Qualitative and quantitative ultrastructural analysis of the membrane rearrangements induced by coronavirus

Coronaviruses (CoV) are enveloped positive-strand
RNA viruses that induce different membrane rearrangements
in infected cells in order to efficiently
replicate and assemble. The origin, the protein composition
and the function of these structures are
not well established. To shed further light on
these structures, we have performed a time-course
experiment in which the mouse hepatitis virus
(MHV)-induced membrane rearrangements were
examined qualitatively and quantitatively by
(immuno)-electron microscopy. With our approach
we were able to confirm the appearance of 6,
previously reported, membranous structures
during the course of a complete infection cycle.
These structures include the well-characterized
double-membrane vesicles (DMVs), convoluted
membranes (CMs) and virions but also the
more enigmatic large virion-containing vacuoles
(LVCVs), tubular bodies (TBs) and cubic membrane
structures (CMSs). We have characterized the
LVCVs, TBs and CMSs, and found that the CoVinduced
structures appear in a strict order. By combining
these data with quantitative analyses on viral
RNA, protein synthesis and virion release, this
study generates an integrated molecular and ultrastructural
overview of CoV infection. In particular, it
provides insights in the role of each CoV-induced
structure and reveals that LVCVs are ERGIC/Golgi
compartments that expand to accommodate an
increasing production of viral particles.