It is well documented in the literature that bivalency of a whole IgG molecule may be an essential features for the biological activity of a mAb [21, 22, 23, 24] . For this reason, in this work, to evaluate PN-SIA28 features as whole IgG molecule, IgG PN-SIA28 was generated and tested in different neutralization assays against human, swine and avian influenza A viruses belonging to both HA based phylogenetic groups and encompassing all subtypes responsible of described pandemic events. The results obtained showed that IgG PN-SIA28 strongly neutralizes viruses belonging to the group 1 as well as those of the group 2. More in details, IgG PN-SIA28 neutralized all the H1N1 tested viruses with an half maximal inhibitory concentration (IC 50 ) ranging between 0.4-3.7 mg/ml, the H5N1 viruses with IC 50 ranging between 0.9-2.8 mg/ml, the H2N2 subtype isolate with an IC 50 of 0.8 mg/ml and the H9N2 subtype strain with an IC 50 of 0.9 mg/ml (Table 1, Figure S1 ). More interestingly, IgG PN-SIA28, also potently neutralizes H3N2 viruses circulating in the years from 1968 to 1975 with IC 50 ranging between 0.8-2.6 mg/ml (Table 1, Figure S2 ) despite the great phylogenetic distance of these viruses compared to those belonging to group 1 ( Figure 1 ). No detectable neutralizing activity was observed against more recent H3N2 tested viruses (Table 1, Figure 1 and S3) as well as for the H7N2 tested isolate.