A consensus rating method for small virus-retentive filters. I. Method development

Virus filters are membrane-based devices that remove large viruses (e.g., retroviruses) and/or small viruses (e.g., parvoviruses) from products by a size exclusion mechanism. In 2002, the Parenteral Drug Association (PDA) organized the PDA Virus Filter Task Force to develop a common nomenclature and a standardized test method for classifying and identifying viral-retentive filters. One goal of the task force was to develop a test method for small virus-retentive filters. Because small virus-retentive filters present unique technical challenges, the test method development process was guided by laboratory studies to determine critical variables such as choice of bacteriophage challenge, choice of model protein, filtration operating parameters, target log10 reduction value, and filtration endpoint definition. Based on filtration, DLS, electrospray differential mobility analysis, and polymerase chain reaction studies, a final rating based on retention of bacteriophage PP7 was chosen by the PDA Virus Filter Task Force. The detailed final consensus filter method was published in the 2008 update of PDA Technical Report 41. Virus Filtration.