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Open Access Research article

Human T lymphotropic virus type 1 (HTLV-1) proviral load induces activation of T-lymphocytes in asymptomatic carriers

Raimundo Coutinho Jr1, Maria Fernanda Rios Grassi12*, Ana Beatriz Korngold1, Viviana Nilla Olavarria2, Bernardo Galvão-Castro12 and Rita Elizabeth Mascarenhas12

Author Affiliations

1 Advanced Laboratory of Public Health/CPQGM – Oswaldo Cruz Foundation (FIOCRUZ), Rua Waldemar Falcão, no 121, Candeal, Salvador, Bahia CEP 40296-710, Brazil

2 Bahiana School of Medicine and Public Health, Salvador, Bahia, Brazil

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BMC Infectious Diseases 2014, 14:453  doi:10.1186/1471-2334-14-453

Published: 22 August 2014

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.

Conclusion

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.

Keywords:
HTLV-1; Proviral load; Asymptomatic; Activation