Detection of autoantibodies in central nervous system inflammatory disorders: Clinical application of cell-based assays

Utility of Oligoclonal Band Testing in Differentiating Immune-Mediated From Infectious Central Nervous System Disorders

OBJECTIVE

This study aimed to evaluate the clinical utility of oligoclonal bands (OCB) in differentiating between immune and infectious diseases of the central nervous system (CNS).

METHODS

The study enrolled patients hospitalized with suspected autoimmune or infectious CNS disorders between 2021 and 2023. Patients were categorized into diagnostic groups: multiple sclerosis (MS), neuromyelitis optica spectrum disorders (NMOSD), autoimmune encephalitis (AE), and viral encephalitis (VE). Relevant clinical and laboratory data were collected and subjected to comparative analysis.

RESULTS

Comparative analysis among the 4 groups revealed that the immunoglobulin G (IgG) index of patients in the MS group was significantly higher than that of patients in the NMOSD and VE groups (P < 0.05). The 24-hour intrathecal synthesis rate of IgG also differed significantly between the MS and NMOSD groups, the NMOSD and AE groups, as well as the AE and VE groups (P < 0.05). The positive rate of OCB was significantly higher in the MS group than in the other 3 groups (P < 0.05). Functional abilities, measured by scores of the Modified Rankin Scale (mRS) and the Expanded Disability Status Scale (EDSS), were higher in the immune group than in the infection group at 1-week, 1-month, 6-month, and 1-year post-treatment. Among patients with immune diseases, those who were OCB-positive showed significantly smaller ΔmRS and ΔEDSS at 1-month, 6-month, and 1-year post-treatment compared with patients who were OCB-negative (P < 0.05).

CONCLUSION

The IgG index and 24-hour intrathecal synthesis rate of IgG served as valuable early indicators for distinguishing between CNS immune and infectious diseases. Positive OCB findings were more common in patients with MS and often associated with poor prognosis and increased risk of disease recurrence.

Validation of the clinical assessment scale for autoimmune encephalitis in a severe autoimmune encephalitis cohort

Objective

The Clinical Assessment Scale for Autoimmune Encephalitis (CASE) is a novel tool tailored specifically for evaluating the severity of autoimmune encephalitis (AE). However, its application in severe AE patients is limited. This study aimed to evaluate the reliability and validity of the CASE and explore its clinical significance in a severe AE cohort.

Methods

The relevant clinical characteristics, laboratory data, and prognosis of patients diagnosed with severe AE between April 2017 and April 2023 were collected. The CASE and modified Rankin scale (mRS) were performed at admission, discharge, and 1-year follow-up, respectively. The reliability of CASE was validated by calculating the Cronbach's alpha value. The validity was evaluated by calculating the Spearman's rank correlation with the corresponding mRS. Univariate and multivariate logistic regression were utilized to identify risk factors for poor prognosis.

Results

A total of 140 patients were recruited for the study. The CASE scale presented great internal consistency, with Cronbach's α value of 0.768 for the total score. The Spearman's rank correlation analysis revealed strong criterion validity between CASE and mRS, with coefficients of 0.68, 0.92, and 0.95 at admission, discharge, and 1-year follow-up, respectively (all p < 0.001). ROC analysis identified CASE score at admission served as a promising predictive marker for clinical response to treatment, with an AUC of 0.67 (95% CI: 0.57-0.77, p = 0.003). The optimal cut-off point was 22.5. At 1-year follow-up, 72/140 (51.4%) patients achieved good functional status (mRS, 0-2). Multivariate logistic regression confirmed that higher CASE scores on admission and older age at onset were associated with poor short-term as well as 1-year prognosis, respectively. In addition, no clinical response to treatment (OR = 40.499; 95% CI: 7.077-231.746, p < 0.001) and longer duration of hospitalization (OR = 1.071; 95% CI: 1.017-1.128, p = 0.010) were associated with poor function states at 1-year follow-up.

Conclusion

The CASE has proven suitable for evaluating disease severity and prognosis in severe AE patients. Besides, CASE score, age at disease onset, hospital stays, and response to immunotherapy are identified as independent risk factors for unsatisfactory prognosis in severe AE patients.

Cell-based vs enzyme-linked immunosorbent assay for detection of anti-Tribbles homolog 2 autoantibodies in Chinese patients with narcolepsy

STUDY OBJECTIVES

Narcolepsy type 1 is attributed to a deficiency in cerebrospinal fluid orexin and is considered linked to autoimmunity. The levels of anti-Tribbles homolog 2 (TRIB2) autoantibodies are elevated in the sera of some patients with narcolepsy with cataplexy. Additionally, injecting mice with serum immunoglobulin from patients with narcolepsy with positive anti-TRIB2 antibodies can induce hypothalamic neuron loss and alterations in sleep patterns. Consequently, we hypothesized the existence of a potential association between anti-TRIB2 antibodies and narcolepsy. To test this possibility, we used cell-based assays (CBAs) and enzyme-linked immunosorbent assays (ELISAs) to detect the presence of anti-TRIB2 antibodies in Chinese patients with narcolepsy.

METHODS

We included 68 patients with narcolepsy type 1, 39 patients with other central disorders of hypersomnolence, and 43 healthy controls. A CBA and a conventional ELISA were used to detect anti-TRIB2 antibody levels in patients' sera.

RESULTS

CBA was used to detect serum anti-TRIB2 antibodies in Chinese patients with narcolepsy, and the results were negative. However, when the ELISA was used, only 2 patients with narcolepsy type 1 had TRIB2 antibody titers higher than the mean titer plus 2 standard deviations of the healthy controls.

CONCLUSIONS

In our study, ELISA identified TRIB2 autoantibodies in sera of patients with narcolepsy where CBA failed to demonstrate them. Contrary to our hypothesis, this intriguing finding deserves further research to elucidate the potential association between TRIB2 and narcolepsy type 1. Exploring the implications of TRIB2 autoantibodies in narcolepsy and disparate outcomes between ELISA and CBA could provide crucial insights.

CITATION

Zhong X, Yuan Y, Zhan Q, et al. Cell-based vs enzyme-linked immunosorbent assay for detection of anti-Tribbles homolog 2 autoantibodies in Chinese patients with narcolepsy. J Clin Sleep Med. 2024;20(6):941-946.

Neurosyphilis complicated by anti-γ-aminobutyric acid-B receptor encephalitis: A case report

BACKGROUND

Syphilis is an infectious disease caused by Treponema pallidum that can invade the central nervous system, causing encephalitis. Few cases of anti-N-methyl-D-aspartate receptor autoimmune encephalitis (AE) secondary to neurosyphilis have been reported. We report a neurosyphilis patient with anti-γ-aminobutyric acid-B receptor (GABABR) AE.

CASE SUMMARY

A young man in his 30s who presented with acute epileptic status was admitted to a local hospital. He was diagnosed with neurosyphilis, according to serum and cerebrospinal fluid (CSF) tests for syphilis. After 14 d of antiepileptic treatment and anti-Treponema pallidum therapy with penicillin, epilepsy was controlled but serious cognitive impairment, behavioral, and serious psychiatric symptoms were observed. He was then transferred to our hospital. The Mini-Mental State Examination (MMSE) crude test results showed only 2 points. Cranial magnetic resonance imaging revealed significant cerebral atrophy and multiple fluid-attenuated inversion recovery high signals in the white matter surrounding both lateral ventricles, left amygdala and bilateral thalami. Anti-GABABR antibodies were discovered in CSF (1:3.2) and serum (1:100). The patient was diagnosed with neurosyphilis complicated by anti-GABABR AE, and received methylprednisolone and penicillin. Following treatment, his mental symptoms were alleviated. Cognitive impairment was significantly improved, with a MMSE of 8 points. Serum anti-GABABR antibody titer decreased to 1:32. The patient received methylprednisolone and penicillin after discharge. Three months later, the patient's condition was stable, but the serum anti-GABABR antibody titer was 1:100.

CONCLUSION

This patient with neurosyphilis combined with anti-GABABR encephalitis benefited from immunotherapy.

A cell-based assay for detection of anti-fibrillarin autoantibodies with performance equivalent to immunoprecipitation

Anti-fibrillarin autoantibodies are useful for the diagnosis and prognosis of systemic sclerosis (SSc). Anti-fibrillarin produces a clumpy nucleolar pattern in indirect immunofluorescence assay on HEp-2 cells (HEp-2 IFA). Here we develop and validate a reliable cell-based anti-fibrillarin assay (Fibrillarin/CBA) for use in clinical diagnostic laboratories. A TransMembrane Signal was fused to the human fibrillarin gene (TMS-fibrillarin). HEp-2 cells overexpressing transgenic TMS-fibrillarin at the cytoplasmic membrane were used as IFA substrate in the Fibrillarin/CBA. Sixty-two serum samples with nucleolar pattern in the HEp-2 IFA (41 clumpy; 21 homogeneous/punctate) were tested for anti-fibrillarin using Fibrillarin/CBA, immunoprecipitation (IP), line-blot and ELISA. In addition, samples from 106 SSc-patients were evaluated with Fibrillarin/CBA and the results were correlated with disease phenotypes. Thirty-eight of 41 samples with the clumpy nucleolar pattern (92.7%) were positive in the Fibrillarin/CBA, while all 21 samples with other nucleolar patterns were negative. Fibrillarin/CBA results agreed 100% with IP results. Among the 38 Fibrillarin/CBA-positive samples, only 15 (39.5%) and 11 (29%) were positive for anti-fibrillarin in line-blot and ELISA, respectively. Higher frequency of diffuse cutaneous SSc (dcSSc) phenotype (72.7% vs 36.8%; p=0.022), cardiac involvement (36.4% vs 6.5%; p=0.001) and scleroderma renal crisis (18.2% vs 3.3% p = 0.028) was observed in SSc patients with positive compared to negative Fibrillarin/CBA result. Performance of Fibrillarin/CBA in the detection of anti-fibrillarin autoantibodies was comparable to the gold standard IP. Positive Fibrillarin/CBA results correlated with disease phenotypes known to be associated with anti-fibrillarin autoantibodies, underscoring the clinical validation of this novel assay.

Autoantibodies in central nervous system and neuromuscular autoimmune disorders: A narrative review

The discovery of novel autoantibodies in neurological disorders contributes to a better understanding of its pathogenesis, improves the accuracy of diagnosis, and leads to new treatment strategies. Advances in techniques for the screening and detection of autoantibodies have enabled the discovery of new antibodies in the central nervous system (CNS) and neuromuscular diseases. Cell-based assays using live or fixed cells overexpressing target antigens are widely used for autoantibody-based diagnosis in clinical practice. Common pathogenic autoantibodies are unknown in most patients with multiple sclerosis (MS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Novel pathogenic autoantibodies to aquaporin-4 and myelin oligodendrocyte glycoprotein (MOG) have been identified in neuromyelitis optica spectrum disorder and MOG antibody-associated disease, respectively. These diseases have clinical similarities to MS, but with the discovery of pathogenic autoantibodies, they are now recognized as distinct disease entities. Antibodies to paranodal membrane proteins such as neurofascin-155, contactin‑1, contactin‑associated protein‑1 in CIDP and muscle-specific kinase and low-density lipoprotein receptor–related protein 4 in myasthenia gravis were added to the profiles of autoantibodies in neurological disorders. Despite the relatively low frequency of seropositivity, autoantibody detection is currently essential for the clinical diagnosis of CNS and neuromuscular autoimmune disorders, and differential approaches to seropositive patients will contribute to more personalized medicine. We reviewed recent discoveries of autoantibodies and their clinical implications in CNS and neuromuscular disorders.

The frequencies of peripheral blood CD5+CD19+ B cells, CD3-CD16+CD56+ NK, and CD3+CD56+ NKT cells and serum interleukin-10 in patients with multiple sclerosis and neuromyelitis optica spectrum disorder

BACKGROUND

Multiple sclerosis (MS) and neuromyelitis optica syndrome disease (NMOSD) are inflammatory diseases of the central nervous system. The pathogenesis and treatments for these two conditions are very different. Natural killer (NK) and natural killer T (NKT) cells are immune cells with an important role in shaping the immune response. B cells are involved in antigen presentation as well as antibody and cytokine production. There is conflicting evidence of the roles of NK, NKT, and B cells in the two conditions. We aimed to compare the frequency of CD3-CD16+CD56+NK, CD3+ CD56+ NKT, and CD5+CD19+ B cells in the peripheral blood and serum Interleukin-10 (IL-10) in patients with MS and NMOSD.

METHODS

CD19+CD5+ B, CD3- CD16+CD56+ NK, and CD3+CD56+ NKT cells were quantitated by flow cytometry in 15 individuals with Interferon-Beta (IFN-β) treated relapsing-remitting MS (RRMS), 15 untreated RRMS, and 15 NMOSD patients as well as 30 healthy controls (HC). Serum IL-10 was measured using an enzyme-linked immunosorbent assay (ELISA).

RESULTS

The percentage of CD3-CD56+CD16+ NK cells in the peripheral blood of IFN-treated MS (1.81 ± 0.87) was significantly lower than for untreated RRMS (4.74 ± 1.80), NMOSD (4.64 ± 1.26) and HC (5.83 ± 2.19) (p < 0.0001). There were also differences for the percentage of CD3-CD16+ and CD3-CD56+ cells (p < 0.001 and p < 0.0007; respectively). IFN-treated RRMS (2.89 ± 1.51) had the lowest proportion of CD3+CD56+ among the study groups (p < 0.002). Untreated RRMS (5.56 ± 3.04) and NMOSD (5.47 ± 1.24) had higher levels of CD3+CD56+ than the HC (3.16 ± 1.98). The mean percentage of CD19+CD5+ B cells in the peripheral blood of untreated RRMS patients (1.32 ± 0.67) was higher compared to the patients with NMOSD (0.30 ± 0.20), HC (0.5 ± 0.22) and IFN-treated RRMS (0.81 ± 0.17) (p < 0.0001). Serum interleukin-10 was significantly higher in the IFN-treated RRMS (8.06 ± 5.39) and in HC (8.38 ± 2.84) compared to untreated RRMS (5.07 ± 1.44) and the patients with NMOSD (5.33 ± 2.56) (p < 0.003).

CONCLUSIONS

The lower proportion of CD3-CD56+ CD16+ NK and CD3+CD56+ cells in peripheral blood of IFN-treated RRMS compared to other groups suggests the importance of immunomodulation in patients with RRMS disorder. Based on the differences in CD19+CD5+ B cells and serum IL-10 between patients and HC, supplementary assessments could be of value in clarifying their roles in autoimmunity.

Improving laboratory diagnostics in myasthenia gravis

Introduction: Myasthenia gravis (MG) is a prototypical autoimmune disease, characterized by pathogenic autoantibodies targeting structures of the neuromuscular junction. Radioimmunoprecipitation assays (RIPAs) represent the gold standard for their detection. However, new methods are emerging to complement, or overcome RIPAs, also with the perspective of eliminating the use of radioactive reagents.Areas covered: We discuss advances in laboratory methods, prompted especially by cell-based assays (CBAs), for the detection of the autoantibodies of MG diagnostics, above all those to the nicotinic acetylcholine receptor (AChR), muscle-specific kinase (MuSK), and low molecular-weight receptor-related low-density lipoprotein-4 (LRP4).Expert opinion: CBA technology makes AChRs aggregate on cell membranes, thus allowing to detect autoantibodies to clustered AChRs, with reduction of seronegative MG cases. The diagnostic relevance of RIPA/CBA-measurable LRP4 antibodies is still unclear, in Caucasian patients at least. Live CBAs for the detection of AChR, MuSK, and LRP4 antibodies might represent an alternative to RIPAs, but first require full validation. CBAs could be used as screening tests, limiting RIPAs for antibody quantification. To this end, ELISAs might be an alternative.Fixation procedures preserving enough degree of antigen conformationality could yield AChR and MuSK CBAs suitable for a wide use in clinical-chemistry laboratories.

Detection of MOG-IgG in Clinical Samples by Live Cell-Based Assays: Performance of Immunofluorescence Microscopy and Flow Cytometry

Human antibodies against Myelin Oligodendrocyte Glycoprotein (MOG) from immunoglobulin-G subclasses (MOG-IgG) have been recently associated with a new subgroup of neurological autoimmune diseases with distinct clinical characteristics from multiple sclerosis and neuromyelitis optica spectrum disorders. The use of MOG-IgG as a biomarker is an essential tool to assist in the diagnosis and clinical prognosis. The cell-based assay (CBA) is a methodology that expresses high levels of natively folded human MOG protein in the cell membrane being the methodology most used for clinical MOG-IgG diagnosis. However, there is still no consensus about the best approach to perform CBA to improve the results. The CBA using flow cytometry (CBA-FC) is an automated technique with objective quantification, reducing the subject of human bias that occurred at CBA using immunofluorescence (CBA-IF). In this study, we compared the performance of CBA-IF and CBA-FC as an acquisition tool analysis. The sera of 104 patients diagnosed with inflammatory Central Nervous System diseases were tested in both CBA-IF and CBA-FC. We used the dilution of 1:128 for CBA-IF and three different dilutions (1:20, 1:100, and 1:640) for CBA-FC. The CBA-FC and CBA-IF results had 88.5% agreement between assays and the CBA-IF titers by endpoint-dilution correlated with the CBA-FC titers. The highest serum dilution resulted in an increased CBA-FC specificity, but there was a reduction in the CBA-FC sensitivity. Our study showed that CBA-FC can be used in clinical practice as a diagnostic technique for MOG-IgG. In addition, in some specific cases, the combination of both techniques could be used as a tool to discriminate unspecific binding and overcome single assay limitations.