Morphological characterization of baculovirus Autographa californica multiple nucleopolyhedrovirus

The budded form of baculovirus Autographa californica multiple nucleopolyhedrovirus is used widely in biotechnological applications. In this study, we observed the morphology of baculovirus in nanometer scale by atomic force microscopy. Additionally, the correlation between transduction efficiency and virus stock storage time was evaluated. By atomic force microscopy, asymmetrical baculovirus particles with enlarged head regions were detected. Observed virus stocks contained variable-length particles, 256 ± 40 nm, along with disintegrated particles and/or cellular components. Long-term storage of stocks led to virus aggregation and decreased cellular entry and transgene expression in mammalian cells. Significantly, baculovirus vectors bearing a 33.5-kb insert induced formation of elongated nucleocapsids, indicating that viral dsDNA genome size influences particle size. Taken together, our results provide the first 3D-characterization of baculovirus morphology and insight into its stability after storage.