Virology (Thiele) Flashcards
(31 cards)
Which viruses can Slip through memb without binding receptors?
1) Parvovirus
2) Rhinovirus
- both small and it happens by chance
How do most viruses enter a cell?
Receptor mediated endocytosis
-Viral Receptor and a VAP(on virus)
Uncoating
DNA Virus- endocytosed, capsid travels to nucleus where it releases DNA. Capsid uncoating
RNA Virus- uncoating done more rapidly, RNA released into the cytosol. Nucleoprotein uncoating
Monocystronic
Each mRNA produces one specific protein
Polycistronic
- Each MRNA produces multiple proteins on THE SAME poly peptide chain
- Cleave large protein into smaller proteins
Monopartite
All genes are found on single strand of DNA or RNA
Multipartitie
Virlar genes are distributed between several strands of DNA or RNA
-Together=GENOME
Positive Strand
can be read by host ribosomes
negative strand
can NOT be read by host genomes
- packaged in capsid with its own RNA dep, RNA poly
- must synthesize complementary strand before translating
Three phases of viral proteins
1) Intermediate Early
2) Early
3) Late
Intermediate Early
Makes proteins that allow virus to takeover cell
Early
Makes enzymes to replicate and begins replication of Viral genome
Late
Makes structural proteins (E.g. Capsid and Glycoproteins
-DNA is packaged at the nucleus
Retroviruses
Capsid contains RNA dep DNA poly packaged with the RNA
-reverse transcribes the RNA upon uncoating
Viral Mutations
1) Recombination- intramolecular genetic exchange b/w virus and host
2) Reassortment-“grab bag” all genes into a compartment and randomly selected out in groups to make new “viral strands”
3) Transcapsidation- protein capsid from virus A, genome from virus B
4) Marker Rescue- Lethal mutants recombine with helper virus to make mutant viable again
What can happen when a virus infects a cell?
1) Abortive- host not permissive(no receptors, inapprop temps, not right enz)
2) Lytic- not what viruses want to do (CPEs-holes in memb, degrading nuclear mater and proteins)
3)Persistent Infections (Chronic, Latent, Recurring)-cells replicate for generations with releasing much virus
-patching, capping, shedding
-Latent infections
- Transformation- removal of “brakes from cell cycle”
-
What is an inclusion body?
aggregate of VIRAL proteins, RNA, or DNA
- used diagnostically
- -> Cowdry type inclusion body=HSV - SEEN IN LYTIC INFECTION
What is a synctia?
Result of cell fusion.
VAPs bind and form Multinucleated Giant Cell
-SEEN OFTEN in RSV
-Lytic infection
Main ways virus evades immune system?
1) Patching- aggregates MHC in clumps
2) Capping-aggregates MHC on one end of cell
3) Shedding- Makes tons of MHC and sheds receptors to prevent immune cells from binding to virally infected cell
Latent Virus
not multiplying , Hiding from immune system
-Source of recurrent infections
How does interferon help viral infections?
Decrease infection to surrounding cells
Incubation Period
Period of time between exposure to symptoms
- a virus gains access to cell and is starting to produce more virus
Prodrome
Non-Specific symptoms prior to the presentation of the disease
Drome
Clinical illness (Chicken pox symptoms)
