INCORPORATION OF RECOMBINANT-EXPRESSED HIGHLY CLEAVABLE H7 HEMAGGLUTININ INTO VIRIONS OF SUPERINFECTED INFLUENZA-VIRUSES

CV-1 cells were preinfected with H7-SV40 recombinant vector and superi nfected with influenza viruses A/USSR/90/77 (H1N1), A/Duck/Czechoslova kia/56 (H4N6), or B/Hongkong/73. A fraction of the yields of influenza A viruses was infectious without trypsin treatment due to the incorpo ration of cleaved H7 hemagglutinin into virions. The specificity of th e effect was confirmed by neutralization of the infectivity with anti- H7 serum. At a low multiplicity of infection the incorporation of H7 h emagglutinin into virions allowed the virus to replicate without tryps in in a multi-cycle manner. The fraction of the infectious virus and t he kinetics of the multi-cycle infection in H7-expressing cells were s imilar in the cells superinfected with A/USSR/90/77 and with A/Duck/Cz echoslovakia/56 viruses, thus demonstrating a low specificity of inter action between H7 hemagglutinin and heterologous M2 proteins. The supe rinfection of H7-expressing cells with influenza B/Hongkong/73 virus d id not produce infectious phenotypically mixed virus, which may be reg arded as an indication of inability of influenza B virus NE protein to replace functionally the influenza A virus M2 protein in its interact ion with hemagglutinin.