The Plasmodium vivax parasite appears to be rapidly evolving to overcome resistance conferred by a specific blood type found among millions of people in Africa, researchers reported at the annual meeting of the American Society of Tropical Medicine and Hygiene.
More than 95% of the population in sub-Saharan Africa lacks the Duffy blood group protein in their red blood cells, which is considered a protective mechanism against P. vivax malaria. However, a growing number of people in Africa and South America who are Duffy-negative have developed P. vivax malaria.
“We discovered previously unknown genetic mechanisms in the P. vivax parasite that could give it other ways to invade red blood cells and help explain why we are seeing these P. vivax malaria infections in people who are Duffy-negative,” Peter Zimmerman, PhD, of Case Western Reserve University, said in a press release.
Zimmerman and colleagues conducted two studies, both of which will also be published in PLoS Neglected Tropical Diseases, to look for possible mechanisms causing the increase of P. vivax malaria among Duffy-negative individuals. The first study took place in parasites collected from Madagascar, where there has been a high rate of these infections.
After performing genome sequencing, they found two copies of the gene that encodes the parasite’s Duffy-binding protein. They analyzed blood samples from people around the world and found that this duplication also is found in other areas where P. vivax malaria is common, but its highest prevalence is in Madagascar. In Cambodia, less than 10% of the samples had the duplicate gene, whereas in Madagascar, more than 50% of the samples had the duplicate gene.
“It was particularly striking that most of the parasites that contained the duplicate gene came from areas where we see the population divided between Duffy-positive and Duffy-negative individuals,” David Serre, PhD, of the Cleveland Clinic’s Genomic Medicine Institute, said in the press release.
In the second study, researchers analyzed the genome of a P. vivax parasite from Cambodia. Previously, they identified an unknown gene that had the features of a red blood cell invasion protein. In this investigation, they found that the gene is present in contemporary P. vivax parasites around the world. However, it was not found in the P. vivax parasite sequenced in 2008, which was used as the reference genome to study the parasite.
For more information:
Hester J. #1319. Presented at: American Society of Tropical Medicine and Hygiene Annual Meeting; Nov. 13-17; Washington, D.C.
Disclosure: Zimmerman and Serre report no relevant financial disclosures.