Autocrine Interferon Priming in Macrophages but Not Dendritic Cells Results in Enhanced Cytokine and Chemokine Production after Coronavirus Infection

Zhou, Haixia; Zhao, Jincun; Perlman, Stanley

MHV induces IFN production in pDC through a TLR7dependent pathway, which signals through MyD88. TLR7 is also expressed in BMM (38) . However, we found that type I IFN production in MHV-infected BMM was not dependent on MyD88 in agreement with a previous report (24) (Fig. 3C) . Further, the levels of MDA5 and RIG-I in MyD88 Ϫ/Ϫ BMM were approximately equal to those found in WT cells, indicating that regulation of in BMDC (C) at different times p.i. were measured by real-time qPCR. C T ratios to HPRT were calculated as described in Materials and Methods. MDA5 and RIG-I were upregulated to a greater extent in BMM than in BMDC (note the differences in scale). Two or three replicates were performed in each experiment, and one of three independent experiments is shown. (B) mRNA was harvested from mock-infected BMM, and basal levels of IFN-␤, MDA5, and RIG-I were measured by real-time qPCR. (C to E) mRNA was harvested 16 h after infection or transfection. mRNA levels were measured by real-time qPCR. C T ratios to HPRT are shown. MHV induced upregulation to a greater extent than poly(I · C) or SenV did (note the differences in scale in panels B to E). Two or three replicates were performed in each experiment, and one of three independent experiments is shown. Values for IFNAR Ϫ/Ϫ or MyD88 Ϫ/Ϫ BMM that were statistically significantly different from the values for wild-type cells are indicated as follows: *, P Ͻ 0.05; **, P Ͻ 0.01. these genes in MHV-infected BMM is not dependent on MyD88 (Fig. 3C ). These findings are not unique for MHV, since expression of IFNAR, but not MyD88, was also required for expression of IFN-␤, MDA5, and RIG-I in BMM that were either transfected with poly(I · C) (Fig. 3D ) or infected with SenV ( Fig. 3E ).