A simplified ELISA for anti-receptor antibodies in myasthenia gravis

A Simple, Rapid and Non-Radiolabeled Immune Assay to Detect Anti-AChR Antibodies in Myasthenia Gravis

OBJECTIVE

To assess the practicality of dot-blot testing for rapid and sensitive detection of the antiacetylcholine receptor (anti-AChR) antibodies in myasthenia gravis (MG).

METHODS

In this case-control study, we tested serum specimens of 85 patients with MG, 85 healthy control individuals, and 85 patients without MG who have other autoimmune and neurological illnesses. All the serum specimens were tested for anti-AChR antibodies using 3 assays: in-house enzyme-linked immunosorbent assay (ELISA), the dot-blot assay, and commercial ELISA.

RESULTS

In-house ELISA, commercial ELISA, and dot-blot test results were positive for anti-AChR antibodies in 65 (76.5%) patients with MG. The results of all 3 tests were negative for anti-AChR antibodies in healthy controls and patients without MG. We observed perfect concordance (K = 1, P <.001) between all 3 tests. In-house ELISA correlated significantly (r = 0.873, P <.001) with commercial ELISA. In-house ELISA and the dot-blot test demonstrated similar diagnostic performance in detecting anti-AChR antibodies.

CONCLUSIONS

The dot-blot assay is a simple, nonradioactive immune assay for rapid detection of anti-AChR antibodies in MG.

Diagnosis of myasthenia gravis: Comparison of anti-nicotinic acetyl choline receptor antibodies, repetitive nerve stimulation and Neostigmine tests at a tertiary neuro care centre in India, a ten year study

Anti-nicotinic AChR antibodies (Anti-nAChR antibodies), Repetitive Nerve Stimulation (RNS) and Neostigmine test are used for diagnosis of myasthenia gravis (MG). We compared their diagnostic agreement in a cohort of 486 MG patients over a period of ten years. Anti-nAChR antibodies, RNS and Neostigmine test showed positivity of 57.36%, 51.78%, and 93.4% respectively in ocular myasthenia and 93.77%, 82.35%, and 97.92% respectively in generalized myasthenia group. Neostigmine test showed higher positivity than anti-nAChR antibodies and RNS test in both groups. A marginal to fair agreement was observed between these tests highlighting their significance in the diagnosis of the disease.

Presynaptic membrane receptor in human brain

Myasthenia gravis (MG) is an autoimmune disease that results from antibody mediated damage of Acetylcholine receptor (AChR) at the neuromuscular junction. The autoimmune character of MG and pathogenic role of AChR antibodies have been established by several workers i.e., the demonstration of anti-AChR antibodies in about 90 % of MG patients. It has been demonstrated that patients with MG also have antibodies against a second protein named presynaptic membrane receptor (PsmR), which is identified by utilizing β-Bgtx, a ligand which binds to PsmR. Using β-Bgtx Sepharose 4B affinity matrix, the PsmR was purified from different regions of human cadaver brain by affinity chromatography. Purified receptor was characterized both by biochemical and immunological procedures. PsmR purified from different regions of the brain shows a specific activity of 0.37 ± 0.01, 0.39 ± 0.02 and 0.43 ± 0.005 nM/ μg of protein in Parietal lobe, Occipital lobe and Frontal lobe respectively. The affinity purified PsmR from the brain of 87 and 68 kd (parietal lobe, occipital lobe and frontal lobe) shows immunoreactivity with myasthenic sera. These findings suggest that PsmR from brain is another antigen against which autoantibodies are developed in Myasthenia gravis patients. Upon treatment with various enzymes we concluded that PsmR from brain is a glycoprotein in which the immunoreactivity resides in the carbohydrate as well as the peptide epitopes. In conclusion the PsmR is another antigen against which autoantibodies are formed in different regions of brain. These can be used as a diagnostic tool for detecting antibodies in the sera or cerebrospinal fluid of MG patients.

Myasthenia gravis and acetylcholine receptor antibodies: a clinico immunological correlative study on South Indian patients

Acquired myasthenia Gravis (MG), a disorder of impaired neuromuscular transmission is recognized as an autoimmune disorder, with a majority of the patients having antibodies against acetylcholine receptor (AChR antibodies) in the serum.

A non-radioactive receptor assay for snake venom postsynaptic neurotoxins

A non-radioactive assay was developed for detecting the binding of postsynaptic neurotoxins to acetylcholine receptor (AchR) from Torpedo californica. Enzyme linked immunosorbent assay (ELISA) wells coated with long or short chain neurotoxins specifically bound to purified AchR while crotamine or two different cardiotoxins did not. Bound receptor was detected by antibody against AchR. Specificity was determined by dose-response experiments and competition studies using carbamylcholine chloride, acetylcholine chloride, or Naja naja atra cobrotoxin mixed with receptor.