Neuraminidase (NA)‐based immunity to influenza can be useful for protecting against novel antigenic variants. To develop safe and effective tools to assess NA‐based immunity, we generated a baculovirus‐based pseudotyped virus, N1‐Bac, that expresses the full‐length NA of the influenza A/California/07/2009 (H1N1)pdm09 strain. We evaluated the level of NA‐inhibiting (NI) antibodies in the paired blood sera of influenza patients using an enzyme‐linked lectin assay (ELLA) using the influenza virus or N1‐Bac. Additionally, we evaluated the level of NA antibodies using the enzyme‐linked immunosorbent assay (ELISA) with an N1‐expressing Sf21 culture. We detected a strong correlation between our results from using the influenza virus and NA‐Bac pseudoviruses to detect NI antibodies and a medium‐strong correlation between NI antibodies and NA antibodies determined by an N1‐cell ELISA, indicating that baculovirus‐based platforms can be successfully used to evaluate NI or NA antibodies. Furthermore, animal experiments showed that immunization with N1‐Bac protected against infection with a drift variant of the A/H1N1pdm09 influenza virus. Our results demonstrate that recombinant baculovirus can be an effective influenza pseudotype to evaluate influenza serologic immunity and protect against influenza virus infection.
