Kinetics of the development of H5 HA-specific serum IgG (A), IgA (B), and neutralizing antibodies (C) elicited by various H5N1 prime-boost regimens.

<p>Ferrets were immunized with either 10⁷ PFU of VN04 <i>ca</i> virus (weeks 0 and 4) or 200 µg of H5 HA DNA (weeks 0, 2 and/or 4) and serum samples were collected regularly at 2-week intervals. H5 HA-specific IgG and IgA in ferret serum samples (N = 4/group) were determined by ELISA using recombinant VN04 H5 HA as antigen. Neutralizing antibody titers against 100 TCID₅₀ of the VN04 <i>ca</i> virus are depicted. Geometric mean titers from each group are shown.