Fig 3.

Relative RNA expression levels of chemokines (CXCL9, CXCL10, and CXCL11), cytokines (IL1β, IL6, and IFNβ1), and IFNβ1-inducible genes (OAS1 and Mx1) in human and pig respiratory epithelial cells and macrophages. Human and pig cells were infected with HPAI H5N1 (A/turkey/Turkey/1/05) and USSR H1N1 (A/USSR/77) viruses at an MOI of 1.0. (A) In human epithelial cells, CXCL9, CXCL10, and CXCL11 were clearly induced by both viruses at comparable levels. However, chemokine induction was absent or barely detected in pig epithelial cells. (B) In human macrophages, all three chemokines were comparably induced by both virus subtypes. Again, in pig macrophages, chemokine induction was absent or weak. (C) IL1β mRNA expression was consistently upregulated in pig epithelial cells infected by both virus subtypes. In infected human epithelial cells, IL1β induction was relatively limited. (D) In pig macrophages, 1L1β mRNA expression was clearly induced by both viruses. IL1β expression in human macrophages, like human epithelial cells, appeared less responsive to HPAI H5N1 and USSR H1N1 infections than their pig counterparts. (E) In human epithelial cells, at 24 h after infection with HPAI H5N1 virus, IL6 induction was consistently pronounced, but in infected pig cells, IL6 expression levels showed a wide variation between experimental repeats. (F) IL6 expression in 24-h H5N1 virus-infected pig macrophages, however, was more highly upregulated than in their human counterparts. (G) In pig epithelial cells, the HPAI H5N1 subtype induced a stronger and increasing IFNβ1 response, but in human HPAI H5N1 virus-infected cells, IFNβ1 induction was less pronounced. USSR H1N1 virus also induced an increasing IFNβ1 response in pig cells; in human USSR H1N1 virus-infected cells, the level of IFNβ1 induction was higher at 24 h but lower at 48 h than those in the corresponding pig cells. (H and I) In both human and pig cells infected with USSR H1N1 virus, the levels of OAS1 (H) and Mx1 (I) expression closely mirrored the relative expression level of IFN-β1. A clear induction of OAS1 and Mx1 by the HPAI H5N1 subtype was found only in human cells at both time points; in HPAI H5N1 virus-infected pig cells, OAS1 and Mx1 were barely detected. Data shown are the means of data from triplicate wells and one representative of three experimental repeats. Error bars indicate standard errors of the means.