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Biology 189 > L21: Viruses, Disease, Treatment, & Resistance > Flashcards

L21: Viruses, Disease, Treatment, & Resistance Flashcards

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1
Q

What are viruses?

A

a very simple microorganism that infects cells and may cause disease

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2
Q

Which types of biomolecules make up a virus?

A

Viruses are aggregates of nucleic
acid (4 to 2,000 genes) within a
protein capsid, and, sometimes,
viral enzymes and viral envelope
(host membrane + glycoproteins)

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3
Q

Do viruses have genes?

A

yes

Viruses are aggregates of nucleic
acid (4 to 2,000 genes) within a
protein capsid, and, sometimes,
viral enzymes and viral envelope
(host membrane + glycoproteins)

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4
Q

What is a capsid?

A

a protein coat

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5
Q

Do all viruses have capsids?

A

yes

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6
Q

What is a viral envelope?

A

outermost layer of many types of viruses typically derived from
(host membrane + glycoproteins)

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7
Q

Do all viruses have viral envelopes?

A

sometimes

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8
Q

Define the term pathogen.

A

cause disease

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9
Q

What is the difference between an epidemic and a pandemic?

A

AN EPIDEMIC is a disease that affects a large number of people within a community, population, or region.
A PANDEMIC is an epidemic that’s spread over multiple countries or continents.

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10
Q

How many humans (to order of magnitude) have died during major flu pandemics?

A

107 to 108 of humans

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11
Q

Which factors determine how infective a virus can be in a host?

A

Infectivity depends on: mode of transmission; host cell
membrane receptors; viral capsid, and viral envelope.

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12
Q

How big are viruses?

A

small 10^-7 meters

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13
Q

How does viral size compare to the size of prokaryotic and eukaryotic cells?

A

smaller

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14
Q

What are the modes of transmission viruses use to move from host to host?

A

A.General Transmission
- Abiotic environment factors (wind, entry into skin)
- Animal vectors (rats, mosquitoes)

B. Human to Human Transmission
- direct contact
- indirect contact
- droplets
- airborne
- fecal - oral

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15
Q

Of the viruses listed in your lecture slides, how are each transmitted?

A

direct contact
- ZIKA
-HIV
-HPV

indirect contact
- influenza
- norovirus

droplets
- Ebola

airborne
- influenza
- measles

fecal- oral
- norovirus

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16
Q

Why do some scientists argue that viruses are not alive?

A

Viruses lack many of the
properties of life; they:
• lack cellular
organization
• cannot metabolize
• cannot replicate
themselves; replicate
within host cell

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17
Q

In this view of viruses, where/how did viruses originate? (not alive)

A

Their view: viruses origin
from decomposing biota
or other processes

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18
Q

How does the new view of viruses differ from the traditional view of viruses?

A

Recently, some scientists
have argued viruses are
alive —just highly evolved
• In this view, the
missing properties of
life are not lacking;
they are outsourced to
host cells

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19
Q

In this new view of viruses, where/how did viruses originate? (alive)

A

They view viral origins as
a lineage of entities that
evolved from Earth’s first
protocells that parasitized
these cells

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20
Q

Which type of nucleic acid (polynucleotide) do viruses use to store their genome?

A

DNA, RNA (or both)

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21
Q

What is a bacteriophage?

A

virus that infects bacteria

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22
Q

Which type of cells do phages infect? Why might this be important to humans?

A

infect bacteria

Bacteriophages have complex relationships with our gut
bacteria and, thus, our immune system.

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23
Q

Discern between the lytic and lysogenic cycles of a typical bacteriophage.

A

Bacteriophage replication cycles may be lytic (host cell dies)
and/or lysogenic (host cell lives but now with a prophage).

24
Q

What is a prophage and how is it transmitted to daughter cells?

A

prophage (the genetic material of a bacteriophage) transmitted to daughter cells during binary fission.

25
Q

Which processes must a typical DNA virus undergo to complete its replication cycle? Do such viruses typically have their own enzymes?

A

Most viruses lack enzymes and
monomers for replication

•They use host cell enzymes
(e.g., polymerases) and
monomers (nucleotides,
amino acids)
• Host cell replicates viral DNA
• Host cell transcribes viral DNA
into mRNA and translates it
into viral capsid proteins
• Virons (i.e., viral particles)
self-assemble and exit

26
Q

Which processes must a typical RNA virus undergo to complete its replication cycle? Do such viruses typically have their own enzymes?

A

Most viruses lack enzymes and
monomers for replication

•They use host cell enzymes
(e.g., polymerases) and
monomers (nucleotides,
amino acids)
• Host cell copies viral RNA
• Host cell transcribes viral
RNA and translates it into
viral capsid proteins
• varies based on class
• Virons (i.e., viral particles)
self-assemble and exit

27
Q

Which processes must a retro RNA virus undergo to complete its replication cycle? Do such viruses typically have their own enzymes?

A

Possess reverse transcriptase (enzyme)

• reverse transcribes
ssRNA into dsDNA
• dsDNA inserted into host cell
genome as a provirus
• Host cell transcribes proviral
DNA and translates it into
viral capsid proteins
• Virons (i.e., viral particles)
self-assemble and exit with a
viral envelope

28
Q

What is reverse transcriptase and which process does it catalyze?

A

an enzyme retroRNA viruses possess that reverse transcribe ssRNA into dsDNA

29
Q

Which criteria are used to classify animal viruses?

A
  • Viral genome: dsDNA, ssDNA, dsRNA, or ssRNA?
  • If ssRNA: +, -, or retro?
  • Is there a viral envelope?
30
Q

What is the difference between a DNA virus and an RNA virus (don’t over think this one)?

A

DNA virus can replicate immediately whereas RNA virus must hav host cell transcribe first then replicate

31
Q

What is the difference between a double-stranded (ds) and a single-stranded (ss) virus (don’t over think this one either)?

A

one strand and two strand

32
Q

Discern among the following ssRNA viruses: positive-sense, negative-sense, and retro.

A

negative sense RNA virus comprises viral RNA, which is complementary to the viral mRNA

positive sense RNA virus comprises viral mRNA, which can be translated into proteins directly.

retro possess reverse transcriptase, reverse transcribes
ssRNA into dsDNA

33
Q

What are the six classes of viruses according to the basic (Baltimore) system of animal viral classification?

A
  1. dsDNA
  2. ssDNA
  3. dsRNA
  4. ssRNA (positive sense)
  5. ssRNA (negative sense)
  6. ssRNA (retro)
34
Q

You should be able to match the following viruses with their class and family: Papilloma (HPV), Herpes (HSV-1, -2, VZ), Parvo B-19, Rotavirus, Rhinovirus, ZIKA, West Nile (WNV), Influenza, Measles, HIV.

A
  1. dsDNA - papilloma (HPV), herpes (HSV-1, -2, VZ)
  2. ssDNA - Parvo B-19
  3. dsRNA - Rotavirus,
  4. ssRNA(+) - Rhinovirus, ZIKA, West Nile (WNV)
  5. ssRNA(-) - Influenza, Measles
  6. ssRNA(retro) - HIV
35
Q

Define the following abbreviations: HPV, HSV, and HIV.
Please learn the specifics (host cells, expression, transmission, treatments, etc.) we discussed regarding the following viruses: HPV, HSV, and HIV.

A

Class I. (dsDNA) Papillomaviridae:
Human Papilloma Virus (HPV)
• Host cell: epithelial cells (esp.
anogenital areas)
• Expression: warts on skin or
mouth, throat, respiratory tract,
and anogenital cancers (e.g., cervical)
• May be necessary but not
sufficient to cause such cancers
• Direct transmission: skin-to-skin
contact (esp. kissing/sex)
• Treatment: may clear on its own;
RNAi trials; HPV vaccine for
prevention in teens

Class I. (dsDNA) Herpesviridae:
Herpes Simplex Viruses (SV I, II)
• Typically, HSV-1 ➟ oral herpes and HSV-II ➟ genital herpes
• Expression: epithelial ulcers
• Retrogrades into nerves and goes dormant; triggers (e.g., UV, stress,
illness)➟ anterogrades/expresses
• Direct transmission: skin-to-skin
contact (esp. kissing/sex)
• Treatment: Docosanol (Abreva®):
a likely cell-binding inhibitor for
oral herpes; Valacyclovir (Valtrex®):
a DNA pol inhibitor for genital herpes and shingles; RNAi in
research trials

Class VI. (ssRNA) Retroviridae:
Human Immunodeficiency (HIV)
• Host cell: CD4+ T Cell (a WBC)
• Expression: ↓ immune function;
Acquired Immunodeficiency
Syndrome (AIDS)
• cannot defend against: Hep B/C, TB,
PC pneumonia, crypto-meningitis,
cancer, toxoplasmosis, etc.
• Direct Transmission: blood/body fluids
via sex, gestation/breast feeding,
sharing needles, etc.
• Treatment: ’Cocktails’ ↓ HIV and
protect against other pathogens

36
Q

What do the terms retrograde and anterograde refer to when discussing HSV?

A

Retrogrades into nerves (hides) and goes dormant; triggers (e.g., UV, stress, illness)➟ anterogrades(move back through the nerve into the epithelium where the ulcers will begin to be expressed)

37
Q

What does the following phrase mean: “HPV may be necessary but not sufficient to cause cervical cancer.”

A

you can be infected with HPV and not have other corroborating factors that cause you to develop cancer

38
Q

What are examples of triggers that cause anterograde and subsequent expression?

A

UV, stress, illness

39
Q

What are examples of infections that AIDS patients develop because they cannot defend themselves against the infection.

A

Hep B/C, TB,
PC pneumonia, crypto-meningitis,
cancer, toxoplasmosis, etc.

40
Q

Define AIDS.

A

acquired immunodeficiency syndrome (AIDS) interferes with the body’s ability to fight infections

41
Q

How do most antiviral drugs work?

A

disrupt the replication cycle of viruses

42
Q

What is a nucleotide analog and how does disrupt a viral replication cycle?

A

(mimic nucleotides) that are competitive inhibitors DNA polymerases (e.g., HSV) and terminate the nascent DNA chain

43
Q

How does RNAi potentially stop the replication cycle of a virus?

A

a small piece of RNA caps viral
mRNA stopping translation of capsid proteins

44
Q

What is antiviral drug resistance and how does it evolve (use the 3TC example to help you form your answer)?

A

mutants ‘survive’ causing population to adapt/evolve to drug making less effective (or even useless).

3TC is a cytosine analog nucleotide reverse transcriptase inhibitor (NRTI) that competitively inhibits HIV reverse transcriptase (RT)
halting the replication cycle.
However, some HIV variants with mutant reverse
transcriptase (MRT) are not inhibited by 3TC;
replication cycle continues…
HIV RT variants were selected against in favor HIV MRT; HIV has evolved resistance to 3TC.

45
Q

What are the three general forms of defenses humans use to defend themselves against pathogens?

A

A. Barrier Immunity
- mucus
- skin
- acidity

B. Innate immunity
- immediate response to breach of barrier allows immune cells to reach sit of injury

C. Adaptive immunity
- T cells kill pathogen-infected cells, tell B cells to make antibodies
- B cells make antibodies specific for the pathogen

46
Q

In which of these systems are antibodies formed?

A

adaptive immunity

47
Q

What is vaccination?

A

introducing pathogen antigens into a person for purposes of invoking immunization against future infections by that pathogen

48
Q

What is the goal of vaccinating a person against various pathogens?

A

create immunity by injection of antibody production that labels
pathogen for destruction now and memory cells to repeat in the future.

49
Q

What is an antibody?

A

a protein that binds to pathogens and make them easier to kill

50
Q

What is a memory cell?

A

antigen-experienced T cells that mediate a faster and more potent response upon repeat encounter with antigen

51
Q

For which viral pathogens have we developed vaccines?

A

MMR, HPV, Polio, Rotovirus, Varicella-Zoster, and Influenza, etc. (but not HIV, yet…)

52
Q

Is there an HIV vaccine yet?

A

not yet

53
Q

What is the antivax movement?

A

A movement to prevent person from vaccinating this children/themselves

54
Q

Is there a credible scientific link between the MMR vaccine and autism?

A

no

55
Q

What are ways the antivax proponents use social media memes to influence opinions about vaccination?

A
  • appeal to emotions
  • appeal to you vs. them
  • often compare situations that are not logically comparable
56
Q

Are such memes replacements for peer-reviewed scientific studies?

A

no

57
Q

Did you know that many health care workers are required to maintain up-to-date vaccinations as a condition of employment?

A

yes

Biology 189 (17 decks)

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