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Virology > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

What type of enzymes do viruses possess and what are their functions ?

A

1) lysins- produced by bacteriophage to cleave host walls 2) retroviral- (HIV), injects genetic material into infected cell 3) reverse transcriptase- create cDNA 4) nucleic acid polymerase- viral genome replication 5) neuraminidases: cleave glycosidic bonds to release the virus

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2
Q

What allows for replication of defective viruses?

A

Mixed infections and a helper virus

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3
Q

What is a defective integrating particle (DIP)?

A

Defective virus integrates its own DNA into an active virus to deactivate it.

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4
Q

What type of virus is used for a vaccine ?

A

Pseudovirus-there is nucleic acid in the capsid instead of the virus

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5
Q

What do Hog Cholera and Classical swine fever have in common ?

A

Same disease, different name Both caused by pestivirus

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6
Q

What do Hand-foot mouth disease and Foot and Mouth disease have in common ?

A

Different disease, different name Hand,foot, mouth-enterovirus Foot and mouth- aphthorvirus

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7
Q

Class I

A

without reverse transcriptase-DNA, double stranded

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8
Q

Class II

A

without reverse transcriptase, DNA, single stranded

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9
Q

Class III

A

without reverse transcriptase, RNA double stranded

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10
Q

Class IV

A

without reverse transcriptase, RNA, single stranded: + sense

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11
Q

Class V

A

without reverse transcriptase, RNA, single stranded: - sense

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12
Q

Class VI

A

with reverse transcriptase, DNA to single stranded + sense RNA

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13
Q

Class VII

A

with reverse transcriptase, RNA to double stranded DNA

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14
Q

What is the only group allowed to classify viruses?

A

ICTV

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15
Q

Bornaviridae

A

single strand linear-RNA negative sense Borna disease-horses: ataxia, cats: posterior paresis

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16
Q

Astroviridae

A

single strand linear-RNA positive sense Astrovirus enteritis Avian nephritis

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17
Q

Prions

A

Scrapie-sheep and goats BSE

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18
Q

What are the 5 types of proteins found in viruses?

A

1) enzymes 2) viral non structural proteins 3) structural proteins 4) inhibitors 5) regulatory

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19
Q

What do viruses need to live?

A

A living host cell

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20
Q

What are three ways to cultivate a virus?

A

Lab animals, tissue culture, embryonated egg inoculation

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21
Q

What is a suspension cell culture?

A

Cells that do no need to attach to anything to grow

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22
Q

What is a monolayer cell culture ?

A

Continuous layer of cells that grow on the culture plate

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23
Q

What is a primary cell culture?

A

Cells directly from the parent line with the same number of chromosomes, and same chromosomes as the parent

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24
Q

What are advantages and disadvantages of a primary cell culture?

A

Advantage: used for viral vaccines, best culture used to grow viruses, close to parent line, heterogenous Disadvantage: easy to contaminate, difficult to grow, short life span, may not be the same as parent line

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25
Q

What is a subculture, and why do we do it?

A

Also called passage, but used to transfer cells to a new vessel. It is used to allow for continuous growth/provide fresh nutrients.

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26
Q

What does the primary cell culture become after the first subculture?

A

Cell line: Continuous or finite

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27
Q

Finite/definitive cell line characteristics are…

A

Possess contact inhibition, maintain original morphology/chromosomes, homogenous population, can be cultured 100x before death, slow growth rate (24-96hrs), less hassle to use, derived from embryos or subculture

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28
Q

Continuous cell line characteristics are…

A

Infinite amount of replications, growth rate is fast (12-24 hrs), not approved for vaccines, derived from cancerous cells or induced, hassle free, genetically weird

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29
Q

What are the 3 morphologies a cell line can be?

A

Fibroblastic, epithelial-like, lymphoblast-like Fibroblastic and Epithelial-like grow on a substrate Lymphoblast-like grow in suspension

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30
Q

Examples of culture media…

A

Eagle’s Basal Medium, Leibovitz L-15 Medium

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31
Q

Characteristics of serum in media are…

A

Growth: 5-10% Maintenance: 0-2% Fetal bovine serum is most commonly used Provides- growth factors, nutrients, attachment and spreading factors, adhesion factors, hormones Regulate cell membrane permeability Carrier proteins

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32
Q

What does phenol red pH indicator test for ?

A

Contamination (will be red)

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33
Q

How much CO2 should be used in cell culture experiments ?

A

4-10%

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34
Q

T/F-antimicrobial agents are used in cell culture

A

T- it prevents contamination

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35
Q

What does culture media provide for cells ?

A

Vital nutrients necessary for the cells to grow.

Ex. Leibovitz L-15 Medium

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36
Q

What is the serum in culture media for, and what are the two that are used ?

A

Adhesion, attachment, hormone, growth and spreading factors.

Molecular weight nutrients

Carrier proteins for lipid substances and trace elements

Regulate cell membrane permeability

Ex. Growth Medium: 5-10%, Maintenance Medium: 0-2%

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37
Q

What tasty animal to we obtain the serum from ?

A

Fetal bovine serum

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38
Q

What is the significance of a color change when using phenol red pH indicator ?

A

Contamination in your culture or you’re lazy and left the cell culture in the same plate for too long!

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39
Q

T/F- you have to use 4-10% CO2 when using media buffered with a CO2-bicarbonate based buffer..

A

TRUE

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40
Q

Since we’re going to be virologists..tell me about the cell line and optimal temperatures they need…

A

Human/Mammals:36-37C

Insect: 27C

Avian: 38.5C

Cold-blooded animals: 15-26C

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41
Q

What proteases would you use for cell cultures ? Do you even care ?

A

Trypsin, Collagenase….. yas, because it’s on the exam. Also, one day I might say screw veterinary medicine and become a virologist.

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42
Q

T/F-It doesn’t matter how long you incubate cell cultures in high trypsin concentrations. What do researchers use to maintain cell integrity ?

A

FALSE-cells will be killed or damaged in high concentrations for too long of incubations periods.

Use enzyme-free dissociation buffers to maintain integrity

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43
Q

How do you dispense cells ?

A

Polystyrene flasks, polstyrene dishes, microwell plates, roller bottles, leighton tube

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44
Q

Cell cultures can be examined using…

A

Inverted tissue culture microscope

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45
Q

Cytopathic effect is…

A

Damage to cells during a virus invasion

Ex. Slide 34 of Cultivation of Viruses

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46
Q
A
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47
Q

What is the ideal way to isolate multiple viruses?

A

Co-cultivation: single monolayer consisting of multiple cell types, detects viral antigens using fluorescein-labeled monoclonal Ab.

Ex. Slide 41 of Cultivation of viruses

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48
Q

T/F- eggs are only good for food…

A

False! Can use to cultivate viruses

Materials: egg cander, specific pathogen free eggs, drill bits, betadine, sterile swabs

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49
Q

What does a blood ring indicate in an egg ?

A

Early embryonic death

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50
Q

What are the 4 routes of egg inoculation ?

A

Chorioallantoic, amniotic, allantoic, yolk sac

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51
Q

How do you do a yolk sac inoculation ?

A

22 gauge, 1.5 inch length needle…drill hole…place inoculum below embryo and in the yolk sac…seal hole with scotch tap or wax.

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52
Q

How do you do an allantoic cavity inoculation ?

A

26 gauge needle, drill hole above oer below air sac, inoculate allantoic cavity

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53
Q

How do you do an amniotic cavity inoculation ?

A

26 gauge needle, drill hole over the air sac, inoculate amniotic cavity

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54
Q

Chorioallantoic membrane inoculation (CAM) is done how?

A

Drill two holes in the eggshell: side and above the air sac

move air sac to side of the egg by gentle suction with rubber bulb, inoculate CAM

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55
Q

How do you know there is virus growth ?

A

Death of embryo, paralysis, stunted growth, urate deposits, hemorrhage and congestion, heamgglutins in embryonic fluids, extracellular membrane lesions

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56
Q

How do you inoculate mice ?

A

Intracerebral or intra peritoneal

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57
Q

T/F particles move at different rates depending on their mass

A

True

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58
Q

Isopycnic centrifugation: Buoyant density and isopycnic point. Tell me about them.

A

Buoyant: object has exact same density as fluid.

Isopycnic: buoyant density of particle equals that of surrounding density gradient medium.

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59
Q

Density Gradient Medium is…

A

Sucrose and Cesium Chloride

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60
Q

What will never happen during Isopycnic Centrifugation?

A

Particles will not sediment to bottom of tube

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61
Q

What is used to purify viruses and virus like particles ?

A

Chromatographic membranes

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62
Q

What are the two types of viral quantification tests ?

A

Biological: Depend on virus particle biological activity…. plaque, pock assays…various endpoint titration methods

Physical: Do NOT depend on virus particle…. electron microscope, hemagglutination, ELISA, PCR, flow cytometry

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63
Q

What is the most direct method to determine the concentration of viruses, but not routinely used due to

A

Transmission Electron Microscopy

64
Q

Virus Counter 2100 is…

A

A memory dump question, but…..

it’s a specialized version of flow cytometry developed for nanometer scale particles. Measures intact virions.

65
Q

How do you assess Antigen concetrations ?

A

Hemaglglutination assay

ELISA

High performance liquid chromatography (HPLC): UV analysis

Single Radial Immunodiffusion (SRID): agarose gel seeded with polyclonal antisera against a viral Ag

66
Q
A
67
Q

What is qPCR used for?

A

Quantifying viruses based on gene expression

68
Q

What is the most accurate quantitative biological assay used ? What is the minimum PFU needed to form plaques ?.

A

Plaque. 1000 PFU

69
Q

T/F-Plaque assays are used to obtain actual numbers of viruses

A

False. It is just a functional measurement

70
Q

What is the Principle of Plaque assay ?

A

Each represents cell lysis initiated by one viral particle

71
Q

What do plaques look like vs. viable cells ?

A

Plaques: clear circles

Viable Cells: blue

72
Q

Determination of Titer calulation:

A

GO DO THE PRACTICE PROBLEMS

Average plaque count x reciprocal of the dilution selected

PFU/ml

73
Q

What is the time for the eclipse period vs. latent period for the one-step virus growth curve ?

A

Eclipse: 0-12 hrs intracellular, none extracellular

Latent: 0-16 hours intracellular, extracellular

74
Q

Why do we even care about Pock assay ?

A

It’s on the exam!!!!

It measure the necrotic area on chorioallantoic membrane of embryonated egg-titraion of herpesvirus and poxvirus.

pock forming units/ml

75
Q

Transformation assay is….

A

Quantitative determination of titers of oncogenic viruses-lose contact inhibtion

focus forming units/ml

76
Q

Quantal Assay is…

A

the measurement of presence or absence of infection.

used for certain viruses that don’t form plaques/determining the virulence of a virus in animals or eggs

77
Q

What assay also measures the endpoints: ID50, LD50, Embryo LD50, Paralytic Dose50 ?

A

Quantal Assays

78
Q

TCID50 is ?

A

Tissue culture infectious dose that infects 50% of the cells

79
Q

Multiplicity of infection (MOI) is…

A

average number of virus particles infecting each cell

80
Q

What type of idiot cell allows for a virus to replicate ?

A

Permissive Cell

81
Q

What type of smart cell does not allow for a virus to replicate?

A

Non-permissive cell

82
Q

One-step virus growth curve Eclipse period is also called what ?

A

Viral uncoating and replication

83
Q

What is Burst size?

A

Number of virions released. Height curve= burst size.

84
Q

What is the order and descriptions of One-Step virus growth curve ?

A

Adsorption: virus attaches and enters cells

Eclipse period: time interval between uncoating and appearance, intracellularly, of first infectious progeny virions. No infectious virus can be detected during this time. 2-12 hrs.

Latent Period: time before new infectious virus appears in the medium. No extracellular virions detected.

Burst size: number of infectious virions released per average cell.

85
Q

What type of receptors do our cells possess for viruses to attach to?

A

Proteins, carbohydrates, glycoproteins, lipids, lipoproteins

86
Q

T/F-sometimes an additional cell surface moleucle/co-receptor is required for entry

A

True

87
Q

What evil virus that is rampent in St.Kitts uses more than one host cell receptor ?

A

HIV

88
Q

Enveloped viruses are mostly…

A

receptor-mediated endcytosed

89
Q

Clathrin-mediated endocytosis of virus by host…

A

1) Virion attach to host receptor
2) Adapter proteins bind to clathrin
3) Formation of Clathrin-Coated Pit (CCP)
4) Dynamim pinch off CCP that release Clathrin-Coated Vesicle (CCV)
5) Viral content delivered to endosomes
6) pH changes to acidic, viral genome released to host cell

90
Q

What happens to most non-enveloped viruses ?

A

LYSIS

91
Q

What occurs in local permeabilization ?

A

Allow virus capsid penetration into the cytoplasm

92
Q

What other types of receptor-mediated endocytosis are there ?

A

*JUST REMEMBER THE NAMES*

Caveolin-mediated endocytosis

Clathrin and caveolin independent endocytosis

93
Q

What do enveloped viruses only have ?

A

Membrane fusion/surface fusion

94
Q

What is retained on the cell surface that makes it a traget to the immune system ?

A

Viral glycoproteins

95
Q

What are the steps of antibody-dependent cell mediated cytotoxicity ?

A

1) antibody binds antigen on surface of target cell
2) Fc receptors on NK cells recognize bound Ab
3) Cross-linking of Fc receptors signals the NK cell to kill target
4) APOPTOSIS

96
Q

What viruses are pH independent ?

A

HIV and measles

97
Q

What are pH dependent viruses ?

A

HA in influenza viruses

98
Q

How else can non-enveloped viruses get their viral genome into a host cell ?

A

Pore-mediated penetration!

99
Q

How does FIP enter the host ?!

A

Antibody mediated attachment!

Attaches to the hosts’ macrophage via spike proteins to the CD13 receptor

Antibodies against spike proteins assist with entry into host cells through IgG-Fcgamma receptors.

100
Q

Let’s talk about the uncoating of viruses…

A

Some animal viruses begin to uncoat after binding to external receptor, completly uncoat in cell-Poliovirus

Some uncoating is complex series with host and viral gene products-Poxvirus

Retro/reoviruses occur inside capsid

101
Q

What is the process of pre-mRNA ?

A

Viral mRNAs are translated by cellular protein synthetic apparatus

Viral mRNA must conform to requirements of host cell translation system

Processing of primary RNA transcript/pre-RNA

mRNAs translated in cytoplasm

Viral mRNAs produced in nucleus exported to cytoplasm

102
Q

Where are viruses capped ? What is the purpose of capping ?

A

5’ end with 7-methelyguanosine

stability, binding of mRNA to ribosomes, mark mRNA as ‘self’

103
Q

How are caps synthesized ?

A

host cell enzymes (retroviruses, adenoviruses)

viral enzymes (poxvirus, reoviruses)

cap snatching! virus steals cap from host mRNA (influenza)

104
Q

What is added t 3’ end that is important for translation ?

A

PolyA tail and cleavage occurs at 10-25 nucleotides downstream

105
Q

What is spliced out during transcription ?

A

Introns bc it DOES NOT CODE FOR AMINO ACIDS

Exons do code for amino acids so they are saved!

106
Q
A
107
Q

Monocistronic vs polycistronic

A

Monocistronic: mRNa that encodes one polypeptide

Polycistronic: mRNA encodes several polypeptides

108
Q

What are 5 important viral proteins ?

A

Enzymes, structural proteins, viral nonstructural proteins, regulatory proteins, inhibitors

109
Q

How are naked and enveloped progeny virions released ?

A

Naked: lysis of host cell

Enveloped: budding

110
Q

What 4 viruses are released by exocytosis ?

A

Flavivirus, Arterivirus, Coronavirus, Bunyavirus

111
Q

What is a way viruses can spread cell-to-cell ?

A

Intercellular spread

Cell-cell plasma membrane fusion: herpesvirus, paramyxovirus, retrovirus

Tight junction: herpesvirus

Neural synapse: rabies virus

Actin or tubulin containin structures: poxviruses

Actin-containing structures, Filopodial bridges: retroviruses

Nanotube subversion: HIV-1

Virological synapse: retroviruses

112
Q

What variables does virulence depend on ?

A

Virus: strain, portal of entry, tropism to host organs, dose of infection, immuno evasion

Host: species, immunity, receptor, physiological factors, inhibitors, fever

113
Q

T/F- The higher the ID50 and LD50 the more virulent an organism is

A

FALSE-if it’s low it’s virulent

114
Q

What are 3 other ways of assessing degree of virulence ?

A

Severity of illness, incubation period, degree of severity, location, and distribution of gross, histologic, and/or ulstrstructural lesions in affected animals.

115
Q

What are the 5 sequential steps in viral infection…

A

1) entry of viruses, primary replication
2) spread, tropism, infection of target organs
3) virus-cll interactions, secondary replication
4) tissue and organ injury
5) shedding

116
Q
A
117
Q

Can viruses penetrate intact skin ? Why/Why not?

A

NO

Skin is awesome!!! –> dense outer layer keratin, low pH, presence of fatty acids, bacterial flora, dryness, components of innate and adaptive immunity.

118
Q

What defenses do our mucuos membranes have ?

A

IgA, virucidal proteins

119
Q

What are the defenses of the GIT ?

A

Mucous membrane or oral cavity and esophagus, acidity of stomach, alkalinity of intestine, layer of mucus covering the gut, lipolytic activity of bile, proteolytic activty of pancreatic enzymes, defensins, IgA, scavenging macrophages

120
Q

What are the defenses of the respiratory tract ?

A

Mucociliary blanket, alveolar macrophages, nasal associated lymphoid tissues (NALT), bronchus-associated lymphoid tissue (BALT), temperature gradient

121
Q

Do you care to tell me about the local spread on epithelial surfaces ?

A

Probably not, but you should….it’s not an FYI….

Virus replicates in epithelial cells at entry site, spread locally by infecting contiguous cells, produce localized infections…shed…or…spread to adjacent subepithelial tissues.

122
Q
A
123
Q

Let’s continue the talk about subepithelial invasion and lymphatic spread…

A

After local invasion…. the inflammatory response to virus infection, destruction of epithelium, or transport pathways like transcytosis allows for the subepithelial invasion.

This method should allow for viruses to overcome local host defense

124
Q

What is critical for subepithelial spread of viruses? Also, what is apical vs. basolateral release ?

A

Directional shedding

Apical: virus dispersal

Basolateral: allows access to underlying tissues for systemic spread

125
Q

What has targeted migration and replication of viruses within phagocytic leukocytes, pass straight through lymph nodes to enter blood stream ?

A

Subepithelial invasion and lymphatic spread

126
Q

Viremia and the three types are…

A

Virus in the blood.

Primary: initial entry of virus into blood after infection

Secondary: Virus replicates in major organs, and enters circulation again

Passive: direct innoculation of virus into blood.

127
Q

Active vs. Passive Viremia are…

A

Active: release of virions from initial site of replication to blood stream.

Passive: no initial replication elsewhere in host before

128
Q

What two ways are viruses found in the blood stream ?

A

Macrophages, Lymphocytes

Free in plasma (parvovirus)

129
Q

How are viruses eradicated from the blood stream ?

A

Mononuclear phagocytes in the spleen, liver, bone marrow, antibody clearance, complement-mediated clearance

130
Q

What examples of virus are spread through nerves ?

A

Herpes simplex virus: low neuroinvasiveness of CNS, highneurovirulence. Always enters PNS, rarely CNS.

Mumps virus: neuroinvasiveness, low neurovirulence. Most infections are CNS.

Rabies: high neuroinvasiveness and high neurovirulence. Infects the PNS and spreads to CNS with 100 % lethality.

131
Q

What are the 4 ways viruses spread in the nervous system ?

A

Axons, perinueral lymphatics, endoneural space, Schwann cells

132
Q

Retrograde vs anterograde spread…

A

Retrograde: virus travels opposite direction of nerve impulse flow

Anterograde: virus travels in direction of nerve impulse flow

133
Q

Centripetal vs Centrifugal movement…

A

Centripetal: toward CNS

Centrifugal: from CNS within peripheral nerves to other parts of body.

134
Q

Why are viruses so good at getting through the blood-brain barrier ?

A

1) Increase permeability of endothelial cells via TNF
2) Breakdown of endothelial cell junctions through Matrix-metalloproteinase (MMP)
3) Monocytes!

135
Q

Virus Shedding ! Yay… what is shedding ?

A

Infectious virions is crucial to maintenance of infection in populations

136
Q

What is critical to virus transmission ?

A

Virus shed

137
Q

Acute vs Persisten infection (shedding)

A

Acute: intensive over short period of time

Persistent: low shedding for months to years

138
Q

What are the routes of viral shedding from host ?

A

Oropharynx & GI, Respiratory, Mucous membranes, Oral & genital fluids, blood, urine, milk, skin

139
Q

Tropism is…

A

affinity of a virus for a particular host tissue

140
Q

What determines viral tropism ?

A

Receptors of host cell, attachment proteins, viral enhancers, cellular protease requirement, temperature of replication, acid lability and protease digestion, transcriptional control of tropism, anatomic barriers, host organ response to infection

141
Q

Types of virus injury to skin (6)…

A

1) Vesicle-small distinct elevation with fluid
2) Ulcer-opening in the skin caused by sloughing of necrotic tissue extending past the epidermis
3) Nodule, tumor-palpablel solid, elevated mass with distinct borders. tumors extend deep.
4) Warts- benign skin growths
5) Papules-solid elevations without fluid with sharp borders
6) Erythema- reddening of skin, from systemic viral infections

142
Q

Types of injury to GI tract…

A

1) Destructions of enterocytes from replication, hypersecretion
2) GI disease, malabsorpstion, diarrhea
3) Dehydration, acidosis, hemoconcentration

143
Q

Injury to respiratory tract (8)…

A

*There is tropism for different parts of the respiratory tracts*

1) loss of ciliary activity
2) loss of mucous layer lining
3) multifocal destruction of epithelium
4) inflammation
5) exudation
6) influx of inflammatory cells
7) obstruction of air passages
8) hypoxia & respiratory distress
9) secondary bacterial infections

144
Q

Types of injury to the CNS (6)…

A

Lytic infections cause..

1) encephalitis or encephalomyelitis
2) neuronal necrosis
3) neurophagia
4) perivascular cuffing (perivascular infiltrations of inflammatory cells)
5) Progressive demyelination
6) neuronal vacuolation

145
Q

Injury to endothelium (4)..

A

1) Petechial and ecchymotic hemorrhages
2) Disseminated intravascular coaglation [DIC]
3) Edema
4) Infaraction

146
Q

Describe DIC…

A

Something males have….ha….but really…

1) Complication from viral infection of blood vessels
2) widespread activation of clotting cascade = formation of blood clots in small vessels
3) excess clots can necros organs
4) once clots are degraded severe bleeding can occur

147
Q

What two ways can fetuses get infected ?

A

Amnionic via vagina

Placental via viremia

148
Q

What is teratogenesis ?

A

Abnormal development or slowing of development in embryo or fetus –> may result in death or malformations

Susceptibility to teratogens: varies with species, and decreases with age

149
Q

Cell injury to embryo..

A

1) cerebellar hypoplasia
2) arthrogryposis
3) porencephaly
4) congenital hydranencephaly

150
Q

Explain virus induced Immunopathology…

A

1) Required tissue injury mediated by host response to virus infection
2) Depends on balance between protective and destructive effects of host response
3) Infected cells not immediately destroyed and becomes chronic
4) Host can survive with minimal symptoms if virus cleared quickly (opposite happens when there is a large immune response)

151
Q

The role of Tcells…is this immuno? no!…it’s Viro…

A

T-cells can destroy virus infected cells or release cytokines

CD8+ destruction of infected cells can destroy liver

CD4+ and CD8+ can create chronic inflammation in persistent viral infections

CD4+ release more cytokines than Cd8+

152
Q

What are cytokines and examples ?

A

Small proteins for cell signaling. Mediate and regulate immune process, and cause inflammation.

Ex/ Monokines-mononucler phagocytic cells

Lymphokines-Th cells/lymphocytes

Interleukins-leukocytes (mediators)

153
Q

The role of Innate Immunity is…

A

TLRs-persistent viral infections allows for these cells to release PRO-inflammatory cytokines thus producing inflammation.

Free radicals, nitric oxide, and superoxide inhibit replication….but will cause cell damage if produced in XS

154
Q

Toxicity from antibody response..

A

Inflammatory reaction from antibody binding to cell that engages IgG and Fc to release mediators that leads to complement cascade

155
Q

What is vasculitis caused by ?

A

Antibodies failing to neutralize virus which triggers the complement cascade

156
Q

What type of infection suppresses the humoral and cell-mediated immune system ?

A

Systemic infection

157
Q
A

Virology (2 decks)

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