Detection of anti-glutamic acid decarboxylase antibodies in immunoglobulin products

Focal Status Epilepticus and Extreme Delta Brush Associated With Thrombotic Thrombocytopenic Purpura

Acute focal neurological deficits demand immediate evaluation. In this report, we present the case of a woman 20-some years of age with a history of hemolytic anemia and thrombocytopenia who presented with altered mental status and focal neurological deficits including aphasia, acute left gaze preference, right homonymous hemianopsia, right lower facial weakness, and right arm and leg weakness. Extensive neurological and hematological workup revealed that the patient suffered from focal status epilepticus associated with an extreme delta brush patten on electroencephalogram, likely secondary to thrombotic thrombocytopenic purpura. This case underscores the connection between hematological disorders and the neurological axis, emphasizing the critical role of integrating the neurological examination and neuroimaging findings to formulate an effective management plan.

Autoantibody profiles in intravenous immunoglobulin preparations: A possible cause of mistaken autoimmunity diagnosis

BACKGROUND

Intravenous immunoglobulins (IVIgs) derived from the pooled plasma of thousands of donors contain numerous types of IgG molecules, including autoantibodies commonly used to diagnose autoimmunity. While these autoantibodies can cause misinterpretation of serological tests for IVIg recipients, their profiles in IVIg preparations are not fully understood.

STUDY DESIGN AND METHODS

Using binding-capability based immune assays, we measured 18 varieties of clinically relevant autoantibodies in domestic blood donor-derived IVIg products. In addition, we analyzed an IVIg product from a US brand to evaluate the influence of regional and racial differences. Based on the determined autoantibody titers, pharmacokinetics of passively acquired autoantibodies and their possible detection period in serum were estimated.

RESULTS

Anti-thyroglobulin (Tg), anti-thyroidperoxidase (TPO), and anti-Sjögren's-syndrome-related antigen A (SS-A) antibodies were present in considerable amounts in IVIg products. Notably, these three autoantibodies can be detected in IVIg recipients' sera for up to 3 months after infusion.

DISCUSSION

To the best of our knowledge, this is the first study that analyzed multiple autoantibody profiles in both pooled plasma and IVIg products and that further evaluated their potential influences on diagnosis of autoimmunity. Clinicians should keep in mind that IVIgs contain several autoantibodies and that their infusion can produce false-positive serology results. To establish an accurate diagnosis, serological tests must be carefully interpreted and clinical symptoms should be more purposefully considered if patients are receiving IVIg therapy.

Anti-Inflammatory and Immunomodulatory Effect of High-Dose Immunoglobulins in Children: From Approved Indications to Off-Label Use

BACKGROUND

The large-scale utilization of immunoglobulins in patients with inborn errors of immunity (IEIs) since 1952 prompted the discovery of their key role at high doses as immunomodulatory and anti-inflammatory therapy, in the treatment of IEI-related immune dysregulation disorders, according to labelled and off-label indications. Recent years have been dominated by a progressive imbalance between the gradual but constant increase in the use of immunoglobulins and their availability, exacerbated by the SARS-CoV-2 pandemic.

OBJECTIVES

To provide pragmatic indications for a need-based application of high-dose immunoglobulins in the pediatric context.

SOURCES

A literature search was performed using PubMed, from inception until 1st August 2023, including the following keywords: anti-inflammatory; children; high dose gammaglobulin; high dose immunoglobulin; immune dysregulation; immunomodulation; immunomodulatory; inflammation; intravenous gammaglobulin; intravenous immunoglobulin; off-label; pediatric; subcutaneous gammaglobulin; subcutaneous immunoglobulin. All article types were considered.

IMPLICATIONS

In the light of the current imbalance between gammaglobulins' demand and availability, this review advocates the urgency of a more conscious utilization of this medical product, giving indications about benefits, risks, cost-effectiveness, and administration routes of high-dose immunoglobulins in children with hematologic, neurologic, and inflammatory immune dysregulation disorders, prompting further research towards a responsible employment of gammaglobulins and improving the therapeutical decisional process.

Autoantibodies Against Proteins Previously Associated With Autoimmunity in Adult and Pediatric Patients With COVID-19 and Children With MIS-C

The antibody profile against autoantigens previously associated with autoimmune diseases and other human proteins in patients with COVID-19 or multisystem inflammatory syndrome in children (MIS-C) remains poorly defined. Here we show that 30% of adults with COVID-19 had autoantibodies against the lung antigen KCNRG, and 34% had antibodies to the SLE-associated Smith-D3 protein. Children with COVID-19 rarely had autoantibodies; one of 59 children had GAD65 autoantibodies associated with acute onset of insulin-dependent diabetes. While autoantibodies associated with SLE/Sjögren's syndrome (Ro52, Ro60, and La) and/or autoimmune gastritis (gastric ATPase) were detected in 74% (40/54) of MIS-C patients, further analysis of these patients and of children with Kawasaki disease (KD), showed that the administration of intravenous immunoglobulin (IVIG) was largely responsible for detection of these autoantibodies in both groups of patients. Monitoring in vivo decay of the autoantibodies in MIS-C children showed that the IVIG-derived Ro52, Ro60, and La autoantibodies declined to undetectable levels by 45-60 days, but gastric ATPase autoantibodies declined more slowly requiring >100 days until undetectable. Further testing of IgG and/or IgA antibodies against a subset of potential targets identified by published autoantigen array studies of MIS-C failed to detect autoantibodies against most (16/18) of these proteins in patients with MIS-C who had not received IVIG. However, Troponin C2 and KLHL12 autoantibodies were detected in 2 of 20 and 1 of 20 patients with MIS-C, respectively. Overall, these results suggest that IVIG therapy may be a confounding factor in autoantibody measurements in MIS-C and that antibodies against antigens associated with autoimmune diseases or other human proteins are uncommon in MIS-C.

Super refractory status epilepticus secondary to anti-GAD antibody encephalitis successfully treated with aggressive immunotherapy

Antibodies against glutamic acid decarboxylase are reported in association with a number of neurological conditions including limbic encephalitis. We report a case of anti-GAD-antibody associated encephalitis presenting with super-refractory status epilepticus. We describe the clinical course, management, and the outcome. In addition, we review the presentation and outcomes of reported cases of anti-GAD encephalitis. Similar to the reported cases of anti-GAD encephalitis, our case was refractory to treatment with conventional antiseizure medication. Treatment with intravenous immune globulin (IVIG), high dose corticosteroids, and plasmapheresis had partial response, but escalation of treatment to the use of tocilizumab was associated with significant clinical improvement.

Anti-Neuronal Antibodies Within the IVIg Preparations: Importance in Clinical Practice

Our study objective was testing for anti-neuronal autoantibodies within commercially available intravenous immunoglobulin (IVIg) preparations. Sixteen samples from 5 different commercially available IVIg preparations were tested with cell-based assays (CBA) and enzyme-linked immunosorbent assay (ELISA) to detect and characterize common neuronal autoantibodies, and with immunohistochemistry on teased fibers from mouse sciatic nerve and on mouse brain sections to screen for nodal and not yet identified neuronal antigens. In 15/16 IVIg preparations, anti-GAD antibodies were detected in titers ranging from 40 to 1507 IU/mL, as typically seen in type 1 diabetes, but not in the range (> 2000 IU/mL) seen in GAD-positive neurological patients. None of the preparations was however positive with anti-GAD CBA. Antibodies to AQP4 were also detected by ELISA in 15/16 IVIg preparations with titers comparable to those seen in AQP4-seropositive NMO patients; with CBA, however, all IVIg samples were AQP4-negative. IVIg preparations contained IgG-anti-MAG antibodies by ELISA at statistically significant higher titers compared to controls. Two of the 16 IVIg samples were positive for human 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) antibodies. All IVIg preparations were negative for antibodies to MOG, NMDAR, anti-nodal, and other neuronal-specific proteins. IVIg preparations contain antibodies against GAD and AQP4 in titers comparable to those seen in autoimmune patients when tested by ELISA, but not by CBA or tissue immunohistochemistry, suggesting that the autoantibodies within the IVIg are against linear rather than structural epitopes, as part of the natural antibody immune repertoire. The information is clinically important for diagnosis when testing patients' sera after they have received therapy with IVIg to avoid false interpretation.

Effects of IVIg treatment on autoantibody testing in neurological patients: marked reduction in sensitivity but reliable specificity

BACKGROUND

Therapy of autoimmune diseases of the central and peripheral nervous system with intravenous IgG immunoglobulin (IVIg) is well established. Since IVIg is produced from pooled human plasma, autoantibodies can be found in IVIg products and, accordingly, in patient sera after transfusion. The de novo evidence or disappearance of anti-neural autoantibodies after IVIg treatment has so far not been systematically examined.

METHODS

We screened 50 neurological patients before and after IVIg treatment for classical onconeural and the most common neurological surface autoantibodies as well as for ganglioside autoantibodies and 23 different antinuclear autoantibodies using immunoblot or cell-based indirect immunofluorescence assays. Furthermore, we screened 31 neurological patients with previously known seropositivity for disappearance of the corresponding antibody after treatment.

RESULTS

After IVIg treatment, 90% of all sera were de novo positive for antinuclear antibodies, especially for Ro-52. In contrast, 94% of all sera did not show any de novo-positive anti-neural antibodies. In the remaining three cases, titers were very low. Importantly, 12.9% of all tested sera of patients with known antibody positivity turned false negative after IVIg treatment and titers were falsely low in 37% of the remaining sera.

CONCLUSIONS

Here, we present for the first time results of a broad screening for clinically relevant autoantibodies before and after IVIg treatment in neurological patients. We identified a high specificity but reduced sensitivity for anti-neural antibody testing after IVIg transfusion. In contrast, antinuclear antibody testing is not reliable after IVIg treatment. These results are of high practical importance for diagnostic of neuroimmunological diseases.

Heidenhain variant sporadic Creutzfeldt-Jakob disease diagnosed as an autoimmune encephalitis due to a false-positive GAD autoantibody

A 64-year-old man presented with a subacute history progressive visual field defects, illusions and misperceptions. An initial MRI brain revealed a right occipital signal abnormality on diffusion-weighted imaging (DWI) with serum glutamic acid decarboxylase (GAD) autoantibodies markedly elevated. A diagnosis of autoimmune encephalitis was made, with the patient being treated with intravenous immunoglobulin. One month after discharge, the patient represented with worsening frank and well-formed visual hallucinations, ataxia and progressive cognitive impairment. Progress MRI displayed characteristic T2 ribboning on diffusion weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) sequences, along with periodic sharp wave complexes on electroencephalogram (EEG) and a raised CSF protein 14-3-3. Repeat serum, as well as cerebrospinal fluid (CSF), GAD antibodies were again markedly elevated as measured by ELISA (RSR, Cardiff, UK), although archival CSF from the original presentation as well as CSF from the second presentation had undetectable GAD autoantibodies as measured via radioimmunoassay (DIAsource, Ottignies-Louvain-la-Neuve, Belgium). Creutzfeldt-Jakob disease was confirmed at autopsy.