Autographa californica (Ac), Bombyx mori (Bm), Hyphantria cunea (Hc) and Spodoptera exigua (Se) nucleopolyhedroviruses (NPVs) were each inoculated to SF21cells, BmN-4 cells, SpIm cells and Se301 cells, and cytopathic effect (CPE) manifestation, viral DNA production, badded virion yield into the culture medium, viral structural protein production, polyhedrin (the matrix protein of polyhedra) production, and polyhedron formation in the inoculated cells were comparatively examined. The results showed that AcNPV were able to multiply and yield budded virions in all of four cell lines examined, but production of polyhedrin and polyhedra occurred only SF21cells, SpIm cells and Se301 cells, and not in BmN-4 cells.
BmNPV multiplied to a high titre in BmN-4 cells and to a low titre in SpIm cells in which only a few number of cells manifested CPE.No clear CPE was observed in SF21 and Se301 cells inoculated with BmNPV.HcNPV multiplied unequivocally and produced polyhedra in SpIm and Se301 cells. In SF21 cells, HcNPV yielded budded virions only to a low titre and produced neither polyhedrin nor polyhedra. In HcNPV-inoculated BmN-4 cells, significant amount of viral DNA accumulated, but accumulation of viral structural protein and polyhedrin and budded virion yield were never detected. SeNPV multiplied clearly only in Se301 cells, and appeared to induce apoptotic form of cell death in many cells of SpIm culture.
These results indicate that NPVs exhibit complex feature in the cells depending upon both the species of NPV and cultured cells being inoculated, and establish important basis for the analysis of molecular mechanisms of host range determination in NPVs.