Active Immunization in Monkeys Against Poliomyelitis with Germicidally Inactivated Virus

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Abstract
Summary and Conclusions: Of interest in the present work is the resistance of the virus of poliomyelitis to the action of ether, as contrasted with that of rabies virus (12f;22). The infectivity of poliomyelitis cord tissue after ten days of contact with 1 per cent phenol is in keeping with the results of other workers (7, 23). These experiments demonstrate that a proper dose of formalized virus may produce, in the majority of monkeys, an active immunity sufficient to enable them to withstand intracerebral inoculation of one or more infective doses of virus, and that virus treated with formalin is a better antigen than is phenolized virus. This latter observation is in agreement with Andervonts' (18b) results for herpes virus and with the work of Bedson and Maitland (17b) for the virus of foot-and-mouth disease. The best immunizing dose was found to be 5 cc. of a 10 per cent suspension of infective cord tissue having an m.c.p. dose of 0.0003 to 0.0006 cc. of a 5 per cent suspension. Of 3 animals which received 2.5-cc. amounts of formalized virus, only 1 had demonstrable tissue immunity. All 3 animals had neutralizing substances in their serums. Of 12 animals given 5-cc. amounts of formalized antigen, 2 failed to show any tissue immunity and 2 had a slight degree of immunity. Seven of the remaining 8 showed an immunity equal to or better than that developed by animals which received a similar amount of active virus, better than that of animals recovered from a mild attack of the disease and comparable with that developed by some of the convalescent monkeys showing residual paralysis. All but 1 animal showed neutralizing substances in their serums. Two of 11 animals inoculated with 10-cc. amounts of formalized virus failed to show a demonstrable tissue immunity. Only 2 of the remaining 9 showed resistance to direct intracerebral inoculation of virus comparable with that of the majority of animals which received 5 cc. of the same material. Humoral immunity was present in the serums of all but 2 animals. The were certain differences in the immunological response of animals to active and formalized virus: The degree of immunity in the case of active virus was proportioned to the size of the immunizing dose, the optimum response being obtained with 10-cc. amounts. On the other hand, using formalized virus, this was not definite, for 5-cc. seemed as good as 10-cc. amounts.With active virus, the degree of humoral immunity was decidedly higher than that of tissue immunity, as demonstrated by a comparison between the number of infective doses of virus neutralized by the animal's serum and the number the animal resisted by intracerebral inoculation. Therefore, as previously suggested (2), humoral immunity is more easily detected than is tissue immunity. With the use of inactivated virus, although the degree of tissue immunity of some equalled that obtained in those cases where active virus was the antigen, the neutralizing power of the serum was decidedly lower than with active virus. Moreover, occasionally, in animals immunized with formalized virus, the tissue resistance was greater than the content of neutralizing substance of the serum. In the case of active virus there is usually a correlation between the humoral and tissue immunity, which relationship was not evident in the case of formalized antigen. Normal cord tissue fails to induce the production of neutralizing substances for the virus of poliomyelitis (1). This tends to rule out the possibility that the higher neutralizing power produced with active virus may be due in part to a non-specific substance produced in the animal in response to the injection of normal cord tissue and which is rendered inert by formalin.Two doses of active virus, when properly spaced gave decidedly better immunity than did a single dose (1). In the few experiments recorded here, using formalized antigen, the two doses did not seem superior to a single dose. This however, requires further confirmation.

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