B. abortus RNA: a novel vit-PAMP involved in the down-modulaton of MHC-I expression on human monocytes

M. AYELÉN MILILLO; LIS N. VELÁSQUEZ; ALDANA TROTTA; M. VICTORIA DELPINO; LUCIANA BALBOA; GUILLERMO H. GIAMBARTOLOMEI; PAULA BARRIONUEVO

Congreso; LXI Reunión Científica Anual de la Sociedad Argentina de Investigación Clínica. LXIV Reunión Anual de la Sociedad Argentina de Inmunología. XLVIII Reunión Anual de la Sociedad Argentina de Farmacología Experimental.; 2016

Brucella abortus elicits a strong Th1 immune response which activates cytotoxic T lymphocytes. However, this pathogen is able to survive inside macrophages and generate a chronic infection. Previously we reported that infection of human monocytes/macrophages with B. abortus inhibits the IFN-γ-induced MHC-I cell surface expression. More importantly, we have recently demonstrated that B. abortus RNA, described as a viability-associated (vita)-PAMP, is the bacterial component involved in this phenomenon. Thus, the aim of this study was to further characterize the component, signalling pathways and mechanisms implicated in MHC-I down-modulation. For this, RNases-treated B. abortus RNA was employed to stimulate human monocytic THP-1 cells in the presence of IFN-γ for 48 h. Then, the expression of MHC-I molecules was evaluated by flow cytometry. Surprisingly, completely degraded RNA was still able to inhibit MHC-I expression (p