Illuminating Lujo virus glycoprotein structure, receptor engagement and neutralizing antibody epitopes

Project Summary The Mammarenavirus genus of the Arenavirus family contains multiple zoonotic pathogens with the potential to cause hemorrhagic fever. These include the South American viruses Junin virus (JUNV; Argentinian hemorrhagic fever) and Machupo virus (MACV; Bolivian hemorrhagic fever), and Lassa virus (LASV), which causes thousands of cases of Lassa Fever in West Africa each year. The case fatality rate for these viruses is 20-70%. Lujo virus (LUJV) is the most recently identified African arenavirus. This virus was responsible for five infections, of which four were fatal. Notably, this outbreak was characterized by human-to-human transmission rather than transmission between rodent and human, as is most common for other arenaviruses. Arenaviruses are genetically and geographically divided into New World (e.g. JUNV and MACV) and Old World (e.g. LASV) groups. Its African location placed LUJV into the OW group. However, LUJV is genetically divergent from other African arenaviruses and is phylogenetically equidistant between the NW and OW groups. Further, its glycoprotein GPC recognizes a different receptor and is antigenically distinct from the other arenaviruses. As the only protein expressed on the viral surface, GPC is responsible for receptor engagement, cell tropism and entry, and is the primary target of antibodies. Understanding the unique structure and surface chemistry of LUJV GPC in its native conformation is key to understanding receptor recognition in the native trimer context, what antibody targets might be on this divergent virus, and how we might design vaccines and therapeutics should the virus re-emerge. The premise of this proposal is that structures of the medically relevant LUJV GP alone and in complex with its cell surface receptor will reveal reasons for its unique cell entry requirements and any differences in its epitope landscape. We will use state-of-the-art biophysical techniques such as cryo electron microscopy, surface plasmon resonance and composition-gradient multiangle light scattering, to characterize the interaction of the prefusion-stabilized LUJV GP trimer (pfGP-TD) with its receptor NRP2. In Aim 2, we will identify antibodies from mice immunized with LUJV pfGP-TD using the Berkeley Lights Beacon platform. Results from the innovative research proposed here will launch multiple lines of inquiry for future studies and will help guide development of vaccines against a diverse range of arenaviruses.