Question

What parts of a human cell does a virus use to replicate?

Define acute, latent, chronic, and viral oncogenesis. Provide an example of each.

Answer 1

Viruses can replicate only by invading a host cell and using the enzymes and organelles of the host cell to make more viruses. Since viruses depend on host cells for replication, they are called obligate intracellular parasites.

RNA viruses replicate.

Upon entering the host cell, viral RNA is released into the host cell's cytoplasm. There, it uses the host cell's ribosomes to produce new viral proteins.

acute viral infections

a short incubation and a short duration. virus is good at taking advantage before the immune system has time to react, but the immune system is very good at getting rid of them (that is why the duration is short)

a chronic, persistent viral infection

long incubation period and long duration-takes the immune system a long time to get rid of them and sometimes they can not get rid of them at all

a latent, persistent viral infection

when the virus become dormant in the body, so there are no symptoms. The latent phase could last years, decades, etc., there is no virus production BUT it can become active again.

latent viral infection become active again ,example

1. provital infection latency

2. episomal latency

EX: shingles, herpes (cold sore), both can go dormant but can become active again

Viral oncogenesis

This is a virus that causes cancer

Viruses are suspected of causing cancer

- 7 virus families contain viruses recognised as oncogenic: 5 are DNA viruses, 2 are RNA viruses

- RNA viruses have productive infection

> expression of all the viral proteins & progeny virions bud from the cell membrane

ex of oncogenic RNA virus: Retroviruses

- DNA viruses have non-productive infection

> viral DNA integrated into cellular genome -> no progeny virus is produced

ex of oncogenic DNA virus: Herpesviruses & Papillomaviruses

- Cancer result if immunological surveillance fails to detect & clear transformed cells