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JDRF Funded Research

JDRF-Funded Research: Lay Abstract

Name: Philippe Mondon ,Ph.D.
Millegen SA, FRA
Lab Website:

Project duration: 01-SEP-2008 to 31-AUG-2010
Priority Research Grant

Project grant award: $500,000.00*

* Total Grant award amount may vary depending on budget adjustments and it is contingent upon research progress and availability of JDRF research funds.

File No: 1-2008-1024

(Abstract Dt: 07-MAY-2008)

Therapeutic Area: Beta Cell Therapies

Grant Status: Active

Project Title

Cloning and Engineering the IC2 Biomarker targeting functional beta cells

Objective

1.To secure the unique beta-cell surface specificity of IC2 a specific biomarker for functional beta-cell - through DNA cloning of the variable antibody region (Fv)2.To fragment the large native IgM autoantibody by making chimeric recombinant antibody (70% human) less immunogenic for later human clinical diagnostic use.3.To enable large scale production of this unique biomarker reagent through production of recombinant rIC2 antibody.4.To identify and characterize at molecular level the target epitope for this unique monoclonal autoantigen by epitope mapping, and eventual cloning of the target autoantigen for further use as target to measure serum autoantibodies with the same specificity in prediagnostic testing5.To better understand the autoimmunity in type-1 diabetes and discover new ways of prevention.

Background/Rationale

Because antibody fragments contain no Fc segment, they do not harbor natural Fc-effector functions and have the advantage to be functionally expressed in bacteria and yeast. Small monovalent antibody fragments (scFv) exhibit good tissue penetration but their lack of avidity results in faster off rates. However, the antibody domains can be further engineered through directed molecular evolution to produce antibody variants with higher affinity or enhanced stability to obtain optimal immune characteristics of the parental antibody. The easy available and large amount of recombinant antibodies produced in fusion with a reporter molecule will give us a better change to make preparative work, like affinity chromatographic purification of the autoantigen, full molecular characterization of the autoantigenic sulfatide-plasma protein complex epitope by structural NMR analysis.

Description of Project

Biomarkers are used in type-1 diabetes mainly as prediagnostic screening tool on serum samples looking for autoantibodies affiliated with onset of the disease or as biomarker for diabetes complications, e.g. nephropathy. However other types of biomarkers are more linked to the insulin production itself or as a direct marker for the beta-cell mass in vivo. Measurement of the beta-cell mass in vivo and its functional state demand biomarkers of very high specificity either to the beta-cell mass as such but preferably exclusively to the functional part of the beta-cells. Biomarkers are of great importance in the clinic to monitor still functional beta-cell mass in vivo during disease development, but also to monitor survival of transplanted beta-cell mass in vivo. A new area of beta-cell mass noninvasive imaging is linked to stem-cell research to followed stem cell differentiation into mature insulin-producing beta-cells and to measure impact of pharmaceutical drugs on beta-cell survival, proliferation and formation of new beta-cell from progenitor stem cells. The monoclonal autoantibody IC2 isolated from a prediabetic rat has proven to be the most specific biomarker for native beta-cells in vivo. It targets exclusively the beta-cell surface of insulin-producing cells, and it has already been applied in vivo labelled with radioactive tracers and shown an ability to give an estimated on both native and transplanted islet functional beta-cells. This unique autoantibody beta-cell specific biomarker will in the proposal be secured forever by recombinant DNA cloning, which at the same time will enable development of more penetrable and perhaps even stronger binding beta-cell probes, obtained by further protein engineering on the originally native autoantibody genes. The cloned version of recombinant IC2 will immediately be available for fusion with so-called reporter-genes as an optical imaging probe, but it also allow large scale production for delivery to the clinic as a new tool to make an easy estimation of the residual beta-cell mass by noninvasive medical imaging. Finally the unique biomarker might target a new still not fully identified and characterized autoantigens, but in this case completely specific to the beta-cell. Full characterization of the IC2 targeted autoantigen might therefore bring a new and better prediagnostic marker for type-1 diabetes, which even could be a new key to an better understand the autoimmune destruction of beta-cell in type-1 diabetes. Other projects linked to this cloning and further engineering of the IC2 specificity is 1) radioisotope medical imaging for estimation of residual beta-cell mass, and 2) development of a new prediagnostic screening methods for type-1 diabetes hopefully more specific to diabetes. With full knowledge about the targeted autoantigen, it sulfatide binding properties and the proposed role in the insulin-secretion cascade we might also have a key to better understand autoimmune diabetes.

Anticipated Outcome

1. Securing and optimizing the specificity of IC2 antibody to functional beta cells.2. Enabling large scale production of IC2 biomarker for medical imaging and purify beta cells for transplantation.3. Role of the targeted autoantigen in the insulin-secretion cascade and a key to a better understanding of autoimmune diabetes.

Relevance to Type I Diabetes

1. Monitoring of beta cell mass destruction and regeneration during development of diabetes type 1. 2. A dynamic new tool of cellular and molecular analysis of diabetes and study the influence of drugs on the functional stage of the beta cells.3. Discovery of a new autoantigen target specific to type 1 diabetes to develop an improve prediagnostic assay for serum autoantibody measurement.