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Researchers have developed a model experimental system that mimics how viruses exit cells. The new technology will not only be useful for investigating this important process but could also serve as a useful tool in synthetic biology and other domains of biotechnology. The findings were published in the journal Science and Technology of Advanced Materials.
After using a host cell's machinery to replicate, viruses exit through a process called budding. In this process, new virus particles push against the cell membrane, which then wraps around them and pinches off, creating a protective envelope encapsulating protein capsule called a capsid. This allows the viruses to leave the cell and spread to infect other cells.
In the study, researchers at the Graduate School of Engineering, Tottori University in Japan created a model of this process using giant unilamellar vesicles (GUVs), which are bubble-like structures made of lipids (fats) that closely resemble cell membranes. The team modified a peptide molecule found in certain viral proteins involved in the infection of host cells. They added a long carbon chain known as an octyl chain to the molecule, creating an anchor that enhances its ability to attach to lipid membranes. When these modified peptides were added to the outside of the GUVs, they induced the formation of smaller daughter vesicles that bud off, mimicking viral capsids – and the daughter vesicles could also encapsulate materials, just like a virus.
Budding inside to outside: an experimental system shows how viruses leave an infected cell by generating buds. This allows the viruses to leave the cell and spread to infect other cells.
“This budding can occur in two ways, from the outside to the inside of the GUV, or from the inside to the outside, depending on where we place the peptides,” explains Kazunori Matsuura, who led the study. “This flexibility in how the vesicles bud shows great potential for controlling how these artificial viral capsid systems interact with specific cells.”
The presence of the octyl chain is crucial. Without it, the peptides don’t induce significant budding, highlighting the importance of these structural features. The researchers also discovered that GUVs composed of more flexible lipids had a higher budding success rate than those made of less flexible lipids.
“The way this budding occurs is similar to how nanoparticles can influence GUVs by increasing surface tension when they adhere to the membrane,” says Hiroshi Inaba, co-author of the study. “When the capsids attach to the GUVs, they create a crowded environment that triggers budding as the surface tension rises.”
The new artificial viral capsid system not only enhances our understanding of viral behaviour but also paves the way for innovative drug delivery strategies, as well as treatments based on improving intercellular communication and aiding in recovering cellular components. The new model system holds exciting promise for synthetic biology, and the team is now working to make it responsive to external stimuli such as light, which would make the system even more useful in different biotechnological contexts.
Further information
Prof Kazunori Matsuura
[email protected]
Tottori University
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