title: Diversity of Plasmodium falciparum chloroquine resistance transporter (pfcrt) exon 2 haplotypes in the Pacific from 1959 to 1979.
abstract: Nearly one million deaths are attributed to malaria every year. Recent reports of multi-drug treatment failure of falciparum malaria underscore the need to understand the molecular basis of drug resistance. Multiple mutations in the Plasmodium falciparum chloroquine resistance transporter (pfcrt) are involved in chloroquine resistance, but the evolution of complex haplotypes is not yet well understood. Using over 4,500 archival human serum specimens collected from 19 Pacific populations between 1959 and 1979, the period including and just prior to the appearance of chloroquine treatment failure in the Pacific, we PCR-amplified and sequenced a portion of the pfcrt exon 2 from 771 P. falciparum-infected individuals to explore the spatial and temporal variation in falciparum malaria prevalence and the evolution of chloroquine resistance. In the Pacific, the prevalence of P. falciparum varied considerably across ecological zones. On the island of New Guinea, the decreases in prevalence of P. falciparum in coastal, high-transmission areas over time were contrasted by the increase in prevalence during the same period in the highlands, where transmission was intermittent. We found 78 unique pfcrt haplotypes consisting of 34 amino acid substitutions and 28 synonymous mutations. More importantly, two pfcrt mutations (N75D and K76T) implicated in chloroquine resistance were present in parasites from New Hebrides (now Vanuatu) eight years before the first report of treatment failure. Our results also revealed unexpectedly high levels of genetic diversity in pfcrt exon 2 prior to the historical chloroquine resistance selective sweep, particularly in areas where disease burden was relatively low. In the Pacific, parasite genetic isolation, as well as host acquired immune status and genetic resistance to malaria, were important contributors to the evolution of chloroquine resistance in P. falciparum.
authors.affiliation: Laboratory of Evolutionary Anthropology and Health, Binghamton University, Binghamton, New York, United States of America. aramidus44@gmail.com
authors.forename: Chim W
authors.initials: CW
authors.lastname: Chan
authors.forename: Rita
authors.initials: R
authors.lastname: Spathis
authors.forename: Dana M
authors.initials: DM
authors.lastname: Reiff
authors.forename: Stacy E
authors.initials: SE
authors.lastname: McGrath
authors.forename: Ralph M
authors.initials: RM
authors.lastname: Garruto
authors.forename: J Koji
authors.initials: JK
authors.lastname: Lum
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000962:Antimalarials / Q000627:therapeutic use; D002738:Chloroquine / Q000627:therapeutic use; D004351:Drug Resistance / Q000235:genetics; D005091:Exons / Q000235:genetics*; D051456:Gene Flow; D014644:Genetic Variation; D005843:Geography; D006239:Haplotypes; D006801:Humans; D016778:Malaria, Falciparum / Q000188:drug therapy / Q000453:epidemiology / Q000469:parasitology; D026901:Membrane Transport Proteins / Q000145:classification / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D010139:Pacific Islands / Q000453:epidemiology; D010219:Papua New Guinea / Q000453:epidemiology; D010802:Phylogeny; D010963:Plasmodium falciparum / Q000235:genetics* / Q000254:growth & development; D016133:Polymerase Chain Reaction; D015995:Prevalence; D015800:Protozoan Proteins / Q000145:classification / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D000962:Antimalarials; D026901:Membrane Transport Proteins; C416369:PfCRT protein, Plasmodium falciparum; D015800:Protozoan Proteins; D002738:Chloroquine