AP-Micro Viral Pathogenesis 3 — Questions and Answers
Question 1: Which type of viral infection is characterized by a long incubation period and slow progressive disease?
- Acute infection
- Slow viral infection (Correct answer)
- Latent infection
- Abortive infection
Correct answer: Slow viral infection
Slow viral infections, such as those caused by prions or subacute sclerosing panencephalitis (SSPE) from measles virus, have incubation periods of years before symptoms appear.
Question 2: What is the primary reason RNA viruses mutate more rapidly than DNA viruses?
- RNA viruses replicate faster
- RNA-dependent RNA polymerases lack proofreading ability (Correct answer)
- RNA viruses have larger genomes
- RNA viruses integrate into host DNA
Correct answer: RNA-dependent RNA polymerases lack proofreading ability
RNA-dependent RNA polymerases (RdRp) lack 3'-to-5' exonuclease proofreading activity, leading to error rates ~10,000 times higher than DNA polymerases.
Question 3: How does poliovirus cause paralysis in infected individuals?
- By destroying anterior horn motor neurons in the spinal cord (Correct answer)
- By infecting the cerebral cortex and causing seizures
- By demyelinating peripheral sensory nerves
- By triggering autoimmune destruction of neuromuscular junctions
Correct answer: By destroying anterior horn motor neurons in the spinal cord
Poliovirus selectively infects and destroys lower motor neurons in the anterior horn of the spinal cord, causing flaccid paralysis in the affected limbs.
Question 4: Which viral pathogenesis mechanism is exemplified by EBV-associated Burkitt's lymphoma?
- Direct cytolysis
- Viral oncogenesis via insertional mutagenesis
- Transformation via viral oncoproteins disrupting cell cycle control (Correct answer)
- Immunosuppression leading to opportunistic cancer
Correct answer: Transformation via viral oncoproteins disrupting cell cycle control
EBV encodes oncoproteins (e.g., LMP1) that mimic activated growth receptors, driving uncontrolled B-cell proliferation and contributing to Burkitt's lymphoma development.
Question 5: What is a cytokine storm, and why is it particularly dangerous in viral pathogenesis?
- A localized inflammatory response that clears infection efficiently
- Dysregulated overproduction of cytokines causing widespread tissue damage (Correct answer)
- A targeted release of interferons that block viral replication
- Cytokine-mediated recruitment of NK cells to infected tissues
Correct answer: Dysregulated overproduction of cytokines causing widespread tissue damage
A cytokine storm is an excessive, uncontrolled release of pro-inflammatory cytokines that damages host tissues and organs, sometimes more severely than the virus itself.
Question 6: Which property allows HIV to establish a latent reservoir in resting CD4+ T cells that persists despite antiretroviral therapy?
- HIV's ability to mutate its surface antigens constantly
- Integrated proviral DNA in non-dividing cells is transcriptionally silent (Correct answer)
- HIV-encoded proteases destroy antiretroviral drugs inside cells
- Resting T cells lack the receptor needed for antiretroviral entry
Correct answer: Integrated proviral DNA in non-dividing cells is transcriptionally silent
HIV provirus integrated into the genome of resting CD4+ T cells is transcriptionally inactive, making these cells invisible to the immune system and unaffected by antiretrovirals.
Question 7: What distinguishes a primary viremia from a secondary viremia in the course of viral infection?
- Primary viremia occurs after secondary; both cause the same symptoms
- Primary viremia spreads virus from initial site to regional lymph nodes; secondary spreads to target organs (Correct answer)
- Primary viremia is more severe and secondary is clinically silent
- Primary viremia only occurs in immunocompromised patients
Correct answer: Primary viremia spreads virus from initial site to regional lymph nodes; secondary spreads to target organs
Primary viremia is the initial low-level spread of virus from the entry site to regional lymph nodes, while secondary viremia represents amplified dissemination to distant target organs.
AP-Micro Viral Pathogenesis 3
Which type of viral infection is characterized by a long incubation period and slow progressive disease?