Fig. 1.

Determining the response of AK-D 2.2 cells to type I interferon and characterizing the replication kinetics and plaque formation of FIPV Black in AK-D 2.2 cells. A) AK-D (black) or AK-D 2.2 (green) cells were treated with increasing concentrations of feline interferon alpha (IFNα). After 6 h, total RNA was extracted and analyzed by qPCR for ISG54 and feline β-actin. ISG54 mRNA expression was normalized to β-actin then presented as average 2^−ΔCt values. B) Growth kinetics of FIPV Black (MOI = 0.1) determined by plaque assay of infected AK-D (black) and AK-D 2.2 (green) cell supernatants. Data representative of two to three independent experiments performed in triplicate and presented mean ± SD. Values were analyzed by unpaired t-tests. ***P < 0.001. C) Fcwf-4 CU cells were infected with MOI = 0.1 serotype I FIPV Black and supernatants were collected at 24 HPI after which plaque assay analysis was performed on AK-D, AK-D 2.2, or Fcwf-4 CU indicator cells. Images were taken at 48 (top) and 72 (bottom) HPI. Images are representative of three independent experiments.