Antibody responses following change-over to mixed species (porcine/bovine) insulins

Summary  TWENTY-SEVEN insulin requiring diabetics, who had been treated with conventional non-purified insulins for at least four years, were transferred to a regimen of highly purified mixed species (porcine/bovine) insulin. They were seen at 3-monthly intervals for two years during which the binding of labelled porcine and bovine insulins by serum was monitored, as was insulin dose, glycosylated haemoglobin and mean fasting blood glucose. Insulin binding by antibody fell from a mean (±ISD) of 13.3±13.7% (bovine) and 8.1±8.4% (porcine) at the beginning of the study to 6.8±8.0% (bovine) and 2.3±1.9% (porcine) 2 years after the change to mixed species insulin. This change reached statistical significance 60 weeks after the transfer. In contrast, antibodies to the insulin contaminant pancreatic polypeptide were significantly reduced 4 weeks after transfer to the mixed species insulins. They fell from 64 (±27)% at week 0 to 14.8 (±7.2)% at week 108. This study indicates the relatively high immunogenicity of highly purified mixtures of beef and pork insulins. In addition, the faster reduction of antibodies to pancreatic polypeptide suggests that this immunogenic impurity has been removed from the highly purified preparations and that the continuing insulin antibody production was caused by the intrinsic immunogenicity of the insulin; it is likely that bovine insulin possesses more immunogenic determinants than porcine insulin.