Патент USA US2136131код для вставки
Patented Nov. 8, 1938' 2,136,131 ‘UNITED STATES PATENT OFFICE 2,136,131 DISTEMPER VACCINE AND METHOD OF . PREPARING THE SAME ‘ :n Robert G. Green, Minneapolis, Minn. No Drawing. Application March 9, 1937, Serial No. 129,955 6 Claims. (Cl. 167-78) The vdistemper virus,’ discovered by .Carré, and extensively investigated by Laidlaw and Dunkin, resulting vaccine was found to produce a mor tality of’only about 30% and those animals dying generally is believed to be the sole cause of canine succumbed suddenly after about 14 days withouj distemper in dogs, foxes, and other susceptible ‘showing the typical symptoms of distemper ex % 5 animals, and has been widely distributed and cepting for a few hours before death.‘ 5 extensively used for the production of vaccines, serums and materials for diagnosis. An object of the present invention is the prepa ration, from the virus of canine distemper, of mortality rate due to the use of the vaccine de creases until at about 30 generations the mor tality rate is only about 3%. By employing a a modi?ed virus or vaccine for use in the immu larger number of generations and by employing 10 nization of foxes and dogs against distemper. The principal desirable properties of such a vac - cine are that it shall be safe to use and produce a high degree of immunity in the animals treated. I have discovered that by passing the ?lterable virus of Carré, e. g. commercially available dis temper virus, such as the so-called Laidlaw Dunkin virus or a virus obtained in the usual and well-known manner from an animal such as a fox having natural distemper, serially through ferrets, it may be so modi?ed or its na ture changed that it safely may be administered in the living state. The virus is so changed in nature by each generation or passage through a ferret that after a serial passage of a sum ciently large number of generations it is found - to have gradually lost its pathogenic properties - As the number of generations is increased the other expedients such as the use of the resulting modi?ed virus in attenuated form produced, for instance, by drying or other known or usual method of attenuation, or by the use of the modi~ ?ed virus or vaccine with serum, the mortality 15 rate may be reduced to a negligible ?gure. In a typical instance the serial passage of the virus through ferrets was accomplished by ?rst injecting 1 cc.- of a 5% spleen emulsion from a fox which had died of typical distemper into 20 a plurality of ferrets. These ferrets sickened and were killed on the 12th day after the inocula tion and their spleens used in the preparation of a 5% emulsion, 1 cc. of which was injected into ' another group of ferrets. This procedure .was 26 continued for the desired number of generations, the vaccine produced at each 5 generations being for foxes and dogs and instead of severe or fatal tested for its effect on foxes. ~ infections it produces only mild infections, clini- ' A combined vaccine and serum treatment pre cally dissimilar to typical distemper and with a ferred for use on young animals, both foxes and 30 low mortality rate, and the animals which have dogs, on account of their lower natural resist been inoculated with the modi?ed virus are ren ance, consists in simultaneously injecting ,the dered immune to typical distemper. animal with a suitable dose, say 1 cc. of a 5% The serial transmission through ferrets is ac 35 complished by inoculating a ferret with active spleen emulsion containing the modi?ed ilrus and a suitable dose, say 10 cc. of standard vntl- 35 distemper virus and when the ferret sickens or serum. This simultaneous injection is followed dies using infected tissue from it to infect an at intervals of between one and two weeks with other ferret and so on for a su?icient number one or more further injections of the modi?ed of generations to produce .the desired degree of 40 modi?cation of the virus. By actual test it has been found that after from 5 to 10 generations the original virus has been slightly but de?nitely modi?ed and its ability to produce typical dis temper in foxes de?nitely reduced. After 20 45 generations the modi?ed virus or vaccine usually produces no demonstrable symptoms of distem per in foxes, tested in groups of as many as ten. Regardless of the number of generations, within reasonable limits infection of foxes with the re 50 sulting vaccine results in immunity to typical distemper. ’ Speci?cally, commercial dog distemper virus injected into foxes was found to produce a mor¢ tality of about 60%, whereas after about 10 gen [5 erations of the virus serially through ferrets the virus or vaccine alone until complete immunity against typical distemper has been established. 40 The serum for use in the foregoing treatment may be prepared by standard procedure, e. g. by giving immune dogs or foxes several inJec tions of virus at suitable intervals and using the blood of the animal for the preparation of the 45 serum. I ., It is observed that the preparation of the distemper vaccine described above is analogous to the known preparation of vaccine for small pox in which virulent virus of human smallpox 50 is modi?ed and rendered innocuous by serial pas sage through calves or rabbits. Not all viruses, , however, are capable of beingmcdi?ed in this manner and one cannot predict this ‘property in a virus or predetermine what animal will serve 55 2 2,186,181 typical canine distemper for at least ten genera for the modification. Moreover, it was not pre dictable that the serum treatment described tions serially through ferrets. 3. _Method 0! modifying distemper virus for the above would exert a protective e?ect by simul taneous injection in an animal inoculated with production of a vaccine capable when injected into foxes oi immunizing the same against typi the modi?ed virus or vaccine. The modi?ed virus produced in accordance cal distemper which comprises passing the virus with the present invention may be used in the or typical canine distemper for at least thirty known manner or in accordance with well, generations serially through ferrets. 4. A distemper vaccine comprising distemper established practice for the production of vac virus modi?ed by serial passage through ferrets 10 cines, serums and materials for diagnosis and 10 for a su?icient number of passages to materially may be used in a variety or ways. The inven tion embraces the modi?cation oi the virus by reduce the normal distemper death rate 01' foxes‘ any number of passages, two or more. through indected therewith, said vaccine being capable oi! ferrets, and the resulting products. I claim: 1. Method of modifying distemper virus for the production of a vaccine capable when in jected into foxes of immunizing the same against typical distemper which comprises passing the 20 virus of typical canine distemper serially through ierrets for a su?lcient number 0! passages to materially reduce the normal distemper death rate or foxes injected therewith. 2. Method of modifying distemper virus for the production of a vaccine capable when injected into foxes oi immunizing the same against typical distemper which comprises passing the virus of immunizing foxes against typical canine dis temper. . 5. A distemper vaccine comprising distemper virus modi?ed by serial passage for at least about ten generations through ferrets, said vaccine be ing capable of immunizing foxes against typical canine distemper. - _ I 20 6. A distemper vaccine comprising distemper virus modi?ed by serial passage for at least about thirty generations through ferrets, said vaccine being capable of immunizing ioxes against typi cal canine distemper. 25 aonna'r a. cam.