Viral contaminants found in mouse cell lines used in the production of biological products

Murine hybridoma and plasmacytoma cell lines are used in the production of biologics for human use such as therapeutic monoclonal antibodies and recombinant proteins. Most of these cell lines produce retro virus-like particles and in many cases infectious C type murine leukaemia virus (MLV) which can be either ecotropic (infectious for cell lines of murine origin or a closely related species) or xenotropic (infectious for species other than murine; X-MLV).