Study On Genetic Diversity Of Plasmodium AMA-1among Different Strain

【Objective】Study on the genetic diversity of Plasmodium falciparum apical membraneantigen1(PfAMA-1) and the genetic diversity of Plasmodium vivax apical membraneantigen1(PvAMA-1) to understand the genetic polymorphism and distribution atAMA-1. Explore the reasons of maintaining genetic polymorphism at AMA-1, whichshould be make a molecular genetics basis for further understanding theepidemiological characteristics of malaria, prevention and control measures ofmalaria and vaccine development using this antigen.【Methods】After patients infected by plasmodium were confirmed by microscopy, filterblood samples were collected from patients who attended. The individual informationof malaria cases were registered detailly. DNA was extracted from filter bloodsamples using Na2HPO4method, nested PCR was employed for amplification thedomainⅡ of plasmodium vivax AMA-1and domainⅠ of Plasmodium falciparumAMA-1. The PCR products were Electrophoresed on agarose gel. Then PCR productswhich had the right DNA band were purified and sequenced. The sequenced resultwas analyzed using biosoftware.【Results】Analyses of all23PfAMA-1sequences resulted into total18haplotypes, where8haplotypes were not found in the GenBank database. we found32segregating siteand the value of nucleotide diversity was0.02501±0.00099.The average difference ofdN-dS for all23PfAMA-1sequences was0.031±0.006and All neutrality tests werenot significant. The minimum number of recombination events (Rm) was10. The LDindex R2evidently declined with increasing nucleotide distance. Analyses of all17PvAMA-1sequences resulted into total9haplotypes, whereonly1haplotype was new and not found in the GenBank database. we found9segregating site and the value of nucleotide diversity was0.00859±0.00093.Theaverage difference of dN-dS for all17PvAMA-1sequences was-0.00230±0.00539and All neutrality tests were not significant. The minimum number of recombinationevents (Rm) was2. For the entire411bp sequence, the declining trend of LD index R2was not obvious with increasing nucleotide distance.【Conclusions】DomainⅠof pfAMA-1displays high genetic diversity and haplotype diversity.So it can be used as molecular maker for studing Plasmodium falciparum, and it hasthe reference significance to the understanding of the genetic characterization ofPlasmodium falciparum.Genetic polymorphism at the domainⅠof PfAMA-1maybemaintained by natural selection and intragenic recombination.Domain Ⅱof PvAMA-1show lower genetic diversity and haplotype diversitythan domainⅠ. There is little difference among different geographical strains, so it islittle significance to use this molecular maker to understand the genetic characteristicsof Plasmodium vivax. There maybe negative selection happened in domain ⅡofPvAMA-1, and very little meiotic recombination occurring at this domain.The result of this research could provide a molecular genetics basis for furtherunderstanding the epidemiological characteristics of malaria, prevention and controlmeasures of malaria and vaccine development using this antigen.