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Natural variation within the principal adhesion domain of the Plasmodium vivax duffy binding protein.

ABSTRACT: The blood-stage development of malaria parasites is initiated by the invasion of merozoites into susceptible erythrocytes. Specific receptor-ligand interactions must occur for the merozoites to first attach to and then invade erythrocytes. Because the invasion process is essential for the parasite's survival and the merozoite adhesion molecules are exposed on the merozoite surface during invasion, these adhesion molecules are candidates for antibody-dependent malaria vaccines. The Duffy binding protein of Plasmodium vivax belongs to a family of erythrocyte-binding proteins that contain functionally conserved cysteine-rich regions. The amino cysteine-rich regions of these homologous erythrocyte-binding proteins were recently identified for P. vivax, Plasmodium knowlesi, and Plasmodium falciparum as the principal erythrocyte-binding domains (C. Chitnis and L. H. Miller, J. Exp. Med. 180:497-506, 1994, and B. K. L. Sim, C. E. Chitnis, K. Wasniowska, T. J. Hadley, and L. H. Miller, Science 264:1941-1944, 1994). We report that amino acids in this critical ligand domain of the P. vivax Duffy binding protein are hypervariable, but this variability is limited. Hypervariability of the erythrocyte-binding domain suggests that this domain is the target of an effective immune response, but conservation of amino acid substitutions indicates that functional constraints limit this variation. In addition, the amino cysteine-rich region and part of the hydrophilic region immediately following it were the site of repeated homologous recombinations as represented by tandem repeat sequence polymorphisms. Similar polymorphisms have been identified in the same region of the homologous genes of P. falciparum and P. knowlesi, suggesting that there is a common mechanism of recombination or gene conversion that occurs in these Plasmodium genes.

SUBMITTER: Tsuboi T

PROVIDER: S-EPMC303305 | biostudies-other | 1994 Dec

REPOSITORIES: biostudies-other

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Natural variation within the principal adhesion domain of the Plasmodium vivax duffy binding protein.

Tsuboi T T Kappe S H SH al-Yaman F F Prickett M D MD Alpers M M Adams J H JH

Infection and immunity 19941201 12

The blood-stage development of malaria parasites is initiated by the invasion of merozoites into susceptible erythrocytes. Specific receptor-ligand interactions must occur for the merozoites to first attach to and then invade erythrocytes. Because the invasion process is essential for the parasite's survival and the merozoite adhesion molecules are exposed on the merozoite surface during invasion, these adhesion molecules are candidates for antibody-dependent malaria vaccines. The Duffy binding ...[more]

PMID: 7960140

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Project description:BackgroundThe Duffy-binding protein II of Plasmodium vivax (PvDBPII) has been considered as an attractive target for vaccine-mediated immunity despite a possible highly polymorphic nature. Among seven PvDBP domains, domain II has been shown to exhibit a high rate of nonsynonymous polymorphism, which has been suggested to be a potential immune (antibody binding) evasion mechanism. This study aimed to determine the extent of genetic polymorphisms and positive natural selection at domain II of the PvDBP gene among a sampling of Thai P. vivax isolates.MethodsThe PvDBPII gene was PCR amplified and the patterns of polymorphisms were characterized from 30 Thai P. vivax isolates using DNA cloning and sequencing. Phylogenetic analysis of the sequences and positive selection were done using DnaSP ver 4.0 and MEGA ver 4.0 packages.ResultsThis study demonstrated a high rate of nonsynonymous polymorphism. Using Sal I as the reference strain, a total of 30 point-mutations were observed in the PvDBPII gene among the set of Thai P. vivax isolates, of which 25 nonsynonymous and five synonymous were found. The highest frequency of polymorphism was found in five variant amino acids (residues D384G, R390H, L424I, W437R, I503K) with the variant L424I having the highest frequency. The difference between the rates of nonsynonymous and synonymous mutations estimated by the Nei and Gojobori's method suggested that PvDBPII antigen appears to be under selective pressure. Phylogenetic analysis of PvDBPII Thai P. vivax isolates to others found internationally demonstrated six distinct allele groups. Allele groups 4 and 6 were unique to Thailand.ConclusionPolymorphisms within PvDBPII indicated that Thai vivax malaria parasites are genetically diverse. Phylogenetic analysis of DNA sequences using the Neighbour-Joining method demonstrated that Thai isolates shared distinct alleles with P. vivax isolates from different geographical areas. The study reported here will be valuable for the development of PvDBPII-based malaria vaccine.

Project description:The Plasmodium vivax Duffy binding protein region II (DBPII) is a vital ligand for the parasite's invasion of reticulocytes, thereby making this molecule an attractive vaccine candidate against vivax malaria. However, strain-specific immunity due to DBPII allelic variation in Bc epitopes may complicate vaccine efficacy, suggesting that an effective DBPII vaccine needs to target conserved epitopes that are potential targets of strain-transcending neutralizing immunity. The minimal epitopes reactive with functionally inhibitory anti-DBPII monoclonal antibody (MAb) 3C9 and noninhibitory anti-DBPII MAb 3D10 were mapped using phage display expression libraries, since previous attempts to deduce the 3C9 epitope by cocrystallographic methods failed. Inhibitory MAb 3C9 binds to a conserved conformation-dependent epitope in subdomain 3, while noninhibitory MAb 3D10 binds to a linear epitope in subdomain 1 of DBPII, consistent with previous studies. Immunogenicity studies using synthetic linear peptides of the minimal epitopes determined that the 3C9 epitope, but not the 3D10 epitope, could induce functionally inhibitory anti-DBPII antibodies. Therefore, the highly conserved binding-inhibitory 3C9 epitope offers the potential as a component in a broadly inhibitory, strain-transcending DBP subunit vaccine.IMPORTANCE Vivax malaria is the second leading cause of malaria worldwide and the major cause of non-African malaria. Unfortunately, efforts to develop antimalarial vaccines specifically targeting Plasmodium vivax have been largely neglected, and few candidates have progressed into clinical trials. The Duffy binding protein is considered a leading blood-stage vaccine candidate because this ligand's recognition of the Duffy blood group reticulocyte surface receptor is considered essential for infection. This study identifies a new target epitope on the ligand's surface that may serve as the target of vaccine-induced binding-inhibitory antibody (BIAb). Understanding the potential targets of vaccine protection will be important for development of an effective vaccine.

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Natural variation within the principal adhesion domain of the Plasmodium vivax duffy binding protein.

Publications

Natural variation within the principal adhesion domain of the Plasmodium vivax duffy binding protein.

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