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

Abstract

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.