Rescue of a H3N2 Influenza Virus Containing a Deficient Neuraminidase Protein by a Hemagglutinin with a Low Receptor-Binding Affinity

Influenza viruses possess at their surface two glycoproteins, the hemagglutinin and the neuraminidase, of which the antagonistic functions have to be well balanced for the virus to grow efficiently. Ferraris et al. isolated in 2003–2004 viruses lacking both a NA gene and protein (H3NA- viruses) (Ferraris O., 2006, Vaccine, 24(44–46):6656-9). In this study we showed that the hemagglutinins of two of the H3NA- viruses have reduced affinity for SAα2.6Gal receptors, between 49 and 128 times lower than that of the A/Moscow/10/99 (H3N2) virus and no detectable affinity for SAα2.3Gal receptors. We also showed that the low hemagglutinin affinity of the H3NA- viruses compensates for the lack of NA activity and allows the restoration of the growth of an A/Moscow/10/99 virus deficient in neuraminidase. These observations increase our understanding of H3NA- viruses in relation to the balance between the functional activities of the neuraminidase and hemagglutinin

Recombinant viruses produced by reverse genetics and their growth characteristics after two passages in MDCK cells.

a<p>Core defined by the PB1, PB2, PA, NP, NS and M genes.</p>b<p>CPE for cytopathic effect. – no visible CPE. +++ visible CPE.</p>c<p>TCID₅₀/50 µl : dose infecting 50% the cell culture determined in MDCK cells.</p

Experiments done on H3NA- viruses.

<p>Experiments done on H3NA- viruses.</p