PF4 and infection: To determine whether PF4 inhibits the replication of CA6 and EVD68, human embryonic kidney (HEK293T) cells were transfected with PF4 tagged with hemagglutinin (HA) or VR1012 (negative control) plasmids, then infected with CA6 or EVD68 at a multiplicity of infection (MOI) of 0.5 and 1.0, respectively.