Research interests: Movement disorders, neuroimmunology, paraneoplastic syndromes.
About 10 years ago, I focused on one pediatric myoclonic disorder caused by neuroblastoma, a paraneoplastic syndrome. I developed the National Pediatric Myoclonus Center (www.omsusa.org), a comprehensive and now international center with two programs, one clinical, the other basic. We have evaluated and created a database on 180 children, which is the largest experience with this rare disorder in the world. The clinical research program is designed to provide compassionate care, state-of-the-art diagnostic testing, the most promising of new investigational drug treatments for myoclonus, and to obtain body fluid samples for laboratory research. It avails itself of the research techniques of many outside collaborators. We developed and advocate immunologic staging, an individualized approach, much as oncologists would do tumor staging, to identify high-risk children and to ensure that no one is under-treated or over-treated. Based on our data, we are also proponents of multi-modality immunotherapy for opsoclonus-myoclonus and have pioneered this approach.
The basic research program entails studies of the neuroimmunology of paraneoplastic disorders. The goal is to define the immunologic defect in the opsoclonus-myoclonus syndrome. In studies of CSF and sera from OMS patients, we immunophenotype by flow cytometry using monoclonal antibodies; measure cytokine/chemokine activity in CSF; culture B cells and T cells and measure lymphocyte responses in vitro, such as antibodies and lymphokines produced in response to various antigen-specific stimuli such as brain and tumor antigens. For neuroanatomic localization, we test for immunostaining of brainstem and cerebellum by CSF, sera, and conditioned media from lymphocyte cultures, using double immunofluorescence labelling and immunoenzymatic assays. To define the neuropharmacologic target of autoantibodies, we screen CSF and sera and B cell culture conditioned media using gel electrophoresis and Western blots of pediatric control brain for testing the existence of autoantibodies against several neurotransmitter system enzymes and receptors known to have a role in myoclonus, such as GABA, glutamate, and serotonin. The relationship of immunologic and molecular pharmacologic abnormalities to clinical variables is evaluated statistically, focusing on treatment status and clinical severity as main variables. We have also developed an in vitro model system for studies of cytotoxicity in opsoclonus-myoclonus, which is being used to study brain-immune interactions. The effect parameters include cell differentiation, dendritic proliferation, and cell death by apoptosis.
My research has lead to the discovery of immunological biomarkers of disease activity in pediatric opsoclonus-myoclonus syndrome. Finding expansion of B- and T-cells in CSF that correlates highly with disease severity, we developed a treatment innovation, namely the use of a selective anti-B-cell monoclonal antibody (rituximab). We demonstrated that rituximab normalizes the CSF B-cell immunophenotype with resulting clinical improvement. We now have a phase I clinical trial that we anticipate will lead to a phase II trial in the near future. Our cytokine program has identified cytokine/chemokine biomarkers of relapse. We are now studying the effect of conventional and investigational immunotherapies on the biomarkers, with the goal of applying or developing novel cytokine/chemokine blockers. Short-term cultures of lymphocyte subsets will be used in functional assays and mechanistic studies.
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