Genetic risk factors in patients with Myasthenia gravis

Myasthenia gravis (MG) is a rare autoimmune disease mediated by antibodies against components of the neuromuscular junction, particularly the acetylcholine receptor (AChR). The prevalence of MG in Belgrade has been estimated at 189 cases per 1,000,000 inhabitants, which is among the highest prevalence reported to date. Genetic studies have mainly pointed to specific HLA alleles associated with MG. However, CTLA-4 and TNFRSF11A, playing a role in the immune response, have recently been associated with MG in genome-wide association studies. Since CTLA-4 and TNFRSF11A promote other autoimmune diseases, the main objective of this casecontrol study was to determine the association between these candidate genes and the risk for developing MG in Serbian population. Genotyping of rs231735 and rs231770 within the CTLA-4 gene and rs4263037 within TNFRSF11A in 447 AChR-MG patients and 447 individually sex- and age-matched controls revealed no association with MG (p=0.344, p=0.923 and p=0.557, respectively). However, when stratifying patients into those with early-onset (n=183) and late-onset MG (n=264), we found an association of minor rs231735 allele T with early-onset MG under the recessive genetic model (OR=0.548, 95% CI=0.339-0.888, p=0.014, p10e6 permutation=0.014). Haplotype analysis revealed that individuals with the GC haplotype rs231735-rs231770 had a higher risk for developing earlyonset MG (OR =1.360, p=0.027, p10e6 permutation =0.027). Considering the sufficient statistical power of the study (>90%) and the selection criteria for controls, our results suggest that the CTLA-4 may be associated with early-onset MG in Serbian population. Analysis of additional variants is needed to understand the association of CTLA-4 with MGBOOK OF ABSTRACTS: 8th CONGRESS OF SERBIAN NEUROSCIENCE SOCIETY with international participation 31 May – 2 June 2023. Belgrade, Serbi

The role of molecular mimicry in the etiology of Guillain Barré Syndrome

Molecular mimicry between host tissue structures and microbial components has been proposed as the pathogenic mechanism for triggeringof autoimmune diseases by preceding infection. Recent studies stated that molecular mimicry as the causative mechanism remains unproven for most of the human diseases. Still, in the case of the peripheral neuropathy Guillain-Barré syndrome (GBS) this hypothesis is supported by abundant experimental evidence. GBS is the most frequent cause of acute neuromuscular paralysis and in some cases occurs after infection with Campylobacter jejuni (C. jejuni). Epidemiological studies, showed that more than one third of GBS patients had antecedent C. jejuni infection and that only specific C. jejuni serotypes are associated with development of GBS. The molecular mimicry between the human gangliosides and the core oligosaccharides of bacterial lipopolysaccharides (LPSs) presumably results in production of antiganglioside cross-reactive antibodies which are likely to be a contributory factor in the induction and pathogenesis of GBS. Antiganglioside antibodies were found in the sera from patients with GBS and by sensitization of rabbits with gangliosides and C. jejuni LPSs animal disease models of GBS were established. GBS as prototype of post-infection immune-mediated disease probably will provide the first verification that an autoimmune disease can be triggered by molecular mimicry

Changes in thymopoiesis in myasthenia gravis

This study was undertaken to investigate T-cell maturation ill hyperplastic thymi of patients suffering from myasthenia gravis (MG). For this purpose, the expression of the major differentiational molecules (CD4, CD8, and CD3/TCRalphass) and that of the regulator. v and activation molecules oil thymocytes from MG patients and control subjects were estimated by flow cytometric analysis. In the MG patients the increase in relative proportion of immature (CD4-8- TCRalphass-) and the most mature (CD4+8- TCRalphass(high) and CD4-8- TCRhigh encompassing immunoregulatory NKT) thymocytes followed by a decrease in that of CD4+8+CD3 /TCRalphass- cells was found. Furthermore, in these patients the relative proportion of CD4+HLA-DR+ and CD4+71+ cells was increased, whereas that of CD4+25+ cells was slightly, but significantly, decreased (reflecting, most likely, decreased contribution of T reg cells bearing this phenotype). Moreover. in MG thymi the percentage of CD45RA+ cells was reduced indicating changes in the selection processes. In keeping with this finding the reduced thymocyte apoptotic index and percentage of cells bearing apoptosing (CD4-8- TCRalphass(low)) phenotype were detected. In conclusion, the study demonstrates substantial changes in intrathymic differentiation of T cells in hyperplastic MG thymi and suggests alterations in selection events providing an increased escape of potentially? autoreactive T-cell clones, on one side, and all altered maturation and/or selection of immunoregulatory cells (NKT and CD4+8-25+ T reg cells) keeping these cell clones under control, on the other side

Paratopic specificity of two human monoclonal immunoglobulins M expressing Y7 idiotype

We have already characterized Y7 idiotype as natural idiotype by showing its expression on IgM molecules derived form cord sera. The aim of this study was to investigate the binding properties of two human monoclonal IgM antibodies isolated from the sera of patients with Waldenstrom macroglobulinaemia, which express Y7 idiotype. In order to estimate the binding repertoire of these two IgM molecules (IgM DJ and IgM RD) we tested the isolated IgM molecules and their F(ab)2 and Fab fragments over the panel of 23 different protein and non-protein antigens, nine different bacterial strains and cell membranes from neuronal and epithelial tissues. These tests were performed by means of direct and competitive ELISA, immunoblot and immunofluorescence assays. Both antibodies reacted with ssDNA, oligonucleotide fragments, and lactobacteria. IgM DJ showed reactivity with myelin associated glycoprotein (MAG) and blood vessel endothelial cells. Binding for DNA oligonucleotide fragments and lactobacteria was interrupted up to 70% with 0.5 M NaCl, which indicated that these interactions were of low affinity. Avidity dependent binding was also evidenced by use of F(ab)2 fragments. Determined characteristics such as polyreactivity which included autoantigens, low affinity and avidity dependent binding, qualified these two monoclonal IgM as natural autoantibodies. Expression of natural idiotype Y7 on two immunoglobulins M,which possessed natural autoantibody properties, indicated the connection of natural autoantibody specificity and the natural idiotype expression and suggested the involvement of network interactions in selection of malignant B cell clones

The effect of benfothiamine in the therapy of diabetic polyneuropathy

Introduction. Diabetic polyneuropathy (DPN) is one of the most common diabetic complications, which can result in a significant functional impairment and reduction of the quality of life in affected individuals. It occurs due to alterations in different biochemical mechanisms which require the presence of thiamine, which is why this vitamin is used in the therapy of DPN. Due to the low bioavailability of the hydrosolubile forms of thiamine, its liposolubile preparations (benfotiamine) are preferentially used. Objective. The aim of this study was to determine the efficacy of benfotiamine in combination with vitamin B6 in the therapy of DPN. Methods. The study group comprised of 22 patients with DPN who were treated with the combination of benfotiamine and vitamin B6 during 45 days. The effect of the therapy was evaluated by the analysis of different clinical, laboratory and electrophysiological parameters before and after conducted treatment. Results. After the treatment period, a statistically highly significant reduction of pain (p<0.01) was noted with the reduction of pain score on visual analogue scale in 86.4% of patients. A significant reduction of subjective complaints was also noted, with decreased modified total symptom score in 95.5% of patients (p<0.01). The presence of alodynia was reported at the beginning of the study in 77.3%, and after the benfotiamine therapy only in 22.7% of patients, while hyperpathy was initially present in 90.9%, and after treatment in 31.8% of patients (p<0,01). Neurophysiological parameters of polyneuropathy also significantly improved, with the improvement of the compound muscle action potential amplitude in 68.2% (p<0.01) and motor conduction velocity of the peroneal nerve in 45.5% of patients (p<0.01). The improvement of the sensory nerve action potential amplitude (p<0.01) and sensory conduction velocity (p=0.05) of the sural nerve was found in 45.5% of patients. After the treatment period, there was a highly statistically significant lowering of the glycosylated haemoglobin (p<0.01), with improved findings in 63.6% of patients. After completed study treatment protocol 86.4% of patients rated their overall condition as improved. Conclusion. Our results showed that the conducted treatment resulted in significant subjective and objective improvement of the disease signs symptoms, which confirmed that benfotiamine was good starting choice for the treatment of diabetic polyneuropathy