Lymphatic Leukemia and Retrieval of Defective Friend Virus in Athymic Nude Rats 1

Abstract

Abstract

We have investigated the ability of Friend virus (FV) and the associated lymphatic leukemia virus (LLV) to replicate in athymic rats. We have also explored the ability of the LLV to act as helper in the retrieval of the defective FV genome from a virus-free, FV-induced tumor of BALB/c mice xenografted to this host. Athymic rats were found to be resistant to Friend disease. However, they did develop lymphatic leukemia when inoculated with FV. Following inoculation of LLV into newborn athymic rats, viremia was detected as early as 20 days and was followed by death from lymphatic leukemia approximately 100 days later. Athymic rats inoculated with LLV when newborn were later xenografted with cells from the virus-free, FV-induced tumor grown in vitro. Cell-free extracts of the tumors that developed induced typical Friend disease in newborn mice. Because the rat apparently lacks target cells for FV replication, the entire output of virus must have originated in the tumor itself, a situation in marked contrast to earlier experiments in BALB/c mice.