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

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

Congreso; LXI REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INVESTIGACIÓN CLÍNICA (SAIC) LXIV REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INMUNOLOGÍA (SAI) XLVIII REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE FARMACOLOGÍA EXPERIMENTAL (SAFE); 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