A family of genes coding for two serologically distinct chicken interferons.

Southern blot analysis and screening of a genomic lambda phage library with the previously cloned chicken interferon (IFN) cDNA indicated that the chicken genome contains at least 10 IFN genes. A particularly strongly hybridizing phage clone that we analyzed in more detail carried a head to tail arrangement of three intron-less IFN genes that differed from each other and from the cloned chicken IFN cDNA by only a few base changes. The primary translation products of these three IFN genes consist of 193 amino acids, and the mature proteins are composed of 162 amino acids. All three genes of this IFN family, designated IFN1, yielded active chicken IFN when expressed individually in transfected COS7 cells. A weakly hybridizing phage clone contained an additional intron-less chicken IFN gene, designated IFN2, whose product was 57% identical to chicken IFN1. Southern blot analysis suggested that the chicken genome contains a single IFN2 gene. The primary translation product of IFN2 consists of 203 amino acids, and the mature protein is composed of 176 amino acids. Purified recombinant chicken IFN2 from Escherichia coli had a specific antiviral activity of about 10(6) units/mg, which was about 20-fold lower than that of chicken IFN1 purified in parallel. The antiviral activity of chicken IFN2 from E. coli or from transfected COS7 cells could not be neutralized by antiserum to recombinant chicken IFN1. Thus, like mammals, the chicken has a large number of type I IFN genes that code for at least two serologically distinct antiviral activities.