ABSTRACT
Four geographic variants (topotypes) of yellow fever (YF) virus from Africa and South America previously determined by RNA oligonucleotide mapping were analyzed for their structural, antigenic and virulence characteristics. The electrophoretic migration mobility and carbohydrate content of the envelope protein E characterized YF virus strains of South America. The NS 1 protein of South American and Central African YF virus strains was not precipitated by anti-NS 1 monoclonal antibodies (MAB) that precipitated NS 1 of West African strains. No distinction could be made among the YF virus strains on the basis of the neutralizing capacity of available MAB. South American, but not African YF virus strains were virulent for 8-day-old mice upon intraperitoneal inoculation. The results permitted characterization of topotypes of Central Africa and South America but failed to differentiate YF strains from West Africa.