Sporadic appearance of paralytic spongiform neurodegeneration in a colony of inbred mice is associated with CNS retrovirus expression

Abstract Exogenous and endogenous retroviruses (RV) have been known to induce vacuolar central nervous system neuropathology. Two mice which were juvenile inbred Rocky Mountain White (IRW), showed signs of spontaneous degenerate motor neuron disease. Signs included wasting, unkempt fur, adduction reflex upon tail elevation, kyphosis, and stilted gait by postnatal day 18 (P18). Brains and spinal cords were examined with H&E staining and stained with a broadly reactive retrovirus antibody. When compared to brains of mice with normal vacuolar pathology as well as mice infected with prototypic non-neurovirulent RV, Fr57E and prototypic neurovirulent RV FrCasE, the subject showed less severity but were clearly distinguishable from the non-virulent RV. Spongiosis was seen in the motor areas in both mice. Immunohistochemical staining showed reactive retroviral antibodies, which is evidence of viral protein expression in glia and endothelia. The type of RV present will take further investigation. The ability for spontaneous appearance of competent RV replication arising from endogenous RV in mice that also can induce neurological disease are highlighted. Similar spontaneous retroviral gene expression in humans have been attributed to diseases such as multiple sclerosis and amyotrophic lateral sclerosis. Understanding the viral re-emergence will shed light on the cause of human and animal retroviral disease