Project 1-A novel BSL2 system for studying bunyavirus entry and antigenicity

PROJECT SUMMARY - PROJECT 1 Many viruses in the Order Bunyavirales are zoonotic and pose serious public health challenges. These include rodent-borne hantaviruses and mosquito-borne Rift Valley fever virus (RVFV). Hantaviruses cause hantavirus cardiopulmonary syndrome (HCPS) in the Americas and hemorrhagic fever with renal syndrome (HFRS) in Eurasia. RVFV causes devastating abortion storms in livestock. Human infections can lead to encephalitis and hemorrhagic fever. Endemic in sub-Saharan Africa, RVFV has spread to the Middle East in the last 20 years. The incidence of these viruses in the future is likely to increase due to habitat overlap and expanding vector range. Gn/Gc glycoproteins are the sole viral proteins necessary and sufficient for the cellular entry of these viruses and are also the main targets of protective immune responses. Despite significant research, no FDA-approved vaccines or therapeutics for human use exist for these viruses. Countermeasure development is, at least partly, hindered by the general requirement of Biosafety level-3 (BSL3) containment (and the Select Agent status of RVFV) for research and our limited understanding of their molecular determinants of entry and antigenicity. To enable their research at BSL2, multiple surrogate viruses carrying Gn/Gc proteins have been developed for hantaviruses and RVFV. Currently, these systems are inefficient, and their plasmid-based rescue is incompatible with a more comprehensive reverse genetic analysis of Gn/Gc. Moreover, the bullet-shaped morphology of the commonly used vesicular stomatitis virus (VSV) virions may not preserve lateral contacts (thus immunogenicity) between the Gn/Gc subunits on round/pleomorphic hantavirus and RVFV virions. To make studying hantavirus Gn/Gc easier, we developed a self-replicating BSL2 system that carries hantavirus Gn/Gc as its structural proteins. We recently extended these findings to RVFV to generate a similar virus expressing the RVFV glycoprotein precursor (GPC). We hypothesize that this new system affords DMS analysis of the Gn/Gc's molecular determinants of cellular entry and antigenicity. Using this system, in Aim 1, we plan to map hantavirus Gn/Gc residues critical for cellular entry and antigenicity. In Aim 2, we will characterize the entry pathways and antigenicity of RVFV GPC-expressing virus. These BSL2 systems will unearth novel information about the Gn/Gc residues critical for mediating virus infection, virus-receptor interactions, and eliciting antibody responses. These can be effective tools to screen for therapeutic antibodies and entry inhibitors. They could also serve as potential vaccine candidates. We handle SHV/SRVs at BSL2 using our IBC-approved protocols within a Class II Type A2 biosafety cabinet while wearing appropriate PPE.