Murray Sanders

STUDIES IN RODENT POLIOMYELITIS : I. FURTHER EXPERIMENTS WITH THE MURINE STRAIN OF SK POLIOMYELITIS VIRUS.

1. SK murine virus maintained over more than 200 serial mouse passages increased in virulence for mice from an initial intracerebral titer of about 1:1 million to a maximum titer of not less than 1:1 billion dilution activity. 2. Following intracerebral injection with murine virus of remote mouse passages, 5 of 13 rhesus monkeys developed a characteristic encephalitic syndrome. Repeated intravenous injection of massive doses of virus caused localized flaccid paralysis in 2 of 14 monkeys. 3. Intracerebral injection of graded doses of murine virus into mice of different age groups caused fatal paralysis in young and old animals alike. Infection with small doses of virus by peripheral routes, while uniformly fatal to young mice, was followed by survival of almost half of the old mice. 4. The incubation period of the disease in young mice infected intracerebrally with a standard dose of murine virus, when studied throughout the period of 1 year, was found considerably lengthened during the summer months. 5. Cross neutralization tests furnished no evidence for any serological relationship between SK murine virus and lymphocytic choriomeningitis virus. Theilers virus was found to be neutralizable by antimurine horse serum and, to a lesser extent, by concentrated antipoliomyelitis horse serum; however, such inactivation, in both cases, was distinctly inferior to that occurring with SK murine virus. On the other hand, no neutralization whatsoever was obtained between SK murine virus and normal adult mouse serum, whereas the same serum completely neutralized Theilers virus. Mice surviving infection with Theilers virus, though acquiring immunity to this virus, remained fully susceptible to reinfection with SK murine virus. 6. Neutralization tests with SK murine virus against poliomyelitis-convalescent monkey sera gave irregular results, but neutralization of murine virus occurred regularly with a hyperimmune antipoliomyelitis horse serum. Hyperimmune antimurine horse and rabbit sera, on the other hand, failed to inactivate three strains of monkey poliomyelitis virus (SK, RMV, Aycock) by intracerebral tests in monkeys. The same sera inactivated murine virus in mice by intraperitoneal, but not by intracerebral injection of virus-serum mixtures. 7. The identity of SK murine virus and its relation to other rodent strains of poliomyelitis virus is discussed on the basis of the available data.

Isolation of a Murine Neurotropic Virus by Passage of Monkey Poliomyelitis Virus to Cotton Rats and White Mice.

Armstrong 1 2 3 reported apparent transmission of poliomyelitis (Lansing strain) from the monkey to the Eastern cotton rat and to white mice. This report deals with attempts to adapt other strains of poliomyelitis virus to these rodents. Cotton rats (Sigmodon hispidus littoralis) were infected intra-cerebrally with 5 recognized strains of monkey poliomyelitis virus (RMV, Aycock, Philadelphia, ST Los Angeles, SK New Haven). None of the animals injected with the first 4 strains showed any abnormal symptoms. However, of 2 cotton rats injected with the SK‡ strain 1 died the following day, evidently of trauma; the other one succumbed one week later without observed symptoms. No lesions were present except a markedly congested brain, sterile upon aerobic and anaerobic cultivation. Intracerebral transfer of this brain to another cotton rat resulted in mild nervous symptoms within 2 days, and death the next day. Further passage of the brain of the second cotton rat produced in a third cotton rat flaccid paralysis of both hind legs on the 6th day, followed by death 24 hr later. From the last 2 cotton rats intracerebral transfers of brain suspensions were made to groups of white mice. All injected mice developed complete flaccid paralysis of the hind legs, within 3 or 4 days, followed by generalized paralysis and death. Subsequent attempts to reproduce passage from monkey to cotton rats and white mice with the original material were unsuccessful. Mouse virus, however, since its isolation, is transmissible from mouse to mouse in an unbroken series. At the time of this writing, i. e., April 24th, 1940, the virus is in its 23rd passage. Over 2500 mice have been inoculated; excepting those injected with virus known to be inactivated or impotent all mice have developed the same characteristic symptoms, with only an occasional recovery, to wit: flaccid paralysis (unilateral or bilateral) of hind legs, seldom of forelegs, occasional encephalitic syndrome, death.

STUDIES IN RODENT POLIOMYELITIS : III. EXPERIMENTAL POLIOMYELITIS IN GUINEA PIGS PRODUCED WITH THE MURINE STRAIN OF SK POLIOMYELITIS VIRUS.

1. Murine SK poliomyelitis virus has been transferred from mouse to guinea pig with the establishment of a fixed strain of cavian passage virus. 2. The disease thus produced in guinea pigs is characterized by the occurrence of flaccid paralysis. Typical poliomyelitic lesions are found in the anterior horn of the spinal cord. 3. Guinea pigs are susceptible to infection with murine virus by the intracerebral, intravenous, intraperitoneal, and subcutaneous route; cavian passage virus produces paralysis only upon intracerebral or intravenous injection. Neither virus paralyzes guinea pigs by feeding or nasal instillation. 4. 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. 5. 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. 6. Cross neutralization tests with cavian passage virus in guinea pigs and with murine virus in mice have established the serological identity of the two viruses. Inactivation of cavian passage virus in guinea pigs by poliomyelitis-convalescent monkey sera is irregular. Complete neutralization has been obtained with a concentrated poliomyelitis horse serum. 7. 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 such animals to neutralize the virus in vitro and by the ability of nerve tissue to dispose in vivo of the infectious agent. 8. Cavian passage virus has a limited pathogenicity for rhesus monkeys. Of a total of 35 monkeys injected intracerebrally with guinea pig passage virus 26 failed to respond with any manifest symptoms of disease; 8 monkeys showed various signs of definite involvement of the central nervous system consisting of tremor, convulsions, facial palsy, and localized pareses; 1 monkey developed typical flaccid paralysis. 9. Following injection 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. 10. Immunization of monkeys with early cavian passage virus by the subcutaneous 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 injected intravenously with early cavian passage virus and intracerebrally with RMV poliomyelitis virus. 11. The bearing of the experimental data upon the epidemiology of the human disease is discussed.

Titration and Neutralization of the Western Strain of Equine Encephalomyelitis Virus in Tissue Culture.

Conclusion Titration of potency of W.E.E. virus and quantitative estimation of neutralizing antibodies in hyperimmune horse serum have been demonstrated by use of tissue cultures. The in vitro method of detecting the presence of virus appeared to (be more sensitive than intracerebral mouse inoculation.