Question

Feedback See Hint Which of the following is NOT a method by which latent viral infections, such as a latent herpes infection, persist inside their hosts? * Choose one: O A. infecting long-lived cells, such as neurons B. producing heterochromatin to inactivate viral proteins C. mimicking immunosuppressive signals O D. using epithelial cells for viral replication

Answer 1

The Herpes viruses undergo a productive infection upon infecting the host organism and then spread to establish a latent infection where they persist in the host. Later, under conditions of stress or other environmental stimuli, they reactivate to undergo a productive infection and spread to new host organisms.

Herpes simplex virus (HSV), in particular, undergoes a productive infection in the mucosal epithelium and spreads to sensory neurons where it undergoes a latent infection. Reactivation leads to virus shedding but can also lead to recurrent disease.

In epithelial cells, the HSV genome is initially silenced by host epigenetic mechanisms, but the virion protein reverse the heterochromatin modifications and promote euchromatin modifications on viral chromatin to promote lytic gene transcription, allowing lytic infection to proceed. In sensory neurons, this however, does not happen because the protein cannot localize to the nucleus activate gene expression. Instead the virus becomes latent.

They undergo latency and enhance neuronal survival by -

• Down-regulation of  lytic gene expression by certain sequences (LAT - Latency Associated Transcript) sequences which act as a long noncoding RNA and promote epigenetic silencing of lytic genes.
• Serving as a precursor for viral miRNAs that inhibit lytic gene expression.
• Inhibits apoptosis.
• Promotes of survival of infected neurons by certain non-apoptotic mechanisms.

Thus option C is incorrect.

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