Differences in the Degree of Infectiousness of two Related Strains of Poliomyelitis Virus Following their Oral Administration to Monkeys,

Summary Although belonging to the same antigenic type of poliomyelitis virus, the Lansing and Y-SK strains differ in their capacity to produce antibodies in cynomolgus monkeys by the oral route. Of 21 monkeys fed Lansing virus, none developed antibodies. On the other hand, of 20 monkeys fed Y-SK virus, one evidenced paralysis and, of the remaining 19 animals without obvious paralytic disease, 12 developed antibodies. Following the repeated feeding of the Lansing strain of poliomyelitis to 6 cynomolgus monkeys, antibodies failed to appear. When these same monkeys were subsequently fed the Y-SK virus, antibodies were found in the sera of 5 of the 6 animals. Six cynomolgus monkeys fed heat-inactivated Lansing followed by heat-inactivated Y-SK virus did not develop antibodies. These experiments would seem to point to a difference in the peripheral invasiveness of these two immunologically related strains.