A routine assay for the direct analysis of HLA-DR-related shared epitope and B27 alleles in chronic inflammatory arthritis.

Knowledge of the genetic background of patients with inflammatory arthritis may be useful for disease management. The main markers are the HLA-DR-associated Shared Epitope (SE) for Rheumatoid Arthritis (RA) and HLA-B27 for ankylosing spondylitis. We have developed a simple molecular biology-based test to provide this essential information. HLA targets are amplified by polymerase chain reaction (PCR), then simultaneously analyzed using 16 individual hybridization reactions in two 8-well ELISA strips with colorimetric detection. Concordance was evaluated using a cohort of RA patients with known genotype. Using this new assay, 100% concordance was observed with conventional genotyping in RA patients both for HLA-DR SE and B27 genotypes. Seventy-three percent of the patients with destructive RA had at least one susceptible allele within SE, compared to 38% of those patients with non-destructive disease. This new assay, which requires minute amount of blood, could be used to determine the genetic background of inflammatory arthritis, particularly in non-specialized settings and for large-scale clinical trials.

Evaluation of a new automated ELISA test for von Willebrand factor using two monoclonal antibodies.

A new automated quantitative enzyme linked immunosorbent assay (ELISA) for the detection of human von Willebrand factor (vWF), VIDAS vWF, has been developed for use on the VIDAS analyser (bioMérieux). The two-step capture/tag test relies on two monoclonal antibodies (mAbs), the second one being labelled with alkaline phosphatase. The lower limit of detection of the assay is < 1 IU/dl, and the upper limit of detection is 120 IU/dl. There is no hook effect for concentrations up to 1100 IU/dl. Intra- and inter-assay precision ranges from 3% and 5%. Assays are performed preferentially using citrated plasma and in these conditions the 95% confidence intervals for normal values are 52-154 IU/dl and 60-200 IU/dl for O blood group and non-O blood group subjects, respectively. Using the lower limits of the normal range as the cut-off level, all patients tested with type 1 (n = 29) or 3 (n = 2) von Willebrand disease (vWD) would be accurately classified with the new ELISA. Comparing the VIDAS test with a conventional ELISA gave a good correlation and comparable results with type 1 and 3 vWD patients (n = 31; r = 0.99; y = 0.99x + 0.24), type 2A and 2B vWD patients (n = 20; r = 0.99; y = 1.05x-1.65) and normal subjects (n = 204; r = 0.94; y = 1.06x-2.6).

High-risk genotype for type 1 diabetes: a new simple microtiter plate-based ELOSA assay.

The main contribution to genetic susceptibility for type 1 diabetes (T1D) is conferred by the HLA class II genes, with a major involvement of the DQB1*02 and 0302 alleles. The aim of our study was to develop a simple and rapid method suitable for identifying individuals with an HLA-associated T1D risk using whole blood as a source of DNA and reverse hybridization on microtiter plates (ELOSA). DNA was extracted from whole blood using various extraction methods. The PCR-amplified second exon of the DQB1 gene was hybridized at 37 degrees C for 1 hr to a set of 11 capture probes immobilized on a microtiter plate (eight-well strip per test) and corresponding to T1D susceptibility (S), protection (P), or neutral (N) alleles. Colorimetric analysis was then performed using specific oligonucleotides coupled to horseradish peroxidase and OrthoPhenyl Peroxidase (OPD) substrate. DNA samples corresponding to French (Rhône-Alpes area) T1D patients (n = 128) have been genotyped with the HLA-T1D prototype. A strong correlation is observed between susceptible genotypes and the disease, because 92.2% of the T1D individuals screened have at least one susceptible allele (DQB1*02 or *0302), thereby strengthening interest in analyzing DQB1 alleles as HLA-linked T1D markers in our Rhône-Alpes area population. Interestingly, clear T1D-associated genotyping results have been observed when using DNA samples extracted from dried blood spots, making it possible to envisage such genotyping in geographically dispersed affected families, for large-scale newborn screening, and for the inclusion of high-risk patients in clinical trials aimed at preventing the disease.

Polymorphisms in the 5' regulatory region of the tissue factor gene and the risk of myocardial infarction and venous thromboembolism: the ECTIM and PATHROS studies. Etude Cas-Témoins de l'Infarctus du Myocarde. Paris Thrombosis case-control Study.

Tissue factor (TF) is a transmembrane protein considered to be responsible for the initiation of coagulation. TF gene expression may be induced in monocytes and endothelial cells and is present in atherosclerotic plaque to initiate thrombus formation. To investigate whether individual differences in TF gene expression could predispose subjects to thrombosis, we sequenced the 5' domain of the gene up to nucleotide 2732 and found 6 different polymorphisms: 4 of them were completely concordant and defined 2 haplotypes with similar frequencies, designated as 1208 D and 1208 I. Genotyping of patients with myocardial infarction in a case-control study involving 2354 subjects showed no association between the polymorphisms and nonfatal coronary thrombosis. In another study involving 255 patients with venous thromboembolism and 1204 controls, allele D was less common in the cases (P=0.022). The odds ratio associated with the presence of at least 1 D allele was 0.72 (P=0. 031). Comparison of subgroups of control subjects who were homozygous for the D or I allele demonstrated a lower plasma TF concentration in DD homozygotes. These results indicate that the TF gene promoter exists in 2 major forms differing at 4 sites. The 1208 D haplotype is not associated with coronary thrombosis but is associated with reduced plasma TF levels and a lower risk of venous thrombosis.