FIG. 3.

System to test vRNP virion incorporation efficiencies. VLPs were recovered from 293T cells transfected with eight PolI constructs for the eight RNA segments PB1, PB2, PA, NA, M, NS, HA-GFP, and NP(Met⁻), which lacks a start codon. These VLPs were used to infect MDCK cells in the presence of helper virus (left). In this experimental setting, GFP-positive MDCK cells are representative of VLPs that contain at least one vRNA segment (i.e., the HA-GFP vRNA). In a parallel experiment, VLPs derived from 293T cells were used to infect MDCK cells expressing NP (right). In this experimental setting, GFP-positive MDCK cells are indicative of VLPs that possess at least four vRNAs (i.e., the PB2, PB1, PA, and HA-GFP vRNAs).