8. HIV

Question 1

What conditions are associated with severe HIV?

Answer 1

Oral thrush - candida albicans 
Kaposi's sarcoma - raised purple lesions
Pneumocystis pneumonia (PCP)

Question 2

What is the outcome of patients with HIV?

Answer 2

Chronic infection (no cure) but no disability if managed properly.

Question 3

What is the structure of viruses?

Answer 3

Genome - either RNA or DNA, ds or ss
Capsid protein coat around genome - helical, icosahedral
Lipid envelope/ unenveloped - from host cell membranes

Question 4

What type of virus is HIV?

Answer 4

Retrovirus - ssRNA gest converted to DNA in cells, transcription into sRNA again.

Question 5

What is the structure of HIV?

Answer 5

ssRNA

Enveloped

Question 6

Which cells does HIV infect?

Answer 6

CD4+ cells

• T helped lymphocytes
• Monocytes, macrophages

Question 7

How does HIV damage hosts?

Answer 7

• Destroys the CD4+ cells
• Inflammation
• Spreads to/infects more cells

Question 8

How is HIV transmitted?

Answer 8

Sexual contact
Transfusion
Contaminated needles
Vertical - breast milk, transplacental, birth canal

Question 9

How does HIV enter CD4+ cells?

Answer 9

Binds to CD4 and co-receptors, fuses with the cell and contents released into the cell.

Question 10

Once in the cell, how does HIV virus replicate?

Answer 10

1. Reverse transcription of viral sRNA to DNA by reverse transcriptase enzyme
2. Integration of viral DNA into host genome by integrate enzyme.
3. Transcription of viral DNA during host replication.
4. Budding of immature virus
5. Maturation of immature virus - proteases

Question 11

What symptoms and signs might be present during the primary infection stage of HIV?

Answer 11

Flu-like or asymptomatic

Question 12

What happens during the primary infection phase of HIV?

Answer 12

Viral load is very high as virus enters tissue and lymph nodes, temporary drop in CD4+ cells.

Question 13

What happens in the latent infection phase?

Answer 13

Viral load decreases to a viral “set point”

The lower the set point, the longer it takes for viral load to increase again.

Question 14

Which stage(s) of HIV progression are asymptomatic?

Answer 14

Primary infection can be asymptomatic

Latent phase is asymptomatic

Question 15

How long can the latent phase last?

Answer 15

Months- years

Question 16

What happens in stage 3/symptomatic infection phase?

Answer 16

The viral load has increased and CD4+ cells are < 350 cells/ul.

Question 17

What happens in stage 4/ severe infection?

Answer 17

AIDS develops.
<200ul CD4+ cells.
Aids defining illnesses present.

Question 18

What are the main symptoms of acute HIV infection?

Answer 18

Systemic - fever, weight loss
Lymphadenopathy
Rash 
Hepatomegaly and splenomegaly
Nausea and vomiting
Sores and oral thrush
Myalgia

Question 19

What aids-defining illness’ occur when CD4+ cells reach 200ul?

Answer 19

PCP

Toxicoplasmosis

Question 20

What disease develops when CD4+ falls to 100ul?

Answer 20

Lymphoma

CMV

Question 21

What factors affect HIV transmission?

Answer 21

Type of exposure - anal sex is most risky
Viral load - transmission unlikely if undetectable
Condom use
Breaks in skin or mucosa

Question 22

What diagnostic tests can be used for HIV?

Answer 22

• Serology
• PCR
• “Rapid tests”

Question 23

How can HIV be detected using serology?

Answer 23

Both HIV antigen and HIV antibody

Question 24

What are the advantages and disadvantages of using serology to diagnosis HIV?

Answer 24

Results the same day

Can detect after 4 weeks, may get false negative result if taken too early

Question 25

How can PCR be used to diagnose HIV?

Answer 25

Detect HIV nucleic acid

Question 26

What are the advantages and disadvantages of using PCR to diagnose HIV?

Answer 26

Highly sensitive Detects very early (few days) But expensive, and results are slow (1 wk) so not used in initial screening

Question 27

How do rapid tests diagnose HIV?

Answer 27

Detect HIV antibody

Question 28

What are the advantages and disadvantages of using rapid tests?

Answer 28

Easy and quick - can be used for in home or postal testing Blood test (finger prick) or oral (saliva) If positive, need serology to confirm If negative then accurate

Question 29

What are the aims of HIV treatment?

Answer 29

- Undetectable viral load - Raise CD4+ count - Reduce general inflammation - Reduce risk of transmission - Normalise lifespan and QoL

Question 30

Why is there no HIV vaccine at present?

Answer 30

Viral envelop antigens are constantly changing during replication.

Question 31

What drugs are used to manage HIV?

Answer 31

Anti-retroviral drugs (ARVS)

Question 32

What proteins can ARVS target?

Answer 32

- Inhibit virus binding and fusing - Inhibit reverse transcriptase - Inhibit integrase - Inhibit protease

Question 33

How many ARVS should be given?

Answer 33

``` 3 in total: 2 x Nucleoside RT inhibitor and 1 other, either: Non-nucleoside transcription inhibitor Protease inhibitor Integrase inhibitor CCR5 entry inhibitor ```

Question 34

Why are 3 ARVS given?

Answer 34

Viral replication occurs at a rapid rate so resistance to drugs develops very quickly. Using 3 helps to overcome this.

Question 35

What other strategies can be used to treat and reduce HIV?

Answer 35

- Increase condom usage - Prevent mother-child transmission - ARV as prevention - Post-exposure prophylaxis (PEP) - Pre-exposure prophylaxis (PrEP)

Question 36

What ethical dilemma's can be involved in HIV diagnosis?

Answer 36

- Psychological impact - Dealing with stigma - Patient confidentiality vs health of mother, unborn child, sexual contact, older siblings and risk to other patients and healthcare workers.