Switching clotting factor concentrates: considerations in estimating the risk of immunogenicity

The development of neutralizing antibodies to factor VIII (FVIII) is the most serious complication of therapy for haemophilia A. There is now excellent documentation that a large number of both genetic and environmental factors contribute to the risk of FVIII inhibitor incidence. One of the environmental factors that has been proposed as an influence on this complication is the occurrence of FVIII product switching. There are only a small number of clinical studies that have addressed this question, and thus, the amount of objective information available to assess this association is limited. In this review, in addition to summarizing past evidence pertinent to this subject, we present the results of a complementary strategy, a Delphi analysis, to add to the considerations of product switching and FVIII immunogenicity. With the imminent arrival in the clinic of several new FVIII products, the haemophilia community must be prepared to collect prospectively controlled data to better address this important management issue.     

The future of plasma-derived clotting factor concentrates

In developed countries, preferred treatments for both haemophilia A and B have moved toward recombinant clotting factor concentrates, while plasma-derived replacement therapies are still required by many patients. Great improvements have been made in producing relatively pathogen-free clotting factor replacements from pooled plasma. The fluidity and complexity of the worldwide plasma product market are discussed in the context of the 'yin and yang' of plasma therapeutics, showing how multiple issues can influence the safety and availability of clotting factor concentrates. Use of plasma-derived products will likely continue for the next decade for patients with inhibitors, patients with von Willebrand disease, those requiring bypassing agents, in immune tolerance induction, and for treatment of rare inherited deficiencies of procoagulant or anticoagulant proteins. Furthermore, in developing countries many of the most advanced therapies are not available for the majority of haemophilia patients, and thus plasma-derived replacement concentrates will continue to be used even for noninhibitor patients.     

The effect of clotting factor concentrates on the immune system in HIV-negative haemophilics

Immune abnormalities have been reported in patients with haemophilia. Although infections with HIV and hepatitis viruses contribute to these abnormalities, chronic exposure to extraneous proteins in clotting factor concentrates (CFC) may also play a role. A number of studies suggest that the degree of immunological abnormalities correlates with the amount of intermediate purity CFC administered over time. The purpose of this study was to investigate whether there were cellular and humoral immunological abnormalities in haemophilics receiving intensive factor replacement therapy with intermediate purity CFC. For this purpose 48 severe haemophilics and 33 healthy controls were enrolled in this study. T and B lymphocytes, CD4+ and CD8+ cell counts, CD4/CD8 ratio, natural killer cells, active T cells were studied in prophylaxis group, on-demand therapy group and healthy controls. In the percentages and absolute counts of lymphocyte subgroups, no significant difference was found between three groups. We also investigated serum antitetanus IgG levels in these 48 haemophilics and the controls to evaluate the specific antibody response. Antitetanus IgG levels were significantly lower in haemophilics compared to healthy controls (P < 0.001). Additionally we evaluated the response to tuberculin skin test in 45 of 48 haemophilics vaccinated with BCG. The response to PPD test was significantly lower in haemophilics compared to the controls (P = 0.037). There was no response to tuberculin test, which is the best marker of delayed type hypersensitivity (DTH) reactions in 24% of haemophilics. In conclusion, although there was no significant change in the ratio of CD4/CD8 and lymphocyte subgroups, specific antibody responses and DTH tests were partially impaired in haemophilic patients receiving intermediate purity CFC.     

The use of intermediate-purity clotting factor concentrates and HIV disease progression in men with haemophilia

Summary. On the basis of evidence from the immune systems of patients with haemophilia infected with HIV, patients in the UK have been switched to high-purity clotting factor concentrates. However, there is very little information currently available on the effect of intermediate-purity clotting factor concentrates on progression of HIV disease. Among 99 HIV-positive men with severe factor VIII deficiency registered at The Royal Free Hospital Haemophilia Centre, a 100 IU kg^-1 increase in the yearly amount of concentrate received did not appear to be associated with more rapid progression to AIDS, death or to a low CD4 count. However, the use of total concentrate usage may mask a more subtle effect of specific concentrate contaminants on the progression of HIV disease.     

Transmission of symptomatic parvovirus B19 infection by clotting factor concentrate

The risk of acquiring diseases from transfusion of blood and blood products is well recognized and the issue of parvovirus in haemophiliacs is not a new one. We report two patients with haemophilia acquiring iatrogenic parvovirus B19 infection, resulting in life-threatening sepsis in one, an immunocompetent adult. Over the last 10 years there has been great progress in manufacturing safer products with regard to enveloped viruses such as HIV, hepatitis B and C. A recent outbreak across Europe of hepatitis A in haemophiliacs treated with plasma-derived factor VIII concentrates has made haemophilic treaters concerned about the known (parvovirus B19 and hepatitis A) and the unknown non-lipid enveloped viruses that may be contained in the clotting factor concentrates, because these are resistant to the existing viral inactivating techniques. The possibility of HIV itself mutating into a non-lipid enveloped virus emphasizes the need to seek and use safer products.     

Vitronectin in clotting factor IX concentrates

Highly purified, plasma-derived factor IX (FIX) concentrates are produced in large part by a combination of anion exchange and heparin affinity chromatography. However, the concentrates still contain some accompanying proteins. The main impurity has turned out to be the adhesive glycoprotein, vitronectin. It occurs in concentrates exclusively in its multimeric form, in contrast to the situation in plasma. The multimeric vitronectin can be removed either by nanofiltration with a crossflow system or by size-exclusion chromatography. When these FIX concentrates are used as therapeutic agents, the fact has to be taken into account that considerable amounts of multimeric vitronectin are given to the patient. The physiological consequences of the dosage of this protein have not yet been investigated. Although no thrombogenicity has been reported in connection with the above-mentioned FIX concentrates, we recommend that the impurity should be removed from the preparation with the methods described here.     

Seroprevalence of parvovirus B19, cytomegalovirus, hepatitis A virus and hepatitis E virus antibodies in haemophiliacs treated exclusively with clotting-factor concentrates considered safe against human immunodeficiency and hepatitis C viruses

Clotting-factor concentrates (CFC) are a potential source of transmission of blood-borne viruses. Newer physical and chemical methods (pasteurization, wet-heating, solvent/detergent treating) developed to inactivate viruses are effective against HIV, HBV and HCV. However, it is not clear if these methods protect against other pathogenic viruses such as parvovirus B19, cytomegalovirus (CMV), hepatitis A virus (HAV) and hepatitis E virus (HEV). To evaluate the safety of current CFC we have studied seroprevalence of parovirus B19, CMV, HAV and HEV antibodies in 22 HIV and HCV negative haemophiliacs who were treated exclusively with clotting-factor concentrates considered safe with respect to HIV and HCV transmission, 22 healthy individuals served as controls. Neither HAV nor HEV antibodies were detected in haemophiliacs or controls.
Two controls and two haemophiliacs were seropositive for CMV. Five controls (32% prevalence) and 15 haemophiliacs (77%) were positive to parovirus B19. No statistical differences can be established for seropositivity with CMV, HAV and HEV between haemophilic patients and controls. In the case of parvovirus B19 the differences are statistically significant ( P = 0.0128). The relative risk of parvovirus B19 is 2.4 in the case of haemophiliacs. CFC considered safe against HIV and HCV are not safe against parvovirus B19, although they seem to be safe against CMV, HAV and HEV.     

Retrospective review of the management of elective surgery with desmopressin and clotting factor concentrates in patients with von Willebrand disease

Limited data are available regarding optimal treatment with desmopressin (DDAVP) or intermediate-purity FVIII concentrates rich in VWF (CFCs) in patients with von Willebrand disease (VWD) who undergo planned surgery. We undertook a retrospective review over 10 years (1988-1997) and identified 27 patients treated with DDAVP for 35 surgical events and 38 patients who received CFCs for 68 elective surgical events. Tranexamic acid was usually added for mucosal surgery. The FVIII:C levels and the severity of surgery were used to determine the frequency and the doses of postoperative treatment. For major surgery the median pre- and post-operative doses of CFCs were 54 and 43 IU/kg, respectively, and for minor surgery the median doses varied between 34 and 52 IU/kg preoperatively and between 23 and 37 IU/kg postoperatively. The effectiveness of haemostasis was excellent in 32 events (91%) treated with DDAVP and in 56 events (82%) treated with CFCs. It is concluded that patients with VWD do not carry an increased operative risk if appropriate therapy is given.     

Hepatitis G virus infection in patients with bleeding disorders

Eighty-two patients with bleeding disorders registered with our centre were screened for infection with hepatitis G virus (HGV). 80 patients were positive for hepatitis C (HCV) antibodies, 66 of whom (83%) were HCV PCR positive. 11 patients (13%) were HGV RNA-positive, a similar prevalence rate to that of other studies of patients with bleeding disorders who received factor concentrates prior to the introduction of viral inactivation procedures. There was no significant difference in histological activity index (HAI) between the 10 HGV RNA-positive and the 31 HGV RNA-negative patients who underwent liver biopsy for assessment of HCV infection (median HAI scores 5.5, range 2–10 and four, range 0–10 respectively, P  = 0.07). One patient in each group had established cirrhosis. In patients who underwent HCV quantitation there was no significant difference in HCV viral titre between HGV RNA-positive and negative patients (median HCV titre in HGV RNA-positive patients 2.10 × 10⁵ DNA copies /ml ( n  = 8) range 4.17 × 10² to 4.17 × 10⁶, median HCV titre in HGV RNA-negative patients 3.33 × 10⁵ ( n  = 31) range 1.00 × 10³ to 6.67 × 10⁶, P  = 0.68). In this study there was no evidence that individuals co-infected with HGV and HCV have more severe liver disease than those infected with HCV alone.     

Continuous infusion of coagulation factor concentrates during intensive treatment

In clinical management of bleeds and surgical procedures in patients suffering from bleeding disorders either repetitive bolus injections (BI) or continuous infusion (CI) can be used for coagulation factor replacement. Continuous infusion seems to be an attractive route of administration and may be considered if replacement therapy is required for more than 3 days. The strongest argument favouring continuous infusion is its superiority in providing the patient with a safe and constant level of the deficient coagulation factor by balancing input with clearance. Furthermore, several studies have shown that coagulation factor consumption may be reduced by CI compared to repetitive bolus injections (BI) since unnecessary peaks of factor level are avoided. Concerns have been raised whether continuous infusion of coagulation concentrates is associated with an increased risk of developing inhibitors. However, available data have so far not shown an increased risk for inhibitor development in severe haemophilia patients with more than 50 exposure days of coagulation factor concentrates. Further, previously reported complications when using CI such as phlebitis at the infusion site and pump failure are nowadays very seldom seen when small amounts of heparin are added to the infusion bag, and increased quality of the pumps are available. Over the last decades, numerous reports have confirmed CI to be a safe and effective mode of coagulation factor replacement even in the most challenging surgical procedures, such as total joint arthroplasties.     

In vitro reversal of supratherapeutic rivaroxaban levels with coagulation factor concentrates

BackgroundA bleeding patient undergoing therapy with new oral anticoagulants is every clinician’s nightmare as no specific reversal agent is available yet. This in vitro study investigated the effect of prothrombin complex concentrate (PCC), recombinant activated factor VII (rFVIIa) and activated prothrombin complex concentrate (aPCC) on supratherapeutic rivaroxaban concentrations using standard laboratory parameters (prothrombin time [PT], activated partial thromboplastin time [aPTT] and PT ratio) and thromboelastometry (clotting time [CT]).ResultsThe addition of the reversal agents had the following statistically significant effects (all p<0.01): +25 IU/kg PCC: CT −15 s, aPTT +5 s; +50 IU/kg PCC: aPTT +11 s; +90 μg rFVIIa: CT −141 s; +25 IU/kg aPCC: CT −142 s, aPTT −9 s, PT ratio +14%, PT −10.5 s; +50 IU/kg aPCC: CT −118 s, aPTT −7 s, PT ratio +17%, PT −12.2 s.DiscussionrFVIIa and aPCC, but not PCC, appear to shorten coagulation times significantly in standard laboratory and thromboelastometry assays. These results need confirmation through evaluation of these agents in the clinical setting.     

Hepatitis G virus RNA and its relation to hepatitis C infection in adult haemophilic patients

The prevalence of hepatitis C virus (HCV) infection and hepatitis G virus (HGV) RNA were studied in 50 adult haemophilic patients who had received commercial clotting factors prior to 1980. HGV RNA was detectable in 6/50 patients (12%); 49/50 (98%) had antibody to HCV and 40/49 (82%) of these were viraemic with detectable HCV RNA; 5/6 patients with detectable HGV RNA had co-existing HCV infection and viraemia. The HGV PCR products from all six patients were directly sequenced and all were shown to be similar to that of HGV but more diverse from that of GB virus C. One patient who had persistent abnormal liver function tests had detectable HGV RNA but no evidence of hepatitis B or C. The presence of HGV RNA in the absence of hepatitis B and C infection indicates that this virus is capable of independent transmission. Independent response to interferon was demonstrated in one patient with co-infection who lost HGV but not HCV after interferon therapy.     

Inhibitor development in haemophilia A: the role of von Willebrand factor/factor VIII concentrates

Summary.  The presence of inhibitors that neutralize the function of factor VIII (FVIII) decreases the haemostatic efficacy of replacement clotting factor concentrate and increases morbidity among patients with haemophilia A. Certain genetic and environmental variables have been linked to a higher incidence of inhibitors. Conversely, the presence of von Willebrand factor (VWF) in some plasma-derived FVIII products may provide some measure of protection against inhibitor development, although the evidence is not conclusive. Clinical trials are needed to resolve this issue and determine the appropriate role of VWF-containing FVIII concentrates in the treatment of haemophilia A patients.     

Clotting factor concentrates and immune function in haemophilic patients

Patients with haemophilia often exhibit a variety of disturbances in immune function. Although infections with HIV, hepatitis and other viruses no doubt contribute to these abnormalities, chronic exposure to extraneous proteins in clotting factor concentrates (CFCs) may also play a role. Numerous in vitro and ex vivo studies show that protein contaminants – such as immunoglobulins, fibrinogen and fibronectin – can depress various immune function indicators. Generally, such studies show that intermediate-purity CFCs are more inhibitory than very high-purity (e.g. monoclonal-purified) CFCs. In many, but not all, studies, the degree of immunosuppression correlates with the amount of intermediate-purity CFC administered over time.   Among various indicators of immune function, CD4+ lymphocyte number is a marker for the progression of HIV infection, and maintenance of CD4+ number is associated with delayed progression. A number of studies suggest that, compared with intermediate-purity CFCs, use of very high-purity CFCs is associated with longer preservation of this class of lymphocytes. However, it remains to be seen whether this translates to improved long-term clinical outcomes.   Further research is needed on the impact of CFCs on the immune system. For the time being, however, evidence to date favours the use of very high-purity products because they appear to preserve immune function and reduce the risk of infection with hepatitis and other viruses.     

Absence of hepatitis A virus transmission by high-purity solvent detergent treated coagulation factor concentrates in Scottish haemophiliacs

Summary. Recent reports of hepatitis A virus (HAV) infection in haemophiliacs receiving high-purity solvent detergent (HP.SD) treated factor VIII concentrates have brought into question the efficacy of this virucidal method for inactivating HAV. To assess whether HAV may have been transmitted by HP.SD concentrates, we compared seroprevalence in haemophiliacs with different disease severity, sought evidence of seroconversion to HAV since introduction of HP.SD products, and directly examined concentrates for HAV RNA by PCR. Our data suggest that Scottish haemophiliacs are not being infected with HAV by HP.SD concentrates produced initially by CRTS Lille and presently by PFC Edinburgh and supplied by the Scottish National Blood Transfusion Service (SNBTS).     

Setting research priorities to improve cost-effectiveness estimations of primary prophylaxis with clotting factor for people with severe haemophilia

Summary.  Primary prophylaxis with clotting factor is the clinical treatment of choice for people with severe haemophilia, as evidence suggests it can prevent the onset and progression of joint- and muscle-related problems caused by bleeding episodes. However, the major limitation of this approach is that it requires considerably more clotting factor compared with treating on-demand. Thus, there is a need to establish its cost-effectiveness. The aim of this paper is to review the published evidence on the cost-effectiveness of prophylaxis and to highlight areas for future research that would decrease the uncertainty around these findings.     

Hepatitis G virus infections in Iceland

This study describes the prevalence of hepatitisG virus (HGV) in Iceland, in blood donors and in persons with parenteral risk factors. Among 370 randomly selected Icelandic blood donors, the prevalence of HGV viraemia was 3.8%, whereas the prevalence of HGV antibodies in the same donor group was found to be 13.2%, thus indicating that at least 17% of blood donors in Iceland had previously been exposed to HGV. Previous exposure was seen in all age groups and also in older blood donors. Among intravenous drug users (IVDUs), the prevalence of HGV was much higher. Among 109 hepatitisC virus (HCV) antibody-positive serum samples collected in the years 1992–1997, 33.9% were polymerase chain reaction (PCR)-positive for HGV and 48.6% had HGV antibodies. Thus, the pattern of HGV in IVDUs was similar to findings among IVDUs in other western countries. HGV viraemia was detected neither in 10 patients with haemophilia nor in five dialysis patients. However, six of the 10 haemophilic patients and one of the five dialysis patients had HGV antibody. In conclusion, unlike hepatitisC, which seems to have been introduced into Iceland relatively recently and has remained virtually confined to IVDUs, exposure to HGV is common among all age groups in the general population, suggesting that the virus has been prevalent in Iceland for much longer, making additional routes of transmission probable.     

Safety of coagulation factor concentrates

Summary. Many of the adverse effects of the early crude plasma-derived concentrates were ameliorated by increasing their purity. Ironically, this strategy may have increased the risks of inhibitor formation and pathogen transmission due to the addition of processing steps which can alter the immunogenicity of clotting factors and the use of very large plasma pools, as dictated by economic considerations. In the absence of extremely sensitive donor screening, these large pools have a high probability of contamination with pathogens, which may be only partially offset by their removal during protein purification. One approach to minimize the risk of viral transmission is to use recombinant clotting factors produced without the use of human or animal plasma proteins at any step in the manufacturing or formulation process. However, as these proteins are synthesized in mammalian cells, even they pose a theoretical risk of pathogen transmission. For plasma-derived concentrates, the initial viral burden is minimized by screening individual donations and plasma pools with tests which detect virusspecific antibodies, protein antigens, or nucleic acid. These techniques are supplemented by non-specific viral reduction steps based on physical partitioning and/or inactivation of pathogens which share chemical or physical characteristics. Prion proteins, the putative causative agents of transmissible spongiform encephalopathies, do not share these characteristics with viruses, and it remains to be determined whether they partition into clotting factor concentrates and whether the current strategies can efficiently remove or inactivate them. For all blood-borne pathogens, active immunization (currently available only for hepatitis B and A) and continued surveillance of susceptible recipients are critical approaches to achieving optimal safety of coagulation factor concentrates.     

Implementation of a nurse practitioner policy for the requisition and administration of drugs in a haemophilia comprehensive care centre

Summary The evolution of comprehensive care centres for haemophilia has altered the work of those involved in the care of haemophilia patients. The role of the haemophilia sister has expanded and the concept of the haemophilia nurse specialist has emerged. We describe the implementation of a local policy which has enabled haemophilia nurse specialists to requisition and administer clotting factor concentrates, DDAVP, tranexamic acid and hepatitis vaccines independently, in hospital and community settings. Since the introduction of this policy on 2 August 1994, prescribing practice has not changed in the haemophilia centre, nor has the involvement of medical staff in the care of haemophilia patients. This approach is widely applicable in other centres and should be a logical progression of the haemophilia nurse specialist's role.