Promise of leishmaniasis treatment in parasite genes

A Leishmania parasite Copyright: Dr Laurence Tetley, University of Glasgow

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Researchers have identified a small number of genes that could guide the development of new therapies for leishmaniasis.

The study was published this week in Nature Genetics (17 June). 

Leishmaniasis is caused by the Leishmania parasite and transmitted by biting insects such as sand flies. It affects about two million people each year around the world, and as yet there is no vaccine and few effective drugs.

Christopher Peacock of the UK-based Wellcome Trust Sanger Institute, and co-workers carried out a comparison of the complete genomes of three Leishmania species — L. infantum, L. braziliensis and L. major.

The species cause a broad range of infection — from potentially life threatening systemic infection in the case of L. infantum (visceral leishmaniasis) to self-healing skin lesions caused by L. major.

Each of the three genomes contains more than 8000 genes, but the researchers found only 200 genes that differed between all three species.

This suggests that only a few genes determine disease severity in leishmaniasis, says Peacock, and that genes specific to one species are likely to be those that cause their particular set of symptoms.

Having a limited repertoire of genes to focus on will “hopefully speed up the development of new therapies for leishmaniasis”, he says.

In particular, the researchers identified a number of genes that are likely to play a role in the ability of L. infantum to cause disease in humans.

“This should provide the basis for future studies designed to identify effective drug targets or potential candidates for vaccine development,” says Peacock.

The researchers looked for genes that were evolving rapidly as these are most likely to be genes involved in defeating or disabling the host’s immune system.

Peacock told SciDev.Net that while these genes make good candidates for vaccines, they may also be useful in finding out how the parasite evades the immune system and allow scientists to more effectively predict the success of potential vaccines.

“The findings of this study are impressive,” says Swapan Jana, secretary of the India-based nongovernmental organisation, Society for Social Pharmacology.

“Leishmaniasis needs a vaccine and new treatment options. This study sheds light in both those areas. It invites further studies to find a definitive vaccine as well as new drug treatment for leishmaniasis,” he adds.

Link to article in Nature Genetics

Reference: Nature Genetics doi 10.1038/ng2053 (2007)