Preparation of quadri-subtype influenza virus-like particles using bovine immunodeficiency virus gag protein

- BIV gag protein was configured as influenza VLP core component.
- Recombinant influenza VLPs were prepared in Sf9 cells using baculovirus expression system.
- Single- and quadri-subtype VLPs were prepared by using BIV gag as a VLP core.
- Co-localization of H5, H7, H9, and H10 HA was confirmed within quadri-subtype VLP.
- Content of HA subtypes within quadri-subtype VLP was determined.
- Potential advantages of quadri-subtype VLPs as influenza vaccine are discussed.

Influenza VLPs comprised of hemagglutinin (HA), neuraminidase (NA), and matrix (M1) proteins have been previously used for immunological and virological studies. Here we demonstrated that influenza VLPs can be made in Sf9 cells by using the bovine immunodeficiency virus gag (Bgag) protein in place of M1. We showed that Bgag can be used to prepare VLPs for several influenza subtypes including H1N1 and H10N8. Furthermore, by using Bgag, we prepared quadri-subtype VLPs, which co-expressed within the VLP the four HA subtypes derived from avian-origin H5N1, H7N9, H9N2 and H10N8 viruses. VLPs showed hemagglutination and neuraminidase activities and reacted with specific antisera. The content and co-localization of each HA subtype within the quadri-subtype VLP were evaluated. Electron microscopy showed that Bgag-based VLPs resembled influenza virions with the diameter of 150-200 nm. This is the first report of quadri-subtype design for influenza VLP and the use of Bgag for influenza VLP preparation.