Fig 3.

Immunologic activity of human NP-specific MoAb in vitro. (A) The virus-neutralizing activity of MoAb NP against influenza virus A/PR/8/34 (H1N1, black bars) or RESVIR-9 (H3N2, gray bars) was tested using an infectivity reduction assay as described previously (22) at various concentrations as indicated. No virus-neutralizing activity was observed, in contrast to the use of homologous positive-control postinfection ferret sera (FS). (B) MoAb NP did not mediate complement-dependent cytotoxicity of A549 cells (gray bars), in contrast to an IgG antibody preparation obtained from human serum with HI activity against the virus used (RESVIR-9 [H3N2]) (white bars). Since equivalent volumes were used for the human (Hu) IgG and the MoAb NP, the concentration of MoAb NP (μg/ml) is indicated or the multiplicity of the volume of human IgG that was able to prevent hemagglutination of 4 hemagglutinin units as measured in the HI assay (HI units [U]/ml) is indicated on the x axis. (C and D) Activation of virus-specific CD8⁺ T cells (CD8⁺ T cell clone specific for the HLA-B*3501-restricted epitope NP_418–426 [LPFEKSTVM]) by DC incubated with various concentrations of split virion antigen preparation as measured by intracellular IFN-γ in the absence (gray bars) or presence (white bars) of MoAb NP with DC obtained from two different blood donors. Indicated are mean values ± standard deviations. The presence of MoAb NP did not have an effect on the activation of the NP_418–426-specific CD8⁺ T cells.