SHORT COMMUNICATION: HUMAN BONE MARROW STROMAL CELLS EXHIBIT IMMUNOSUPPRESSIVE EFFECTS ON HTLV-1 T-LYMPHOCYTE FROM INFECTED INDIVIDUALS.

Human multipotent mesenchymal stromal cells (MSC) display immunoregulatory functions that can modulate innate and adaptive cellular immune responses. The suppressive and immunomodulatory activities of MSC occur by the action of soluble factors that are constitutively produced and released by these cells or alternatively, after MSC induction by stimuli of inflammatory microenvironments. However, up to date it is unknown the contribution of MSCs in the inflammatory microenvironment resulting from viral infection. In our study, we evaluated the MSC immunosuppressive effect on HTLV-1 infected T lymphocytes. To evaluate if MSC immunoregulation can influence the proliferation of HTLV-1 infected T lymphocytes, we compared the proliferation of lymphocytes obtained from HTLV-1 infected and healthy individuals co-cultured in the presence of MSC. It was observed that the lymphoproliferative inhibition by MSC on infected lymphocytes was similar compared to the cells obtained from healthy individuals. Additionally, this suppressive effect was related to a significant increase of IDO and PGE2 gene expression (p≤0.05). Furthermore, the HTLV-1 pol gene were less expressed after coculturing with MSC, suggesting that the MSC immunoregulation can have effective suppression on HTLV-1 infected T cells. In conclusion, this study suggests that MSC could be involved in the immunomodulation of the HTLV-1 infected T lymphocytes.