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3.34 Flashcards

1
Q

Paramyxoviruses (Family = Paramyxoviridae) Chapter 34

Species (4)

A

measles virus
mumps virus
respiratory syncytial virus (RSV)
parainfluenza viruses

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2
Q

Rhabdoviruses (Family = Rhabdoviridae) Chapter 35

Species: (1)

A

rabies virus

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3
Q

Orthomyxoviruses (Family = Orthomyxoviridae) Chapter 36

Species: (1)

A

influenza viruses A, B and C

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4
Q 
Paramyxoviruses
characteristics (4)
A

Helical nucleocapsid
Pleomorphic envelope (variable shape)
Hemagglutinin (measles virus) on envelope binds sialic acid on cell surface glycoproteins
measles virus binds CD46 protein present on most cells
minus stranded RNA genome

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5
Q

minus stranded RNA genome

=

A

one segment of RNA (~16,000 bases in length)

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6
Q

Paramyxovirus replication

A

Virus brings in RNA polymerase which transcribes minus RNA
into plus RNAs (full length and mRNAs)
Replication is cytoplasmic

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7
Q

Measles virus (~— nt –strand RNA genome)

A

16000

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8
Q

hemagglutinins -

A 
envelope glycoproteins
attachment proteins (bind virus to host cells)
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9
Q

F protein -

A

causes membranes to fuse together
role in viral entry into cells
expression on infected cells causes cell-cell fusion
Giant cells (syncytia)

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10
Q

All paramyxoviruses can induce — formation

A

syncytia

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11
Q

Measles (Rubeola)

characteristics (3)

A

• caused by measles virus
• enters body through
respiratory tract
• extremely contagious

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12
Q

Measles (Rubeola)
— involvement (partly, inflammation due to host response)
humoral and cellular immune responses modulate outcome

A

skin

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13
Q

Measles (Rubeola)

3 Cs=

A

cough, coryza,
conjunctivitis
Also morbilliform appearance
(rash = exanthem)

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14
Q

Coryza is a word describing the symptoms of a

A

head cold. It
describes the inflammation of the mucous membranes lining
the nasal cavity which usually gives rise to the symptoms of
nasal congestion and loss of smell, among other symptoms.

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15
Q

Measles (Rubeola)

complications (3)

A 
– Pneumonia (giant cell pneumonitis)
– Bacterial superinfections of middle ear
and lung
– pneumococci, staphylococci, and
meningococci
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16
Q

Measles (Rubeola)

• subacute sclerosing panencephalitis (1)

A

– rare progressive degeneration of central
nervous system caused by a type of
measles virus

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17
Q

Measles (Rubeola)

• treatment, prevention, and control (2)

A 
– symptomatic/supportive therapy
– attenuated measles vaccine
• MMR vaccine (measles, mumps,
rubella)
• Live Measles vaccine - 1993
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18
Q

Mumps

• caused by (3)

A 
mumps
virus
– Paramyxovirus
pleomorphic,
enveloped virus
– helical nucleocapsid
– negative strand RNA
(~15,000 nt)
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19
Q 
mumps 
clinical manifestations (3)
A

– develop 16-18 days after infection
– fever, and swelling and tenderness of salivary glands
– complications include meningitis and orchitis
(inflammation of testis)

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20
Q

mumps

tx

A

– live, attenuated vaccine (MMR)

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21
Q

Respiratory syncytial virus

characteristics (3)

A

minus stranded RNA
genome = one segment of RNA
enveloped

22
Q

Respiratory syncytial virus

G protein binds

A

host cells

instead of a hemagglutinin

23
Q

Respiratory syncytial virus

F protein -

A

causes membrane fusion

syncytia formation

24
Q

Respiratory syncytial virus

virus enter respiratory epithelial cells, then spreads

A

downward

along the respiratory mucosa

25
Respiratory syncytial virus | no clinically significant spread to distant sites (3)
necrosis of epithelial cells infiltration of lymphocytes increased mucous production
26
Respiratory syncytial virus (RSV) (2)
• considered to be most dangerous respiratory infections in young children • spread by hand contact and respiratory secretions
27
``` RSV clinical manifestations (3) ```
– acute onset of fever, cough, rhinitis, and nasal congestion – often progresses quickly to severe bronchiolitis and pneumonia host response may account for most serious
28
• bronchiolitis -
bronchiole obstruction that can | lead to respiratory failure
29
RSV | tx
– rapid immunologic tests
30
Rabies | • caused by --- virus (3)
rabies – negative strand RNA virus – highly neurotropic
31
Rabies | transmitted by: (3)
– bites of infected animals – aerosols in caves where bats roost – contamination of scratches, abrasions, open wounds, or mucous membranes with saliva of infected animals
32
``` Rabies virus (Lyssavirus) characteristics (3) ```
minus stranded RNA genome = one segment of RNA (~12,000 bases in length) enveloped, bullet shaped virus replication is entirely cytoplasmic
33
incubation can be up to -- months after virus enters body depends on size of: --- location of bite: --- bite has shorter incubation
12 inoculum face
34
Negri bodies
masses of nucleocapsids in cytoplasm seen in brain tissue of 70-90% of infected humans
35
``` rabies clinical manifestations (5) ```
clinical manifestations – begin 2 to 16 weeks after exposure – pain or paresthesia at wound site, anxiety, irritability, depression, fatigue, loss of appetite, fever, and sensitivity to light and sound – Hydrophobia – quickly progresses to paralysis – death results from destruction of regions of brain that regulate breathing
36
Hydrophobia:
contractions of muscles involved in | swallowing (sometimes sight of water elicits this)
37
rabies | tx (3)
– Passive administration of antibody (antiserum or immunoglobulin) (human rabies immune globulin = HRIG collected from immunized persons) – postexposure vaccination – preexposure vaccination of individuals with high risk of exposure, dogs, and cats
38
Orthomyxoviruses (Family = Orthomyxoviridae) Chapter 36 (3)
Genus: Influenzavirus - influenza virus A, B and C minus stranded RNA enveloped
39
Orthomyxoviruses | genome=
8 segments of RNA (for influenza viruses A and B) | 7 segments of RNA (for influenza virus C)
40
cap-snatching -
uses 5 end of host mRNA to prime viral mRNA synthesis | Random packaging of the 8 segments (11 segments packaged per virion)
41
``` Surface spikes (peplomers) hemagglutinin (HA) ```
attachment to host cell surface (prior to entry) binds to sialic acid on epithelial cell surface promotes membrane fusion (viral-cellular) binds/aggregates RBCs elicits protective neutralizing antibody response
42
neuraminidase (NA)
release of virus from envelope | cleaves sialic acid (NA has enzymatic activity)
43
Typical flu symptoms (fever, headache, muscle aches, malaise) due to ---
interferon induction
44
rabies tx (2)
–Treat with amantidine, rimantidine (A strain only); ribavirin (A and B) –inactivated virus vaccine
45
Antigenic shifts in influenza virus are caused by --- of viral genomic fragments during a mixed infection by two different influenza viruses
reassortment
46
Reassortment creates an
``` influenza virus that can infect humans but has a hemagglutinin from the animal influenza virus strain. (H3 vs. H2 in original human infleunza virus strain) ```
47
Changes in influenza virus surface proteins (hemagglutinin and neuraminidase) due to --- that occur during viral replication is called antigenic drift.
point mutations
48
Antigenic shifts in influenza virus are caused by reassortment of viral genomic fragments Pigs play an important role as a “mixing vessel”
for influenza viruses from humans, birds, and pigs. This is because pigs can become infected by these different influenza viruses. Example: Diagram of the origin of a new human virus with a shift from H3N2 to H5N1. Pigs were infected with a duck influenza virus, and another set of pigs with the human influenza virus. At some time, one pig underwent mixed infection with both viruses. The resulting virus created by reassortment of the viral gene segments could be transmitted to and infect humans. In this example, genomic segments from the duck virus contribute the genes for hemagglutinin and neuraminidase, shifting the original human virus from H3N2 to H5N1.
49
1918 flu pandemic: “spanish influenza” | characteristics (2)
killed 50 million world-wide | victims usually young and previously healthy
50
Likely killed via a “cytokine storm” in victims with strong immune systems
unchecked positive feedback loop between cytokines and cellular response result: too many immune system cells activated in an single space à tissue damage
51
H1N1 virus:
genome recovered in 1997 from victim in permafrost grave in Alaska Sequencing showed the virus originated in birds and mutated to be infectious in humans

Microbiology (42 decks)

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