Virology exam 1 review

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Variolation (inoculation)

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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

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what was variolation later improved to and by whom?

vaccination by Dr. Edward Jenner

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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)

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what type of microscope is needed to see viruses?

electron microscope

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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

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CPE: Syncytium formation

adjacent cells merge into a continuous mass (glob)

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CPE: inclusion bodies

compacted masses of viruses or damaged cell organelles in the nucleus and cytoplasm

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CPE: loss of contact inhibition

-Cells will now pile up on each other -Normal cells stop dividing when in contact with other cells

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who created the rabies vaccine?

Louis Pasteur

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types of vaccines

  1. prophylaxis (pre exposure)

  2. post-exposure

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How do attenuated vaccines work?

create a weaker infection that trigger immune response and memory without the full blown disease

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Baltimore Classification Scheme

based on relationship of viral genome to its mRNA

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Baltimore Classification Scheme Class I

dsDNA ex. herpes

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Baltimore Classification Scheme Class II

ssDNA that requires an intermediate ex. Parovirus

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Baltimore Classification Scheme Class III

dsRNA ex. Rotovirus

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Baltimore Classification Scheme Class IV

ssRNA that requires an intermediate ex. Coronavirus

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Baltimore Classification Scheme Class V

ssRNA that does not require an intermediate ex. Radbdovirus

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Baltimore Classification Scheme Class VI

ssRNA that uses reverse transcriptase to be dsDNA ex. retrovirus

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Baltimore Classification Scheme Class VII

dsDNA that is too short and uses a ssRNA intermediate ex. hepadenovirus

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one step growth curve

demonstrates the multiplication of viruses

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Viral replication Cycle

  1. attachment

  2. entry

  3. uncoating

  4. genome replication

  5. gene expression

  6. assembly

  7. release

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IRES

internal ribosome entry site

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acute infection

comes on rapidly, with severe but short-lived effects

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chronic infection

progress and persist over a long period of time slow replication ex. HPV

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latent infection

Persistent infection with recurrent symptoms that "come and go" ex. chickenpox

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prophage

the viral DNA that is embedded in the host cell's DNA

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host range

The limited range of host cells that each type of virus can infect and parasitize.

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how does a virus enter the body?

  1. respiratory tract

  2. GI tract

  3. bloodstream

  4. GU tract

  5. eyes

  6. skin

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how of the host range is determined by

viral attachment

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host receptors also determine

tissue tropism ( what can be infected)

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attachement is dependent on

capsid proteins NOT genomic payload

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what is an example of a virus that is acute latent?

varicella-zoster (chickenpox will later cause shingles as some of it stays hidden)

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viruses typically bind when the

spike proteins binds to receptor

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what will a virus do if it cannot immediately find a receptor?

weakly attach and tumble down till it can find a receptor

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HMO

-human milk oligosaccharides -80% chance that child won't get HIV from breast milk if it is HIV - at birth

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what part of the HIV envelope iniates attachement?

SU (gp120)

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CD4

primary host receptor

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how do we find host receptors for viruses?

  1. molecular cloning

  2. affinity binding

  3. immunological approach

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affinity binding

isolate cell surface proteins -> immbolize proteins in chromotography column -> test for virus binding

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immunological approach

mix virus w/ cell protein extract -> chemically induce crosslinking -> look to see what has bound to virus

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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

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what is critical in transitioning from attachement to uncoating

fusion protein

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fusion can take place

-plasma membrane -internally (more common): endosome or lyzosome

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typicall when something comes from the exterior of the cell to the interior, it becomes more

acidic, but some viruses take advantage of that

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how are the more important receptors determined

inducing certain mutations

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influenza spike proteins

  1. Hemagglutinin (HA)

  2. Neuraminidase (NA)

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what type of virus does not require a fusion protein

naked virus ex. polio

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fusion of enveloped virus

virus just fuses in

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endocytosis of an enveloped virus

engulfed vesicle forms around viral envelope most animal virues

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gp41

fusion protein

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gp120

primary binding protein

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what dictates where most of the replication will take place

genome

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viruses will utilize what to carry the virus to the nucleus?

cytoskeleton

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what is an example of a virus that has replicates unusually?

Reovirus

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how do plant viruses infect?

through broken/damaged parts (mechanical destruction from insects chewing) reproductive structures are also susceptible

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what structure in plants allow the spreading of a virus once its in?

plasmodesmata

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plant immune defense

chemicals that kill the tissues before further spreading

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sigma factor

helps direct RNA polymerase where to start

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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

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MS2 genes (4)

  1. coat

  2. RdRp gene

  3. A protein

  4. lysis protein

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what is RdRp

RNA dependent RNA polymerase

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which MS2 gene is in high abundance?

coat

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which MS2 gene is in low abundance?

lysis

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the phi chi 174/phi x 174 has a ___________ genome

circular

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bacteriophage lambda

-dsDNA

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how are the genes in bacteriophage lambda expressed? (3)

  1. immediate early

  2. delayed 3 late

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if the virus has a complicated structure, you can assume that there are lots of

enzymes structural proteins genome

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under good growth conditions, bacteriophage lambda favors

lysogeny

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under poor growth conditions, bacteriophage lambda favors

lytic

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lambda gene expression

  1. immediate early

  2. expression of N gene (transcriptional antiterminator) and protein (Pl promoter)

  3. Cro gene and protein (Pr promoter)

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what does the transcribing in bacteriophage lambda?

RNAP

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what does the N protein do?

binds to the terminator stem loop and recruits host protein

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what does Q protein do?

causes more antitermination which late gene expression

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rolling circle replication makes long

concatemers of DNA

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