Question

What does it mean for a virus to be persistent or latent, and how are these events important?

Answer 1

Viruses are entities which can cause lysogenic or lytic infections in bacteria, plants and in animals. The viruses can invade and burst a cell which is termed as Lytic. On the other hand it can get inside the host and cause lysogeny.

• The latent and persistent infections are part of lysogeny, with few differences. Persistent and latent infections may occur if the viral genome becomes integrated into the host cell genome.

• In persistent viral infections, the virus may reproduce at a slow rate and be shed by the cell for a very long time. Example: hepatitis B infections.

• During persistent infections, the viral genome may be either stably integrated into the cellular DNA or maintained episomally.

• The latent infections are characterized by the viruses entering a dormant state and not replicate until some trigger causes them to activate and become either persistent or lytic. These virus infections are called latent, and this is typical of HIV and herpes virus infections.

• Lysogeny is impotant clinically because it has capacity to alter the host cell and its behaviour. Example: Corynebacterium diptheriae only produces diptheria toxin if is infected with a phage carrying the toxin gene. A similar situation exists with Clostridium botulinum and botulism toxin and Streptococcus pyogenes and erythrogenic toxin - the toxin which provokes scarlet fever.