Retroviral Envelope Protein: A New Autoantigen Reactive with Non Obese Diabetic (NOD) Mice Sera

Abstract

IDDM (Insulin dependent diabetes mellitus) is believed to be an autoimmune disease and characterized by the immune activation against insulin-producing pancreatic beta cell. The identification and characterization of new autoantigens reactive with an activated immune System would heip to elucidate the pathogenic mechanism of this disease. Several autoantigens are trying to apply for diagnosis and prevention of IDDM. The NOD (non obese diabetic) mice have been the best model for studying the pathogenesis of human IDDM. To identify new autoantigens reactive with activated humoral immunity of NOD mice, the lambda gt11 cDNA library was constructed from NOD-derived pancreatic beta cell (MIN6N8a: mouse insulinoma cell) and screened with prediabetic NOD sera. Mine positive dones were selected from 2x10^(5) phage plaques. The 5'-end sequencing and homology searching showed that six clones from nine clones had over 98% sequence homolgy with the retroviral envelope gene. Full sequendng reveated that the cloned gene was a fragment of ecotropic retrovirus (emv-3) envelope gene. To confirm the immunoreactivity of doned retroviral envelope protein, the cloned gene fragment was expressed in an E.coli expression vector System. Western blotting showed that the recombinant envelope protein fragment also reacted with prediabetic NOD sera.