EPIDEMIOLOGIC STUDIES IN CHILDREN OF A LOW-ENDEMIC REGION, A HIGH-ENDEMIC REGION, AND DWELLERS OF A LEPROSY COLONY - EVALUATION OF ANTI-ND-BSA ANTIBODIES AND LEPROMIN RESPONSE

Children residing in a low-endemic region (LER), a high-endemic region (HER), and a leprosy colony contact population (CP) were evaluated fo r lepromin response as well as reactivity to the Mycobacterium leprae- specific synthetic antigen, ND-BSA. The mean reactivity to ND-BSA in t he LER group (OD 0.03 +/- 0.03, N = 71) was significantly lower (p < 0 .001) than that in the contact population (OD 0.14 +/- 0.09, N = 140) as well as the population residing in the HER (OD 0.09 +/- 0.08, N = 1 340). ELISA-positive results were the highest (21.4%) with the CP grou p and lowest (0.0%) in the LER group, suggesting that it was a measure of the extent of exposure to M. leprae. In the contact population, fe males showed a preponderance for ELISA positivity over males (p < 0.00 5), a finding not observed with the HER population. The Mitsuda respon ses showed a Gaussian-type distribution in all of the three population s examined with the mean response being highest in the LER (6.0 mm +/- 2.9) and lowest in the HER (4.5 mm +/- 2.0) groups. The percent posit ivity for the Mitsuda reaction was found to be highest in the LER (93. 0%) and lowest in the HER (88.3%) groups. The Mitsuda response thus ap pears to be independent of M. leprae exposure, and its interpretation in a given population needs consideration of several factors, such as nutritional, environmental, etc. The percent positivity as well as the mean Fernandez response was found to be highest in the LER (52.1%, 5. 5 +/- 4.6) and lowest in the HER (24.4%, 3.1 +/- 3.0) groups, indicati ng more of a reflection of an individual immunological response rather than a prior exposure to M. leprae. The humoral and cell-mediated imm une responses (Mitsuda) in the same individual showed a poor correlati on between the two in all three groups studied. However, the percent-p ositive ELISA results associated et une with lepromin-negative individ uals in the CP group was significantly higher (5/12, 41.7%) than that observed in HER group (10/156, 6.4%). The clinical utility and the pre dictive value of the two tests along with the cost-effectiveness for t he outcome of the disease need close and longer follow-up studies.