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Biomedical subjects

R Schwaab

Publications and source records attributed to R Schwaab.

At least 37 records · Page 2Linked to original sources
PubMed2000

NovoSeven in immune tolerance therapy.

The development of inhibitors in haemophilia patients is one of the most serious challenges to effective treatment. The effect of factor (F) concentrate and treatment regimen on titre levels was studied in nine patients with haemophilia A or B and inhibitors. Patients with haemophilia A were subdivided into those treated with recombinant activated factor VII (rFVIIa) on demand or those treated prophylactically with activated prothrombin complex concentrate (aPCC) and rFVIIa. A third group comprised haemophilia B patients receiving rFVIIa prophylaxis and on-demand aPCC or rFVIIa. On-demand therapy with rFVIIa proved to be effective and safe treatment for acute bleeding episodes in haemophilic patients. In group 1, inhibitor titres decreased markedly 0.5-21 months prior to immune tolerance therapy (ITT) and remained low for a further 1-19 months. However, use of rFVIIa instead of aPCC as prophylactic treatment in group 2 patients undergoing ITT failed to show favourable results for rFVIIa. This may be due to the short half-life of rFVIIa (2.3-2.9 h). The data presented suggest that exclusive use of rFVIIa in acute bleeding episodes prior to commencing ITT is an effective method of decreasing inhibitor titre, thereby optimizing conditions for ITT.

Adolescent↗
PubMed2000

Molecular genetics in haemophilia A.

Efficient mutation screening methods have greatly facilitated the analysis of the factor VIII gene. The fast growing number of identified mutations has led to an increasing understanding of the genetics in haemophilia A. In combination with the recently generated molecular models of the factor VIII protein systematic studies of structural-functional relationships of the factor VIII protein have started. The knowledge of the causative gene defect has also become an important instrument in haemophilia care with respect to prediction of the patients' clinical course and safe genetic counselling of relatives.

Factor VIII↗
PubMed2000

Antibodies to factor VIII in hemophilia A patients.

Inhibitor development represents the main complication in the treatment of haemophilia A. The risk of inhibitor formation is in part genetically determined by the type of the underlying factor VIII gene lesion but environmental factors may also play an important role. Due to the lack of efficiency of factor VIII in these patients other therapeutic agents must be used for the treatment of bleedings, however, none is as effective as factor VIII in a non-inhibitor patient. Therefore, the eridication of the inhibitor through immune tolerance therapy is the treatment of choice. Centralized national and international immune tolerance registries have collected the results and show cost effectiveness of this treatment.

Factor VIII↗
PubMed2000

Congenital deficiency of vitamin K dependent coagulation factors in two families presents as a genetic defect of the vitamin K-epoxide-reductase-complex.

Hereditary combined deficiency of the vitamin K dependent coagulation factors is a rare bleeding disorder. To date, only eleven families have been reported in the literature. The phenotype varies considerably with respect to bleeding tendency, response to vitamin K substitution and the presence of skeletal abnormalities, suggesting genetic heterogeneity. In only two of the reported families the cause of the disease has been elucidated as either a defect in the gamma-carboxylase enzyme (1) or in a protein of the vitamin K 2,3-epoxide reductase (VKOR) complex (2). Here we present a detailed phenotypic description of two new families with an autosomal recessive deficiency of all vitamin K dependent coagulation factors. In both families offspring had experienced severe or even fatal perinatal intracerebral haemorrhage. The affected children exhibit a mild deficiency of the vitamin K dependent coagulation factors that could be completely corrected by oral substitution of vitamin K. Sequencing and haplotype analysis excluded a defect within the gamma-carboxylase gene. The finding of highly increased amounts of vitamin K epoxide in all affected members of both families indicated a defect in a protein of the VKOR-multienzyme-complex. Further genetic analysis of such families will provide the basis for a more detailed understanding of the structure-function relation of the enzymes involved in vitamin K metabolism.

Blood Coagulation Factors↗
PubMed2000

Risk factors for inhibitor development in hemophilia A.

The development of anti-factor-VIII-antibodies represents the most serious complication of factor VIII concentrate therapy, affecting about 30% of patients with severe hemophilia A. The genetics of the patients, comprising the factor VIII gene mutation and the immune response genes (MHC), have been shown to influence the risk of inhibitor formation. Severe molecular defects within the factor VIII gene, such as intron 22 inversions, nonsense mutations and large deletions, are associated with a 7 to 10 times higher inhibitor prevalence than less severe molecular gene defects such as missense mutations. Unexpectedly, frame shift deletions within runs of adenine nucleotides showed a low inhibitor risk, although most of them result in a stop codon. The explanation of this phenomenon is the restoration of the reading frame in some factor VIII molecules by slippage errors of the polymerase enzymes. Within most mutation types subgroups with significantly different inhibitor risks can be defined, e.g. multi domain vs. single domain large deletions, yielding a total of 10 groups with different risks of inhibitor formation. Alleles of MHC class II genes showed a less impressive influence on inhibitor development. In two studies of patients with a homogenous factor VIII gene mutation, the alleles DQA0102, DQB0602 and DR15 occurred more frequently in patients with inhibitor than without inhibitor (relative risks ranging from 1.9 to 4.0) and therefore could be assigned as risk alleles. Inflammatory processes in early childhood are under discussion as being an environmental influence factor that may modify the immune response to a foreign antigen. Fixing the genetic predisposition by gene analysis will be one important tool in the future to assess further parameters that might influence inhibitor formation.

Genetic Predisposition to Disease↗
PubMed1999

Analysis of expression kinetics and activity of a new B-domain truncated and full-length FVIII protein in three different cell lines.

Transient expression of full-length wild-type (wt) and a new B-domain truncated (deltaB) FVIII has been investigated in three eukaryotic cell lines (HEK-293, COS, CHO). When expressed in CHO cells, both FVIII proteins reached the same peak antigen levels, whereas in HEK-293 and COS cells those of FVIII/deltaB were up to sixfold those of FVIII/wt. Investigation of specific activity of the recombinant FVIII proteins using a chromogenic and a one-stage assay in addition to the FVIII-antigen ELISA revealed large variations: In HEK-293 cells specific activity of FVIII/deltaB measured with both assays was higher than that of FVIII/wt. In COS cells specific activity of both FVIII proteins was higher measured in the one-stage assay than in the chromogenic assay. In CHO cells both FVIII proteins had similar specific activity in each assay. In summary, expression kinetics and specific activity of conditioned medium vary depending on cell type used.

Animals↗
PubMed1999

Highly sensitive and species-specific assay for quantification of human transgene expression levels.

During the past few years great efforts have been made to construct and to test human factor VIII (hFVIII) and IX (hFIX) vectors suitable for haemophilia gene therapy in vivo. However, little is known about the molecular mechanisms of persistence and shut-off of transgene expression in the target organs after gene transfer using recombinant adenoviral vectors. To evaluate low transgene mRNA levels in different tissues, especially at long times after the gene transfer, the common northern blot method is often not sensitive enough. For this reason we developed a new, highly sensitive and species-specific method for hFIX mRNA quantification and employed it in mice treated with an adenoviral vector (Ad5CMVFIX) expressing human FIX. In addition to its very high sensitivity (lowest detection level=1 fg RNA), the method was shown to be strictly species-specific, since hFIX mRNA signals were never detected in untreated mice. In a long-term study of 18 vector-treated mice we compared the human FIX:Ag levels in the mouse plasma, the human FIX mRNA levels and human FIX vector DNA concentrations in the mouse liver. We found that a slow but continuous decrease of hFIX:Ag levels in mouse plasma was associated with a corresponding decrease of hFIX mRNA levels in the liver. However, the Ad5CMVFIX vector DNA levels did not decrease to a comparable degree, suggesting that the decrease of human FIX:Ag levels in mouse plasma is, to a significant extent, also caused by CMV promotor shut-off and only to a minor degree by loss of vector DNA.

Adenoviridae↗
PubMed1999

Induction of immune tolerance in haemophilia A inhibitor patients by the 'Bonn Protocol': predictive parameter for therapy duration and outcome.

The treatment of inhibitors is one of the most challenging fields in haemophilia care. The present study reports the results of 60 haemophilia A inhibitor patients treated according to the 'Bonn Protocol' and evaluates predictors for the duration and outcome of therapy. Successful immune tolerance could be achieved in 52 patients (86.7%) while the therapy failed in eight patients (13.3%). The immune tolerance achieved was longlasting in all 52 patients, with no inhibitor relapse in up to 20-years follow-up. The course of ITT was influenced by several factors. Interruptions of treatment during the ITT course led to a substantial prolongation of ITT duration (median 39.9 months vs 14.1 months in continuously treated patients). Infections of intravenous central lines appeared to be frequently coincided with ITT prolongation and sometimes even ITT failure. Further negative predictors towards the ITT duration were high inhibitor titres at enrollment or during ITT. There was also a tendency towards longer ITT duration in patients exhibiting the prevalent intron 22 inversion. As a consequence of our data treatment interruptions and infections of intravenous central lines should be avoided during the course of ITT. Furthermore our data suggest, that ITT should be started at low inhibitor titres preferably with a high factor VIII dosage protocol.

Blood Coagulation Factors↗
PubMed1999

Allelic discrimination of factor V Leiden using a 5' nuclease assay.

The G1691A (Leiden) mutation of the factor V gene is the most prevalent identified cause of venous thrombosis. Therefore, we developed a new genetic test using the TaqMan system. With this assay which combines PCR amplification and detection reaction in one closed tube, a cohort of 234 patients with a history of thrombosis was screened. In parallel, amplification products of the same patients were screened with a previously described test using endonuclease digestion of PCR products followed by gel electrophoresis. Identical results were obtained by both methods. Among cases, 122 (52%) individuals were homozygous normal, 99 (42%) were heterozygous affected and 13 (5.5%) showed homozygous pattern for the Factor V Leiden mutation. Thus, it could be demonstrated that the new TaqMan assay is a robust, rapid and automated method for high throughput application which avoids time consuming and difficult post-PCR steps.

Alleles↗
PubMed1998

Expression of CYP19 (aromatase) mRNA in the human temporal lobe.

The conversion of androgens to estrogens by CYP19 (cytochrome P450AROM, aromatase) is an important step in the mechanism of androgen action in the brain. CYP19 expression has been demonstrated in various animal species, but studies in human postnatal brain tissue are lacking. Therefore, we investigated CYP19 mRNA expression in human temporal lobe tissues. We studied biopsy materials removed at neurosurgery from 34 women, 32 men and 10 children with temporal lobe epilepsy. Quantification of CYP19 mRNA was achieved by nested competitive reverse transcription-PCR. CYP19 mRNA concentrations did not differ significantly between women (2.6 +/- 0.6 arbitrary units, aU; mean +/- SEM) and men (1.6 +/- 0.3 aU) nor between cerebral cortex tissue (2.0 +/- 0.4 aU) and subcortical white matter tissue of adults (2.4 +/- 0.7 aU), but they were significantly lower in cerebral cortex specimens of children (0.9 +/- 0.6 aU) than in those of adults (p < 0.02). In conclusion, CYP19 mRNA is expressed in the temporal lobe of children and adults. CYP19 mRNA concentrations are significantly lower in specimens of children than in those of adults.

Adult↗
PubMed1998

Haemophilia B: database of point mutations and short additions and deletions--eighth edition.

The eighth edition of the haemophilia B database (http://www.umds.ac. uk/molgen/haemBdatabase.htm ) lists in an easily accessible form all known factor IX mutations due to small changes (base substitutions and short additions and/or deletions of <30 bp) identified in haemophilia B patients. The 1713 patient entries are ordered by the nucleotide number of their mutation. Where known, details are given on: factor IX activity, factor IX antigen in circulation, presence of inhibitor and origin of mutation. References to published mutations are given and the laboratories generating the data are indicated.

Computer Communication Networks↗
PubMed1998

Immune tolerance induction: a role for recombinant activated factor VII (rFVIIa)?

The development of factor VIII (FVIII) and FIX inhibitors is one of the most serious complications of repeated transfusions in patients with haemophilia. Management of patients with haemophilia with inhibitors must be separated into 2 concepts: the control of acute bleeding episodes and, in the long term, the treatment of the inhibitor itself. This paper will discuss both aspects of the management of these patients, focusing in particular on the therapeutic options available for the treatment of bleeding episodes during immune tolerance induction (ITI) therapy. The second part of the paper will review the management and outcomes of 10 patients with severe haemophilia in whom recombinant activated FVII (rFVIIa: NovoSeven, Novo Nordisk, Bagsvaerd, Denmark) has been used to treat bleeding episodes in the Haemophilia Centre at Bonn University; 6 patients were treated with rFVIIa for bleeding episodes while undergoing ITI. The results obtained demonstrate that rFVIIa is a safe and effective treatment for bleeding episodes and haemostatic cover for surgical procedures in patients with inhibitors. Inhibitor titres were not boosted in patients with haemophilia and inhibitors on treatment with rFVIIa. Therefore, rFVIIa is also a suitable treatment for bleeding episodes or control of haemostasis during surgery in patients prior to initiation of ITI therapy.

Antibodies↗
PubMed1997

Haemophilia B: database of point mutations and short additions and deletions, 7th edition.

The seventh edition of the haemophilia B database lists in easily accessible form all known factor IX mutations due to small changes (base substitutions and short additions and/or deletions of <30 bp) identified in haemophilia B patients. The 1535 patient entries are ordered by the nucleotide number of their mutation. Where known, details are given on: factor IX activity, factor IX antigen in circulation, presence of inhibitor and origin of mutation. References to published mutations are given and the laboratories generating the data are indicated.

Databases, Factual↗