Laboratory of Applied Molecular Entomology, Division of Applied Bioscience, Research Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan.
Laboratory of Applied Molecular Entomology, Division of Applied Bioscience, Research Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan.
Virus Res. 2021 Jan 2;291:198195. doi: 10.1016/j.virusres.2020.198195. Epub 2020 Oct 17.
The Bombyx mori nucleopolyhedrovirus (BmNPV)-based baculoviral expression vector system is among the most efficient expression vector systems for eukaryotic proteins especially when used in combination with silkworms as a host. We newly isolated a novel BmNPV strain (BmNPV H4) in Hokkaido, Japan that outperforms the type strain T3 in terms of both proliferation and expression of polyhedrin protein in silkworm larvae; however, it proliferates poorly in the BmN cell line. We inferred the gene responsible for the differences in proliferation between viral strains by quantifying amino acid similarity distances in protein functional domains and identifying highly divergent alleles between the H4 and T3 strains. Among proteins that differ markedly in functional domain sequence between H4 and T3, we identified the F gene, which encodes the F protein, as a putative cause of proliferative differences between the two strains. Using recombinant viruses with the F protein-coding sequence exchanged between H4 and T3, we determined that the T3 F protein increases H4 proliferation in BmN while the H4 F protein does not improve T3 proliferation in silkworm larvae. Our results suggest that the BmNPV F protein can strongly affect viral proliferation in a genetic background-specific manner and may be an important target for manipulating the proliferation characteristics of BmNPV-based expression vectors.
家蚕核型多角体病毒（BmNPV）杆状病毒表达载体系统是最有效的真核蛋白表达载体系统之一，特别是与家蚕作为宿主结合使用时。我们在日本北海道新分离到一种新型 BmNPV 株（BmNPV H4），该病毒在家蚕幼虫中的增殖和多角体蛋白表达方面均优于 T3 株；然而，它在 BmN 细胞系中的增殖能力较差。我们通过量化蛋白功能域中的氨基酸相似性距离并鉴定 H4 和 T3 株之间高度分化的等位基因，推断出导致病毒株间增殖差异的基因。在家蚕核型多角体病毒 H4 和 T3 株之间功能域序列差异显著的蛋白中，我们鉴定出 F 基因，该基因编码 F 蛋白，是两株间增殖差异的潜在原因。使用在 H4 和 T3 之间交换 F 蛋白编码序列的重组病毒，我们确定 T3 F 蛋白可增加 H4 在 BmN 中的增殖，而 H4 F 蛋白不能改善 T3 在蚕幼虫中的增殖。我们的研究结果表明，BmNPV F 蛋白可以以特定遗传背景的方式强烈影响病毒的增殖，并可能是操纵 BmNPV 表达载体增殖特性的重要目标。
