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MOD > morphology and biology of viruses > Flashcards

morphology and biology of viruses Flashcards

1
Q

criteria for virus classification

A
  • type and organisation of the virus (RNA/DNA? single/double stranded? genome relatedness?)
  • how does the virus replicate (e.g. reverse transcriptase?)
  • structure/size of replicate
  • range of hosts
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2
Q

characteristics of herpes herpidae

A

have an icosahedral nucleoplasmid. dsDNA that is linear. are enveloped and posses the ability to lay latent and then reactivate

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3
Q

characteristics of HIV

A

enveloped RNA virus. contains reverse transcriptase. two viral surface proteins = gp120 and gp41 involved in infecting Th cells

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4
Q

characteristics of Hepatitis A virus

A

naked RNA virus (not enveloped) icosehedral in shape. is +ve sense (= viral RNA can be directly translated, no need for transcription)

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5
Q

characteristics of hepatitis A virus infection

A

incubates for 15-45 days. is an acute onset. more common children and young adults. transmission mainly faeco-oral. can be sexual. unlikely percutaneous or perinatal

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6
Q

characteristics of hepatitis B virus

A

is enveloped DNA virus. Partially double stranded. icosahedral in shape. can exist as complete virus or incomplete particles of tubular filaments of virus surface antigen.
virus found in bodily fluids

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7
Q

characteristics of hepatitis B virus infection

A

incubates for 30-50 days. is acute or insidious onset. more common in young adults, babies, toddlers. percutaneous transmission, perinatal or sexual. rarely faeco-oral

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8
Q

characteristics of hepatitis C virus

A

enveloped RNA virus. NS1 and E proteins important

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9
Q

characteristics of hepatitis C virus infection

A

incubation for 15-120 days. insidious onset. common in adults. percutaneous transmission. mostly chronic cases. can cause cancer. responsive to IFN treatment

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10
Q

risk factors for contracting hepatitis C

A

IV drug users. Needle stick injury, Haemodialysis. Verticle transmission and Sexual transmission, blood transfusions before 1992

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11
Q

what are the 2 big GI infections

A

norovirus and rota virus

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12
Q

characteristics of norovirus

A

nonenveloped RNA virus.

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13
Q

characteristics of norovirus infection

A

once exposed, 2 days for symptoms to appear. symptoms include fever, vomiting, diarrhoea, abdominal pain. common in infants and young children but all can be infected.

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14
Q

treatments for norovirus

A

no antivirals available but oral vaccines are available

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15
Q

characteristics of rotavirus

A

dsDNA in a triple capsid. infects cells of intestinal epithelium using surface proteins VP7 and VP4. important in attachment and entry.

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16
Q

mechanism of rotavirus infection

A

binds and enters by endocytosis. loses outer layer. VP1,2,3, in virus transcribe dsDNA. mRNA enter cytoplasm and viral proteins made. then is assembly of the single and double shelled particles in the cytoplasm.
double shelled -> ER, acquires outer shell -> leaves cell to infect new cell

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17
Q

what is a +ve sense virus

A

viral RNA can be directly translated by host ribosomes, no need for transcription

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18
Q

what is -ve sense virus

A

viral RNA is the coding strand (for sense) and template strand .’. needs a reverse transcriptase

19
Q

characteristics of measles virus

A

enveloped -ve sense ssRNA. pleomorphic. highly contagious. transmitted via sneezing or coughing. virus can live on surface for up-to 2hrs

20
Q

characteristics of measles virus infection

A

after 2/3 days = white spots inside mouths., 3-5 days = rash on face and spreads down to feet. fever may spike.

21
Q

characteristics of mumps virus

A

enveloped ssRNA virus. transmission via droplets eg cough/sneeze

22
Q

characteristics of rubella

A

enveloped ssRNA virus from togavirus. transmission via droplets e.g. cough/sneeze

23
Q

what is rubella

A

acute viral disease with fever and a rash lasting 2-3 days, the disease is mild in children and young adults.

24
Q

what is congenital rubella

A

newborn has rubella bc pregnant mother contracted it. results in birth defects e.g. deafness, cataracts, heart defects, damage to fatal brain, liver and spleen

25
Q

what is adenovirus

A

nonenveloped dsDNA virus. commonly = respiratory illness; may cause other illnesses like gastroenteritis, conjunctivitis, cystitis and rash

26
Q

what is papillomavirus

A

non-enveloped dsDNA, some cause infection in genital tract, responsible for cervical cancer

27
Q

what is parvovirus

A

non enveloped dsDNA virus has receptor that allows it to attach to erythrocyte progenitors. parvovirus B19 = inhibition of erythropoiesis

28
Q

clinical presentation of parvovirus

A

erythema infectosum which has slapped cheek appearance on face. red rash on trunk and limbs. low grade fever, typically resolves in 7-10 days

29
Q

more serious problems that parvovirus can cause

A

gloves and shock syndrome, arthropathy, transient aplastic crisis, chronic red cell alpasia, neutropenia, pancytopenia, thrombocytopenia

30
Q

how is parvovirus transmitted

A

respiratory route via droplets. can be passed from mother to foetus.

31
Q

how do we diagnose parvovirus

A

serologically. IgM = recent virus. IgG = past infection.

also try to detect viral dna

32
Q

characteristics of influenza virus

A

airborne RNA virus. lipid envelope derived from host cell membrane. hem agglutinin and neuraminidase proteins on surface and ion channel (M2) embedded in viral envelope. has ribonucleic protein complex containing RNA and protein together.

33
Q

what is type A influenza

A

most serious and affects mammals and birds. cross over being type A strains may = pandemic. strains classified according to surface antigens

34
Q

what is type B influenza

A

Affects humans but causes only minor outbreaks not pandemics

35
Q

what is type C influenza

A

mild. affects only humans. is endemic, symptoms similar to common cold

36
Q

how does influenza A get into cells

A

attached to cells using (haemagluttinin) HA to attach to sialic acid on host cell membrane and is then internalised by endocytosis .’. is inside endosome in cell. virus envelope fuses with endosome membrane triggers uncoating of virus

37
Q

how does virus inside cell replicate itself

A

virus envelope fuses with endosome membrane =virus uncoated, viral nucleocapsid released into cytoplasm. -ve sense RNA is copied in nucleus to form +ve sense strand. copied back several times to -ve strand to be packaged into virus. mRNA synthesised from +ve sense to form viral proteins

38
Q

why down influenza A virus mutate rapidly

A

bc the RNA polymerase involved in replication of genome has a low selectivity and no proofreading mechanism .’. mistakes made often and not corrected

39
Q

what are the two patterns of mutation

A

antigenic shift and antigenic drift

40
Q

what is antigenic drift

A

continual viral mutation, often minor with no effect on function but changes accumulate over time and lead to new drifted strains that can produce illness

41
Q

what is antigenic shift

A

only occurs in type A influenza. genetic reassortment where there is mixing of genetic material between strains when they infect same host resulting in novel strain to which everyone lacks immunity

42
Q

symptoms of ebola virus

A

Fever, Headache, Diarrhoea, Vomiting, Stomach pain, Muscle pain, Unexplained bleeding or bruising

43
Q

characteristics of Ebola virus

A

enveloped RNA virus. spread by direct contact with blood or body fluids or contaminated objects e.g. needles

44
Q

how does ebola infect humans

A

enters through mucous membrane or through break in skin. infect many cell types. migrates from initial site of infection to lymph nodes, then liver spleen and adrenal gland.
tissue necrosis occurs, inflammation and finally organ failure

MOD (13 decks)

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