Hemagglutinin displayed baculovirus protects against highly pathogenic influenza.

Baculovirus (BV) replicating in insect cells can express a foreign gene product as part of its genome. The influenza hemagglutinin (HA) can be expressed from BV and displayed on the surface of baculovirus (HA-DBV). In this study we first generated six recombinant baculoviruses that expressed chimeric HAs with segments of the BV glycoprotein (gp64). The signal peptide (SP) and cytoplasmic tail (CT) domains of gp64 can enhance the display of HA from A/PR8/34 on BV surface, while the transmembrane (TM) domain of gp64 impairs HA display. Different doses of either live or β-propiolactone (BPL)-inactivated HA-DBV were administered to BALB/c mice. Live HA-DBV elicited higher hemagglutination-inhibition (HAI) titers than BPL-inactivated HA-DBV, and provided sterilizing protection. A second generation recombinant BV simultaneously displaying four HAs derived from four subclades of H5N1 influenza viruses was constructed. This tetravalent H5N1 HA-DBV vaccine elicited HAI titers against all four homologous H5N1 viruses, significantly decreasing viral lung titers of challenged mice and providing 100% protection against lethal doses of homologous H5N1 viruses. Moreover, mice vaccinated with HA-DBV had high levels of IFNγ-secreting and HA-specific CD8+ T cells. Taken together, this study demonstrates that HA-DBV can stimulate strong humoral, as well as cellular immune responses, and is an effective vaccine candidate for influenza.