Immunology 4 - HIV infection

Question 1

Using which enzyme does HIV replicate inside cells?

Answer 1

Reverse Transcriptase

Question 2

How many genes are inside the HIV genome?

Answer 2

9

Question 3

What is the role of reverse transcriptase in HIV?

Answer 3

Converts RNA into DNA which can be incorporated into host cells’ genes

Question 4

What are the two key glycoproteins encoded by the HIV virus?

Answer 4

gp120

gp41

Question 5

Which cell of the immune system is particularly affected by HIV?

Answer 5

CD4+ T cells

Question 6

Recall the receptor and co-receptors for HIV on CD4+ T cells

Answer 6

CD4 receptors

CCR5 CXCR4 coreceptors

Question 7

In people who have natural immunity to HIV, what antibodies may be present in serum?

Answer 7

Anti-gp120 and anti-gp41 (Nt) antibodies

Question 8

How does HIV infection affect CD8+ T cells?

Answer 8

Interferes with activation, as CD4+ T cell and antigen-presenting cell help are not present due to the virus

Question 9

How does HIV infection affect monocytes and dendritic cells?

Answer 9

Not activated by CD4+ T cells and so cannot prime naive CD8+ T cells

Question 10

How does HIV affect immunological memory?

Answer 10

CD4+ T cell memory is lost

CD8 memory cell not activated by antigen-presenting cell

Question 11

Why is there so much variation/mutation in HIV infection?

Answer 11

HIV lacks same checking mechanisms in DNA transcription

Question 12

Why is HIV mutation within the host problematic?

Answer 12

Escape from neutralising antibodies.

Escape from HIV-1-specific T cells.

Resistance and escape from antiretroviral drugs.

Question 13

Recall the 7 steps of the HIV life cycle

Answer 13

1. Binding: HIV binds to the host cell
2. Fusion: The HIV virus fuses with the cell membrane of the host cell which allows HIV contents including RNA, reverse transcriptase, integrase and other proteins to enter the cell.
3. Reverse Transcription: inside the cell, hiv rna is converted into dna using reverse transcriptase
4. Integration: integrase enzyme allows hiv dna to be integrated into the host dna
5. Replication: hiv can now produce long chains of hiv proteins which can be used to build more hiv
   6: assembly: hiv proteins and rna move to surface of cell to be assembled into immature hiv cells
6. Budding: immature hiv is pushed out of the cell and proteases activate immature hiv into mature infectious hiv cells

Question 14

Which drugs are capable of inhibiting the action of reverse transcriptase in HIV infection?

Answer 14

1. Nucleoside analogues

2. Non-nucleotide reverse transcriptases

Question 15

Which class of HIV drugs can prevent integration of viral DNA?

Answer 15

Integrase inhibitors

Question 16

Which HIV drugs can prevent modification of translated viral proteins?

Answer 16

Protease inhibitors

Question 17

What is the median time of infection with HIV to AIDS development?

Answer 17

8-10 years

Question 18

What does it mean if someone is an HIV exposed seronegative individual?

Answer 18

Partner of individual with HIV who remains uninfected

Question 19

What are the 3 major markers used to monitor HIV?

Answer 19

CD8
CD4
Plasma viral load

Question 20

What is long-term nonprogression of HIV?

Answer 20

Individual who is asymptomatic 10 years after infection

Question 21

How can HIV be detected?

Answer 21

anti-HIV antibodies (ELISA)

Viral load (PCR) - more sensitive

ELISA = initial screening test. Do Western Blot after to confirm (Gold standard)

Question 22

How are CD4+ T cell levels measured in HIV infection?

Answer 22

Flow cytometry

Question 23

What are the two methods of testing for ARV resistance?

Answer 23

Phenotypic

Genotypic (involves directly sequencing the amplified genome)

Question 24

Which drugs make up a HAART regimen?

Answer 24

Three or more drugs + one or more binding agents

Question 25

When should HAART treatment be initiated?

Answer 25

Immediately

Question 26

Give 2 examples of NRTI HIV drugs

Answer 26

Zidovudine

Lamivudine

Question 27

Recall 2 examples of Nucleotide RTI HIV drugs

Answer 27

Tenofovir

Adefovir

Question 28

What class of drug is raltegravir?

Answer 28

Integrase inhibitor (end in Gravir)

Question 29

Which drugs make up the HAART regimen initially?

Answer 29

2 NRTIs + NNRTI/boosted PI

Question 30

What CD4 count defines AIDS?

Answer 30

<200 cells/ nanolitre

Question 31

Which drugs make up the atripla pill?

Answer 31

Emtricitabine (Nucleoside RTI) + tenofovir (Nucleotide RTI) + efavirenz (NNRTI)

Question 32

Which ARV is best to use in pregnancy?

Answer 32

Zidovudine

Question 33

How can CD8+ T cells prevent HIV entry into cd4 cells?

Answer 33

Producing chemokines MIP-1A, MIP-1b and RANTES