CHARACTERIZATION OF A NEUROLOGIC DISEASE INDUCED BY A POLYTROPIC MURINE RETROVIRUS - EVIDENCE FOR DIFFERENTIAL TARGETING OF ECOTROPIC AND POLYTROPIC VIRUSES IN THE BRAIN

A variety of ecotropic murine leukemia viruses cause neurodegenerative disease. We describe here the clinical and histopathological features of a neurologic disease induced by a polytropic murine leukemia virus , FMCF98. Clinical disease was dominated by hyperexcitability and atax ia, and the histopathology was characterized primarily by astrocytosis and astrocytic degeneration. The viral envelope gene harbored the det erminants of neurovirulence, since the chimeric virus Fr98(E), which c ontained the envelope gene of FMCF98 on a background of the nonneurovi rulent virus FB29, caused a similar disease. The disease caused by Fr9 8(E) differed from that induced by the coisogenic neurovirulent ecotro pic virus FrCas(E) in clinical presentation, histopathology, and distr ibution of virus in the central nervous system. Since Fr98(E) contains ;a polytropic envelope gene and FrCas(E) contains an ecotropic envelop e gene, these phenotypic differences appeared to be determined by enve lope sequences and may reflect differences in virus receptor usage in the central nervous system.