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Infection and the immune response > Viruses > Flashcards

Viruses Flashcards

1
Q

what is a virus?

A

simple acellular infectons pathogens, incapable of self replication or metabolic activity.

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2
Q

what is the average size of a human virus?

A

20 to 200nm can’t be seen under light microscope

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3
Q

what are the possibilities of viral genomes?

A

-DNA or RNA
-linear or cellular
-single stranded or double stranded (not for circular RNA)

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4
Q

what are some viral components?

A

-genome (nucleic acids)
-capsid (protein coat)
-nucleocapsid (complete unit of nucleic acid and capsid)
-naked or enveloped

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5
Q

capsid?

A

surrounds the genome ,composed of capsomeres, several different polypeptides grouped together. distinctive symmetry.

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6
Q

what is a virion?

A

fully assembled infectious ectracellular particle

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7
Q

what are the two types of capsid structures?

A

helical and isocahedral

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8
Q

what are enveloped viruses?

A

characterised by a phospholipid bilayer derived from the host cell ;
-plasma membrane
-golgi
-ER
-nuclear membrane

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9
Q

what are enveloped viruses composed of?

A

-lipids
-virus proteins and glycoproteins

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10
Q

what are glycoproteins?

A

they are expressed by viruses and help facilitate host cell entry. they are host cell receptor specific

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10
Q

where are glycoproteins expressed?

A

-alongside capsid proteins in naked viruses
-anchored in the phospholipid bilayer of enveloped viruses

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11
Q

what is viral tropism?

A

ability of a virus to productively infect a
-particular cell
-tussue
-host species

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12
Q

what are some modes of transmissions?

A

-droplet
-direct
-sexual
-transplacental
direct skin contact
oral

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13
Q

how can viruses be classified?

A

sie
genetic material
capsid structure and symetry
naked or enveloped

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13
Q

what are some diseases caused by viruses?

A

-respiratory illness (cold bronchitis, croup, viral pneumonia)
-coronaviruses
-influenzas
-herpes
-MMR
-HIV/AIDS
-ebola
-zica

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14
Q

what is a zoonoses?

A

infection passed from a non human host to a human host

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15
Q

what are the classifications of herpes?

A

-cold sores
-chicken pox
-shingles

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16
Q

what is a normal CD4 count?

A

450-1600

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17
Q

how do viruses enter a cell?

A

generally by endocytosis

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18
Q

what is macropinocytosis?

A

once the virus attaches to the host cell it can become engulfed by the host cell membrane

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19
Q

what is membrane fusion?

A

when the virus inserts itself into the host cell

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20
Q

what are the stages that are essential for virus replication?

A

-attatchemnt
-penetration
-uncoating
-replication
-assembly
-virion release

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21
Q

penetration?

A

-attatchment to specific receptor which can induce a conformational change in viral capsid proteins or the lipid envelope
-results in the fusion of viral and cellular membranes
-some DNA viruses can also enter by receptor mediated endocytosis

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22
Q

uncoating?

A

viral capsid is removed and degraded by viral enzymes or host enzymes releasing the viral genomic nucleic acid

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23
Q

replication?

A

-transcription or translation
-differs between DNA and RNA viruses with opposite polarities
-culminates in the de novo synthesis of viral proteins and genome

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24
Q

assembly?

A

-after de novo synthesis
-viral proteins packaged with newly replicated viral genome in new virions ready for release from host cell

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25
Q

virion release?

A

-lysis or budding
-lysis results in death of infected Jost cell (cytolytic viruses)
-budding results in the acquisition of the viral phospholipid envelope, don’t kill host cell (cytopathic)

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26
Q

persistent?

A

the virus may be maintained in the host cell cytoplasm eg herpes

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27
Q

what are the outcomes of viral infection?

A

-virus can be released and destroyed by cell lysis
-can exit by budding
-maintained in host cytoplasm
-become incorporated in genome
-can become oncogenic

28
Q

what are the 3 molecular mechanisms that can cause viral genome variation?

A

-mutation
-recombintion
-gene switching/reassortment

29
Q

what are some examples of mutations?

A

-insertion
-deletion
-substitution

30
Q

what affects the rate of mutation?

A

-RNA faster that DNA
-SS faster than DS
-smaller genomes faster than larger

31
Q

what is recombination?

A

exchange of entire genes between two strains, if two strains infect a host, recombination will occur confusing it resulting antigenic shift

32
Q

antigenic drift?

A

small mutations within antigenic genes over time which allows viruses to evade host immune systems

33
Q

what is antigenic shift?

A

an abrupt major change in virus

34
Q

what is the distinctive feature of coronaviruses?

A

spikes on their surfaces

35
Q

how many droplets does a cough produce?

A

3,000

36
Q

how many droplets does a sneeze produce?

A

40,000

37
Q

what are the types of influenza?

A

A, B and C
A+B cause significant human disease
B+C have limited genetic diversity and almost occur extensively in human
A is a zoonosis

38
Q

what causes chicken pox?

A

varicella zoster virus

38
Q

what causes cold sores?

A

herpes simplex virus

39
Q

what are the symptoms of measles?

A

-onset is flu like illness with high fever
-cough
-conjunctivitis
-red spots with bluish white centre in lining of cheeks inside
-widespread rash

40
Q

what is rubella?

A

important cause of preventable congenital defects
-infecton occurs in early pregnancy
-can result in miscarriage and still births
-highest risk of cogenital infection is during first 12 weeks

41
Q

when is HIV recognised as turning to AIDS?

A

when CD4 count drops below 200cells/mm3

41
Q

how does HIV infect an individual?

A

spreads through bodily fluids and attacks immune system and CD4+ cells

42
Q

what are the symptoms of Zika virus?

A

-fever
-rash
-headache
-joint pain
-conjunctivitis
-muscle pain

42
Q

what is congenital zika syndrome?

A

passed from mother to child during pregnancy
-microcephaly (small head) in the child
-reduces their brain size
-associated with guillian barre syndrom

43
Q

what are the possibilities of the nucleic acid genome of a virus?

A

RNA OR DNA
genome may be circular or linear
continuous or segmented
double stranded or single stranded

43
Q

what are some examples of enveloped viruses?

A

herpes
HIV

44
Q

example of a non enveloped/ naked virus?

A

polio

45
Q

what is positive sense viral RNA?

A

similar to mRNA and thus can be immediately translated by the host cell

46
Q

what is negative sense viral RNA?

A

complementary to mRNA and thus must be converted to positive sense RNA by an RNA polymerase before translation

47
Q

what is the function of a capsid?

A

provides protection for the viral genome against environment and functions in receptor recognition

48
Q

how do viruses enter the host cell?

A

generally by a form of endopinocytosis

48
Q

what is macropinocytosis?

A

once the virus attached to the host cell it can become engulfed by the host cell membrane

49
Q

what is membrane fusion?

A

where the virus inserts itself into the host cell

50
Q

what are the 6 basic stages of virus infection?

A

-attatchment
-penetration
-uncoating
-replication
-assembly
-virion release

51
Q

what is budding?

A

results in acquisition of the viral phospholipid envelope. these types of virus do not usually kill the infected cell and are termed cytopathic viruses

52
Q

what transcribes the first strand of the RNA double stranded virus?

A

viral polymerase into mRNA

53
Q

what does it mean to have a single strand positive sense?

A

the same base sequence as that is required for translation, it can be used directly as mRNA

54
Q

what does it mean to have a negative sense configuration ?

A

must be first transcribed using viral polymerase into a positive sense strand, which can then act as mRNA.

55
Q

how is a positive sense single strand RNA transcribed?

A

first made into a negative sense single strand DNA using viral reverse transcriptase carried in nucleocapsid
double stranded DNA then formed which enters the nucleus and becomes integrated in the host genome
integrated viral DNA is then transcribed by host polymerase into mRNA

56
Q

how does HIV invade immune cells?

A

infects T cells via high affinity interactions between the virion envelope glycoprotein (gp120) and the CD4 molecule. infection of the T cells is assisted by the T cell co receptor CXCR4 while HIV infects monocytes by interacting with the ccr5 co receptor

57
Q

what is the innate immune response to a viral infection?

A

recognition of PAMPS BY PRRs
pro inflammatory cytokines and interferons

58
Q

which herpes virus causes cold sores

A

herpes simplex

59
Q

Wha does positive sense mean?

A

Their genome RNA can be translated directly ask mRNA

60
Q

What are the three enzymes within the capsid of HIV that are essential for replication, function and survival?

A

Integrase, reverse transcriptase, protease

61
Q

which virus is commonly associated with antigenic shift?

A

influenza A

62
Q

which herpes virus causes chicken pox

A

varicella zoster virus

63
Q

where does the varicella zoster virus (chicken pox) remain after the skin infection heals?

A

nerve cells

64
Q

what is shingles a reinfection from?

A

chicken pox (varicella zoster virus)

Infection and the immune response (11 decks)

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