Immunization of monkeys against poliomyelitis

Abstract

This work represents efforts made toward developing a practicable method of immunization against acute poliomyelitis. Highly potent monkey polio virus is attenuated by heat in two ways. In one case 5 c.c. of brain and cords in 10 per cent. saline suspension from monkey poliomyelitis is subjected to 55° C. for one half hour and injected subcutaneously into monkeys on ten successive days. This represents the use of killed virus. In the other method the 10 per cent. emulsion is subjected to graded attenuation as follows: heated to 55° C. for one half hour on first two days; to 45° C. on third day; to 37° C. on fourth day and on the fifth day the material is injected unheated.

On the 20th day after the series of subcutaneous injections are completed, the treated animals are bled from the heart in order to test for the presence of neutralizing substances in the blood. On the following day the treated animals were tested by subjecting them to three to five intracerebral lethal doses of highly potent monkey virus. The sera of the treated animals were placed in contact with equal part of 5 per cent. emulsion of monkey virus at 37° C. for two hours and then in ice box over night. On the day of intracerebral test for treated animals, the serum virus mixtures were inoculated intracerebrally into normal monkeys. The same virus emulsion was used in the test inoculations and serum virus mixtures.

The results with killed virus injection method were not so good as with that of graded attenuation. In the former method only 3 animals were used. Of these two succumbed to test inoculations with the usual incubation and the third presented a delayed incubation of 12 days, but recovered with residual paralyses of both arms and legs.