Fig. 2.

Bovine respiratory coronavirus (BCoV) infection enhances the adherence of Pasteurella multocida (PM) to bovine respiratory epithelial cells (BRECs).

(A) BRECs preinfected with 5000 TCID₅₀ of BCoV for 1, 2, and 3 days were exposed to PM (MOI = 100) for 1 h. The number of PM adhering to BRECs was counted on Brucella agar. Data are expressed as the mean (±SEM; n = 3; *p < 0.05 compared to uninfected cells). (B) FITC-labeled PM (green) adherence to BCoV-infected and -uninfected BRECs at 3 dpi was observed with a fluorescence microscope; nuclei were stained with Hoechst-33342 (blue) (scale bar: 30 μm). (C) Expression of bovine IL-1β, IL-6, and TNF-α mRNA in BRECs infected with BCoV alone at 3 dpi, PM alone at 1 hpi, or BCoV 3 dpi plus PM 1 hpi. Data represent the mean of relative mRNA expression between the virus and/or bacteria infected samples and uninfected controls (±SEM; n = 3; * p < 0.05 compared to PM alone).