Dan Frenkel

Immunology and immunotherapy of Alzheimer's disease.

Although Alzheimers disease is considered to be a degenerative brain disease, it is clear that the immune system has an important role in the disease process. As discussed in this Review, immune-based therapies that are designed to remove amyloid-β peptide from the brain have produced positive results in animal models of the disease and are being tested in humans with Alzheimers disease. Although immunotherapy holds great promise for the treatment of Alzheimers disease, clinical trials of active amyloid-β vaccination of patients with Alzheimers disease were discontinued after some patients developed meningoencephalitis. New immunotherapies using humoral and cell-based approaches are currently being investigated for the treatment and prevention of Alzheimers disease.

Oral CD3-specific antibody suppresses autoimmune encephalomyelitis by inducing CD4+ CD25- LAP+ T cells.

A major goal of immunotherapy for autoimmune diseases and transplantation is induction of regulatory T cells that mediate immunologic tolerance. The mucosal immune system is unique, as tolerance is preferentially induced after exposure to antigen, and induction of regulatory T cells is a primary mechanism of oral tolerance. Parenteral administration of CD3-specific monoclonal antibody is an approved therapy for transplantation in humans and is effective in autoimmune diabetes. We found that orally administered CD3-specific antibody is biologically active in the gut and suppresses autoimmune encephalomyelitis both before induction of disease and at the height of disease. Orally administered CD3-specific antibody induces CD4+CD25−LAP+ regulatory T cells that contain latency-associated peptide (LAP) on their surface and that function in vitro and in vivo through a TGF-β–dependent mechanism. These findings identify a new immunologic approach that is widely applicable for the treatment of human autoimmune conditions.

Nasal Vaccination with Myelin Oligodendrocyte Glycoprotein Reduces Stroke Size by Inducing IL-10-Producing CD4+ T Cells

Inflammation plays an important role in ischemic stroke and in humans IL-10 may have a beneficial effect in stroke. We mucosally administered myelin oligodendrocyte glycoprotein (MOG) 35–55 peptide to C57BL/6 mice before middle cerebral artery occlusion (MCAO) to induce an anti-inflammatory T cell response directed at CNS myelin. Nasal and oral administration of MOG35–55 peptide decreased ischemic infarct size at 24 and 72 h after MCAO surgery. Nasal MOG35–55 peptide was most efficacious and reduced infarct size by 70% at 24 h and by 50% at 72 h (p ≤ 0.0001 vs control) and also improved behavior score. Immunohistochemistry demonstrated increased IL-10 and reduced IFN-γ in the area surrounding the ischemic infarct following nasal treatment. Nasal MOG did not reduce infarct size in IL-10-deficient mice. Adoptive transfer of CD4+ T cells to untreated mice from nasally tolerized mice before MCAO surgery decreased stroke size (p < 0.001 vs control), whereas, CD4+ T cells from nasally tolerized IL-10-deficient mice had no effect. Our results demonstrate that IL-10-secreting CD4+ T cells induced by nasal MOG reduce injury following stroke. In addition, we observed a dramatic reduction of CD11b+ cells in nasal MOG-treated animals. CD11b+ cells may contribute to secondary infarct expansion by enhancing NO synthesis that may be reduced by elevated IL-10 levels. Modulation of cerebral inflammation by nasal vaccination with myelin Ags that increase IL-10 in the brain may improve outcome after stroke and enhance mechanisms of recovery.

Filamentous phage as vector-mediated antibody delivery to the brain

Early diagnosis of Alzheimers disease is prevented by lack of means to visualize and target β amyloid plaques in the brains of affected people. There are many methods of detecting amyloid plaques by staining postmortem brain tissue, but none are available for monitoring in living patients. We propose anti-β amyloid antibodies as a highly specific probe to monitor amyloid plaque formation in living patients. Intranasal administration of filamentous phage as delivery vector of anti-β amyloid antibody fragment into Alzheimers APP transgenic mice enables in vivo targeting of β amyloid plaques. The plaques were covisualized both by thioflavin-S and fluorescent-labeled antiphage antibodies in the olfactory bulb and the hippocampus region. The genetically engineered filamentous bacteriophage proved to be an efficient and nontoxic viral delivery vector to the brain, offering an obvious advantage over other mammalian vectors. The ability to image Aβ deposits in vivo would arguably provide the most useful diagnostic and monitoring test for early diagnosis of Alzheimers disease.

Neuroprotection by IL-10-producing MOG CD4+ T cells following ischemic stroke.

Mucosal tolerance has been used successfully to treat animal models of autoimmune diseases and is being tested in human diseases. In this work we demonstrate the reduction of infarct size following mucosal tolerance by myelin oligodendrocyte glycoprotein (MOG) (35-55) peptide in mouse stroke model. Nasal MOG was most efficacious and reduced ischemic infarct size by 70% at 24 h as well as improving behavior score. Using immunohistological methods and IL-10 -/- mice, we demonstrate the importance of IL-10-producing CD4+ T cells in the reduction of the ischemic infarct volume following middle cerebral artery occlusion (MCAO). Furthermore, adoptive transfer of CD4+ T cells from nasally tolerized mice to untreated mice prior to MCAO surgery significantly decreased stroke size (p<0.001 vs. control), whereas CD4+ T cells from nasally tolerized IL-10-deficient mice had no significant effect. Based on these results, modulation of cerebral inflammation by mucosal tolerance to myelin antigens may have applicability both as prophylactic therapy and treatment following ischemia attacks.

Inhibition of Autoimmune Diabetes by Oral Administration of Anti-CD3 Monoclonal Antibody

Anti-CD3 monoclonal antibody (mAb) has been shown to induce tolerance and to be an effective treatment for diabetes both in animal models and in human trials. We have shown that anti-CD3 mAb given orally is biologically active in the gut and suppresses experimental autoimmune encephalitis by the induction of a regulatory T-cell that expresses latency-associated peptide (LAP) on its surface. In the present study, we investigated the effect of oral anti-CD3 mAb on the prevention of autoimmune diabetes in AKR mice in which the low-dose streptozocin (STZ) model induces autoimmunity to the β-cells of the islets. We found that oral anti-CD3 mAb given at doses of 50 and 250 μg/feeding suppressed the incidence of diabetes in this model with the best effects seen at the 50 μg/dose. Associated with suppression, we observed decreased cell proliferation in the spleen and conversion of T-helper (Th)1 responses into Th2/Th3 responses in the periphery, including the pancreatic lymph nodes. Oral anti-CD3 mAb increased the expression of LAP on CD4+ T-cells, and these cells could adoptively transfer protection. Protection by oral anti-CD3 was transforming growth factor-β dependent. Our results demonstrate that oral anti-CD3 is effective in the model of STZ-induced diabetes and may be a useful form of therapy for type 1 diabetes in humans.

Generation of auto-antibodies towards Alzheimer's disease vaccination.

We developed a novel procedure to evoke anti-aggregating β-amyloid (Aβ) antibodies, using filamentous phages displaying only four amino acids EFRH of the β-amyloid peptide (AβP). This epitope was found to be the main regulatory site for fibril formation. For the first time, effective auto-antibodies have been obtained in guinea-pigs, which exhibit human identity in the AβP. Immunization through a phage-carrying epitope was found to be long-lasting, and no toxic effect caused by autoimmune response was detected in the challenged animal sections. These antibodies performed similarly to site-directed monoclonal antibodies and to antibodies raised against fibrillar Aβ in disaggregation of plaques, and may serve as the basis for developing an anti-Aβ vaccine.

A nasal proteosome adjuvant activates microglia and prevents amyloid deposition

We assessed whether peripheral activation of microglia by a nasal proteosome‐based adjuvant (Protollin) that has been given safely to humans can prevent amyloid deposition in young mice and affect amyloid deposition and memory function in old mice with a large amyloid load.

New immunosuppressive approaches: Oral administration of CD3-specific antibody to treat autoimmunity

One of the major goals for the immunotherapy of autoimmune diseases is the induction of regulatory T cells that mediate immunologic tolerance. Parenteral administration of anti-CD3 monoclonal antibody is an approved therapy for transplantation in humans and is effective in autoimmune diabetes. We have found that oral administration of anti-CD3 monoclonal antibody is biologically active in the gut and suppresses experimental autoimmune encephalomyelitis both prior to disease induction and at the height of disease. Oral anti-CD3 antibody acts by inducing a unique type of regulatory T cell characterized by latency-associated peptide (LAP) on its cell surface that functions in vivo and in vitro via TGF-beta dependent mechanism. Orally delivered antibody would not have side effects including cytokine release syndromes, thus oral anti-CD3 antibody is clinically applicable for chronic therapy. These findings identify a novel and powerful immunologic approach that is widely applicable for the treatment of human autoimmune conditions.

Nasal vaccination with troponin reduces troponin specific T-cell responses and improves heart function in myocardial ischemia–reperfusion injury

Myocardial ischemia with subsequent reperfusion (MI/R) can lead to significant myocardial damage. Ischemia initiates inflammation at the blood-microvascular endothelial cell interface and contributes significantly to both acute injury and repair of the damaged tissue. We have found that MI/R injury in mice is associated with a cellular immune response to troponin. Myocardial cells exclusively synthesize troponin and release the troponin into the bloodstream following injury. Mucosally administered proteins induce T cells that secrete anti-inflammatory cytokines such as IL-10 and transforming growth factor beta at the anatomical site where the protein localizes. We found that nasal administration of the three subunits of troponin (C, I and T isoforms), given prior to or 1 h following MI/R, decreased infarct size by 40% measured 24 h later. At 1.5 months following MI/R, there was a 50% reduction in infarct size and improvement in cardiac function as measured by echocardiography. Protection was associated with a reduction of cellular immunity to troponin. Immunohistochemistry demonstrated increased IL-10 and reduced IFN-gamma in the area surrounding the ischemic infarct following nasal troponin. Adoptive transfer of CD4+ T cells to mice from nasally troponin-treated mice 1 h after the MI/R decreased infarct size by 72%, whereas CD4+ T cells from IL-10-/- mice or nasally BSA-treated mice had no effect. Our results demonstrate that IL-10-secreting CD4+ T cells induced by nasal troponin reduce injury following MI/R. Modulation of cardiac inflammation by nasal troponin provides a novel treatment to decrease myocardial damage and enhance recovery after myocardial ischemia.