Escape of non-enveloped virus from intact cells

Abstract

How do viruses spread from cell to cell? Enveloped viruses acquire their surrounding membranes by budding. If a newly enveloped virus has budded through the plasma membrane, it finds itself outside the cell immediately. If it has budded through the bounding membrane of an internal compartment such as the ER, the virus finds itself in the lumen, from which it can exit the cell via the conventional secretion pathway. Thus, although some enveloped viruses destroy the cells they infect, there is no topological need to do so. On the other hand, naked viruses such as poliovirus lack an external membrane. They are protein-nucleic acid complexes within the cytoplasm or nucleus of the infected cell, like a ribosome, a spliceosome or an aggregate of Huntingtin protein. The simplest way for such a particle to pass through the single lipid bilayer that separates it from the outside of the cell would be to violate the integrity of that bilayer. Thus, it is not surprising that the primary mode of exit for non-enveloped viruses is cell lysis. However, more complex exit strategies are possible, such as the creation of new compartments whose complex topologies allow the exit of cytoplasm and its contents without violating the integrity of the cell. Here we will discuss the non-lytic spread of poliovirus and recent observations of such compartments during viral infection with several different picornaviruses.

Non-Lytic Egression of Infectious Bursal Disease Virus (IBDV) Particles from Infected Cells

“…In a recent review article [32], Bird and Kirkegaard proposed three alternative mechanisms capable of sustaining non-lytic egression of naked viruses. Our TEM data clearly argues against first proposed mechanism, the blebbing of virus particles from the PM of infected cells, for the release of IBDV virions.…”

Rice Reoviruses in Insect Vectors

“…Recently, we showed that these compartments contain autophagy protein LC3, indicating a potential role for a cellular autophagy pathway in nonlytic viral release. The subversion of the autophagy pathway by animal nonenveloped viruses has been extensively studied (9,10). Given that the autophagy pathway is a cell clearance mechanism, it comes as a surprise that rice reoviruses have evolved to subvert such cellular process for viral nonlytic release.…”

Viruses exploit the tissue physiology of the host to spread in vivo

“…The general belief that non-enveloped viruses are exclusively released as a consequence of cell lysis (Fig. 1D) has recently been challenged [62]. HepA, HepE, and poliovirus were shown to escape from intact cells by acquiring a temporary membrane (Fig.…”