Serial Passage of a Lymphocytic Tumor and Choriomeningitis Virus in Immune Mice

Abstract

Lymphocytic choriomeningitis (LCM) virus associated with an ascitic form of the lymphocytic tumor P288 survived indefinite serial passage in LCM-immune strain CDBA mice. Initially it was necessary to treat the mice with amethopterin (methotrexate), but after repeated passage the virus survived in untreated immune mice with intraperitoneal, but not with subcutaneous, tumors. In immune Swiss mice, where the tumor normally regresses, amethopterin enabled both tumor and virus to survive if the tumor was in the ascitic form. In immune Swiss mice not treated with amethopterin, the LGM-carrying tumor from 2 passage lines behaved differently; the tumor that had been maintained in amethopterin-treated immune CDBA mice did not support LCM survival, but the tumor adapted to passage in untreated immune CDBA mice supported LCM survival during the early stages of ascites tumor growth. The explanation offered for the survival of LCM in immune mice under these conditions is that virus passes from one tumor cell to its offspring at the time of cell division. Similarities between these LCM tumor-cell relationships and several other virus-cell interactions are discussed.