Podcast
Questions and Answers
How do nonenveloped viruses typically attach to host cells?
How do nonenveloped viruses typically attach to host cells?
- Through lipid bilayer interactions
- Via protein spikes
- Through endocytosis directly
- By using their capsid proteins (correct)
What method do enveloped viruses use to enter a host cell?
What method do enveloped viruses use to enter a host cell?
- Cell lysis
- Direct injection of nucleic acid
- Endocytosis or membrane fusion (correct)
- None of the above
What occurs during the uncoating phase of viral infection?
What occurs during the uncoating phase of viral infection?
- The host immune response is activated
- Viral proteins are transported out of the nucleus
- Virions are assembled
- The capsid disassembles and is digested (correct)
How are new virions released from enveloped viruses?
How are new virions released from enveloped viruses?
What characterizes a chronic persistent viral infection?
What characterizes a chronic persistent viral infection?
Which method is primarily used to cultivate most animal viruses?
Which method is primarily used to cultivate most animal viruses?
What is a major limitation of the ELISA test?
What is a major limitation of the ELISA test?
Which technique is commonly used to detect viral genetic material?
Which technique is commonly used to detect viral genetic material?
What is required for reverse transcriptase (RT) in RT-qPCR?
What is required for reverse transcriptase (RT) in RT-qPCR?
What triggers flare-ups in latent persistent infections?
What triggers flare-ups in latent persistent infections?
What is the primary role of leukocytes in the immune response?
What is the primary role of leukocytes in the immune response?
Which of the following structures is primarily responsible for filtering lymph?
Which of the following structures is primarily responsible for filtering lymph?
Which type of leukocyte is known for its role in fighting parasites and causing allergies?
Which type of leukocyte is known for its role in fighting parasites and causing allergies?
What class of antimicrobial peptides rapidly kill invaders by disrupting cell membranes?
What class of antimicrobial peptides rapidly kill invaders by disrupting cell membranes?
Where does the maturation of T cells occur?
Where does the maturation of T cells occur?
What condition indicates an increase in leukocytes in the blood?
What condition indicates an increase in leukocytes in the blood?
What is the main physical barrier to pathogens in the human body?
What is the main physical barrier to pathogens in the human body?
What happens to lymph nodes when they detect an invading microbe?
What happens to lymph nodes when they detect an invading microbe?
What is indicated by a high cycle threshold (Ct) value in a PCR test?
What is indicated by a high cycle threshold (Ct) value in a PCR test?
Which characteristic makes designing antiviral drugs challenging?
Which characteristic makes designing antiviral drugs challenging?
What is the role of interferons in the immune response?
What is the role of interferons in the immune response?
Which of the following is NOT a mechanism of innate immunity?
Which of the following is NOT a mechanism of innate immunity?
Which drug is known to inhibit viral DNA replication?
Which drug is known to inhibit viral DNA replication?
What do nucleoside reverse transcriptase inhibitors (NTRIs) target?
What do nucleoside reverse transcriptase inhibitors (NTRIs) target?
What happens when prions are ingested?
What happens when prions are ingested?
Which physiological barrier helps to trap pathogens that enter the respiratory system?
Which physiological barrier helps to trap pathogens that enter the respiratory system?
How do antimicrobial peptides (AMPs) function?
How do antimicrobial peptides (AMPs) function?
What concept does the hygiene hypothesis suggest?
What concept does the hygiene hypothesis suggest?
Which of the following is an example of adaptive immunity?
Which of the following is an example of adaptive immunity?
Which antiviral drug is used as a preventive measure shortly after suspected exposure to rabies?
Which antiviral drug is used as a preventive measure shortly after suspected exposure to rabies?
What property of viruses poses a challenge for antiviral drug development?
What property of viruses poses a challenge for antiviral drug development?
Which of the following statements is true regarding innate immunity?
Which of the following statements is true regarding innate immunity?
What type of viruses are obligate intracellular pathogens and cannot survive outside of a host cell?
What type of viruses are obligate intracellular pathogens and cannot survive outside of a host cell?
Which of the following is NOT a feature of viral capsids?
Which of the following is NOT a feature of viral capsids?
What distinguishes enveloped viruses from naked viruses?
What distinguishes enveloped viruses from naked viruses?
Which viral genome type is directly translated by host cell ribosomes?
Which viral genome type is directly translated by host cell ribosomes?
What is the primary reason that RNA viruses mutate more frequently than DNA viruses?
What is the primary reason that RNA viruses mutate more frequently than DNA viruses?
What is antigenic drift?
What is antigenic drift?
How does antigenic shift occur?
How does antigenic shift occur?
The capsid of most animal viruses is primarily composed of what?
The capsid of most animal viruses is primarily composed of what?
What property is NOT used in the classification of viruses?
What property is NOT used in the classification of viruses?
Which of the following best describes a cytopathic effect of a viral infection?
Which of the following best describes a cytopathic effect of a viral infection?
Which of the following viruses typically has a segmented RNA genome?
Which of the following viruses typically has a segmented RNA genome?
What role do viral spikes (peplomers) play in the viral life cycle?
What role do viral spikes (peplomers) play in the viral life cycle?
The process through which beneficial mutations in viruses enable them to escape host immune detection is known as what?
The process through which beneficial mutations in viruses enable them to escape host immune detection is known as what?
Which of the following is NOT a characteristic of single-stranded RNA viruses?
Which of the following is NOT a characteristic of single-stranded RNA viruses?
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Study Notes
Viruses and Prions
- Viruses are acellular obligate intracellular pathogens.
- 70% of human viruses are zoonotic.
- Virion: A single, infectious virus particle.
- Capsid: Protein shell that packages and protects the genome.
- Enveloped viruses: Have a lipid based envelope surrounding the capsid.
- Naked/nonenveloped virus: Does not have an envelope.
- Viral spikes: Protrude from the capsid or envelope.
- Viral genomes can be RNA or DNA, single or double-stranded, segmented or non-segmented, linear or circular.
- Viral genomes change over time, due to their rapid replication rate and lack of proofreading capabilities in RNA polymerases.
- Antigenic Drift: Minor changes to the HA and NA spikes due to error-prone RNA polymerase.
- Antigenic Shift: Major changes to genetic reassortment, usually occurs when two or more strains of a virus combine to create a new subtype.
- Important DNA viral families:
- Papillomaviridae (human papillomaviruses)
- Herpesviridae (herpes, varicella-zoster virus/chickenpox)
- Poxviridae (smallpox)
- Important RNA viral families:
- Coronaviridae (SARS, SARS-CoV-2, common colds)
- Flaviviridae (Hepatitis C virus, West Nile Virus, Dengue fever virus)
- Retroviridae (HIV)
- Parmyxoviridae (Measles & mumps)
- Orthomyxoviridae (Influenza)
- Animal Virus Replication:
- Attachment: Viral proteins bind to host cell receptors.
- Penetration: Nonenveloped viruses enter by endocytosis; enveloped viruses enter by endocytosis or membrane fusion.
- Uncoating: Capsid is degraded in cytoplasm, nucleus, or endocytic vesicle.
- Replication: Genome replication and viral protein synthesis.
- Assembly: New virions are formed.
- Release: Enveloped viruses bud off; nonenveloped viruses kill the host cell.
- Acute infections: Viruses infect a host cell and new virions are immediately made.
- Persistent infections: Replication strategies allow viruses to avoid immune clearance.
- Chronic persistent infections: Continuous release of virions over time with slow progression.
- Latent persistent infections: Flare-ups with intermittent periods of dormancy; virions are shed during flare-ups.
- Prions: Infectious proteins that cause transmissible spongiform encephalopathies (TSEs).
- Misfolded proteins: Associated with neurodegenerative diseases.
- Hygiene hypothesis: Decreases in diversity and levels of microbes in the microbiota may negatively affect immune responses.
Innate Immunity
- Ancient protection in all eukaryotes.
- Generalized, lacks specificity and memory.
- Mechanical barriers: Prevent pathogen spread by rinsing, flushing, or trapping.
- Chemical barriers: Directly attack invaders or establish environments that limit pathogen survival.
- Antimicrobial Peptides (AMPs): Proteins that destroy a wide spectrum of pathogens.
- Physical barriers: Epithelial tissue lines every body cavity and entrance; skin serves as a major physical barrier.
- Lymphoid tissues: filter lymph and screen for antigens.
- Primary lymphoid tissues: Site of leukocyte production and maturation (thymus and bone marrow).
- Secondary lymphoid tissues: filter lymph and sample body sites for antigens (lymph nodes, spleen, and MALT).
- Leukocytes: White blood cells.
- Granulocytes: cells with granules in their cytoplasm.
- Agranulocytes: lack granules in their cytoplasm.
- Neutrophils: Most abundant white blood cells; phagocytize foreign cells and viruses.
- Eosinophils: Fight parasites or cause allergies.
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