Plasmodium falciparum SURFIN_4.1 is a type I transmembrane protein thought to locate on the merozoite surface and to be responsible for a reversible adherence to the erythrocyte before invasion. In this study, we evaluated surf_4.1 gene segment encoding extracellular region for polymorphism, the signature of positive selection, the degree of linkage disequilibrium, and temporal change in allele frequency distribution in P. falciparum isolates from Thailand in 1988–89, 2003, and 2005. We found that SURFIN_4.1 is highly polymorphic, particularly at the C-terminal side of the variable region located just before a predicted transmembrane region. A signature of positive diversifying selection on the variable region was detected by multiple tests and, to a lesser extent, on conserved N-terminally located cysteine-rich domain by Tajima’s D test. Linkage disequilibrium between sites over a long distance (> 1.5 kb) was detected, and multiple SURFIN_4.1 haplotype sequences detected in 1988/89 still circulated in 2003. Few of the single amino acid polymorphism allele frequency distributions were significantly different between the 1988/89 and 2003 groups, suggesting that the frequency distribution of SURFIN_4.1 extracellular region remained stable over 14 years.

Plasmodium falciparum SURFIN_4.1 is a type I transmembrane protein thought to locate on the merozoite surface and to be responsible for a reversible adherence to the erythrocyte before invasion. In this study, we evaluated surf_4.1 gene segment encoding extracellular region for polymorphism, the signature of positive selection, the degree of linkage disequilibrium, and temporal change in allele frequency distribution in P. falciparum isolates from Thailand in 1988–89, 2003, and 2005. We found that SURFIN_4.1 is highly polymorphic, particularly at the C-terminal side of the variable region located just before a predicted transmembrane region. A signature of positive diversifying selection on the variable region was detected by multiple tests and, to a lesser extent, on conserved N-terminally located cysteine-rich domain by Tajima’s D test. Linkage disequilibrium between sites over a long distance (> 1.5 kb) was detected, and multiple SURFIN_4.1 haplotype sequences detected in 1988/89 still circulated in 2003. Few of the single amino acid polymorphism allele frequency distributions were significantly different between the 1988/89 and 2003 groups, suggesting that the frequency distribution of SURFIN_4.1 extracellular region remained stable over 14 years.

Objective To compare the growth of Plasmodium vivax in Anopheles sinensis(An.s) and Anopheles anthropophagus(An.a) during the periods of malaria clinic attack and diapause. Methods The blood samples of patients during the clinic attack and diapause of vivax malaria patients in the vivax epidemic area in China were collected, feeding the mosquitoes of An.s and An.a by using the artificial membrane feeding system in vivo in the lab, and the mosquitoes were dissected during the day 7-9th and 14th after the infection and the oocysts and sporozoites in the stomach and gland of the mosquitoes were counted, respectively. Results The oocyst positive rate in An.s fed by Plasmodium vivax during the fever stage was lower than that in non-fever stage, the sporozoite positive rate in An.a fed by Plasmodium vivax during the fever stage was lower than that in non-fever stage. The positive mosquito rate with oocyst and sporozoite infected by Plasmodium vivax in the fever stage to An.s and An.a were lower than those in non-fever stage. The infective sporozoite intensity of An.s fed by Plasmodium vivax in the fever stage was lower than that in non-fever stage, but the reverse result was found to An.a. Conclusion There is a significant difference between the periods of malaria clinic attack and diapause of the oocyst and sporozoite infection to An.s and An.a.

Objective To compare the susceptibility of Anopheles anthropophagus from Jiangsu, Guangdong and Liaoning provinces in China to Plasmodium vivax.Methods The blood samples of patients with P. vivax in endemic areas of China were collected to feed the mosquitoes of An. anthropophagus from different areas by using the artificial in vitro membrane feeding system in the lab, and then the mosquitoes were dissected during the 7-9th day and on the 14th day after the feeding and the oocysts and sporozoites in the stomach and salivy gland of mosquitoes were counted. Results The mosquitoes from Jiangsu, Guangdong and Liaoning were simultaneously fed with the blood of 35 cases of P. vivax. The oocyst positive rates of An. anthropophagus from Jiangsu, Guangdong and Liaoning during the 7-9th day after the feeding were 68.57%, 60.00% and 68.57%, as well as the sporozoite positive rates of them on the 14th day after the feeding were 22.86%, 14.29% and 22.86%, respectively. On the 7th day after the feeding, 228, 235, 228 mosquitoes of An. anthropophagus from Jiangsu, Guangdong and Liaoning were dissected, and the positive mosquito rates with oocyst infection were 28.07%, 25.11% and 26.75%, respectively. On the 14th day after the feeding, 150, 142, 135 mosquitoes of An. anthropophagus from the three areas were dissected, the positive rates with sporozoite infection were 10.67%, 8.45% and 11.85%, respectively. The num-bers of mosquitoes dissected with infective grade("+","++","+++","++++") of sporozoites of An. anthropophagus from Jiangsu, Guangdong and Liaoning were 4, 3, 2, 7; 2, 2, 3, 7 and 1, 6, 3, 8, respectively. Conclusions An. anthropophagus from Jiangsu, Guangdong and Liaoning is susceptible to the parasites of Plasmodium vivax and there is no significant difference among the susceptibilities of An. anthropophagus from the three areas to Plasmodium vivax.

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

A family of calcium-dependent protein kinases (CDPKs) is a unique enzyme which plays crucial roles in intracellular calcium signaling in plants, algae, and protozoa. CDPKs of malaria parasites are known to be key regulators for stage-specific cellular responses to calcium, a widespread secondary messenger that controls the progression of the parasite. In our study, we identified a gene encoding Plasmodium vivax CDPK4 (PvCDPK4) and characterized its molecular property and cellular localization. PvCDPK4 was a typical CDPK which had well-conserved N-terminal kinase domain and C-terminal calmodulin-like structure with 4 EF hand motifs for calcium-binding. The recombinant protein of EF hand domain of PvCDPK4 was expressed in E. coli and a 34 kDa product was obtained. Immunofluorescence assay by confocal laser microscopy revealed that the protein was expressed at the mature schizont of P. vivax. The expression of PvCDPK4-EF in schizont suggests that it may participate in the proliferation or egress process in the life cycle of this parasite.
Amino Acid Sequence ; Cloning, Molecular ; Conserved Sequence ; Escherichia coli/genetics ; Gene Expression ; Gene Expression Profiling ; Microscopy, Confocal ; Microscopy, Fluorescence ; Molecular Sequence Data ; Molecular Weight ; Plasmodium vivax/chemistry/*genetics ; Protein Kinases/analysis/chemistry/*genetics ; Protein Structure, Tertiary ; Protozoan Proteins/analysis/chemistry/*genetics ; Sequence Alignment