Factors affecting induction of neurological disorder in mice by PVC viruses and the sequence of ENV-LTR region of PVC441

PVC111, PVC211, PVC321 and PVC441 cause neurological disorders associated with tremor and paralysis in rats. We tested the pathogenicity of these viruses in mice. Although histopathological studies revealed spongiform degeneration in the spinal cords of NFS mice infected with each PVC virus, only PVC441 caused a high incidence of tremor and paralysis. Further studies with PVC441 revealed dose and age dependence for tremor induction. In contrast to NFS mice, BALB/c, DBA/2 and C57BL/6 mice infected with PVC441 virus showed no neurological symptoms, although the virus replicated in each strain to titers within 5-fold of the titer in NFS mice. Despite absence of neurological symptoms, high degree of neuronal degeneration in the lumbar spinal cord was found in PVC441-infected BALB/c mice. Low degree of neuronal degeneration was found in PVC441-infected DBA/2 or C57BL/6 mice. Genetic crosses of these resistant mice with susceptible NFS mice indicated that resistance to PVC441-induced tremor induction was dominant in all strains and suggested that various host genes may control the susceptibility of mice to tremor induction by PVC441 virus. Sequencing of env-LTR region of PVC441 revealed an intermediate character between PVC211 and F-MuLV.