Poliomyelitis as a consequence of poliovirus infection is observed only in primates. Despite a host range restricted to primates, experimental infection of rodents with certain genetically well defined poliovirus strains produces neurological disease. The outcome of infection of mice with mouse-adapted poliovirus strains has been described previously mainly in terms of paralysis and death, and it was generally assumed that these strains produce the same disease syndromes in normal mice and in mice transgenic for the human poliovirus receptor (hPVR-tg mice). We report a comparison of the clinical course and the histopathological features of neurological disease resulting from intracerebral virus inoculation in normal mice with those of murine poliomyelitis in hPVR-tg mice. The consistent pattern of clinical deficits in poliomyelitic transgenic mice contrasted with highly variable neurologic disease that developed in mice infected with different mouse-adapted polioviruses. Histopathological analysis showed a diffuse encephalomyelitis induced by specific poliovirus serotype 2 isolates in normal mice, that affected neuronal cell populations without discrimination, whereas in hPVR-tg animals, damage was restricted to spinal motor neurons. Mouse neurovirulent strains of poliovirus type 2 differed from mouse neurovirulent poliovirus type 1 derivatives in their ability to induce CNS lesions. Our findings indicate that the characteristic clinical appearance and highly specific histopathological features of poliomyelitis are mediated by the hPVR.(ABSTRACT TRUNCATED AT 250 WORDS)