Removal of viruses from human intravenous immune globulin by 35 nm nanofiltration

Viral safety is an important prerequisite for clinical immunoglobulin prepa rations. A common manufacturing practice is to utilize several virus remova l/inactivation process steps to ensure the safety of human intravenous immu noglobulin (IVIg). In this regard, we examined the use of Planova 35 nm fil ters to reduce potential loads of both non-enveloped and enveloped viruses prior to end-stage solvent detergent treatment. The nanofiltration process was validated for removal of a variety of enveloped and non-enveloped virus es ranging in size from 70 nm to 18 nm including: Sindbis virus, Simian Vir us 40 (SV40), Bovine Viral Diarrhoea virus (BVDV), Feline Calicivirus, Ence phalomyocarditis virus (EMC), Hepatitis A virus (HAV), Bovine Parvovirus (B PV) and Porcine Parvovirus (PPV). The filtration procedure was carried out by first spiking a 7% solution of IVIg with <10(8) virus. The spiked IVIg s olution was then filtered through a 75 nm Planova filter followed by two Pl anova 35 nm filters in series (75/35/35). The 75 nm prefilter is incorporat ed into this process to increase the capacity of the 35 nm viral removal fi lters. As a result of the inclusion of the 75 nm pre-filtration step it was possible to assess the removal of virus by the 35 nm filters independent o f possible aggregation of the initial viral spiking material. Samples were collected at each step and immediately titred by viral plaque assay. A proc ess control sample of the spiked load solution was held at the same conditi ons for the duration of the filtration process and then titred to determine the extent to which antibody neutralization may have contributed to overal l viral reduction. Control assays of spiked IVIg were performed to establis h the degree of toxicity of the IVIg solution to the indicator cell lines a nd the extent to which the IVIg interfered with plaque formation in the ass ay system. This combined data was used to establish assay sensitivity for t he calculation of log removal by the filtration process. It was noted that toxicity/interference effects could have a significant effect upon apparent log reductions, and these effects could vary greatly, even within viruses of the same family. The results of these studies indicate that 35 nm filtra tion is very effective for removing substantial quantities of both non-enve loped and enveloped viruses from IVIg. Complete clearance (to the limits of detection of the assay) was obtained for all viruses larger than 35 nm. in terestingly, viruses reported to have mean diameters of less than 35 nm (EM C and HAV) were at least partially removed by the filtration (4.3 and >4.7 logs removal, respectively). Even small viruses such as PPV were to some ex tent removed from the IVIg solution by the filters (2.6 logs removal). Redu ction of BPV would not be assessed due to extensive neutralization and inte rference with plaque formation by the IVIg. Sindbis and SV40 also were subj ect to neutralization and assay interference due to the IVIg, though to a l esser extent. We conclude from these studies that the 35 nm mean pore size is functionally efficient in removal of smaller size viruses from spiked IV Ig concentrates. (C) 1998 The International Association of Biological Stand ardization.