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2a - microbiology and IDs > viral infections > Flashcards

viral infections Flashcards

1
Q

what are the 6 stages in general virology replication

A
  1. attachment (between virus and host cell receptors)
  2. cell entry (viral ‘core’ carrying nucleic acid and proteins enter )
  3. interaction with host cells - virus uses cell materials eg. enzymes, for their replication and to subvert host cell defence mechanism
  4. replication within host cell to produce structural proteins, a viral genome and other nonstructural proteins eg. enzymes
  5. assembly of new virions
  6. release - bursts out of cells, or leaves via exocytosis, or leaks by budding. causes host cell death
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2
Q

which antibodies are involved in the humoral response to a virus ?

A

IgG,A,M response

IgA blocks attachment

complement factors are also involved

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3
Q

what cell can kill virus particles and infected cells and is a key part of the cell mediated response to viruses?

A

Cytotoxic T helper cells

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4
Q

what is meant by viral infection?

A

The process by which viruses evade the immune system and Interfere with specific or nonspecific defence

They do this by mutation

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5
Q

define antigenic drift

A

Antigenic drift of viruses:

spontaneous mutations, occur gradually giving minor changes in hemagglutinin and neuraminidase.

causing change in their antigens

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6
Q

define antigenic shift

A

Antigenic shift of viruses:

sudden emergence of new subtype different to that of preceding virus.

sudden change in coat antigens

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7
Q

out of antigenic drift and shift, which is responsible for epidemics and pandemics ?

A

Drift – epidemics

Shift – pandemics

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8
Q

give the definition/ criteria of a virus

A

An infectious, obligate intracellular parasite compromising genetic materia (DNA or RNA) surrounded by a protein coat and/or membrane.

They all have a receptor binding protein to ‘dock’ to cells.

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9
Q

what is the name of a virus that isn’t inside an infected cell

A

a virion

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10
Q

describe the structure of a virion, what does it consist of ?

A

the nucleocapsid
- Genetic material (DNA or RNA)
- Protein coat (capsid)

can be enveloped or non-enveloped
- envelope= lipid coat derived from plasma membrane of the host cell

contains no membranes or walls, no cell organelles, no metabolites,

very small

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11
Q

name 3 different shapes a nucelopcapsid can be

A

helical or icosahedral or complex

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12
Q

can a virus survive outside a host ?

A

depends in type of virus and environment

eg. can’t survive in UV light

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13
Q

a bacterium can contain both DNA and RNA . is this true also for viruses?

A

no

have only 1 type of nucleic acid

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14
Q

would you describe viruses as living?

A

they cannot feed or respire

they cannot reproduce by themselves

therefore considered non-living

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15
Q

give ways that viruses cause disease and damage

A
  • direct destruction of host cells
  • modify host ells
  • cause over-reactivity of host immune response
  • cell proliferation
  • evades intracellular and extracellular defences
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16
Q

give 2 ways that viruses evade the hosts extraceullar defence system

A
  1. latency - virus is non detectable but then can reactivate at a time of low immune control
  2. direct cell to cell spread - avoids immune system
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17
Q

give 2 ways that viruses evade the hosts intracellular defence system

A
  1. antigenic variability
  2. prevention of host cell apoptosis
  3. down regulation fo interferons and other defence proteins
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18
Q

what are the 2 main approaches to diagnosis of viral infection ?

A
  1. direct detection of the virus
  2. indirect detection of the immune response to the virus, using SEROLOGY
19
Q

list some methods of direct viral detection that are now considered outdated (timely,efffort)

A

electron microscopy

CPE - culture viruses for 4 weeks and look at effect virus has on the cells ie. detection of a cytopathic effect

20
Q

what is the preferred methods of direct viral detection

A

NAATs (nucleic acid amplification tests)

  • identify viruses by looking for the presence of viral nucleic acid in a tissue sample, blood sample or a swab.
  • most common NAAT is the PCR (polymerase chain reaction)
21
Q

describe how a PCR works

A
  1. special enzymes ‘unzip’ chains of DNA or RNA
  2. they then make complimentary copies of the original DNA/RNA by using nucleoside bases as substrate to double the number of copies of the original.
  3. By repeating this process many times, logarithmic increases in the copies of RNA/DNA are created.
  4. The nucleoside substrate bases are each specially tagged with a fluorescent molecule which only fluoresces when bound in a chain of other bases.

5.Thus, the creation of the new DNA/RNA can be detected and quantified by measuring increases in fluorescence.

22
Q

advantages to PCR

A

very sensitive and quick

23
Q

diadvantages to PCR

A
  • vulnerable to laboratory contamination of a sample and might give a false positive result
  • an only detect nucleic material complimentary to the primer sequences used to initiate it - so you need to know the DNA/RNA sequence of the virus before complimentary primers can be designed and used. It is not possible to detect a virus via PCR unless you suspect it in the first place and use the relevant primers.

Difficult for new viruses!

24
Q

indirect detection of a virus via serology

how does this work?

A

study the antibody responses in the serum with the virus in

25
Q

which classes of antibodies are especially examined during serology?

A

IgG

IgM

26
Q

IgM

  • when does it appear during a viral infection?
A

its the initial antibody to appear after an infection
(within one week of onset of infection)

remains positive for up to 12 weeks after an acute infection.

27
Q

IgG

  • when does it appear during a viral infection?
A

appears later than IgM

remains for life or many years and is responsible for giving immunity.

it binds to the antigens in a stronger manner than IgM

28
Q

what levels of IgG and IgM indicate and a re used to diagnose in serology recent viral infection

A

detection of virus specific IgM

or by measuring a rise in virus specific IgG antibody

29
Q

what is the most common serology technique

A

ELISA

enzyme linked immunosorbent assay

30
Q

its important to know herpes group 1-8.

what is HSV 1 commonly known as and what does it commonly cause?

A

herpes simplex virus type 1

often causes oral herpes

31
Q

its important to know herpes group 1-8.

what is HSV 2 commonly known as and what does it commonly cause?

A

herpes simplex virus type 2

often causes genital herpes

VZV (Zoster), EBV (Epstein Barr), CMV (cytomegalovirus),

32
Q

its important to know herpes group 1-8.

what is HSV 3 commonly known as and what does it commonly cause?

A

varicella- zoster virus

VZV

causes chickenpox and shingles

33
Q

its important to know herpes group 1-8.

what is HSV 4 commonly known as and what does it commonly cause?

A

Epstein - Barr virus , EBV

infectious mononucleosis, or mono

34
Q

its important to know herpes group 1-8.

what is HSV 5 commonly known as and what does it commonly cause?

A

human cytomegalovirus, HMCV

35
Q

its important to know herpes group 1-8.

what is HSV 8 commonly known as and what does it commonly cause?

A

Kaposi’s Sarcoma Virus

36
Q

examples of enteroviruses:

A

polio

rhinovirus

37
Q

need to know hep A-E

MAKE FLASHCARDS ON THESE

A
38
Q

name some respiratory viruses

A

Influenza A

Coronaviruses

Rhinovirus

39
Q

name Viruses associated with diarrhoeal outbreaks

A

Rotavirus, Norovirus

40
Q

name Lymphotropic viruses

A

HIV,

HTLV I & II (Human T-lymphotropic virus)

41
Q

name Viruses associated with immunocompromise & post transplant

A

JC virus, BK virus

42
Q

name a viral disease that causes an acute encephalitis

A

Rabies

43
Q

name a viral disease that causes an acute encephalitis

A

Rabies

2a - microbiology and IDs (13 decks)

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