Studies on the resistance of the C57B1/6 mouse strain to the polycythemia-inducing strain of the Friend virus (FV-P)

Friend virus replication as a function of age

We have investigated the effect of age on the replication of Friend spleen focus-forming virus (SFFV). Recovery of SFFV from the spleens of four strains of mice was determined following intravenous infection with NB-tropic Friend virus (FV) complex at ages ranging from 6 to 134 weeks. In C57BL/6 mice, the virus did not replicate in adults up to 40 weeks of age, but beyond that there was a steep exponential increase with age in the amounts of SFFV recoverable. In C3H/He mice, which replicate the virus as young adults, the amount of SFFV recovered was 6-fold greater in old than in young mice. Recovery of virus was biphasic with age in SJL mice; in A strain mice no consistent change with age was noted. In C57BL/6 mice, reconstitution of lethally irradiated recipients with syngeneic marrow cells, followed by i.v. infection with FV, showed that the amounts of SFFV recovered depended on the age of the recipient. The present work shows that Friend SFFV replication is a sensitive indicator and can be used as a tool for the investigation of aging processes. The mechanisms responsible for the age-dependent change in regulation of virus replication and for the polymorphism remain to be determined.