August 6, 2012
Sequenced Malaria Genome Provides Benefits, Difficulties In Finding A Cure
Brett Smith for redOrbit.com - Your Universe Online
After sequencing the genome of several malaria-related parasites, scientists found that the protozoans responsible for the deadly disease are very genetically diverse and therefore difficult to eradicate, according to their report published this week in the journal Nature Genetics.While the genomes of the four sequenced strains of Plasmodium vivax, a parasite that infects about 100 million people each year, indicated that organism´s genetic robustness, they also offered a window into how to engineer more useful treatments.
"The bad news is there is significantly more genetic variation in P. vivax than we'd thought, which could make it quite adept at evading whatever arsenal of drugs and vaccines we throw at it," said New York University biology professor Jane Carlton, who was a senior author on two somewhat related malaria studies published in the current edition of the journal.
"However, now that we have a better understanding of the challenges we face, we can move forward with a deeper analysis of its genomic variation in pursuing more effective remedies."
Carlton, along with a team of American and Indian scientists, sequenced and analyzed the genomes of four P. vivax strains collected from disparate geographic locations. Their analysis showed approximately twice as much genetic diversity along certain sections of the parasite´s genome when compared to the known genomes of Plasmodium falciparum, a malaria-causing parasite with higher mortality rates around the world.
P. falciparum parasite is highly prevalent in sub-Saharan Africa where P. vivax causes only about 10 to 20 percent of malaria-related deaths. However, outside of Africa, P. vivax accounts for half of all malaria cases and less is known about the genome of this more resilient parasite, which can stay in remission for longer and withstand cooler climates
Although P.vivax has been sequenced in the past, this latest research has resulted in the tripling of the number of genome sequences available, bringing the total to six. The study also increased the diversity of P.vivax genomes, which has proved challenging to do because of the complexity in culturing this species
The parasite´s “high genetic diversity” suggests it may be tough to develop a single vaccine that targets several different strains of P. vivax. The study´s authors wrote that this development warrants “a deeper survey of variation in P. vivax,” a “neglected but major pathogen.”
In the other Nature Genetics malaria report, Japanese and the American scientists, including Carlton, reported that they had sequenced the genomes of three strains of P. cynomolgi -- a species related to P. vivax that causes the disease in Asian Old World monkeys.
Because of genetic similarities, the information culled from the sequencing of P. cynomolgi "provides the foundation for further insights into traits... that will enhance prospects for the eventual elimination of vivax-caused malaria and global malaria eradication," according to the study´s authors.
"We have generated a genetic map of P. cynomolgi, the sister species to P. vivax, so we can now push forward in creating a robust model system to study P. vivax,” explained study co-author Kazuyuki Tanabe, a professor at Osaka University.
“This is important because we can't grow P. vivax in the lab, and researchers desperately need a model system to circumvent this.”