Leprosy

Growing out of the successful transmission of leprosy to armadillos, making available large quantities of M. leprae, there have been remarkable recent advances in the knowledge of the leprosy bacillus. These bacilli and their isolated chemical constituents provide organisms for in vitro testing of new drugs, reagents for the study of the immunologic dysfunction in leprosy patients, development of early diagnostic methods, and the preparation of candidate vaccines. Leprosy is usually transmitted by the nasorespiratory route, but occasionally, there is transplacental infection. There are reports suggesting that patients have acquired leprosy by contact with wild M. leprae-infected armadillos in Louisiana and Texas. Perturbations in lymphocyte-macrophage interaction appear to be most closely related to the defective CMI in leprosy. The helper T/suppressor T cell populations vary markedly in lesions of the various forms of leprosy, with enhanced suppression of T-cell activity in lepromatous disease. Infiltration of IL-2 and gamma-interferon seems to stimulate CMI in situ in lesions of lepromatous leprosy. Vaccination of lepromatous patients with a killed M. leprae-plus-BCG preparation stimulates CMI and clears tissues of leprosy bacilli, providing an immunotherapeutic approach to the management of leprosy. Immunoprophylactic vaccine trials are in progress, and initial results should be available in 1991. Because of drug resistance, dapsone monotherapy of leprosy is no longer recommended. Multidrug regimens, composed of dapsone, rifampin, and clofazimine or a thioamide, are now required and appear to reduce the incidence of leprosy when applied assiduously. Newer experimental drugs that may eventually be included in these regimens include the fluoroquinolones, minocycline, and clarithromycin. There is no clear evidence that the early serologic diagnosis of leprosy is generally applicable. Favorable response to therapy in multibacillary patients, however, may be assessed by noting drops in levels of M. leprae-specific antigens in blood and urine and, to a lesser extent, levels of specific antibodies in serum. There are conflicting reports on the influence of AIDS on leprosy. There are no convincing data showing that AIDS and leprosy affect each other. Although chemotherapy offers the best current hope for the control of leprosy, effective immunoprophylaxis and improved socioeconomic conditions in endemic areas are thought to be essential in programs for the eradication of leprosy.