HIV

Question 1

Some background facts about HIV (retrovirus)

Answer 1

Discovered in 1983
Was transferred from chimps to humans
1st anti-retro viral introduced in 1987 in zidovudine

HAART highly active anti-retro viral treatment

Question 2

Characteristics of human immunodeficiency virus

Answer 2

100nm
Has a lipid envelope, cone shaped capsid
2 copies of positive single stranded RNA
Possesses enzymes and proteins

Question 3

Function of GP-120

Answer 3

Allows virus entry and is the binding site for CD4 cells

Question 4

Function of GP-41

Answer 4

Is the transmembrane anchor

Question 5

What protects the virus from neutralising antibodies

Answer 5

The fact that the virus is heavily glycosylated

Question 6

What the enzymes that viruses possess

Answer 6

Reverse transcriptase = RNA to DNA
Protease = cleavage of long viral polypeptide into shorter functional units
Ribonuclease = breaks down RNA a
Integrase = pro viral DNA into host cell’s chromosomes

Question 7

How is HIV transmitted

Answer 7

As is a blood borne virus would be spread through sexual contact
Blood transfusions
Infected organs or tissues
Contaminated equipment
Mother to fetal spread in transplacental, delivery or breastfeeding

Question 8

What are the life cycle stages of a virus

Answer 8

Attachment
Fusion
Reverse transcription
Integration
Replication
Assembly
Budding
Maturation

Question 9

What is pneumocystis jiroveci pneumonia and common symptoms:

Answer 9

Infection caused by a fungus that leads to dry cough, fever and shortness of breath

Spread by inhalation of droplets

People with HIV and those on corticosteroids are highly at risk

Question 10

How is PCP diagnosed and treated

Answer 10

Diagnosed via examining sputum, bronchoalveolar lavage, PCR or X-ray

Treated with trimethoprim or sulfomethoxazole
Combination of both called cotrimoxazole

Question 11

Symptoms of HIV primary infection

Answer 11

Fever, headaches, lymphadenopathy, mouth/genital ulcers, rash and viral meningitis
Cold/flu like symptoms

Question 12

Examples of AIDS defining illnesses

Answer 12

> 200 CD4 count = skin conditions and mucosal conditions such as shingles, thrush

CD4 50-150 = infections such as PJP, toxocoplasmosis and malignancies such as cervical cancer and lymphoma

CD4 <50 MAC, CMV, PML, lymphoma

• TB can be caught at any CD4 count but normally at low CD4
• MAC = mycobacterium Avium complex

Question 13

Mechanism of action of reverse transcriptase inhibitors

Answer 13

NRTI = nucleoside reverse transcriptase inhibitor
Eg zidovudine

NtRNI = nucleotide reverse transcriptase inhibitor
Both above lack hydroxyl group in molecule so more DNA nucleotides can’t be added after that. Blocks synthesis of chain

NNRTI non nucleoside reverse transcriptase inhibitors - bind to reverse transcriptase and inhibit DNA polymerase

Eg efavirenz

• difference between NRTI and nnrti is that nnrti is non competively inhibition whilst NRTI is competitive inhibition

Question 14

Mechanism of action of integrase inhibitors and example

Answer 14

Prevent transfer of viral DNA to cellular DNA by blocking enzyme binding to viral DNA
Eg raltegravir

Question 15

Mechanism of action of protease inhibitors and example

Answer 15

Competitively inhibit viral protease which prevents cleaving of long viral polypeptide
Eg darunavir

Question 16

Role of ritonavir

Answer 16

Enhances activity of protease inhibitors as it reduces its metabolism by the liver so it can be sustained at higher concentrations