Sucrose gradient velocity centrifugation, polyacrylamide gel electrophoresis and RNA-RNA hybridization were used to characterize Lassa and Machupo virion RNAs as well as virus-specific RNAs from cells infected with Pichinde and Machupo viruses. Five RNA species: 30-31S, 28S, 22-24S, 18S and 4-6S have been detected in Lassa, Machupo, and Pichinde virion RNAs. Among them 28S, 18S and 4-6S RNAs cosediment and comigrate with respectively cell RNAs. RNase resistance analyses suggest the presence of extensive secondary structures and complementary RNAs in Lassa, Machupo, and Pichinde virion RNAs. Annealing with poly(A)-containing RNA from infected cells has revealed that the bulk of "minus" strands of Machupo virion RNA is located in 22-24S and 28-31S fractions of sucrose gradient. Thus Machupo and Lassa viruses as well as Pichinde virus contain two genomic RNA fragments: "large" (molecular weight of about 2.2 X 10(6] and "small" (molecular weight of about 1.3 X 10(6]. In the cells infected with Pichinde virus and treated with actinomycin D (1.0 microgram/ml) synthesis of 18S, 22-24S and 30-31S RNAs has been registered. At least 22-24S and 30-31S classes comprise "plus" and "minus" strands. In cells infected with Machupo virus in the presence of actinomycin D the synthesis of similar sedimentation classes of RNAs and certain amounts of 28S RNA have been detected.

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The most abundant protein in purified Machupo virions (Corvallo strain) labelled with 14C-Protein hydrolysate is a 64 K polypeptide which is associated with virion RNAs. Another structural polypeptide, 37 K, solubilized by nonionic detergent seems to be a major surface glycoprotein. In addition to this, a 78 K polypeptide and a minor 50 K polypeptide have been detected. In Machupo virus infected cells three virus-specific polypeptides similar in size to those described for structural polypeptides were immunoprecipitated with anti-Machupo virus serum. The most abundant virus-specific polypeptide was nonglycosylated (64 K, NP), and the others were glycosylated polypeptides (78 K and 37 K). The synthesis of NP and 78 K polypeptides was recognized at the beginning of a log phase of virus replication. Pulse-chase experiments as well as experiments with an arginine analogue, canavanine (to block proteolytic processing) suggest that 78 K is a precursor for structural glycoproteins of Machupo virions.

Cell-associated proteins of rodent (CG-1820 strain) and human (K-27 and 360 strains) hantaviruses isolated in the European endemic areas of the U.S.S.R. are antigenically similar as revealed by immunoprecipitation and immunoblotting assays. Nucleocapsid-associated RNAs of representative hantaviruses of four antigenic groups [Sugiyama et al. (1987) J Gen Virol 68: 979-987] have unique PAGE patterns. "Electropherotyping" of the RNAs isolated from infected cells might be used for identifying and distinguishing hantaviruses.