Plasmodium vivax, a protozoan malaria parasite of humans, represents a major public health concern in the Republic of Korea (= South Korea). However, little is known about the genetic properties and population structures of the P. vivax isolates circulating in South Korea. This article reviews known polymorphic genetic markers in South Korean isolates of P. vivax and briefly summarizes the current issues surrounding the gene and population structures of this parasite. The critical genetic characteristics of major antigens of the parasite, such as circumsporozoite protein (CSP), merozoite surface protein 1 (MSP-1) and MSP-3, Duffy binding protein (DBP), apical membrane antigen 1 (AMA-1), and GAM-1, are also discussed.
Amino Acid Sequence ; Animals ; Antigens, Protozoan/chemistry/*genetics ; Base Sequence ; Humans ; Malaria, Vivax/*parasitology ; Molecular Sequence Data ; Plasmodium vivax/chemistry/*genetics/isolation & purification ; *Polymorphism, Genetic ; Protozoan Proteins/chemistry/*genetics ; Republic of Korea ; Sequence Alignment

The plasmepsins are the aspartic proteases of malaria parasites. Treatment of aspartic protease inhibitor inhibits hemoglobin hydrolysis and blocks the parasite development in vitro suggesting that these proteases might be exploited their potentials as antimalarial drug targets. In this study, we determined the genetic variations of the aspartic proteases of Plasmodium vivax (PvPMs) of wild isolates. Two plasmepsins (PvPM4 and PvPM5) were cloned and sequenced from 20 P. vivax Korean isolates and two imported isolates. The sequences of the enzymes were highly conserved except a small number of amino acid substitutions did not modify key residues for the function or the structure of the enzymes. The high sequence conservations between the plasmepsins from the isolates support the notion that the enzymes could be reliable targets for new antimalarial chemotherapeutics.
Amino Acid Sequence ; Animals ; Aspartic Endopeptidases/*genetics ; Base Sequence ; Cloning, Molecular ; Conserved Sequence ; DNA, Protozoan/chemistry/genetics ; Human ; Molecular Sequence Data ; Plasmodium vivax/*enzymology/genetics/isolation & purification ; Polymerase Chain Reaction ; Sequence Alignment ; Sequence Analysis, DNA ; Support, Non-U.S. Gov't

In order to develop tools for an early serodiagnosis of Plasmodium falciparum infection, we evaluated the usefulness of P. falciparum liver stage antigen-3 (LSA-3) as a serodiagnostic antigen. A portion of LSA-3 gene was cloned, and its recombinant protein (rLSA-3) was expressed in Escherichia coli and purified by column chromatography. The purified rLSA-3 and 120 test blood/serum samples collected from inhabitants in malaria-endemic areas of Mandalay, Myanmar were used for this study. In microscopic examinations of blood samples, P. falciparum positive rate was 39.1% (47/120) in thin smear trials, and 33.3% (40/120) in thick smear trials. Although the positive rate associated with the rLSA-3 (30.8%) was lower than that of the blood stage antigens (70.8%), rLSA-3 based enzyme-linked immunosorbent assay could detect 12 seropositive cases (10.0%), in which blood stage antigens were not detected. These results indicate that the LSA-3 is a useful antigen for an early serodiagnosis of P. falciparum infection.
Recombinant Proteins/biosynthesis/genetics/*immunology ; Plasmodium vivax/isolation & purification ; Plasmodium falciparum/*immunology ; Molecular Sequence Data ; Malaria, Falciparum/blood/*diagnosis ; Humans ; Genes, Protozoan/genetics/immunology ; Fluorescent Antibody Technique, Direct/methods ; Escherichia coli/genetics ; Enzyme-Linked Immunosorbent Assay/methods ; Early Diagnosis ; DNA, Protozoan/chemistry ; DNA Primers/chemistry ; Cloning, Molecular/methods ; Base Sequence ; Antigens, Protozoan/biosynthesis/chemistry/genetics/*immunology ; Animals ; Amino Acid Sequence

The present study was designed to investigate polymorphism in Duffy binding protein (DBP) gene of Plasmodium vivax isolates of Korea. Thirty samples were obtained from P. vivax patients in Yonchon-gun, Kyonggi-do in 1998. The PCR products of the samples were subjected to sequencing and hybridization analyses of the regions II and IV of P. vivax DBP gene. Two genotypes, SK-1 and SK-2, were identified on the basis of amino acid substitution and deletion. The genotype of 10 isolates was SK-1 and that of 20 isolates was SK-2. Most of the predicted amino acids in the region II of DBP gene were conserved between the Korean isolates and Belem strain except for 4-5 amino acid substitutions. In the region IV of DBP, a 6-bp insert that was shown in the Sal-1 allele type was found in SK-1, and a 27-bp insert that was shown in the Papua New Guinea allele type was found in SK-2. In conclusion, the present findings suggest that two genotypes of P. vivax coexist in the endemic area of Korea.
Amino Acid Sequence ; Animals ; *Antigens, Protozoan ; Base Sequence ; Carrier Proteins/*analysis/chemistry/*genetics ; DNA, Protozoan/genetics ; Genotype ; Human ; Korea ; Malaria, Vivax/parasitology ; Molecular Sequence Data ; Plasmodium vivax/*genetics/isolation & purification ; Polymerase Chain Reaction ; *Polymorphism (Genetics) ; *Protozoan Proteins ; Receptors, Cell Surface/*analysis/chemistry/*genetics ; Support, Non-U.S. Gov't

Resistance of Plasmodium spp. to anti-malarial drugs is the primary obstacle in the fight against malaria, and molecular markers for the drug resistance have been applied as an adjunct in the surveillance of the resistance. In this study, we investigated the prevalence of mutations in pvmdr1, pvcrt-o, pvdhfr, and pvdhps genes in temperate-zone P. vivax parasites from central China. A total of 26 isolates were selected, including 8 which were previously shown to have a lower susceptibility to chloroquine in vitro. For pvmdr1, pvcrt-o, and pvdhps genes, no resistance-conferring mutations were discovered. However, a highly prevalent (69.2%), single-point mutation (S117N) was found in pvdhfr gene. In addition, tandem repeat polymorphisms existed in pvdhfr and pvdhps genes, which warranted further studies in relation to the parasite resistance to antifolate drugs. The study further suggests that P. vivax populations in central China may still be relatively susceptible to chloroquine and sulfadoxine-pyrimethamine.
Antimalarials/*pharmacology ; China ; Chloroquine/pharmacology ; DNA, Protozoan/chemistry/genetics ; Drug Resistance/*genetics ; Folic Acid Antagonists/pharmacology ; Genotype ; Humans ; Malaria, Vivax/epidemiology/*parasitology ; Plasmodium vivax/drug effects/*genetics/isolation & purification ; Point Mutation ; Polymorphism, Single Nucleotide/*genetics ; Prevalence ; Protozoan Proteins/genetics ; Sequence Analysis, DNA ; Tandem Repeat Sequences/*genetics

Malaria is still a major health problem in Thailand and its incidence is currently rising in Korea. To identify a useful antigen for the diagnosis of malaria patients, a cDNA expression library from malaria parasites was constructed and screened out immunologically. One clone was selected in view of its predominant reactivity with the patient sera. The recombinant malaria parasite antigen (Pv30) with 27 kDa as a C-terminal His-tag fusion protein that was produced in Escherichia coli was identified through immunoblot analysis. The deduced amino acid sequence had the sequence homology with the merozoite surface protein 1 (MSP1) genes of Plasmodium falciparum and P. yoelii, each by 41% and 42%, respectively. Measurement of serum IgG and IgM antibody to Pv30 by enzyme-linked immunosorbent assay (ELISA) was evaluated as a serodiagnostic test for malaria patients in Thailand (endemic area) and Korea (recently reemerging area). The sensitivity of P. vivax, P. falciparum, and P. malariae was 96.3% (26 /27), 90.6% (29/32), and 100% (6/6), respectively, and the specificity was 63.5% (40/63) in Thailand samples. The sensitivity of P. vivax was 98.8% (88/89), and the specificity was 96.6% (86/89) in Korean samples. Pv30 appears to be a good and reliable recombinant antigen for serodiagonosis of malaria in a nonendemic area.
Amino Acid Sequence ; Animals ; Antibodies, Protozoan ; Enzyme-Linked Immunosorbent Assay/*methods ; Human ; Korea ; Malaria, Vivax/*diagnosis/immunology ; Merozoite Surface Protein 1/*analysis/genetics/immunology ; Molecular Sequence Data ; Plasmodium vivax/chemistry/immunology/*isolation & purification ; Sensitivity and Specificity ; Serologic Tests ; Support, Non-U.S. Gov't