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Biomedical subjects

K Peerlinck

Publications and source records attributed to K Peerlinck.

At least 37 records · Page 2Linked to original sources
PubMed1998

Optimal care of inhibitor patients during surgery.

The care of haemophilia patients with high titre inhibitors during surgery has always been a formidable challenge. The introduction of recombinant activated factor VII (rFVIIa; NovoSeven, Novo Nordisk, Bagsvaerd, Denmark) appears to be a major breakthrough for the management of such patients. Administration of rFVIIa as a continuous infusion is a very attractive option and precludes the need for very frequent (2-h) injections due to the very short half-life of the product. Successful major surgery has been performed in patients with high titre inhibitors using continuous infusion of rFVIIa. Several questions remain, however, such as optimal therapeutic level, optimal monitoring, optimal prevention of thrombophlebitis at the injection site and the necessity for antifibrinolytic agents.

Antibodies↗
PubMed1998

Dominant C2 domain epitope specificity of inhibitor antibodies elicited by a heat pasteurized product, factor VIII CPS-P, in previously treated hemophilia A patients without inhibitors.

From June, 1990, to November, 1991, in The Netherlands and Belgium, 16 previously treated severe hemophilia A patients (PTP) developed inhibitors after exposure to factor VIII CPS-P, a new heat pasteurized product. A previously untreated patient (PUP) also developed an inhibitor to CPS-P. In inhibitor neutralization assays with recombinant fVIII C2 and A2 domain polypeptides, plasmas from 14 PTPs were > or = 79% neutralized by C2 and < 10% by A2, but the PUP plasma was partially neutralized by C2 (48%) and A2 (28%). Immunoprecipitation assays of the PTP and PUP plasmas with the fVIII heavy chain and with recombinant C2 and A3-C1 polypeptides confirmed that the C2 dominant immune response to CPS-P was found only in the PTPs. Competition of the binding of 2 inhibitors to 125I-CPS-P by unlabeled CPS-P and another plasma fVIII was similar, demonstrating that the antibody response was not directed to epitopes only present in CPS-P. We propose that the immunogenicity of the CPS-P C2 domain was altered by heat pasteurization.

Adolescent↗
PubMed1998

Anti-hepatitis G E2 antibody detection and its relation to serum HGV-RNA in patients with clotting disorders: high prevalence of HGV infection and spontaneous remission.

In a previous study, we have determined the prevalence of serum HGV-RNA in patients with congenital clotting disorders. Twenty-six (15%) of 175 patients investigated were serum HGV-RNA positive. In addition, HGV-RNA was detectable in peripheral blood mononuclear cells (PBMC) in ten percent of the cases, three of these patients were serum HGV-RNA negative. In the present study, we have determined the prevalence of anti-HGV-E2 antibodies in the same patient population. Anti-HGV-E2 as determined by ELISA was detected in 45 patients (25.7%). Forty of these patients were serum HGV-RNA negative. Ninety-two percent of the 26 HGV viremic patients and all but one patient (44 patients) with detectable anti-HGV-E2 had coinfection with the hepatitis C virus (HCV). Of these coinfected patients, 62.5% of HGV viremic patients and 53% of anti-HGV-E2 positive patients showed elevated serum ALT levels. Anti-HGV-E2 seroconversion is thus not associated with HCV infection. Two patients who were solely infected with HGV had normal serum ALT levels. In a retrospective longitudinal study, we have observed in 15 patients that serum HGV-RNA persisted during one to 19 years of follow-up, while anti-HGV-E2 was repeatedly negative. Five additional patients who were anti-HGV-E2 positive with concomitant detectable HGV-RNA (4 patients in serum and 1 patient in PBMC) became HGV-RNA negative during follow-up, ranging from 1 to 8 years after the first detection of anti-HGV-E2 antibodies. Two patients had lost anti-HGV-E2 antibodies 3 to 6 years after the seroconversion without the re-appearance of serum HGV-RNA. From these findings, it is clear that the prevalence rate of HGV infection in patients with clotting disorders as determined by PCR assay for HGV-RNA and anti-HGV-E2 by ELISA is actually higher than the prevalence of HGV viremia. Although HGV viremia may persist for longer than 19 years, most of the patients infected with HGV may clear the viremia spontaneously. The clearance of viremia is usually associated with seroconversion to anti-HGV-E2. In addition, anti-HGV-E2 may be lost during years of follow-up without the reappearance of the HGV-RNA. Although HGV infection does not seem to influence the fate of HCV infection and does not induce increased levels of serum ALT, the clinical significance of long-term infection remains to be established.

Adolescent↗
PubMed1998

The molecular basis of antithrombin deficiency in Belgian and Dutch families.

The molecular basis of hereditary antithrombin (AT) deficiency has been investigated in ten Belgian and three Dutch unrelated kindreds. Eleven of these families had a quantitative or type I AT deficiency, with a history of major venous thromboembolic events in different affected members. In the other two families a qualitative or type II AT deficiency was occasionally diagnosed. DNA studies of the AT gene were performed, using polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) analysis, followed by direct sequencing of the seven exons and intron-exon junction regions. Six novel point mutations were identified: four missense, one nonsense mutation and a single nucleotide deletion near the reactive site, causing a frameshift with premature translation termination. In two kindreds the underlying genetic defect was caused by a whole gene deletion, known as a rare cause of AT deficiency. In these cases, Southern blot and polymorphism analysis of different parts of the AT gene proved useful for diagnosis. In another kindred a partial gene deletion spanning 698 basepairs could precisely be determined to a part of intron 3B and exon 4. In two type I and in both type II AT deficient families a previously reported mutation was identified. In all cases, the affected individuals were heterozygous for the genetic defect.

Adolescent↗
PubMed1998

Experiences with continuous infusion of recombinant activated factor VII.

A questionnaire was sent to 28 haemophilia treatment centres known to have used recombinant activated factor VII (rFVIIa; NovoSeven, Novo Nordisk, Bagsvaerd, Denmark), to collect data on continuous infusion of this product. This mode of administration was recently introduced for rFVIIa but there are several questions which remain to be answered in order to optimize this technique. Of the 26 responding centres, 14 had used rFVIIa in continuous infusion for 40 treatment episodes over a total of 283 days. In most of the cases the treatment was targeted at a factor VII level of 10 IU/ml, monitored by the one-stage clotting assay. This seemed to be adequate for most of the haemorrhagic and surgical procedures. Pretreatment pharmacokinetic evaluation was performed in only a minority of the cases but is probably of great importance given the wide variation observed in the clearance values. A strategy was necessary to prevent local thrombophlebitis, at least for infusions in peripheral veins; parallel infusion of heparin, saline or dextrose-saline proved effective. The question of optimal monitoring needs further attention. Haemorrhagic complications were significantly less frequent when treatment was combined with the antifibrinolytic tranexamic acid.

Drug Monitoring↗
PubMed1997

Confirmatory strategy of hepatitis C serology based on two screening assays in a diagnostic setting.

One hundred ninety seven successive sera, positive for anti-hepatitis C virus antibody with a third generation screening enzyme immunoassay (MEIA on IMX, Abbott), were tested with alternative third generation screening assays from two different manufacturers (Sanofi and Ortho), with an immunoblot assay (RIBA 3.0, Chiron), and by reverse transcriptase polymerase chain reaction (RT-PCR). Samples positive by RIBA 3.0 or by RT-PCR were considered as true positives. The positive predictive value of a combination of strong positive results in two screening assays was more than 98%. This combination of results has the same predictive value for detectable viraemia as a positive RIBA 3.0 (86.5%). Using a policy of two successive enzyme immunoassays in this clinical diagnostic setting diminishes the need for supplemental assays by more than 85%.

Hepatitis C↗
PubMed1997

Factor VIII inhibitors in previously treated haemophilia A patients with a double virus-inactivated plasma derived factor VIII concentrate.

Antibodies to factor VIII (inhibitors) are usually produced at the beginning of treatment with factor VIII and are rare in multitransfused patients. Such antibodies are deemed to be patient-related, as supported by the description of a number of associated risk factors. However, a second category of inhibitors has recently been identified, namely antibodies occurring in multitransfused patients as a result of exposure to a particular factor VIII concentrate. A first outbreak of product-related inhibitors was recently described. The present paper describes the second well-documented occurrence of such inhibitors. Eight out of 140 multitransfused patients with severe haemophilia A developed an inhibitor to factor VIII shortly after changing treatment to a double-virus inactivated plasma-derived factor VIII concentrate. In addition to solvent-detergent treatment, this concentrate was pasteurised at 63 degrees C for 10 hours. Exposure to the pasteurised product before inhibitor detection ranged from 9 to 45 days. Inhibitor titers varied between 2.2 and 60 Bethesda Units and recovery of transfused factor VIII ranged from 0.21 to 0.68 (expressed as i.u./dl factor VIII rise per i.u./kg administered). In contrast to usual inhibitors in haemophilia A patients, these product-related inhibitors showed complex inhibition kinetics. They were found specific for the factor VIII light chain. The inhibitors gradually declined when exposure to the pasteurised product was stopped, despite further treatment with other factor VIII concentrates. The present data stress the importance of carefully monitored clinical studies, both in previously treated and previously untreated patients, before introduction of a new or modified clotting factor concentrate.

Adolescent↗
PubMed1997

Hepatitis G viral RNA in serum and in peripheral blood mononuclear cells and its relation to HCV-RNA in patients with clotting disorders.

The hepatitis G virus (HGV) has recently been identified as a new member of the Flaviviridae family. Infection by this virus is thought to be associated with blood borne hepatitis. In this study, the presence of HCV- and HGV-RNAs in serum or plasma (175 patients) and in peripheral blood mononuclear cells (PBMC) (133 patients) was investigated in patients with clotting disorders using a sensitive reverse transcriptase polymerase chain reaction (RT-PCR). HGV-RNA was detected in serum of 26 patients (14.8%). In apparently healthy blood donors, serum HGV-RNA was detected in 4 of 358 individuals investigated (1.12%). Ninety two percent of the 26 serum HGV-RNA positive patients had coinfection with the hepatitis C virus (HCV), especially with HCV genotype 1b, the most common genotype in Belgium. Of these coinfected patients, 15 (62.5%) showed elevated serum ALT levels. Two patients who were solely infected with HGV had normal serum ALT.HGV-RNA in PBMC was found in 18 patients, of whom 3 were negative for serum HGV-RNA. As in case of HCV, HGV-RNA in PBMC is preferentially sensitive to interferon treatment. Nevertheless, rapid reappearance of HGV-RNA in PBMC was observed after cessation of treatment. In one patient, persistent serum ALT elevation seems to be associated with continued HGV viremia, despite the disappearance of serum HCV-RNA.

Adolescent↗
PubMed1997

Restricted epitope specificity of anti-FVIII antibodies that appeared during a recent outbreak of inhibitors.

We recently described an outbreak of anti-factor VIII (FVIII) antibodies in a population of haemophilia A patients non-responsive to FVIII (1). To find out what part of the FVIII molecule had been altered, we purified specific anti-FVIII antibodies from the plasma of the five patients showing high titres of inhibitors. An average of 100 micrograms antibodies per ml of initial plasma was recovered by immunoadsorption on insolubilised FVIII. The antibodies followed the normal isotypic distribution, including the presence of specific IgG2 antibodies; the relative increase in IgG4 that is usually observed in patients with long-standing inhibitors, was not present. The regions of FVIII to which human antibodies bound were determined by a competition assay using a panel of murine monoclonal antibodies: two major regions were identified, one located in the A2 heavy chain domain, and the other made of determinants of both the A3 and C2 light chain domains. Affinity-purified antibodies inhibited the function of FVIII as determined in a chromogenic assay. However, variations existed in the affinities with which antibodies bound to soluble FVIII. This study shows that the immunogenicity of two particular regions of FVIII has been altered. A screening for alterations located in these two regions should possibly be included in the preclinical evaluation of FVIII concentrates.

Animals↗
PubMed1995

Factor VIII gene inversions in severe hemophilia A: results of an international consortium study.

Twenty-two molecular diagnostic laboratories from 14 countries participated in a consortium study to estimate the impact of Factor VIII gene inversions in severe hemophilia A. A total of 2,093 patients with severe hemophilia A were studied; of those, 740 (35%) had a type 1 (distal) factor VIII inversion, and 140 (7%) showed a type 2 (proximal) inversion. In 25 cases, the molecular analysis showed additional abnormal or polymorphic patterns. Ninety-eight percent of 532 mothers of patients with inversions were carriers of the abnormal factor VIII gene; when only mothers of nonfamilial cases were studied, 9 de novo inversions in maternal germ cells were observed among 225 cases (approximately 1 de novo maternal origin of the inversion in 25 mothers of sporadic cases). When the maternal grandparental origin was examined, the inversions occurred de novo in male germ cells in 69 cases and female germ cells in 1 case. The presence of factor VIII inversions is not a major predisposing factor for the development of factor VIII inhibitors; however, slightly more patients with severe hemophilia A and factor VIII inversions develop inhibitors (130 of 642 [20%]) than patients with severe hemophilia A without inversions (131 of 821 [16%]).

Blotting, Southern↗
PubMed1995

Promotion of binding of von Willebrand factor to platelet glycoprotein Ib by dimers of ristocetin.

In the absence of high shear forces, the in vitro binding of human von Willebrand factor (vWF) to its platelet receptor glycoprotein Ib (GPIb) can be promoted by two well-characterized mediators, botrocetin and ristocetin. Using purified vWF and GPIb, we have investigated the mechanisms by which ristocetin mediates this binding. Specific binding of vWF monomers to GPIb occurred with a 1:1 stoichiometry, but high-affinity binding required the participation of two ristocetin dimers. Binding was strongly dependent on pH and inhibited by low poly-L-lysine concentrations, indicating ristocetin-dependent charge neutralization during the interaction. With increasing ristocetin concentrations, vWF binding depended progressively less on the involvement of its A1 loop, which is compatible with a model in which the two ristocetin dimers bridge the vWF-GPIb complex on secondary sites. In agreement with this model, the ristocetin-dimer-promoted stabilization of vWF on GPIb was abolished by low concentrations of poly(Pro-Gly-Pro), which is known to complex ristocetin dimers. Mechanistic analysis of the inhibition of vWF binding by the recombinant vWF fragment Leu504-Ser728 (VCL), which covers the entire A1 loop, revealed an affinity of VCL for GPIb comparable with that of the botrocetin-vWF complex for GPIb, and identified a specific but 20-fold lower affinity of VCL in the presence of ristocetin. The proline-rich peptides flanking the vWF A1 loop, Cys474-Val489 and Leu694-Asp709, inhibited vWF binding semispecifically by competitively interfering with the formation of the GPIb-vWF complex rather than by complexation of free ristocetin dimers. In conclusion, ristocetin-promoted binding of vWF to its GPIb receptor results from charge neutralization and interactions involving proline residues in the vicinity of the natural interaction sites present on both GPIb and the A1 domain of vWF.

Amino Acid Sequence↗
PubMed1995

Hepatitis C virus genotypes in Belgian hemophiliacs.

Hemophiliacs who have been exposed to unheated and/or dry heated pooled clotting factor concentrates are at a high risk of chronic hepatitis C. Serum HCV-RNA was measured by reverse transcriptase-polymerase chain reaction (RT-PCR) technique in 58 hemophiliacs positive for anti-HCV antibodies, HCV-RNA was detected in 55 patients. Based on the results of PCR positivity, HCV genotyping was carried out using genotype specific probes and the dot blot hybridization assay: 2 patients were found to be infected with type 1a (3.6%), 31 patients with type 1b (56.4%), 8 patients with type 2 (14.6%), 6 patients with type 3 (10.9%), 1 patient with type 4, and 7 patients with double infection (12.7%). As compared to a control group of 105 nonhemophilia patients with chronic hepatitis C, HCV genotype 1b was found predominant in both groups. However, double infection with two HCV types as well as a relatively high prevalence of infection with type 2 and type 3 were found in hemophiliacs.

Adolescent↗
PubMed1994

Molecular basis for type 1 antithrombin deficiency: identification of two novel point mutations and evidence for a de novo splice site mutation.

Inherited type 1 antithrombin (AT) deficiency is characterized by a reduction in both immunologically and functionally detectable protein. The disorder is associated with a high risk of thromboembolic disease. We have investigated the molecular basis of type 1 AT deficiency in three unrelated families. We have used the polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) analysis, followed by direct sequencing of the seven exons and the intron-exon junctions of the AT gene. Two novel point mutations were identified. A T to C single-base substitution was found in codon 421 in exon 6 (nucleotide position 13380), leading to an AT 421 isoleucine to threonine substitution. In another kindred, one of three Cs at nucleotide (nt) positions 5448 to 5450 in exon 3A (codon 151 or 152) was deleted, resulting in a frameshift mutation and predicting premature termination of protein translation at codon 251. In a third family, a previously reported G to A substitution, at nt position 9788 in intron 4, 14 bp in front of exon 5, was found. We have demonstrated the creation of a de novo exon 5 splice site by ectopic transcript analysis of lymphocyte mRNA. In all cases, the affected individuals were heterozygous for the mutation and no variant AT protein was detected.

Adolescent↗
PubMed1994

Hepatitis C virus-RNAs in plasma and in peripheral blood mononuclear cells of hemophiliacs with chronic hepatitis C: evidence for viral replication in peripheral blood mononuclear cells.

Hemophiliacs who have been exposed to unheated and/or dry heated pooled clotting factor concentrates are at high risk of chronic hepatitis C. Although the mechanism and site of hepatitis C virus (HCV) replication are not yet known, HCV is thought to replicate through a complementary negative RNA strand, as has been shown for flaviviruses. The detection of negative RNA strands has therefore been regarded as a marker of replication. We investigated the prevalence of HCV-RNA and of negative HCV-RNA strands in peripheral blood mononuclear cells (PBMC) and plasma of hemophiliacs. Forty-three of 47 patients studied (91%) had anti-HCV antibodies and in 36 patients HCV-RNA was detectable in PBMC. In one group of 20 patients negative HCV-RNA strands were present in PBMC and 10 of these patients also had negative HCV-RNA strands in plasma. In another group of nine patients HCV-RNA was detected in PBMC, although cDNA synthesis was carried out in the absence of primers. Only in two of these nine patients negative and positive HCV-RNA strands were demonstrated specifically in PBMC using a modified reverse transcription step. If the presence of negative HCV-RNA strands can be considered as marker of viral replication, the findings indicate that HCV can replicate in PBMC. Furthermore, in certain patients it is impossible to use the currently available technique to detect selectively positive or negative HCV-RNA strands.

Adolescent↗
PubMed1994

Pharmacokinetics and pharmacodynamics of MK-383, a selective non-peptide platelet glycoprotein-IIb/IIIa receptor antagonist, in healthy men.

MK-383 (L-tyrosine, N-(n-butylsulfonyl)-O-[4-butyl(4-piperidinyl)], monohydrochloride monohydrate) is a potent and specific platelet fibrinogen receptor antagonist that may be useful in preventing processes that lead to occlusive thrombus formation in the lumen of the blood vessel. Two placebo-controlled phase I trials were completed in 56 healthy volunteers to investigate the safety, tolerability, pharmacokinetics, and pharmacodynamics of MK-383 administered as 1- and 4-hour infusions in the presence and absence of aspirin. When administered to healthy male subjects by constant infusions up to 0.4 microgram/kg/min over 1 hour or up to 0.2 microgram/min over 4 hours, it provided a well-tolerated reversible means of inhibiting platelet function. At infusion rates of 0.25 and 0.15 microgram/kg/min for 1 and 4 hours, respectively, MK-383 extended baseline bleeding time by 2.0- to 2.5-fold and inhibited adenosine diphosphate (ADP)-induced platelet aggregation by at least 80%. The pharmacokinetics of MK-383 include a mean plasma clearance of 329 ml/min, steady-state volume of distribution of 76 L, and half-life of 1.6 hours. The percentage of dose excreted in the urine was 37%. Correlations between MK-383 plasma concentration (C) and inhibition of platelet aggregation were examined by fitting with a sigmoid maximum-effect model. The plasma concentration yielding 50% inhibition (C50) for MK-383 in healthy volunteers is approximately 13 ng/ml, with a Hill coefficient > 5. Based on a naive pooled analysis, an exponential empirical model best describes the MK-383 C-extension of template bleeding time (BTE) relationship. The model indicates that the MK-383 plasma concentration necessary to double BTE is approximately 30 ng/ml (i.e., 2.5-fold greater than the C50 for ADP-induced inhibition of platelet aggregation). The pharmacokinetics of MK-383 was unaffected by pretreatment with 325 mg aspirin 1 day before and 1 hour before infusion. Conversely, aspirin pretreatment reduced C50 and increased bleeding time extension, suggesting that aspirin may have an additive effect with respect to inhibition of platelet function. Based on the putative role of the fibrinogen receptor in thrombotic processes and an acceptable human pharmacokinetic-pharmacodynamic profile, MK-383 should be evaluated in patients with unstable angina.

Analysis of Variance↗
PubMed1994

Rapid clearance of hepatitis C virus RNA in peripheral blood mononuclear cells of patients with clotting disorders and chronic hepatitis C treated with alpha-2b interferon is not a predictor for sustained response to treatment.

Thirteen patients with congenital coagulation disorders and chronic hepatitis C were treated with alpha-interferon (IFN). Serum transaminases (ALT) and hepatitis C virus (HCV)-RNA in plasma and peripheral blood mononuclear cells (PBMC) were followed during and after treatment. During IFN treatment ALT levels normalized in 8/13 patients. In all patients HCV-RNA disappeared from PBMC. In 9/13 HCV-RNA also became undetectable from plasma; in six of these nine this occurred earlier in PBMC than in plasma; in the remaining three the disappearance of HCV-RNA occurred simultaneously in plasma and PBMC. All but two patients relapsed within 3 weeks after cessation of IFN, one relapsed after 6 weeks and one patient remains in remission after 6 months. HCV-RNA reappeared either earlier in plasma (3/12) or simultaneously in plasma and PBMC (9/12). Viral replication in PBMC thus can easily be suppressed by IFN, whereas longer treatment is needed for the eradication of HCV-RNA in plasma. The detection of HCV-RNA in PBMC cannot be used as a prognostic marker for the identification of patients with chronic hepatitis C who will have a sustained response to IFN treatment.

Adult↗