FIG 2.

Human monoclonal antibodies bind to conformational epitopes on hemagglutinin. Antibodies were used to probe a blot of lysed Madin-Darby canine kidney cells that were infected with A/Vietnam/03/2004 (H5N1). BF1-1, BF1-10, and BF1-19, which showed reactivity by the HI assay, showed no binding, indicating that they did not recognize linear epitopes of hemagglutinin. BF1-32, which did not show reactivity by the HI assay, recognized linear epitopes on what appeared to be HA₁, as the most prominent bands corresponded to HA₀ (82 kDa) and HA₁ (58 kDa), with a less intense band being found at 78 kDa.