Cerebrospinal fluid B-cell expansion in longitudinally extensive transverse myelitis associated with neuromyelitis optica immunoglobulin G

Role and Relevance of Cerebrospinal Fluid Cells in Diagnostics and Research: State-of-the-Art and Underutilized Opportunities

Cerebrospinal fluid (CSF) has recently experienced a revival in diagnostics and research. However, little progress has been made regarding CSF cell analysis. For almost a century, CSF cell count and cytomorphological examination have been central diagnostic parameters, with CSF pleocytosis as a hallmark finding of neuroinflammation and cytology offering valuable clues regarding infectious, autoimmune, and malignant aetiologies. A great deal of information, however, remains unattended as modern immune phenotyping technologies have not yet been broadly incorporated into routine CSF analysis. This is a serious deficit considering the central role of CSF cells as effectors in central nervous system (CNS) immune defence and autoimmune CNS processes, and the diagnostic challenges posed by clinically overlapping infectious and immune-mediated CNS diseases. Here, we summarize historical, specimen-intrinsic, methodological, and technical issues determining the state-of-the-art diagnostics of CSF cells and outline future perspectives for this underutilized window into meningeal and CNS immunity.

Cerebrospinal fluid CD20 positive B-cell expansion in a case of anti-NMDAR encephalitis

Anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis is a potentially fatal autoimmune encephalitis with a strong B-cell response. We measured the proportion of CD20 positive and CD19 positive B-cells in the CSF from a case of severe anti-NMDAR encephalitis. The proportion of CD20 positive B-cells in the CSF was 15.0%, higher than CD19 positive B cells (10.1%), and higher than that seen in non-inflammatory neurological disorders (<1%). After the treatments of steroids, intravenous immunoglobulin and rituximab to eliminate B-cells, she recovered. These findings further support the use of rituximab that targets CD20 positive B-cells in anti-NMDAR encephalitis.

Magnetic resonance imaging in enterovirus-71, myelin oligodendrocyte glycoprotein antibody, aquaporin-4 antibody, and multiple sclerosis-associated myelitis in children

AIM

We used magnetic resonance imaging (MRI) to compare the neuroimaging of children with their first episode of clinical enterovirus 71-associated transverse myelitis (EV71-TM), myelin oligodendrocyte glycoprotein antibody positive transverse myelitis (MOG-TM), aquaporin-4 antibody positive transverse myelitis (AQP4-TM), transverse myelitis in multiple sclerosis (MS-TM), and unclassified transverse myelitis (UNC-TM).

METHOD

We performed a retrospective blinded radiological assessment and compared the neuroimaging of 52 children (32 females, 20 males; mean age 9y 8mo, SD 5y 5mo, range 5mo-17y) presenting with their first episode of myelitis caused by EV71-TM (n=11), MOG-TM (n=10), AQP4-TM (n=9), MS-TM (n=13), and UNC-TM (n=9).

RESULTS

In the EV71-TM group, lesions were distributed throughout the cord and enhancement of nerve roots (ventral and dorsal) was common. The MOG-TM group had lesions distributed throughout the cord and most commonly longitudinally extensive transverse myelitis and lesions involving the grey matter alone on axial scans. The AQP4-TM group had lesions distributed in the cervicothoracic spine, cavitation, and contrast enhancing lesions. All patients with AQP4-TM had an abnormal brain MRI scan. The MS-TM group characteristically had multiple short segment lesions of the cord involving the cervicothoracic spine. The UNC-TM group did not have distinctive spinal MRI findings but had a relative paucity of lesions on their brain MRI scans.

INTERPRETATION

There are neuroimaging findings that are helpful in differentiating between myelitis associated with EV71, MOG, AQP4, and multiple sclerosis in children. These features may be useful early in the presentation of transverse myelitis while awaiting infectious/immunological testing, and/or further demyelinating events.

WHAT THIS PAPER ADDS

Magnetic resonance imaging can help identify aetiologies for children presenting with a first episode of myelitis. Entervirus-71-associated myelitis lesions are distributed throughout the cord and enhancement of nerve roots is common. Lesions distributed throughout the cord are commonly seen in myelin oligodendrocyte-associated myelitis. Aquaporin-4-associated myelitis lesions are distributed in the cervicothoracic spine, cavitation and contrast enhancing lesions are common. Short segment lesions in the cervicothoracic spine are commonly seen in multiple sclerosis-associated myelitis.

Promise, Progress, and Pitfalls in the Search for Central Nervous System Biomarkers in Neuroimmunological Diseases: A Role for Cerebrospinal Fluid Immunophenotyping

Biomarkers are central to the translational medicine strategic focus, though strict criteria need to be applied to their designation and utility. They are one of the most promising areas of medical research, but the "biomarker life-cycle" must be understood to avoid false-positive and false-negative results. Molecular biomarkers will revolutionize the treatment of neurological diseases, but the rate of progress depends on a bold, visionary stance by neurologists, as well as scientists, biotech and pharmaceutical industries, funding agencies, and regulators. One important tool in studying cell-specific biomarkers is multiparameter flow cytometry. Cerebrospinal fluid immunophenotyping, or immune phenotypic subsets, captures the biology of intrathecal inflammatory processes, and has the potential to guide personalized immunotherapeutic selection and monitor treatment efficacy. Though data exist for some disorders, they are surprisingly lacking in many others, identifying a serious deficit to be overcome. Flow cytometric immunophenotyping provides a valuable, available, and feasible "window" into both adaptive and innate components of neuroinflammation that is currently underutilized.

The pathology of an autoimmune astrocytopathy: lessons learned from neuromyelitis optica

Neuromyelitis optica (NMO) is a disabling autoimmune astrocytopathy characterized by typically severe and recurrent attacks of optic neuritis and longitudinally extensive myelitis. Until recently, NMO was considered an acute aggressive variant of multiple sclerosis (MS), despite the fact that early studies postulated that NMO and MS may be two distinct diseases with a common clinical picture. With the discovery of a highly specific serum autoantibody (NMO-IgG), Lennon and colleagues provided the first unequivocal evidence distinguishing NMO from MS and other central nervous system (CNS) inflammatory demyelinating disorders. The target antigen of NMO-IgG was confirmed to be aquaporin-4 (AQP4), the most abundant water channel protein in the CNS, mainly expressed on astrocytic foot processes at the blood-brain barrier, subpial and subependymal regions. Pathological studies demonstrated that astrocytes were selectively targeted in NMO as evidenced by the extensive loss of immunoreactivities for the astrocytic proteins, AQP4 and glial fibrillary acidic protein (GFAP), as well as perivascular deposition of immunoglobulins and activation of complement even within lesions with a relative preservation of myelin. In support of these pathological findings, GFAP levels in the cerebrospinal fluid (CSF) during acute NMO exacerbations were found to be remarkably elevated in contrast to MS where CSF-GFAP levels did not substantially differ from controls. Additionally, recent experimental studies showed that AQP4 antibody is pathogenic, resulting in selective astrocyte destruction and dysfunction in vitro, ex vivo and in vivo. These findings strongly suggest that NMO is an autoimmune astrocytopathy where damage to astrocytes exceeds both myelin and neuronal damage. This chapter will review recent neuropathological studies that have provided novel insights into the pathogenic mechanisms, cellular targets, as well as the spectrum of tissue damage in NMO.

Cerebrospinal fluid CD19(+) B-cell expansion in N-methyl-D-aspartate receptor encephalitis

There is increasing interest in the role of autoantibodies in acquired autoimmune central nervous system disorders. N-methyl-D-aspartate receptor (NMDAR) encephalitis is an autoimmune encephalitis defined by the presence of autoantibodies that bind to the NMDAR. Although there is evidence of NMDAR antibody pathogenicity, it is unclear which treatment results in the best outcome. We measured the proportion of B-cells in the cerebrospinal fluid of two children with NMDAR encephalitis (a 6-year-old male and a 4-year-old female), one in the acute phase and one in the relapsing phase. The proportion of CD19(+) B-cells in both children was greater than 10%, significantly higher than seen in non-inflammatory neurological disorders (<1%). This finding supports the use of drugs, such as rituximab, that deplete B-cells in severe or refractory cases of NMDAR encephalitis, and lends further support to the humoral autoimmune hypothesis in NMDAR encephalitis.

Aquaporin-4 autoantibody: a neurogenic cause of anorexia and weight loss

Neuromyelitis optica (NMO) is a severe inflammatory demyelinating disease often associated with a highly specific autoantibody, aquaporin-4 antibody. Although the classic syndrome involves the optic nerves and spinal cord, aquaporin-4 antibody has been important in defining the true spectrum of NMO, which now includes brain lesions in areas of high aquaporin-4 expression. Brainstem involvement, specifically area postrema involvement in the medulla, has been associated with intractable vomiting in some patients with NMO. We describe a 14-year-old female with positive aquaporin-4 antibody whose clinical course was dominated by severe anorexia with associated weight loss (from 68-41kg; body mass index 25.2-15.6). Magnetic resonance imaging showed lesions in the medulla, pons, and thalami. Although she had asymptomatic radiological longitudinally extensive transverse myelitis, she never had symptoms or signs referable to the spinal cord or the optic nerves. We propose that anorexia and weight loss should be considered part of the NMO spectrum, probably related to area postrema involvement.

Cerebrospinal fluid levels of CXCL13 are elevated in neuromyelitis optica

BACKGROUND

B cells are believed to play an important role in the pathogenesis of NMO. Chemokine (C-X-C motif) ligand 13 (CXCL13), the most potent B-cell chemoattractant, is a chemokine which is critical for secondary lymphoid tissue development and for B-cell migration. Concentration of CXCL13 in cerebral spinal fluid (CSF) is elevated in patients with multiple sclerosis (MS). However, whether levels of CSF CXCL13 are elevated in NMO patients still remain unknown.

OBJECTIVE

To measure the CSF concentration of CXCL13 in NMO patients, and to determine its relationship with NMO disease activity.

METHODS

CSF CXCL13 was measured by an enzyme-linked immunosorbent assay (ELISA) in NMO (n=22), MS (n=18) patients and controls (CTLs) (n=12).

RESULTS

CSF CXCL13 levels in NMO were notable higher than MS (p=0.015) and CTLs (p<0.001), and were related to the NMO disease activity indicated by relapse rate and Expanded Disability Status Scale (EDSS) scores. NMO Patients with the higher relapse rates exhibited the higher CXCL13 concentrations in their CSF; and a trend of increased disease disability with increased CSF CXCL13 level was revealed. The CSF CXCL13 concentrations seemed to associate with CSF white blood cell counting, total protein concentration in NMO subgroup, thought did not quite reach statistical significance (WBC, p=0.473; TP, p=0.276).

CONCLUSIONS

The concentration of CSF CXCL13 was elevated in NMO patients, and correlated with NMO activity.