The hazards of retroviruses associated with monoclonal antibody production.

The majority of mammalian cells contain in their chromosomes genetic information related to retroviruses. Mice, and in particular, the inbred strains used in laboratory studies, have a number of different types of these viruses and murine cell lines frequently express virus. Retrovirus production has been noted in a number of myeloma cell lines and in hybridomas prepared from them. Therefore crude monoclonal antibody preparations may contain large numbers of these viruses. Retroviruses have been shown to be capable of activating or of acquiring oncogenes from cells. They may also recombine with endogenous leucosis virus to produce a recombinant virus with pathogenic properties. Comparison of endogenous cell DNA and retrovirus sequences has shown that retroviruses are capable of crossing genus and even class barriers. Retroviruses that are harmless in one species may be pathogenic in another. Hence care is required in the manufacturing and quality control procedures applied to monoclonal antibodies, particularly with products intended for medical and veterinary use. Widespread inoculation of retroviruses into a range of animal species may result only in trauma for the occasional individual but it is not possible to preclude the formation of a new type of pathogenic agent that can spread throughout the population.