Study of Yellow Fever Vaccine Viruses With Monoclonal Antibodies.

This thesis describes the antigenic and biological analysis of 31 yellow fever (YF) vaccine viruses from three different vaccine strains (17D-204, 17DD and the French Neurotropic Vaccine [FNV]) using panels of monoclonal antibodies (McAbs). The antigenic specificity and biological function of the epitopes recognised by the McAbs were identified. Two YF-type specific and one flavivirus group reactive McAbs were identified while the remainder were partial flavivirus group reactive. Four panels of McAbs were used together with polyclonal anti-sera to antigenically analyse the envelope (E) protein epitopes on YF viruses using haemagglutination inhibition assays (HAI) and plaque reduction neutralisation tests (PRNT’s). Heterogeneity in the biological function of the E-protein epitopes was demonstrated. Using the technique of cluster analysis a dendrogram was produced which divided all YF viruses into three groups. McAb neutralisation escape variants were produced to examine the function of particular epitopes in detail. One 17D-204 sub-strain specific epitope was found to affect the neurovirulence of YF 17D-204 vaccine virus for mice. The new 17D YF vaccine virus manufactured in the Union of Soviet and Socialist Republics (USSR) was examined in detail. The vaccine was indistinguishable from other 17D vaccines with the majority of McAbs. However, pathogenicity studies showed that the vaccine contained virions which killed mice with a reduced average survival time compared to other 17D vaccines. Three FNV vaccine viruses were studied in HAI assays, PRNT's and pathogenicity tests. In HAI assays they were indistinguishable, while PRNT’s and pathogenicity studies were able to distinguish between them. The 17DD sub-strain vaccine viruses and their wild-type parent strain Asibi were found to be temperature sensitive when grown in the mosquito C6-36 cell line and not the human SW13 cell line. No evidence was found to associate this phenotype with epitopes on the E-protein