Deltabaculoviruses encode a functional type I budded virus envelope fusion protein

Authors: WANG, MANLI - Wageningen University; SHEN, SHU - Wuhan University; WANG, HUALIN - Wuhan University; Becnel, James; VLAK, JUST - Wageningen University

Submitted to: Journal of General Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2017
Publication Date: 4/28/2017
Citation: Wang, M., Shen, S., Wang, H., Becnel, J.J., Vlak, J.M. 2017. Deltabaculoviruses encode a functional type I budded virus envelope fusion protein. Journal of General Virology. 98(4):847-852. doi:10.1099/jgv.0.000745.
DOI: https://doi.org/10.1099/jgv.0.000745

Interpretive Summary: Mosquitoes are important vectors of pathogens that cause diseases in man and animals and new control strategies are being investigated by ARS scientists. One group of new microbial control agents under investigation are mosquito pathogenic viruses. Understanding the interactions between these viruses and the mosquito host are crucial to further development. In this collaborative research project between ARS and the Laboratory of Virology, Wageningen University, Wageningen, the Netherlands, investigations were conducted to investigate the functionality of an envelope fusion protein (Cuni-F) from a mosquito baculovirus (CuniNPV), which is a potent pathogen of Culex mosquitoes. It was discovered that Cuni-F is expressed on the surface of cells and can induce cell-cell fusion. This evidence suggests that Cuni-F is a functional fusion protein. Understanding specific proteins involved in cell fusion in mosquitoes provides important clues to pathogenic virus infectivity and host range and can lead to the development of novel control strategies for vector mosquitoes.

Technical Abstract: Envelope fusion proteins (F proteins) are major constituents of budded viruses (BVs) of alpha- and betabaculoviruses (Baculoviridae) and are essential for the systemic infection of insect larvae and insect cells in culture. An F protein homolog gene was absent in gammabaculoviruses. Here we show that open reading frame 104 of Culex nigripalpus nucleopolyhedrovirus (CuniNPV), the only deltabaculovirus member, encodes a putative F-homolog (Cuni-F). When expressed alone, this protein is located on the surface of cells and able to induce cell-cell fusion. When expressed by an alphabaculovirus (Autographa californica nucleopolyhedrovirus (AcMNPV), it was found to be incorporated into BVs. Western blot analyses detected the uncleaved Cuni-F0 form and the furin-cleaved F1 forms. Treatment of infected cells by tunicamycin showed that Cuni-F contains N-glycans. Mutagenesis analysis identified the canonical furin cleavage site 126RARR129 as being responsible for the cleavage of Cuni-F in insect cells. The collective evidence suggests that CuniNPV encodes a functional F protein.