level reactors in sera from persons in the surrounding community. This did not appear to be a result of age, sex, family relationship to the index case, or clinical character of the index case. Some index cases had high level serum reactors among their contacts; others did not. This phenomenon was not a function of the clinical classification of the index case. The reason is unknown. This test should provide another practical means to study leprosy.