Reduced infectivity of a Leishmania donovani biopterin transporter genetic mutant and its use as an attenuated strain for vaccination.

Pterins are essential for the growth of Leishmania species, and recent work has led to the isolation of the biopterin transporter BT1. In this study, we inactivated the Leishmania donovani biopterin transporter BT1 by gene disruption mediated by homologous recombination. No transport of biopterin was detected in this mutant. The L. donovani BT1 null mutant showed a much lesser capacity for inducing infection in mice than wild-type parasites and could elicit protective immunity in mice susceptible to infection against a L. donovani challenge. Splenocytes isolated from mice immunized with the BT1 null mutant parasites produced significant amounts of interferon gamma following stimulation with L. donovani promastigotes as measured by enzyme-linked immunosorbent assay and enzyme-linked immunospot assays. Overall, these results show that by genetically manipulating the pterin transport in L. donovani, it is possible to generate an attenuated organism that could be part of a vaccination strategy.