Methods
To focus the screen onto the entry step, we used non-lytic fluorescent
reporters in combination with a comparative counter screen strategy to
distinguish host genes affecting the pseudoviral reporter from those
unique to envelope-mediated entry. Screening of SARS-CoV-2 spike and
VSV-G on the same lentiviral pseudovirus allowed identification of
entry-specific genes relative to genes associated with
retro-transcription, integration, and reporter expression from the
lentiviral pseudovirus. Second, a Cre-Gag fusion protein in the
pseudovirus was used to bypass retro-transcription and integration by
directly activating a floxed GFP reporter upon entry to reduce the
number of gene hits and increase specificity for viral entry.