4-parameter dose response – inhibition nonlinear regression equation  (GraphPad Software Inc)

Journal: PLoS ONE

Article Title: A Novel Compound from the Mushroom Cryptoporus volvatus Inhibits Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) In Vitro

doi: 10.1371/journal.pone.0079333

Figure Lengend Snippet: (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.

Article Snippet: The 50% effective concentration (EC 50 ) was determined using a 4 parameter, nonlinear regression of dose response inhibition by plotting log (inhibitor(-concentration)) vs. virus titer (variable slope) using GraphPad Prism (GraphPad Software, San Diego, CA).

Techniques: Infection, Virus, Saline, Negative Control, Positive Control, Fluorescence, Inhibition, MTT Assay, Incubation, Control