Table 1. Antiviral activity of N-terminally tagged IFN variants confirmed that fusion of a histidine–glycine tag to the N-terminus does not impact on IFN activity.

Sample	Specific activity calculated to NIBSC IFNα-2a [MIU per mg]
	IFN	Tag 1	Tag 2	Tag 3	Tag 4
		HHGGGG-IFN	HHHHGG-IFN	HGHGGG-IFN	HGHGHG-IFN
n	n = 3	n = 5	n = 5	n = 5	n = 5
MEAN	254.2	228.5	216.7	242.4	218.4
SEM	34.5	23.2	18.5	31.4	51.4