Cloning, expression and biological activity of a new variant of human interferon alpha identified in virus induced lymphoblastoid cells

A synthetic oligonucleotide complementary to a highly conserved sequence in the IFN-alpha gene family, was used to screen a Namalva cDNA library. Among the cDNA clones having typical IFN-alpha traits, one was distinct from previously characterized IFN-alpha cDNAs. E. coli cells carrying this recombinant cDNA plasmid express an alpha-interferon activity. The sequence of this IFN-cDNA is extremely homologous (99.5%) to that of the IFN-alpha J gene and is designated IFN-alpha J1. Several E. coli trp expression plasmids were constructed for efficient transcription and translation of the mature IFN-alpha J1. The maximal level of expression (5 X 10(3) molecules/cells) was obtained from plasmid pJ1-4. A synthetic consensus translation initiation sequence coupled to the trp p/o region (in pJ1-5) proved to be 10 times less effective in promoting metIFN production in bacteria, than the in-vitro mutated trpL initiation sequence carried on pJ1-4. The bacterial IFN-alpha J1 was purified (to over 90% purity) to a specific activity of 1.3 X 10(8) units/mg. The antiviral activity of the purified IFN-alpha J1 was compared with other highly purified IFN-alpha species (bacterial IFN alpha A and alpha C, leukocyte IFN-alpha 1, leukocyte IFN mixture and Namalva IFN preparation) on a large panel of mammalian cell cultures. IFN-alpha J1 exhibits a distinct antiviral activity.