Genetic Diversity Analysis of Surface-Related Antigen (SRA) in Plasmodium falciparum Imported From Africa to China.

Plasmodium falciparum surface-related antigen (SRA) is located on the surfaces of gametocyte and merozoite and has the structural and functional characteristics of potential targets for multistage vaccine development. However, little information is available regarding the genetic polymorphism of pfsra. To determine the extent of genetic variation about P. falciparum by characterizing the sra sequence, 74 P. falciparum samples were collected from migrant workers who returned to China from 12 countries of Africa between 2015 and 2019. The full length of the sra gene was amplified and sequenced. The average pairwise nucleotide diversities (π) of P. falciparum sra gene was 0.00132, and the haplotype diversity (Hd) was 0.770. The average number of nucleotide differences (k) for pfsra was 3.049. The ratio of non-synonymous (dN) to synonymous (dS) substitutions across sites (dN/dS) was 1.365. Amino acid substitutions of P. falciparum SRA could be categorized into 35 unique amino acid variants. Neutrality tests showed that the polymorphism of PfSRA was maintained by positive diversifying selection, which indicated its role as a potential target of protective immune responses and a vaccine candidate. Overall, the ability of the N-terminal of PfSRA antibodies to evoke inhibition of merozoite invasion of erythrocytes and conserved amino acid at low genetic diversity suggest that the N-terminal of PfSRA could be evaluated as a vaccine candidate against P. falciparum infection.

[DNA genetyping of the trace bloodstains on the adsorbent object].

OBJECTIVE: To study the extraction and analysis of DNA from trace bloodstains on the adsorbent object. METHODS: DNA was extracted by Chelex-100, QIAamp Mini Kit, and modified QIAamp Mini Kit, respectively. The extracted DNA was amplified and short tandem repeat (STR) loci were genotyped by multiplex PCR procedures, and then analyzed by ABI 3100 Genetic Analyzer. RESULTS: The STR loci could be better genotyped with modified QIAamp Mini Kit, compared to poorer genotyping results obtained with Chelex-100 extraction method and QIAamp Mini Kit. CONCLUSION: Our data indicate that DNA extracted from trace bloodstains on adsorbent object with modified QIAamp Mini Kit serves a better DNA template. for amplification and genotyping.