Abstract
In a previous note 1 we reported our inability to demonstrate an antibody response in poliomyelitis refractory animals in any way comparable to that realized in monkeys. Although antisera produced in the guinea pig, rabbit, dog, sheep and goat in some instances inactivated an equal volume of a 5% suspension of virus tissue (cord and medulla) when these sera were employed in an undiluted form, previous dilution of the serum to 1-2 (after addition of virus suspension, 1-4) failed to render such a virus suspension non-infectious for monkeys. Essentially the same results were obtained with the serum of a horse, which at the time of the previous report (June, 1930) had been given 9 intravenous injections of 50 cc. (one injection 20 cc.) each of a 10% suspension of virus material (cord and medulla) over a period of 45 days. Since the horse represented a much later addition to our series of poliomyelitis refractory animals, virus injections have been continued to make the period of “immunization” more comparable to those of the sheep and goat, which received virus injections over a period of about a year. The results with the horse have, however, proven far more gratifying than in the case of the other poliomyelitis refractory animals. Titrations carried out recently on serum procured from the horse 8 months after the “immunization” was begun indicate that the serum is now capable of inactivating an equal volume of a 5% virus suspension in a final serum dilution of 1-60, which according to the recent observation of Shaughnessy, Harmon and Gordon 2 may equal, if not exceed the antibody titer of the average human poliomyelitis convalescent serum. The antibody titer is not as high as that of some of the hyperimmunized poliomyelitis convalescent monkey sera we have titrated (1-128), but we anticipate that with further immunization of the horse the titer may rise to a higher level.
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