Figure 4. Cryptoporus volvatus extract inhibits PRRSV release and cell-to-cell spreading.

Determination of viral RNA released to the supernatants (A) or intracellular (B). Marc-145 cells were infected with PRRSV Ch1a (MOI of 0.1) for 24 h. After washing with PBS, cells were treated with either Cryptoporus volvatus extract or BFA (a known inhibitor of protein transport) for 0.5, 1, or 3 hours, and then copies of viral RNA in the supernatants and in the cells were determined using quantitative real-time RT-PCR assay. (C) PRRSV cell-to-cell spread is inhibited by Cryptoporus volvatus extract in a dose-dependent manner. Marc145-cells were incubated with CH-1a strain (MOI = 0.01) for 3 h at 37°C, and then culture medium was replaced with fresh medium containing Cryptoporus volvatus extract at indicated concentrations and neutralizing antibody (10% vol/vol). PRRSV N protein expression in cells was observed using indirect immunofluorescence at 24 hours after infection. Micrographs chosen to illustrate the sizes of infected cell foci (N expression, green). (D) Average number of infected cells per foci. Data are representative of three independent experiments (mean ± SD). Statistical significance was analyzed by Student’s t test; *P<0.05; **P<0.01; ***P<0.001.