AP-Micro Viral Pathogenesis 2 — Questions and Answers
Question 1: Which viral mechanism allows a pathogen to avoid destruction by cytotoxic T lymphocytes (CTLs)?
- Downregulating MHC class I expression on infected cells (Correct answer)
- Upregulating MHC class II on host cells
- Increasing interferon-gamma secretion
- Enhancing natural killer cell recognition
Correct answer: Downregulating MHC class I expression on infected cells
Many viruses, including herpesviruses and HIV, downregulate MHC class I to prevent CTLs from recognizing and killing infected cells.
Question 2: What is the role of viral neuraminidase in influenza pathogenesis?
- Facilitates viral entry into host cells
- Cleaves sialic acid to release new virions from cell surfaces (Correct answer)
- Inhibits interferon signaling
- Integrates viral RNA into the host genome
Correct answer: Cleaves sialic acid to release new virions from cell surfaces
Neuraminidase cleaves sialic acid residues on host cell surfaces, releasing newly assembled influenza virions so they can spread to new cells.
Question 3: During viral latency, herpes simplex virus (HSV) genome is maintained in what form within sensory neurons?
- Integrated into the host chromosome
- As a circular episome in the nucleus (Correct answer)
- As single-stranded RNA in the cytoplasm
- Packaged in incomplete virions
Correct answer: As a circular episome in the nucleus
HSV maintains its genome as a circular episomal DNA in the nucleus of sensory neurons during latency, without integrating into host chromosomes.
Question 4: Which term describes the ability of a virus to infect and replicate in multiple different tissue types?
- Viremia
- Tropism
- Pantropic (Correct answer)
- Teratogenic
Correct answer: Pantropic
A pantrophic virus has broad tissue tropism, meaning it can infect and replicate in many different cell and tissue types throughout the body.
Question 5: How do non-cytopathic viruses cause host cell damage without directly killing the infected cell?
- By triggering massive apoptosis
- By provoking immune-mediated destruction of infected cells (Correct answer)
- By producing toxins that lyse adjacent cells
- By blocking protein synthesis completely
Correct answer: By provoking immune-mediated destruction of infected cells
Non-cytopathic viruses cause damage primarily through the host immune response, where CTLs and antibodies destroy virally infected cells.
Question 6: What is meant by 'viral shedding' in the context of pathogenesis?
- Loss of the viral envelope during cell entry
- Release of infectious viral particles from the host into the environment (Correct answer)
- Degradation of viral proteins by proteasomes
- Budding of virions from the nuclear membrane
Correct answer: Release of infectious viral particles from the host into the environment
Viral shedding refers to the release of infectious virus from an infected host into secretions or excretions, enabling transmission to new hosts.
Question 7: Ebola virus causes hemorrhagic fever partly by infecting which cell type, leading to systemic immune dysregulation?
- Erythrocytes
- Macrophages and dendritic cells (Correct answer)
- B lymphocytes
- Platelets
Correct answer: Macrophages and dendritic cells
Ebola virus infects macrophages and dendritic cells, impairing adaptive immune responses and triggering a cytokine storm that damages blood vessels.
AP-Micro Viral Pathogenesis 2
Which viral mechanism allows a pathogen to avoid destruction by cytotoxic T lymphocytes (CTLs)?