title: Human T lymphotropic virus type 1 (HTLV-1) proviral load induces activation of T-lymphocytes in asymptomatic carriers.
abstract: BACKGROUND
  High HTLV-1 proviral load (PVL) is mainly found in infected individuals with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). However one third of asymptomatic carriers may have high PVL. This study aimed to evaluate the impact of PVL in the activation of T lymphocytes of asymptomatic individuals infected with HTLV-1.
  
  
  METHODS
  Membrane activation markers (CD25+, CD28+, CD45RO+, CD69+, CD62L+, HLA-DR+), FoxP3+ and intracellular IFN-γ expression were evaluated on both CD4+ and CD8+ T-lymphocytes from asymptomatic carriers with PVL ≥ and < 1% of infected cells, using flow cytometry. HTLV-1 proviral load was determined using real-time PCR.
  
  
  RESULTS
  Asymptomatic carriers with PVL ≥ 1% presented a higher frequency of CD4+CD25+CD45RO+ (13.2% vs. 4%, p = 0.02), CD4+HLA-DR+ (18% vs. 8.3%, p = 0.01) and CD4+IFN-γ+ (4.5%; 1%, p = 0.01) T-cells, than healthy donors. HTLV-1 PVL was directly correlated with the proportion of CD4+CD25+CD45RO+ T-cells (R = 0.7, p = 0.003). Moreover, a significant increase in the proportion of CD4 + FoxP3+ T-cells was observed in HTLV-1-infected individuals, compared to healthy donors.
  
  
  CONCLUSIONS
  HTLV-1 PVL is associated with activation of both CD4+ and CD8+ T-lymphocytes in asymptomatic individuals. Prospective studies should be conducted to evaluate whether asymptomatic individuals with higher PVL and high immune activation are more prone to developing HTLV-1-associated diseases.
authors.forename: Raimundo
authors.initials: R
authors.lastname: Coutinho
authors.affiliation: Advanced Laboratory of Public Health/CPQGM - Oswaldo Cruz Foundation (FIOCRUZ), Rua Waldemar Falcão, no 121, Candeal, Salvador, Bahia CEP 40296-710, Brazil. grassi@bahia.fiocruz.br.
authors.forename: Maria Fernanda Rios
authors.initials: MF
authors.lastname: Grassi
authors.forename: Ana Beatriz
authors.initials: AB
authors.lastname: Korngold
authors.forename: Viviana Nilla
authors.initials: VN
authors.lastname: Olavarria
authors.forename: Bernardo
authors.initials: B
authors.lastname: Galvão-Castro
authors.forename: Rita Elizabeth
authors.initials: RE
authors.lastname: Mascarenhas
mesh_terms: D058070:Asymptomatic Diseases; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002353:Carrier State / Q000276:immunology* / Q000821:virology; D005434:Flow Cytometry; D006684:HLA-DR Antigens / Q000276:immunology; D015490:HTLV-I Infections / Q000276:immunology* / Q000821:virology; D015368:Human T-lymphotropic virus 1 / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D006801:Humans; D060888:Real-Time Polymerase Chain Reaction; D019562:Viral Load
chemical_list: D006684:HLA-DR Antigens