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Abstract
Lassa Virus (LASV) and Ebolavirus (EBOV) are two of the most globally threatening emerging pathogens. These pathogens continually circulate in animal reservoirs and future zoonotic crossover events are a certainty. Therefore, there is a critical need for rapidly adaptable vaccine and antiviral platforms to control ongoing and prevent future outbreaks. An optimal way to prevent a virus from establishing infection in the human host is to inhibit virus-cell entry. This stage in the viral replication cycle is typically mediated by viral glycoproteins (GPs), which coat the viral envelope and are the only viral proteins exposed to the extracellular environment. Viral glycoprotein functional domains, particularly the RBDs, are ideal targets for therapeutics (e.g. neutralizing antibodies) because they are accessible outside of the cell and are essential for viral replication. Many viruses, including LASV and EBOV, can also bind to cell surfaces using phosphatidylserine receptors (PSRs), which interact with phosphatidylserine (PS) in the viral envelope. This strategy is termed apoptotic mimicry because PSRs mediate the uptake and clearance of PS-coated apoptotic cells and debris. Several groups demonstrated that increasing the amount of PSRs on cell surfaces enhances viral entry or confers virus susceptibility to cells. Less clear, however, is how viral envelopes acquire PS. Unlike viral glycoproteins, which are encoded in the viral genome, envelopes are pinched off directly from host cell membranes during budding. To better understand and target LASV and EBOV entry, we aim to 1) characterize the LASV receptor binding site within glycoprotein subunit 1 (GP1) using site-directed mutagenesis, 2) define specific cellular PS scramblases required for external EBOV envelope PS, and 3) investigate the role of cellular PS flippases in EBOV replication.