Immune Serum Production in Poliomyelitis Refractory Animals. ∗

Several investigators have reported the production of antipoliomyelitis serum in poliomyelitis refractory animals. Thus, Kraus 1 and likewise Pettit 2 claim to have been able to produce a viricidal serum in sheep, while more recently Neustaedter and Banzhaf 3 Pettit, 4 Weyer, Park and Banzhaf, 5 and Fairbrother 6 have reported similar results with the serum of horses immunized with virus material from monkeys. The observations of other investigators (Flexner, 7 Stewart and Haselbauer 8 ) have not supported the view that refractory animals are serviceable for the production of antipoliomyelitis serum. We began in 1928 to make a careful study of the capacity of various refractory animals to produce viricidal sera against this virus. The animals used include the guinea pig, rabbit, dog, goat, sheep and horse. These animals received injections of virus material (ground cord and medulla) from poliomyelitis monkeys, administered by various routes, at short intervals of time over periods ranging from several months for some of the animals to more than a year for others (sheep). The sera of these animals have been tested for viricidal properties in the customary manner, except that we aimed to subject the supposedly immune sera to somewhat more severe tests than those described by previous workers. Our method in setting up the viricidal test has been to add to a given volume (1 cc.) of a 5% suspension of virus cord (very finely ground in a machine, 9 lightly centrifuged and filtered through filter paper) to an equal volume (rather than 9 times the volume) of the undiluted immune serum. This mixture was incubated for 2 hours at 37° C. and injected in doses of 1.5 cc. into the frontal lobe of the brain of a monkey. Certain of the immune sera so produced were compared with monkey convalescent serum by titrating them against the same virus suspension.