1 intro to virology

Question 1

what is the best way to see viruses?

Answer 1

electron miroscope

Question 2

what does polythetic mean?

Answer 2

The taxonomic method adopted for use in virology is polythetic, meaning that any given virus group is described using a collection of individual properties”.

Question 3

Possible properties that could be used for classification:?

Answer 3

Question 4

wht does an icosahedral virus look like and what does a naked virus look like? and an enveloped helical?

Answer 4

Question 5

what are the shapes of the capsid?

what are the 2 ways that the capsids can be packages?

Answer 5

they can be icosahedral or helical

then both of those forms can be naked or enveloped.

Question 6

what form of RNA can be made into +mRNA?

Answer 6

-RNA

Question 7

how does baltimore type 4 get form +RNA to -DNA?

Answer 7

Reverse transcriptase.

Question 8

what is a viron?

Answer 8

the viral particle

Question 9

what is an infectious particle?

Answer 9

virus

Question 10

what does MOI mean?

Answer 10

multiplicity of infection

Question 11

what does CPE?

Answer 11

cytopathic effect

Question 12

what is teh word describing the spread of a virus through the body via the blood stream.

Answer 12

viremia

Question 13

what does a plaque assay detect?

Answer 13

titration of the number fo the infections progeny. each unit is a PFU or plaque forming unit.

Question 14

what is a focus forming assay?

Answer 14

for looking at viruses that promote cell growth rather than death.

Question 15

what is a single step growth curve?

Answer 15

provides quantitation of “burst size”

Question 16

what does virons contain?

Answer 16

Question 17

what are attachment proteins and fusion proteins for?

Answer 17

they are for binding and entry.

Question 18

what is the difference between viral replication and bacterial replication?

Answer 18

bacteria is fusion

viruses make new exact DNA copies of them selves.

Question 19

what are the basic steps in the viral lifecycle?

Answer 19

Question 20

how do all virons attach?

Answer 20

a viral surface protien attaches to a receptor on the target cell.

Question 21

what are the cell surface recpeptors made of ?

Virus recognition of its receptor is important for

determining?

Answer 21

proteins or carbs.

o host range (human vs other hosts)

o cell tropism

Question 22

what is the receptor for HIV?

Answer 22

human CD4 on t

Question 23

what is the receptor fo r the epstein barr virus?

Answer 23

human complemenat receptor CD21

Question 24

what is teh receptor for epstein barr virus?

Answer 24

human ICAM-1

Question 25

what is the receptor for the influenza virus

Answer 25

sialic acid

Question 26

how do naked viruses get in the cell?

Answer 26

through endocytosis and they are surrounded by the endosomal membrane.

Question 27

what are the 2 ways that envoloped viruses can get into the cell?

Answer 27

1. by using thier glycoprotein to fuse the virus and cell membrane, releasing the capsid into the cytoplasm.
2. some enveloped are taken up by endocytosis. then fused with an acid endosomal compartent releases capsid.

Question 28

what kind of replication enzymes do cells not have?

Answer 28

ones that

copy RNA to RNA, or RNA to DNA

Question 29

all viruses must synthesize _______ to make proteins

Answer 29

all viruses must synthesize + mRNA to make proteins

Question 30

 all viruses use host ribosomes to synthesize viral proteins, although viral proteins may modify their translational specificity

 viruses can use host or viral machinery to modify proteins (e.g. phosphorylate)

Answer 30

true

Question 31

 many viruses use, divert, or modify cellular membranes for replication and assembly

Question 32

many viruses “shut-off” host macromolecular synthesis; others manipulate the cell cycle of the host to provide the best replicative environment

Question 33

how are many naked viruses released?

Answer 33

many depend on cell lysis for release

Question 34

how are most enveloped viruses released?

Answer 34

they bud at the plasma membrane.

Question 35

what happens in a productive infection?

Answer 35

generally leads to cytopathic effect with a burst of virus production

Question 36

what happens in a latent infection?

Answer 36

no production of infectious virus particles, but genetic information of the virus remains

Question 37

Persistent infection ?

Answer 37

there is chronic virus procution

Question 38

what is an abortive infection?

Answer 38

where the virus life cycle is inclomples nad the virus is lost.

Question 39

what is a syncytia?

Answer 39

membrane fusion of adjacent cells to form giant,

multi-nucleate cells called syncytia

Question 40

what are some acute cytopathic effects of viruses on host cells?

Answer 40

 membrane fusion of adjacent cells to form giant,

multi-nucleate cells called syncytia

 shut off of host metabolism

 induction of apoptosis

 cell death – necrosis

Question 41

what is the virus effect fo cell transformation?

Answer 41

loss of normal growth control, “oncogenic potential”

out of control growth.

Question 42

what is tropism?

Answer 42

a way that a virus will go look for and attach to a certain type of cell.

Question 43

how do viruses do tropism?

Answer 43

• receptor
• tissue-specific cellular components required for infection

(eg., transcription factors, miRNAs)
• tissue-specific restriction factors that abort infection • temperature or pH or activating proteases

(eg., periphery vs. core, intestinal)

Question 44

how do viruses spread between contacts?

Answer 44

Transmission: • respiratory
• fecal/oral
• direct contact

sexually transmitted

parenteral (blood borne)
• indirect contact (fomites or vectors)

Question 45

how do viruses cause disease?

Answer 45

virus destruction of infected cells
viral modification of infected cell function
 immune and inflammatory responses to virus infection

 fever, rash, myalgia
 immune-mediated damage or destruction of cells or

tissues

combination of several factors

Question 46

what are the the innate responses of the host?

Answer 46

soluble mediators: interferons (IFNs), cytokines, chemokines antiviral response within infected cell make surrounding cells resistant to infection recruit effector cells (NK cells, macrophages)

apoptosis: programmed cell death to avoid release of infectious virus

Question 47

what is teh adaptive immune response humorla?

Answer 47

neutralizing antibody: block attachment or entry

complement fixing antibody: lyse virions or infected cells

Question 48

what is teh cell mediated adaptive response?

Answer 48

MHC presentation of viral peptides:

killing of virus-infected cells by cytotoxic T cells

Question 49

what is teh host defence of the memory response?

Answer 49

they will resist reinfection.

from the B and T cells.