Lecture 18: Retrovirus, Hepatitis virus, Prions - Chap 54, 55, 56 Flashcards
What is the significance of the 1911 discovery of Rous Sarcoma Virus?
It was the first virus shown to cause cancer.
Which retrovirus was linked to cancer in humans in 1981?
HTLV-1 (discovered by Robert Gallo)
How do retroviruses like HIV convert RNA to DNA?
Using reverse transcriptase.
What genetic material structure do retroviruses carry?
Two copies of positive-strand RNA.
Which genes are basic to all retroviruses?
gag, pol, and env.
Name two accessory genes found in HIV.
tat and nef.
Where does the HIV virus assemble inside the host?
Plasma membrane.
What enzyme in HIV cleaves proteins for virus assembly?
Protease.
What role does GP120 play in HIV infection?
It binds to CD4 on immune cells.
Which protein helps HIV fuse with cell membranes?
GP41.
What happens in the synthesis stage of HIV’s life cycle?
RNA is reverse transcribed to DNA.
How does HIV’s high mutation rate benefit the virus?
It helps evade immune detection.
What is the main impact of HIV on the immune system?
Destroys CD4+ T cells, weakening immunity.
What are nucleoside reverse transcriptase inhibitors (NRTIs) used for?
Blocking HIV’s reverse transcription.
How do protease inhibitors work against HIV?
They prevent the virus from maturing.
What is HBsAg and what does its presence indicate?
Hepatitis B surface antigen; indicates infection.
How does Hepatitis B virus (HBV) evade the immune system?
Produces non-infectious HBsAg particles.
What is the structure of HBV’s genome?
Partially double-stranded circular DNA.
Name the primary route of transmission for Hepatitis B.
Blood-to-blood contact.
What is the ‘Dane particle’ in HBV?
The fully infectious HBV particle.
Which hepatitis virus is the most environmentally stable?
Hepatitis A.
How does Hepatitis A typically spread?
Fecal-oral route, often via contaminated food or water.
What is a common long-term risk of chronic Hepatitis B and C?
Liver cancer.
How does Hepatitis C virus (HCV) enter liver cells?
By binding to receptors like CD81 and Claudin-1.
What diagnostic test detects PrP^Sc in prion diseases?
Proteinase K-resistant form detection in Western blot.
What is the main impact of prion proteins (PrP^Sc) in the brain?
They cause neurodegeneration and spongiform changes.
How is Creutzfeldt-Jakob Disease (CJD) most commonly transmitted?
Through ingestion of or exposure to infected tissue.
What makes prion diseases different from typical viral infections?
No immune response or inflammation.
Why are IV drug users at high risk for Hepatitis C?
Due to sharing needles, exposing them to blood.
What are protease inhibitors’ role in HIV treatment?
They block viral protein cleavage, stopping maturation.
What are signs of AIDS progression?
Low CD4 count and presence of opportunistic infections.
How does Hepatitis C virus (HCV) cause chronic infection?
By evading immune detection and establishing in the liver.
How is HIV primarily diagnosed?
Through antibody tests like ELISA and confirmatory Western blot.
What is the HIV ‘provirus’?
Integrated viral DNA within the host genome.
What are the high-risk factors for HIV?
Unprotected sex, IV drug use, and transfusions (in unscreened cases).
Which component of the HIV virus mutates frequently to avoid immunity?
GP120 protein.
What is the purpose of ART (antiretroviral therapy) in HIV?
To slow HIV progression and reduce viral load.
Which prion disease is associated with ritual cannibalism?
Kuru.
What disease can arise from consuming BSE-infected meat?
Variant Creutzfeldt-Jakob Disease (vCJD).
Why does Hepatitis C infection have a long ‘window period’?
Antibodies may take weeks to months to develop, delaying detection.
