FIG 6.

Inhibitory effect of the VLP-immunized sera on virus attachment. Different amounts of the VLP-immunized sera were incubated with 3.8 × 10⁵ TCID₅₀ of EV71 in a 200-μl final volume for 1 h at 37°C. The mixtures were added to RD cells and incubated for 1 h at 4°C for virus attachment. After incubation, unbound virus was carefully washed away. The total RNA of treated cells was then extracted and used for relative quantitation of genome copy of cell-bound EV71 by qRT-PCR as described in Materials and Methods. The y axis shows the ratio of relative EV71 genomic RNA level of antiserum-treated cells to that of the control (cells only infected with the virus). Means ± the standard errors of the mean (SEM) of triplicate wells are shown. The dotted line indicates the background level of the assay. The data are representative results of two independent experiments. Statistical significance was determined by the Student t test and is indicated as follows: n.s., P > 0.05; *, P < 0.05; **, P < 0.01; or ***, P < 0.001.