How it began
Jacinto Convit, a physician born in Caracas in 1913, spent his career on leprosy and other tropical diseases. In the mid-1970s he developed a model of immunotherapy for leprosy that combined purified leprosy bacilli, obtained from the nine-banded armadillo, with the Bacillus Calmette-Guérin (BCG) vaccine as an adjuvant. In 1987 he added killed Mycobacterium leprae to the BCG vaccine to make a combined vaccine. He worked at the Institute of Biomedicine in Caracas, which he founded in 1984.
Before it existed
When Convit began treating leprosy patients, the only resource was chaulmoogra oil, which was poorly effective, caused nausea when swallowed and was painful when injected. In the early 1940s Convit and his team showed the efficacy of sulfones and their derivatives, and he created regional public health dermatology services that allowed patients to be treated as outpatients.
How it works
The leprosy bacillus cannot be grown in laboratory culture, so the nine-banded armadillo was used as the animal model to obtain large quantities of it. Killed bacilli purified from armadillo tissue were mixed with live BCG, the tuberculosis vaccine, which strongly stimulates cell-mediated immunity. The aim was to provoke an immune response against the leprosy bacillus in people whose own defenses did not react to it. Convit had earlier been commissioned by the World Health Organization, in 1960, to run a drug evaluation program for parasitic diseases, and in 1971 to direct its committee on the classification of leprosy.
What changed first
The work brought Convit the Prince of Asturias Award for Scientific and Technical Research in 1987, and the Venezuelan government nominated him for a Nobel Prize in 1988. The combined vaccine was tested worldwide but was not found to be more effective than regular BCG alone.
What lasted
The same model was applied to leishmaniasis, and that approach has given thousands of patients access to therapy during shortages of antimonial drugs, at far lower cost and with comparable efficacy. Convit's regional dermatology services were extended to leishmaniasis and onchocerciasis and were copied in national health programs elsewhere in Latin America. He died in Caracas in 2014 at the age of 100.
