Recent advances in experimental leprosy.

Within the last 15 years we have learned to identify Mycobacterium leprae, determine its viability, screen the efficacy of antileprosy drugs, and monitor the bacilli for drug sensitivity. We have evidence that subclinical infections occur frequently among contacts of patients with leprosy and that the different manifestations of leprosy reflect differences in resistance to M leprae. We are developing hypotheses about the mechanism of these differences. We have experimentally transmitted lepromatous leprosy to normal armadillos, and from these we can obtain amounts of leprosy bacilli which fully substitute for harvests from in vitro cultures. Furthermore, if susceptibility of armadillos can be determined without infecting them and if we can breed them under controlled conditions, we would have an animal model for investigating fundamental and applied areas of leprosy which otherwise are intractable. How much our knowledge has advanced is illustrated by a project of the World Health Organization which calls for the preparation of pure, specific antigens from the now available abundance of leprosy bacilli, which might become valuable as diagnostic and epidemiologic tools and as immunoprophylactic and even immunotherapeutic weapons.