Polymorphism in the gene encoding the apical membrane antigen-1 (AMA-1) ofPlasmodium falciparum. X. Asembo Bay Cohort Project

We have investigated the genetic diversity of the gene encoding the apical membrane antigen-1 (AMA-1) in natural populations of Plasmodium falciparum from western Kenya and compared it with parasite populations from other geo graphic regions. A total of 28 complete sequences From Kenya. Thailand, Ind ia. and Venezuela field isolates were obtained. The genetic polymorphism is not evenly distributed across the gene. which is in agreement with the pat tern reported in earlier studies. The alleles from Kenya exhibit 20 and 30% , more polymorphism than that found in Southeast Asia and Venezuelan allele s. respectively. Based on the gene genealogies derived from sequencing data , no evidence for allele families was found. We have found evidence support ing limited gene flow between the parasite populations. specifically. betwe en the Southeast Asian and Venezuelan isolates; however, no alleles could b e linked to a specific geographic region. This study reveals that positive natural selection is an important factor in the maintenance of genetic dive rsity for AMA-I. We did not find conclusive evidence indicating intragenic recombination is important in the generation of the AMA-I allelic diversity . The study provides information on the genetic diversity of the AMA-1 gene that would be useful in vaccine development and testing. as well as in ass essing factors that are involved in the generation and maintenance of the g enetic diversity in P. falciparium. (C) 2001 Published by Elsevier Science B.V.