Fig. 4. Inhibition of LRP1 yields virions with enhanced infectivity.

(A) Efficient LRP1 knockdown at the RNA level: Fibroblasts were transfected with an LRP1-specific siRNA or left untreated. 24 h later, cells were infected (5 IU/cell); and then, after the indicated time intervals, RNA was isolated and assayed by real-time qPCR to determine the levels of LRP1 transcripts. Samples were normalized to GAPDH RNA. Infected cell RNA levels are presented relative to mock.

(B) Efficient LRP1 knockdown at the protein level: Fibroblasts were transfected with an LRP1-specific or scrambled control siRNA. 24 h later, cells were infected, and, after an additional 24 h, whole cell lysates were prepared and assayed by Western blot for LRP1.

(C-D) siRNA-mediated LRP1 knockdown produces enhanced yields of infectious HCMV: Fibroblasts were infected (0.1 IU/cell) at 24 h post transfection with the indicated siRNAs or no siRNA. 96 h later, virus in the medium was assayed by IE1 fluorescence in cultures where nuclei were identified by Hoechst staining (C) or TCID₅₀ assay (D).

(E) Neutralizing antibody to LRP1 produces enhanced yields of infectious HCMV. Fibroblasts were infected (0.1 IU/cell) at 1h after treatment with the indicated antibodies (Ab), and cell-free virus was quantified by a TCID₅₀ assay 96 h later.

(F) LRP1 knockdown generates virions with enhanced infectivity. Particle to IU ratios were calculated by dividing the amount of DNA in virus particles by the virus titer.

Error bars report the standard errors of the means from three experiments, each performed in triplicate. **P<0.001 (t-test, compared to control condition). Fig. S1 contains additional data relevant to this experiment.