Leishmaniasis: current status of vaccine development

Abstract

Leishmaniasis, a spectrum of diseases caused by various forms of Leishmania has become a major health problem all over the world. Vaccination against leishmaniasis has passed through many developmental stages beginning with the ancient practice of 'leishmanization'. Due to various problems and difficulties associated with traditional vaccines, the interest has been shifted to novel approaches of vaccination like DNA vaccination, vaccination with live vectors encoding leishmanial antigens and finally to designer vaccines. In an effort towards developing an anti-leishmanial vaccine, our laboratory has been working on various genes present in an amplified locus of Leishmania known as the 'LD1 locus'. Two genes, ORFF and BT1 (previously ORFG), are part of the multigenic LD1 locus on chromosome 35. BT1 encodes a biopterin transporter, while the function of ORFF gene product is unknown. Immunization of mice with recombinant ORFF (rORFF) and BT1 proteins, individually, or in combination, conferred partial protection against challenge with Leishmania donovani. We also tested the protective efficacy of ORFF DNA vaccine in BALB / c mice model and found that the level of protection was significantly higher than that of ORFF protein. Protection conferred by ORFF DNA vaccine correlated with significant levels of in vitro splenocyte proliferation and low levels of antigenspecific antibodies. There was a preferential production of IFN-γ compared to IL-4, which indicated the induction of a protective Th1 response, by the DNA vaccine. Thus, DNA immunization may offer an attractive alternative strategy against leishmaniasis. We present here the current status of vaccine development against leishmaniasis.