The effect of immunomodulators on the immunogenicity of TNF-blocking therapeutic monoclonal antibodies: a review

Therapeutic monoclonal antibodies have revolutionized the treatment of various inflammatory diseases. Immunogenicity against these antibodies has been shown to be clinically important: it is associated with shorter response duration because of diminishing concentrations in the blood and with infusion reactions. Concomitant immunomodulators in the form of methotrexate or azathioprine reduced the immunogenicity of therapeutic antibodies in rheumatoid arthritis, Crohn disease, and juvenile idiopathic arthritis. The occurrence of adverse events does not increase when immunomodulators are added to therapeutic antibodies. The mechanism whereby methotrexate and azathioprine influence immunogenicity remains unclear. Evidence-based consensus on prescribing concomitant immunomodulators is needed

Large-Vessel Vasculitis:Interobserver Agreement and Diagnostic Accuracy of (18)F-FDG-PET/CT

Introduction. F-18-FDG-PET visualises inflammation. Both atherosclerosis and giant cell arteritis cause vascular inflammation, but distinguishing the two may be difficult. The goal of this study was to assess interobserver agreement and diagnostic accuracy of F-18-FDG-PET for the detection of large artery involvement in giant cell arteritis (GCA). Methods. 31 F-18-FDG-PET/CT scans were selected from 2 databases. Four observers assessed vascularwall F-18-FDGuptake, initially without and subsequently with predefined observer criteria (i.e., vascular wall F-18-FDG uptake compared to liver or femoral artery F-18-FDG uptake). External validation was performed by two additional observers. Sensitivity and specificity of F-18-FDG-PET were determined by comparing scan results to a consensus diagnosis. Results. The highest interobserver agreement (kappa: 0.96 in initial study and 0.79 in external validation) was observed when vascular wall F-18-FDG uptake higher than liver uptake was used as a diagnostic criterion, although agreement was also good without predefined criteria (kappa: 0.68 and 0.85). Sensitivity and specificity were comparable for these methods. The criterion of vascular wall F-18-FDG uptake equal to liver F-18-FDG uptake had low specificity. Conclusion. Standardization of image assessment for vascular wall F-18-FDG uptake promotes observer agreement, enables comparative studies, and does not appear to result in loss of diagnostic accuracy compared to nonstandardized assessment

Novel APC mutations in Czech and Slovak FAP families: clinical and genetic aspects

BACKGROUND: Germline mutations in the adenomatous polyposis gene (APC) result in familial adenomatous polyposis (FAP). FAP is an autosomal dominantly inherited disorder predisposing to colorectal cancer. Typical FAP is characterized by hundreds to thousands of colorectal adenomatous polyps and by several extracolonic manifestations. An attenuated form of polyposis (AFAP) is characterized by less than 100 adenomas and later onset of the disease. METHODS: Here, we analyzed the APC gene for germline mutations in 59 Czech and 15 Slovak FAP patients. In addition, 50 apparently APC mutation negative Czech probands and 3 probands of Slovak origin were screened for large deletions encompassing the APC gene. Mutation screening was performed using denaturing gradient gel electrophoresis and/or protein truncation test. DNA fragments showing an aberrant electrophoretic banding pattern were sequenced. Screening for large deletions was performed by multiplex ligation dependent probe amplification. The extent of deletions was analyzed using following microsatellite markers: D5S299, D5S82, D5S134 and D5S346. RESULTS: In the set of Czech and Slovak patients, we identified 46 germline mutations among 74 unrelated probands. Total mutation capture is 62,2% including large deletions. Thirty seven mutations were detected in 49 patients presenting a classical FAP phenotype (75,5%) and 9 mutations in 25 patients with attenuated FAP (36%). We report 20 novel germline APC mutations and 3 large deletions (6%) encompassing the whole-gene deletions and/or exon 14 deletion. In the patients with novel mutations, correlations of the mutation localization are discussed in context of the classical and/or attenuated phenotype of the disease. CONCLUSION: The results of the molecular genetic testing are used both in the establishment of the predictive diagnosis and in the clinical management of patients. In some cases this study has also shown the difficulty to classify clinically between the classical and the attenuated form of FAP according to the established criteria. Interfamilial and/or intrafamilial phenotype variability was also confirmed in some cases which did not fit well with predicted genotype-phenotype correlation. All these findings have to be taken into consideration both in the genetic counselling and in the patient care

The role of the codon and the initiation factor IF-2 in the selection of N-blocked aminoacyl-tRNA for initiation

Poly(uridylic acid) [poly(U)] and poly(xanthidylic acid) [poly(X)] strongly stimulate the IF-2-dependent binding of fMET-tRNA to 30-S ribosomal subunits from Escherichia coli [Van der Laken et al. (1979) FEBS Lett. 100, 230-234]. The N-formylmethionine moiety is incorporated into poly(phenylalanine) upon subsequent addition of other components required for protein synthesis when poly(U) is used as template. This paper shows that N-acetylated Phe-tRNAPhe (AcPhe-tRNA), but not Phe-tRNAPhe or tRNAPhe, competes with fMET-tRNA for binding to poly(U)-programmed 30-S ribosomal subunits. The two species of N-blocked aminoacyl-tRNA are bound to poly(U)-programmed and poly(X)-programmed 30-S subunits in a ratio that is linearly dependent on the ratio of the two species added. With poly(U) as template there is no apparent preference for either fMET-tRNA or AcPhe-tRNA, whereas with poly(X) there is a 2-3-fold preference for fMET-tRNA. The initiation factor IF-2, which is strictly required for the binding of N-blocked aminoacyl-tRNAs, has a higher affinity for fMET-tRNA than for AcPhe-tRNA. It is concluded that (a) interaction of the 30-S ribosomal subunit with poly(U) or poly(X) leads to IF-2-dependent binding of N-blocked aminoacyl-tRNA; (b) the initiation factor IF-2-discriminates in favour of fMET-TRNA; (c) the presence of the cognate codon discriminates in favour of the corresponding N-blocked aminoacyl-tRN

Promising potential of new generation translocator protein tracers providing enhanced contrast of arthritis imaging by positron emission tomography in a rat model of arthritis

INTRODUCTION: Early diagnosis of and subsequent monitoring of therapy for rheumatoid arthritis (RA) could benefit from detection of (sub)clinical synovitis. Imaging of (sub)clinical arthritis by targeting the translocator protein (TSPO) on activated macrophages is feasible using (R)-[(11)C] PK11195-based positron emission tomography (PET), but clinical applications are limited by background uptake in peri-articular bone/bone marrow. The purpose of the present study was to evaluate two other TSPO ligands with potentially lower background uptake in neurological studies, [(11)C]DPA-713 and [(18)F]DPA-714, in a rat model of arthritis. METHODS: TSPO binding of DPA-713, DPA-714 and PK11195 were assessed by in vitro competition studies with [(3)H]DPA-713 using human macrophage THP-1 cells and CD14(+) monocytes from healthy volunteers. In vivo studies were performed in rats with methylated bovine serum albumin-induced knee arthritis. Immunohistochemistry with anti-TSPO antibody was performed on paraffin-embedded sections. Rats were imaged with [(11)C]DPA-713 or [(18)F]DPA-714 PET, followed by ex vivo tissue distribution studies. Results were compared with those obtained with the tracer (R)-[(11)C]PK11195, the established ligand for TSPO. RESULTS: In THP-1 cells, relative TSPO binding of DPA-713 and DPA-714 were 7-fold and 25-fold higher, respectively, than in PK11195. Comparable results were observed in CD14(+) monocytes from healthy volunteers. In the arthritis rat model, immunohistochemistry confirmed the presence of TSPO-positive inflammatory cells in the arthritic knee. PET images showed that uptake of [(11)C]DPA-713 and [(18)F]DPA-714 in arthritic knees was significantly increased compared with contralateral knees and knees of normal rats. Uptake in arthritic knees could be largely blocked by an excess of PK11195. [(11)C]DPA-713 and [(18)F]DPA-714 provided improved contrast compared with (R)-[(11)C]PK11195, as was shown by significantly higher arthritic knee-to-bone ratios of [(11)C]DPA-713 (1.60 ± 0.31) and [(18)F]DPA-714 (1.55 ± 0.10) compared with (R)-[(11)C]PK11195 (1.14 ± 0.19). CONCLUSIONS: [(11)C]DPA-713 and [(18)F]DPA-714 clearly visualized arthritis and exhibited lower (peri-articular) bone/bone marrow uptake than (R)-[(11)C]PK11195. These features merit further investigation of these tracers for early diagnosis and therapy monitoring of RA in a clinical setting