Activation of divergent neuronal cell death pathways in different target cell populations during neuroadapted sindbis virus infection of mice

Infection of adult mice with neuroadapted Sindbis virus (NSV) results in a severe encephalomyelitis accompanied by prominent hindlimb paralysis. We fi nd that the onset of paralysis parallels morphologic changes in motor neuro n cell bodies in the lumbar spinal cord and in motor neuron axons in ventra l nerve roots, many of which are eventually lost over time. However, unlike NSV-induced neuronal cell death found in the brain of infected animals, th e loss of motor neurons does not appear to be apoptotic, as judged by morph ologic and biochemical criteria. This may be explained in part by the lack of detectable caspase-3 expression in these cells.