Genetic diversity, haplotypes and allele groups of Duffy binding protein (PkDBPαII) of Plasmodium knowlesi clinical isolates from Peninsular Malaysia.
BACKGROUND
The monkey malaria parasite Plasmodium knowlesi is now recognized as the fifth species of Plasmodium that can cause human malaria. Like the region II of the Duffy binding protein of P. vivax (PvDBPII), the region II of the P. knowlesi Duffy binding protein (PkDBPαII) plays an essential role in the parasite's invasion into the host's erythrocyte. Numerous polymorphism studies have been carried out on PvDBPII, but none has been reported on PkDBPαII. In this study, the genetic diversity, haplotyes and allele groups of PkDBPαII of P. knowlesi clinical isolates from Peninsular Malaysia were investigated.


METHODS
Blood samples from 20 knowlesi malaria patients and 2 wild monkeys (Macaca fascicularis) were used. These samples were collected between 2010 and 2012. The PkDBPαII region of the isolates was amplified by PCR, cloned into Escherichia coli, and sequenced. The genetic diversity, natural selection and haplotypes of PkDBPαII were analysed using MEGA5 and DnaSP ver. 5.10.00 programmes.


RESULTS
Fifty-three PkDBPαII sequences from human infections and 6 from monkeys were obtained. Comparison at the nucleotide level against P. knowlesi strain H as reference sequence showed 52 synonymous and 76 nonsynonymous mutations. Analysis on the rate of these mutations indicated that PkDBPαII was under purifying (negative) selection. At the amino acid level, 36 different PkDBPαII haplotypes were identified. Twelve of the 20 human and 1 monkey blood samples had mixed haplotype infections. These haplotypes were clustered into 2 distinct allele groups. The majority of the haplotypes clustered into the large dominant group.


CONCLUSIONS
Our present study is the first to report the genetic diversity and natural selection of PkDBPαII. Hence, the haplotypes described in this report can be considered as novel. Although a high level of genetic diversity was observed, the PkDBPαII appeared to be under purifying selection. The distribution of the haplotypes was skewed, with one dominant major and one minor group. Future study should investigate PkDBPαII of P. knowlesi from Borneo, which hitherto has recorded the highest number of human knowlesi malaria.
Department of Parasitology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia. fongmy@um.edu.my.
Mun-Yik
MY
Fong
Yee-Ling
YL
Lau
Phooi-Yee
PY
Chang
Claudia Nisha
CN
Anthony
D000595:Amino Acid Sequence; D000818:Animals; D014644:Genetic Variation; D006239:Haplotypes; D006801:Humans; D008252:Macaca fascicularis; D008288:Malaria / Q000453:epidemiology / Q000469:parasitology / Q000662:veterinary*; D008296:Malaysia; D008969:Molecular Sequence Data; D016790:Plasmodium knowlesi / Q000235:genetics / Q000378:metabolism*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D012641:Selection, Genetic
D015800:Protozoan Proteins