title: Analysis of lymphocytes in patients with Plasmodium vivax malaria and its relation to the annexin-A1 and IL-10.
abstract: BACKGROUND
  Malaria is the most prevalent parasitic disease in the world. In Brazil, the largest number of malaria cases (98%) is within the Legal Amazon region, where Plasmodium vivax is responsible for over 80% of diagnosed cases. The aim of this study was to investigate the annexin-A1 expression in CD4+, CD8+ T cells, regulatory T cells (Treg) and cytokine IL-10 quantification in plasma from patients with malaria caused by P. vivax.
  
  
  METHODS
  The quantification of the cytokine IL-10 of patients infected with P. vivax and healthy controls were evaluated by enzyme-linked immunosorbent assay (ELISA). The determination of the expression of annexin-A1 in lymphocytes from patients and healthy controls was determined by immunofluorescence staining. All results were correlated with the parasitaemia and the number of previous episodes of malaria.
  
  
  RESULTS
  The cytokine IL-10 plasma levels showed a significant increase in both patients with low (650.4 ± 59.3 pg/mL) and high (2870 ± 185.3 pg/mL) parasitaemia compared to the control (326.1 ± 40.1 pg/mL). In addition, there was an increase of this cytokine in an episode dependent manner (individuals with no previous episodes of malaria--primoinfected: 363.9 ± 31.1 pg/mL; individuals with prior exposure: 659.9 ± 49.4 pg/mL). The quantification of annexin-A1 expression indicated a decrease in CD4+ and CD8+ T cells and an increase in Treg in comparison with the control group. When annexin-A1 expression was compared according to the number of previous episodes of malaria, patients who have been exposed more than once to the parasite was found to have higher levels of CD4+ T cells (96.0 ± 2.5 A.U) compared to primoinfected (50.3 ± 1.7). However, this endogenous protein had higher levels in CD8+ (108.5 ± 3.1) and Treg (87.5 ± 2.5) from patients primoinfected.
  
  
  CONCLUSIONS
  This study demonstrates that in the patients infected with P. vivax the release of immunoregulatory molecules can be influenced by the parasitaemia level and the number of previous episodes of malaria. annexin-A1 is expressed differently in lymphocyte sub-populations and may have a role in cell proliferation. Furthermore, annexin-A1 may be contributing to IL-10 release in plasma of patients with vivax malaria.
authors.forename: Quessi I
authors.initials: QI
authors.lastname: Borges
authors.forename: Cor J F
authors.initials: CJ
authors.lastname: Fontes
authors.affiliation: Post-graduation in Health Science, Faculty of Medicine (FM), Federal University of Mato Grosso (UFMT), Cuiabá, Mato Grosso 78060-900, Brazil. asdamazo@yahoo.com.br.
authors.forename: Amílcar S
authors.initials: AS
authors.lastname: Damazo
mesh_terms: D000328:Adult; D017305:Annexin A1 / Q000096:biosynthesis*; D001938:Brazil; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005455:Fluorescent Antibody Technique; D064368:Healthy Volunteers; D006801:Humans; D016753:Interleukin-10 / Q000097:blood*; D016780:Malaria, Vivax / Q000276:immunology*; D008297:Male; D010966:Plasmodium vivax / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000276:immunology*
chemical_list: D017305:Annexin A1; C508609:IL10 protein, human; D016753:Interleukin-10