Virus-host interactions : entry and replication of Crimean-Congo hemorrhagic fever virus

Crimean-Congo hemorrhagic fever (CCHF) is a severe acute human disease with potential lethal outcome caused by a virus, Crimean-Congo hemorrhagic fever virus (CCHFV). Not much is known regarding how CCHFV infects cells, replicates and why it cause vascular dysfunction. To better understand CCHFV- pathogenesis increased knowledge regarding these issues is needed. Viruses have to enter a host cell in order to replicate its genome and here we show that CCHFV entry occur by clathrin-mediated endocytosis and is pH- dependent. A new in situ detection technique was establihed to visualize individual CCHFV cRNA and vRNA transcripts. Potential colocalization with the viral nucleocapsid protein (NP) was also investigated. cRNA was found to be more concentrated to particular regions within the cytoplasm and co-localized with CCHFV NP. While vRNA was detected throughout the cytoplasma not colocalizating with CCHFV NP. It is not known if the vascular leakage observed in CCHF is due to direct virus infection or is immune-mediated. A new in vitro model system was therefore established and it was found that CCHFV has a preference for basolateral entry. However and surprisingly, using CCHFV-infected monocyte-derived dendritic cells (moDCs) or their supernatant, a preference for apical entry was observed. This indicate that the change in entry site could be due to soluble factors from the moDCs. Neither direct infection nor addition of CCHFV-infected moDCs affected the cellular permeability of the human polarized epithelial cell layer, indicating that other factors are most likely are causing the vascular leakage. Taken together, we established several new in vitro model systems to study CCHFV’s interaction with host cells. We also demonstrated the entry pathway for CCHFV into cells. These data and tools will hopefully facilitate and promote research on virus-host interactions which in turn may result in the development of new antivirals and/or vaccines against CCHFV