A cell is said to be permissive when it supports the virus multiplication. Viruses infecting the permissive cells are usually cytocidal (kill the host cell) while infection to non- permissive cells do not produce any effect upon infection hence called abortive. When the virus replication gets completed, no more viral mRNA or protein are produced in the infected cells and is referred as restricted . In some cases viral DNA or RNA may sequester indefinitely inside a host cell and this condition is called as persistent infection .

 

9.1 Cytolytic infections

Cytolytic infections can be clearly visualized under a light microscope. The characteristic of CPE effect is an important parameter for a virologist to identify the virus species. In some viral infections inclusion bodies which are formed upon viral infection are identified after specific staining methods and are used as a tool for identifying the virus. Seller's stain is used to visualize the Negri bodies in the cells infected with Rabies virus. Inclusion bodies are the remnants of viral structural and non-structural proteins. Alternatively, inclusion bodies may be formed by a host cell macromolecule upon virus infection. For example, Cytomegalovirus infection to a cell changes the cytoskeleton of infected cell which are then visible as inclusion bodies. Viral infection to a permissive cell is often associated with changes in cellular biosynthetic pathways, its morphology, and cell physiology.

Table 9.1 Viral inclusion bodies in some human diseases