Leprosy--in pursuit of a vaccine.

Clinical leprosy is characterized by varying manifestations between tuberculoid and lepromatous leprosy. In the former state the patient is able to elicit a cell-mediated immune response whereas in the latter, there is usually a humoral response. An understanding of this immunological balance is crucial in the search for a vaccine which will control the disease. The development of a possible anti-Mycobacterium leprae vaccine has been advanced by the isolation of organisms from the infected tissues of the nine-banded armadillo, Dasypus novemcinctus; 125 000 doses can be prepared from one animal. In addition, recent studies on the biochemical activities of these organisms may provide the knowledge required to allow cultivation on a laboratory medium. Eventually it may be possible to produce a combined leprosy:tuberculosis vaccine for use in those parts of the world where both diseases are prevalent.