Kinetic analysis of the influenza A virus HA/NA balance reveals contribution of NA to virus-receptor binding and NA-dependent rolling on receptor-containing surfaces
(A) Schematic representation of the experimental set-ups. Colours of the sensors correspond with the colours of the lines in graphs B-D. (A). Biotinylated 3’N+O fetuin (3’N+O fetuin bt) is indicated by the large Xs. Origin of the HA and NA proteins of the viruses used is indicated, as well as the absence or presence of OC during the incubation of the sensors with the viruses. The left, middle and right panels correspond with the graphs shown in B,C, and D (A). The capital R indicates the regeneration of the sensors. (B) 75 pM WSNHAMtSIN (with low NA activity) was bound in presence of 10 μM OC to two sensors containing biotinylated 3’N+O fetuin (3’N+O fetuin bt) (loaded to maximum level) for 15 minutes reaching ~15% of the maximum binding level. A control sensor was dipped in PBS. (C) The sensors from B were allowed to bind 30 pM PR8MtSIN, in the presence or absence of 10 μM OC. (D) Regenerated sensors were allowed to re-bind WSNHAMtSIN at a concentration of 100 pM to determine the degree of de-sialylation that occurred in (C).