Human B cell infection by pathogenic Old and New World Hantaviruses

MARTINEZ V; BASSI SC; GARCÍA M; KLINGSTRÖM J; GUPTA S; MALEKI K; SCHIERLOH P; IGLESIAS A; SOLÀ RIERA C

Encuentro; KI Infection Retreat; 2017

Karolinska Institutet

Aim: The aim of this project is to evaluate human B cells as alternative targets of hantavirus infection and the implications this might have in the pathogenesis of Hemorrhagic Fever with Renal Syndrome (HFRS) and Hantavirus Pulmonary Syndrome (HPS).Introduction: Hantavirus are enveloped RNA viruses that belong to the Bunyaviridae family. They are classified in two groups: Old World and New World hantaviruses. The first group is responsible for HFRS, mainly in Europe and Asia. The New World hantaviruses, on the other hand, are responsible for HPS in the Americas. The main target of infection are microvascular endothelial cells. In previous studies, we observed a massive polyclonal activation of circulating B cells in HPS patients from Argentina and an increased risk for B cell lymphoma related to HFRS history in Sweden, which led us to question if these cells may constitute an alternative target for hantavirus infection.Methods: To test this hypothesis, purified normal B cells from blood donors were exposed to HTNV, ANDV and PUUV strains at a multiplicity of infection of 1. Supernatants and cells were then collected at different timepoints (6, 24, 48 and 72hs post infection). To asses for infection, cells were lysed for western blot detection of the nucleocapsid protein (NP) or processed for immunofluorescence detection of intracellular NP by confocal microscopy. To test for production of progeny virus, supernatants were assayed for production of focus forming units. On the other hand, B cells were co-cultured with HTNV infected endothelial target cells (HUVEC, 3dpi) and surface activation markers were analyzed on B cells by FACS after 24hs.Results: In vitro infection showed that B cells are susceptible to infection by both Old World and New World hantaviruses. Additionally, Old World hantaviruses cause productive infectivity, as shown by increased progeny titers over time after infection. Furthermore, B cells showed increased levels of CD69 surface expression when co-cultured with infected endothelial cells, indicating activation within 24hs of co-incubation.Conclusion: These results indicate that human B cell constitute an alternative cell target for both Old and New World hantaviruses with secretion of fully functional infectious virions (productive infection). This novel finding could entail B cell involvement in disease pathogenesis and thus, further studies are required.