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C A Ludlam

Publications and source records attributed to C A Ludlam.

At least 73 records · Page 4Linked to original sources
PubMed1997

Recombinant coagulation factors.

The advent of technology that has allowed production of recombinant proteins on an industrial scale has revolutionized haemophilia care. Recombinant coagulation factors, as opposed to their plasma-derived counterparts, have a very low risk for transmission of infectious agents and their use should eradicate the threat of infection from viruses such as hepatitis C and the human immunodeficiency virus. This review outlines the manufacturing process involved in the production of the recombinant coagulation factors and the trials to date that have been performed to establish their safety and efficacy. We also discuss some of the issues involved in the change to use of recombinant coagulation factors, such as viral safety and potential immunogenicity.

Blood Coagulation Factors↗
PubMed1997

Human parvovirus B19 and blood products.

BACKGROUND AND OBJECTIVES: Human B19 parvovirus (B19), identified in 1975, was only recognised as the causative agent of fifth disease in 1983. The incidence of viraemia is low, around 1 in 1,000, but is sufficient to ensure that most plasma pools for fractionation contain some virus. While infection usually occurs in childhood and is benign, chronic infection sometimes occurs and may be of concern in certain patient groups. MATERIALS AND METHODS: This review is based on a meeting held in March 1995, and addresses recent concerns regarding the potential transmission of B19 infection by pooled plasma products. RESULTS: Recent data on the pathophysiology and assay of this virus are summarised along with possible approaches to donor screening, product screening, and virus removal. Only five cases of symptomatic infection have been reported in persons with haemophilia, but no technology for virus removal is established, and infection may be of concern in pregnant women, and in patients with enhanced red cell turnover or who are immunosuppressed, including those infected with human immunodeficiency virus, but only rarely in immunocompetent patients. CONCLUSIONS: For the future, well-validated assays relevant to virus infectivity are required if blood donations, plasma pools, or plasma products are to be screened, and an in-process virus inactivation step for B19 would be highly desirable. In the interim, non-plasma or recombinant products or a selective transfusion policy might be used in patient groups in which B19 infection is of particular concern. Further clinical data on the prognosis and impact of B19 infection are needed to justify both such policies and the future adoption of new technologies designed to reduce any excess B19 infectivity arising from transfused products.

Female↗
PubMed1997

Discrimination of hepatitis G virus/GBV-C geographical variants by analysis of the 5' non-coding region.

We have investigated the ability of different subgenomic fragments to reproduce the phylogenetic relationships observed between six complete genome sequences of GBV-C/hepatitis G virus (HGV). While similar relationships were observed following analysis of part of the 5' non-coding region (5'NCR), for the coding region they were not accurately reproduced for some large fragments or for the majority of fragments of 300 or 600 nucleotides. Analysis of 5'NCR sequences from a large number of isolates, including newly obtained sequences from Pakistan, Zaïre and Scotland, produced separate groupings of Asian, African and European/North American variants. These groupings are associated with specific polymorphisms in the 5'NCR, many of which were covariant and consistent with a proposed secondary structure for this region. The relatively low level of amino acid sequence variation observed between these geographically and phylogenetically defined groups of variants suggests that they are unlikely to display significant biological differences.

Base Sequence↗
PubMed1997

Viral safety of plasma-derived factor VIII and IX concentrates.

Treatment, or prevention, of bleeding in severe haemophilia requires lifelong therapy with repeated injections of factor VIII/IX concentrate which carry a risk of viral infection. The overall safety of all blood products depends not only upon careful donor selection and the screening of donations for infectious viruses, but also on the efficacy of specific anti-viral steps in the manufacturing process. As a result of the episodes of virus transmission by currently available concentrates there have been calls for all manufacturing processes to include two viral inactivation procedures. There have been no clinical studies, however, to demonstrate that these products have enhanced viral safety. A variety of other virucidal techniques are under evaluation. The way forward may be a form of post-marketing surveillance or pharmacovigilance in which large numbers of haemophiliacs are routinely screened for known transmissible viruses and the data systematically collected. It would probably be necessary to have a multinational arrangement because of the rarity of the transmission episodes. Such a system could also provide quick early warning of a difficulty with an individual product.

Drug Contamination↗
PubMed1997

An in vivo model for the assessment of acute fibrinolytic capacity of the endothelium.

The effects on blood flow and plasma fibrinolytic and coagulation parameters of intraarterial substance P, an endothelium dependent vasodilator, and sodium nitroprusside, a control endothelium independent vasodilator, were studied in the human forearm circulation. At subsystemic locally active doses, both substance P (2-8 pmol/min) and sodium nitroprusside (2-8 microg/min) caused dose-dependent vasodilatation (p <0.001 for both) without affecting plasma concentrations of PAI-1, von Willebrand factor antigen or factor VIII:C activity. Substance P caused local increases in t-PA antigen and activity (p <0.001) in the infused arm while sodium nitroprusside did not. At higher doses, substance P increased blood flow and t-PA concentrations in the noninfused arm. We conclude that brief, locally active and subsystemic infusions of intraarterial substance P cause a rapid and substantial local release of t-PA which appear to act via a flow and nitric oxide independent mechanism. This model should provide a useful and selective method of assessing the in vivo capacity of the forearm endothelium to release t-PA acutely.

Adult↗
PubMed1997

The treatment of bleeding in acquired haemophilia with recombinant factor VIIa: a multicentre study.

Recombinant factor VIIa was used to treat 38 patients with acquired haemophilia participating in the Novoseven compassionate-use program. 19 were male, median age 59, range 2-89 years. The median pre-treatment anti-human (H) and anti-porcine (P) inhibitor titre was H 43 BU/ml (range 1-4500) and P 4.5 BU/ml (range 0-1600). Recombinant factor VIIIa was used as first-line therapy for 14 bleeding episodes and as salvage-therapy for 60 episodes which failed to respond to blood-product therapy given for a median of four days (range 1-21 days) prior to treatment with rVIIa. Pre-rVIIa treatment was not reported for four episodes. The indications for treatment were 7 haemarthroses, 40 muscle haematomas, 20 urinary or GI haemorrhages and 3 surgical interventions. The median starting dose of rVIIa was 90.4 microg/kg (range 45-181). A median of 28 doses (range 1-541) were given per episode, over a median 3.9 days (range 0-43). Efficacy was assessed clinically 8 and 24 h after the start of rVIIa and at the end of treatment. A good response was obtained in all 14 bleeds for which rVIIIa was used as first-line therapy. The response after 24 h of rVIIa salvage-therapy for 60 bleeds was good in 75%, partial in 17% and poor in 8%. Efficacy was unreported in 4 cases. The median prothrombin time (PTT) shortened from 12 s (range 9.3-20) pre-treatment to 8.8 s (range 6-14) during treatment. The clinical response did not correlate with the dose of rVIIa used, the type of bleed or the degree of shortening of the PTT following rVIIa infusion. Three patients died from haemorrhagic complications of acquired haemophilia. This mortality of 7.9% is lower than previously reported for this condition. Although one patient developed DIC during treatment with rVIIa, this was probably attributable to hypovolaemic shock, massive transfusion and the use of PCCs. This study demonstrates that rVIIa is a safe, useful and effective treatment for bleeding in patients with acquired haemophilia.

Adolescent↗
PubMed1996

Infection with hepatitis G virus among recipients of plasma products.

BACKGROUND: Hepatitis G virus (HGV or GBV-C) is a newly discovered human flavivirus distantly related to hepatitis C virus (HCV). Little information is available on its natural history or routes of transmission, although it can be transmitted parenterally. We investigated the prevalence of persistent infection of HGV and HCV in patients exposed to non-virus-inactivated pooled blood products associated with transmission of HCV. METHODS: RNA was extracted from the plasma of 112 patients with haemophilia and 57 with hypogammaglobulinaemia, as well as from 64 different batches of archived coagulation-factor concentrates and immunoglobulins. RNA was reverse transcribed and amplified with primers from the 5' non-coding region of HCV and HGV by a nested polymerase chain reaction (PCR). Viral RNA was quantified by titration of complementary DNA before amplification. FINDINGS: Among non-renumerated UK blood donors HGV infection (detected by PCR) was more common than HCV infection (four [3.2%] of 125 compared with 137 [0.076%] of 180658 in southeast Scotland). Testing of batches of factor VIII and factor IX concentrates prepared without viral inactivation procedures showed high frequencies of contamination with HGV (16 of 17 factor VIII batches positive; six of six factor IX batches positive), with no difference between renumerated and non-renumerated donors. However, among 95 haemophiliacs who had received non-virus-inactivated concentrates, 13 (14%) were positive for HGV compared with 79 (83%) who were positive for HCV. Two of 37 recipients of long-term immunoglobulin replacement therapy were positive for HGV. Virus inactivation of blood products substantially reduced or eliminated contamination by HGV RNA sequences. INTERPRETATION: Despite the extremely high level of HGV contamination of non-virus-inactivated blood products, their use was not associated with high rates of persistent infection in recipients. The infectivity of HGV in blood products may be lower than that of HCV, or the virus may be less able to establish persistent infection in humans. Whatever the case, the high prevalence of active HGV infection in the general population remains difficult to explain.

Agammaglobulinemia↗
PubMed1996

Evolution of zidovudine resistance-associated genotypes in human immunodeficiency virus type 1-infected patients.

Substantial differences have been described in the response of individual patients to zidovudine (ZDV) therapy, both in the clinical impact and in virus load. Genotypic changes associated with the appearance of drug resistance may also be different or occur at different rates. We have obtained the nucleotide sequence of the RT domain of individual HIV-1 genomes extracted from 10 plasma and peripheral blood mononuclear cell (PBMC) samples donated by two haemophiliac patients before, during, and after long-term ZDV therapy. Although the plasma virus load was similar throughout, the order and timing of appearance of resistance-associated substitutions differed in the two patients. In patient p74, K70R appeared after 4 months, T215Y at 5.5 months, and M41L at 13 months. In p87, K70R also appeared at 4 months, but T215Y and K219Q were not observed until 18 months and M41L not at all. Much greater sequence change overall occurred in p74. The evolution of the viral population in that patient was dominated by the unique appearance of T215Y and subsequently M41L, with all sequences from the last time point being descended by a single path from the pretreatment samples. However, in p87, several different lineages of RT sequences were found to persist throughout treatment. We propose that these differences in outcome may be determined by differences in genetic background at sites other than the five generally considered to be associated with ZDV sensitivity.

Amino Acid Sequence↗
PubMed1996

Investigation of the relative infectivity and pathogenicity of different hepatitis C virus genotypes in hemophiliacs.

To assess the relative infectivity and pathogenicity of variants of hepatitis C virus (HCV) genotypes, the distribution of genotypes in hemophilic patients who had been treated with nonvirally inactivated factor concentrates or cryoprecipitates prepared from local blood donors was compared with those found in the respective blood donor populations. Genotype frequencies differed markedly in the four countries investigated (Scotland, Hungary, South Africa, and Thailand) but in each, the HCV genotype distributions in hemophiliacs and blood donors were similar. In addition, HCV genotypes in recipients of commercially manufactured concentrates were similar to those found in the US general population. These findings provide no evidence that HCV genotypes differ significantly from each other in replication rate, transmissibility, or infectivity.

Hemophilia A↗
PubMed1996

Interferon treatment for chronic hepatitis C infection in hemophiliacs--influence of virus load, genotype, and liver pathology on response.

In this study, we assessed the effectiveness of interferon treatment in 31 hemophiliacs with chronic hepatitis C virus (HCV) infection. Interferon alfa-2a (3 MU three times weekly) was administered for 6 months. Response was assessed by both serial alanine transaminase (ALT) and HCV RNA levels measured by a sensitive semiquantitative polymerase chain reaction (PCR) method. HCV genotype was determined by restriction fragment length polymorphism (RFLP), and evidence of changing genotypes during interferon therapy was sought. Severity of liver disease was assessed by both noninvasive and invasive methods, including laparoscopic liver inspection and biopsy. Sustained normalization of ALT levels occurred in eight patients (28%), and seven (24%) became nonviremic as assessed by PCR (<80 HCV/mL). Responders universally cleared HCV RNA within 2 months of starting interferon. Genotype 3a was associated with a favorable response to interferon. No evidence was found for a change in circulating genotype in patients who failed to respond to interferon or who relapsed. This study confirms that response rates to interferon are low in hemophiliacs as compared with other groups with chronic HCV infection. We have also demonstrated that virus load measurement over the first 8 to 12 weeks of treatment is an extremely useful method to identify responders at an early stage.

Adolescent↗
PubMed1996

Investigation of chronic hepatitis C infection in individuals with haemophilia: assessment of invasive and non-invasive methods.

Hepatitis C virus (HCV) infection is the major cause of chronic liver disease in individuals with haemophilia. A wide spectrum of disease severity is found in this group, ranging from mild hepatitis to cirrhosis. We have studied a cohort of 87 anti-HCV positive haemophiliacs who have been infected with HCV for 10-25 years and assessed the relative value of invasive and non-invasive methods of evaluating liver disease. The severity of liver disease was assessed using ultrasound scan (n = 77), upper GI endoscopy (n = 50), laparoscopic liver inspection (n = 33) and liver biopsy (n = 22). Invasive investigations were performed without any significant bleeding complications. Evidence of severe liver disease was found in approximately 25% of patients. There was agreement between the severity of liver histology and the information derived from the laparoscopic liver inspection, endoscopy and ultrasound in 86%. Co-infection with HIV was significantly associated with more severe liver disease (P = 0.006). This study provides further evidence that liver disease is emerging as a major complication in haemophiliacs and severe liver disease is more common in those co-infected with HIV. We have shown the potential value of laparoscopic liver inspection, in combination with endoscopy and ultrasound, in staging the extent of liver disease, and suggest that most patients may be managed without resorting to liver biopsy.

Adolescent↗
PubMed1996

Development of anti-interferon antibodies and breakthrough hepatitis during treatment for HCV infection in haemophiliacs.

The development of anti-interferon antibodies may lead to treatment failure during interferon therapy. We have studied the development of such antibodies in a group of 39 haemophiliacs receiving interferon-alpha 2a for chronic hepatitis C virus (HCV) infection. Anti-interferon antibodies developed in five (13%) patients and were associated with "breakthrough hepatitis' in three cases. There was an association between the development of anti-interferon antibodies and infection with HCV genotype 3a (P = 0.01). This study suggests that the development of anti-interferon antibodies may lead to treatment failure in a proportion of haemophiliacs with HCV infection. The association with genotype 3a has not previously been reported. Monitoring for the development of breakthrough hepatitis due to anti-interferon antibodies may provide the opportunity to develop strategies to overcome their effects.

Adolescent↗
PubMed1996

Measurement of platelet volume using a variety of different anticoagulant and antiplatelet mixtures.

Mean platelet volume (MPV), a measure of platelet size, has previously been noted to change in a time dependent manner in ethylene-diaminetetraacetic acid (EDTA) and citrate anticoagulants. We measured MPV in healthy volunteers using several different anticoagulants and at different temperatures. In ten volunteers MPV was measured (Sysmex NE 8000 autoanalyser) serially over a 29 h period in 15 different anticoagulant/antiplatelet combinations kept at room temperature and on ice-water mixture. We evaluated the following mixtures: K3EDTA, K3EDTA/prostaglandin E1 (PGE1), K3EDTA/PGE1/theophylline, Na2EDTA, Na2EDTA/PGE1, citrate 1:9, citrate 1:4, citrate 1:9/PGE1/theophylline, citrate 1:4/PGE1/theophylline, citrate 1:9/PGE1, citrate 1:9/dextrose, citrate 1:4/dextrose, acid-citrate-dextrose (ACD) 15%, ACD 11.9%, ACD 11.9%/Na2EDTA. In a second experiment we evaluated MPV, at room temperature only, in a further 20 volunteers in K3EDTA, citrate 1:9, ACD 11.9%/Na2EDTA, ACD 11.9% (total = 30) and citrate-phosphate-dextrose-adenine (CPDA; total = 20). Over the 29 h period there was a significant positive trend of increasing MPV in K3EDTA, CPDA and ACD 11.9%/Na2EDTA and a negative trend in citrate 1:9. ACD 11.9% showed no significant change in MPV with time at room temperature. This methodology should enable the wider application of MPV measurement for routine clinical and research studies.

Adult↗
PubMed1996

Recommendations for the treatment of factor VIII inhibitors: from the UK Haemophilia Centre Directors' Organisation Inhibitor Working Party.

A strategy is described for the initial detection, management and elimination of factor VIII inhibitors arising in patients with congenital and acquired haemophilia A. It is suggested that children with severe haemophilia A should be screened every 3 months up to the age of 10 years for inhibitors using the Bethesda method. Factor VIII inhibitors arising in these patients should be abolished using immune-tolerance induction wherever possible. Such regimes should be started as early as possible, preferably when the inhibitor titre is < 10 Bethesda Units (BU)/ml, and should not be interrupted. High-intensity regimes are recommended for patients whose inhibitors exceed 10 BU. Autoantibodies to factor VIII giving rise to acquired haemophilia should be abolished using high-dose immunoglobulin or conventional immunosuppression. The choice of haemostatic agent for the treatment of severe bleeding should be based upon the clinical circumstances and the current inhibitor value, measured using both human and porcine factor VIII in the Bethesda assay. The past anamnestic response should also be considered when choosing treatment for minor bleeding episodes.

Blood Coagulation Factors↗
PubMed1996

High purity factor IX and prothrombin complex concentrate (PCC): pharmacokinetics and evidence that factor IXa is the thrombogenic trigger in PCC.

Recent studies using assays for surrogate markers of thrombogenicity in man have demonstrated that activation of the coagulation system occurs following infusion of clinical doses of prothrombin complex concentrates (PCC) but not after the same doses of high-purity factor IX concentrates (HP-FIX) in patients with haemophilia B. Here we have investigated the mechanism of such thrombogenesis by applying assays that detect early-through to late-events in coagulation system activation in a pharmacokinetic cross-over study of 50 IU/kg PCC and a new HP-FIX product in haemophilia B patients. Satisfactory recoveries and half-lives were observed for both concentrates. HP-FIX caused no increases in thrombin-antithrombin III complex (TAT), prothrombin activation peptide fragment F1+2 (F1+2), factor X activation peptide (FXAP) or factor VIIa (FVIIa). In contrast the same dose of factor IX in the form of PCC was followed by significant increases over pre-infusion levels of TAT, F1+2 and FXAP, but not FVIIa. Elevations of FIXAP occurred after both HP-FIX and PCC but did not reach normal levels and were attributed to normalisation of the FIX concentration in those patients whose levels of FIXAP were initially low. We conclude that the thrombogenic trigger associated with PCC infusion occurs at the level of factor X activation. In the absence of any increase in FVIIa, we would attribute this to the likely presence of FIXa in the PCC.

Adult↗
PubMed1995

Heterogeneity of hepatitis C virus genotypes in hemophilia: relationship with chronic liver disease.

In this study we have determined the hepatitis C virus (HCV) serotype and genotype in a cohort of 96 HCV-infected hemophiliacs and have examined the relationship between HCV genotype and severity of chronic liver disease as determined by liver biopsy. HCV serotype was determined by specific enzyme-linked immunosorbent assays (ELISAs) and genotype by restriction fragment length polymorphism (RFLP) and HCV viral sequencing. The pattern of genotype distribution was quite unlike that of HCV-infected United Kingdom (UK) blood donors in that five of the six known HCV genotypes were represented, 50% were type 1, 13% type 2, and 18% type 3. An unexpected observation was the presence of HCV genotype 4 in four patients and type 5 in two patients. An additional feature was the presence of mixed infection, detected in 14% and 7% by serotype and genotype analysis, respectively. Liver biopsies were available from 51 patients. Cirrhosis was present in five of 27 (19%) of individuals with type 1, in 2 of 9 (22%) with type 2, and 5 of 8 (63%) of those with type 3. The heterogeneous pattern of HCV genotype distribution in this cohort of patients and the observed relationship between the severity of the related liver disease and specific HCV genotype may have important implications with respect to the natural history and treatment of HCV-related chronic liver disease in infected hemophiliacs worldwide.

Alanine Transaminase↗
PubMed1995

Low proteins C and S and activation of fibrinolysis in treated essential thrombocythemia.

The aim of this study was to investigate whether abnormalities in the fibrinolytic system and in the naturally occurring anticoagulant proteins could contribute to the thrombotic risk in essential thrombocythemia. Euglobulin lysis time, fibrin plate lysis area, tissue plasminogen activator antigen, and activity and plasminogen activator inhibitor antigen were measured before and after venous occlusion in a group of 16 patients with essential thrombocythemia and in 16 healthy age and sex matched controls. In addition, resting levels of antithrombin III, D-dimer, prothrombin fragment 1 + 2, and protein C and S were assessed. The results were related to the presence or absence of a thrombotic history. The results demonstrated that the patients had a significantly elevated fibrin plate lysis area and significantly decreased plasminogen activator antigen, both at baseline and after venous occlusion. They also had significantly decreased levels of plasma protein C and total protein S. There was a modest, non-significant elevation in the plasma concentration of D-Dimer and F 1 + 2. Those patients with a history of thrombosis had significantly lower protein C levels compared with individuals without a thrombotic history. We conclude that patients with essential thrombocythemia have evidence of activated fibrinolysis in the resting state and after stimulation. This, and the decreased levels of protein C and total protein S, may be secondary to chronic clinically occult thrombosis occurring in myeloproliferative disorders.

Adult↗