PHENOTYPIC ANALYSIS OF YELLOW-FEVER VIRUS DERIVED FROM COMPLEMENTARY-DNA

A thorough phenotypic characterization of yellow fever (YF) virus gene rated from cDNA is a necessary prerequisite for mapping virulence/atte nuation determinants and exploring the potential of YF attenuated viru s 17D as a carrier for heterologous protective epitopes. In this study , YF virus was produced from 17D cDNA clones after lipofectin-mediated RNA transfection of certified primary cultures of chicken embryo fibr oblasts (YFiV5.2/SL). This virus was passaged once in embryonated chic ken eggs according to current YF vaccine manufacture methodology to pr oduce the experimental virus (YFiv5.2/VL). These viruses were characte rized in established monkey neurovirulence safety tests and quantitati ve clinical and histologic scores were derived for each virus. The exp erimental vaccine viruses (YFiV5.2/SL and VL) compared favorably with another well-known YF vaccine strain (17DD) used as control virus for the histologic score. Although slightly higher clinical neurovirulence was observed for YFiv5.2 as compared with the 17DD virus, it should n ot preclude the use of YFiv5.2 for mapping YF virus virulence determin ants.