Genetic Diversity and Natural Selection in 42 kDa Region of Plasmodium vivax Merozoite Surface Protein-1 from China-Myanmar Endemic Border.

Plasmodium vivax merozoite surface protein-1 (PvMSP1) gene codes for a major malaria vaccine candidate antigen. However, its polymorphic nature represents an obstacle to the design of a protective vaccine. In this study, we analyzed the genetic polymorphism and natural selection of the C-terminal 42 kDa fragment within PvMSP1 gene (Pv MSP142) from 77 P. vivax isolates, collected from imported cases of China-Myanmar border (CMB) areas in Yunnan province and the inland cases from Anhui, Yunnan, and Zhejiang province in China during 2009-2012. Totally, 41 haplotypes were identified and 30 of them were new haplotypes. The differences between the rates of non-synonymous and synonymous mutations suggest that PvMSP142 has evolved under natural selection, and a high selective pressure preferentially acted on regions identified of PvMSP133. Our results also demonstrated that PvMSP142 of P. vivax isolates collected on China-Myanmar border areas display higher genetic polymorphisms than those collected from inland of China. Such results have significant implications for understanding the dynamic of the P. vivax population and may be useful information towards China malaria elimination campaign strategies.

Genetic diversity and natural selection of three blood-stage 6-Cys proteins in Plasmodium vivax populations from the China-Myanmar endemic border.

Pv12, Pv38 and Pv41, the three 6-Cys family proteins which are expressed in the blood-stage of vivax malaria, might be involved in merozoite invasion activity and thus be potential vaccine candidate antigens of Plasmodium vivax. However, little information is available concerning the genetic diversity and natural selection of these three proteins. In the present study, we analyzed the amino acid sequences of P. vivax blood-stage 6-Cys family proteins in comparison with the homologue proteins of Plasmodium cynomolgi strain B using bioinformatic methods. We also investigated genetic polymorphisms and natural selection of these three genes in P. vivax populations from the China-Myanmar endemic border. The three P. vivax blood-stage 6-Cys proteins were shown to possess a signal peptide at the N-terminus, containing two s48/45 domains, and Pv12 and Pv38 have a GPI-anchor motif at the C-terminus. Then, 22, 21 and 29 haplotypes of pv12, pv38 and pv41 were identified out of 45, 38 and 40 isolates, respectively. The dN/dS values for Domain II of pv38 and pv41 were 3.33880 and 5.99829, respectively, suggesting positive balancing selection for these regions. Meanwhile, the C-terminus of pv41 showed high nucleotide diversity, and Tajima's D test suggested that this fragment could be under positive balancing selection. Overall, our results have significant implications, providing a genetic basis for blood-stage malaria vaccine development based on these three 6-Cys proteins.

[Genetic variations of the elastase gene among eight populations of Schistosoma japonicum].

OBJECTIVE: To investigate genetic diversity in the elastase gene among eight Schistosoma japonicum populations, and whether natural selection occur. METHODS: S. japonicum populations were collected from the provinces of Anhui (Tongling and Guichi), Hunan (Yueyang), Hubei (Shashi), Sichuan (Xichang), Yunnan (Eryuan), Taiwan (Puye) in China, and the Philippines. The elastase gene from different populations was amplified by PCR and then sequenced. Watterson's theta, Tajima's pi, dN/dS ratio, Tajima's D and fixation index (F(st)) of each population were calculated. The phylogenetic networks based on the elastase gene were constructed by median-joining algorithm. RESULTS: A total of 73 elestase gene sequences (GenBank No. KF297654-KF297681) were obtained from 8 populations. The sequence analysis indicated that higher genetic diversity was found in the populations from the middle and lower reaches of the Yangtze River (i.e. Tongling City of Anhui, Yueyang City of Hunan), while there was no genetic variations in Hubei or Philippines populations. The value of Tajima's D was positive in Hunan population, while negative in the other populations. The dN/dS ratio was higher than 1 in Tongling population, whereas lower than 1 in Taiwan population. Significant genetic differentiations were observed between Taiwan population and other populations. CONCLUSION: The genetic diversity of the elastase gene among S. japonicum populations is very high, and a high level of gene flow has been detected among the populations from the middle and lower reaches of the Yangtze River. The S.japonicum elastase gene might have been under a positive selection. The level of genetic divergence is the highest between Taiwan population and others.

[New polymorphic microsatellite loci identified using genomic resource for Schistosoma japonicum].

OBJECTIVE: To identify new microsatellite loci from genome sequence database for the study of polymorphism of Schistosoma japonicum. METHODS: Schistosoma japonicum isolates were obtained from seven endemic sites in China: Tongling and Guichi counties of Anhui Province, Duchang county of Jiangxi Province, Changde and Yueyang Cities of Hunan Province, Shashi City of Hubei Province, Xichang City of Sichuan Province. In order to study the genetic variance, genomic DNAs of 96 individual adult worms were screened against 17 new Schistosoma japonicum microsatellites and the raw data were analyzed by GenMapper 4.0. Furthermore, the varieties of alleles were inverstigated using GenA1Ex 6 and genetic distances within a subpopulation (GenClone) and among populations(UPGMA, MEGA 3.1) were analyzed. RESULTS: High levels of polymorphism were found between and within population samples, and significant genetic diversity was observed among the seven subpopulations. Within Jiangxi population, most genetic distances (17 loci) among samples range from 25 to 32, indicating a significant genetic diversity. There are three clusters among the seven populations: Jiangxi, Tonglin, Shashi and Changde population, with the genetics distances ranging from 0.0178 to 0.0363; Guichi and Yueyang population belong to another cluster, with the genetic distance of 0.0247; However, Xichang population is an unique group. Its genetic distances to other populations are notable with a range from 0.019 2 to 0.069 3. CONCLUSION: The 17 new polymorphic microsatellites identified may be used as suitable markers for the study on population genetics of Schistosoma japonicum and the genetic variance of the worms seems to be complicated.