Viruses

Question 1

What are the two most common routes of transmission for HIV?

Answer 1

Blood and semen

Question 2

Which family is HIV part of?

Answer 2

Retroviridae family

Question 3

What was HIV previously known as and why?

Answer 3

GRID - Gay related infectious disease

Was seen in large numbers of gay men

Question 4

How many people are infected with HIV worldwide each year?

Answer 4

36.9 million

Question 5

How many people die from HIV related deaths each year worldwide?

Answer 5

1.2 million

Question 6

Which genus is HIV part of?

Answer 6

Lentivirus

Question 7

How many HIV virions can replication produce in a day?

Answer 7

10^10

Question 8

How many groups does HIV-1 contain and what are they?

Answer 8

3 - M, N and O

Question 9

There are two main types of HIV - what are they?

Answer 9

HIV-1 and HIV-2

Question 10

Which HIV-1 group is the most prevalent?

Answer 10

M

Question 11

How many subtypes does group M have?

Answer 11

8 subtypes

Question 12

Which M group subtype is most commonly found in America and Europe?

Answer 12

Subtype B

Question 13

Can HIV be transmitted through saliva?

Answer 13

No

Question 14

How long can HIV survive in a reused needle?

Answer 14

42 days

Question 15

What are three common routes of HIV transmission?

Answer 15

Blood, semen, pre-seminal fluid, vaginal fluid, rectal fluids, breast milk

Question 16

Give an example of an activity where the risk of HIV transmission is high and explain why

Answer 16

Drug user sharing needles - HIV can survive on a reused needle for 42 days, penetrated into skin where it can reach the mucosal membrane
Rape victim - often violent which can create tears, allowing easier transmission into blood
Anal or vaginal sex
Birth - tears, damaged skin, lots of bodily fluids allowing risk for transmission/contact

Question 17

Give an example of a less common route of HIV transmission

Answer 17

From mother to child during pregnancy
Birth
Breast feeding

Question 18

Give an example of a lower risk route of HIV transmission

Answer 18

Oral sex
Blood transfusions
Organ transplants
Bites
Pre-chewed foods

Question 19

Give three features of stage 1 of HIV - acute infection

Answer 19

Single virion - 80% of mucosal infected individuals in B and C
Occurs around 10 days before vRNA is detectable
Within 2-4 weeks post infection may have flu-like symptoms that may last for a few weeks
Very infectious - virion production is at its highest
Asymptomatic

Question 20

What type of cell do HIV prefer to bind to?

Answer 20

CD4+ T cell

Question 21

At which stage of HIV infection is an individual most infectious?

Answer 21

Stage 1 - acute infection

Virion production is at its highest (plus individuals unlikely to know they’re infectious)

Question 22

What are the three stages of HIV infection?

Answer 22

Stage 1 - acute infection
Stage 2 - clinical latency
Stage 3 - AIDS

Question 23

What is stage 2 (clinical latency) of HIV infection?

Answer 23

Asymptomatic
Virus reproduces at lower levels (less infectious)
Viral load increases
CD4+ T cells decrease

Question 24

Roughly how long can a HIV +ve individual last in the clinical latency stage of infection with medication?

Answer 24

15+ years

Question 25

Roughly how long can a HIV +ve individual last in the clinical latency stage of infection without medication?

Answer 25

Around 10 years

Question 26

What is stage 3 (AIDS) of HIV infection?

Answer 26

Weakened immune system from reduced CD4+ T cells (now make up <14% of the total lymphocyte population) Severe repeating illness, infections and opportunistic infections

Question 27

How long does a patient with AIDS typically survive?

Answer 27

3 years

Question 28

In AIDS, what percentage of the total lymphocyte population are CD4+ T cells?

Answer 28

<14%

Question 29

Give four symptoms of AIDS

Answer 29

``` Fever Chills Diarrhoea Fatigue Weakness Weight loss Sweats Swollen lymph glands Blurred vision Night sweats Symptoms of recurrent, opportunistic infections: TB, pneumonia, fungal infections, HSV ```

Question 30

Which virus is the envelope protein Gp120 found on?

Answer 30

HIV

Question 31

What is the role of Gp120?

Answer 31

It is a docking glycoprotein found on the HIV envelope essential for virus entry. Binds to CD4 and the co-receptor, inducing a conformational change to allow gp41 to penetrate the cell membrane

Question 32

What does HIV need to bind to on the host cell for viral entry?

Answer 32

CD4 and a co-receptor (either CXCR4 or CCR5)

Question 33

Which co-receptor used by HIV for viral entry is primarily found on CD4+ T cells?

Answer 33

CXCR4

Question 34

Which molecule is thought to be linked to HIV viral entry?

Answer 34

Cholesterol

Question 35

Describe the HIV lifecycle

Answer 35

``` HIV receptor gp120 binds to CD4 and co-receptor (CCR5 or CXCR4). This causes a conformational change that allows gp41 transmembrane protein to penetrate the cell membrane. The matrix and capsid protein are essentially digested, releasing the viral enzymes and RNA. The viral RNA is reverse transcribed into viral DNA using host nucleotides. Reverse transcriptase can then do this again to produce dsDNA. dsDNA forms a pre-integration complex (p17, integrate and VPR) which is transported to the nucleus vDNA creates a circular long terminal repeat. Viral integrase (p32) can then remove host chromosomal DNA and insert the vDNA ```

Question 36

The CD4 co-receptor CCR5 is primarily found on which cells?

Answer 36

T cells, macrophages, monocytes and DCs

Question 37

What is the viral protein p32?

Answer 37

Integrase (HIV)

Question 38

What are p16 and p14 (Tat)?

Answer 38

Transcriptional transactivators that bind to LTR

Question 39

How does HIV replicate?

Answer 39

p16 and p14 bind to LTR p19 binds to vDNA and transports it to the cytoplasm RNA polymerase II produces viral mRNA Host ribosomes translate viral proteins (Tat, Rev, Gag and Env) Env assembled in the golgi pathway and buds from host cell As the virus buds from the host cell, it takes the lipid bilayer as the viral envelope Virus inserts gp120 through the lipid bilayer

Question 40

Where is Env assembled in the HIV replication cycle?

Answer 40

Env is assembled in the golgi pathway (exact mechanism is unknown)

Question 41

What is the result when there is a switch from CCR5 to CXCR4 co-receptor binding?

Answer 41

Increased AIDS progression

Question 42

How long after peak viral load do T-cells to the original HIV virus peak?

Answer 42

1-2 weeks after peak viral laod

Question 43

What do T cells usually target in HIV infection?

Answer 43

Env (envelope protein), then Gag and Pol

Question 44

What is Gag (HIV)?

Answer 44

Capsid and matrix proteins

Question 45

What is Pol (HIV)?

Answer 45

Viral polymerase/enzymes

Question 46

In HIV infection, Abs generated targeted which viral proteins?

Answer 46

gp41 and gp120