Figure 5. Heterosubtypic binding and neutralizing activity.

(a) The binding activity of the IgG1 panel (5 µg/ml) was measured against 0.5 µg/ml directly coated recombinant HA antigen (see methods for strain designation), BPL inactivated NIBRG-14 (HA from A/Vietnam/1194/04) or BPL inactivated H1N1 (A/New Caledonia/1/99). Detection was performed with mouse anti-human IgG-HRP and results given as OD₄₉₂ nm. Control antigens were Influenza B virus (B/Ohio/1/05) and Rabies vaccine (RIVM, Bilthoven). Anti-rabies virus (RV) IgG1 (IGHV1-69) was used as a negative control. ELISA values>10× background or between 10× and 3× background are coloured red and yellow respectively. (b) Phylogenetic tree of amino acid sequences at the subtype level, division of subtypes by group is indicated by coloured balloons (blue H1 and H9, green H3 and H7). (c) Neutralizing activity of purified IgG1 against 100 TCID₅₀ of influenza A viruses, IC₅₀ calculated as in Fig. 3.