Polyspecificity of antimicrosomal thyroid antibodies in hepatitis C virus-related infection.

OBJECTIVES: The outcome of dysthyroidism and the presence of antithyroid antibodies in patients with chronic hepatitis C virus (HCV) infection receiving interferon-alpha therapy is clearly established. However, the prevalence and the specificity of antithyroid antibodies in HCV patients before interferon-alpha therapy remain controversial. The aim of the present study is to clarify within a large population of HCV patients the prevalence of antithyroid antibodies before interferon-alpha therapy and to determine whether their immunodominant antigen is the same as described in autoimmune thyroiditis. METHODS: Sera from 99 patients with chronic hepatitis C before (n = 99) and after (n = 37) interferon-alpha treatment were investigated for the presence of antimicrosomal and antithyroperoxidase antibodies assessed by indirect immunofluorescence and ELISA, respectively. Dot blotting on human thyroid lysate was designed to further characterize these autoantibodies. Data were compared to those obtained with sera of patients with autoimmune thyroiditis (n = 75) and healthy subjects (n = 96). RESULTS: In HCV patients, antimicrosomal antibodies were found with a higher proportion before interferon-alpha therapy (12.1%) than after therapy (8%). Thyroperoxidase constitutes the main antigen in only 4% before treatment, a prevalence similar to that observed in healthy controls. CONCLUSIONS: The prevalence of antithyroid antibodies is low in patients with chronic hepatitis C before interferon-alpha therapy. Thyroperoxidase may not be their main target. Further studies are required to determine whether HCV infection leads to a breakdown of tolerance to a thyroid self-protein other than thyroperoxidase.

The Pseudomonas syringae Hrp pathogenicity island has a tripartite mosaic structure composed of a cluster of type III secretion genes bounded by exchangeable effector and conserved effector loci that contribute to parasitic fitness and pathogenicity in plants.

The plant pathogenic bacterium Pseudomonas syringae is divided into pathovars differing in host specificity, with P. syringae pv. syringae (Psy) and P. syringae pv. tomato (Pto) representing particularly divergent pathovars. P. syringae hrp/hrc genes encode a type III protein secretion system that appears to translocate Avr and Hop effector proteins into plant cells. DNA sequence analysis of the hrp/hrc regions in Psy 61, Psy B728a, and Pto DC3000 has revealed a Hrp pathogenicity island (Pai) with a tripartite mosaic structure. The hrp/hrc gene cluster is conserved in all three strains and is flanked by a unique exchangeable effector locus (EEL) and a conserved effector locus (CEL). The EELs begin 3 nt downstream of the stop codon of hrpK and end, after 2.5-7.3 kb of dissimilar intervening DNA with tRNA(Leu)-queA-tgt sequences that are also found in Pseudomonas aeruginosa but without linkage to any Hrp Pai sequences. The EELs encode diverse putative effectors, including HopPsyA (HrmA) in Psy 61 and proteins similar to AvrPphE and the AvrB/AvrC/AvrPphC and AvrBsT/AvrRxv/YopJ protein families in Psy B728a. The EELs also contain mobile genetic element sequences and have a G + C content significantly lower than the rest of the Hrp Pai or the P. syringae genome. The CEL carries at least seven ORFs that are conserved between Psy B728a and Pto DC3000. Deletion of the Pto DC3000 EEL slightly reduces bacterial growth in tomato, whereas deletion of a large portion of the CEL strongly reduces growth and abolishes pathogenicity in tomato.

[Comparison of indirect immunofluorescence on Crithidia luciliae of Farr test, and immunoenzymatic methods for the screening of anti-native DNA autoantibodies]. / Comparaison de l'immunofluorescence indirecte sur Crithidia luciliae du test de Farr, et des méthodes immunoenzymatiques pour le dépistage des autoanticorps anti-ADN natif.

Anti-native DNA (ds DNA) antibodies were measured by the Farr assay, an indirect immunofluorescence on Crithidia luciliae (IIFCL) and a newly commercialised enzyme-linked immunosorbent assay (Elisa) in the sera of 270 patients: 73 negative controls, 67 patients with systemic lupus erythematosus (SLE), 73 with clinical symptoms of another connective tissue disease and 61 patients with liver diseases. The Farr assay remains a reliable method, IIFCL seems to be as specific but less sensitive and Elisa has a higher sensitivity but a lower specificity. Finally, 35 sera from the 270 patients were tested for anti-ds DNA antibodies using two other commercialised Elisa-related techniques. The results suggest little correlation between the three Elisa methods.

[Evaluation of a radioimmunologic technique for the detection of anti-native DNA antibodies]. / Evaluation d'une technique radio-immunologique pour la détection des anticorps anti-ADN natif.

The anti-native DNA antibodies were measured by a radioimmunoassay (RIA) type Farr assay in the sera from 648 patients: 108 with active or inactive systemic lupus erythematosus (SLE), 181 with clinical symptoms of another connective tissue disease, 171 with liver diseases, 29 with different pathology and 159 normal sera were obtained from a blood bank. The anti-DNA kit has been calibrated against the first international units/ml. This assay has proved to be sensitive and specific, and appears to be reliable for the diagnosis and follow-up of SLE patients. The authors propose a new reference cut-off level higher than producer's one.