Lecture 18: Retrovirus, Hepatitis virus, Prions - Chap 54, 55, 56

Question 1

What is the significance of the 1911 discovery of Rous Sarcoma Virus?

Answer 1

It was the first virus shown to cause cancer.

Question 2

Which retrovirus was linked to cancer in humans in 1981?

Answer 2

HTLV-1 (discovered by Robert Gallo)

Question 3

How do retroviruses like HIV convert RNA to DNA?

Answer 3

Using reverse transcriptase.

Question 4

What genetic material structure do retroviruses carry?

Answer 4

Two copies of positive-strand RNA.

Question 5

Which genes are basic to all retroviruses?

Answer 5

gag, pol, and env.

Question 6

Name two accessory genes found in HIV.

Answer 6

tat and nef.

Question 7

Where does the HIV virus assemble inside the host?

Answer 7

Plasma membrane.

Question 8

What enzyme in HIV cleaves proteins for virus assembly?

Answer 8

Protease.

Question 9

What role does GP120 play in HIV infection?

Answer 9

It binds to CD4 on immune cells.

Question 10

Which protein helps HIV fuse with cell membranes?

Answer 10

GP41.

Question 11

What happens in the synthesis stage of HIV’s life cycle?

Answer 11

RNA is reverse transcribed to DNA.

Question 12

How does HIV’s high mutation rate benefit the virus?

Answer 12

It helps evade immune detection.

Question 13

What is the main impact of HIV on the immune system?

Answer 13

Destroys CD4+ T cells, weakening immunity.

Question 14

What are nucleoside reverse transcriptase inhibitors (NRTIs) used for?

Answer 14

Blocking HIV’s reverse transcription.

Question 15

How do protease inhibitors work against HIV?

Answer 15

They prevent the virus from maturing.

Question 16

What is HBsAg and what does its presence indicate?

Answer 16

Hepatitis B surface antigen; indicates infection.

Question 17

How does Hepatitis B virus (HBV) evade the immune system?

Answer 17

Produces non-infectious HBsAg particles.

Question 18

What is the structure of HBV’s genome?

Answer 18

Partially double-stranded circular DNA.

Question 19

Name the primary route of transmission for Hepatitis B.

Answer 19

Blood-to-blood contact.

Question 20

What is the ‘Dane particle’ in HBV?

Answer 20

The fully infectious HBV particle.

Question 21

Which hepatitis virus is the most environmentally stable?

Answer 21

Hepatitis A.

Question 22

How does Hepatitis A typically spread?

Answer 22

Fecal-oral route, often via contaminated food or water.

Question 23

What is a common long-term risk of chronic Hepatitis B and C?

Answer 23

Liver cancer.

Question 24

How does Hepatitis C virus (HCV) enter liver cells?

Answer 24

By binding to receptors like CD81 and Claudin-1.

Question 25

What diagnostic test detects PrP^Sc in prion diseases?

Answer 25

Proteinase K-resistant form detection in Western blot.

Question 26

What is the main impact of prion proteins (PrP^Sc) in the brain?

Answer 26

They cause neurodegeneration and spongiform changes.

Question 27

How is Creutzfeldt-Jakob Disease (CJD) most commonly transmitted?

Answer 27

Through ingestion of or exposure to infected tissue.

Question 28

What makes prion diseases different from typical viral infections?

Answer 28

No immune response or inflammation.

Question 29

Why are IV drug users at high risk for Hepatitis C?

Answer 29

Due to sharing needles, exposing them to blood.

Question 30

What are protease inhibitors’ role in HIV treatment?

Answer 30

They block viral protein cleavage, stopping maturation.

Question 31

What are signs of AIDS progression?

Answer 31

Low CD4 count and presence of opportunistic infections.

Question 32

How does Hepatitis C virus (HCV) cause chronic infection?

Answer 32

By evading immune detection and establishing in the liver.

Question 33

How is HIV primarily diagnosed?

Answer 33

Through antibody tests like ELISA and confirmatory Western blot.

Question 34

What is the HIV 'provirus'?

Answer 34

Integrated viral DNA within the host genome.

Question 35

What are the high-risk factors for HIV?

Answer 35

Unprotected sex, IV drug use, and transfusions (in unscreened cases).

Question 36

Which component of the HIV virus mutates frequently to avoid immunity?

Answer 36

GP120 protein.

Question 37

What is the purpose of ART (antiretroviral therapy) in HIV?

Answer 37

To slow HIV progression and reduce viral load.

Question 38

Which prion disease is associated with ritual cannibalism?

Answer 38

Kuru.

Question 39

What disease can arise from consuming BSE-infected meat?

Answer 39

Variant Creutzfeldt-Jakob Disease (vCJD).

Question 40

Why does Hepatitis C infection have a long 'window period'?

Answer 40

Antibodies may take weeks to months to develop, delaying detection.