7 Poliovirus Receptors

Poliovirus (PV) is the etiological agent of poliomyelitis, an acute human disease of the central nervous system (CNS). Invasion of PV into the CNS results in the destruction predominantly of motor neurons, leading to paralysis. Poliomyelitis, however, is a rare complication of PV infections of humans. The virus proliferates mainly in cells of the oropharyngeal and enteric tract, from where it can spread to the CNS. Neither the precise nature of cells in which the virus primarily replicates in the natural host, nor the route by which the virus enters the CNS has been elucidated. Viremia is frequent and can lead to infection of monocytes (Freistadt et al. 1993). It is likely that invasion of the CNS occurs both by overcoming the blood/brain barrier (Freistadt et al. 1993) and by retrograde axonal migration in neurons (Ren and Racaniello 1992a). Only humans are known natural hosts of the virus, although monkeys can be infected orally with high doses of PV leading to poliomyelitis (Wenner et al. 1959). Whereas the tissue tropism of PV is predominantly governed by the presence of a cellular receptor (Holland 1961), it is likely that other factors, such as auxiliary proteins (Barnert et al. 1992; Shepley and Racaniello 1994; Shepley, this volume) or intracellular restrictions, influence the susceptibility of tissue cells to viral infection. Available evidence all but rules out the possibility that PV can make use of more than one receptor entity, the human poliovirus receptor (hPVR), to enter cells of human origin. PV is a...