Validation of virus inactivation and removal for the manufacturing procedure of two immunoglobulins and a 5% serum protein solution treated with beta-propiolactone

T-cell inhibitory capacity of hyperimmunoglobulins is influenced by the production process

Intravenous immunoglobulin (IVIg) preparations are widely used for anti-inflammatory therapy of autoimmune and systemic inflammatory diseases. Hyperimmunoglobulins enriched in neutralizing antibodies against viruses can, in addition to their virus-neutralizing activity, also exert immunomodulatory activity. Previously, we observed that Cytotect®, an anti-CMV hyperimmunoglobulin, was less effective in suppressing human T-cell responses in vitro compared to Hepatect® CP, an anti-HBV hyperimmunoglobulin. We hypothesized that the poor immunomodulatory activity of Cytotect® results from treatment with β-propiolactone during the manufacturing process. The manufacturer of these hyperimmunoglobulins has now introduced a new anti-CMV hyperimmunoglobulin, called Cytotect® CP, in which β-propiolactone treatment is omitted. Here we show that Cytotect® CP inhibits PHA-driven T-cell proliferation and cytokine production with similar efficacy as Hepatect® CP, whereas the former Cytotect® does not. In addition, Cytotect® CP inhibits allogeneic T-cell responses better than Cytotect®. Our results advocate the use of hyperimmunoglobulins that have not been exposed to β-propiolactone in order to benefit from their immunomodulatory properties.

Identification of target antigens of self-reactive IgG in intravenous immunoglobulin preparations

Intravenous immunoglobulin (IVIg) contains a wide range of self-reactive immunoglobulins (Ig) G. Acidic pH is known to increase the reactivity of purified IgG with self-antigens. We describe here the target antigens of IgG autoantibodies in IVIg and analyze the influence of acidic pH on IgG reactivities. We used 2-DE and immunoblotting with protein extracts of human umbilical vein endothelial cells (HUVEC) and HEp-2 cells. Two IVIg preparations obtained by ethanol fractionation [one with an acidic pH step (acidic-IVIg) and one with beta-propiolactone (propiolactone-IVIg)] and a pool of sera from 12 healthy individuals were tested. Serum IgG of 3 healthy individuals and IgG purified from the same sera with elution at pH 2.8 were also tested individually. Finally, propiolactone-IVIg was acidified at pH 2.8. IgG obtained with a step at low pH recognized many more target spots than IgG obtained without acidic pH. Our findings demonstrate that an acidic pH step artificially enlarges the repertoire of self-reactive IgG. Thus, protein spots recognized by IgG in propiolactone-IVIg represent the core set of self-antigens targeted by IVIg. Overall, 96 proteins were identified by MS. Fourteen were recognized in both extracts including glycolysis proteins such as alpha-enolase, RNA processing and cytoskeletal proteins such as lamin-A/C.

Virus safety of intravenous immunoglobulin: future challenges

Patients with immunodeficiencies or some types of autoimmune diseases are dependent on safe therapy with intravenous immunoglobulins. State-of-the-art manufacturing processes provide a high safety standard by incorporating virus elimination procedures into the manufacturing process. Based on their mechanism, these procedures are grouped into three classes: partitioning, inactivation, and removal based on size. Because of current socioeconomic and ecological changes, emerging pathogens continue to be expected. Such pathogens may spread very quickly because of increased intercontinental traffic. Severe acute respiratory syndrome-coronavirus and the West Nile virus are recent examples. Currently, it is not possible to predict the impact such a pathogen will have on blood safety because the capacity for a globally coordinated reaction to such a threat is also evolving. The worst-case scenario would be the emergence of a transmissible, small, nonenveloped virus in the blood donor population. Examples of small nonenveloped viruses, which change host and tissue tropism, are discussed, with focus on parvoviridae. Although today's immunoglobulins are safer than ever, in preparation for future challenges it is a high priority for the plasma industry to proactively investigate such viruses on a molecular and cellular level to identify their vulnerabilities.

Reducing the risk of infection from plasma products: specific preventative strategies

Collection and testing procedures of blood and plasma that are designed to exclude donations contaminated by viruses provide a solid foundation for the safety of all blood products. Plasma units may be collected from a selected donor population, contributing to the exclusion of individuals at risk of carrying infectious agents. Each blood/plasma unit is individually screened to exclude donations positive for a direct (e.g., viral antigen) or an indirect (e.g. anti-viral antibodies) viral marker. As infectious donations, if collected from donors in the testing window period, can still be introduced into manufacturing plasma pools, the production of pooled plasma products requires a specific approach that integrates additional viral reduction procedures. Prior to the large-pool processing, samples of each donation for fractionation are pooled ('mini-pool') and subjected to a nucleic acid amplification test (NAT) by, for example, the polymerase chain reaction (PCR) to detect viral genomes (in Europe: HCV RNA plasma pool testing is now mandatory). Any individual donation found PCR positive is discarded before the industrial pooling. The pool of eligible plasma donations (which may be 2000 litres or more) may be subjected to additional viral screening tests, and then undergoes a series of processing and purification steps that, for each product, comprise one or several reduction treatments to exclude HIV, HBV HCV and other viruses. Viral inactivation treatments most commonly used are solvent-detergent incubation and heat treatment in liquid phase (pasteurization). Nanofiltration (viral elimination by filtration), as well as specific forms of dry-heat treatments, have gained interest as additional viral reduction steps coupled with established methods. Viral reduction steps have specific advantages and limits that should be carefully balanced with the risks of loss of protein activity and enhancement of epitope immunogenicity. Due to the combination of these overlapping strategies, viral transmission events of HIV, HBV, and HCV by plasma products have become very rare. Nevertheless, the vulnerability of the plasma supply to new infectious agents requires continuous vigilance so that rational and appropriate scientific countermeasures against emerging infectious risks can be implemented promptly.

Multicenter crossover comparison of the safety and efficacy of Intraglobin-F with Gamimune-N, Sandoglobulin, and Gammagard in patients with primary immunodeficiency diseases

The safety and clinical efficacy of a liquid, beta-propiolactone-stabilized intravenous gamma-globulin, Intraglobin-F, was evaluated in a multicenter, double-blind study comparing Intraglobin-F to Gamimune-N, Sandoglobulin, or Gammagard. beta-Propiolactone stabilizes the IgG molecule to decrease aggregate formation and is a potent virucidal agent that reduces the risk of viral transmission by intravenous gamma-globulin (IVIG) preparations. Twenty-seven patients with primary immunodeficiency diseases were enrolled at three centers. Each patient received 6 months of therapy with either Intraglobin-F or the IVIG preparation that they had received during the preceding 3 months, then crossed over to the other preparation. Twenty-three patients completed the study. One patient withdrew because of an adverse event, generalized urticaria. A second patient withdrew because of fatigue and perceived decreased efficacy. Adverse reactions were comparable and occurred in 8.7% of the infusions of Intraglobin-F and 6% of the infusions with Sandoglobulin. None were severe or life-threatening. There was no discernible difference in efficacy between any of the products. The number of days when patients noted symptoms in their diaries was similar for Intraglobin-F and the comparison preparations, 4158 vs 4143. Similarly, there were no differences in the number of physician visits (33 vs 22), days missed from work or school (405 vs 404), days with fever (41 vs 47), or days of prophylactic antibiotics (675 vs 642). There was an increase in the number of days when antibiotics were given therapeutically (578 vs 451); most of the difference was attributable to one patient. There also was a difference in the number of days of hospitalization (21 vs 0), but 19 of the days were accounted for by two patients. When the patients were asked to score their feeling of well-being on a scale of 1 to 5, with 1 being entirely well, the mean score for the patients on Intraglobin-F was 1.86 (range, 1.0 to 3.0), compared to 1.85 (range, 1.0 to 3.2) for patients while on the comparison preparations. Trough IgG levels were slightly lower during the period when patients were treated with Intraglobin-F compared to the other products. There were no abnormalities in blood chemistries or hematologic parameters. Thus, Intraglobin-F is comparable to three of the marketed IVIG preparations in efficacy and safety, as well as patient acceptability, and offers the additional benefit of an extra virucidal step to reduce further the risk of transmitting viral infections.

Prevalence of hepatitis C virus in plasma pools and the effectiveness of cold ethanol fractionation

Screening blood donations for antibodies against hepatitis C virus (HCV) greatly reduces the risk of transmitting HCV by transfusions. However, despite such screening programs, plasma pools still contain a high percentage of HCV ribonucleic acid as determined by polymerase chain reaction. This result would not be alarming if the procedures for producing blood products included steps to inactivate or remove HCV. Although this appeared to be the case for all blood products, such as coagulation factors and most immunoglobulins, which are subjected to an inactivation step, the effectiveness of the cold ethanol fractionation process still needed to be determined. In validation experiments using bovine viral diarrhea virus as a model virus for HCV, we demonstrated that the Cohn-Oncley cold ethanol fractionation process neither inactivated nor removed this virus sufficiently. Our observations may help to explain how HCV was transmitted to a number of recipients of intravenous immunoglobulin.

[Viral safety of intravenous immunoglobulins G for therapeutic use]

Even though IV IgG concentrates are considered to be among the safest products derived from human plasma, some preparations have been associated with the sporadic transmission of NANB hepatitis and, specifically of hepatitis C. The risk of transmission may have decreased markedly for several IgG preparations since the availability of an immunological test to detect the antibodies against HCV in the starting plasma, but it has not been fully eradicated. Thus, in addition to established viral inactivation treatments, such as acid pH incubation, new methods have been (or are being) implemented to further reduce the risk of HCV infection through IV IgG concentrates. Among these methods are the solvent-detergent treatment already shown to be highly effective for the inactivation of HCV and other enveloped viruses in clotting factor concentrates, and nanofiltration for the specific removal of viruses on the basis of their size. Also, chromatographic methods have helped to improve the overall safety of the product not only by removing viruses but also by improving purity and thus favoring a better in vivo tolerance. This paper reviews the reported cases of HCV transmission and the viral validation data for various IV IgG processing steps and current specific viral inactivation methods. An overview of the present safety status of IV IgG concentrates is presented as well as the recent introduction of new promising techniques for the overall improvement of the safety of this plasma derivative.

Ensuring safety and consistency in cell culture production processes: viral screening and inactivation

The history of the use of biological products is littered with examples of the iatrogenic transmission of viruses. A major effort of the biotechnology industry is directed towards the elimination of any risk of infection from the products of cell culture. This article summarizes the overall strategy that has been followed, so far with great success, in that there have, as yet, been no reported cases of viral transmission by the products of biotechnology.