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.

[Polymorphism analysis of Plasmodium falciparum histidine-rich protein II and III].

OBJECTIVE: To analyze the polymorphism of Plasmodium falciparum histidine-rich protein (PfHRP) II and III. METHODS: Genomic DNA was isolated from blood samples of 20 patients infected with Plasmodium falciparum in Yunnan Province. Blood samples were tested by microscopy and RDTs. The Pfhrp2 and Pfhrp3 gene fragments were amplified by PCR and sequenced. The sequencing results were analyzed and compared using the bioinformatics software. RESULTS: 20 patients infected with Plasmodium falciparum tested by microscopy and RDTs. PCR showed that the Pfhrp2 gene was with 389~986 bp, and Pfhrp3 gene with 329-640 bp. All PfH-IRP II sequences started with type 1 repeat (AHHAHHVAD) and ended with the type 12 repeat (AHHAAAHHEAATH). The number of type 7 (AHHAAD), type 2 (AHHAHHAAD) and type 6 (AHHATD) within PfHRP II was more than the other types of repeats, as well as type 16 (AHHAAN) and type 17 (AHHDG) for PfHRP III. Type 11 repeat (AHN) was not found from the PfHRP II and PfHRP III sequences. CONCLUSION: There is an extensive diversity in Pfhrp2 and Pfhrp3 fragments in the individuals infected with P. falciparum in Yunnan. Some types of repeats are shared by PfHRP II and PfHRP III.

[Increasing SNR of dynamic spectrum method using harmonic waves].

The sources of noise in dynamic spectrum (DS) method and their corresponding frequency characteristic were analyzed in order to improve the signal to noise ratio (SNR) of DS method. The processes of DS data in frequency domain were reviewed by means of energy, then the harmonic waves of DS data were taken into account in the DS signal and some experiments were done to test whether the modified method works well. In addition, corresponding experiments were carried out to seek the relationship between the SNR and the number of harmonic waves, and to determine how many harmonic waves should be involved in order to get the best SNR in DS method. Results showed when harmonic waves were used in the method properly, the modified method can distinguish DS more precisely. And it was also showed that as the number of harmonic waves increased, the correlation coefficient of DS data from different volunteers became smaller at first and then bigger later, while the correlation coefficient of DS data from different sampling site of the same volunteer kept increasing all the time. When the number of harmonic waves was set to 5, the correlation coefficient of DS data from different volunteers goes from 0.73752 to 0.73676, while the one from the same volunteer goes from 0.99416 to 0.99533, which means the modified method can reflect the information about blood component more precisely than the old ones, and thus the SNR of DS reaches the highest.

[Expression of hepatitis delta antigen Inner Mongolian strain in prokaryotic cell and analysis of its antigenicity].

OBJECTIVE: To obtain high yield and good antigenic activity of HDV L-Ag and to detect different regional patients' sera to test the purified antigen's antigenicity. METHODS: Hepatitis delta virus' sequence was obtained from Inner Mongolian patient by using RT-PCR and PCR methods, PET43a was used and His-tag was added at the HDV L-Ag 5' and 3' to construct the recombinant expression plasmid, transform the plasmid into host bacterium BL21 and induce it with IPTG. The expression supernatant was purified by saturated (NH4)2SO4 and affinity chromatography. The activity and antigenicity of the expressed product were analyzed by using EIA. RESULTS: Comparison of results obtained with detection by using the expressed protein coated plate and ABBOTT Murex anti-Delta (total) of 15 positive and 10 negative sera, the consistency was good (100%). CONCLUSION: EIA proved that the purified antigen had good antigenicity, no serological difference was found in detection between different region's sera, therefore the purified delta antigen may be useful in diagnostic and other research.