Relative Antiviral Activity ofIn Vitro-Synthesized Murine Interferon-α4and -α1

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Abstract
Murine interferon-α4 (MuIFN-α4) is notable among the MuIFN-α subtypes because it lacks 5 amino acids corresponding to postitions 103–107 of the other subtypes, yet is the most highly expressed subtype.(1,2) Site-directed in vitro mutagenesis has been used to modify the genes coding for MuIFN-α4 and MuIFN-α1. The modifications have allowed (i) the in vitro expression of the mature form of each MuIFN-α subtype and (ii) the insertion of five amino acids, corresponding to amino acid positions 103–107 of MuIFN-α1, into the MuIFN-α4 sequence. In contrast to previously published data(1,3) MuIFN-α4 and MuIFN-α1, show only a twofold difference in antiviral activity, with MuIFN-α4 being the more active subtype. In keeping with this observation, it was also found that insertion of the five "missing" amino acids into MuIFN-α4 resulted in an analogue MuIFN-α with antiviral activity equivalent to MuIFN-α1. It may be inferred from this work that the deletion of amino acids 103–107 (QVGVQ) is solely responsible for the difference in antiviral activity between MuIFN-α4 and MuIFN-α1.