FIG 9.

Postattachment neutralization by the VLP-immunized sera. EV71 (100 TCID₅₀) was allowed to attach to RD cells for 1 h at 4°C. After washing away unbounded virus, the cells were then incubated for 1 h at 37°C with the VLP-immunized sera at different dilutions as indicated. After three washes, the treated cells were grown at 37°C for 72 h and then observed for CPE or subjected to an MTT assay for cell viability evaluation as described in Materials and Methods. (A) Representative images of cells treated with the indicated antisera at a 1:8 dilution. (B) Viability of the antisera treated cells measured by the MTT assay. The data are means ± the SEM of the OD₄₉₀ readings of four replicate wells. The dash line indicates the cutoff, which is 50% of the OD₄₉₀ reading of the uninfected cells.