title: Antibody response of naturally infected individuals to recombinant Plasmodium vivax apical membrane antigen-1.
abstract: In the present study, we evaluate the naturally acquired antibody response to the Plasmodium vivax apical membrane antigen 1 (PvAMA-1), a leading vaccine candidate against malaria. The gene encoding the PvAMA-1 ectodomain region (amino acids 43-487) was cloned by PCR using genomic DNA from a Brazilian individual with patent P. vivax infection. The predicted amino acid sequence displayed a high degree of identity (97.3%) with a previously published sequence from the P. vivax Salvador strain. A recombinant protein representing the PvAMA-1 ectodomain was expressed in Escherichia coli and refolded. By ELISA, this recombinant protein reacted with 85 and 48.5% of the IgG or IgM antibodies, respectively, from Brazilian individuals with patent P. vivax malaria. IgG1 was the predominant subclass of IgG. The frequency of response increased according to the number of malaria episodes, reaching 100% in individuals in their fourth malaria episode. The high degree of recognition of PvAMA-1 by human antibodies was confirmed using a second recombinant protein expressed in Pichia pastoris (PV66/AMA-1). The observation that recognition of the bacterial recombinant PvAMA-1 was only slightly lower than that of the highly immunogenic 19kDa C-terminal domain of the P. vivax Merozoite Surface Protein-1 was also important. DNA sequencing of the PvAMA-1 variable domain from 20 Brazilian isolates confirmed the limited polymorphism of PvAMA-1 suggested by serological analysis. In conclusion, we provide evidence that PvAMA-1 is highly immunogenic during natural infection in humans and displays limited polymorphism in Brazil. Based on these observations, we conclude that PvAMA-1 merits further immunological studies as a vaccine candidate against P. vivax malaria.
authors.affiliation: Departamento de Análises Clínicas e Toxicológicas, Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, Av. Prof Lineu Prestes, 580, Cidade Universitária, São Paulo SP 05508-900, Brazil.
authors.forename: Maria Helena C
authors.initials: MH
authors.lastname: Rodrigues
authors.forename: Karina M
authors.initials: KM
authors.lastname: Rodrigues
authors.forename: Tatiane R
authors.initials: TR
authors.lastname: Oliveira
authors.forename: Andréia N
authors.initials: AN
authors.lastname: Cômodo
authors.forename: Mauricio M
authors.initials: MM
authors.lastname: Rodrigues
authors.forename: Clemens H M
authors.initials: CH
authors.lastname: Kocken
authors.forename: Alan W
authors.initials: AW
authors.lastname: Thomas
authors.forename: Irene S
authors.initials: IS
authors.lastname: Soares
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000917:Antibody Formation / Q000276:immunology*; D000953:Antigens, Protozoan / Q000235:genetics / Q000276:immunology*; D001938:Brazil; D003001:Cloning, Molecular / Q000379:methods; D016054:DNA, Protozoan / Q000032:analysis; D019353:Endemic Diseases; D004797:Enzyme-Linked Immunosorbent Assay; D004926:Escherichia coli / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D017780:Malaria Vaccines / Q000235:genetics / Q000276:immunology; D016780:Malaria, Vivax / Q000276:immunology*; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology*; D020066:Merozoite Surface Protein 1; D010966:Plasmodium vivax / Q000235:genetics / Q000276:immunology; D011110:Polymorphism, Genetic / Q000235:genetics / Q000276:immunology; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology*; D011994:Recombinant Proteins / Q000276:immunology; D020539:Sequence Analysis, Protein / Q000379:methods; D014614:Vaccines, Synthetic / Q000235:genetics / Q000276:immunology
chemical_list: D000953:Antigens, Protozoan; D016054:DNA, Protozoan; D007074:Immunoglobulin G; D017780:Malaria Vaccines; D008565:Membrane Proteins; D020066:Merozoite Surface Protein 1; D015800:Protozoan Proteins; D011994:Recombinant Proteins; D014614:Vaccines, Synthetic; C111111:pva1 protein, Plasmodium vivax