1.Nonspecific “model”viruses representing a range of physico-chemical structures:

•SV40(Polyomavirus maccacae 1),human polio virus 1(Sabin),animal parvovirus or some other small,nonenveloped viruses;

•a parainfluenza virus or influenza virus,Sindbis virus or some other medium-to-large,enveloped,RNAviruses;

•a herpes virus (e.g.,HSV-1or a pseudorabies virus),or some other medium-to-large,DNAviruses.

These viruses are examples only and their use is not mandatory.

2.For rodent cell substrates murine retroviruses are commonly used as specific “model”viruses.

Several viruses that have been used in viral clearance studies are listed in Table A-1.However,since these are merely examples,the use of any of the viruses in the table is not considered mandatory and manufacturers are invited to consider other viruses,especially those that may be more appropriate for their individual production processes.Generally,the process should be assessed for its ability to clear at least three different viruses with differing characteristics.