Respiratory Viruses Flashcards

1
Q

Orthomyxoviruses:

A

aka Influenza viruses

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2
Q

Orthomyxoviruses Structure

A

– enveloped, (-) ssRNA, 8 separate nucleocapsids, helical

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3
Q

Type A

A
  • Antigenic shift and drift
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4
Q

Type B

A
  • Antigenic drift only, school-age, less antigenic
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5
Q

Type C

A

– stable, unlikely to cause disease

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6
Q

Antigenic Drift

A

– accumualtion of point mutation of HA/NA that slightly changes the antigen, low in avian and high in human

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7
Q

Antigenic Shift

A

– sudden major antigen change due to reassortment of 2 strains, recycling or gradual adaptation

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8
Q

Glycoproteins

A

– NA, HA, M2 (Gp anchor), NS2, matrix protein, transcriptase complex

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9
Q

HA

A

-trimeric hemagglutinin, 5 antigenic sites HA0 made in RER → Golgi to make HA1 and HA2 with a fusion peptide

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10
Q

NA

A

– tetrameric neuraminidase, 2 antigenic sites, viral release

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11
Q

NP

A

– holds segmented RNA together

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12
Q

Influenza A:

Entry

A

– sialic acid receptor → HA → endocytosis → fusion with acidic endosomes → M2 protein forms ion channel → HA conformational change → fusion of viral and cell membranes → release of genome

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13
Q

Influenza A: Replication

A

– nucleus/cytoplasm, forms (+) strands to translate into proteins and replication of more (-) strands for progeny

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14
Q

Influenza A: Budding

A

– synthesized membrane GPs insert into cell membrane, packaged (-) strands bud out taking part of cell membrane

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15
Q

Influenza A: Pathogenesis

A

– aerosol inoculation → replication in resp tract → killing of ciliated and mucus cells → activation of T cells, interferons and Ab → influenza syndrome and future protection

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16
Q

Influenza syndrome

A

– acute and self-limited, fever, congestion, sore throat and cough (cytokines)

17
Q

Influenza syndrome Complications

A

– primary viral pneumonia, secondary bacterial pneumonia, combined, myositis and heart involvement, Reyes syndrome (aspirin use), Guillain-Barre syndrome (ascending paralysis)

18
Q

Influenza syndrome Pathogenicity

A

– string of basic residues at Arg cleavage site on HA0, cleavage by furin enzyme

19
Q

Influenza A Outbreaks:

H5N1

A

– high mortality rate, avian virus, no genetic reassortment
Receptor – sialic acid links via α2,3 instead of α2,6 → upper tract epithelia cells don’t bind, lower tract cells do bind
Cleavage site – highly basic residues, many tissues in the body will cleave, systemic spread

20
Q

H1N1

A

– swine origin, quadruple reassortment of human, swine and avian influenza

21
Q

Influenza Treatment:

Vaccines

A

H1N1, H3N2, Infl B - administered Oct/Nov before flue peak in Dec/Jan

22
Q

Influenza Treatment:
Vaccines
Inactivated

A

– Fluzone, Fluvirin, Fluarix

23
Q

Influenza Treatment:
Vaccines
Live-attenuated

A

– Flumist

24
Q

Influenza Treatment:

Amantadine/Rimantadine - prevent opening of M2 ion channel prophylactically

A
  • prevent opening of M2 ion channel prophylactically
25
Influenza Treatment: | Neuraminidase inhibitors
Neuraminidase inhibitors – Zanamivir, Oseltamivir – prevents viral shedding
26
Influenza Treatment: Immunity
– long lived but subtype specific, secretory IgA is primary mediator for URT, T cells help clear virus
27
Paramyxoviruses: | Structure
– enveloped, 1 (-) ssRNA, helical → cause giant cell syncytia Attachment proteins – F + HN (Paramyxo, mumps), H (measles), G (RSV)
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Paramyxoviruses: Replication
– fusion entry → (-) strand → (+) strand, only in cytoplasm
29
Measles:
infection of resp tract → lymphocytes and free virus in blood → conjunctiva, resp tract, GU tract, lymphatics, CNS, vessels Sx – 101+ fever, CCC, maculopapular rash due to T cell response to infected endothelial cells, Koplik spots (white, mouth) Complications – encephalitis, sclerosing panencephalitis, continued replication, malnutrition increases susceptibility
30
Mumps:
benign viral parotitis, T cell clearance | Sx – enlarged parotid gland (↑ amylase), could spread to pancreas, ovaries, testes, aseptic meningitis
31
RSV:
Respiratory Syncytial virus, high rate of hospitalization and infant death, most common cause of LRT disease in infants Sx – bronchilitis, brochopnuemonia, and croup (hoarseness, barking cough) in infants, bronchitis is adults Tx – ribavirin aerosol, -mabs directed to envelope GP of virus, oxygen therapy, no vaccine
32
Human Metapneumovirus –
– most everyone has Abs, clinically identical to RSV
33
Parainfluenza virus
– ss(-)RNA, enveloped, close relation to mumps | Sx – croup (steeple sign, stridor), bronchiolitis, pneumonia
34
Rubella:
Togaviridae, ss(+)RNA, icosahedral, enveloped | Sx – maculopapular rash (less red), prodrome (fever, rash, sore throat, lymphadenopathy, aka “3 day measles”
35
Congenital Rubella syndrome
– infection of fetus can lead to fetal death depending on gestational age Triad – cataracts, sensorineural deafness, heart defects (patent ductus, pulm stenosis), first trimester is the worst
36
MMR vaccine
– measles, mumps, rubella live-attenuated strains → 1 year, booster before school, before pregnancy Contraindications – egg or neomycin allergy, pregnancy, immunosuppressed, moderate/severe acute illness
37
Common cold: virus highly variable
Rhinovirus – picornavirus, naked, +ssRNA, acid-labile Coronavirus - +ssRNA, enveloped Transmission – hand contact, fomites, direct aerosol Patho – virus replicates in URT epithelia → cell death → cell sloughing, lamina propria fluid
38
SARS: severe acute respiratory syndrome
Coronaviridae -began in China, typical symptoms with a LRT infection and pneumonia