Objective—To evaluate the effects of recombinant human interferon α-2b (rHuIFN-α2b) and recombinant feline interferon ω (rFeIFN-ω) on in vitro replication of feline herpesvirus (FHV)-1.
Sample Population—Cultures of Crandell-Rees feline kidney (CRFK) cells.
Procedures—CRFK cells were treated with rFeIFN-ω or rHuIFN-α2b at concentrations ranging from 100 to 500,000 U/mL. Cultures were then inoculated with FHV-1. Constant concentrations of interferon products were maintained throughout the study. Reductions in the number and size of plaques were used as indicators of antiviral activity. Six plaque reduction assays were performed in duplicate. A 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide assay was used to detect cytotoxic effects of interferon. A 1-way ANOVA and Dunnett test were used to determine significant differences.
Results—Treatment with rFeIFN-ω at various concentrations resulted in significant reductions in the number of plaques (100,000 U/mL, 54.7%; and 500,000 U/mL, 59.8%) and in plaque size (100,000 U/mL, 47.5%; 250,000 U/mL, 81.0%; and 500,000 U/mL; 70.5%). Treatment with various concentrations of rHuIFN-α2b resulted in a significant reduction in plaque size (100,000 U/mL, 56.0%; 250,000 U/mL, 75.7%; and 500,000 U/mL, 69.0%). None of the tested concentrations of interferon caused significant cellular toxicosis.
Conclusions and Clinical Relevance—At some of the higher concentrations, the antiviral effect of rFeIFN-ω was greater than the antiviral effect of rHuIFN-α2b. Reduction in plaque size appeared to be a good indicator of the antiviral activity of interferon against FHV-1.