3-Virology Flashcards
virus
definition
tiny acellular obligate parasite
-nucleic acid/genome + protein coat/capsid
how viruses replicate
assembly of pre formed components NOT binary fission (like bacteria)
virus components
genome (segmented or continguos)+ capsid surrounded by
1. matrix/tegument
2. envelope
3. viral attachment proteins
genome types
DNA- single or double
RNA- single (neg or pos sense) or double
pos sense ssRNA
can be recognized to make proteins
neg sense ssRNA
not recognized for protein syn right away
-need to be turned into pos sense
ssDNA families
- parvoviridae
dsDNA families
- papillomaviridae
- polyomaviridae
- adenoviridae
- herpesviridae
- poxviridae
- hepadnaviridae
HAPPY
mneumonic
H = herpes, hepadna
dsRNA families
- reoviridae
-ssRNA families
- ortomyxo
- paramyxo
- rhabdo
- bunya
- arena
- filo
+ssRNA
- matona
- flaviv
- corona
- retro
- picorna
- calici
- hepe
end in viridae
RNA virus properties
- labile and transient bc easier to kill
- repl in cytoplasm
- cells cannot rep RNA- viruses must encode an RNA dependent RNA polymerase or have it packaged in virion itself
- prone to mutation so evade immune sys
capsid shapes
-helical/tube/slinky
-icosahedral, like letter die
-complex, mixture of helical and icosahedral
naked capsid viruses
non enveloped
-spread easily, survive in adverse conditions even if dry out, resistant to detergents
-kill cells that they infect bc released by lysis
-all gastroenteritis viruses non eveloped
enveloped viruses
-adapted to rely on lipid layer for infectious so must stay in moist environ
-not survive GI tract, disrupted by pH
-not need to kill cell to spread
life cycle summary
- attachment
- entry
direct fusion
attachment and entry simultaneous
-enveloped viruses only
receptor mediated endocytosis entry
for non enveloped viruses
-lysis vesicle after endocytosed
transcription
DNA
mRNA productin dep on genome-
dsDNA good bc can use transcription machinery
ssDNA similar just extra step to make ds
transcription +ssRNA
no enzyme needed to convert to mRNA
-still need RdRp encoded
can directly produce protein
transcription retroviruses
reverse transcribe into dsDNA
viral RdRp
for -ssRNA and dsRNA to convert to mRNA
-ssRNA needs to carry RdRp in virion too
-ssRNA mneumonic
always
bring
polymerase
or
fail
replication
assembly process
- indiv viral proteins form into capsid subunits
- subunits combo for complete capsid
- viral genome selectively packaged
- envelope acquired
- exit cell
- mature
budding
way to leave cell
-pushes thru plasma membrane then pinched off
point mutation accumulation
from poor proofreading capacity of many viral polymerases
-if change produces advantage for virus
viral recombination
use cell’s machinery to combine
viral reassortment
infection types
- acute- burst of rep before immune sys clears
- chronic- burst of rep but immune reduces instead of clears after
- latent- burst, immune sys stops in certain tissues, reactivates in other tissues
syncytia formation
multinucleated cells from fusing together
-infected + uninfected
plaque assay
grow monolayer
add sample
look for plaques (1 virus infects and spreds to adj cells, little hole in monolayer)
quantitative for infectious agents
antibodies
EISA
westerna blot
genomes
DNA, PCR RNA, RT-PCR
viral antigesn
ELISA
others
