High-Affinity H7 Head and Stalk Domain–Specific Antibody Responses to an Inactivated Influenza H7N7 Vaccine After Priming With Live Attenuated Influenza Vaccine

Recent studies have shown that live attenuated influenza vaccines (LAIVs) expressing avian influenza virus hemagglutinins (HAs) prime for strong protective antibody responses to an inactivated influenza vaccine (IIV) containing the HA. To better understand this priming effect, we compared H7 HA head and stalk domain-specific B-cell responses in H7N7 LAIV-primed subjects and non-H7-primed controls after a single dose of H7N7 IIV. As previously reported, H7N7 LAIV-primed subjects but not control subjects generated strong hemagglutination-inhibiting and neutralizing antibody responses to the H7N7 IIV. Here, we found that the quantity, epitope diversity, and affinity of H7 head-specific antibodies increased rapidly in only H7N7 LAIV-primed subjects after receipt of the IIV. However, all cohorts generated a vigorous, high-affinity, stalk-specific antibody response. Consistent increases in circulating memory B-cell frequencies after receipt of the IIV reflected the specificity of high-affinity antibody production. Our findings emphasize the value of LAIVs as a vehicle for prepandemic vaccination.