Strategy for adventitious agent assays.

There are three important questions to be addressed when considering a strategy for adventitious virus screening. (i) What viruses should be tested for? This will depend on the species of origin of the production cell although careful consideration has to be given also to the entire manufacturing process for the possible introduction of a contaminating virus from other biological materials used in production, e.g. bovine serum. (ii) What tests should be performed? Tests for viruses are highly varied. General tests act as "catch-all" types of assays. These are complemented by a variety of tests for individual viruses or types of viruses. (iii) At what stage(s) during the manufacturing process should virus testing be performed? Manufacturing stages which should be tested for virus contamination include extensive testing of the master cell bank and limited testing of the working cell bank and end of production cells.