Unit 4 General Flashcards
antigenic drift
Gradual change in amino acid sequence of flu on H or N surface antigens.
antigenic shift
Occurs in A type flu only. Occurs when novel H or N gene segment is introduced to humans.
Pandemic Criteria
- emergence of new flu subtype
- virus must infect humans and cause serious illness
- virus must have sustained human to human transmission and spread easily among humans
positive sense RNA virus
can be directly translated
negative sense RNA virus
requires RNA-dependent RNA polymerase for replication
dsRNA virus
requires RNA-dependent RNA polymerase for replication
plaque assays
measure infectivity of a sample
reverse transcriptase is required for what type of virus?
+ ssRNA virus with DNA intermediate
latent viral infection
initial infection followed by asymptomatic periods with occasional reactivation
cytotoxic T cells
- adaptive immune defense
- associated with killing virally infected cells
- CD8+
dsDNA virus
-conventional transcription and translation
gapped circular dsDNA
- translated into regular dsDNA, then to RNA then to protein
- RNA is reverse transcribed to make DNA for next virus?
- hepatitis B virus
ssDNA
- made to dsDNA
- transcribed to RNA and madd to protein
- also replicated into DNA for next virus
dsRNA
- encodes RNA dependent RNA polymerse (RdRp)
- can be translated into protein
ss(+)RNA
- translated directly into protein
- encodes RNA dependent RNA polymerase (RdRp)
- ex. SARS, yellow fever, hep C, HIV
ss(-)RNA
- encodes RNA dependent RNA polymerase (RdRp)
- NOT translated directly to protein
- translated into +RNA then into protein
ss(+)RNA with DNA intermediate
- +ssRNA is never used as a message
- ssRNA is converted to dsDNA with reverse transcriptase
- dsDNA intermediate integrates into host genome and is permanent (provirus)
Innate TLRs involved in antiviral response
TLR3 (dsRNA), TLR7 (viral RNAs, synthetic ligands), TLR9 (unmethylated CpG)
innate intracellcular restriction factor antiviral responses
- APOBEC
- TRIM5
- TLRs (3, 7, 9)
- helicases
innate anti-viral defense cells
- mononuclear phagocytes
- dendritic cells
- NK cells
- granulocytes
innate antiviral cytokines
-IFNs, IL1, TFNa, IL6, IL12, IL18
innate antiviral chemokines
- IL8, IP10, MIP1a
- chemical that will attract other cells
Innate Defense Mechanisms
- barriers
- intracellular restriction factors
- interferons
- anti-viral cells
- cytokines
- chemokines
innate interferons
-IFNs (type 1, type 2, jakstat, PKR (dec. protein synth), OAS (degrade mRNA))
adaptive antiviral cells
- B cells
- T cells
- macrophages
- hepatocytes
tissue tropism
-certain viruses prefer certain tissues over other
virulence
-ability of infection to cause disease
4 Types
- affect ability of virus to replicate
- modify host defense mechanisms
- facilitate virus spread
- directly toxic to host cells
acute local viral response
- short incubation times (1-3 days)
- IgA
- cold and diarrhea
- epithelial infection
- high likelihood of reinfection
acute systemic viral response
- longer incubation time (10-20 days)
- IgA and IgG
- low likelihood of reinfection
latent viruses
- HSV- dorsal root ganglia
- HPV-basal epithelial cells
- EBV-B lymphocytes
- VZV
- virus for MS?
