Researchers have decoded the genomes of two different malaria parasites that plague people in Southeast Asia and South America, and say the new information will boost efforts to find a vaccine for the mosquito-borne disease. The work builds on the sequencing of the first malaria genome six years ago, when scientists tackled the most deadly malaria parasite, Plasmodium falciparum, which is endemic in Africa.
By comparing the genetics of Plasmodium falciparum to that of the newly sequenced species, P. knowlesi and P. vivax, the two teams have begun to identify the different mechanisms by which each species maximizes its chances of evading the host immune system [The Scientist].
P. vivax is the main cause of malaria in Latin America and Southeast Asia, and although it's rarely deadly researchers say it still causes plenty of misery. It's also challenging to eradicate because it can lie dormant in the liver for months.
"It makes people very sick," says lead researcher Jane Carlton.... "It can come out of the liver weeks or months after the initial mosquito bite. That makes it a very serious risk to human health." Vivax malaria is so debilitating that sufferers, most of whom are poor, can't support themselves or their families. "Vivax is one of the stealth reasons that poor people can't escape poverty," says [tropical disease expert] Peter Hotez [USA Today].
Two separatepapers, both published in Nature [subscription required], describe the genomes of the two parasites, and call attention to some genes that could figure into the parasites' defenses against host immune systems. While researchers didn't discover the mechanism that allows P. vivax to lie dormant, they did find genes that may be involved in the process.
"We found genes in the P. vivax genome that seem to be related to genes found in dormant stages in other organisms such as yeast," Carlton explained. "This is like a first foot on the ladder" [National Geographic].
The other parasite, P. knowlesi, primarily infected monkeys in the past, but in recent years it has been making inroads in human populations in Southeast Asia. In one unexpected finding, researchers discovered that the P. knowlesi genome
contained sequences closely resembling the genes for two human proteins that regulate immune response. The parasite may trick its human host by mimicking its immune system proteins [The Scientist].
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Image: flickr/naturegirl 78