STUDIES IN RODENT POLIOMYELITIS

Abstract

Murine SK poliomyelitis virus has been transferred from mouse to guinea pig with the establishment of a fixed strain of cayian passage virus. The disease thus produced in guinea pigs is characterized by the occurrence of flaccid paralysis. Typical poliomyelitic lesions are found in the ant. horn of the spinal cord. Guinea pigs are susceptible to infection with murine virus by the intracerebral, in-traven., intraperit., and subcut. route; cavian passage virus produces paralysis only upon intracerebral or intravenous injection. Neither virus paralyzes guinea pigs by feeding or nasal instillation. The potency of the virus (murine or cavian) in guinea pigs is considerably lower than in mice and compares with the titer of the original SK strain in monkeys. In paralyzed guinea pigs the virus is found only in the central nervous system and not in extraneural sites, such as blood or abdominal viscera. Attempts to cultivate cavian passage virus in tissue culture have yielded evidence of some in vitro propagation but no passage virus has as yet been obtained by this method. Cross neutralization tests with cayian passage virus in guinea pigs and with murine virus in mice have established the serological identity of the 2 viruses. Inactivation of cavian passage virus in guinea pigs by poliomyelitis-convalescent monkey sera is irregular. Complete neutralization has been obtained with a conc. poliomyelitis horse serum. Resistance to reinfection with potent virus can be demonstrated in convalescent guinea pigs as well as in guinea pigs which have survived a symptomless infection with either murine or cavian virus. This immunity is demonstrable by the power of the serum of these animals to neutralize the virus in vitro and by the ability of nerve tissue to dispose in vivo of the infectious agent. Cavian passage virus has a limited pathogenicity for rhesus monkeys. Of a total of 35 monkeys injd. intra-cerebrally with guinea pig passage virus 26 failed to respond with any manifest symptoms of disease; 9 monkeys showed various signs of definite involvement of the central nervous system consisting of tremor, convulsions, facial palsy, localized paresis, and, in one instance, typical flaccid paralysis. Reinfection with potent SK poliomyelitis virus failed to produce paralysis in 5 of 19 symptomless monkeys. Following injn. with cavian virus the virus may be recovered from the tissues of normal monkeys but not from the tissues of convalescent monkeys shortly after a paralyzing attack of poliomyelitis due to SK or Aycock virus. Immunization of monkeys with early cavian passage virus by the subcut. route has given no clear-cut evidence of protection against intracerebral reinfection with SK poliomyelitis virus. Neither has there been any evidence of effective interference in monkeys injd. intrayen. with early cavian passage virus and intracerebrally with RMV poliomyelitis virus. The bearing of the exptl. data upon the epidemiology of the human disease is discussed.