Leprosy vaccines – A voyage unfinished

Leprosy, a chronic granulomatous disease caused by Mycobacterium leprae , is endemic in many regions of the world. With introduction of multidrug therapy in 1982, there has been a dramatic reduction in the prevalence of leprosy, but new cases continue to appear. There have been more than 200,000 new cases per year for the past 10 years. There is a renewed interest in leprosy vaccines with immunoprophylactic and immunotherapeutic roles. Due to the difficulty in cultivating M. leprae in artificial media, vaccine strategies have centered on the use of cross-sensitizing mycobacteria. Bacillus Calmette–Guerin (BCG) has been the most popular among these, but with a widely varying protective efficacy reported from different parts of the world. In three meta-analyses, BCG has shown strong evidence of efficacy against leprosy. Recently, India has focused interest on another vaccine, Mycobacterium indicus pranii vaccine earlier known as Mycobacterium w . To overcome the limitations of these whole cell vaccines, various recombinant BCGs and subunit vaccines have been developed and studied in experimental models. These often yield inconsistent results. However, a new subunit recombinant vaccine – LepVax holds promise and has completed Phase 1a clinical trials successfully.