Peptide mapping characterization of viral proteins generated in a cell-free coupled system for the transcription and translation of influenza virus mRNA

Combined action of mouse alpha and beta interferons in influenza virus-infected macrophages carrying the resistance gene Mx

In mice, the combined action of alpha and beta interferons (IFNs) against influenza viruses is modulated by the host gene Mx. High concentrations of IFN fail to prevent efficiently the replication of influenza A virus in cultured macrophages lacking the gene Mx, whereas cultured macrophages carrying Mx develop strong antiviral activity even at low concentrations of IFN. Several steps in the replication cycle of influenza virus were compared in Mx/Mx and +/+ mouse macrophages treated with IFN-alpha + beta. Uncoating was not affected. A twofold reduction in the accumulation of primary transcripts was observed in IFN-treated macrophages at the highest concentration of IFN regardless of the genetic constitution of the host cell. No evidence was obtained for inhibition of influenza virus translation in macrophages which lacked Mx when treated with IFN-alpha + beta. In contrast, a marked shut-off of influenza virus polypeptide synthesis occurred in Mx-bearing macrophages treated with these IFNs, although the primary transcripts were active in directing the synthesis of viral polypeptides in a cell-free system. We concluded that a specific inhibitory mechanism for influenza virus translation was induced by IFN-alpha + beta in macrophages bearing the resistance gene Mx.

Intracellular glycosylation of influenza hemagglutinin: the effect of glucosamine

The intracellular glycosylation of influenza virus hemagglutinin has been studied in calf kidney primary cultures infected with influenza virus A/NWS (H0N1). Intermediate glycosylated forms were obtained by the addition of glucosamine to the culture medium; they were characterized after [35S]-methionine labelling by their precursor relationship, by immunoprecipitation and peptide mapping. The underglycosylated hemagglutinins were distributed in classes of discrete molecular weight indicating that glycosylation occurred in a stepwise manner. A total of 8 different bands, suggesting 7 glycosylation sites, was obtained under conditions of both complete and incomplete glycosylation.

A new method for the size estimation of the RNA genome segments of influenza virus

Previous estimates of the size of the RNA genome segments of influenza virus have been unreliable because of a lack of suitable RNA species as size markers. We have attempted to overcome this problem by utilising the ability of AMV reverse transcriptase to synthesise full length DNA copies of RNA molecules in the presence of a suitable primer. By comparing such DNA copies of the RNA segments of the influenza virus genome with sequenced restriction fragments from the E. coli plasmid pBR322, we have made more reliable estimates of the sizes of the eight genome segments from influenza virus A/NT/60/68.