Viral Pathogenesis: Host responses to viral infections Flashcards
True or False: Innate defenses are immediate and non-specific.
True
What are the three general outcomes of viral infections of a cell?
- Abortive infection
- Lytic Infection
- Persistent Infection
What are the three categories persistent infections?
- Chronic
- Latent
- Transforming
What are the two types of cytopathic effects on virus infection?
- Direct cell damage
2. Indirect cell damage
Define permissive.
A cell that provides the machinery and components required for completion of viral replication. May result in latent or transforming infection.
Define non-permissive
A cell that does not provide the machinery and components required for completion of viral replication.
Name three types of innate defenses.
- Natural barriers (skin, mucus, etc.)
- Cells (macrophages, neutrophils, etc.)
- Soluble Factors (interferons, cytokines, etc.)
What are host restriction factors?
Intracellular blocks to viral replication that are part of the innate immune response.
True or False: Modern-day vertebrate innate immune system is optimized to defend against modern viral threats.
False. they are optimized to defend against ancient, extinct viruses.
Are toll-like receptors (TLRs) part of the innate immune or adaptive immune system?
Innate.
TLR3 recognize..
Double-stranded RNA
TLR4 recognize…
Fusion proteins and envelope protein
TLR7 and TLR8 recognize…
Imidazoquinoline and single-stranded RNA
TLR 9 recognize…
CpG-conting DNA
What does retinoic acid-inducible gene I (RIG-I)-like helicase recognize?
Viral nucleic acid
What is the role of type I interferons?
Antiviral cytokines secreted by most infected cells. Control genes whose transcription is regulated by ISREs.
What is the role of type II interferons?
Produced by T cells and NK cells. Controls genes whose transcription is regulated by GAS(gamma activated site)
What symptoms are likely to manifest upon sufficient release of IFN?
Fever, chills, nausea, and malaise
What is the role of PKR in IFN-induced anti-viral state?
Phosphorylates and therefore inactivates a cellular translation initiation factor to decrease protein synthesis.
What is the role of OAS in IFN-induced anti-viral state?
Degrades mRNA
Name five types of cells in the innate defense
- Mononuclear phagocytosis
- Dendritic Cells
- NK cells (contain virus)
- Granulocytes
True or False: Antibodies produced during primary virus infections are usually of lower affinity and often of the IgM isotype.
True
What type of antibody inhibits virion/host attachment and neutralizes toxins and enzymes?
IgA
What three functions does IgG play to prevent viral infection?
- Inhibits fusion of enveloped viruses with host membrane
- Opsonize virions to enhance phagocytosis (with IgM)
- can facilitate complement lysis of enveloped viruses (with IgM)
What three functions does IgM play to prevent viral infection?
- Can coat and agglutinate some virions
- Opsonize virions to enhance phagocytosis (with IgG)
- can facilitate complement lysis of enveloped viruses (with IgG)
What is APOBEC3G?
A human protein that interferes with the replication of HIV by incorporating itself into virus particles and damaging the genetic material of the virus.
What is Vif?
The HIV protein that blocks APOBEC activity can function in two ways: (1) by binding to APOBEC3G and preventing incorporation into virus particles; and (2) by targeting APOBEC3G for destruction and elmination.
What two interferons are considered type I interferons?
INF-alpha and INF-beta
What interferon is considered a type II interferon?
INF-gamma
Cells respond to IFN through receptors through which signalling pathways?
Jak/Stat
Name nine strategies to evade host defenses.
- Antigenic variation
- Inhibition of the INF pathway
- Inhibition of apoptosis and cell cycle control
- Immune tolerance
- Immunoprivilaged sites
- Infection of the immune system
- Restricted expression of viral genome (hide)
- Viral molecules that act as inhibitors or decoys
- Down regulation of host proteins
