Table 1.

IFN-β and IFN-γ inhibit CoV plaque formation

CoV	Treatment (U/ml)a	Mean no. plaquesb ± SEM	Fold-reductionc
Urbani	Vehicle	40.3 ± 5.9	–
	IFN-β (100)	14 ± 4.8*	3
	IFN-β (200)	15 ± 1.0*	2
	IFN-γ (100)	19.3 ± 5.8*	2
	IFN-γ (200)	11.5 ± 1.0*	3
	IFN-β (100)+ IFN-γ (100)	1.8 ± 0.5*	30
MHV-A59	Vehicle	60.3 ± 1.8	–
	IFN-β (100)	24.7 ± 1.1*	2
	IFN-β (200)	21.0 ± 0.7*	2
	IFN-γ (100)	32.0 ± 0.8*	2
	IFN-γ (200)	27.7 ± 1.1*	2
	IFN-β (100)+ IFN-γ (100)	9.7 ± 1.1*	6

^aVero E6 cells were treated with vehicle, hu IFN-β, hu IFN-γ or hu IFN-β and hu IFN-γ for 12 h before infection with approximately 40 PFU of SARS-CoV strain Urbani. L2 cells received identical treatments with murine IFNs and were infected with approximately 50 PFU of MHV-A59.

^bAverage number of plaques per well of a 10⁵ diluted stock determined 3–4 days post-infection (p.i.). Values represent (mean ± SEM) from three independent experiments.

^cFold-reduction in each group was calculated as 'plaques in vehicle/plaques in treatment.' Values represent mean from three independent experiments. Boldface type indicates a greater than 30-fold reduction in viral plaque formation.

^*P < 0.05, as determined by one-way ANOVA and Tukey's post hoc t test comparison of this treatment to vehicle.