Poliovirus Induces Apoptosis in the Mouse Central Nervous System

Poliovirus (PV) is the etiological agent of human paralytic poliomyelitis. Paralysis results from the destruction of motoneurons, a consequence of PV replication. However, the PV-induced process leading to the death of motoneurons is not well known. We investigated whether PV-induced central nervous system (CNS) injury is associated with apoptosis by using mice as animal models. Transgenic mice expressing the human PV receptor were infected intracerebrally with either the neurovirulent PV-1 Mahoney strain or a paralytogenic dose of the attenuated PV-1 Sabin strain. Nontransgenic mice were infected with a mouse-adapted PV-1 Mahoney mutant. DNA fragmentation was demonstrated in CNS tissue from paralyzed mice by visualization of DNA oligonucleosomal laddering and by enzyme-linked immunosorbent assay. Viral antigens and DNA fragmentation detected by the in situ terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end-labeling technique were colocalized in neurons of spinal cords from paralyzed mice. In addition, morphological changes characteristic of cells undergoing apoptosis were observed in motoneurons by electron microscopy. Thus, we show that PV multiplication and CNS injury during paralytic poliomyelitis are associated with apoptosis.