Safety of COVID-19 vaccines in multiple sclerosis: A systematic review and meta-analysis.

BACKGROUND: Data are sparse regarding the safety of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines in patients with multiple sclerosis (MS). OBJECTIVE: To estimate (1) the pooled proportion of MS patients experiencing relapse among vaccine recipients; (2) the rate of transient neurological worsening, adverse events, and serious adverse events; (3) the previous outcomes of interest for different SARS-CoV-2 vaccine types. METHODS: Systematic review and meta-analysis of pharmacovigilance registries and observational studies. RESULTS: Nineteen observational studies comprising 14,755 MS patients who received 23,088 doses of COVID-19 vaccines were included. Mean age was 43.3 years (95% confidence interval (CI): 40-46.6); relapsing-remitting, secondary-progressive, primary-progressive MS and clinically isolated syndrome were diagnosed in 82.6% (95% CI: 73.9-89.8), 12.6% (95% CI: 6.3-20.8), 6.7% (95% CI: 4.2-9.9), and 2.9% (95% CI: 1-5.9) of cases, respectively. The pooled proportion of MS patients experiencing relapse at a mean time interval of 20 days (95% CI: 12-28.2) from vaccination was 1.9% (95% CI: 1.3%-2.6%; I2 = 78%), with the relapse risk being independent of the type of administered SARS-CoV-2-vaccine (p for subgroup differences = 0.7 for messenger RNA (mRNA), inactivated virus, and adenovector-based vaccines). After vaccination, transient neurological worsening was observed in 4.8% (95% CI: 2.3%-8.1%) of patients. Adverse events and serious adverse events were reported in 52.8% (95% CI: 46.7%-58.8%) and 0.1% (95% CI: 0%-0.2%) of vaccinations, respectively. CONCLUSION: COVID-19 vaccination does not appear to increase the risk of relapse and serious adverse events in MS. Weighted against the risks of SARS-CoV-2-related complications and MS exacerbations, these safety data provide compelling pro-vaccination arguments for MS patients.

Autoimmunity to neuronal nicotinic acetylcholine receptors.

Nicotinic acetylcholine receptors (nAChRs) are widely expressed in many and diverse cell types, participating in various functions of cells, tissues and systems. In this review, we focus on the autoimmunity against neuronal nAChRs, the specific autoantibodies and their mechanisms of pathological action in selected autoimmune diseases. We summarize the current relevant knowledge from human diseases as well as from experimental models of autoimmune neurological disorders related to antibodies against neuronal nAChR subunits. Despite the well-studied high immunogenicity of the muscle nAChRs where autoantibodies are the main pathogen of myasthenia gravis, autoimmunity to neuronal nAChRs seems infrequent, except for the autoantibodies to the ganglionic receptor, the α3 subunit containing nAChR (α3-nAChR), which are detected and are likely pathogenic in Autoimmune Autonomic Ganglionopathy (AAG). We describe the detection, presence and function of these antibodies and especially the recent development of a cell-based assay (CBA) which, contrary to until recently available assays, is highly specific for AAG. Rare reports of autoantibodies to the other neuronal nAChR subtypes include a few cases of antibodies to α7 and/or α4ß2 nAChRs in Rasmussen encephalitis, schizophrenia, autoimmune meningoencephalomyelitis, and in some myasthenia gravis patients with concurrent CNS symptoms. Neuronal-type nAChRs are also present in several non-excitable tissues, however the presence and possible role of antibodies against them needs further verification. It is likely that the future development of more sensitive and disease-specific assays would reveal that neuronal nAChR autoantibodies are much more frequent and may explain the mechanisms of some seronegative autoimmune diseases.

Sexual dysfunction therapeutic approaches in patients with multiple sclerosis: a systematic review.

OBJECTIVE: Multiple sclerosis (MS) is the most common chronic inflammatory demyelinating disease of the central nervous system (CNS). The most common clinical manifestations of MS are spasticity, pain, vesico-urethral disorders, cognitive impairments, chronic fatigue and sexual dysfunction. This review aims to explore the possible therapeutic options for managing sexual dysfunction in people with MS (PwMS). METHOD: A thorough search of the PubMed Medline database was performed. Records were limited to clinical studies published between 01/01/2010 up to 01/01/2022. The results were screened by the authors in pairs. RESULTS: The search identified 36 records. After screening, 9 records met the inclusion-exclusion criteria and were assessed. The pharmacological approaches investigated the effectiveness of sildenafil, tadalafil and onabotulinumtoxinA. Of the interventional studies the non-pharmacological investigated, the effectiveness of aquatic exercises, the application of pelvic floor exercises,the combination of pelvic floor exercises and mindfulness technique, the combination of pelvic floor exercises and electro muscular stimulation with electromyograph biofeedback, the application of yoga techniques and the efficacy of assistive devices like the clitoral vacuum suction device and the vibration device. CONCLUSION: The management of sexual dysfunction in PwMS needs to be further investigated. A team of healthcare professionals should be involved in the management of SD in order to address not only the primary (MS-related) SD symptoms but the secondary and tertiary as well. The main limitations that were identified in the existing literature were related to MS disease features, sample characteristics and evaluation tools and batteries.

Myasthenia gravis genome-wide association study implicates AGRN as a risk locus.

BACKGROUND: Myasthenia gravis (MG) is a rare autoimmune disorder affecting the neuromuscular junction (NMJ). Here, we investigate the genetic architecture of MG via a genome-wide association study (GWAS) of the largest MG data set analysed to date. METHODS: We performed GWAS meta-analysis integrating three different data sets (total of 1401 cases and 3508 controls). We carried out human leucocyte antigen (HLA) fine-mapping, gene-based and tissue enrichment analyses and investigated genetic correlation with 13 other autoimmune disorders as well as pleiotropy across MG and correlated disorders. RESULTS: We confirmed the previously reported MG association with TNFRSF11A (rs4369774; p=1.09×10-13, OR=1.4). Furthermore, gene-based analysis revealed AGRN as a novel MG susceptibility gene. HLA fine-mapping pointed to two independent MG loci: HLA-DRB1 and HLA-B. MG onset-specific analysis reveals differences in the genetic architecture of early-onset MG (EOMG) versus late-onset MG (LOMG). Furthermore, we find MG to be genetically correlated with type 1 diabetes (T1D), rheumatoid arthritis (RA), late-onset vitiligo and autoimmune thyroid disease (ATD). Cross-disorder meta-analysis reveals multiple risk loci that appear pleiotropic across MG and correlated disorders. DISCUSSION: Our gene-based analysis identifies AGRN as a novel MG susceptibility gene, implicating for the first time a locus encoding a protein (agrin) that is directly relevant to NMJ activation. Mutations in AGRN have been found to underlie congenital myasthenic syndrome. Our results are also consistent with previous studies highlighting the role of HLA and TNFRSF11A in MG aetiology and the different risk genes in EOMG versus LOMG. Finally, we uncover the genetic correlation of MG with T1D, RA, ATD and late-onset vitiligo, pointing to shared underlying genetic mechanisms.

A Comparison of Two Analytical Approaches for the Quantification of Neurofilament Light Chain, a Biomarker of Axonal Damage in Multiple Sclerosis.

Neurofilament light chain (NfL), is a neuron-specific cytoskeletal protein detected in extracellular fluid following axonal damage. Extensive research has focused on NfL quantification in CSF, establishing it as a prognostic biomarker of disability progression in Multiple Sclerosis (MS). Our study used a new commercially available Enzyme-Linked Immunosorbent Assay (ELISA) kit and Single Molecular Array (Simoa) advanced technology to assess serum NfL levels in MS patients and Healthy Controls (HC). Verifying the most accurate, cost-effective methodology will benefit its application in clinical settings. Blood samples were collected from 54 MS patients and 30 HC. Protocols accompanying the kits were followed. The ELISA thershold was set as 3 S.D. above the mean of the HC. For Simoa, the Z-score calculation created by Jens Kuhle's group was applied (with permission). Samples exceeding the threshold or z-score ≥1.5 indicated subclinical disease activity. To our knowledge, this is the first study to find strong-positive correlation between ELISA and Simoa for the quantification of NfL in serum (r = 0.919). Despite the strong correlation, Simoa has better analytical sensitivity and can detect small changes in samples making it valuable in clinical settings. Further research is required to evaluate whether serum NfL quantification using ELISA could be utilized to predict disability progression.

Potential Role of Antibodies against Aquaporin-1 in Patients with Central Nervous System Demyelination.

Aquaporins (AQPs; AQP0-AQP12) are water channels expressed in many and diverse cell types, participating in various functions of cells, tissues, and systems, including the central nervous system (CNS). AQP dysfunction and autoimmunity to AQPs are implicated in several diseases. The best-known example of autoimmunity against AQPs concerns the antibodies to AQP4 which are involved in the pathogenesis of neuromyelitis optica spectrum disorder (NMOSD), an autoimmune astrocytopathy, causing also CNS demyelination. The present review focuses on the discovery and the potential role of antibodies against AQP1 in the CNS, and their potential involvement in the pathophysiology of NMOSD. We describe (a) the several techniques developed for the detection of the AQP1-antibodies, with emphasis on methods that specifically identify antibodies targeting the extracellular domain of AQP1, i.e., those of potential pathogenic role, and (b) the available evidence supporting the pathogenic relevance of AQP1-antibodies in the NMOSD phenotype.

Main Role of Antibodies in Demyelination and Axonal Damage in Multiple Sclerosis.

Antibodies and oxidative stress are hallmarks of multiple sclerosis (MS) lesions. We aimed to clarify the relation between them, their role in MS patients and to investigate their specificity, comparing MS with classical neurodegenerative diseases (ND). Brain samples from 14 MS cases, 6 with ND and 9 controls (without neurological diseases). Immunohistochemistry assays were used to detect oxidized lipids (EO6), IgG and IgM, oligodendrocytes (Olig2), axons (NF, neurofilament) and cellular (TUNEL) and axonal damage (APP, amyloid precursor protein). We did not observe EO6 in controls. All samples from MS patients showed EO6 in oligodendrocytes and axons within lesions. We did not detect co-localization between EO6 and antibodies. Neither did we between EO6 and TUNEL or APP. 94.4% of TUNEL-positive cells in normal appearing white matter were also stained for IgG and 75.5% for IgM. IgM, but not IgG, co-localized with APP. EO6 was associated with axonal damage in amyotrophic lateral sclerosis (ALS). We did not observe association between antibodies and cellular or axonal damage in ND patients. MS patients showed a higher number of B cells and plasma cells in the lesions and meninges than controls. The number of B cells and plasma cells was associated with the presence of antibodies and with the activity of the lesions. We observed a main role of B lymphocytes in the development of MS lesions. Antibodies contribute to the oligodendrocyte and axonal damage in MS. Oxidative stress was associated with axonal damage in ALS.

Cortical involvement and leptomeningeal inflammation in myelin oligodendrocyte glycoprotein antibody disease: A three-dimensional fluid-attenuated inversion recovery MRI study.

BACKGROUND: Cortical demyelination and meningeal inflammation have been detected neuropathologically in multiple sclerosis (MS) and recently in myelin oligodendrocyte glycoprotein antibody disease (MOGAD). OBJECTIVES: To assess in vivo cortical and leptomeningeal involvement in MOGAD. METHODS: We prospectively evaluated 11 MOGAD and 12 relapsing-remitting MS (RRMS) patients combining three-dimensional fluid-attenuated inversion recovery (3D-FLAIR) and 3D-T1-weighted (3D-T1w) sequences at 3-Tesla magnetic resonance imaging (MRI). Leptomeningeal contrast enhancement (LMCE) was assessed on 3D-FLAIR post-gadolinium (3D-FLAIRGd). Cerebral cortical lesions (CCLs) were classified as either intracortical-subpial (IC-SP) or leukocortical (LC). RESULTS: CCLs were present in 8/11 MOGAD and 12/12 RRMS patients, with the number of CCLs being significantly lower in MOGAD (median (interquartile range (IQR)) 3 (0.5-4) vs 12 (4.75-19), p = 0.0032). In MOGAD, IC-SP lesions were slightly more prevalent than LC lesions (2 (0-2.5) vs 1 (0-2), p = 0.6579); whereas in RRMS, IC-SP lesions were less prevalent than LC lesions (3.5 (2.75-5.5) vs 9 (2-12.75), p = 0.27). LMCE was observed in 3/11 MOGAD and 1/12 RRMS patients; MOGAD with LMCE showed an increased median number of CCLs compared with MOGAD without LMCE (8 (4-9) vs 2.5 (0.75-3.25), p = 0.34). No correlation was observed between MOGAD MRI findings and (a) MOGAD duration, (b) serum MOG-immunoglobulin G1 titers, and (c) oligoclonal band presence. CONCLUSION: We described cortical lesion topography and detected for the first time LMCE using 3D-FLAIRGd sequences in MOGAD patients.

Autoantibody profile in myasthenia gravis patients with a refractory phase.

INTRODUCTION/AIMS: A subgroup of myasthenia gravis (MG) patients fail to respond adequately to recommended treatments, a condition referred to as refractory MG. During the refractory phase, patients experience persistent debilitating symptoms with potential life-threatening events or inability to reduce immunosuppressant dosages and minimize long-term toxicities. METHODS: We conducted a retrospective, single-center study of 113 MG patients to investigate the autoantibody profile and clinical characteristics of refractory MG patients, compared with nonrefractory patients, based on predefined criteria. RESULTS: Fifteen patients (13.3%) were classified as refractory. Double-seronegative MG (DSNMG), without detectable nicotinic acetylcholine receptor (AChR) or muscle-specific tyrosine kinase (MuSK) antibodies, was identified in six refractory patients, significantly higher than those with nonrefractory MG (40% vs 16.3%; P = .031). None of the refractory patients had MuSK antibodies. Patients in the refractory group more frequently had an earlier disease onset, thymic pathology, and thymectomy (P ≤. 03 for all). DISCUSSION: In this study, patients with refractory MG were more likely than those with nonrefractory MG to be DSN; and refractory DSNMG patients had worse MGFA classes in their recent visit compared with anti-AChR positive refractory patients. Refractory DSNMG patients may represent a distinct group that requires more individualized and targeted treatment approaches.

Concordance of cerebrospinal fluid real-time quaking-induced conversion across the European Creutzfeldt-Jakob Disease Surveillance Network.

BACKGROUND AND PURPOSE: Cerebrospinal fluid (CSF) real-time quaking-induced conversion (RT-QuIC) has a high degree of sensitivity and specificity for the diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD) and this has led to its being included in revised European CJD Surveillance Network diagnostic criteria for sCJD. As CSF RT-QuIC becomes more widely established, it is crucial that the analytical performance of individual laboratories is consistent. The aim of this ring-trial was to ascertain the degree of concordance between European countries undertaking CSF RT-QuIC. METHODS: Ten identical CSF samples, seven from probable or neuropathologically confirmed sCJD and three from non-CJD cases, were sent to 13 laboratories from 11 countries for RT-QuIC analysis. A range of instrumentation and different recombinant prion protein substrates were used. Each laboratory analysed the CSF samples blinded to the diagnosis and reported the results as positive or negative. RESULTS: All 13 laboratories correctly identified five of the seven sCJD cases and the remaining two sCJD cases were identified by 92% of laboratories. Of the two sCJD cases that were not identified by all laboratories, one had a disease duration >26 months with a negative 14-3-3, whilst the remaining case had a 4-month disease duration and a positive 14-3-3. A single false positive CSF RT-QuIC result was observed in this study. CONCLUSIONS: This study shows that CSF RT-QuIC demonstrates an excellent concordance between centres, even when using a variety of instrumentation, recombinant prion protein substrates and CSF volumes. The adoption of CSF RT-QuIC by all CJD surveillance centres is recommended.

Effects of Teriflunomide on B Cell Subsets in MuSK-Induced Experimental Autoimmune Myasthenia Gravis and Multiple Sclerosis.

Antigen-specific immune responses are crucially involved in both multiple sclerosis (MS) and myasthenia gravis (MG). Teriflunomide is an immunomodulatory agent approved for treatment of MS through inhibition of lymphocyte proliferation. MG associated with muscle-specific tyrosine kinase (MuSK) antibodies often manifests with a severe disease course, prompting development of effective treatment methods. To evaluate whether teriflunomide treatment may ameliorate MuSK-autoimmunity, experimental autoimmune MG (EAMG) was induced by immunizing C57BL/6 (B6) mice three times with MuSK in complete Freund's adjuvant (CFA) (n = 17). MuSK-immunized mice were treated daily with teriflunomide (n = 8) or PBS (n = 9) starting from the third immunization (week 8) to termination (week 14). Clinical severity of EAMG was monitored. Immunological alterations were evaluated by measurement of anti-MuSK IgG, neuromuscular junction deposits, and flow cytometric analysis of lymph node cells. In MS patients under teriflunomide treatment, the peripheral blood B cell subset profile was analyzed. B6 mice treated with teriflunomide displayed relatively preserved body weight, lower EAMG prevalence, reduced average clinical grades, higher inverted screen scores, diminished anti-MuSK antibody and NMJ deposit levels. Amelioration of EAMG findings was associated with reduced memory B cell ratios in the lymph nodes. Similarly, MS patients under teriflunomide treatment showed reduced memory B cell, plasma cell, and plasmablast ratios. Teriflunomide treatment has effectively ameliorated MuSK-autoimmunity and thus may putatively be used in long-term management of MuSK-MG as an auxiliary treatment method. Teriflunomide appears to exert beneficial effects through inhibition of effector B cells.

Serum glial fibrillary acidic protein (GFAP)-antibody in idiopathic intracranial hypertension.

AIM: Idiopathic intracranial hypertension (IIH), a disease of obscure origin, is characterized by headache and visual disturbances due to increased intracranial pressure. Recent line of evidence has suggested involvement of inflammation in IIH pathogenesis thus bringing forward anti-glial autoimmunity as a potential contributor of IIH. Glial fibrillary acidic protein (GFAP) is a major astrocytic autoantigen associated with a specific form of meningoencephalitis. MATERIALS AND METHODS: In this study, we investigated the presence of GFAP-antibody in 65 sera (49 obtained during active disease and 16 during remission) and in 15 cerebrospinal fluid (CSF) samples of 58 consecutively recruited IIH patients using cell based assay and indirect immunohistochemistry. RESULTS: GFAP-antibody was found in active period sera of 2 IIH patients with classical symptoms and good treatment response. Two remission period sera obtained at different time points from one of these cases showed lower titers of GFAP-antibody positivity. IgG from positive samples yielded an astrocytic immunoreactivity pattern. None of the CSF samples showed GFAP-antibodies. CONCLUSIONS: These results suggest that anti-astrocyte autoimmunity might be present in a fraction of IIH patients. Exact pathogenic significance of this association needs to be further studied.

A probable role of copper in the comorbidity in Wilson's and Creutzfeldt-Jakob's Diseases: a case report.

BACKGROUND: To the best of our knowledgedd, there is currently no case in the literature reporting the comorbidity of Wilson's and Creutzfeldt-Jakob disease (CJD), linked through copper. CASE PRESENTATION: A 44-year-old male with a history of inherited Wilson's disease (hepatolenticular degeneration), which manifested as mild liver injury and psychiatric symptoms, was admitted to our department due to speech and cognitive disturbances. Upon his admission, he had motor aphasia as well as psychomotor retardation with an otherwise normal neurological examination. Laboratory tests, including liver enzymes, copper and serum ammonia were all within normal range. The brain MRI showed increased T2 signal in the caudate nuclei, attributed to copper deposition in the context of Wilson's disease. In the electroencephalogram, periodic sharp discharges were eminent, initially unilateral and then generalized. The positive 14-3-3 protein in the cerebrospinal fluid (CSF) and the new brain MRI, that demonstrated elevated DWI signal not only in the basal ganglia but also in parts of the cerebral cortex (cortical ribbon sign), all supportive of a possible CJD diagnosis. The detection of PrPSc in the patient's CSF, using the RT-QuIC method, which has a 99.4-100% specificity for CJD, made the diagnosis of CJD highly probable. CONCLUSION: This is the first report of Wilson's and Creutzfeldt-Jakob diseases co-morbidity in the literature, which could evoke a possible role of copper in the pathogenesis of CJD.

Recurrent myelitis and asymptomatic hypophysitis in IgG4-related disease: case-based review.

IgG4-related disease (IgG4-RD) is a disorder with various clinical manifestations. Central nervous system (CNS) involvement is well recognized, with hypertrophic pachymeningitis and hypophysitis being the most common manifestations. Spinal cord involvement is an extremely rare manifestation. We present the first case of an IgG4-RD patient with spinal cord parenchymal disease and concurrent hypophysitis. We review also the current literature about CNS parenchymal involvement in the context of IgG4-RD. A young female presented with clinical symptoms of myelitis. Cervical spinal cord magnetic resonance imaging (MRI) displayed features of longitudinally extensive transverse myelitis (LETM). Brain MRI showed a small number of high-intensity lesions in the deep white matter and enlargement of hypophysis with homogeneous gadolinium enhancement (asymptomatic hypophysitis). Diagnostic workup revealed elevated IgG4 serum levels (146 mg/dL). Our patient fulfilled the organ-specific diagnostic criteria of IgG4-hypophysitis. Treatment with intravenous glucocorticoids led to rapid clinical response, and to the substantial resolution of imaging findings. Azathioprine was used as a maintenance treatment. One relapse occurred 2 years after the initial diagnosis and patient was re-treated with glucocorticoids. Three years after relapse, patient is in remission with azathioprine. We present the first case of myelitis with radiological features of LETM associated with increased IgG4 serum levels and the simultaneous presence of asymptomatic IgG4-related hypophysitis.

X linked Charcot-Marie-Tooth disease and multiple sclerosis: emerging evidence for an association.

OBJECTIVE: X linked Charcot-Marie-Tooth disease (CMTX) is a hereditary neuropathy caused by mutations in GJB1 coding for connexin-32, a gap junction protein expressed in Schwann cells, but also found in oligodendrocytes. Four patients with CMTX developing central nervous system (CNS) demyelination compatible with multiple sclerosis (MS) have been individually published. We presently sought to systematically investigate the relationship between CMTX and MS. METHODS: Over 20 years, 70 consecutive patients (36 men) with GJB1 mutations were identified at our Neurogenetics Unit, Athens, Greece, and assessed for clinical features suggestive of MS. Additionally, 18 patients with CMTX without CNS symptoms and 18 matched controls underwent brain MRI to investigate incidental findings. Serum from patients with CMTX and MS was tested for CNS immunoreactivity. RESULTS: We identified three patients with CMTX who developed clinical features suggestive of inflammatory CNS demyelination fulfilling MS diagnostic criteria. The resulting 20-year MS incidence (4.3%) differed significantly from the highest background 20-year MS incidence ever reported from Greece (p=0.00039). The search for incidental brain MRI findings identified two CMTX cases (11%) with lesions suggestive of focal demyelination compared with 0 control. Moreover, 10 cases in the CMTX cohort had hyperintensity in the splenium of the corpus callosum compared with 0 control (p=0.0002). No specific CNS-reactive humoral factors were identified in patients with CMTX and MS. CONCLUSIONS: We have demonstrated a higher than expected frequency of MS in patients with CMTX and identified incidental focal demyelinating lesions on brain MRI in patients with CMTX without CNS symptoms. This provides circumstantial evidence for GJB1 mutations acting as a possible MS risk factor.

Ocular flutter as presenting manifestation of pediatric MOG antibody-associated demyelination: A case report.

A 13-year-old girl presented with a 5-day history of oscillopsia. On examination, ocular flutter and mild cerebellar signs were found. Brain magnetic resonance imaging (MRI) revealed four periventricular and subcortical non-enhancing lesions. Cerebrospinal fluid (CSF) oligoclonal bands were negative. Neuroblastoma or other malignancies were not found. She responded well to a corticosteroid-intravenous immunoglobulin (IVIG) combination and remained symptom-free for 3 years until presenting again with isolated ocular flutter. Brain MRI at this time remained atypical for classic multiple sclerosis (MS) with a predominance of juxtacortical demyelinating lesions. CSF was positive for oligoclonal bands. Serum myelin oligodendrocyte glycoprotein (MOG) antibodies were present. Ocular flutter can be the presenting feature of MOG antibody-associated pediatric demyelination.

T cell-mediated autoimmune disease due to low-affinity crossreactivity to common microbial peptides.

Environmental factors account for 75% of the risk of developing multiple sclerosis (MS). Numerous infections have been suspected as environmental disease triggers, but none of them has consistently been incriminated, and it is unclear how so many different infections may play a role. We show that a microbial peptide, common to several major classes of bacteria, can induce MS-like disease in humanized mice by crossreacting with a T cell receptor (TCR) that also recognizes a peptide from myelin basic protein, a candidate MS autoantigen. Structural analysis demonstrates this crossreactivity is due to structural mimicry of a binding hotspot shared by self and microbial antigens, rather than to degenerate TCR recognition. Biophysical studies reveal that the autoreactive TCR binding affinity is markedly lower for the microbial (mimicry) peptide than for the autoantigenic peptide. Thus, these data suggest a possible explanation for the difficulty in incriminating individual infections in the development of MS.

Antibodies to aquaporins are frequent in patients with primary Sjögren's syndrome.

Objectives: Several aquaporins (AQPs) are present in the salivary glands, likely contributing to their secretions. AQP dysfunction may contribute to the salivary gland dysfunction in SS. Antibodies to AQP4 and AQP1 are detected in neuromyelitis optica and are believed to play a pathogenic role. We aimed to search for antibodies to several AQPs in the sera from SS patients in an effort to shed light on the pathogenic mechanisms of SS. Methods: We searched for antibodies to six AQPs in the sera of 34 SS patients without neurological findings using ELISAs with synthetic peptides corresponding to the three extracellular domains of each AQP, radioimmunoassays with AQPs, Western blots and competition experiments with cell-embedded AQPs. Results: Thirteen (38.2%) SS patients had antibodies to extracellular domains of AQP1 (two), AQP3 (one), AQP8 (six) or AQP9 (four); none had AQP4 or AQP5 antibodies. Each patient had antibodies to only one extracellular domain. AQP binding was further verified by radioimmunoassay with intact AQPs, western blots and AQP-transfected cells. In contrast, none of the 106 healthy controls or 68 patients with other autoimmune diseases had antibodies to intact AQPs. Expression of AQP8 (the major antibody target) on human salivary glands was shown by immunohistochemistry. Patients with anti-AQP antibodies had more severe xeropthalmia compared with anti-AQP-negative patients, suggesting a potential pathogenic role of these antibodies. Conclusion: Antibodies to AQPs (especially to AQP8 and AQP9) are frequent in SS patients. The likely important role of AQPs in salivary gland secretions justifies further research.