Selective vulnerability of neural cells to viral infections.

A number of viruses selectively infect neurons and, in some cases, specific populations of neurons. The susceptible neuron need not be permissively infected to cause acute or chronic disease; therefore, infectious virus may not be recoverable and morphologically identifiable viral structures may not be detectable by ultrastructural structures. Polioviruses and the neurotropic murine retrovirus both cause paralytic disease with major pathological changes in motor neurons of the spinal cord. Both produce disease more readily in later life; in poliovirus because the mature animals are more susceptible to acute infection, and in the neurotropic retrovirus infections because of the long incubation period of the natural infection. In the acute inflammatory poliovirus infections, the motor neurons appear to be selectively infected and lysed by the virus, whereas in the chronic noninflammatory retrovirus infection, the effect may be indirect or may result from nonpermissive infection.