Arterivirus receptors: rules of engagement for cross-species infection

PROJECT SUMMARY/ABSTRACT As COVID-19 has illustrated, the emergence of novel RNA viruses from wild animals poses a significant threat to human health. In this proposal, we will begin to assess the zoonotic potential of an entire family of viruses: the arteriviruses. The arteriviruses are the only mammalian RNA virus family not known to infect humans; as such they have been largely ignored by the biomedical research community. However, these viruses cause severe disease in many other mammals including monkeys. Due to historical neglect, the research community has not developed the resources and knowledge that would be required to rapidly develop medical countermeasures in the event of an arterivirus emergence in humans. Thus, these viruses are uniquely positioned in our pandemic preparedness blindspot. In this project we will characterize the zoonotic risk posed by arteriviruses using a diverse collection of arteriviruses and variety of host tools. In Aim 1, we will build upon our recent discoveries that identified CD163 as a host molecule required for arterivirus entry into cells. We will create a panel of cells expressing CD163 orthologs from various species (human, monkey, mouse, pig) and examine the susceptibility of these cells to a panel of arteriviruses. Next, we will create CD163 molecules with mutations and deletions to map the key domains and residues required for arterivirus binding. Finally, we will use our knowledge of CD163 to try and grow novel arterivirus isolates that so far cannot be grown in culture. In Aim 2, we will build upon our recent discovery that the neonatal Fc receptor (FcRn) is required for arterivirus infection of cells. We hypothesize that FcRn acts as an attachment factor, allowing the virus to adhere to the cell surface and become internalized in the endosomal compartment where it contacts CD163. To test this, we will perform a series of binding and internalization assays (in the presence and absence of CD163) to establish a role of FcRn as a pan-arterivirus attachment factor. We will also overexpress CD163 and FcRn in the background of FcRn- and CD163-knockout cells to determine if these molecules are each required in sequential fashion or are redundant for arterivirus infection. Finally, we will perform a pair-wise species comparison of FcRn orthologs and divergent arteriviruses to examine whether FcRn acts as a barrier to cross-species infection. Upon conclusion of this project we will have a greater appreciation for the zoonotic risk posed by these viruses. We will also have developed tools, biological systems, and knowledge that will serve as a critical resource for the rapid development of life-saving medical countermeasures in the event of an arterivirus outbreak in humans.