Abstract
Bombyx mori nuclear polyhedrosis virus (BmNPV) is an important pathogen of silkworms. Despite extensive studies in recent decades, the interaction between BmNPV and host cells is still not clearly understood. Autophagy is an intrinsic innate immune mechanism and it controls infection autonomously in virus-infected cells. In this study, we found that BmNPV infection could trigger autophagy, as demonstrated by the formation of autophagosomes, fluorescent Autophagy-related gene 8-Green Fluorescent Protein (ATG8-GFP) punctate, and lipidated ATG8. Meanwhile, autophagic flux increased significantly when monitored by the ATG8-GFP-Red Fluorescent Protein (RFP) autophagy tandem sensor and protein degradation of p62. In addition, almost all of the identified autophagy-related genes (Atgs) had been up-regulated post infection in mRNA levels. Then, we screened Atgs with the greatest fold-change during virus infection. Interestingly, all of the screened Atgs positively regulated the expression of virus genes. Further studies showed that Atg7 and Atg9 could contribute to the level of autophagy caused by viral infection. Our results demonstrated that BmNPV induced host cell autophagy to benefit its infection. These results offer insight into the complex interactions between virus and host cell, and viral pathogenesis.
Highlights
Baculoviruses are a family of DNA viruses that have a large, circular, supercoiled, and double-stranded DNA-containing genome that infect insects, of the orderLepidoptera [1,2]
We found that autophagy-related genes could directly affect viral infection
Many double-membrane vesicles appeared in Bombyx mori nucleopolyhedrovirus (BmNPV)-infected cells, suggesting that BmNPV infection could trigger the production of autophagosomes in BmN-SWU1 cells (Figure 1A)
Summary
Baculoviruses are a family of DNA viruses that have a large, circular, supercoiled, and double-stranded DNA-containing genome that infect insects, of the orderLepidoptera [1,2]. Baculoviruses are a family of DNA viruses that have a large, circular, supercoiled, and double-stranded DNA-containing genome that infect insects, of the order. Bombyx mori nucleopolyhedrovirus (BmNPV), one of the best characterized baculoviruses, has two virion phenotypes during its infectious life cycle: occlusion-derived virus (ODV). ODV is responsible for lateral transmission between individuals, while BV is responsible for the spread of the infection throughout the host [3,4,5]. Autophagy mediates a highly conserved and regulated self-degradation process that is initiated as an adaptive response in unfavorable conditions, such as nutrient deprivation and innate immunity [6,7]. Autophagy is a highly conserved cell degradation pathway, but the amount of degradation varies by cell type, nutrients, environment, or cellular stresses, including virus infection [8]. The autophagy process contains three different steps: autophagy induction; cargo recognition and packaging; Viruses 2018, 10, 14; doi:10.3390/v10010014 www.mdpi.com/journal/viruses
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