A system to rapidly develop a bunyavirus pseudotyped virus neutralisation assay for pandemic preparedness

Several Bunyavirales families have been listed as being of high pandemic or epidemic risk by the WHO R&D Blueprint. To support pandemic preparedness and the 100 Days Mission, along with rapid provision of vaccines and therapeutics, the development of tools to assess the immune response is required. Pseudotyped viruses (PV) have been shown to be a suitable alternative to authentic infectious virus to measure virus-neutralising activity, a key component of the immune response. They alleviate the need to acquire and amplify viral isolates and do not require high containment facilities. Generating PV of some families within the class Bunyaviricetes is challenging because of a lack of co-localisation of viral glycoproteins at the vector budding site. Here, we describe a versatile plug-and-play system focusing on two prototype viruses for the family Phenuiviridae, Rift Valley fever virus (RVFV) and for the family Nairoviridae, Crimean-Congo haemorrhagic fever virus (CCHFV). Shared key parameters for the production of RVFV and CCHFV PV were identified and optimised on a single-cycle, recombinant vesicular stomatitis virus vector (VSV), which allowed for the successful and rapid production of PV for Dabie bandavirus and Oropouche virus. We propose that this system could be successfully applied to other high-consequence bunyaviruses, including those yet unknown, which may emerge in the future. Assessment of the novel bunyavirus PV generated here demonstrated a good correlation with traditional neutralisation assays with infectious virus. This system offers an adaptable and widely accessible platform that can be rapidly developed in response to emerging viral threats.