Preparation and biochemical characterization of Lassa virus subvirion fractions.

14C-labelled Lassa virus was purified by isopycnic centrifugation and split to subvirion fractions. The purified virus was treated with nonionic detergents Nonidet P-40 (NP-40) and with octylglycoside. After ultracentrifugation in urographin density gradient, two subvirion fractions with buoyant density of 1.24-1.26 and 1.08-1.10 g/cm3 were obtained. The first fraction corresponded to the nucleocapsid of Lassa virus: it contained a protein with molecular mass of 60 kDa, the L and S segments of the genomic RNA. The second one contained a protein with molecular mass of 48 kDa and represented, apparently, envelope fraction of virus particles.