Figure 3. C. volvatus fraction C_M-H-L-5 inhibited PRRSV replication.

(A and B) The C_M-H-L-5 blocked PRRSV Ch1a replication in Marc-145 cells. Marc-145 cells were infected with PRRSV Ch1a at an MOI of 0.1, and then treated with IFN-a (10 units/µl) or the C_M-H-L-5 at various concentrations. At 24 h p.i., cells were fixed and analyzed by IFA using antibody against PRRSV N protein (A), and virus yield in the supernatants was also quantified (B). Culture treated with normal saline was set up as negative control (0 mg/ml), and treated with INF-α was set up as positive control. The brightness of the fluorescence represents the level of the virus. Results are from three independent experiments, each of which was conducted in triplicate. (C) The C_M-H-L-5 potently inhibited both PRRSV HV and VR2332 replication in PAMs. A similar virus inhibition assay was performed with PAM cells infected with PRRSV strain HV or VR2332 at an MOI of 0.1 in the presence of IFN-a (10 units/µl) or the C_M-H-L-5 at various concentrations. (D) Determination of cytotoxicity of the C_M-H-L-5 by MTT assay. PAMs or Marc145 cells were incubated with various concentrations of the C_M-H-L-5 or the control normal saline for 48 h prior to the MTT assay. 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.