2.3 Immunization and
challenge
Female BALB/c mice (6-8 weeks old) were randomized into groups. Six
groups were subcutaneously immunized with 26.6 µg (100 µL) candidate
vaccines, respectively (Fig. 1a). The Cap VLPs group (20 µg, Cap molar
equivalent) is serves as positive control. The Carbopol 971P as adjuvant
at final concentration 1% (Ding et al.,
2017). Booster immunization was performed at the 21 and 42 days post
initial immunization (dpi). Serum samples were collected at 63 dpi and
stored at -20 °C until use. Mice in each group were divided into three
groups (n=9). Mice were lightly anesthetized and intranasally challenged
with lethal dose humans, swine and avian IAV at 64 dpi, respectively.
Survival rates and body weight loss were monitored daily for 14 days
post challenge (dpc). Mice were humanely euthanized if weight loss of ≥
25%.