Attenuated hog cholera virus vaccine and method of producing same

Claim 1

AN ATTENUATED HOG CHOLERA VACCINE CONTAINING AN ATTERNUATED HOG CLOLERA VIRUS CAPABLE, BY GROWTH, OF INVOKING THE PRODUCTION OF ANTIBODIES AND THE DEVELOPMENT OF A SPECIFIC RESISTANCE TO AND A DURABLE IMMUNITY AGAINST HOG CLOLERA WITHOUT THE APPEARANCE OF THE USUAL SYMPTOMS OF THE DISEASE AND WHICH ELIMINATES THE DISADVANTAGES ATTENDANT TO USING EITHER INACTIVATED VIRUS VACCINES OR VIRULENT VIRUS IN COMBINATION WITH AN ANTI-SERUM, PRODUCED BY A METHOD WHEREIN THE DESIRED ATTENUATION IS EFFECTED BY SERIAL PASSAGE PROPAGATION OF VIRULENT HOLG CHOLERA VIRUS THROUGH A NUMBER OF SUCCEEDING PASSAGES IN SUCCEEDING PORTIONS OF AN ARTIFICIAL CULTURE MEDIA CONTAINING LIVING HOG TISSUE, FREE FROM HOG CHOLERA IMMUNE FRACTIONS, THEREBY ATTENUATING THE VIRUS CULTURE BEYOND THE MEASURABLE DEGREE OF ATTENUATION WHICH OCCURS ANYWHERE FROM THE 15TH ON THE 33RD PASSAGE TO THE POINT WHERE ANIMAL TESTS, MADE AGAINST CONTROLS IN THE USUAL MANNER, PROVE THAT PORTIONS THEREOF CAN SERVE AS VACCINES FOR PRODUCING A DURABLE IMMUNITY, SAID POINT, WHICH IS USUALLY FOUND IN PASSAGES 49 TO 157, BEING CHARACTERISTICALLY FOUND BY ANIMAL TESTS WHICH SHOW THE BLOOD AND SPLEEN TISSUES OF HOGS PREVIOUSLY INOCULATED WITH SUCH A MODIFIED VIRUS CULTURE EFFECTIVELY SERVE TO IMMUNIZE HOGS, CONCLUSIVELY PROVING THAT (1) THE VIRUS DID NOT INCREASE IN VIRULENCE DUE TO THE CONSECUTIVE PASSAGE THROUGH TWO PIGS; AND THAT (2) THE BLOOD AND SPLEEN TISSUES COLLECTED FROM PIGS INOCULATED WITH THE MODIFIED VIRUS CONTAIN THE MODIFIED VIRUS.