Host-virus interactions in hantavirus glycoprotein assembly

PROJECT SUMMARY/ABSTRACT Rodent-borne orthohantaviruses (hereafter, hantaviruses) are an important group of zoonotic bunyaviruses associated with over 50,000 annual diagnosed cases of disease worldwide, primarily caused by rodent-to-human transmission, but also by direct human-to-human contact. Infections by some hantaviruses are associated with severe disease with up to 40% case-fatality rates. No FDA-approved countermeasures are currently available to prevent or treat hantavirus infections and disease. Hantaviruses and other members of the order Bunyavirales (bunyaviruses) encode complex membrane polyproteins that undergo processing and maturation to liberate virion-incorporated glycoprotein complexes (Gn/Gc). The Gn/Gc complexes mediate viral entry and are the major targets of the antiviral host antibody response and therapeutic antibodies. Despite their critical roles and the likelihood that their interactions with host factors provide conserved Achilles' heels for the development of broadly acting antivirals, the biogenesis and vesicular trafficking of Gn/Gc complexes remain poorly understood. Here, we propose to delineate the mechanisms of intracellular assembly, maturation, trafficking, and activity of glycoprotein complexes from four rodent-infecting hantaviruses representing the Old and New World clades and causing two distinct human diseases. These complexes are assembled in the ER and then transit to the Golgi complex, where they are retained to assemble into virions. Our previous studies have identified a) key mutations in the Old-World Hantaan virus (HTNV) Gn/Gc that relocalize a substantial amount of Gn/Gc to the plasma membrane, and b) multiple members of the ER membrane complex (EMC) as hits in a haploid genetic screen for host factors for the New-World Andes virus (ANDV). Using a combination of genetic, virologic, and mass-spectrometric approaches, our interdisciplinary team plans to identify and define virus-host interactions required for ER/Golgi retention of Gn/Gc proteins and elucidate the role(s) of the EMC in viral entry and replication. Our long-term goals are to generate fundamental knowledge about the mechanisms of glycoprotein biogenesis and function that drive hantavirus infection and create novel avenues for therapeutic intervention against these agents.