FIG 5.

NDRG1 knockdown increases PRRSV replication and assembly. (A) PRRSV BJ-4 (MOI = 10) was allowed to bind to the surfaces of sh-control and sh-NDRG1 cells on ice for 1 h. After the cells were washed with PBS, the viral RNA was isolated and quantified by RT-qPCR with ORF7-specific primers. NS, not significant (by an unpaired two-tailed t test). (B) PRRSV BJ-4 (MOI = 10) was allowed to bind to the surfaces of sh-control and sh-NDRG1 cells on ice for 1 h (binding), and cells were then shifted to 37°C for 2 h (internalization). Intracellular viral RNA was isolated and quantified by RT-qPCR using ORF7-specific primers. NS, not significant (by an unpaired two-tailed t test). (C) Cells were infected with PRRSV BJ-4 at an MOI of 10 for the indicated times, before the cells were fixed and stained for double-stranded RNA (dsRNA) and with DAPI. Random fields of view were recorded with a confocal microscope. (D) Fluorescence intensities of dsRNA in panel C were quantified in cells containing PRRSV dsRNA. (E) Cells were infected with PRRSV BJ-4 at an MOI of 10 for 24 h. The efficiency of viral assembly in the supernatants was determined by comparing the infectious titers (TCID₅₀ per milliliter) with the total PRRSV genome equivalents (GE). *, P < 0.05 (by an unpaired two-tailed t test). (F) Cells were infected with PRRSV BJ-4 at an MOI of 10 for 24 h. The efficiency of virus secretion was determined as the ratio of intra- and extracellular infectivity relative to the total infectivity. NS, not significant (by an unpaired two-tailed t test).