Abstract
Work on the nature of virus-antiserum combinations has indicated that although the virus in such mixtures is completely inactivated, the effect on the virus is not a destructive one, but more in the nature of a “neutralization” phenomenon. It is possible to recover active virus from neutral virus-serum unions by such means as dilution, and cataphoresis. 1 , 2 , 3 , 4 , 5 It is therefore not surprising that mixtures of virus neutralized by serum have been shown to possess antigenic properties. 6 , 7 , 8
Utilizing these facts, with a view toward ultimate development of a safe and practical method for active immunization against poliomyelitis, applicable to humans, investigations were undertaken to determine the conditions under which a high incidence of immunity could be obtained in the experimental animal.
To that end, 2 series of animals, whose serums had previously been tested by the neutralization test to rule out the presence of neutralizing substance, were inoculated subcutaneously and intramuscularly, with neutralized mixtures. In the first series, varying proportions of virus and serum, the potencies of which were only roughly approximated, were used. The second series of animals received inoculations of accurately neutralized mixtures based on careful titrations of virus and serum. Two such balanced mixtures of serum and virus were used in this series; one containing 16 cc. of 5% virus suspension to 1 cc. of human convalescent serum, the other mixture containing 20 cc. of virus to 1 cc. of serum.
Since the purpose of this attempt at immunization was to determine the number of animals that would give a demonstrable response following injection of neutralized mixtures of virus and serum of known titre, the neutralization test was selected as the most desirable criterion for immunity. This is in accord with conclusions reached by Stewart and Rhoads 9 and by Brodie and Goldbloom, 10 that the neutralization test (using small doses of virus) is a more sensitive test for immunity than is the intracerebral test.
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