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

In contrast, mRNA expression of MDA5, RIG-I, CXCL10, and ISG15 was lower at 16 h p.i. in BMDC than after IFN treatment alone ( Fig. 6C and D) . No IFN protein was produced at any time after MHV infection in BMDC or 17Cl-1 cells, so exogenous IFN greatly enhanced expression of these genes in both cell types. The lower levels observed in infected BMDC resulted only in part from an inability to produce IFN because even when we treated these cells with IFN-␤, cytokine expression was still much lower than detected in MHV-infected BMM (Fig. 6C and D) . Furthermore, virus replication and IFN acted synergistically only in enhancing CXCL10 expression, with maximal levels obtained when MHVinfected BMDC or 17Cl-1 cells were treated with IFN. Consistent with analyses of IFNAR Ϫ/Ϫ cells (Fig. 5A) , TNF expression was not upregulated by IFN treatment in any cell type in the presence or absence of MHV infection (Fig. 6E) .