GB738454A - Improvements in or relating to the production of poliomyelitis virus vaccine - Google Patents

Abstract

A poliomyelitis virus vaccine for immunizing primates is prepared by modifying poliomyelitis virus by serial passage in suckling rodents until it has become adapted to grow in chick embryos, inoculating chick embryos with said modified poliomyelitis virus and after a period of incubation in said chick embryos, harvesting the embryonic tissue and recovering the poliomyelitis virus therefrom; continuing the steps of inoculation, incubation and harvesting until the virus is modified so that it may be administered to primates by oral ingestion without causing illness but with the production of protective antibodies and then preparing the poliomyelitis vaccine from the harvested embryonic tissue of the final passage. A poliomyelitis virus which will propagate in the central nervous tissue of rodents is obtained (a) from the American Type Culture Collection, or (b) by serial passage of a specified strain through mice and then hamsters of 6 to 8 weeks. An aqueous suspension of the modified virus is inoculated intracerebrally into suckling rodents, preferably of 1 to 12 days old, and just prior to the time when they show evidence of paralysis, i.e. when the virus titre is at a maximum, the rodents are sacrificed and a suspension, usually isotonic, is made of their central nervous tissue. This suspension is inoculated intracerebrally into other suckling rodents and serial passages through suckling rodents are made until the LD50 mouse titre of the virus suspension is at least 10-5. The virus is then propagated serally in chick embryos, especially 7-day-old chick embryos with incubation at 37 DEG C. for 7 days, until the virus has been modified sufficiently to be safely used on humans, as shown by tests with monkeys. A live virus vaccine may be prepared by grinding the chick embryonic tissue in isotonic saline solution or Ringer's solution and centrifuging to remove gross tissue, if desired. It may be taken orally alone or in admixture with food such as milk or chocolate. A killed poliomyelitis virus vaccine is obtained by treating the live virus vaccine with an inactivating agent such as phenol, formalin or ethylene oxide. A diagnostic antigen is obtained by drying the killed virus vaccine, extracting the dried material with a fat solvent and adding saline solution to the extracted product.