title: CD4+ T cells apoptosis in Plasmodium vivax infection is mediated by activation of both intrinsic and extrinsic pathways.
abstract: BACKGROUND
  Reduction in the number of circulating blood lymphocytes (lymphocytopaenia) has been reported during clinical episodes of malaria and is normalized after treatment with anti-malaria drugs. While this phenomenon is well established in malaria infection, the underlying mechanisms are still not fully elucidated. In the present study, the occurrence of apoptosis and its pathways in CD4+ T cells was investigated in naturally Plasmodium vivax-infected individuals from a Brazilian endemic area (Porto Velho - RO).
  
  
  METHODS
  Blood samples were collected from P. vivax-infected individuals and healthy donors. The apoptosis was characterized by cell staining with Annexin V/FITC and propidium iodide and the apoptosis-associated gene expression profile was carried out using RT2 Profiler PCR Array-Human Apoptosis. The plasma TNF level was determined by ELISA. The unpaired t-test or Mann-Whitney test was applied according to the data distribution.
  
  
  RESULTS
  Plasmodium vivax-infected individuals present low number of leukocytes and lymphocytes with a higher percentage of CD4+ T cells in early and/or late apoptosis. Increased gene expression was observed for TNFRSF1B and Bid, associated with a reduction of Bcl-2, in individuals with P. vivax malaria. Furthermore, these individuals showed increased plasma levels of TNF compared to malaria-naive donors.
  
  
  CONCLUSIONS
  The results of the present study suggest that P. vivax infection induces apoptosis of CD4+ T cells mediated by two types of signaling: by activation of the TNFR1 death receptor (extrinsic pathway), which is amplified by Bid, and by decreased expression of the anti-apoptotic protein Bcl-2 (intrinsic pathway). The T lymphocytes apoptosis could reflect a strategy of immune evasion triggered by the parasite, enabling their persistence but also limiting the occurrence of immunopathology.
authors.forename: Natália S
authors.initials: NS
authors.lastname: Hojo-Souza
authors.forename: Dhelio B
authors.initials: DB
authors.lastname: Pereira
authors.forename: Tiago A O
authors.initials: TA
authors.lastname: Mendes
authors.forename: Lívia S A
authors.initials: LS
authors.lastname: Passos
authors.forename: Ana Clara
authors.initials: AC
authors.lastname: Gazzinelli-Guimarães
authors.forename: Pedro H
authors.initials: PH
authors.lastname: Gazzinelli-Guimarães
authors.forename: Mauro S
authors.initials: MS
authors.lastname: Tada
authors.forename: Graziela M
authors.initials: GM
authors.lastname: Zanini
authors.forename: Daniella C
authors.initials: DC
authors.lastname: Bartholomeu
authors.forename: Ricardo T
authors.initials: RT
authors.lastname: Fujiwara
authors.affiliation: Department of Parasitology, Institute of Biological Science, Federal University of Minas Gerais, Av, Antônio Carlos 6627, 31270-901 Belo Horizonte, Minas Gerais, Brazil. lilacerdabueno@gmail.com.
authors.forename: Lilian L
authors.initials: LL
authors.lastname: Bueno
mesh_terms: D000328:Adult; D017209:Apoptosis; D001938:Brazil; D015496:CD4-Positive T-Lymphocytes / Q000502:physiology*; D003584:Cytological Techniques; D005260:Female; D020869:Gene Expression Profiling; D054884:Host-Pathogen Interactions; D006801:Humans; D016780:Malaria, Vivax / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis*; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000096:biosynthesis*; D015398:Signal Transduction; D055815:Young Adult
chemical_list: D019253:Proto-Oncogene Proteins c-bcl-2; D047888:Receptors, Tumor Necrosis Factor, Type I