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MICR 121 > Viruses > Flashcards

Viruses Flashcards

1
Q

Virus characteristics (4)

A

1) parasites, cannot replicate on their own, MUST have host

2) Made up of proteins and ONE type of Nucleic acid (either RNA or DNA)

3) main function of a virion (a single virus molecule) → deliver its DNA or RNA into the host cell so that it can be expressed (transcribed and translated) by the host cell

4) can infect animal cells, bacteria (bacteriophages), human cells

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2
Q

Examples of RNA viruses

A

COVID-19

HIV

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3
Q

Examples of DNA viruses

A

Hep B

Herpes (HSV-1, HSV-2)

“pox” viruses

varicella zoster (chicken pox, shingle)

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4
Q

Bacteria vs Viruses (4)

A

1) viruses are incredibly small, smaller than bacteria, need an electron microscope to see them

2) bacteria self-replicate, viruses do not

3) bacteria have cellular machinery including ribosomes, viruses do not

4) bacteria have DNA AND RNA, viruses only have one, not both

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5
Q

Methods to detect viruses (2)

A

1) antibody test

2) PCR

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6
Q

Viruses can be detected through antibody tests if they are
a) very common
b) rare or you get them once

A

b) rare or you get them once

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7
Q

Viruses that can be detected through antibody tests

A

HIV

Herpes

Ebola

West Nile

Canada and US: Dengue

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8
Q

Envelope of virus is made of ________

A

glycoproteins from host cell

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9
Q

Capsid

A

protein shell that protect the nucleic acid of the virus

important for the attachment of viruses to specific host receptors

provides structure and symmetry to the virus

consists of assembly of identical protein subunits

shapes - either:
1) Icosahedral
2) Helical
3) Spherical

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10
Q

Enveloped virus layers

A

Envelop

Capsid

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11
Q

Non-enveloped virus layers

A

Capsid

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12
Q

Which virus is most stable in the environment outside of host?
a) enveloped
b) non-enveloped

A

b) non-enveloped

can live on inanimate objects up to a week

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13
Q

Example of an enveloped virus

A

HIV

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14
Q

Examples of non-enveloped viruses

A

norovirus

poliovirus

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15
Q

Exception - example of enveloped virus that is stable in the environment

A

pox viruses

e.g. smallpox on blankets
e.g. m pox on hospital laundry affecting cleaning staff

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16
Q

Virus Classification System (5)

A

1) Nature of the nucleic acid in the Virion (RNA or DNA)

2) Symmetry of the capsid (helical, icosahedral)

3) Presence or absence of an envelope(enveloped or naked)

4) Structure, size and or Morphology of a virus

5) Tissue or organ tropism (Adenovirus, Enterovirus, Rhinovirus)

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17
Q

Virus Replication Cycle Steps (4)

A

QUIZ/MIDTERM Q**

1) Attachment
-to host cell

2) Entry and Uncoating
-remove capsid

3) Replication and Assembly
-replicates in cytoplasm or nucleus

4) Egress or Release of the Virus
-need to leave cell to infect other cells

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18
Q

Mechanisms of Virion Attachment (4)

A

1) Direct fusion

2) Endocytosis

3) Receptor-mediated entry

4) Nucleic acid translocation

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19
Q

Direct fusion

A

virus directly fuses with the host plasma membrane and the nucleic acid is released

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20
Q

Endocytosis

A

internalized into a vacuole, transported to an endosome and then the nucleic acid is released

may or may not be receptor mediated

21
Q

Receptor-mediated entry

A

specific receptors are used by the virus to gain entry into the cell

engagement of the receptors will often lead to changes in the structures of the virus that further help with entry

22
Q

Examples of viruses that use receptor-mediated entry (many)

A

HIV

Hep C

SARS

COVID

influenza

23
Q

Nucleic acid translocation

A

rare

feature of non-enveloped viruses

capsid adheres to host cell membrane

partial rearrangement of the virion

nucleic acid passed directly into host cell

24
Q

Types of viral lifecycles (2)

A

1) lytic

2) lysogenic

25
Lytic lifecycle
results in the host cell lysing in the end, releasing the virus so it can go on to infect other cells usually clinically quite apparent e.g. influenza
26
Lysogenic lifecycle
integrates its genetic material into the host cell's DNA and remains dormant e.g. HPV
27
Examples of a virus that is lytic AND lysogenic (2)
1) HSV-1 -lytic phase - cold sore -lysogenetic - clinically silent -lytic - another cold sore 2) Varicella Zoster -lytic - chickenpox -lysogenetic - clinically silent -lytic - shingles
28
Important enzyme that viruses carry
viral polymerase important for viral replication and transcription
29
Which type of virus mutates faster? a) RNA viruses b) DNA viruses
a) RNA viruses poorer antiviral response e.g. HIV, Hep C, COVID, SARS, influenza, RSV
30
dsDNA virus Replication
double-stranded viral DNA is transcribed to viral mRNA by the VIRAL polymerase mRNA is then translated to make proteins and enzymes that allow for new virus particle production uses the host RNA polymerase to make RNA (capsid proteins, DNA polymerase) newly created DNA polymerase can then replicate the virus DNA
31
Examples of dsDNA viruses (many)
Herpes viruses: -Herpes Simplex Virus 1 and 2 (HSV-1, HSV-2) -Cytomegalovirus (CMV) -Varicella zoster virus (VZV) -Epstein Barr virus (EBV) Hepatitis B virus Parvovirus B19
32
RNA Viral Replication
much simpler some can act directly as mRNA and be read on the ribosome some more complex i.e: must bring extra replicative enzymes with them
33
RNA virus examples (many)
Rotavirus Poliovirus West Nile Virus Influenza Virus Hepatitis A virus HIV Hepatitis C SARS-CoV-1 and SARS-CoV-2 (COVID-19)
34
Latent viral infection
implies lysogeny persistence of viral genomes, but not infectious visions, in host cells without the destruction of the infected cell for certain viruses, viral DNA can also become integrated within host cell DNA can lead to latent infection virus may start to replicate at later times
35
Examples of latent viral infections
HSV and varicella-zoster virus established latency in sensory neuron HIV-1 can avoid host immune responses and antiretroviral drugs through the latent infection of resting memory CD4(+) T cells
36
Examples of triggers for latent viral infections (5)
1) stress 2) UV light 3) hormones 4) immune suppression 5) unknown
37
Negative sense (-) RNA Viruses
has to be converted to a positive stranded genome prior to mRNA and protein production virion associated RNA polymerase results in a positive sense RNA that can them be transcribed to proteins
38
Example of - RNA viruses
influenza viruses
39
Postive sense (+) RNA Virus
RNA directly to mRNA and can be used to make proteins no intermediary steps
40
Example of + RNA viruses
SARS-CoV-2 and other coronaviruses
41
Retrovirus
RNA virus that use the reverse transcriptase enzyme to create a single strand of viral DNA complementary to the retroviral RNA ssDNA copied to form complementary DNA dsDNA now enters the host cell nucleus a later infection results
42
Methods of detecting viruses (5)
1) Electron microscopy 2) Serology 3) Virus culture 4) Amplification of nucleic acids 5) Antigen detection
43
Electron microscopy
direct detection best for: brand new viruses very large microscope difficult to do, time-consuming, impractical not as sensitive as PCR can only tell you what family of viruses the virus is from not the actual virus
44
Serology
detection of the immune response by the host against the infectious agent detecting specific immunoglobulin - Host antibody response best for: -very narrow window of viremia: West Nile Virus, Zika -not culturable: Hep B -at low levels soon after infection
45
Virus Culture
growth in tissue culture not all viruses can be cultured slow (days to weeks) requires specific cell lines and many different tissues types must be inoculated
46
Cytopathic effect (CPE)
effects the virus infection has on the appearance of cells in culture viewed by light microscopy after a patient specimen is inoculated onto the cell culture and the virus has had a chance to replication fairly non-specific
47
Amplification of Nucleic Acids
Polymerase Chain Reaction find a specific segment of RNA or DNA amplifies it exponentially
48
Antigen Detection
direct test on a patient specimen detecting specific antigens (antigen = antibody generator) of the particular organism you are looking for similar to a pregnancy test

MICR 121 (15 decks)

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