LIVE ORAL POLIOMYELITIS VACCINE
PREPARATION AND SELECTION OF CANDIDATE SEED VIRUS FROM SABIN'S TYPE 1 VIRUS
1979 Volume 29 Issue 1 Pages 31-44
Details
1979 Volume 29 Issue 1 Pages 31-44
A candidate type 1 working seed virus was selected from the newly prepared SOM+1 (one passage progeny of the virus prepared by the Merck, Sharp and Dohme Research Laboratories from Sabin original virus) viruses, which were excellent in rct characters, as well as their progeny vaccine-level viruses. Monkey neurovirulence, rct characters, and genetic stability through passages in vitro were compared between the vaccine-level virus derived from the candidate seed and one of the authors' type 1 vaccines which had been released for practical use and proved to be good in the routine administration. As a result, the selected candidate virus was a little superior to the former seed in producing a vaccine of high quality.
Another comparison was made between the selected candidate virus and a virus derived from an SOM's clone. It indicated that thermosensitivity was considerably higher in the clone-derived seed and its progeny viruses than in the selected candidate seed (SOM+1) and its progeny vaccine (SOM+2) viruses, as revealed in the rct test. Comparative intraspinal monkey neurovirulence tests were conducted on each of the vaccine-level viruses made from both parent seeds. In them the clone-derived virus caused histological poliomyelitic changes to spread over the spinal cord and brain stem that were remote from the site of inoculation. No implication of this result is yet known.
The authors' past vaccines showed a good efficacy and safety. It is highly probable that vaccine virus of too high thermosensitivity may reduce immune responses. Taking these points into consideration, it may be concluded that it is safe to select a virus as a candidate working seed which will yield vaccine viruses to the same extent as, or a slightly larger extent than, the preceding vaccine lots with regard to rct characters. This selection should also be made on the basis of the satisfactory results of the monkey neurovirulence test.
