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MMI 133 > lesson five > Flashcards

lesson five Flashcards

1
Q

viruses

A
  • infectious particles
    -must be treated using different therapeutic strategies than
    other microorganisms because they are different in
    makeup and structure
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2
Q

transmission of viruses

A

blood transfusion, mucus droplets, aerosols, fomites,
air (airborne), water, food, vectors

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3
Q

Virus Size

A
  • smaller than most bacteria
  • always obligate intracellular parasites
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4
Q

virion

A

complete infectious viral particle with nucleic acid surrounded by protein coat

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5
Q

viral structure

A
  • RNA or DNA and capsid (protein coat) comprised of capsomeres (protein molecules)
  • complete unit: nucleocapsid
  • some viruses have “lipid envelopes” outside of the
    nucleocapsid
  • glycoproteins or spikes inserted in enveloped or capsid
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6
Q

virus host range

A
  • different viruses can infect every life form
  • usually fairly specific host range or specificity
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7
Q

bacteriophages

A
  • viruses that infect bacterial cells and can transfer new genes from one bacteria to another
  • can transfer genes for production of toxin
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8
Q

classifying viruses

A
  • viruses are grouped into families on basis of DNA or RNA genome composition
  • RNA viruses are known for their ability to mutate quickly
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9
Q

DNA viruses

A
  1. Papillomaviridae (HPV)
  2. Adenoviridae (adenovirus)
  3. Hapadnaviridae (hepatits B virus)
  4. Herpesviridae (HSV-1, HSV-2, HHV-3…)
  5. Poxviridae (smallpox, monkeypox)
  6. Parvoviridae (B-19)
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10
Q

Viral infection: attachment and penetration into host cell

A

a) virus must attach to host cell, usually to receptors
b) two processes for penetration of the virus into the host cell: Fusion and Pinocytosis

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11
Q

viral infection: replication of the genome

A
  • DNA forms the genome of all organisms
  • Transcription of the DNA gives rise to a RNA molecule that is almost an
    exact copy of the DNA
  • protein is synthesized
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12
Q

what is the goal of a virus

A

to replicate itself

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13
Q

can viruses have two types of nucleic acid

A
  • viruses have only ONE type of nucleic acid (DNA or RNA)
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14
Q

DNA viruses replication

A

Host cell DNA polymerase may be used directly
to make more virus DNA (if replic. in host cell nucleus)
viral DNA → viral DNA

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15
Q

RNA viruses replication

A

Virus must carry its own RNA polymerase
enzyme to produce RNA from viral RNA (no RNA
polymerase in host cells)
viral RNA → viral RNA

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16
Q

retrovirus replication

A

carries its own reverse
transcriptase enzyme in the virus capsid:
viral RNA → viral DNA integrated into the
chromosome → viral RNA

17
Q

assembly of new virus

A
  • Association of newly replicated RNA or DNA (nucleic acid) with newly made
    viral proteins results in new nucleocapsids
18
Q

release of new enveloped virus

A

envelope components are produced and inserted into the host cell plasma membrane, the viral particle then attaches to the plasma membrane and buds through

19
Q

fuzeon (antiviral drug)

A

stops entry (fusion) of HIV into cells

20
Q

acyclovir (antiviral drug)

A

stops replication of herpes viruses by interfering
with the viral DNA polymerase

21
Q

tamiflu (antiviral drug)

A

stops budding/release of influenza
virus from host cell

22
Q

acute or productive infection

A
  • virus replicates, produces many virions
  • host cell often killed= lytic infection
23
Q

latent infection

A

viral genome persists in host cell but does not replicate- provirus

24
Q

chronic infection

A

virus replicates without causing host cell lysis and can persist for long periods of time

25
Q

what virus causes acute chickenpox infection

A

Caused by an enveloped DNA virus, HHV-3, sometimes called “varicella”

26
Q

chickenpox acute infection symptoms

A
  • fever, itchy rash
  • rash is spread on trunk and head
  • virus particles in rash can escape and infect
  • skin vesicles always present in different stages of lesion formation
  • When lesions heal, the virus travels up the nerve that
    ennervates the skin at the site of the lesion and makes a home in the peripheral nerve ganglion where it remains latent
27
Q

chickenpox latent infection

A
  • virus is present but no replicating until triggered by external factors, then travels down nerve to skin and reactivates
28
Q

what is reactivation known as in HHV-3

A

shingles or zoster

29
Q

shingles or zoster

A
  • reactivation of the virus as it travels back down the nerve to skin from the site of latency
  • begins as a local skin rash
  • characterized by confluent rash and pain
  • untreated rash lasts 2-5 weeks, infectious to those who have not had chicken pox
30
Q

chicken pox complications

A
  • most common in immunocompromised is secondary bacterial infection
  • CNS disease: encephalitis, meningitis, myelitis
31
Q

zoster complications

A
  • PHN (Post Herpetic Neuralgia) most common complication
  • 25-50% of patients >50 yrs develop PHN
  • Pain that persists for months or years
  • Can cause permanent nerve damage so important to get
    treatment (acyclovir) within 48-72 hours of symptoms
    appearing
32
Q

prevention of chickenpox

A

active immunization:
- live attenuated vaccine
passive immunization:
- effective up to 3 days post-exposure
- VZIG antibodies to the virus
- normally for immunocompromised exposed children and neonates born to mothers with varicella

33
Q

chickenpox

A

lesions are in different stages of development

34
Q

smallpox

A

all lesions are in the same stage of development

35
Q

oncogenic viruses

A
  • Some viruses can “transform” normal host cells to cancer cells
  • Not all “transformed” cells become cancerous e.g. wart virus:
    often benign tumours- Cancer-producing viruses can be RNA or DNA viruses
36
Q

PCR viral diagnosis

A

polymerase chain reaction
- molecular biology technique used to detect the genes in an organism

37
Q

prions

A
  • protein misfolding disease
  • self protein becomes changes and nonfunctional
  • prions are misfolded proteins that act as infectious agents in susceptible exposed animals
38
Q

human prion disease

A

always fatal

39
Q

human prion disease signs

A
  • ataxia
  • Cortical visual symptoms
  • Progressive dementia
  • Myoclonus
  • Akinetic mutism
    average death time after onset :4 months

MMI 133 (7 decks)

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