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Foundations of Medicine > Week 3 - Microbiology Viral Replication > Flashcards

Week 3 - Microbiology Viral Replication Flashcards

1
Q

What are viral pathogens classified by?

A

Basis of virion structure, characteristics of nucleic acid, and replication strategy

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2
Q

What are viruses?

A

Obligate Intracellular parasites… must have host cell - if they don’t multiply they will not cause disease

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3
Q

Do viruses produce toxins?

A

NO. They must multiply to cause disease.

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4
Q

Why vaccinate?

A

Provide as many antiviral compounds so when virus enters body they do not multiply

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5
Q

Virion

A

Invections virus particle, what invades the body

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6
Q

What does a virion contain?

A

Nucleic acid genetic material surrouned by protein coat (capsid)

Some have lipid and glycoprotein envelope

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7
Q

Genomes can be?

A

DNA or RNA

Single stranded or double stranded

Can have same (+) polarity or complimentary (-) polarity as viral m-RNA

Circular or linear (some segmented)

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8
Q

Positive polarity in viral genomes

A

Same polarity as viral mRNA (+)

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9
Q

Negative polarity in viral genomes

A

It is complementary to viral mRNA

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10
Q

Viral genomes are haploid except for what?

A

Retroviruses.. They are diploid

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11
Q

DNA vs RNA virus genomes

A

DNA are single stranded, double stranded, or circular

RNA is Single stranded (polarity), segmented or double stranded segmented

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12
Q

Capsids/Nucleocapsids

A

Nucleocapsid if enveloped

They are composed of many copies of one or very few viral-encoated protein subunits

Their function is in packaging the nucleic acid in viral assembly and protection of the nucleic acid

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13
Q

Capsid Shape

A

Either cylindrical (helical form) or cubic shape (icosahedron from)

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14
Q

Viral attachment protein (VAP)

A

Capsids of naked viruses contain VAPs. They are used this to get into other cells

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15
Q

VAPs as drug targets

A

If an antibody targets and destruct the VAP the virus cant get into cell and cant replicate

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16
Q

Capsomer arrangement

A 
Penton capsomer (surrounded by 5 capsomers)
Hexon capsomer (surrounded by 6 capsomers)
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17
Q

Do all capsids contain enzymes?

A

No. Only some.

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18
Q

Glycoproteins on Nucleocapsids

A

Specific glycoproteins act as VAPs for enveloped helical nucleocapsids

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19
Q

What is the Envelope composed of?

A

Lipds, proteins and glycoproteins

The glycoproteins are acquired from viral modified cellular membranes during egress of virus from host cell

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20
Q

What is the viral envelope disrupted by?

A

Non-moist environments, heat, acid, and lipids solvents…

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21
Q

What is a Peplomer

A

A glycoprotein

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22
Q

Enveloped helical

A

Capsomere surrounds nucleic acid in helix form

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23
Q

How are viruses classified?

A

Nucleic acid, virion structure, replication strategy

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24
Q

How many families of viruses in human pathogens?

A

21 families, 7 families contain DNA. Viruses in same family don’t always produce same diesease.. Also different families can produce same disease…

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25
Q

DNA viruses

A

…viridae

Parvo
Papo
Adeno
Herpes
Hepadna
Pox
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26
Q

RNA viruses

A

…viridae

Toga
Flavi
Picorna
Corona
Paramyxo
Reo
Bunya
Arena
Orthomyxo
Rhabdo
Retro
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27
Q

If viruses don’t multiply they…

A

…don’t cause disease!*

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28
Q

Obligate intracellular parasite

A

Use host machinery to produce mRNA so cant target host machinery as drug target… So must find a certain characteristic… to target

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29
Q

What does host range for viruses depend on?

A

If a virus can…

Enter a cell
Find appropriate cellular machinery
Exit the cell

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30
Q

Productive infections?

A

Virus infections that yield new infections viruses

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31
Q

Non-productive?

A

Virus infections occur when the vira genetic material persists in a cell (latent state) but no infections virus is formed

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32
Q

Some _________ infections can lead to oncogenic transformation of cells?

A

Non-productive

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33
Q

Phases of viral multiplication?

A 
Attachment
Penetration
Uncoating
Virus Component Synthesis
Assembly
Release
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34
Q

What happens to host cell during synthis of viral proteins?

A

They often result in morphological changes to the host cell. Called cytopathic effects (CPE)

35
Q

Cytopathic effets (CPE)

A

Morphological changes to a host cell that is infected with a virus

36
Q

What do antivirals do to a virus?

A

Inhibit one or more of the steps of viral multiplication

37
Q

CPE and herpes?

A

Some herpes can synthesize protein in their envelope to help fuse to host clel

38
Q

What to spikes find?

A

Specific receptor site on host cell..

39
Q

What is the general virus multiplication cycle?

A

Attachment to host cell
Penetration into host
The uncoating of the virus
Synthesis of viral proteins and DNA using host machinery (usually)
Assembly of the replicated virus from proteins
Release out of the cell
Repeat

40
Q

Difference in coated pit vs not coated..

A

Dff but ultimate affect is release of virion into host cell.

41
Q

RNA virus vs DNA virus synthesis

A

RNA virus does not need to get into nucleus.. Can translate in cytoplasm (where translation occurs in normal cells…already have RNA!)

DNA virus must get into nucleus to replicate.. Must transcribe RNA prior to translation

42
Q

Exceptions of where RNA virus and DNA virus replicate

A

AIDS - RNA virus - replicates in nucleus)

Influenza - RNA virus - (needs enzyme in nucleus of cell to replicate)

Pox viruses - DNA - cytoplasm

43
Q

Viroporins

A

Small, hydrophobic virus encoded proteins

Oligomerize at host cell membranes

44
Q

What are Viroporins involved in?

A

They are involved in enveloped virus budding

and Enveloped virus cellular lysis

45
Q

What cytopathogenic effects to viroporins have on cell?

A

They form hydrophilic pores and alterations of calcium and hydrogen gradients

46
Q

Draw maturation and budding of an enveloped virus.

A

viral multiplication ppt slide

47
Q

Where do naked viruses replicate?

A

In the cytoplasm of host cell

Then the cell lyses and releases the new virion

48
Q

Enveloped virion budding

A

Need host protein and viral protein spike. Then buds out.. Doesn’t necessarily kill cell but .. It modefies the cellular membrane and that results in the body not recognizing it as a normal human cell and the body kills it…**

49
Q

Virus life cycle

A 
Attach
Penetrate
Uncoating
Transcription of mRNA in cyto or nucleus Translation of proteins
Replication of DNA
Assembly proteins
Assembly of virus (maturation) 
Release
50
Q

How to determine how long it takes for a virus to replicate in a host cell?

A

Find a one step growth curve

51
Q

What is a one step growth curve?

A

Viral multiplication ppt

52
Q

Naked virus

A

Lyses cell, then to other cells

53
Q

Eclipase period

A

First start to see viruses made

54
Q

Latent period

A

First see release of virus

55
Q

Then get burst size

A

how many are pumped out.

56
Q

What happens to latent period in cells that are actively replicating vs cells that are not?

A

Latent period is much shorter in cells that are replicating. The host cell has all of the machinery up and running so to say*

57
Q

Example of Orthomyxocviruses

58
Q

Example of Retroviruses

59
Q

Where to RNA viruses replicate?

A

Replicate in cytoplasm except for orthomyxoviruses and retroviruses (transcription for these viral mRNAs happen in nucleus)

60
Q

What senses (+ or -) to RNA viruses have in regards to mRNA?

What is unique about negative sense viruses?

A 
Positive sense (same as mRNA polarity)
Negative sense (opposite of mRNA)
Ambisence (both positive and negative)

All negative sense RNA viruses are enveloped

61
Q

What do host cells lac (in cytoplasm) that RNA viruses must produce?

A

Host cells do not have cytoplasmic RNA polymerase

SO.. RNA viruses must produce their own replicase/transcriptase

62
Q

What is unique mechanism to produce individual polypeptices from polycistronic RNA?

A

Picornaviruses synthesize polypeptides that are then cleaved by viral proteases…

Individual initiaion adn termination signals appear throughout RNA of rabies virus

63
Q

Drugs target viral proteases…Why?

64
Q

Virus with segmented genome*

A

Each segment codes for one (or sometimes 2) polypeptides required for replication.

Orthomyxoviruses and retroviruses have segmented genomes. (retroviruses have spliced transcripts)

65
Q

Why is spontaneous mutation frequency higher in RNA viruses vs DNA viruses?

A

Because RNA polymerases are not as accurate in duplication

66
Q

What to all negative sense RNA viruses have?

A

Have a repicase/transcriptase associated with RNA within the virion

67
Q

What is different about RNA viruses HIV and Influenza?

A

NEED NUCLEUS FOR REPLICATION**

68
Q

What do all single stranded RNA replicate via?

except retroviruses, they replcate via?

A

Double stranded RNA intermediate

Retroviruses have a nuclear phase, involving reverse transcriptase

69
Q

Where does replication of DNA viruses occur? Why?

A

In the nucleus.

Because they need the machinery of the host cell.

Exception is poxviruses (happens in cytoplasm)

70
Q

Where do poxviruses replicate?

A

They replicate entirely in cytoplasm

71
Q

What phase of the host cell is needed for DNA virus replication?

A

S phase*

The availability of host cell DNA binding proteins for transcription helps determin tissue trophism and host range of virus

72
Q

Non productive infection

A

need S phase of host function* herpes on lip example.. Must have s phase of cell so factors activeate and allow virus to go town to lip and replicate…

If not in S phase the virus cannot replicate..

73
Q

All DNA viruses except which can transformm cells?

A

Parvoviruses

74
Q

Hepadnaviruses

A

Partially Double stranded DNA genome (Hep B)

75
Q

How are hepadnaviruses replicated?

A

Replicated in nucleus by RNA intermediate, RNA dependent DNA polymerase - reverse transcriptase.. (associated with HIV) sooooo.. Some Hep B treatments are results of HIV treatment research.

Hep B replication happens in hepatocytes*

76
Q

Pre-genome RNA

A

Full lenghth copy of DNA, then goes to cytoplasm . It is then reverse transcriptase enzyme makes the DNA.. So have core particle with viral dna that escapes.

77
Q

Reverse transcriptase

A

Make DNA from RNA copie using enzyme reverse transcriptase

78
Q

What DNA viruses have a double stranded DNA genome?

A

Adenoviruses
Herpesviruses
Papoviruses

79
Q

What do hepadna (DNA) and retroviruses (RNA) have in commone?

A

They require reverse transcriptase.. for replication

80
Q

What DNA viruses have a single strand DNA genome?

A

Parvovirues

81
Q

How is singel strand DNA replicated?

How is double strand DNA replicated?

A

Enters nucleus though nuclear pores
Forms hairpin structure (self primes DNA pol to synthesize complimentary strand

Double stranded DNA uses cellular DNA pol and viral specific endonucleases for form genome

Some strains need a helper virus to replicate (Adeno-associated virus)

82
Q

Double stranded DNA in Pox viruses

A

Provide own mRNA and DNA synthetic machinery

Code for viral DNA dependent RNA pols and mRNA modifying enzymes for capping and methylation

They synthesize own envelope

83
Q

Double stranded dna replication?

A

Provide own mRNA and DNA.. Do doe they need to be in nucleus?

Foundations of Medicine (42 decks)

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