[Analysis of dissemination pathways for poliovirus].

Poliomyelitis is an acute disease of the central nervous system (CNS) caused by poliovirus (PV). In humans, an infection is initiated by oral ingestion of the virus, followed by multiplication in the alimentary mucosa, from which the virus spreads through the bloodstream. Paralytic poliomyelitis initiates from the invasion of the central nervous system by circulating poliovirus, probably via the blood-brain barrier. After the virus enters the central nervous system, it replicates in neurons, especially in motor neurons, inducing the cell death that causes paralytic poliomyelitis. Along with this route of dissemination, a neuron-specific pathway has been reported in humans, monkeys, and PV-sensitive transgenic (Tg) mice carrying the PV receptor (hPVR/CD155) gene. It is important for the efficient virus dissemination to overcome the barriers as follows; i) to access the target tissue, ii) to enter the cells, iii) to reach the place for the replication, iv) to replicate efficiently. PV is easily transferred to humans orally; however, no rodent model for oral infections has been developed. We analyzed the each barrier above, and showed that PV is inactivated by the low pH of the gastric contents in mice. We also demonstrated that type 1 interferon signaling plays an important role in determining permissivity in the alimentary tract. As for the neural pathway, we demonstrated that direct efficient interaction between the cytoplasmic domain and cytoplasmic dynein is essential for the efficient retrograde transport of PV-containing vesicles along microtubules for the hPVR-dependent PV transport. On the other hand, we found that hPVR-independent axonal transport of PV was also observed in hPVR-Tg and non-Tg mice, indicating that several different pathways for PV axonal transport exist.