Virology exam 1 review

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Variolation (inoculation)
the method first used to immunize an individual against smallpox with material taken from a patient in the hope that a mild, but protective infection would result
what was variolation later improved to and by whom?
vaccination by Dr. Edward Jenner
The filtering device shown in the ppt had porcelin pores too small for bacteria to pass through, but ..........
something smaller than bacteria was able to pass through (aka viruses)
what type of microscope is needed to see viruses?
electron microscope
CPE (cytopathic effect)
a visible effect on a host cell, caused by a virus, that may result in host cell damage or death ex. changes in cell morphology
CPE: Syncytium formation
adjacent cells merge into a continuous mass (glob)
CPE: inclusion bodies
compacted masses of viruses or damaged cell organelles in the nucleus and cytoplasm
CPE: loss of contact inhibition
-Cells will now pile up on each other -Normal cells stop dividing when in contact with other cells
who created the rabies vaccine?
Louis Pasteur
types of vaccines
1. prophylaxis (pre exposure) 2. post-exposure
How do attenuated vaccines work?
create a weaker infection that trigger immune response and memory without the full blown disease
Baltimore Classification Scheme
based on relationship of viral genome to its mRNA
Baltimore Classification Scheme Class I
dsDNA ex. herpes
Baltimore Classification Scheme Class II
ssDNA that requires an intermediate ex. Parovirus
Baltimore Classification Scheme Class III
dsRNA ex. Rotovirus
Baltimore Classification Scheme Class IV
ssRNA that requires an intermediate ex. Coronavirus
Baltimore Classification Scheme Class V
ssRNA that does not require an intermediate ex. Radbdovirus
Baltimore Classification Scheme Class VI
ssRNA that uses reverse transcriptase to be dsDNA ex. retrovirus
Baltimore Classification Scheme Class VII
dsDNA that is too short and uses a ssRNA intermediate ex. hepadenovirus
one step growth curve
demonstrates the multiplication of viruses
Viral replication Cycle
1. attachment 2. entry 3. uncoating 4. genome replication 5. gene expression 6. assembly 7. release
internal ribosome entry site
acute infection
comes on rapidly, with severe but short-lived effects
chronic infection
progress and persist over a long period of time slow replication ex. HPV
latent infection
Persistent infection with recurrent symptoms that "come and go" ex. chickenpox
the viral DNA that is embedded in the host cell's DNA
host range
The limited range of host cells that each type of virus can infect and parasitize.
how does a virus enter the body?
1. respiratory tract 2. GI tract 3. bloodstream 4. GU tract 5. eyes 6. skin
how of the host range is determined by
viral attachment
host receptors also determine
tissue tropism ( what can be infected)
attachement is dependent on
capsid proteins NOT genomic payload
what is an example of a virus that is acute latent?
varicella-zoster (chickenpox will later cause shingles as some of it stays hidden)
viruses typically bind when the
spike proteins binds to receptor
what will a virus do if it cannot immediately find a receptor?
weakly attach and tumble down till it can find a receptor
-human milk oligosaccharides -80% chance that child won't get HIV from breast milk if it is HIV - at birth
what part of the HIV envelope iniates attachement?
SU (gp120)
primary host receptor
how do we find host receptors for viruses?
1. molecular cloning 2. affinity binding 3. immunological approach
affinity binding
isolate cell surface proteins -> immbolize proteins in chromotography column -> test for virus binding
immunological approach
mix virus w/ cell protein extract -> chemically induce crosslinking -> look to see what has bound to virus
molecular cloning
mRNA from permissive cell is obtained and converted into cDNA library -> inserted into nonpermissive cells (one of which will now contain the receptor protein ) -> a previosly non permissive will become permissive -> recover and sequence
what is critical in transitioning from attachement to uncoating
fusion protein
fusion can take place
-plasma membrane -internally (more common): endosome or lyzosome
typicall when something comes from the exterior of the cell to the interior, it becomes more
acidic, but some viruses take advantage of that
how are the more important receptors determined
inducing certain mutations
influenza spike proteins
1. Hemagglutinin (HA) 2. Neuraminidase (NA)
what type of virus does not require a fusion protein
naked virus ex. polio
fusion of enveloped virus
virus just fuses in
endocytosis of an enveloped virus
engulfed vesicle forms around viral envelope most animal virues
fusion protein
primary binding protein
what dictates where most of the replication will take place
viruses will utilize what to carry the virus to the nucleus?
what is an example of a virus that has replicates unusually?
how do plant viruses infect?
through broken/damaged parts (mechanical destruction from insects chewing) reproductive structures are also susceptible
what structure in plants allow the spreading of a virus once its in?
plant immune defense
chemicals that kill the tissues before further spreading
sigma factor
helps direct RNA polymerase where to start
T7 DNA replication proteins
1. gp 2.5 (viral) : ss binding protein 2. gp 4 (viral): helicase and primase 3. gp 5 (viral): polymerase 4. Trx (host): aid processivity
MS2 genes (4)
1. coat 2. RdRp gene 3. A protein 4. lysis protein
what is RdRp
RNA dependent RNA polymerase
which MS2 gene is in high abundance?
which MS2 gene is in low abundance?
the phi chi 174/phi x 174 has a ___________ genome
bacteriophage lambda
how are the genes in bacteriophage lambda expressed? (3)
1. immediate early 2. delayed 3 late
if the virus has a complicated structure, you can assume that there are lots of
enzymes structural proteins genome
under good growth conditions, bacteriophage lambda favors
under poor growth conditions, bacteriophage lambda favors
lambda gene expression
1. immediate early 2. expression of N gene (transcriptional antiterminator) and protein (Pl promoter) 3. Cro gene and protein (Pr promoter)
what does the transcribing in bacteriophage lambda?
what does the N protein do?
binds to the terminator stem loop and recruits host protein
what does Q protein do?
causes more antitermination which late gene expression
rolling circle replication makes long
concatemers of DNA