FIG 7.

MNV infection induces the secretion of immune-tolerogenic factors. Neutralization of Gdf15 in the cell culture supernatant resulted in increased cell survival and upregulation of expression of inflammatory and antiviral factors. (A) Representative plot (n = 4) showing the mean results of cell viability assays performed at 30 h p.i. on RAW264.7 cells, mock-, or MNV-infected cells at an MOI of 0.01, 0.1, and 1 and incubated with normal goat IgG or anti-GDF15 antibody from 6 h p.i. onward at the indicated concentrations. Results are shown as means ± SEM, and statistical analysis results are shown above the dots. **, P < 0.0001; ***, P < 0.001. (B) MNV gRNA levels in RAW264.7 cells treated as in panel A were measured using qRT-PCR analysis. Values are means ± SEM, and statistical significance is shown above the bars (n = 3). ****, P < 0.0001; ***, P < 0.001; **, P < 0.01; *, P < 0.1. (C) Representative bar plots (n = 3) of qRT-PCR analysis of innate immune response transcripts levels. Experiment performed on total transcripts from RAW264.7 cells mock or MNV infected at an MOI of 1 for 12 h p.i. and incubated with normal goat IgG or anti-Gdf15 antibody from 6 h p.i. onward. Purified RNAs were reverse transcribed using poly(dT) primer and qPCR performed using exon-junction spanning pair of PCR primer for Tnf, Csf2, Ptgs2, and Mx1 mRNAs indicated. Values are means ± SEM, and statistical significance is shown above the bars. ****, P < 0.0001; ***, P < 0.001; **, P < 0.01; *, P < 0.1.