Objective
Development of immunotherapies that protect at risk individuals and maintain residual beta cells in newly diagnosed T1D patients is a scientific high priority and public interest. Assessing whether an agent can potentially fulfill this goal requires initial analysis animal models. The NOD mouse model in particular has prove critical for this purpose and it was used to first uncover therapeutic potential of anti-CD3 antibody, leading eventually to FDA approval of teplizumAb. The goal of this innovative proposal is to assess immunotherapeutic potential of a self-reactive natural IgM monoclonal antibody (called x-mAb). We do so by examining the ability of the x-mAb to induce remission in overtly diabetic NOD mice, examine underlying mechanisms and relevance to human disease using peripheral T cells from T1D patients. If the x-mAb proved to be equal or better than anti-CD3 in inducing remission, the results will be novel and would represent critical advancement towards developing safe immunotherapies that specifically target autoreactive T cells using x-mAb. Importance of such findings will be buoyed by the fact that the x-mAb is a human antibody and our published and new data show that it captures and interacts with insulin reactive CD4 T cells laying the foundation for additional preclinical studies and eventually testing in clinical trials.
Background Rationale
T1D is a chronic autoimmune disease caused by autoreactive lymphocytes that infiltrate and destroy insulin-producing beta cells, leading to hyperglycemia that needs to be actively controlled using exogenous insulin. Whereas insulin replacement is essential for patient survival, it does not totally prevent serious long-term neurologic and cardiologic complications. Furthermore, disease management significantly affects quality of life and public health care costs are extremely given that T1D strikes early in life. Thus, there is an urgent need for safe immunotherapies that prevent or delay disease progression and reduce insulin dependency. The FDA approval of the anti-CD3 antibody Tzield (teplizumab) as the first immunotherapeutic to delay onset of T1D was a breakthrough that sets the stage for new therapeutics that bypass serious side effects of teplizumAb, including transient deletion of T cells and immunosuppression. Therapeutic efficacy of teplizumab was first discovered by the ability of145-2C11 mouse anti-CD3 antibody to induce remission in diabetic NOD mice. The ability of mouse anti-CD3 to reverse hyperglycemia is unique among hundreds of modalities that have been examined, suggesting a correlation between the ability to induce remission in diabetic NOD mice and the ability to modulate T1D onset in patients. Our preliminary data show that the x-mAb can induce remission in diabetic NOD mice and suggest that x-mAb targets and tolerizes autoreactive T cells without impacting the immune system. If x-mAb proves to be efficacious in inducing remission in NOD mice and tolerizing autoreactive T cells of T1D patients, the results will provide rationale for assessing its efficacy in at risk individuals.
Description of Project
X-mAb is an unusual self-reactive antibody of the IgM isotype that is produced by a novel lymphocyte called “Dual Expressor (DE)” because it coexpresses both the TCR and BCR (surface antibody), the two antigen receptors that are normally expressed exclusively by T cells and B cells, respectively. DEs are present in healthy individuals, but in T1D patients they predominantly express the x-mAb. We have cloned, sequenced, and recombinantly expressed the light and heavy chains of the x-mAb as described in recent Cell and PNAS papers. We have generated a lymphoblastoid cell line from a DE isolated from a T1D patient that serves as a cellular source of soluble x-mAb. Functionally, the x-mAb is self-reactive as it induce proliferation of a subset of T cells and recognzies insulin-reactive T cells from various patients as determined by flow cytometry. We hypothesize that x-mAb can be used to capture and tolerize autoreactive T cells, leading to disease specific tolerance if injected in a tolerogenic form and absence of adjuvants. To test this hypothesis, we are using the NOD mouse, the best animal model for evaluating novel T1D therapeutics and the model where therapeutic efficacy of anti-CD3 (teplizumab) has first been demonstrated. Our preliminary results show that when diabetic NOD mice were treated with five consecutive injections of x-mAb in non-inflammatory phosphate buffered saline (PBS), blood sugar levels returned to normal level in the majority of mice for up to 100 days. At the cellular level, T cells recognized by x-mAb produced large amounts of the anti-inflammatory cytokine IL-10 and less proinflammatory TNFα and INF cytokines as compared to non-responders. We propose to build on these preliminary data and fully assess the therapeutic efficacy of x-mAb as compared to anti-CD3 and assess relevance to humans using PBMCs from T1D patients.
Anticipated Outcome
We anticipate to show that treatment of diabetic mice with x-mAb induces remission with a rate similar or better than that of anti-CD3 with less production of proinflammatory cytokines or global depletion of T cells.
Relevance to T1D
This study will uses the non-obese diabetic (NOD) mice, the widely used model of T1D to assess new biologics. Demonstrating that the x-mAb can iduce remission of autoimmune diabetes in NOD mice will be directly relevant to type 1 diabetes and the ultimate goal of develop specific immunotherapies that safely prevent or delay onset of diabetes.