Abstract
BackgroundThe glutamate-rich protein (GLURP) of the malaria parasite Plasmodium falciparum is a key surface antigen that serves as a component of a clinical vaccine. Moreover, the GLURP gene is also employed routinely as a genetic marker for malarial genotyping in epidemiological studies. While extensive size polymorphisms in GLURP are well recorded, the extent of the sequence diversity of this gene is rarely investigated. The present study aimed to explore the genetic diversity of GLURP in natural populations of P. falciparum.ResultsThe polymorphic C-terminal repetitive R2 region of GLURP sequences from 65 P. falciparum isolates in Thailand were generated and combined with the data from 103 worldwide isolates to generate a GLURP database. The collection was comprised of 168 alleles, encoding 105 unique GLURP subtypes, characterized by 18 types of amino acid repeat units (AAU). Of these, 28 GLURP subtypes, formed by 10 AAU types, were detected in P. falciparum in Thailand. Among them, 19 GLURP subtypes and 2 AAU types are described for the first time in the Thai parasite population. The AAU sequences were highly conserved, which is likely due to negative selection. Standard Fst analysis revealed the shared distributions of GLURP types among the P. falciparum populations, providing evidence of gene flow among the different demographic populations.ConclusionsSequence diversity causing size variations in GLURP in Thai P. falciparum populations were detected, and caused by non-synonymous substitutions in repeat units and some insertion/deletion of aspartic acid or glutamic acid codons between repeat units. The P. falciparum population structure based on GLURP showed promising implications for the development of GLURP-based vaccines and for monitoring vaccine efficacy.
Highlights
The glutamate-rich protein (GLURP) of the malaria parasite Plasmodium falciparum is a key surface antigen that serves as a component of a clinical vaccine
Nucleotide diversity and neutrality test The GLURP R2 region was amplified from the genomic DNA of 72 isolates of P. falciparum collected from five localities in Thailand
The nucleotide sequences of GLURP in P. falciparum from Thailand were combined with 103 sequences from the NCBI nucleotide collections and from wholegenome shotgun sequences to generate a global collection of 168 GLURP alleles and the in silico translated GLURP alleles in P. falciparum isolates worldwide (Additional file 2: Table S1), encoding a total of 105 GLURP subtypes
Summary
The glutamate-rich protein (GLURP) of the malaria parasite Plasmodium falciparum is a key surface antigen that serves as a component of a clinical vaccine. A microscopic examination of the blood stage malaria on blood films is the most commonly used method in the laboratory and clinics This technique is simple, low-cost and easy to perform, but it has many limitations, such as the requirement of high. One of the polymorphic antigen-encoding genes often employed as a key genetic marker for strain identification of the human malaria parasite P. falciparum is the glutamate-rich protein (GLURP) gene. The glutamate-rich protein (GLURP), a 220 kDa antigen expressed throughout the life-cycle of the malaria parasites in a mammalian host [12, 13], is localized to the Plasmodium falciparum Pfs protein complex on the merozoite surface, and the protein contains a module of six cysteine residues forming three intramolecular disulphide bonds. The R0 region is predicted to be hydrophobic and may act as a signal peptide, which is a feature of secretory proteins [13]
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