Genome Of Parasite That Causes Relapsing Malaria Decoded

Led by a parasitologist from NYU Langone Medical Center, Jane Carlton, PhD, some 40 researchers sequenced the genome of Plasmodium vivax (P. vivax), one of four malaria parasites that routinely affect humans. P. vivax, which is increasingly resistant to some antimalarial drugs, is the species most common outside Africa, particularly in Asia and the Americas, including the United States, the site of periodic outbreaks.

Vivax malaria, as it is known, is believed more robust and resilient than its cousin, the more deadly malaria species, P. falciparum – and is thus more difficult to eradicate. Distinctively, vivax malaria can be transmitted by mosquitoes in cooler temperatures. It also has a dormant stage that enables it to re-emerge as climates warm, causing "relapses" of the disease months and even years after a first attack.

Symptoms for the two strains of malaria are similar – flu-like, featuring fever and abdominal pain, often leading to severe anemia – and, in children, lifelong learning disabilities. Malaria is a disease of poorer populations, and overall is estimated annually to kill more than a million people worldwide.

Researchers also identified several pathways in the P. vivax parasite that could eventually be targets for drug treatment. Both P. vivax and P. falciparum vivax are also being studied to identify potential vaccine targets.

The research is regarded as all the more significant in that P. vivax has long remained little-researched, little-known and little-understood. Such neglect is mainly due to the focus on the more deadly malaria species, P. falciparum -- P. vivax is seldom lethal -- and also because the parasite cannot be grown in a lab setting. Further, the growing burden of vivax malaria will complicate efforts to control P. falciparum in areas where the two coincide.

Indeed, the project that led to the landmark genetic decoding was in the works for a total of six years, involving researchers from England, Spain, Australia and Brazil as well as the United States. After two years, remaining funds from the P. falciparum genome project were exhausted, and funding from the Burroughs Wellcome Fund and the National Institutes of Health allowed its completion.

P. vivax is the second species of human malaria parasite to be sequenced. Researchers found the genome for P. vivax dramatically different from the genomes of three other sequenced malaria parasites – different in content, structure and complexity. They used whole genome shotgun methods to produce high-quality sequences that will enable malaria researchers worldwide to undertake further research on the parasite. The next step is to sequence six other P. vivax genomes – from Brazil, Mauritania, India, North Korea and Indonesia -- to identify novel vaccine candidates and generate an evolutionary map of the species.

"This project is a tribute to the collegiality and tenacity of the vivax malaria community," says Jane M. Carlton, associate professor at NYU School of Medicine's Department of Medical Parasitology, who led a team of investigators from around the world. "They have persevered despite financial tribulations and lack of interest to generate an invaluable resource. These findings will be used by all malariologists for years to come to advance scientific investigation into this neglected species."

"The availability of genome sequence data has great potential to accelerate the identification and development of novel vaccines and therapeutics against this major human pathogen," says Claire Fraser-Liggett, PhD, director of the Institute of Genomic Sciences at University of Maryland School of Medicine and formerly president of The Institute for Genomic Research, Rockville Maryland where the project began. "Dr. Carlton is to be congratulated for her leadership role in bringing this project to completion."

"Unveiling the full genome sequence of Plasmodium vivax is a tremendous advance – a huge step forward in parasite biology and the fight against malaria," says Nick White, MD, professor of tropical medicine, Oxford University, England and Mahidol University, Thailand.