Virus removal and inactivation

Validation of virus removal and inactivation procedures (2/1991) Radiopharmaceuticals based on monoclonal antibodies (5/1991)... 

Committee for Proprietary Medical Products. Ad hoc working party on biotechnology/pharmacy and working party on safety medicines, EEC regulatory document, note for guidance vahdation of virus removal and inactivation procedures. Biologicals 1991,19, 247-251. 

Virus removal and inactivation have been reviewed by several authors [23, 25-27]. It is generally accepted that conventional water treatment practices can reduce viral levels by a factor of 10 to 10 in the finished water. Disinfection, mostly in the form of chlorination, has been the main method of virus inactivation in drinking water. Viruses seem to be considerably more resistant than coliforms, thus requiring higher doses and longer contact times (for ref. see [16]). 

Medicinal products derived from human blood or plasma have certain features arising from the biological nature of the source material. For example, disease-transmitting agents, especially viruses, may contaminate the source material. The prevention of the transmission of viruses by these products relies therefore on the control of source materials and their origin as well as on the subsequent manufacturing procedures, including virus removal and inactivation. 

Careful consideration should be given to the validation of methods for sterilization, disinfection, virus removal and inactivation. 

The virus reduction factor of an individual purification or removal—inactivation step is defined as the log10 of the ratio of the virus load in the pre-purification material divided by the virus load in the post-purification material. A clearance factor for each stage can be calculated and the overall clearance capacity of the production process assessed. Total virus reduction is calculated as the sum of individual log reduction factors. Individual manufacturing steps must possess fundamentally different mechanisms of virus removal or inactivation in order for values to be considered cumulative. Additionally, because viruses vary greatly with regard to inactivation or removal profiles, only data for the same model virus can be cumulative. 

Removal and Inactivation of Viruses by a Surface-Bonded Quaternary Ammonium Chloride... 

For the clearance of enveloped and non-enveloped viruses, today s requirements ask for an orthogonal combination of methods that are based on the different physical principles of removal and inactivation, and are complementary to each other [165]. Virus filtration and solvent/de-tergent treatment are state of the art for removal and inactivation [166, 167]. Partitioning steps are considered less robust, as they are somewhat influenced by the actual process conditions. In any case, scaled-down models must be designed... 

In order to prevent cross-contamination, premises and equipment used for manufacturing operations using products which have undergone a process of virus removal or inactivation should be dedicated and distinct from those used for non-treated products. 

As biopharmaceuticals are potentially contaminanted with possibly harmful viruses and allergenic and pyrogenic acting endotoxins as residual components of their host cell, guidelines and directions have been issued by the FDA s Center for Biologies Evaluation and Research (CBER) requesting validated procedures for virus and endotoxin removal and inactivation. 

Each interferon preparation was ultracentrifuged at 20,000 revolutions per minute for one hour to remove tissue debris and inactivated virus. The supernatant was dialyzed against distilled water (1 400) for 24 hours at4°C. The material was then freeze-dried. The dried product was reconstituted in one-tenth of the original volume in distilled water and dispensed into ampoules. Reconstituted solutions were assayed for interferon activity, examined for toxicity, and tested for sterility. 

The capacity of each step of the extraction and purification procedure to remove and/or inactivate contaminating substances derived from the host cell or culture medium, including, in particular, virus particles, proteins, nucleic acids and added substances, must be validated. 

Most of today s resins and filters can be cleaned and sanitized with agents such as sodium hydroxide, which has been shown to be very effective [34], In some cases, however, affinity chromatography ligands, especially those that are proteinaceous, are not resistant to the rather harsh conditions necessary to inactivate viruses, fungi, and bacteria or to remove residual product and impurities... 

Virus identification can start during cell bank characterization and continues until the final product is obtained. It is essential to demonstrate that the viruses are not co-purified with the product (FDA, 1993a, 1997 ICH, 1997). The efficiency of removal or inactivation procedures should be demonstrated on a small scale through spiking experiments, by the use of the viruses themselves, when identified and possible, or with model viruses which mimic any possible variants large or small, DNA or RNA genome,... 

Following growth of the virus in batch cell culture the culture fluid containing virus particles and cell debris is clarified by low-speed centrifugation or filtration to remove the latter. The virus preparation (inactivated when required) must then be tested for... 

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