1491-P: Examination of the Humanized Antibody to SerpinB13 in Autoimmune Diabetes

Studies in our laboratory suggest that a combinatorial approach with a monoclonal antibody (mAb) to serpinB13, a cathepsin L (catL) inhibitor, and a suboptimal dose of antibody to CD3, is therapeutically superior to single antibody use, when these reagents are delivered into NOD mice during the late prediabetes period. The purpose of this study was to examine whether our newly generated humanized antibody to serpinB13 (hB29) has a similar effect. Ten-week old NOD female mice were each injected with 40 micrograms of hB29 and a suboptimal dose (10 micrograms) of CD3 mAb (clone 145-2C11). Control treatments included injections with non-specific human and hamster IgG. Random blood glucose levels were assessed for eight weeks after the last antibody injection, and mice were declared diabetic following two measurements of glucose exceeding 300 mg/dL. Alternatively, eight-week old NOD females were injected with the above-mentioned doses of antibodies and sacrificed 10 days later for histological analysis of pancreatic beta-cell mass. Visiopharm software was used for the quantitative analysis of microscopic images. We found that the combination of hB29 with CD3 mAb offered a significant level of protection from diabetes, while single antibody use had no effect. This was independently confirmed by microscopic analysis, which revealed increased residual beta-cell mass in the group receiving both hB29 and CD3 mAb, compared with the group receiving nonspecific human IgG. Our data demonstrate a strong similarity between the original mouse serpinB13 mAb and our new agent, the humanized antibody, hB29. Moreover, our finding of improved preservation of beta-cell mass within a short period of time following exposure to hB29 and CD3 mAb, is consistent with our previous observations that the serpinB13 mAb-mediated rescue of catL activity is responsible for impairing leukocyte function, and for slowing the progression of pancreatic islet damage.