Gregory P. Owens

Intrathecal pathogenic anti–aquaporin-4 antibodies in early neuromyelitis optica†

The serum of most neuromyelitis optica (NMO) patients contains autoantibodies (NMO‐IgGs) directed against the aquaporin‐4 (AQP4) water channel located on astrocyte foot processes in the perivessel and subpial areas of the brain. Our objectives were to determine the source of central nervous system (CNS) NMO‐IgGs and their role in disease pathogenesis.

Single-Cell Repertoire Analysis Demonstrates that Clonal Expansion Is a Prominent Feature of the B Cell Response in Multiple Sclerosis Cerebrospinal Fluid

Single-cell RT-PCR was used to sample CD19+ B cell repertoires in cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS) or viral meningitis. Analysis of amplified Ab H and L chain products served to identify the rearranged germline segment and J segment, and to determine the degree of homology for the H and L chain sequence of individual B cells. The B cell repertoire of viral meningitis CSF was predominately polyclonal, whereas B cell clonal expansion was a prominent feature of the IgG repertoire in three of four MS patients. Two dominant clonal populations in one MS CSF accounted for ∼70% of the IgG H chain V regions sequenced, while the corresponding IgM repertoires were more heterogeneous. One clonal B cell population revealed multiple L chain rearrangements, raising the possibility of a role for receptor editing in shaping the B cell response in some MS patients. The most immediate implications of identifying rearranged Ig sequences in MS B cells is the potential to accurately recreate recombinant Abs from these overrepresented H and L chains that can be used to discover the relevant Ag(s) in MS.

Proteomic analysis of multiple sclerosis cerebrospinal fluid

Two-dimensional gel electrophoresis and peptide mass fingerprinting were used to identify proteins in cerebrospinal fluid (C SF) pooled from three patients with multiple sclerosis (MS) and in C SF pooled from three patients with non-MS inflammatory central nervous system (C NS) disorders. Resolution of C SF proteins on three pH gradients (3-10, 4-7 and 6-11) enabled identification of a total of 430 spots in the MS C SF proteome that represented 61 distinct proteins. The gels containing MS C SF revealed 103 protein spots that were not seen on control gels. A ll but four of these 103 spots were proteins known to be present in normal human C SF. The four exceptio ns were: C RTAC -1B (cartilage acidic protein), tetranectin (a plasminogen-binding protein), SPARC -like protein (a calcium binding cell signalling glycoprotein), and autotaxin t (a phosphodiesterase). It remains unknown whether these four proteins are related to the cause and patho genesis of MS.

Antibodies Produced by Clonally Expanded Plasma Cells in Multiple Sclerosis Cerebrospinal Fluid

Intrathecal IgG synthesis, persistence of bands of oligoclonal IgG, and memory B‐cell clonal expansion are well‐characterized features of the humoral response in multiple sclerosis (MS). Nevertheless, the target antigen of this response remains enigmatic.

Programmed Cell Death in Developing Grafts of Fetal Substantia Nigra

Intracerebral transplants of ventral mesencephalic (VM) tissue have been well characterized. VM grafts contain numerous tyrosine hydroxylase immunoreactive neurons which send axons into the host brain. Transplanted neurons in VM grafts develop normally in that they contain tyrosine hydroxylase and GAP43. An overlooked aspect of graft development is cell death. It has been suggested that cell death in VM grafts was mostly necrotic. However, recent work in this laboratory suggested that developing grafts contain numerous apoptotic cells. In the present paper morphological, histochemical, and molecular correlates of apoptosis were used to assay cell death during VM graft development. At early times (5-15 days) after grafting VM grafts contained numerous apoptotic cells. In older grafts (21 and 28 days) few apoptotic cells were observed. In situ end labeling of fragmented DNA with biotinylated dUTP showed that early grafts contained numerous positive cells. The expression of RP8, a molecular correlate of apoptotic cell death, occurred in early grafts, but was not detectable in older grafts. These results indicate that apoptosis is a normal part of VM graft development. As in naturally developing neural systems, cell death in grafts may function to eliminate cells that fail to connect to appropriate targets.

Comparative Analysis of the CD19+ and CD138+ Cell Antibody Repertoires in the Cerebrospinal Fluid of Patients with Multiple Sclerosis

Increased amounts of intrathecally synthesized IgG and oligoclonal bands have long been recognized as a hallmark of multiple sclerosis (MS). B cells and plasma cells are components of the inflammatory infiltrates in both active and chronic MS lesions, and increased numbers of these cells are present in MS cerebrospinal fluid (CSF). Single-cell RT-PCR was used to analyze both the CD19+ B cell and CD138+ plasma cell populations in CSF of two patients with clinically definite MS and of one MS patient whose CSF was obtained after a clinically isolated syndrome, but before the second episode. Sequence analysis of amplified IgG V region sequences identified the rearranged germline segments, extent of somatic mutation, and clonal relationships within and between the two cell populations in the three MS patients. Expanded B cell and plasma cell clones were detected in each MS CSF and in all three patients the CD138+ IgG repertoire was more restricted. However, little if any significant sequence overlap was observed between the CD19+ and CD138+ repertoires of each donor. Detection of plasma cell clones by single-cell PCR will facilitate the in vitro production of recombinant Abs useful in identifying disease-relevant Ags.

The B cell response in multiple sclerosis.

Abstract Multiple sclerosis (MS) plaques and CSF contain increased amounts of intrathecally synthesized IgG, manifest as oligoclonal bands (OCBs) after protein electrophoresis. OCBs are not unique to MS and are also produced in infectious diseases of the CNS, in which the oligoclonal IgG has been shown to be antibody directed against the disease-causing agent. Thus, analysis of antibody specificity may identify the causative agent/antigen in MS. This review discusses recent studies that have analyzed the phenotypes of B cells in MS which infiltrate the CNS and the molecular features of their antigen-binding regions. Together with histologic studies showing the presence of ectopic lymphoid follicles in the meninges of some MS patients, this data supports the notion of a targeted and compartmentalized humoral response in MS.

The expression of GAP43 mRNA during the late embryonic and early postnatal development of the CNS of the rat: an in situ hybridization study

GAP43 is a developmentally regulated phosphoprotein which is almost exclusively found in neurons. Numerous correlative studies have shown that GAP43 is expressed at high levels during neurite extension, axonal elongation and synaptogenesis. In this study we used in situ hybridization to examine GAP43 expression during late embryonic and early postnatal development. The highest relative levels of GAP43 at all stages were present in the neocortex. Levels in this and other regions peaked between postnatal days 5 and 10. These results indicate that high levels of GAP43 mRNA correlate most highly with the latter stages of axon outgrowth and with the early stages of synapse formation.

Viruses and Multiple Sclerosis

Multiple sclerosis (MS) is a chronic demyelinating disorder of unknown etiology, possibly caused by a virus or virus-triggered immunopathology. The virus might reactivate after years of latency and lyse oligodendrocytes, as in progressive multifocal leukoencephalopathy, or initiate immunopathological demyelination, as in animals infected with Theilers murine encephalomyelitis virus or coronaviruses. The argument for a viral cause of MS is supported by epidemiological analyses and studies of MS in identical twins, indicating that disease is acquired. However, the most important evidence is the presence of bands of oligoclonal IgG (OCBs) in MS brain and CSF that persist throughout the lifetime of the patient. OCBs are found almost exclusively in infectious CNS disorders, and antigenic targets of OCBs represent the agent that causes disease. Here, the authors review past attempts to identify an infectious agent in MS brain cells and discuss the promise of using recombinant antibodies generated from clonally expanded plasma cells in brain and CSF to identify disease-relevant antigens. They show how this strategy has been used successfully to analyze antigen specificity in subacute sclerosing panencephalitis, a chronic encephalitis caused by measles virus, and in neuromyelitis optica, a chronic autoimmune demyelinating disease produced by antibodies directed against the aquaporin-4 water channel.

Neuromyelitis optica MOG-IgG causes reversible lesions in mouse brain

IntroductionAntibodies against myelin oligodendrocyte glycoprotein (MOG-IgG) are present in some neuromyelitis optica patients who lack antibodies against aquaporin-4 (AQP4-IgG). The effects of neuromyelitis optica MOG-IgG in the central nervous system have not been investigated in vivo. We microinjected MOG-IgG, obtained from patients with neuromyelitis optica, into mouse brains and compared the results with AQP4-IgG.ResultsMOG-IgG caused myelin changes and altered the expression of axonal proteins that are essential for action potential firing, but did not produce inflammation, axonal loss, neuronal or astrocyte death. These changes were independent of complement and recovered within two weeks. By contrast, AQP4-IgG produced complement-mediated myelin loss, neuronal and astrocyte death with limited recovery at two weeks.ConclusionsThese differences mirror the better outcomes for MOG-IgG compared with AQP4-IgG patients and raise the possibility that MOG-IgG contributes to pathology in some neuromyelitis optica patients.