Cells expressing HTLV-1 genes, Tax and HBZ, showed different patterns of cytolysis by human γδ T cells and NK cells

KOCK, S; GONZALEZ POLO, VIRGINIA; RUGGIERI, M; QUIROGA, F; FISCH, P; BERINI, C; BIGLIONE, M

Lima

Congreso; HTLV 2019 19th INTERNATIONAL CONFERENCE ON HUMAN RETROVIROLOGY; 2019

Cells expressing HTLV-1 genes, Tax and HBZ, showed different patterns of cytolysis by human γδ T cells and NK cells. Introduction: the most important HTLV-1 viral proteins, HBZ and Tax, regulate not only viral replication but also cell cycle. Human γδ T cells represent 1 to 5% of the peripheral blood lymphocytes, with Vγ9/Vδ2 T cells as the most abundant subset. The majority of them are activated in an HLA-independent manner. Vγ9/Vδ2 activation is achieved after binding of phosphoantigens to the intracellular part of butyrophilin transmembrane molecules.Objective: to determine if HBZ and Tax, expressed by target cells, modulate the cytolitic capacity of human γδ T cells and butyrophilin expression.Methods: β2M FO-1 (melanoma cell line), Myla (CD4+ lymphoid cell line) and Peer (lymphoid cell line) were transduced with constructs encoding the genes HBZ, Tax or both (H-T) and used as target cells. Cloned Vγ9/Vδ2 T cells and polyclonal γδ T cells served as effector cells and natural killer (NK) cells as controls. Cytotoxicity was measured by Cr-51 release assays. Butyrophilin expression was determined by flow cytometry using the monoclonal antibody 103.2.Results: β2M FO-1 cells expressing HBZ, Tax or H-T genes presented higher cytolysis by Vγ9/Vδ2 clones and expanded γδ T cells compared to control. In contrast, β2M FO-1 cells were protected from cytolysis by NK cells when they expressed Tax or H-T, compared to HBZ or control. Furthermore, transduction of β2M FO-1 cells with HBZ, but not with Tax or H-T slightly decreased surface butyrophilin expression, compared to control. Myla cytolysis by expanded γδ T cells was increased only when expressing H-T and, contrary to the cell line β2M FO-1, cytolysis by NK was enhanced when expressing Tax or H-T. Moreover, transfected Peer did not showed differences in cytotoxicity by γδ T cells or NK compared with control. Strikingly, a significant difference in IFN-α release was observed when NK cells were co-cultured with Myla transfected with HBZ, Tax and H-T.Conclusions: Expression of HTLV-1 genes Tax and HBZ by target cells produce different effects over cytolysis by NK and γδ T cells. The effect on γδ T cells is likely not related to an upregulation of surface butyrophilins. Further experiments have to be performed in order to understand the cause of these differences. Nevertheless, the observation of γδ T cells cytotoxicity against cells expressing viral proteins suggest that γδ T cells play a role in the immunosurveillance against HTLV-1. These findings are supported by our results by cDNA spectratyping and by flow cytometry that show decreased proportions of Vδ2 T cells in HTLV-1 patients, even in HTLV-1positive asymptomatic cases.