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Two Monoclonal Antibodies Distinguish between Human Recombinant Interferon‐α5s Produced by Escherichia coli and by Mouse Cells

Two monoclonal antibodies against human IFN‐α‐one against natural leukocyte IFN‐α and the other against recombinant human IFN‐α 2 produced in E. coli—were prepared, and designated as HT‐1, and 104‐5‐f, respectively. These monoclonal antibodies were used to examine the antigenicities of recombinant human IFN‐α5s produced by E. coli and by mouse cells. The HT‐1 antibody could bind and neutralize recombinant human IFN‐α5 synthesized in mouse cells, but not recombinant human IFN‐α5 synthesized in E. coli. On the other hand, the 104‐5‐f antibody could bind and neutralize recombinant human IFN‐α5 synthesized in E. coli but not recombinant human IFN‐α5 synthesized in mouse cells. Then these monoclonal antibodies or sheep polyclonal antibody against human IFN‐α were used to immunoprecipitate the radioactively labeled recombinant human IFN‐α5 synthesized either in E. coli or mouse cells, and analysed on polyacrylamide gel electrophoresis in the presence of NaDodSO4. The labeled recombinant human IFN‐α5 produced by mouse cells could be immunoprecipitated with the HT‐1 monoclonal antibody or sheep anti‐(human IFN‐α) polyclonal antibody but not with the 104‐5‐f monoclonal antibody and showed a band of Mr. 17,500 on polyacrylamide gel electrophoresis in the presence of NaDodSO4. On the other hand, the labeled recombinant human IFN‐α5 produced by E. coli could be immunoprecipitated with the 104‐5‐f monoclonal antibody but not with the HT‐1 monoclonal antibody and showed a band of similar Mr. on polyacrylamide gel electrophoresis. These results indicate that the two different preparations of recombinant human IFN‐α5, one produced by mouse cells and the other in E. coli, have different epitopes on their molecules which are supposed to have the same primary amino acid sequence. Although the reason why these different epitopes are expressed on the two molecules is unclear, the results agree with our previous observation that recombinant human IFN‐α5 produced by mouse cells but not by E. coli has a slight cross reactivity on mouse cells [Fukunaga, Sokawa, and Nagata, 1984. Proc. Natl. Acad. Sci. U.S.A. 81: 5086–5096]. And these results may suggest the different tertiary structure between recombinant human IFN‐α5 produced in E. coli and mammalian cells.