title: High levels of IgG3 anti ICB2-5 in Plasmodium vivax-infected individuals who did not develop symptoms.
abstract: BACKGROUND
  Plasmodium vivax has the potential to infect 2.85 billion individuals worldwide. Nevertheless, the limited number of studies investigating the immune status of individuals living in malaria-endemic areas, as well as the lack of reports investigating serological markers associated with clinical protection, has hampered development of vaccines for P. vivax. It was previously demonstrated that naturally total IgG against the N-terminus of P. vivax merozoite surface protein 1 (Pv-MSP1) was associated with reduced risk of malarial infection.
  
  
  METHODS
  Immune response against Pv-MSP1 (N-terminus) of 313 residents of the Rio Pardo rural settlement (Amazonas State, Brazil) was evaluated in a cross-sectional and longitudinal follow up over two months (on site) wherein gold standard diagnosis by thick blood smear and rRNA gene-based nested real-time PCR were used to discriminate symptomless Plasmodium vivax-infected individuals who did not develop clinical symptoms during a 2-months from those uninfected ones or who have had acute malaria. The acquisition of antibodies against Pv-MSP1 was also evaluated as survival analysis by prospective study over a year collecting information of new malaria infections in surveillance database.
  
  
  RESULTS
  The majority of P. vivax-infected individuals (52-67%) showed immune recognition of the N-terminus of Pv-MSP1. Interesting data on infected individuals who have not developed symptoms, total IgG levels against the N-terminus Pv-MSP1 were age-dependent and the IgG3 levels were significantly higher than levels of subjects had acute malaria or those uninfected ones. The total IgG anti ICB2-5 was detected to be an important factor of protection against new malaria vivax attacks in survival analysis in a prospective survey (p = 0.029).
  
  
  CONCLUSIONS
  The study findings illustrate the importance of IgG3 associated to 2-months of symptomless in P. vivax infected individuals and open perspectives for the rationale of malaria vaccine designs capable to sustain high levels of IgG3 against polymorphic malaria antigens.
authors: Instituto Leônidas e Maria Deane - Fiocruz, Rua Teresina 476, 69057-070 Manaus, AM, Brazil. paulonogueira@amazonia.fiocruz.br.
authors: Fernanda G
authors: FG
authors: Versiani
authors: Maria E M
authors: ME
authors: Almeida
authors: Gisely C
authors: GC
authors: Melo
authors: Francivaldo O L
authors: FO
authors: Versiani
authors: Patrícia P
authors: PP
authors: Orlandi
authors: Luís André M
authors: LA
authors: Mariúba
authors: Leidiane A
authors: LA
authors: Soares
authors: Luciana P
authors: LP
authors: Souza
authors: Antonio A
authors: AA
authors: da Silva Balieiro
authors: Wuelton M
authors: WM
authors: Monteiro
authors: Fabio T M
authors: FT
authors: Costa
authors: Hernando A
authors: HA
authors: del Portillo
authors: Marcus V G
authors: MV
authors: Lacerda
authors: Paulo A
authors: PA
authors: Nogueira
mesh_terms: D000293:Adolescent; D000328:Adult; D000913:Antibodies, Protozoan / Q000097:blood*; D058070:Asymptomatic Diseases; D001938:Brazil; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D016780:Malaria, Vivax / Q000276:immunology* / Q000473:pathology; D008297:Male; D020066:Merozoite Surface Protein 1 / Q000276:immunology*; D008853:Microscopy; D018512:Parasitemia / Q000175:diagnosis; D011446:Prospective Studies; D012424:Rural Population; D016019:Survival Analysis; D055815:Young Adult
chemical_list: D000913:Antibodies, Protozoan; D007074:Immunoglobulin G; D020066:Merozoite Surface Protein 1
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