title: Naturally-acquired humoral immune responses against the N- and C-termini of the Plasmodium vivax MSP1 protein in endemic regions of Brazil and Papua New Guinea using a multiplex assay.
abstract: BACKGROUND
  Progress towards the development of a malaria vaccine against Plasmodium vivax, the most widely distributed human malaria parasite, will require a better understanding of the immune responses that confer clinical protection to patients in regions where malaria is endemic.
  
  
  METHODS
  Glutathione S-transferase (GST) and GST-fusion proteins representing the N- terminus of the merozoite surface protein 1 of P. vivax, PvMSP1-N, and the C-terminus, PvMSP1-C, were covalently coupled to BioPlex carboxylated beads. Recombinant proteins and coupled beads were used, respectively, in ELISA and Bioplex assays using immune sera of P. vivax patients from Brazil and PNG to determine IgG and subclass responses. Concordances between the two methods in the seropositivity responses were evaluated using the Kappa statistic and the Spearman's rank correlation.
  
  
  RESULTS
  The results using this methodology were compared with the classical microtitre enzyme-linked immnosorbent assay (ELISA), showing that the assay was sensitive, reproducible and had good concordance with ELISA; yet, further research into different statistical analyses seems desirable before claiming conclusive results exclusively based on multiplex assays. As expected, results demonstrated that PvMSP1 was immunogenic in natural infections of patients from different endemic regions of Brazil and Papua New Guinea (PNG), and that age correlated only with antibodies against the C-terminus part of the molecule. Furthermore, the IgG subclass profiles were different in these endemic regions having IgG3 predominantly recognizing PvMSP1 in Brazil and IgG1 predominantly recognizing PvMSP1 in PNG.
  
  
  CONCLUSIONS
  This study validates the use of the multiplex assay to measure naturally-acquired IgG antibodies against the merozoite surface protein 1 of P. vivax.
authors.affiliation: Barcelona Centre for International Health Research (CRESIB), Hospital Clinic/IDIBAPS, Universitat de Barcelona, Rosello 132, 08036 Barcelona, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Fernandez-Becerra
authors.forename: Sergi
authors.initials: S
authors.lastname: Sanz
authors.forename: Marina
authors.initials: M
authors.lastname: Brucet
authors.forename: Danielle I
authors.initials: DI
authors.lastname: Stanisic
authors.forename: Fabiana P
authors.initials: FP
authors.lastname: Alves
authors.forename: Erney P
authors.initials: EP
authors.lastname: Camargo
authors.forename: Pedro L
authors.initials: PL
authors.lastname: Alonso
authors.forename: Ivo
authors.initials: I
authors.lastname: Mueller
authors.forename: Hernando A
authors.initials: HA
authors.lastname: del Portillo
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood / Q000276:immunology*; D000917:Antibody Formation; D001938:Brazil / Q000453:epidemiology; D004797:Enzyme-Linked Immunosorbent Assay; D005982:Glutathione Transferase / Q000032:analysis / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood* / Q000145:classification; D016780:Malaria, Vivax / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control; D020066:Merozoite Surface Protein 1 / Q000032:analysis / Q000276:immunology*; D010219:Papua New Guinea / Q000453:epidemiology; D010966:Plasmodium vivax / Q000276:immunology* / Q000302:isolation & purification; D011994:Recombinant Proteins / Q000276:immunology
chemical_list: D000913:Antibodies, Protozoan; D007074:Immunoglobulin G; D020066:Merozoite Surface Protein 1; D011994:Recombinant Proteins; D005982:Glutathione Transferase