Viral pathogens 2

Question 1

What do viruses need in order to replicate?

Answer 1

In order to replicate, viruses need to find host cells

Question 2

What do viruses replicate in?

Answer 2

• Viruses replicate in specific cells for specific reasons and to allow its transmission and pathogenesis

Question 3

Why are CD4+ key in the immune response to HIV?

Answer 3

• CD4+ are key in the immune response to HIV infection as the course of HIV infection goes on, you get less CD4+ T cells and more viral RNA genomes

Question 4

What happens to levels of CD4+, 10 years after the infection of HIV-1?

Answer 4

• 10 years after the infection, you have almost undetectable levels of CD4+ T cells and large numbers of copies of the RNA genome reaching an end point

Question 5

What do viruses do to evade the immune response?

Answer 5

• To evade this immune response, viruses replicate in the immune cell whose function is to recognise and kill infected cells

Question 6

What does replication of viruses in the immune cell hide the virus from?

Answer 6

• Replication in the immune cells hides the virus from the immune cells and inhibits immune cell function

Question 7

What does inhibition of immune cell function allow other pathogens to do ?

Answer 7

• Inhibition of immune cell function allows other pathogens to replicate in virus infected hosts.
§This allows disease to occur

Question 8

What are the 2 types of CD4 T cells that virus enter?

Answer 8

• Virus enters CD4 T cells(Non-permissive CD4 T cells/permissive CD4 T cells)

Question 9

What are permissive CD4 T cells?

Answer 9

• Permissive CD4 T cells are cells In which the virus can fully replicate

Question 10

What are non-permissive CD4 T cells?

Answer 10

• Non-permissive CD4 T cells are cells in which the virus can’t fully replicate

Question 11

What happens once virus enters permissive CD4 T cells?

Answer 11

• Once virus enters cell and converts its RNA into dsDNA, it infects the nucleus

Question 12

What mechanism does the CD4 T cell have and what does this activate, trigger and cause?

Answer 12

• Host cell has mechanisms in place which recognise this DNA as foreign and activates caspase-3, which triggers apoptosis, causing CD4 T cells to die
§This plays a small role in CD4 T+ cell depletion and this response is mostly not successful

Question 13

What happens when virus enters non-permissive CD4 T cells?

Answer 13

• Virus enters but doesn’t replicate fully and this leads to the accumulation of incomplete reverse transcriptase

Question 14

What does the IFI16 DNA sensor recognise and what does it activate?

Answer 14

• IFI16 DNA sensor recognises the foreign nucleic acids which activates innate antiviral response, inflammatory responses and inflammasome response
§This activates Caspase-1 which leads to pyroptosis and hence cell death occurs as well as the excretion of immune molecules to warn neighbouring cells of the infection

Question 15

What does HIV infection lead to and cause?

Answer 15

• HIV infection leads to pyroptosis and causes:

-CD4 T cell death and release of pro-inflammatory cytokine + cellular contents which causes inflammation

Question 16

What is direct activation of immune system through?

Answer 16

• Direct activation of immune system through cell death

Question 17

What is indirect activation of immune system through?

Answer 17

• Indirect activation of immune system through pro-inflammatory cytokine release

Question 18

What is primary infection?

Answer 18

When you’ve never been exposed to pathogen before and so exposure allows virus to replicate and can typically be resolved by immune suppression

Question 19

Why does an infection become latent?

Answer 19

• Infection then moves to areas in which immune system can’t access and hence becomes latent

Question 20

What does reactivation from latency occur upon?

Answer 20

• Reactivation from latency occurs upon immunodeficiency and the immune system is no longer suppressing the virus

Question 21

HSV

Answer 21

• HSV moves into the nervous system and a lack of immune surveillance here as immune cells don’t access the blood brain barrier
• HSV remains there without replication, ready for immunodeficiency

Question 22

What happens when KSHV enters cell?

Answer 22

• KSHV enters cell and KS progenitor cells are produced.
○ This is a primary infection
○ There’s latent infection of V cells
○ KSHV continues replicating slowly

Question 23

What happens to interactions between T cells and B cells due to HIV?

Answer 23

○ HIV leads to T cells depletion hence interaction no longer occurs
○ Virus in the B cell reactivates

Question 24

What happens if KS enters a non-permissive B cell?

Answer 24

○ KS progenitor cells produced
○ Latent infection of B cells but no transformation
○ Requires an inflammatory signal to reactivate from latency
○ Some of these cells become oncogenic