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Caspr2 autoantibodies target multiple epitopes.

ABSTRACT: To better understand the mechanisms of autoantibodies to the axonal protein contactin-associated protein-like 2 (Caspr2) by studying their target epitopes.A plasmid for expressing Caspr2 was modified so that the various extracellular subdomains were deleted individually and in groups. Cultured cells were transfected to express these constructs and assayed by immunofluorescence staining with a commercial Caspr2 antibody and a panel of patient sera known to react with Caspr2. Western blotting was also performed. The role of glycosylation in immunogenicity was tested with tunicamycin and PNGase F treatment.Patient antibodies bound to the extracellular domain of Caspr2. Neither native protein structure nor glycosylation was required for immunoreactivity. Caspr2 constructs with single or multidomain deletions were expressed on the plasma membrane. All deletion constructs were recognized by patients' sera, although reactivity was significantly reduced with deletion of the discoidin-like subdomain and strongly reduced or abolished with larger deletions of multiple N-terminal subdomains. Caspr2 with all subdomains deleted except the discoidin-like domain was still recognized by the antibodies.Caspr2 autoantibodies recognize multiple target epitopes in the extracellular domain of Caspr2, including one in the discoidin-like domain. Reactivity for some epitopes is not dependent on glycosylation or native protein structure.

SUBMITTER: Olsen AL

PROVIDER: S-EPMC4496632 | biostudies-literature | 2015 Aug

REPOSITORIES: biostudies-literature

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Caspr2 autoantibodies target multiple epitopes.

Olsen Abby L AL Lai Yongjie Y Dalmau Josep J Scherer Steven S SS Lancaster Eric E

Neurology(R) neuroimmunology & neuroinflammation 20150702 4

<h4>Objective</h4>To better understand the mechanisms of autoantibodies to the axonal protein contactin-associated protein-like 2 (Caspr2) by studying their target epitopes.<h4>Methods</h4>A plasmid for expressing Caspr2 was modified so that the various extracellular subdomains were deleted individually and in groups. Cultured cells were transfected to express these constructs and assayed by immunofluorescence staining with a commercial Caspr2 antibody and a panel of patient sera known to react ...[more]

PMID: 26185774

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Project description:ObjectiveTo examine the clinical characteristics of autoimmune encephalitis associated with the contactin-associated protein-2 (CASPR2) antibody.Materials and methodsMedical records of all patients diagnosed with CASPR2 antibody-associated encephalitis were retrospectively analysed. Data regarding demographic features, neurological symptoms and signs, laboratory tests, imaging results, treatments, and prognosis were collected.ResultsA total of 25 patients aged from 3 to 79 years old were enrolled in this study, with a median age of 43. Eight of 25 (32%) were female, and 17 of 25 (68%) were male. The median age of symptom onset was 42 years old with the course of disease from onset to hospital admission ranging from 2 days to 6 months (median was 17 days). Six patients (6/25) had fever as an onset symptom. During the course of disease, cognitive disturbance was the most common symptom, which was observed in 17 patients (17/25) in total. Eight patients (8/25) met the criteria for limbic encephalitis. Epileptic seizure occurred in six of these eight patients. Four patients (4/25) were diagnosed as Morvan syndrome. All patients were positive for anti-CASPR2 antibody in the serum (1:10-1:300). In six patients, antibodies were detected both in the blood and CSF (1:32-1:100). White blood cell (WBC) counts in the CSF were elevated in eight patients (8/25). The concentration of proteins in CSF increased in 10 patients (ranging from 480 to 1,337.6 mg/dl), decreased in seven patients (ranging from 23.2 to 130.5 mg/dl) and remained at a normal range in the other eight patients (ranging from 150 to 450 mg/dl). Abnormal electroencephalogram (EEG) activities included slow background activity and epileptic patterns. Abnormal signals in the bilateral hippocampus were detected by magnetic resonance imaging (MRI) in three patients presenting cognitive disturbance. In one patient who had limbic encephalitis, increased metabolism of bilateral basal ganglia and the mesial temporal lobe was revealed by PET-CT. Eleven of 15 patients receiving immunotherapy experienced varying degrees of improvement. Relapse occurred in four of 25 patients (4/25) after 2 months.ConclusionCASPR-antibody-mediated autoimmune encephalitis is characterized by diverse clinical manifestations. The most prominent conclusion revealed by this retrospective analysis is the involvement of both central and peripheral nerve systems, as well as a lower relapse rate, a good response to immunotherapy, and favorable short-term prognosis after treatment was also demonstrated. Besides, additional work is necessary to evaluate the long-term prognosis.

Project description:Background and objectivesApproximately 20%-30% of patients with anti-glomerular basement membrane disease present coexisting anti-myeloperoxidase (MPO) autoantibodies. We previously showed the recognition of a linear fragment of the MPO heavy chain N-terminus ((1)H, MPO279-409) in plasma from most double-positive patients. Herein, we investigated the frequency of autoantibodies against overlapping (1)H-derived linear peptides in plasma from patients with anti-glomerular basement membrane disease.Design, setting, participants, & measurementsWe synthesized 13 overlapping linear peptides ((1)H-1 to (1)H-13) covering MPO279-409. We retrospectively collected plasma samples from 67 patients with anti-glomerular basement membrane disease from 1996 to 2012, and we screened them for IgG autoantibodies by ELISA using intact human MPO and the overlapping peptides as antigens, and we further investigated the clinical significance. Autoantibody binding to the linear MPO structure was confirmed by Western blotting.ResultsWe followed up the 67 patients until 2015, with a median follow-up time of 10.0 (2.3-36.0) months, and 56 ESRD events occurred among the 67 patients with follow-up data. Plasma from 23.9% (16) of the patients recognized intact human MPO, whereas 62.7% (42) plasma samples recognized MPO279-409 linear peptides. Of the 13 linear peptides, (1)H-4 (44.8%, 30 patients) and (1)H-12 (40.3%, 27 patients) exhibited the highest recognition frequencies. Patients with autoantibodies against (1)H-11 or (1)H-12 (MPO371-400) were older (46.1±18.8 versus 34.1±16.6 years; P<0.01), had higher serum creatinine upon diagnosis (median 7.8 mg/dl, interquartile range 4.9-12.6 mg/dl versus median 5.4 mg/dl, interquartile range 2.4-7.3 mg/dl; P=0.02), and had a higher probability of progressing to ESRD; however, multivariate Cox regression analysis showed that (1)H-11 or 12 reaction was not an independent risk factor for renal failure (hazard ratio, 1.2; 95% confidence interval, 0.8 to 2.8; P=0.19).ConclusionsAutoantibodies against linear peptides of MPO can be detected in the majority of patients with anti-glomerular basement membrane disease, and several are associated with disease severity. The potential common pathogenic mechanism between anti-glomerular basement membrane antibodies and anti-MPO autoantibodies in anti-glomerular basement membrane disease requires further investigation.

Project description:Several groups have described the presence of fetal brain-reactive maternal autoantibodies in the plasma of some mothers whose children have autism spectrum disorder (ASD). We previously identified seven autoantigens targeted by these maternal autoantibodies, each of which is expressed at significant levels in the developing brain and has demonstrated roles in typical neurodevelopment. To further understand the binding repertoire of the maternal autoantibodies, as well as the presence of any meaningful differences with respect to the recognition and binding of these ASD-specific autoantibodies to each of these neuronal autoantigens, we utilized overlapping peptide microarrays incubated with maternal plasma samples obtained from the Childhood Autism Risk from Genetics and Environment (CHARGE) Study. In an effort to identify the most commonly recognized (immunodominant) epitope sequences targeted by maternal autoantibodies for each of the seven ASD-specific autoantigens, arrays were screened with plasma from mothers with children across diagnostic groups (ASD and typically developing (TD)) that were positive for at least one antigen by western blot (N = 67) or negative control mothers unreactive to any of the autoantigens (N = 18). Of the 63 peptides identified with the discovery microarrays, at least one immunodominant peptide was successfully identified for each of the seven antigenic proteins using subsequent selective screening microarrays. Furthermore, while limited by our relatively small sample size, there were peptides that were distinctly recognized by autoantibodies relative to diagnosis For example, reactivity was observed exclusively in mothers of children of ASD towards several peptides, including the LDH-B peptides DCIIIVVSNPVDILT (9.1% ASD vs. 0% TD; odds ratio (95% CI) = 6.644 (0.355-124.384)) and PVAEEEATVPNNKIT (5.5% ASD vs. 0% TD; odds ratio (95% CI) = 4.067 (0.203-81.403)).These results suggest that there are differences in the binding repertoire between the antigen positive ASD and TD maternal samples. Further, the autoantibodies in plasma from mothers of children with ASD bound to a more diverse set of peptides, and there were specific peptide binding combinations observed only in this group. Future studies are underway to determine the critical amino acids necessary for autoantibody binding, which will be essential in developing a potential therapeutic strategy for maternal autoantibody related (MAR) ASD.

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Caspr2 autoantibodies target multiple epitopes.

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Caspr2 autoantibodies target multiple epitopes.

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