Chimeric proteins for diagnosis and treatment of diabetes

Abstract

Novel chimeric fusion proteins comprising immunodominant epitopes of GAD and insulin are provided. Also provided are immunomodulatory methods for the use of such proteins for both the prevention and treatment of Type 1 diabetes mellitus. The chimeric fusion proteins of the invention are useful in predicting risk of onset of Type I diabetes, determining prognosis of Type 1 diabetes patients early in disease progression, and in evaluating patients for suitability as recipients of transplants of pancreatic cells or tissues. The administration of the proteins of the invention in accordance with the immunomodulatory methods of the invention results in beneficial effects on disease development and severity in patients suffering from or predicted to be at risk of developing Type 1 diabetes, as well as on the outcome of transplants of pancreatic cells or tissues in Type I diabetes patients.

Description

CROSS REFERENCE TO RELATED APPLICATION [0001] This application claims priority from U.S. provisional application Ser. No. 60 / 068,648, filed Dec. 23, 1997, which is incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] The discussion in this section is not limited to subject matter that qualifies as “prior art” against the present invention. Therefore, no admission of such prior art status shall be implied or inferred by reason of inclusion of particular subject matter in this discussion, and no declaration against the present inventors' interests shall be implied by reason of such inclusion. [0003] Diabetes Mellitus [0004] Diabetes mellitus is the most common endocrine disease, and is characterized by abnormalities of glucose metabolism. The abnormal glucose metabolism associated with this disease results in hyperglycemia (high blood glucose levels) and eventually causes complications of multiple organ systems, including eyes, kidneys, nerves, and blood vessels. Patien...

AI Technical Summary

Benefits of technology

[0064] In view of the foregoing, the objects of this invention include the provision of novel chimeric fusion proteins that act as single molecular entities that 1) facilitate diagnosis and prognostic evaluation of individuals suspected of predispostion for the development of IDDM, as well as those suffering from IDDM and / or Stiff-Man syndrome, and 2) to provide enhanced beneficial effects when administered to animals (including human patients) suffering from or at risk of developing autoimmune (Type 1) diabetes. To these ends the invention provides chimeric fusion proteins comprising epitopes of both GAD (glutamate decarboxylase) and insulin. Preferably the GAD is GAD 65 and the GAD and insulin are human GAD and insulin.

[0066] In accordance with the invention, (and as set forth in the examples, below) the combination of GAD 65 and insulin chains and / or peptides in a single chimeric fusion protein further provides a compound which can be administered so as to furnish more effective immunomodulatory therapeutic treatment than the combination of the same peptides and / or insulin chains as discrete individual peptide moieties and insulin chains. More specifically, preferred chimeric fusion proteins of the invention, when tested in an assay in a mouse model of IDDM, provide a greater reduction in the frequency of onset of diabetes than a control mixture containing equimolar amounts of each of the various discrete individual peptide moieties and insulin chains comprised by the chimeric fusion protein, each of said individual peptide moieties and insulin chains not being covalently bound to any other of said individual peptide moieties and insulin chains in said mixture, wherein the assay is carried out by the repeated parenteral administration of a number of measured doses, each dose being of a predetermined molar quantity of said chimeric fusion protein in a pharmaceutically effective carrier or of said control mixture in the pharmaceutically effective carrier, the administration being at intervals of not less than twelve hours and not more than 72 hours between each of the doses.

[0069] The chimeric fusion proteins of the invention each combine in a single molecular entity the key (immunodominant) autoantigenic epitopes of both insulin and GAD 65. In so doing, they provide single component diagnostic and therapeutic compounds. The chimeric fusion proteins of the invention provide enhanced beneficial effects after administration to animals (including human patients) when compared to the administration of combinations of the individual peptides representing the same immunodominant epitopes as are comprised within the chimeric fusion proteins.

[0078] To achieve these and other objects, the invention provides methods of treating a patient in need of such treatment, e.g., a patient selected from the group of patients consisting of patients at risk of developing type 1 diabetes and patients suffering from type 1 diabetes, so as to delay the onset or reduce the symptoms of diabetes in the patient and / or to ameliorate the autoimmune destruction of pancreatic beta cells in treated patients. Such treatment is particularly advantageous, and is preferably carried out, during the “honeymoon period” early in disease progression, before all of the patient's beta cells have been destroyed by the disease, or later in disease progression, when a patient is a candidate for transplantation of islet cells or tissues containing such cells.

Problems solved by technology

The abnormal glucose metabolism associated with this disease results in hyperglycemia (high blood glucose levels) and eventually causes complications of multiple organ systems, including eyes, kidneys, nerves, and blood vessels.

This dysfunction may lead to destruction of the islet beta cells, which produce insulin, a glucose regulatory peptide hormone.

In pre-IDDM, however, the destruction (if any) has not progressed to an extent sufficient to require the administration of insulin.

In addition to the acute metabolic complication of ketoacidosis, the diabetic patient is susceptible to a series of late complications that cause considerable morbidity and premature mortality.

Initial signs include increasing proteinuria, with azotemia ultimately leading to renal failure.

Diabetic foot ulcers represent a special problem of diabetics, and appear to be due primarily to abnormal pressure distribution secondary to diabetic neuropathy.

The relative importance of these various autoantigens to autoimmune pathogenesis, and the timing with which each plays a role during the course of disease onset and development, are the subject of considerable uncertainty and consequent controversy in the art.

Further uncertainty stems from the fact that each supposed autoantigen comprises numerous epitopes, some of which may be have disease promoting effects while others may have disease suppressive effects.

While diabetes has been studied for centuries, only a few effective treatments are available for type 1 disease.

One problem with this approach is that intensive insulin therapy requires a high level of patient awareness and compliance, as well as a highly skilled care team of physicians, nurses, and dietitians.

The goals of intensive insulin therapy are thus extremely difficult to achieve, even with motivated and educated patients.

Another problem is that a higher rate of hypoglycemia is seen in such rigorously treated patients than in patients receiving standard, less rigorous, insulin regimens.

The Diabetes Control and Complication Trial highlighted not only the benefit to overall metabolic health of maintaining normal blood glucose levels, but also a fundamental problem associated with the treatment of Type 1 diabetes, namely that the overt symptoms of the disease are manifested only when essentially all of the patients' islets are destroyed.

Oral agents for diabetes, such as the sulfonylureas, act primarily by stimulating the release of insulin from dysfunctional beta cells, and thus are not useful for most patients with type 1 disease, i.e. for those patients with IDDM.

These “effector” functions are the cause of tissue damage in autoimmune and other diseases.

Unfortunately, the duration of the therapeutic benefit of such transplants is currently limited by the same autoimmune phenomena that cause type 1 disease in the first place.

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