The effects of virus infection on  the host cell

1-Cytocidal (death of infected cell)

  • A cell can be directly killed by the virus,
  • The virus kills the cell by
  • Inhibition of synthesis of cellular  DNA, RNA, and protein
  • Lysing the cell during exit
  • Viruses may replicate widely throughout the body without any disease symptoms if they do not cause significant cell damage or death

-e.g., adenovirus and poliovirus


2-Cell fusion

  • Infection of cells with certain viruses causes the cells to fuse producing giant multinucleated cells (syncytia formation) -e.g. herpesviruses & paramyxoviruses

Title: Multinucleate giant cell of Tilapia lake virus infection in fish


3- Formation of intracytoplasmic or intranuclear inclusion bodies

  • These are nuclear or cytoplasmic aggregates of partially folded expressed viral proteins at sites of replication


4-Transformation of cells

  • Some viruses can transform normal cells into malignant cells
  • The transformation is an irreversible genetic process caused by the integration of viral DNA into the host’s DNA


5-Non-Cytocidal changes in virus-infected cells

  • Some viruses do not kill the cells in which they replicate
  • They often cause persistent infection during which infected cells produce and release virions
  • In such infections, overall cellular metabolism is little affected and no overt symptoms are seen
  • In many instances, infected cells even continue to grow and divide
  • This kind of interaction occurs in cells infected with RNA viruses, such as  pestiviruses, arenaviruses, and retroviruses


Not all viruses are bad for you”

  • It’s true, most viruses have a pathogenic relationship with their hosts
  • qBut they are not all bad
  • Bacteriophages (or “phages”) found in  the mucus membrane lining in the different tracts infect and destroy specific bacteria
  • Viral infections at a young age are important to ensure the proper development of our immune systems
  • In addition, the immune system is continuously stimulated by systemic viruses at low levels sufficient to develop resistance to other infections