In this study, in order to better characterize its neutralizing activity, PN-SIA49 was produced as whole IgG1 molecule using the BD BaculoGold System. The whole IgG molecule was tested in fluorescence inhibition assay, infectious foci formation reduction assay and plaque reduction assay against human, swine and avian influenza A viruses belonging to phylogenetic group 1 (H1N1, H2N2, H5N1 and H9N2) and group 2 (H3N2 and H7N2). The results obtained showed that IgG PN-SIA49 has a stronger neutralizing activity compared to Fab PN-SIA49 (Table 1) [26, 27] . Indeed, IgG PN-SIA49 neutralized all tested viruses belonging to group 1, except the virus strain belonging to H9N2 subtype, with a half maximal inhibitory concentration (IC50) ranging between 0.1-1.9 mg/ml (Table 1 and Figure S1 ). On the contrary, PN-SIA49 showed no neutralizing activity against the viruses belonging to group 2 ( Figure S2 ). These data suggest that the epitope recognized by PN-SIA49 is conserved among group 1 viruses.