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VP - Microbio > Wk 11/12 > Flashcards

Wk 11/12 Flashcards

(74 cards)

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1
Q

T/F: Viruses are definitely considered to be a part of the tree of life and a living thing, even though they don’t have a metabolism and standard cellular organelles of their own.

A

False, it is not a definitive thing, and they are non living entities (?!)

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2
Q

T/F: Loeffler and Frosch developed the first proof of viral infections in animals, while Dimitri Ivanosky used diseased tobacco plants to discover filterable infectious agents within them.

A

True

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3
Q

Discuss the general properties of viruses (relative/general size, facultative or obligate intracellular parasite, survival rate outside of host cells)

A

Small and filterable
Obligate intracellular parasites (hijack and utilize cellular metabolism to make energy or proteins)
Survive hours to days outside host cells - reduced infectivity with increased time outside host cells

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4
Q

T/F: many viruses have shown to be host specific but when selecting a host range, it is determined by virus requirements for attachments to host cell

A

True

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5
Q

Define giant viruses and provide two examples.

A

Viruses whose viral particle magnitude, structure, genome length, and complexity are larger than standard virus families
Ex. Mimivirus, medusavirus

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6
Q

In a general virus structure, what can a naked virus versus an enveloped one include?

A

Naked: nucleic acid, capsid, capsomer
Enveloped: All with envelope (w/ proteins, glycoproteins) and envelope spikes

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7
Q

Describe the difference between the viral genome and nucleocapsid.

A

Viral genome: viral RNA or DNA
Nucleocapsid: capsid + viral genome

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8
Q

What is the difference between capsid and capsomer?

A

Capsid: the protein shell that encases the viral genome that can exist in different symmetries with the function to protect, antigenic sites, and attachment to host cells
Capsomer: Basic subunit protein of the capsid

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9
Q

What is the structure and purpose of the envelope of a virus?

A

Structure: outer membrane of a lipid bilayer with embedded (glyco)proteins surrounding protein capsid
Purpose: facilitate virus entry to host cells, helps virus to adapt fast and evade host immune system

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10
Q

Define virion

A

Complete virus particle with RNA or DNA core with a protein coat, sometimes with an envelope and is the extracellular infective form of a virus

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11
Q

Define virus

A

Any aspect of the infectious agent including, infectious (virion) or inactivated virus particle, or viral nuclei acid and protein in the infected host cell

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12
Q

Define viroid

A

Infectious particle smaller than any of the known viruses, but AN AGENT OF CERTAIN PLANT DISEASES
Small circular RNA molecule, lacking the protein coat of a virus

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13
Q

What are four ways in classifying viruses?

A

Presence of envelope, capsid symmetry, nucleic acid, and genome architecture

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14
Q

T/F: enveloped viruses are the only type of viruses exist.

A

False, they can get naked as well ;)

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15
Q

What are the three types of capsid symmetry?

A

Helical, isohedral, and complex

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16
Q

Describe the helical capsid symmetry. Explain the difference between animal and plant viruses with helical nucleocapsids.

A

Description: capsomeres and nucleic acid are wound together and form a helical or spiral tube
Animal viruses are always enclosed within a lipoprotein envelope, while plant viruses commonly have naked helical nucleocapsids

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17
Q

How is the isohedral capsid symmetry formed?

A

(5) protomeres aggregate to form capsomers which are either hexons or pentons

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18
Q

Why can viruses be considered to have a complex capsid symmetry? Name two examples

A

Virions are composed of several parts each with separate symmetries and shapes.
Ex; bacteriophage (icosahedral head and helical tail) and pox virus

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19
Q

Explain the differences between DNA and RNA viruses

A

DNA: very stable, usu 2x helix, accurate replication, larger genomes
RNA: less stable, mixture of ss and ds, error prone replication

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20
Q

What is sense in terms of genome architecture? Differentiate between positive and negative sense.

A

Sense: polarity of the genome in relation to mRNA (5’ —> 3’)
Positive: genetic material has same polarity as viral mRNA (no need for transcription , direct translation into proteins)
Negative: genetic material is complementary to mRNA (transcription before translation)

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21
Q

Define Baltimore classification.

A

Clusters viruses into 7 groups depending on replication strategy of mRNA

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22
Q

What is a reservoir?

A

Habitat or population in which an infectious agent normally lives, grows and multiplies; can maintain pathogens over time; in animals, humans, environment

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23
Q

What are some misconceptions about reservoirs?

A

Not all sick animals are reservoirs, reservoir does not mean “not ill,” an individual can be killed by the agent, but the population maintains the agent

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24
Q

What are the 7ish examples of routes of transmission?

A

Abiotic environmental factors, animal vectors, direct contact, indirect contact, droplets, airborne, fecal/oral

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25
What is the difference between the airborne versus droplet route of transmission?
Airborne: can float in air for hours, can be inhaled, <5-100um Droplet: can travel less than 1m, cannot be inhaled, >100 um
26
What are four ways diseases can be transmitted?
Horizontal transmission, vertical transmission, zoonotic, cross-species transmission
27
Describe the viral genome (what do their genes code for?)
Contains only few genes, genes encode for structural components (capsid components), genes encode for enzymes necessary in the virus cycle, mainly for nucleic acid synthesis
28
T/F: viruses are facultative intracellular parasites, and can make energy and proteins by themselves. Their proteins and enzymes are synthesized and functional both inside and outside of the host cell, and do not need to be supplied by the host cell
False, they are obligate intracellular parasites. They need to be supplied by the host cell in order to make energy and proteins, making them only functional inside the host cell
29
List the viral replication cycle in order
1. Attachment, 2. Penetration, 3. Uncoating, 4. Replication, 5. Assembly, 6. Release
30
Describe the first step of the viral replication cycle: attachment/adsorption.
The process of attachment of the virion to the host cell surface Interactions between capsid (glycol)proteins or envelope spikes and host cell receptors determine host specificity and tissue specificity of viruses Receptors: selectively bind specific substance and mediate it’s entry or action into the cell Viruses have evolved to use host cell receptors where animal ones have attachment sites distributed all over the cell surface
31
Describe the second step of the viral replication cycle: penetration/entry (definition, dependent on)
The process of bringing the viral genome to the other side of the host cell’s plasma membrane by entry of (a portion of) the virion Dependent on energy and temperature
32
A host cell is classified as susceptible to virus if a virus can enter the cell. What are the three mechanisms a virus can enter?
Endocytosis, membrane fusion, direct penetration
33
Define endocytosis
Process in which the virus gains entry into the host cell without passing through the cell membrane via active transport
34
Define membrane fusion (definition, mediated with or without pH, type of viruses susceptible to this)
Process of merging fusion of the virus envelope with the host cell lipid bilayer membrane Mediated by pH independent fusion proteins or pH dependent fusion proteins that are anchored on the virus surface Only for enveloped viruses
35
Define penetration (definition, what mediates a pore’s location, restricted to which viruses)
Def: process of viral genome injection into the host cell’s cytoplasm after initial attachment Pore-mediated: relation of pore in host membrane mediated by viral pore-forming peptide associated in viral capsid Restricted to naked viruses AND viruses which genome is required for infection
36
Describe the third step of the viral replication cycle: uncoating
The process of capsid protein removal and release of viral genome in the host cell Disassembly of the capsid in a programmed multi step process mediated by cell pH and lysosomal enzymes
37
T/F: large viruses have their own uncoating enzymes, and there is a loss of infection for virions
True
38
Describe the fourth step of the viral replication cycle: replication/synthesis.
The genomic expression the viruses, using host cellular machinery to replicate and make functional and structural proteins
39
In addition to Baltimore classification, what key enzymes are important for replication/synthesis in viruses and why?
Reverse transcriptase: transcript + sense mRNA to ds DNA RNA dependent RNA polymerase: form + sense mRNA to - sense mRNA and vice versa DNA Polymerase: form DNA copies from DNA
40
mRNA synthesis is essential for viral protein synthesis. How does DNA viruses and RNA viruses differ in their mRNA synthesis and what are examples of exceptions for each?
DNA viruses: mRNA synthesis and replication in nucleus using host cell’s DNA-dependent RNA polymerase (exception: Pox virus - due to size) RNA viruses: mRNA synthesis and replication in cytoplasm (exception: retroviruses, influenza viruses)
41
In replication/synthesis, what is the difference in early and late protein synthesis?
Early: synthesis of enzyme polymerase which makes many copies of genetic material of progeny viruses Late: synthesis of capsid and/or envelop proteins
42
What are the differences in genomic expression between taxonomic groups of viruses?
Strandedness & Sense Location of production of mRNA
43
Describe the fifth step of the viral replication cycle: assembly and maturation. Where would it get packaged and which organelle holds that role?
Process of packing the viral genome and proteins into new virions following a specific order In nucleus, cytoplasm , and/or cell membrane Role of golgi
44
Describe the last step of the viral replication cycle: release/shedding. (List the 3 mechanisms and what type of virions does which mechanism)
The process of expulsion and release of progeny virions following replication in infected host cells Mechanisms: budding (enveloped virions), exocytosis, cell lysis (naked virions)
45
T/F: most bacteriophages require cell lysis to be released from the infected cell
True
46
What are the steps the life cycle of DNA viruses?
1) virions attaches to host cell 2) virion enters cells and its DNA is uncoated 3) a portion of viral DNA is transcribed, producing mRNA that encodes “early” viral proteins 4) viral DNA is replicated and some viral proteins are made 5) late translation; capsid proteins are synthesized 6) virions mature and are released
47
Why is Pox virus an exception to the life cycle of DNA viruses?
Large viruses, more gene,s, carry their own RNA polymerase, produced mRNA in the cytoplasm
48
What is the difference between plus sense versus minus sense single strand RNA virus in their life cycle?
Plus: fastest way to do translation/transcription, as you can immediately start translation Minus: first needs to be transcribed towards +sense mRNA
49
What are the exceptions to the life cycle of RNA viruses and why?
Influenza: viral DNA enters the nucleus Retroviruses: reverse transcriptase & viral DNA enters host’s nucleus and integrate as a provirus
50
In the third life cycle of bacteriophages, it can either be lytic or lysogenic. Define the lytic cycle.
phage infects the cell —> phage DNA circularizes remaining separate form the host DNA —> phage DNA replicates and phage proteins are made. New phage particles are assembled —> cell lyses, releasing phage
51
In the third life cycle of bacteriophages, it can either be lytic or lysogenic. Define the lysogenic cycle. What makes it different from the lytic cycle?
Phage infects a cell —> phage DNA becomes incorporated into the host genome —> cell divided and propagate is passed on to daughter cells —> under stressful conditions, the phage DNA excised from the bacterial chromosome and enters the lytic cycle
52
Compare prophages and proviruses
Prophage: virus genome of bacteriophage that is integrated into the DNA of a host cell; in life cycle of bacteriophages Provirus: virus genome that is integrated into the DNA of a host cell
53
When referring to the mechanism of cell injury, what are the results we can see viral infections have on host cells?
Inhibition (host cell nucleic acid synthesis, RNA transcription, protein synthesis), cytopathic effect, neoplasticism transformation, drive host cell to apoptosis, non-cytocidal changes
54
What are the three general effects viral infections can have on host cells?
Abnormal cell growth, cell damage/death (lysis, cell membrane alteration, apoptosis), no apparent changes (persistent, latent, immuno-suppression)
55
What are the two types of viruses with specific host range and effect?
Bacteriophages: viruses that infect bacteria and can kill bacteria; applied in phage therapy Oncolytic viruses: viruses that infect and kill cancer elks through oncolysis; applied in cancer therapy through stimulation of host anti-tumor immune response
56
In a viral growth curve, the timing of a one step growth cycle varies depending on virus and host. What is the difference in growth of bacterial viruses versus animal viruses.
Bacterial: 20-60min Animal: 8-40hr
57
Define the eclipse period of the viral growth curve. What stage(s) of the viral replication cycle does this happen
Infectivity of the virus disappears during uncoating and replication stage
58
Define the latent period of the viral growth curve. What stages of the viral replication cycle are seen here?
Replication of viral nucleic acid and protein. Uncoating, replication, reassembly/maturation (kinda)
59
Define the maturation period of the viral growth curve
Assembly of viral genome and protein into mature virus particles. If at this time cells are broken, active virus can be detected
60
Define viremia and the difference between passive and active viremia
Viremia: spread of viruses via bloodstream Passive: direct inoculation of virus into host’s bloodstream and no replication at site of entry (ex contaminated syringe, bite of arthropods) Active: viremia following virus replication in host
61
Compare primary and secondary viremia
Both are subcategories of active viremia Primary: spreading into the blood from infected area Secondary: spreading to other organs/tissues
62
What are the five patterns of infection in a host?
Acute, latent, chronic, persistent, persistent slow
63
Compare acute, latent and chronic infection
Acute: rapid onset of disease and symptoms Latent: virus remains in asymptomatic host cell for long periods Chronic: often with persistent shedders that have constant or intermitted shedding, can go unnoticed
64
Describe the difference between persistent infections versus persistent slow infections in a host
Persistent: after initial viral infection proliferation is ceased but viral genome not fully eradicated Persistent slow: characterized by a long incubation period followed by progressive disease
65
T/F: threshold level of virus is required to activate innate immune response
False; activate adaptive immunity
66
Why is diagnosis of viral infections necessary?
Viral disease diagnosis, screen of blood donors, proper management of diseases, early detection of epidemics
67
Although sampling depends on disease, virus type, host species, and diagnostic test, where can we sample from?
Blood, sputum/bronchial washes, feces, cerebrospinal fluid, biopsy/necropsy tissues
68
What are the four methods for lab diagnosis of a virus?
Virus culture and isolation, detection of virus specific antibodies, detection of viral antigen, detection of viral genome
69
T/F: viruses can grow on artificial media as they do not need host cells to replicate
False
70
List and define the three cell lines
Primary: derived from tissues, die after few generations Diploid: developed from human embryos, grow for 100 generations Continuous: transformed (cancerous) immortal cell lines (ex HeLa, Vero)
71
What are the purpose of embryonated chicken eggs
Cells that support virus growth; used for virus isolation, identification & production of vaccines Not all viruses will grow in tissues of ECE, but many can adapt to it
72
What is candling?
Method using bright light behind the egg to study growth and development of embryo inside
73
What is the difference between TCID50, LD50, ID50?
TCID50: tissue culture infectious dose; # of VIRUSES required to cause infection in 50% of cell culture LD50: 50% lethal dose; # of MICROBES or amount of TOXIN required to cause terminal acute infections in 50% of animals infected ID50: 50% infectious dose; number of MICROBES required to cause infection in 50% of animals
74
What are the 4 ways used for virus detection in diagnosis of viral infections
Electron microscopy, fluorescent antibody staining, immunohistochemistry, virus induced cytopathic effects

VP - Microbio (5 decks)

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