Retrovirus screening of vaccine cell substrates.

A strategy for the detection of low levels of infectious retroviruses in vaccine cell substrates is outlined. This strategy involves amplification of possible viral contaminants in cell substrates by co-cultivation of the Cell Bank, with or without prior induction, with potentially susceptible cells followed by extended culturing and subsequent retrovirus testing using general and specific detection assays. In some cases, the virus seed may need to be examined by direct infection and extended culturing of cells that can support the replication of potential retroviral contaminants.