title: Single nucleotide polymorphisms in Plasmodium falciparum V type H(+) pyrophosphatase gene (pfvp2) and their associations with pfcrt and pfmdr1 polymorphisms.
abstract: BACKGROUND
  Chloroquine resistance in Plasmodium falciparum malaria has been associated with pfcrt 76T (chloroquine resistance transporter gene) and pfmdr1 86Y (multidrug resistance gene 1) alleles. Pfcrt 76T enables transport of protonated chloroquine out of the parasites digestive vacuole resulting in a loss of hydrogen ions (H(+)). V type H(+) pyrophosphatase (PfVP2) is thought to pump H(+) into the digestive vacuole. This study aimed to describe the geographic distribution of single nucleotide polymorphisms in pfvp2 and their possible associations with pfcrt and pfmdr1 polymorphisms.
  
  
  METHODS
  Blood samples from 384 patients collected (1981-2009) in Honduras (n=35), Colombia (n=50), Liberia (n=50), Guinea Bissau (n=50), Tanzania (n=50), Iran (n=50), Thailand (n=49) and Vanuatu (n=50) were analysed. The pfcrt 72-76 haplotype, pfmdr1 copy numbers, pfmdr1 N86Y and pfvp2 V405I, K582R and P711S alleles were identified using PCR based methods.
  
  
  RESULTS
  Pfvp2 was amplified in 344 samples. The pfvp2 allele proportions were V405 (97%), 405I (3%), K582 (99%), 582R (1%), P711 (97%) and 711S (3%). The number of patients with any of pfvp2 405I, 582R and/or 711S were as follows: Honduras (2/30), Colombia (0/46), Liberia (7/48), Guinea-Bissau (4/50), Tanzania (3/48), Iran (3/50), Thailand (1/49) and Vanuatu (0/31). The alleles were most common in Liberia (P=0.01) and Liberia+Guinea-Bissau (P=0.01). The VKP haplotype was found in 189/194 (97%) and 131/145 (90%) samples harbouring pfcrt 76T and pfcrt K76 respectively (P=0.007).
  
  
  CONCLUSIONS
  The VKP haplotype was dominant. Most pfvp2 405I, 582R and 711S SNPs were seen where CQ resistance was not highly prevalent at the time of blood sampling possibly due to greater genetic variation prior to the bottle neck event of spreading CQ resistance. The association between the pfvp2 VKP haplotype and pfcrt 76T, which may indicate that pfvp2 is involved in CQ resistance, should therefore be interpreted with caution.
authors.affiliation: Malaria Research, Infectious Diseases Unit, Department of Medicine Solna, Karolinska University Hospital/Karolinska Institutet, Retzius väg 10, 171 77 Stockholm, Sweden; Departamento de Parasitología, Escuela de Microbiología, Facultad de Ciencias, Universidad Nacional Autónoma de Honduras (UNAH), Tegucigalpa, Honduras. Electronic address: irina.jovel@ki.se.
authors.forename: Irina Tatiana
authors.initials: IT
authors.lastname: Jovel
authors.affiliation: Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden; School of Biological Sciences, Nanyang Technological University, Singapore. Electronic address: pedroemferreira@gmail.com.
authors.forename: Pedro Eduardo
authors.initials: PE
authors.lastname: Ferreira
authors.affiliation: Malaria Research, Infectious Diseases Unit, Department of Medicine Solna, Karolinska University Hospital/Karolinska Institutet, Retzius väg 10, 171 77 Stockholm, Sweden; Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal. Electronic address: maria.isabel.veiga@gmail.com.
authors.forename: Maria Isabel
authors.initials: MI
authors.lastname: Veiga
authors.affiliation: Malaria Research, Infectious Diseases Unit, Department of Medicine Solna, Karolinska University Hospital/Karolinska Institutet, Retzius väg 10, 171 77 Stockholm, Sweden; Department of Biomedical Sciences and Veterinary Public Health, Section of Virology, Swedish University of Agricultural Sciences, Uppsala, Sweden. Electronic address: malmberg.maja@gmail.com.
authors.forename: Maja
authors.initials: M
authors.lastname: Malmberg
authors.affiliation: Malaria Research, Infectious Diseases Unit, Department of Medicine Solna, Karolinska University Hospital/Karolinska Institutet, Retzius väg 10, 171 77 Stockholm, Sweden; Global Health, Department of Public Health Sciences, Karolinska Institutet, Stockholm, Sweden. Electronic address: andreas.martensson@ki.se.
authors.forename: Andreas
authors.initials: A
authors.lastname: Mårtensson
authors.affiliation: Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden. Electronic address: akira.kaneko@ki.se.
authors.forename: Akira
authors.initials: A
authors.lastname: Kaneko
authors.affiliation: Malaria and Vector Research Group, Biotechnology Research Center, Pasteur Institute of Iran, Iran. Electronic address: zakeris@yahoo.com.
authors.forename: Sedigheh
authors.initials: S
authors.lastname: Zakeri
authors.affiliation: Centro Internacional de Entrenamiento e Investigaciones Médicas, Cali, Colombia. Electronic address: claribel_murillo@cideim.org.co.
authors.forename: Claribel
authors.initials: C
authors.lastname: Murillo
authors.affiliation: Shoklo Malaria Research Unit, Mae Sot Tak, Thailand; Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand; Nuffield Department of Clinical Medicine, Centre for Clinical Vaccinology and Tropical Medicine, University of Oxford, Oxford, United Kingdom. Electronic address: francois@tropmedres.ac.
authors.forename: Francois
authors.initials: F
authors.lastname: Nosten
authors.affiliation: Malaria Research, Infectious Diseases Unit, Department of Medicine Solna, Karolinska University Hospital/Karolinska Institutet, Retzius väg 10, 171 77 Stockholm, Sweden. Electronic address: anders.bjorkman@karolinska.se.
authors.forename: Anders
authors.initials: A
authors.lastname: Björkman
authors.affiliation: Malaria Research, Infectious Diseases Unit, Department of Medicine Solna, Karolinska University Hospital/Karolinska Institutet, Retzius väg 10, 171 77 Stockholm, Sweden. Electronic address: johan.ursing@karolinska.se.
authors.forename: Johan
authors.initials: J
authors.lastname: Ursing
mesh_terms: D000328:Adult; D000483:Alleles; D000962:Antimalarials; D001483:Base Sequence; D002648:Child; D002738:Chloroquine / Q000378:metabolism / Q000627:therapeutic use; D016054:DNA, Protozoan / Q000235:genetics; D004351:Drug Resistance / Q000235:genetics*; D008040:Genetic Linkage; D006239:Haplotypes; D006801:Humans; D043564:Inorganic Pyrophosphatase / Q000235:genetics*; D016778:Malaria, Falciparum / Q000469:parasitology; D026901:Membrane Transport Proteins / Q000235:genetics*; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics*; D010963:Plasmodium falciparum / Q000145:classification / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D015800:Protozoan Proteins / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D000962:Antimalarials; D002738:Chloroquine; D016054:DNA, Protozoan; D043564:Inorganic Pyrophosphatase; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D015800:Protozoan Proteins; C513498:Mdr1 protein, Plasmodium falciparum; C416369:PfCRT protein, Plasmodium falciparum
keywords: Chloroquine; Malaria; P. falciparum; Pfcrt; Pfmdr1; Pfvp2; Resistance