Research
Induction of galectin-1 expression by HTLV-I Tax and its impact on HTLV-I infectivity
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* Corresponding author: Benoit Barbeau barbeau.benoit@uqam.ca
1 Research Center in Infectious Diseases, CHUL Research Center, 2705 boul. Laurier; Ste-Foy, Québec, G1V 4G2, Canada
2 Université du Québec à Montréal, Département des sciences biologiques, 2080 St-Urbain, Montréal, Québec, H2X 3X8, Canada
Retrovirology 2008, 5:105 doi:10.1186/1742-4690-5-105
Published: 25 November 2008Abstract
Background
Cell-free Human T-cell Leukemia Virus type I (HTLV-I) virions are poorly infectious and cell-to-cell contact is often required to achieve infection. Other factors might thus importantly contribute in increasing infection by HTLV-I. Galectin-1 is a galactoside-binding lectin which is secreted by activated T lymphocytes. Several functions have been attributed to this protein including its capacity to increase cell-to-cell adhesion. Based on previous studies, we postulated that this protein could also accentuate HTLV-I infection.
Results
Herein, we demonstrate that galectin-1 expression and release are higher in HTLV-I-infected T cells in comparison to uninfected T cells. Furthermore, galectin-1 expression was activated in various cell lines expressing the wild type viral Tax protein while this induction was minimal upon expression of NF-κB activation-defective TaxM22. Cotransfection of these Tax expression vectors with galectin-1 promoter-driven luciferase constructs confirmed that Tax upregulated galectin-1 promoter activity. However, a NF-κB-independent mechanism was strongly favoured in this induction of galectin-1 expression as no activation of the promoter was apparent in Jurkat cells treated with known NF-κB activators. Using HTLV-I envelope pseudotyped HIV-1 virions, galectin-1 was shown to increase infectivity. In addition, a co-culture assay with HTLV-I-infected cells also indicated an increase in cell fusion upon addition of galectin-1. This effect was not mediated by factors present in the supernatant of the HTLV-I-infected cells.
Conclusion
These data suggest that HTLV-I Tax increases galectin-1 expression and that this modulation could play an important role in HTLV-I infection by stabilizing both cell-to-cell and virus-cell interactions.