title: Identification of a highly antigenic linear B cell epitope within Plasmodium vivax apical membrane antigen 1 (AMA-1).
abstract: Apical membrane antigen 1 (AMA-1) is considered to be a major candidate antigen for a malaria vaccine. Previous immunoepidemiological studies of naturally acquired immunity to Plasmodium vivax AMA-1 (PvAMA-1) have shown a higher prevalence of specific antibodies to domain II (DII) of AMA-1. In the present study, we confirmed that specific antibody responses from naturally infected individuals were highly reactive to both full-length AMA-1 and DII. Also, we demonstrated a strong association between AMA-1 and DII IgG and IgG subclass responses. We analyzed the primary sequence of PvAMA-1 for B cell linear epitopes co-occurring with intrinsically unstructured/disordered regions (IURs). The B cell epitope comprising the amino acid sequence 290-307 of PvAMA-1 (SASDQPTQYEEEMTDYQK), with the highest prediction scores, was identified in domain II and further selected for chemical synthesis and immunological testing. The antigenicity of the synthetic peptide was identified by serological analysis using sera from P. vivax-infected individuals who were knowingly reactive to the PvAMA-1 ectodomain only, domain II only, or reactive to both antigens. Although the synthetic peptide was recognized by all serum samples specific to domain II, serum with reactivity only to the full-length protein presented 58.3% positivity. Moreover, IgG reactivity against PvAMA-1 and domain II after depletion of specific synthetic peptide antibodies was reduced by 18% and 33% (P = 0.0001 for both), respectively. These results suggest that the linear epitope SASDQPTQYEEEMTDYQK is highly antigenic during natural human infections and is an important antigenic region of the domain II of PvAMA-1, suggesting its possible future use in pre-clinical studies.
authors.affiliation: Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Lilian Lacerda
authors.initials: LL
authors.lastname: Bueno
authors.forename: Francisco Pereira
authors.initials: FP
authors.lastname: Lobo
authors.forename: Cristiane Guimarães
authors.initials: CG
authors.lastname: Morais
authors.forename: Luíza Carvalho
authors.initials: LC
authors.lastname: Mourão
authors.forename: Ricardo Andrez Machado
authors.initials: RA
authors.lastname: de Ávila
authors.forename: Irene Silva
authors.initials: IS
authors.lastname: Soares
authors.forename: Cor Jesus
authors.initials: CJ
authors.lastname: Fontes
authors.forename: Marcus Vinícius
authors.initials: MV
authors.lastname: Lacerda
authors.forename: Carlos
authors.initials: C
authors.lastname: Chavez Olórtegui
authors.forename: Daniella Castanheira
authors.initials: DC
authors.lastname: Bartholomeu
authors.forename: Ricardo Toshio
authors.initials: RT
authors.lastname: Fujiwara
authors.forename: Erika Martins
authors.initials: EM
authors.lastname: Braga
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000595:Amino Acid Sequence; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood / Q000235:genetics / Q000276:immunology; D000953:Antigens, Protozoan / Q000235:genetics / Q000276:immunology*; D018985:Epitopes, B-Lymphocyte / Q000276:immunology*; D006801:Humans; D016780:Malaria, Vivax / Q000097:blood / Q000276:immunology / Q000382:microbiology; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology*; D008875:Middle Aged; D008969:Molecular Sequence Data; D010455:Peptides / Q000235:genetics / Q000276:immunology; D010966:Plasmodium vivax / Q000166:cytology / Q000276:immunology*; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology*; D055815:Young Adult
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D018985:Epitopes, B-Lymphocyte; D008565:Membrane Proteins; D010455:Peptides; D015800:Protozoan Proteins; C090077:apical membrane antigen I, Plasmodium