Tightly regulated expression of Autographa californica multicapsid nucleopolyhedrovirus immediate early genes emerges from their interactions and possible collective behaviors

Improving the production of baculovirus expression vector by overexpression of IE0/IE1 through tandem promoter

The baculovirus expression vector system, known for its protein production in insect cells and has been criticized for its relatively low expression capacity. IE0/IE1, acknowledged vital early regulators of baculovirus, are indispensable for the virus proliferation and regulate the expression of various genes within the virus. Prior research has reported a substantial rise in exogenous gene expression upon overexpression of IE01. In this study, to mitigate the risk of generating defective viruses due to homologous recombination, we introduced an additional promoter in vivo within the viral genome, thus overexpressing IE0/IE1. The research outcomes demonstrate that the expression of exogenous proteins is notably enhanced without the homologous regions sequence for enhancement. In parallel, they still indicate that the upregulation of IE0/IE1 not only boosts viral titers but also enhances apoptosis within cellular populations. In sum, we successfully constructed a novel baculovirus expression vector that significantly enhances the expression of exogenous genes, presenting a new perspective for optimizing the baculovirus expression vector system.

Inhibitory role of the Bm8 protein in the propagation of Bombyx mori nucleopolyhedrovirus

Lepidopteran nucleopolyhedroviruses have distinct viral tissue tropisms in host larvae. We previously identified the Bm8 gene of Bombyx mori nucleopolyhedrovirus (BmNPV), the product of which inhibits viral propagation in the middle silk gland (MSG). However, it is unknown whether this inhibitory function of the Bm8 protein is specific to MSGs. Here we generated a Bm8-disrupted recombinant BmNPV expressing green fluorescent protein (GFP) and examined viral propagation in B. mori cultured cells and larvae. We found that Bm8-disrupted BmNPV produced fewer budded viruses and more occlusion bodies (OBs) than the wild-type virus in both cultured cells and larvae. Microscopic observation of OB production and GFP expression revealed that Bm8 disruption accelerated the progression of viral infection in various larval tissues. Furthermore, quantitative reverse transcription-polymerase chain reaction experiments showed that the loss of Bm8 enhanced viral gene expression in BmNPV-infected larval tissues. These results indicate that the Bm8 protein suppresses viral propagation to varying degrees in each larval tissue, which may establish BmNPV tissue tropisms in B. mori larvae.