Serial passage

Attachments

Investigators at the Rockefeller Institute sought to attenuate yellow fever virus for vaccine production by serial passage of the virus in animal tissues, as Pasteur had done with rabies vaccine.28
It was produced by more than 500 serial passages of vaccinia virus (from a wild strain discovered by the Turkish vaccine institute of Ankara) in chicken embryo fibroblasts.
Theiler and Smith,29 at the Rockefeller Institute, subsequently found that serial passage of wild-type virus in chick embryos resulted in a viral strain attenuated in both viscerotropic and neurotropic activity.
This approach proved problematic, however, because serial passage in mouse brain tissue attenuated viscerotropic virulence but the virus became more neurotropic.