Experimental approaches to guarantee minimal risk of potential virus in purified monoclonal antibodies

Regarding biological products, increasing awareness of potential side effects have placed great importance not only at protein purity regarding other proteins but on the removal of biologicals such as DNA and especially virus the importance of which may not be known. Monoclonal antibodies (Mab) have come to be an important class of molecules obtained from hybridoma cells, i.e., nonrecombinant cells in culture. It has been noted during the last years, that with rare exceptions hybridoma cell lines contain retrovirus like particles. The infectious nature of the EM-visible particles has been tested for, however, in most cases not been substantiated. In order to bring these valuable biological reagents, Mab's, to good use in man for imaging or therapy, the remaining concern about a potential retroviral infection has to be reduced to an acceptable minimum. We describe experimental approaches for the validation of chromatographic and ultrafiltration steps used in the production of monoclonal antibodies to remove and inactivate murine retrovirus. Present day biotechnological manufacturing processes have been devised incorporating a number of strategic preventive measures that have found wide spread acceptance. They permit to answer the question: how can a potentially harmful infection by an unknown virus be excluded. Knowledge of the efficacy of purification steps to clear infectious model virus is fundamental to devise biotechnological manufacturing processes yielding a purified antibody for use in man.