99 Questions
What is viral tropism?
The ability of a virus to enter and replicate within specific cell types or tissues
What is persistent infection?
An infection that the host is unable to clear, usually following an acute stage
What are defense mechanisms to viral infections?
Physical and chemical barriers as well as symbiotic barriers that act as the innate defense against viral infections
What are methods used to determine viral virulence?
Mean time to death or symptom appearance, virulence in animal models, changes in blood parameters, or histological changes
What is the function of APOBEC proteins induced by RSV infection?
Enhance virus evolution
What is the role of immature dendritic cells at the site of infection?
Become mature and patrol tissues
What is the function of T1 cells?
Produce IL-2, IL-12, TNF-a, and IFN-gamma
What is the difference between persistent infection and latent infection?
Persistent infection is actively replicating the virus, while latent infection is not replicating
What is the role of viroceptors?
Sequester host-derived cytokines and chemokines
What is the study of viral pathogenesis and immunity about?
How viruses cause disease and the immune response to viral infections
What are the conditions required for a successful viral infection?
Contact with a susceptible host, exposure to sufficient viral inoculum, and successful attachment and entry into target cells
What is virus inoculum?
The number of virions that enter the body during an infection
What defines a latent infection?
Presence of a dormant viral genome and potential to reactivate
What is the characteristic of an acute infection?
Self-limiting infection with rapid onset and resolution
What is the role of antiviral defenses?
To limit disease by controlling or clearing the virus
What is a characteristic of indirect cell functions/characteristics caused by a viral infection?
$Cell transformation or oncogenesis$
What is the process through which healthy cells become transformed into cancer cells as a result of a viral infection called?
$Oncogenesis$
What is the imbalance between factors that promote disease and those that guard against it known as?
$Disease$
What are the characteristic signs of a symptomatic viral infection?
Fever, malaise, and aches due to pro-inflammatory cytokines
During which phase of disease can symptoms linger and wane?
Convalescence phase
What is the MOI (Multiplicity of Infection) of a virus?
The number of infectious viral particles added per target cell
How do persistent infections differ from recurrent infections?
Persistent infections involve continuous or intermittent pathogen multiplication, while recurrent infections occur after periods of latency
What are vertically transmitted viruses?
Viruses passed from a pregnant mother to her fetus or newborn during childbirth or through breast milk
How do the structural characteristics of viruses allow them to resist adverse conditions?
By having an outer protective capsid that shields them from unfavorable environmental conditions
What are the general properties of a virus that make it toxic and pathogenic?
Membrane and accessory proteins known to trigger cell destruction
What is the role of adaptive immune response in combating viral infections?
It targets specific viral pathogens and works to eliminate them
What is the mode of transmission for genital transmission of viruses?
Transmitted through sexual contact or contact with infected genital secretions
What is polarized cells in the context of virology?
Cells with structural and functional asymmetries, such as neurons and muscle cells
What is syncytia formation in the context of virology?
Process of cell-to-cell membrane fusion, leading to the formation of multinucleated giant cells
What are naked viruses in the context of virology?
Viruses that do not have an envelope and cause disease by destroying infected tissue
How does a virus like Rhinovirus cause the common cold?
It elicits a strong host immune response, which leads to increased inflammation and respiratory symptoms
What is the term used to describe the morphological changes to a cell caused by a viral infection?
Cytopathic effect
What is the term for the decrease in virulence or ability to cause harm in a virus due to mutations in the viral genome?
Virus restriction
Which factor guards against disease by providing a barrier to viral infection through examples such as skin, mucous membranes, and body secretions?
Physicochemical barriers
Can all viral infections lead to disease?
No, not all viral infections result in disease
Which stage of viral diseases involves the replication of viruses in target tissues?
Replication in target tissue
During which stage of progression can some infections go undetected?
Asymptomatic or subclinical infection
What are examples of cyclic viral infections?
Urogenital herpes and Varicella and zoster
What is the term for an organism that serves as a carrier for a virus, providing safe transit and potentially amplifying the virus's numbers?
Vector
What do inclusion bodies refer to in the context of viral infections?
Viral particles in the nucleus of infected cells
How do viruses like RSV and influenza cause respiratory diseases?
By triggering inflammatory responses leading to tissue damage
What is bone marrow suppression?
A decrease in the production of blood cells due to virus-induced cell death or altered immune activity within the bone marrow
What is the purpose of fusion sessions?
To encourage preparation, attendance, and participation through learning content completion
What is the process by which mutations are naturally introduced in viruses, such as RNA viruses?
Antigenic Shift
How do cells recognize viral infections?
Through TLR3 and RLRs
What is the primary site through which a virus enters the host's body?
Gastrointestinal Transmission
What is the primary method of spread of viruses through ingestion of contaminated food or water?
Gastrointestinal Transmission
Which pathway can lead to IFN-α/ß-mediated apoptosis in infected cells?
$2’-5’-oligo(A) synthetase/RNase L pathways$
What type of pathogenic effects are caused by the virus itself?
Direct/viral damage
What is a strategy used by some viruses to inhibit NK cell response?
$dsRNA binding proteins$
What is the restrictive barrier that limits access to the central nervous system?
$Blood-Brain Barrier (BBB)$
Which event leads to the accidental incorporation of a segment from one virus strain into another?
$Antigenic Shift$
What produces inhibitory fatty acids and RNases that can be harmful to viruses?
$Skin and mucosa$
'Herpetic Lesions' are skin lesions caused by which type of viruses?
$Herpetic Lesions$
What pathogen can cause cell lysis as well as persistent infections?
$Hepatitis B$
What is the consequence of MHC-I- and MHC-II-restricted antigen presentation?
Virus degradation and upregulation of MHC molecules
What is ID50?
Measure of the number of particles required to cause symptoms in 50% of hosts
What are some inflammatory mediators responsible for the signs and symptoms of a viral infection?
IL-6, IL-1β, TNF-α
What is one explanation for why one identical twin might overcome a viral flavivirus while the other does not?
Nutritional status
What is the role of interferon λ in the immune response?
Response to ssRNA viruses and TLR7/TLR8-responsive viruses
How does IFN-α/ß stimulate apoptosis?
By increasing the cellular concentration of inactive PKR
What is the consequence of macrophages recognizing the virus?
Secretion of IL-12 and TNF-a for immune response
What are the pathogenic effects of erythrovirus (Parvovirus B19)?
Bone marrow suppression leading to disorders like aplastic crisis
What are gene products that are toxic?
Virus gene products that cause cellular damage
What is one strategy used by viruses to block the TAP transporter and inhibit MHC molecule synthesis?
Inhibition of antigen processing
What is the role of commensal or mutualistic microorganisms in viral infections?
Interfering with viral infections by modifying pH levels or producing microbial inhibitors
What are permissive cells in the context of viral infections?
Cells that are able to support the entire viral replication cycle
What is the consequence of deterioration of factors guarding against disease?
Increased susceptibility to infection and exacerbation of existing disease
What is the steady state of viral load within a few weeks or months after infection called?
Viral Set Point
What is a common strategy used by viruses to achieve high yields?
High replication rate
What is the difference between acute and cyclic viral infections?
Acute infections involve rapid clearance by the immune system, while cyclic infections involve latent periods and potential for recurring disease
What are essential genes in the context of virology?
Genes absolutely necessary for virus replication and survival
What is the spread of viruses through inhalation of respiratory droplets or contact with contaminated surfaces referred to as?
Respiratory Transmission
What is the long-term presence of a virus in the body referred to as?
Persistent Infection
What are non-essential genes in virology?
Genes that are not necessary for virus survival
What do permissive cells do in the context of viral infections?
Support viral replication and production of progeny virions
What is the process by which a virus must gain access to a host, infect susceptible cells, and evade antiviral defenses in order to cause disease known as?
Overcoming Host Defenses
What is the role of natural killer (NK) cells in the immune system?
Recognizing and eliminating infected or abnormal cells
What is tissue tropism in the context of viral infections?
The tendency of certain viruses to selectively infect certain tissues or organs
What happens when a cell recognizes it is infected?
The cell responds by expressing type I interferons
What is antigen presentation in the context of the immune system?
The process where a pathogen is recognized by phagocytic cells, then activated to engage naive lymphocytes into a T1 response
What are escape mutants in the context of viral infections?
Viruses that modify their antigenic surface to evade the host's immune system
What defines quasispecies in the context of virology?
A collection of similar viruses within a single host that arise from replication errors
What type of interferon responses (stress responses) are particularly important as an initial means of viral containment?
Type I interferons (IFN-α & IFN-ß) and type III interferons (IFN-λ)
What is the role of PKR in the cell?
Inhibiting protein synthesis leading to apoptosis upon type I IFN stimulation
What is APOBEC in the context of virology?
Viral proteins that impede virus replication at various stages of the cycle
What are virokines in the context of virology?
Viral proteins that serve as homologs of host cytokines and chemokines
What happens upon type I IFN stimulation in a cell?
The cellular concentration of inactive PKR increases
What is the role of natural killer (NK) cells in the immune system?
Recognizing and eliminating infected or abnormal cells
What is the process of antigen presentation?
Recognition of pathogens by phagocytic cells and activation to engage naive lymphocytes
What happens when a cell recognizes it is infected?
The cell expresses type I interferons and their receptor for activation
What is the role of PKR in the cell?
Activating translation initiation factor eIF2
What are virokines in the context of viral infections?
Viral proteins that dampen the host's T1 response
What is antigenic variation in virology?
The process by which viruses evade host immune responses through mutations in the genes responsible for encoding antigens
What is the role of MICA and MICB in viral infections?
Recognized by some CD8 T lymphocytes
What are escape mutants in virology?
Viruses that modify their antigenic surface to evade the host's immune system
What is quasispecies in virology?
A collection of similar viruses within a single host arising from replication errors
What is tissue tropism in virology?
The tendency of viruses to infect various tissues or organs within the host
What is meant by stress response in the context of virology?
A mechanism triggered by viral infections or cellular stress leading to interferon production
Test your knowledge of the body's first line of defense against viral infections and cellular stress, including the role of interferon proteins and the type of signaling that leads to the activation of appropriate genes to address a particular pathogen. Explore how macrophages and dendritic cells are activated, along with the secretion of cytokines for immune response.
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