Occlusion-derived baculovirus: interaction with human cells and evaluation of the envelope protein P74 as a surface display platform

To develop complementary baculovirus-based tools for gene delivery and display technologies, the interaction of occlusion-derived baculovirus (ODV) with human cells, and the functionality of the P74 ODV envelope protein for display of the IgG-binding Z domains (ZZP74) were evaluated. The cellular binding of ODV was concentration-dependent and saturable. Only minority of the bound virions were internalized at both 37 and 4 degrees C, suggesting usage of direct membrane fusion as the entry mode. The intracellular transport of ODV was confined in vesicular structures peripheral to the plasma membrane, impeding subsequent nuclear entry and transgene expression. Transduction of ODV was not rescued by mimicking the preferred alkaline environment and lowered temperature of the ODV infective entry, or following treatment with the microtubule depolymerizing agent nocodazole or with the histone deacetylase inhibitor sodium butyrate. Similar to unmodified P74, the ZZP74 chimera localized in the intranuclear ring zone, and was enriched in virus-induced microvesicles. However, Western blotting of ODV and budded virions (BV), as well as viral envelope and nucleocapsid fractions combined with functional infection/transduction studies revealed incorporation of the ZZP74 fusion protein into viral nucleocapsids. The ZZP74 BV preserved normal infectivity, polypeptide profile, and morphology, but became incapable of entering and transducing human cells.