L4 - Viral Pathogens 2

Question 1

Describe the typical course of HIV infection?

Answer 1

At the start, during primary infection, the number of CD4+ T cells goes down, while the number of HIV goes up.

As the number of HIV goes up, more T -cell are being killed.

HIV level reaches viral load set point, which is the minimum number of HIV particles you can have without the immune system detecting it, but the virus still replication.

The number of T cells gradually falls, and so there is small number of virus replication, which causes a lot of HIV to be produced, cuasing opportunistic infections.

This ultimately leads to death

Question 2

Why is immunodeficiency advantageous to the virus?

Answer 2

viruses must evade immune responses, some immune responses are mediated by specific cells of the immune system. These immune cells recognise and kill cells infected with the virus.

To evade this, some viruses replicate in the immune cells and inhibit their function. This allows other pathogens to replicate in virus infected cells and thus disease occurs

Question 3

How might HIV kill permissive and non permissive CD4 T cells?

Answer 3

permissive:

infection of CD4 T cell - caspase 3 activation - apoptosis cell death

non- permissive:
innate system activated after infection - caspase 1 activation - pyroptosis cell death

Question 4

How are T cells directly killed during HIV infection?

Answer 4

• HIV infection
• CD4 T cell death by pyroptosis, release of pro-inflammatory cytokines.
• inflammation is caused, recruiting healthy T cells to the area.
• leads to healthy cells being infected and killed in a cycle

Question 5

How are T cells indirectly killed during HIV infection?

Answer 5

• HIV infection
• CD4 T cell death by pyroptosis and inflammation occurs
• inflammation causes migration of neutrophils into tissue and causes more T cell death

Question 6

What are the 2 possible routes of infection in an HIV infected individual?

Answer 6

• primary infection:
  HIV individual who dosen’t have another virus, encounters the virus for the 1st time and they get infected.

Reactivation from latency:

individual might’ve had another virus before HIV, and after they get infected with HIV, it may be reactivated due to low number of T cells