Schematic diagram of the baculovirus group II f gene, showing the proteolytic cleavage site, fusion peptide (FP), heptad repeat (HR) regions, transmembrane region (TM), and cytoplasmic tail domain (CTD) of HearNPV F (A) and C-terminal truncations of F (B). Each donor plasmid carrying HearNPV f or a truncated f gene was used to construct a repair HearNPV bacmid and a pseudotyped AcMNPV bacmid.