Mutational analysis. Antibody anti-H1N1 induced plasmablast variable genes were amplified by single-cell RT-PCR using primer sets and PCR efficacy of the mAb, mice were treated intraperitoneally with 200 µg (10 mg/kg of body weight) of the specific mAbs. 12 h later, mice were challenged with 3xLD50 of one of the mouse adapted influenza viruses used in the study. All mice were monitored daily for any signs of morbidity and mortality. Body weight changes were registered daily for a period of 14 d. All mice that lost >25% of their initial body weight were sacrificed according to the institutional animal care and use committee guidelines. To determine the therapeutic efficacy of the mAbs, mice were challenged with 3xLD50 of the mouse-adapted pandemic H1N1 virus. At various times after infection (12, 24, 36, 48, 60 , and 72 h) mice were treated intraperitoneally with 200 µg (10 mg/kg of body weight) of the specific mAbs. All mice were monitored daily and the body weight changes were registered daily as described above.