Honing in on malaria parasites

Two research groups present the genome sequences of the human malaria parasites Plasmodium knowlesi and Plasmodium vivex in this week’s issue of Nature. Published six years after the completion of the genome of Plasmodium falciparum, the species that causes the most severe form of human malaria, the sequences reveal how differences in genetic make-up may shape the specific biology of each species.

Only some of the many species of Plasmodium infect humans, and different species cause malaria of varying degrees of severity. Plasmodium knowlesi is a monkey parasite that is increasingly recognized as a significant cause of human malaria.

In sequencing the genome of P. knowlesi, Arnab Pain of the Wellcome Trust Sanger Institute, UK, and an international team of researchers have found that one family of parasite genes shares common amino acid sequences with a host protein. They suggest that this could represent an unusual form of mimicry, whereby the parasite impersonates the host to avoid detection. According to the researchers, their findings reinforce the notion that malaria parasites have evolved specific mechanisms to enhance survival within their respective hosts.

Jane Carlton of The Institute for Genomic Research/J. Craig Venter Institute, USA, and her international team of researchers have sequenced the genome of P. vivax — the most widespread of all the malaria parasites and the most common cause of benign but recurring malaria. It is responsible for 25–40% of some 515 million annual cases of malaria worldwide, write the researchers.

By comparing the P. vivax sequence with all the other sequenced Plasmodium genomes, Carlton and co-workers have revealed novel gene families and potential alternative invasion pathways not recognized previously. The research offers insight as to why some species are more dangerous than others, and, note the researchers, provides a valuable resource to the scientific community.

In a supporting review article, Elizabeth Winzeler of the Genomics Institute of the Novartis Research Foundation and The Scripps Research Institute, USA, comments that: “Considering the impact that malaria parasites have had on human health it seems remarkable that we know as little as we do.” She discusses the impact that the Plasmodium genome sequences have had and will have on the hunt for much-needed new therapeutics.