Disruption of Phosphatidylserine Synthesis or Trafficking Reduces Infectivity of Ebola Virus

The outer leaflet of the viral membrane of Ebola virus (EBOV) virions is enriched with phosphatidylserine (PtdSer), which is thought to play a central role in viral tropism, entry, and virus-associated immune evasion. We investigated the effects of inhibiting synthesis and/or export of PtdSer to the cell surface of infected cells on viral infectivity. Knockdown of both PtdSer synthase enzymes, PTDSS1 and PTDSS2, effectively decreased viral production. Decreased PtdSer expression resulted in an accumulation of virions at the plasma membrane and adjacent of intracellular organelles, suggesting that virion budding is impaired. The addition of inhibitors that block normal cellular trafficking of PtdSer to the plasma membrane resulted in a similar accumulation of virions and reduced viral replication. These findings demonstrate that plasma membrane-associated PtdSer is required for efficient EBOV budding, increasing EBOV infectivity, and could constitute a potential therapeutic target for the development of future countermeasures against EBOV.