Effect of skin test with M. leprae soluble antigen on reaction to a subsequent test with the same antigen.

Soluble skin-test antigens (STA), produced from armadillo-derived Mycobacterium leprae by Drs. Rees and Convit, were expected to meet the long-felt need of a test for leprosy infection and also to serve as tests for measuring postvaccination sensitization induced by vaccine preparations against leprosy. The present paper reports results from two studies examining the influence, if any, of skin testing with Rees' STA on reaction to a subsequent test with the same antigen. In the first study, 2168 persons from households of leprosy patients and from neighboring households were skin tested with Rees' STA twice at an interval of 6 months. In the second study, 1700 persons, free from leprosy, received either Rees' STA or normal saline by random allocation. A random subset of 850 persons was tested with Rees' STA after 3 months. The remaining 850 persons were tested with Rees' STA after 6 months. In addition, 242 leprosy patients were given Rees' STA or normal saline by random allocation, and all of these patients were tested with Rees' STA after 6 months. The results of the two studies showed that among persons reacting with a small size of reaction to Rees' STA, the size of the reaction to the repeat test was significantly larger. However, from the results of the second study, which included a control group, it was clearly seen that the quantum of boosting or sensitizing effect of the first test as well as that of new sensitization was small over a period of 3-6 months.(ABSTRACT TRUNCATED AT 250 WORDS)