Intro to Medical Virology Flashcards Preview

Microbiology Exam 1 > Intro to Medical Virology > Flashcards

Flashcards in Intro to Medical Virology Deck (30):
1

Can negative sense ssRNA undergo protein synthesis?

No, must be converted to positive sense first

2

DNA Viruses that infect humans

ssDNA: Parvoviridae

dsDNA: Papovaviridae, Adenoviridae, Herpesviridae, Poxviridae, Hepadnaviridae

Mnemonic: HHAPPPy

3

dsRNA virus family

Reoviridae

4

-ssRNA virus families

Paramyxoviridae, Rhabdoviridae, Bunyaviridae, Filoviridae, Orthomyxoviridae, Arenaviridae

Mnemonic: Paralyzed, Rabid Bunnies Fill Our Arenas

5

+ssRNA virus families

Retrovirus, Togavirus, Flavivirus, Coronavirus, Hepevirus, Calicivirus, Picornavirus

Mnemonic: I went to the Retro Toga party, where I drank Flavored Corona and ate Hippy California Pickles

6

How do cells replicate RNA viruses?

Cells CANNOT replicate RNA. RNA viruses must encode an RNA-dependent RNA polymerase

7

Three types of Viral Capsids

Helical (e.g. Tobacco Mosaic Virus), Icosahedral (e.g. Polio Virus), Complex (e.g. Smallpox (variola))

8

Naked Capsid Properties

Non-envoloped; Capsid is made of protein is very stable
-Stable to: temperature, acid, proteases, detergents, drying
-Released by cell lysis

9

Naked Capsid Clinical Consequences

Spread easily
Dry out and remain infectivity
Survive adverse conditions of the gut
Resistant to detergents and poor sewage treatment

10

Envelope Properties

Lipid envelope; not as stable as protein
-Envrionmentally labile and disrupted by: acid, detergents, drying, heat
-Released by budding and cell lysis

11

Envelope Clinical Consequences

***MUST STAY WET***
-Cannot survive GI tract
-Spreads in large droplets, secretions, organ transplants, and blood transfusions
-Does not need to kill the cell to spread

12

Virus Life Cycle Summary (6 steps)

1. Attachment
2. Entry
3. mRNA production
4. Protein and Genome synthesis
5. Virion Assembly
6. Egress

13

Attachment and Entry

Penetration: a direct fusion event

Entry: viral attachment proteins can be used to hijack vesicular transport system of cells --> invagination of plasma membrane --> pH change causes release of capside into cell
***Can occur in both enveloped and non-enveloped viruses

14

How do viruses get around the fact that cellular DNA replication machinery is not available at all times?

1. Make cellular DNA replication machinery available (e.g. PAPOVAVIRUSES stimulate cell growth and DNA synthesis)
2. Encode viral proteins to synthesize genome (e.g. POXVIRUSES encode their own polymerase and enzymes to provide deoxyribonucleotides for DNA synthesis, replication machinery, and transcription machinery in the cytoplasm)

15

(+)ssRNA viruses vs. (-)ssRNA virsues: dealing with the challenge of having no RdRp

(+)ssRNA viruses: encode a RdRp in your geneome

(-)ssRNA viruses: encode a RdRp in your genome AND carry the enzyme in your virion

16

What is the general pathway to viral assembly and egress?

1. Individual viral proteins form into capsid subunits
2. Subunits combine to form complete capsid
3. Viral genome and other essential virion components are selectively packaged into capsids
4. Envelope acquired (only for enveloped viruses)
5. Virus exits cell
6. Virions mature (only for certain viruses)

17

Budding

Allows viruses to assemble and get out of the cell at the same time

18

Egress: Lysis

***KILLS the cells as the virions leave

Lysis often accompanies release of virions with naked capsids

19

How do viruses evolve or change? (3 ways)

1. Recombination
2. Reassortment
3. Point mutations

20

Plaque Assay

-Place virus sample on a monolayer of cells, allowing for infection
-Lets you know infectious virus particle is there and allows you to count the number of viruses (each plaque is caused by one particle)

21

Which Viral Diagnostic test(s) target Antibodies?

ELISA
Western Blot

22

Which Viral Diagnostic test(s) target Genomes?

DNA: PCR
RNA: RT-PCR

23

Which Viral Diagnostic test(s) target Viral Antigens?

ELISA
Others

24

Which Viral Diagnostic test(s) target Infectious Virions?

Plaque Assay

25

Virus Culture/Plaque Assay (Detects, Advantages, Limitations)

D: Infectious Virus
A: Positivity shows viral infection
L: Restricted to viruses that replicate in tissue culture and produce cytopathic effect

26

Electron Microscopy (Detects, Advantages, Limitations)

D: Virion Particles
A: Especially helpful in the identification of emerging viruses
L: Relatively expensive and technically challenging

27

Antigen Detection (e.g. ELISA) (Detects, Advantages, Limitations)

D: Viral proteins and glycoproteins
A: Sensitive and quick
L: Requires specific antibody

28

PCR (Detects, Advantages, Limitations)

D: DNA genomes
A: Highly sensitive
L: DNA sequence information must be available

29

RT-PCR (Detects, Advantages, Limitations)

D: RNA genomes
A: Highly sensitive
L: RNA sequence information must be available

30

Serology (e.g. Western Blot) (Detects, Advantages, Limitations)

D: Anti-viral Antibodies
A: Sensitive and quick
L: Time must be allowed for the initiation of the immune response. Care must be taken to differentiate present from past infections.