40 Questions
What is the primary mechanism by which interferons inhibit virus replication?
By degrading viral mRNA
Which type of interferon is involved in activating macrophages?
Gamma interferon
What is the characteristic of Natural Killer cells that allows them to recognize and destroy infected cells?
They recognize cells that do not display class I MHC proteins
Which type of RNA virus is the most potent inducer of interferons?
Double-stranded RNA virus
What is the mechanism by which Natural Killer cells kill infected cells?
By releasing granzymes
What is the primary function of viruses producing receptors for immune mediators such as IL-1 and TNF?
To prevent the activation of antiviral processes
What is the term for individuals who produce virus for long periods of time and can serve as a source of infection for others?
Carrier state
What type of host defense against viruses is comprised of interferons and natural killer cells?
Nonspecific immunity
Which type of infection is characterized by a long incubation period, often measured in years?
Slow virus infection
What is the main site of disease for slow virus infections such as progressive multifocal leukoencephalopathy?
Brain
What is a characteristic of viruses that distinguishes them from cells?
They are capable of independent replication
What is the structure composed of nucleic acid genome and capsid proteins?
Nucleocapsid
What is the symmetry of a viral nucleocapsid?
Spherical (icosahedral) symmetry or helical symmetry
What is the size range of viruses?
~20 nm to ~300 nm
What is the function of the capsid?
To cover the genome
Why can't the presence of IgG be used to diagnose a current infection?
Because IgG can be due to a past infection
What is the significance of a fourfold or greater increase in antibody titer in the convalescent serum sample?
It is used to diagnose a current infection
What is the 'gold standard' in viral diagnosis?
The presence of viral DNA or RNA
What is the purpose of labeled probes in viral diagnosis?
To identify specific viral nucleic acids
What is the purpose of reverse transcriptase in viral diagnosis?
To amplify small amounts of viral nucleic acids
What is the result of phenotypic mixing between two different viruses?
The progeny viruses can infect cells of species that the parental viruses could not.
What is the term for transmission of a virus from mother to offspring?
Vertical transmission
What is an example of a virus that uses the surface antigen of another virus as its outer coat protein?
Hepatitis D virus
What is the term for the process by which one virus produces a protein that can be used by another virus?
Complementation
What are the main portals of entry for viral infection?
Respiratory, gastrointestinal, and genital tracts
What is the process by which two different viruses infect the same cell and progeny viruses contain proteins of both parental viruses?
Phenotypic mixing
What is the term for the process by which segments of the genome RNA of influenza virus are exchanged?
Reassortment
What is the incubation period of a viral infection?
The period before symptoms appear
What are the four stages of viral infection in a person?
Incubation, prodromal, specific-illness, and recovery
What is the term for the transmission of a virus from one individual to another?
Horizontal transmission
What is the primary function of viral surface proteins?
To mediate attachment to host cell receptors
What is the purpose of matrix proteins in viral structure?
To link viral proteins and envelope proteins
What is a characteristic of enveloped viruses?
They are easily inactivated
What determines the host and organ specificity of a virus?
Viral surface proteins
What is a characteristic of naked viruses?
They survive longer in the environment
What is the result of adsorption of an enveloped virus to two cells at the same time?
Cell fusion
What is unique about the genome of parvoviruses?
It is single-stranded
Where do DNA viruses replicate, except for poxviruses?
Nucleus
What is the typical function of early proteins in viral replication?
Enzymes used in synthesis of viral components
How do poliovirus and retroviruses translate their mRNA?
Into precursor polyproteins
This quiz covers the role of interferons in nonspecific defenses, including their mechanism of action in inhibiting virus replication and inducing the synthesis of a ribonuclease.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
