Hantavirus-infected endothelium induce B cell priming and increased survival

GARCIA M.; SOLÀ RIERA C; MALEKI K; IGLESIAS A; GUPTA S; MARTINEZ V; SCHIERLOH P

Dresden

Simposio; B Cells: Mechanisms in Immunity and Autoimmunity (E4); 2018

Keystone Symposia

Hantavirus are enveloped RNA viruses belonging to the Bunyaviridae family. They are classified as Old World and New World hantaviruses. The first are responsible for Hemorrhagic Fever with Renal Syndrome (HFRS), whereas the latter are responsible for Hantavirus Pulmonary Syn¬drome (HPS). The main known target of infection are microvascular endothelial cells. Hantaan (HTNV) and Andes (ANDV) virus are representative strains responsible for HFRS and HPS, respectively. In previous studies, we observed a massive polyclonal activation of circulating B cells in HPS patients from Argentina. Thus, the aim of this study was to evaluate if and how hantavirus infected endothelial cells can have a role in B cell. To test this hypothesis B cells were co-cultured with HTNV-infected endothelial cells (EC, HUVEC and HMVEC-L, 3dpi) either directly (contact) or via a transwell system (TW). Additionally, B cells were exposed to infected EC conditioned medium (HTNV-CM). As controls, EC were exposed both to UV inactivated HTNV or medium alone. B cells were collected 24 to 72hs post co-culture and assessed by flow cytometry.All HTNV-infected conditions (contact, TW and CM) showed elevated levels of CD69+ B cells compared to controls after 24hs of co-culture, suggesting that HTNV-EC secrete soluble B cell activating factors. In line with this, augmented levels of CD71+ and BAFF-R+ B cells were also observed, compared to controls. Longer term HTNV-CM co-culture (72hs) showed even higher levels of CD69+ B cells. Interestingly, while BAFFR+ B cell levels decreased with time after co-culture in controls, these remained elevated in the HTNV-CM condition. Together with this, higher levels of live B cells were observed at 72hs post HTNV-CM vs controls, suggesting a secretion of proliferative and/or survival factors for B cells by HTNV-EC. Furthermore, increased levels of IL-6 and BAFF -B cell activating and pro-survival cytokines- were measured in supernatants from HTNV-EC compared to controls, constituting possible mediators of B cell activation by HTNV-EC. In conclusion, hantavirus infected EC can activate B cells. These results suggest possible mechanisms involved in the polyclonal activation of B cells observed in HPS patients.