Vaccinia virus particles (red and green)

Vaccinia virus particles (pictured) can be immobilized — at least temporarily — by host cells. Credit: Dr Klaus Boller/SPL

Cell biology

How cells imprison viruses in molecular cages

Corralled viruses escape by co-opting cellular proteins.

A protein cage that cells deploy to slow the spread of certain viruses could help scientists to develop better antiviral drugs.

The vaccinia virus is a less-harmful relative of the smallpox virus. After vaccinia reproduces inside a host cell, some viral particles prompt components of the cell’s internal skeleton to form ‘tails’ that protrude from the cell. Each tail has a viral particle at its tip. The tails propel the particles outwards, allowing the virus to cross into adjacent cells.

Michael Way at the Francis Crick Institute in London and his colleagues imaged living human cells to investigate this process in more detail. The researchers found that cellular proteins called septins form ‘cages’ that trap the viral particles, delaying assembly of the tails. Vaccinia eventually breaks free by recruiting other cellular proteins that displace the septin cage, but the virus can be kept locked up by inhibiting these proteins.