Egress mechanisms have been studied for only two archeoviruses:
the rod-shaped rudivirus SIRV2 and the icosahedral STIV. These Sulfolobus viruses differ significantly in
their morphological and genomic properties; however, they exploit the same mechanism for the release of
mature virions from the host cell. Near the end of the eclipse
phase, pyramidal ultrastructures that point outwards and
perforate the S-layer, termed virus-associated
pyramids (VAPs), appear on the surface of infected cells.
Later, the VAPs open, and virions that have been preassembled
in the cytoplasm are released through the apertures. The lysed cells persist in the form of empty
spheres, with apertures delimited by the remnants of the
VAPs. In parallel to the formation of the VAPs, a
massive degradation of the host chromosome is observed in
SIRV2-infected cells.