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Flashcards in deck_524014 Deck (130)
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2
Q

review of structure of paramyxoviruses- enveloped?- nucleocapsid symmetry?- genome structure?- -/+ stranded?

A

enveloped virionhelical symmetrygenome consists of a single molecule of RNARNA genome is minus-stranded

3
Q

what type of virus are mumps and measles?

A

paramyxoviruses

4
Q

are mumps and measles antigenically related to parainfluenza viruses?

A

mumps ismeasles is not

5
Q

describe mumps and measles:- nucleocapsid- genome- +/– envelope?

A

helical nucleocapsidminus-stranded RNAenvelope with virus-specified glycoproteins

6
Q

do mumps and measles hemagglutinate red cells?

A

yes

7
Q

do paramyxoviruses carry an RNA polymerase?

A

yes

8
Q

can measles and mumps viruses reassort? why or why not?

A

since the RNA is only one piece, genetic reassortment is impossibleas a result, no significant antigenic variation has been seen

9
Q

what types of infections do mumps and measles (and paramyxoviruses) cause?

A

systemic infections with viremia as an essential step in pathogenesis

10
Q

what is an essential step in the pathogenesis of mumps and measles

A

viremia

11
Q

what kinds of infections do orthomyxoviruses and paramyxoviruses generally cause?

A

local, nonsystemic noviremic infections

12
Q

what is the significance of the fact that mumps and measles cause systemic infection (summary)?

A

incubation period is longer for mumps and measles because cycles of multiplication in several sites in sucession are requiredlifelong immunity occurs in individuals who have had the disease - obligatory viremia allows neutralization by IgG

13
Q

how does the incubation period of mumps and measles compare with that of orthomyxoviruses and paramyxoviruses (so flu and paraflu)?

A

it’s longer because the cycles of multiplication is several sites in succession are required to establish infection in mumps and measles

14
Q

how long is immunity to mumps and measles after infection?

A

lifelong

15
Q

what antibody type is involved in the reaction to mumps and measles?

A

obligatory viremia allows for neutralization by IgG

16
Q

how many serotypes of mumps are there?

A

only one

17
Q

how many types of species can mumps infect?

A

humans are the sole reservoir of mumps

18
Q

how is mumps transmitted?

A

by respiratory droplets

19
Q

how long is the average incubation period of mumps before symptoms appear?

A

18 days

20
Q

what are the symptoms of mumps? what would allow you to diagnose mumps (ie what would you look for)?

A

around 18 days, a prodromal period of fever, malaise, and anorexia is followed by unilateral or bilateral swelling of the parotid gland (parotiditis) = usual presenting clinical symptomwill have inflamed parotid duct (stensens duct) in mouthalso get orchitis in males after age of puberty

21
Q

what is paratiditis

A

caused by mumpsinfection of the parotid glandthe virus grows in the enlarged parotid salivary glands becomes painfulis excreted in saliva several days before and after swelling of the gland begins

22
Q

why does mumps cause pain?

A

pressure and swelling within organs in tight capusles, so ones like the parotid gland and testis (orchitis) after puberty

23
Q

are most mumps infections symptomatic or asymptomatic?

A

most are symptomatic - only 30% are subclinical/asymptomatic

24
Q

where does mumps virus multiply, primarily?

A

in respiratory epithelium and local lymph nodes

25
Q

what is the result of primary mumps multiplicaton (ie what’s the secondary step in infection)?

A

in viremia that spreads to the salivary glands and other organs

26
Q

where do most of the infectious virions in mumps come from?

A

they are produced in the salivary glandsthey go down the duct to the mouth and are spread by coughs and sneezes

27
Q

how long does it take for parotiditis to begin in a mumps infection?

A

about 18-21 days = a three week incubation period

28
Q

how frequent is orchitis in mumps infections?

A

occurs in about 30% of infected males past puberty

29
Q

what is orchitis?does it resolve?who can get it?

A

painful inflammation of the testiclescaused by mumpsunilateral orchitis resolves with no other complicatoinsbilateral can result in sterility or subfertility but this outcome is uncommononly in adults after puberty because children don’t have fibrous capsule yet

30
Q

what organs are affected by mumps?

A

testicles, parotid glanduncommonly the pancrease and ovarymore commonly the meninges (aseptic meningitis)all have a generally benign course

31
Q

how long is the immunity to mumps after infection?

A

generally lifelong, even after subclinical infection

32
Q

is there an antiviral therapy for mumps?

A

no

33
Q

is there a vaccine for mumps? if there is, what kind of vaccine is it and how is it administered (timing)?

A

yes, there is a live-attenuated vaccineit’s administered as a component of the MMR pediatric vaccine given twice to confer protection without serious side effectsincidence of infection has fallen in developed countries because of childhood immunization

34
Q

what has been the incidence of infection in developed countries recently?

A

the incidence has fallen markedly because of childhood immunization but there have been some recent epidemics

35
Q

what kind of virus is measles? is it antigenically related to other viruses of its type?

A

measles is a paramyxovirusit is unrelated to any other paramyxoviruses in humans

36
Q

how often does measles cause subclinical infections?

A

almost never

37
Q

pre-vaccination, how often were there measles epidemics?

A

local epidemics occured generally every three years in the winter

38
Q

what were the causes of measles epidemics?

A

1: the number of nonimmune susceptibles increases because of births2: epidemics occur when the number of nonimmune susceptibles becomes sufficient to break down herd immunitynote: there is no antigenic variation between the strain that causes epidemic and other strains, unlike flu

39
Q

how is measles transmitted?

A

respiratory droplets

40
Q

how/where does measles infect?

A

via the respiratory tractinitially multiplies in the epithelium and local lymph nodes and conjunctiva

41
Q

what are the prodromal symptoms of measles?

A

fever, cold-like symptoms, runny nose, red eyesphotophobia is also a common symptom

42
Q

what is the definitive symptom of measles?

A

rashKoplik spots - bright red lesions with a white central spot on the buccal mucosa - appear first and then rash appears in a day or two the rash is described as a generalized maculopapular erythematous rash

43
Q

at what point after measles infection would you expect to see a rash appear?

A

after a 14-day incubation period

44
Q

what, besides the virus, plays a role in the development of the rash seen in measles?

A

the immun response

45
Q

how and when is measles virus excreted?

A

excreted from the respiratory tract and in tears and urinefor a few days before and after appearance of the rash

46
Q

how common are complications from measles infection in developed countries?

A

can be mild to severe (death)death rate in us from measles infection is 1 to 3 deaths per 1000 cases

47
Q

what are common complications of measles in developed countries?

A

1: 1 in 20 result in pneumonia (sometimes due to a secondary bacterial infection2: otitis media (generally bacterial)3: acute encephalitis in about 1 to 2 per 1000 cases

48
Q

in what cohort of patients would you expect to see complications from measles?

A

in adults and in those who are immune compromised

49
Q

how is measles treated?

A

there is no specific treatment, but could give antibodies to measles from the sera of immune individuals to help a bit

50
Q

what is the effect of the immune response to measles (ie is it effective and for how long)?

A

immune response eliminates viral excretionconfers life-long immunity without requiring restimulation by contact with exogenous virus

51
Q

what is the pathology of measles virus?

A

measles causes the formation of multinucleated giant cells in lymphoid tissue and respiratory mucosa (virus-induced cell fusion)

52
Q

what is the mechanism behind the pathology of the measles virus?

A

the measles fusion protein is inserted into infected cell plasma membranes, causing it to fuse with surrounding cells

53
Q

what is the effect of measles on cell-mediated immunity?

A

measles infection suppresses cell-mediated immunityeg: delayed hypersensitivity skin tests (such as the TB test) become negative for a few weeks or even months in a child who was positive before contracting measles = anergy

54
Q

what is anergy and in what viral infection does it occur?

A

transient loss of cell-mediated immunityoccurs in measles infections

55
Q

what type of environment (think population) does measles need to survive?

A

a large, concentrated human populationsince it’s nonenveloped, it’s unstable and so must be growing in some individual at all times

56
Q

how many resivoirs for the measles virus are there? how many serotypes?

A

only one - humansthere’s also only one serotype

57
Q

do immune individuals excrete infectious measles virus?

A

no

58
Q

what is the occurence of measles virus in small isolated populations like?

A

the virus disappears because continuous transmission is blocked by immunity or herd immunity

59
Q

what are the potential complications of measles virus and when do they occur?

A

though complications are rare, giant-cell pneumonia can occurthis is lethal, and occurs without a measles rashoccurs when cell-mediated immunity is defective (proof that cell-mediated immunity plays a role in the genesis of the rash)

60
Q

review of cell-mediated immunity

A

at least as important as antibodies in immunity to viral diseaseviral proteins are synthesized on cellular ribosomes in the cytoplasm adn these are occasionally partially degraded and antigenic fragments are displayed on MHCI proteins this antigen presentation triggers an attack by MCHI-restricted cytotoxic T cells that are specific for the viral antigen

61
Q

what is congenital agammaglobulinemia? what diseases are patients with this disorder usually susceptible to and which ones can they recover from?

A

a defect in the ability to make antibody but still have normal cell-mediated immunitysubject to recurrent bacterial infection but usually recover from viral infections and develop long-term immunity to these infections

62
Q

what is the mortality rate due to measles in developing countries?

A

5-25% mortality ratestill causes more than 160,000 childhood deaths each year (down from 600,000 10 years ago)progress in reducing deaths due to measles vaccination initiative

63
Q

what is symptom is seen in fatal cases of measles?

A

a severe hemorrhagic rash

64
Q

why does measles cause death?

A

likely results from fatal synergism of measles and malnutritionevidence for this: treatment with vitamin A can reduce mortality from measles (but also reduces overall childhood mortality rates)also formation of multinucelated giant cells (syncytia) - don’t need to know mechanism, but antibodies won’t inhibit and immune system will have to clear out all the damaged tissue - t-cell immunity must be used to do so

65
Q

how is measles treated?

A

there is no specific antiviral therapy available

66
Q

is there a vaccine for measles? if so, what type is it and how is it administered?

A

there is an injected live-attenuated vaccinegiven as a component of the MMR pediatric vaccinegiven twice

67
Q

how does herd immunity to measles compare to that of other viruses?

A

since measles is highly infective, establishing and sustaining herd immunity is more difficult

68
Q

how frequent are measles cases in the US today?

A

it has been eradicated in the US, but about 50 to 100 imported cases occur every year

69
Q

what are the challenges of measles eradication?

A

in developing countries, many cases occur before 12 months of age, making immunization extremely difficult because of maternal antibody

70
Q

what are general characteristics of slow viruses caused by conventional viruses? (summary card)

A

1: have a long incubation period (usually years)2: follow a slow but relentless course leading to death3: tend to have a genetic predisposition4: often re-emerge from latency during immune suppression

71
Q

how long is the incubation period of most slow viruses?

A

usually years

72
Q

how do genetics contribute to slow viruses?

A

those caused by conventional agents usually have a genetic predispositionthose caused by prions may have a genetic predisposition

73
Q

what are some examples of slow viruses caused by conventional viruses (list)?

A

HIVJC virus - causes PMLSSPE

74
Q

what family of viruses does JC virus belong to?

A

papovavirus

75
Q

what does JC virus cause?

A

progressive multifocal leukoencephalopathy (PML)

76
Q

what types of patients does PML occur in?

A

it’s present in 75% of normal human sera, but only becomes a problem in immunocompromised individualsespecially AIDS patients and those receiving cancer chemotherapy and immunosuppresive drugs following organ transplantationsome patients undergoing MS treatment with monoclonal antibody natalizumab

77
Q

what are effects of PML?- cell types affected- symptoms and final outcome

A

it’s a progressive demyelinating disease of the brain (JC infects oligodendroglia)causes demyelination by killing oligodendrocytesneurons are unaffectedno inflammation is seenprogresses to blindness, dementia, comapatients die within 6 monthsinitial symptoms include visual field defects, mental status changes, and weakness

78
Q

what is thought to cause PML in those infected with JC virus?

A

originates via the reactivation of JC viruscases have been reported in patients undergoing immune treatment for MS

79
Q

what are the effects/results of subacute sclerosing panencephalitis (SSPE)?

A

intellecutal deterioration, psychological disturbances with slow decline interrupted by remissionsstarts with mild changes in personality generally fatal with terminal paralysis and blindness

80
Q

what virus causes subacute sclerosing panencephalitis (SSPE)?

A

measlesdue to a recurrent infection that can’t repeat its replication (lev)

81
Q

what is seen by electron microscope in SSPE patients?

A

inclusion bodieshelical nucleocapsids were seen in these - suggested viral etiology

82
Q

what Ab titer and antigen results would you expect to see in a patient with SSPE?

A

high Ab titers to measles virus (much higher than in normal immune state)CNS contains measles virus antigen

83
Q

what is the relationship between measles and SSPE?

A

all patients with SSPE had an uncomplicated case of measles 4 to 17 years before developing SSPEmany had measles at age 2 or youngerall have high antibody titer to measles and measles antigen in their CNSthe virus can be isolated from SSPE brainshowever, how measles virus causes SSPE is not well understood

84
Q

can SSPE occur in individuals who have been vaccinated?

A

yes, but the incidence is less than one per million, which is much lower than the incidence following natural measles (one per 100000) (so basically you’re still better off getting vaccinated

85
Q

what are general characteristics of slow diseases caused by unconventional agents (prions)? (summary)

A

1: long incubation period (usually years)2: follow a slow but relentless course leading to death3: cause diseases confined to CNS4: produce a spongiform encephalopathy5: may have a genetic predisposition

86
Q

what are prions?

A

they’re hypothesized to be infectious proteinsprotein-containing particles that lack any detectable nucleic acidhighly resistant to proteolytic enzymesresistant to temperatures usually employed in cooking - may be important in suspected ability to be transmitted by food

87
Q

what are human prion-mediated diseases called?

A

transmissible spongiform encephalopahties(note: spongiform refers to spongy, swiss-cheese like hose seen in brain parenchyma that are caused by the death of the neurons - levinson)

88
Q

what are the five known human transmissible spongiform encephalopathies due to prions? (list)

A

1: KURU2: creutzfeld-jacob disease (CDJ)3: variant CDJ4: gerstmann-Straussler-scheinker syndrome (GSS)5: fatal familial insomnia

89
Q

scrapie (summary card)

A

chronic progressive CNS (usually cerebellum) disorder of adult sheepno pathological evidence of an infectious processcertain inbred lines are much more susceptibleagent that causes the disease has been transfered to mice with an incubation period of less than one yearresistant to uv irradiation, formaldehyde, alkylating agents, etc. - no known virus would survive these treatments

90
Q

in what species and part of the body does scrapie act?

A

in adult sheepchronic progressive CNS disorder - usually in the cerebellum

91
Q

what makes sheep genetically predisposed to scrapie?

A

being the descendent of certain inbred lines

92
Q

can scrapie infect other animals?

A

yes, it has been transfered to mice

93
Q

what is the incubation period of scrapie?

A

in the strains that have been transfered to mice, an incubation period of less than a year has been observed

94
Q

what treatments is scrapie resistant to?

A

UV irradiationformaldehydealkylating agentsno know virus would survive these

95
Q

what species and part of the body does Kuru affect?

A

it’s a progressive degenerative disorder of the CNS, especially the cerebellum, in humans

96
Q

in what population is the Kuru virus seen?

A

limited to a small stone-age tribe in New Guinea (the Fore people)

97
Q

what are the symptoms/effects of Kuru?- what cells it affects- symptoms

A

spongiform encephalopathy - death of neurons (rather than demylenation as with JC virus)at it’s peak caused 1/2 of the mortality rate of the fore tribe that it effectssymptoms = progressive tremors and ataxia, but not dementia

98
Q

how can the kuru disease be transmitted?

A

by ingestion of infected brainsthe symptoms and neuropathy were reproduced in chimps that were infected by intracerebral injection of brain material from human casescould also be transmitted through cuts while the brains were prepared

99
Q

what other prion does Kuru resemble?

A

scrapie, in terms of the properties of the infectious agent

100
Q

what is the incidence of Kuru today?

A

now low because of reduced cannibalism

101
Q

what is the most common human spongiform encephalopathy?

A

creutzfeld-jacob disease (CJD)

102
Q

what are the causes of creutzfeld-jacob disease (CJD)?

A

some are due to an inherited mutation (15% of cases; autosomal dominant; called fCJD), but most are spontaneous with no established cause (called sCJD)some iatrogenic (inadvertently caused by physicians) cases have been caused by corneal transplants and other medical procedures

103
Q

what are iatrogenic cases of a disease?

A

cases inadvertently caused by physiciansexample: cases of CJD due to corneal transplants from a donor with undiagnosed disease or contaminated surgical instruments or to GH prepared from the pituitary glands of undiagnosed patients

104
Q

what is variant CJD (aka vCJD), and how is it spread?

A

this is mad cow diseaseit’s a spongiform encephalopathy of cowsreached epidemic status in britain as a result of using brains and bone marrow from cows and sheep to manufacture of bovine foodoutbreak in humans was linked to eating beef from these infected cows

105
Q

what can inactivate prions?

A

protein and lipid-disrupting agents such as phenol, ether, NaOH, and hypochlorite

106
Q

what is the mechanism by which prions affect neuronal signaling (levinson)?

A

normally in alpha helical conformation (known as PRPc)when to changes to beta-pleated sheet (now known as PrPsc or prion protein scrapie) these aggregate into filaments - disrupt neuronal function and cause cell death beta-pleated form can recruit alpha helical forms and cause them to change their concentration

107
Q

are there virus particles in the brains of people with spongiform encephalopathies?

A

no

108
Q

what is an encephalopathy (levinson)?

A

pathologic process in the brain without signs of inflammation

109
Q

what is encephalitis (lev)?

A

an inflammatory brain process in which either neutrophils or lymphocytes are present

110
Q

how are prions acquired/transmitted? what do they do once they are (ie how do they spread throughout the body)? (lev)

A

ingestedmust survive digestion in intestinal tract and penetrate gut mucosaamplified within follicle dendritic cells in lymphatic tissue, such as peyer’s patchesspread to spleen - carried by migrating dendritic cellsspread to CNS, probably via sympathetic nervescould also reach the brain via lymphocytes

111
Q

what are polyomaviruses (enveloped?; genome structure?)? what is an example of one?

A

nonenveloped viruses with a circular, double-stranded DNA genomeJC virus is onethis is according to levinson - our course notes classify JC virus as a papovavirus

112
Q

how would you diagnose JC virus? (lev)

A

usually by PCR assay of a brain biopsy specimen or spinal fluid

113
Q

what are the clincal findings of CJD? (lev)

A

dementia, including behavioral changes, memory loss, and confusionmyoclonic jerkingataxiaaphasiavisual losshemiparesissymptoms appear gradually and progress inexorablyin terminal stage - patient mute and akinetic, then comatose80% die within 1 year

114
Q

how can CJD be diagnosed? (lev)

A

presumptively by detecting spongivform changes in brain biopsy specimenwould see neuronal loss and gliosis and sometimes amyloid plaquesbrain imaging and eeg may show changesspecific diagnosis by immunohistochemistry for prions (make antibodies in other animals because humans don’t make antibodies for the prions that infect them - so no serological tests can be used)

115
Q

how can vCJD be diagnosed? (lev)

A

presumptive diagnosis via brain biopsy specimenwould see “florid” plaques composed of flowerlike amyloid plaques surrounded by a halo of vacuolesbrain imaging and eeg may show changescan look at tonsilar tissue using monoclonal antibody-based assays

116
Q

what is familial fatal insomnia?

A

one of the slow diseases caused by prionscharacterized by progressive insomnia, dysautonomia, resulting in dementia, deathpatients have specific mutation in prion protein

117
Q

what is different about variant CJD than CJD? ie why is it variant? (lev)

A

occurs in much younger peoplehas certain clinical and pathologic findings different from those found in typical form of disease

118
Q

what genetic profile must someone have to contract vCJD?

A

can only be contacted by people who have a native prion protein that is homozygous for methionine at AA 129

119
Q

what are the symptoms of scrapie?

A

sheep get tremors, ataxia, itching - sheep scrape their wool off against fence postsspongiform degeneration without inflammation

120
Q

describe the replicative cycle of measles and mumps (lev)

A

adsorption to the cell surface via hemagglutininpenetrates and uncoatsvirion RNA polymerase transcribes the negative-strand genome into mRNAmultiple mRNAs are synthesizedeach translated into the specific viral proteinshelical nucleopcapsid is assembledmatrix protein mediates teh interaction with the envelopevirus released by budding from the cell membrane

121
Q

what is the result of measles infection in pregnant women? (lev)

A

usually results in stillbirth

122
Q

why shouldn’t the MMR vaccine be given before 15 months of age?

A

maternal antibodies could neutralize the virus, preventing an immune response

123
Q

what ways can genetic variation in viruses occur? (review) what forms of influenza can this occur in and why?

A
  • genetic reassortment - mixing between viruses of different speciesinfluenza A can undergo shifts in antigenicity but B and C don’t because B and C don’t exist in birds or pigs, where the reassortment is suspected to occur since birds and pigs can host human forms of influenza A- can have classical genetic recombination not with single-stranded RNA viruses- simple mutationRNA viruses have higher rate - paramyxoviruses
124
Q

what is the only thing that changes the death rate of humans?

A

influenza A (just a random interesting fact)

125
Q

why does the antibody for measles not appear until after 14 days? (what is the normal length of time for occurence?)

A

normally takes 7 days for antibodies to appear

126
Q

what are koplick spots?

A

spots in the mouthappear 14 days after infectiondefinitive of measles

127
Q

where can measles virus grow? what will the infection cause in some of these tissue types?

A

can grow everywhereso also grows in eyescauses photophobia - pupils hugeoften have tearsin respiratory tract so potential for pneumoniain skin so rashear infectionsencephalitis because can grow in NSfever

128
Q

what age group is measles infection most severe?

A

older children and adults

129
Q

what is anergy and in what virus does it occur?

A

anergy is lack of immune response to infected cellsin measles indicates that there’s a defect in T-cell response to the virus

130
Q

what is giant cell pneumonia and when does it occur?

A

only occurs in kids infected by measles with a genetic defect in cell-mediated immunityno measles rash!kills kids cause get syncytia in lung

131
Q

what can increase deadliness of measles (epidemiological factors)?

A

living in close proximity - in Glasgow rates of death increased significantly with the more people living/room - also socioeconomic thoughmalnourishedricketsvitamin Aproteingive any of these things get reduction in deaths