Vascular cell adhesion molecule-1 induced by human T-cell leukaemia virus type 1 Tax protein in T-cells stimulates proliferation of human T-lymphocytes

Human T-cell leukaemia/lymphotropic virus type 1 (HTLV-1), aetiologically l inked to lymphoproliferative as well as inflammatory diseases, infects and activates CD4(+) helper T-cells and thus alters immunoregulatory pathways. The viral regulatory Tax protein has been shown previously to induce the ex pression of vascular cell adhesion molecule-1 (VCAM-1) by T-cells. To deter mine the functional role of this adhesion molecule, Jurkat T-cells stably e xpressing either Tax or both Tax and Rex (another viral regulatory protein) were used in binding and coculture assays performed with either control Ju rkat cells or primary human T-lymphocytes. Evidence was provided that VCAM- 1 acting in synergy with leucocyte function-associated antigen-3 promotes T -cell-T-cell interactions and increases T-cell proliferation. Interestingly , Rex was found to modulate these events. These data establish that VCAM-1 induced by Tax on T-cells thus contributes to the immunopathological proces s triggered by HTLV-1 infection.