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.