[Correlation of acetylcholine receptor antibodies and clinical severity of myasthenia gravis in combined immunosuppressive therapy]

Acetylcholine Receptor Antibody Titers and Clinical Course after Influenza Vaccination in Patients with Myasthenia Gravis: A Double-Blind Randomized Controlled Trial (ProPATIent-Trial)

BACKGROUND

It is a continuous matter of discussion whether immune activation by vaccination in general and Influenza vaccination in particular increases the risk for clinical deterioration of autoimmune diseases. This prospective study investigated the serological and clinical course of autoimmune Myasthenia gravis (MG) after a seasonal influenza vaccination.

METHODS

This randomized, placebo-controlled, double-blind study enrolled MG patients with antibodies against acetylcholine-receptors (AChR-ab). They were allocated to receive seasonal influenza vaccine or placebo. The primary endpoint was the relative change of AChR-ab-titer over 12weeks. A relative increase of 20% was set as non-inferiority margin. Secondary endpoints were clinical changes in the modified Quantitative Myasthenia Gravis Score (QMG), increase of anti-influenza-ELISA-antibodies, and changes of treatment. The study is registered with Clinicaltrialsregister.eu, EudraCT number 2006-004374-27.

FINDINGS

62 patients were included. Mean±standard deviation (median) in the vaccine and placebo group were AChR-ab-titer changes of -6.0%±23.3% (-4.0%) and -2.8%±22.0% (-0.5%) and QMG score changes of -0.08±0.27 (0.17) and 0.11±0.31 (0.00), respectively. The difference between groups (Hodges-Lehmann estimate with 95% CI) was - for the AChR-ab-titer change 4·0% [-13.3%, 4.5%] (p=0.28 for testing a difference, p<0.0001 for testing non-inferiority) and for the QMG change 0·00 [-0.17, 0.00] (p=0.79 for testing a difference). The occurrence of 74 adverse events (AE) was comparable between groups. The most common AE was flu-like symptoms. One serious AE (hospitalisation following gastrointestinal haemorrhage) in the verum group was not related to the vaccine.

INTERPRETATION

Influenza vaccination in MG is safe. Uprating the potential risk of a severe course of MG exacerbation during influenza infection compared to the 95% CI differences for the endpoints, vaccination is principally indicated in this patient population.

Disturbed B cell subpopulations and increased plasma cells in myasthenia gravis patients

Whether there is a general perturbation of B and plasma cell subsets in myasthenia gravis (MG) has not been investigated so far. Here we performed a detailed flow cytometric analysis of blood and if available thymic tissue in order to detect MG-specific and therapy-induced changes. We observed significant differences in the distribution of B cell subsets in MG patients, yet these were mainly attributable to medical treatment. Furthermore MG is associated with significantly increased frequencies of plasma cells that were especially activated in purely ocular disease manifestation. In contrast to thymoma, B cell subset distribution in hyperplastic thymus could be distinguished from peripheral blood, however both tissues were not significantly enriched with plasma cells. Thus B cell differentiation in general is not defective in MG, but modified by therapy and enhanced frequencies of plasma cells can be detected in MG patients.

Ocular myasthenia gravis. A critical review of clinical and pathophysiological aspects

Myasthenia gravis (MG) is probably the best studied autoimmune disease caused by autoantibodies against the acetylcholine receptor (AChR) at the neuromuscular junction, subsequently leading to abnormal fatigability and weakness of skeletal muscle. Extraocular muscle weakness with droopy eyelids and double vision is present in about 90% of MG patients, being the initial complaint in about 50%. In approximately 20% of the patients the disease will always be confined to the extraocular muscles. The single most important diagnostic test is the detection of serum antibodies against AChR which is positive in 90% of patients with generalized MG, but only in 65% with purely ocular MG. Electromyographic studies and the Tensilon test are of diagnostic value in clear-cut cases, but may be equivocal in purely ocular myasthenia, especially the latter not rarely producing false-positive results. Treatment response to corticosteroids and anti-cholinesterase agents is satisfactory in many patients with ocular MG, however other immunosuppressive drugs may also be needed. Pathogenetically relevant steps of the underlying autoimmune process have been elucidated during the last few years; nevertheless a number of questions remain open, especially what starts off the autoimmune process, and why are eye muscles so frequently involved in MG?

Anti-acetylcholine receptor antibodies decrease after thymectomy in patients with myasthenia gravis. Clinical correlations

Clinical course and changes in serum levels of antibodies to the acetylcholine receptor (a-AChR) were followed in 82 patients with myasthenia gravis during a period of 1-8 years after thymectomy. Decrease in a-AChR immediately after thymectomy was influenced by changes in a total IgG. Immunosuppressive medication affected serum a-AChR at all points of time. In a subgroup of 41 patients without thymoma who had no immunosuppressive drugs, there was a steady decrease in a-AChR concomitant with clinical improvement from 6 weeks after thymectomy.