PRELIMINARY STUDIES ON THE IMMUNOGENICITY AND AMOUNT OF ESCHERICHIA COLI POLYPEPTIDES IN BIOSYNTHETIC HUMAN INSULIN PRODUCED BY RECOMBINANT DNA TECHNOLOGY

Abstract

To find out whether biosynthetic human insulin produced from Escherichia colicontained bacterial polypeptides and whether these were immunogenic, polypeptides obtained from E. coli containing a plasmid similar to the one used to produce A and B chains but lacking the genes for these chains were used to measure the degree of human serum binding to iodinated peptides, to study immunogenicity in guineapigs, and to develop a sensitive immunoradiometric assay for E. coli polypeptides. Several biosynthetic human insulin preparations were tested by the use of this assay. Sera from 20 new diabetic patients receiving either biosynthetic human insulin or purified porcine insulin were tested for anti- E. coli polypeptide antibodies. 2, 4, and 6 month antibody levels in patients receiving biosynthetic human insulin did not differ significantly from pretreatment levels or from levels in those receiving porcine insulin. E. coli polypeptides were essentially non-immunogenic in guineapigs or rabbits unless emulsified with complete Freund's adjuvant. Biosynthetic human insulin did not produce anaphylaxis or delayed skin and Arthus reactions in guineapigs immunised with E. colipolypeptides emulsified in incomplete or complete Freund's adjuvant. The immunoradiometric assay for measuring E. coli polypeptides in biosynthetic human insulin preparations showed an absence of E. coli polypeptides capable of stimulating an immunogenic reaction.