L'institut Armand-Frappier

Orvo Ast

Vytautas Pavilanis

Robert Dubreuil, Deceased

The disclosure describes a process for the production of an attenuated strain of measles virus effective for the production of an attenuated measles virus vaccine. The starting material is an Edmonston strain of measles virus which has undergone a plurality of culture passages in various culture media. A sample of the last culture passage is taken and a plurality of culture passages of the sample is effected in primary cultures of fibroblasts of chicken embryos. A sample from the last culture passage is inoculated and a culture passage is effected in a primary culture of fibroblasts of chicken embryos thereby obtaining clones of virus. Clones of measles virus obtained in the last culture passage are isolated and one selects those which are thermosensitive at a temperature between about 32.degree. C. and 37.degree. C. Among the thermosensitive clones which have been selected, another selection is made of the ones with moderate cytopathic effect, and finally one isolates from the latest selection, the one which shows highest seroconversion on monkeys, thus producing an attenuated strain of measles virus.

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Pierrefonds, Canada

Orvo Ast