REGULATION OF MEGAKARYO/THROMBOPOIESIS BY ENDOSOMAL TLR7/TLR8 ACTIVATION OF CD34+ CELLS IN A VIRAL INFECTION MODEL

RODRÍGUEZ, CAMILA SOFÍA; CHARÓ N; TATTI, SILVIO; GOMEZ, RICARDO; D´ATRI LINA PAOLA; SCHATTNER, MIRTA

Congreso; Reunión Conjunta SAIC. SAI. SAFIS; 2022

Background: Although they are not immune cells, hematopoietic progenitor cells (CD34+ cells), megakaryocytes (MKs), and platelets (PLT) express Toll-like receptors (TLRs) that enable these cells to amplify the host innate immune response during infectious or inflammatory processes. However, the role of TLR7/TLR8, which recognizes single-stranded RNA (ssRNA) viruses, in megakaryopoiesis has not yet been investigated. Objectives: We evaluated the effect of the positive sense ssRNA Coxsackievirus B3 (CVB3) and synthetic TLR7/TLR8 agonists on human MK development and PLT production. Methods: CD34+ cells from the human umbilical cord were exposed to CVB3 or UV-irradiated CVB3 virus or stimulated with TLR7 (imiquimod or loxoribine) or TLR8 (TL8-506 or ssPolyU) agonists and cultured in the presence of thrombopoietin. MK viability, caspase-3 activation (flow cytometry) and IL-1beta release from mature MKs was measured 12 days later (ELISA). Inflammatory markers of MKs were evaluated on day 12 of culture (flow cytometry). Results: Cell expansion, differentiation into MKs, MK maturation, and PLT biogenesis, were significantly reduced in CD34+ infected cultures (n=5, p