Fig. 4.

Antibody mediates protection afforded by immunization with LAH-KLH. (A) Analysis of prechallenge serum from mice infected with PR8 reveals a positive correlation between hemagglutinin-specific antibody titer and increase in body weight on days 1–3 after infection. (B and C) Pooled sera from mice immunized with LAH-KLH, mice infected with H1 or H3 virus, or mice immunized with KLH alone were transferred to mice 2 h before infection with A/Georgia/81, a seasonal human H3 virus, or with the H1 virus PR8. Lung titers were evaluated on day 2 postinfection (***P < 0.001). (D and E) Human sera taken pre- or postimmunization with the TIV were evaluated for binding activity with the LAH polypeptide. Data shown are from serum samples diluted 1:3,000. (D) Subjects responded variably to seasonal vaccination, and (E) serum demonstrates minimal binding activity against the LAH peptide.