title: Indigenous evolution of Plasmodium falciparum pyrimethamine resistance multiple times in Africa.
abstract: OBJECTIVE
  Resistance to pyrimethamine in Plasmodium falciparum is conferred by mutations in the gene encoding dihydrofolate reductase (DHFR). It is known that DHFR double mutants have evolved independently in multiple geographic areas, whereas the triple mutant prevalent in Africa appears to have originated in south-east Asia. In this study, we investigated whether other triple mutants may have evolved independently in Africa.
  
  
  METHODS
  We determined the DHFR genotypes and haplotypes of five microsatellite loci flanking the DHFR locus between 4.49 kb upstream and 1.48 kb downstream of 159 isolates collected from three African countries (Republic of Congo, Ghana and Kenya).
  
  
  RESULTS
  The CIRNI type of DHFR triple mutant (with mutations underlined at amino acid positions 51, 59 and 108) was predominant in the Republic of Congo (82%) and Ghana (81%) and was the second most prevalent in Kenya (27%), where the CICNI type of DHFR double mutant was dominant. Three distinct microsatellite haplotypes were identified in the DHFR triple mutant. One haplotype was identical to that originating in south-east Asia. The other two haplotypes occurred in Ghana and Kenya, which were unique, previously undescribed and identical to those of the two DHFR double mutants found in the same locations.
  
  
  CONCLUSIONS
  This study presents strong evidence for the unique, multiple independent evolution of pyrimethamine resistance in Africa. Indigenous evolution of the triple mutant from the double mutant appears to have occurred in a step-wise manner in Kenya and Ghana or in nearby countries in east and west Africa.
authors.affiliation: Department of International Affairs and Tropical Medicine, Tokyo Women's Medical University, 9-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan. hiro-tm@research.twmu.ac.jp
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Mita
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Tanabe
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Takahashi
authors.forename: Richard
authors.initials: R
authors.lastname: Culleton
authors.forename: Mathieu
authors.initials: M
authors.lastname: Ndounga
authors.forename: Mawuli
authors.initials: M
authors.lastname: Dzodzomenyo
authors.forename: Willis S
authors.initials: WS
authors.lastname: Akhwale
authors.forename: Akira
authors.initials: A
authors.lastname: Kaneko
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Kobayakawa
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D000962:Antimalarials / Q000494:pharmacology*; D003223:Congo; D016172:DNA Fingerprinting; D016054:DNA, Protozoan / Q000235:genetics; D004351:Drug Resistance; D005838:Genotype; D005869:Ghana; D006801:Humans; D007630:Kenya; D016778:Malaria, Falciparum / Q000469:parasitology*; D018895:Microsatellite Repeats; D020125:Mutation, Missense; D010963:Plasmodium falciparum / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D015800:Protozoan Proteins / Q000235:genetics; D011739:Pyrimethamine / Q000494:pharmacology*; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics
chemical_list: D000962:Antimalarials; D016054:DNA, Protozoan; D015800:Protozoan Proteins; D013762:Tetrahydrofolate Dehydrogenase; D011739:Pyrimethamine