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MICR3320 > 21 - Viral Respiratory Diseases > Flashcards

21 - Viral Respiratory Diseases Flashcards

1
Q

Upper Respiratory Tract (URT)

A
  • Continually exposed to pathogens
  • Infections are common and usually mild
  • E.g. Rhinovirus, adenovirus
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2
Q

What does the URT consist of

A
  • Nasal cavity
  • Pharynx
  • Larynx
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3
Q

Lower Respiratory Tract (LRT)

A
  • Sterile environment
  • Infections are more dangerous and difficult to treat
  • E.g. Influenza, RSV, COVID
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4
Q

Chronic bronchitis

A

Develops as a significant and chronic inflammatory response to inhaled irritants (e.g. smoking) leading to narrowing of airways and scaring

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5
Q

Viruses damaging epithelial cells of RT

A
  • Viruses enter and replicate in epithelial cells
  • Infected cells lyse and cause oedema (enables secondary bacterial infection)
  • Severity ranges from sore throat to life threatening pneumonia and COPD
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6
Q

Fomites

A

Objects or materials which are likely to carry infection such as clothes, utensils and furniture

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7
Q

Rhinovirus

A
  • Group 4 (+)ssRNA
  • Enterovirus genus of Picornaviridae family
  • Transmitted by droplets and fomites
  • > 150 known serotypes
  • URT infection
  • LRT infection in babies and young children associated with severe disease
  • Can exacerbate asthma and bronchitis
  • Classified into 3 species (RV-A, RV-B, RV-C)
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8
Q

Rhino virus replication

A
  • Use three different receptors to enter respiratory epithelial cells
  • ICAM-1 is used by the majority of RV-A and RV-B viruses and is target for anti-viral therapeutics
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9
Q

Rhinovirus infection exacerbating disease in atopic individuals

A
  • Immune response in allergic individuals is biased to Th2: increased synthesis of cytokines that increase expression if ICAM-1 on the surface of bronchoepithelial cells (BECs), likely renders cells more susceptible to infection
  • BECs in atopic asthmatics produce decreased levels of anti-viral cytokine, increases severity of HRV infection
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10
Q

RSV

A
  • Group 5 (-)ssRNA
  • Orthopneumovirus genus, Pneumoviridae family
  • Ubiquitous pathogen that infects all children by 2 yo
  • Same symptoms as HMPV
  • May spread to LRT, host immune responses increase mucuus production leading to narrowing of airways and bronchiolitis in children
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11
Q

Maternal hypergammaglobulinaemia

A

In the presence of hypergammaglobulinaemia, high levels of non-specific antibodies are produced and saturate the finite number of Fc receptors at the placental interface

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12
Q

RSV G proteins

A
  • High glycosylation and structural variability of surface G-protein allows escape from neutralizing antibodies
  • Soluble G-protein, released during viral replication, binds anti-RSV antibodies and reduces amount available for RSV neutralization
  • Soluble G-protein also inhibits induction of TLR-mediated Type I IFN production
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13
Q

Human Metapneumovirus (HMPV)

A
  • Group 5 (-)ssRNA
  • Cough, fever, nasal congestion, may progress to bronchitis or pneumonia and exacerbates COPD
  • Viral clearance linked to development of adaptive immunity
  • Causes upper and lower RT infections
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14
Q

HMPV and host immune response

A
  • Inhibition of T cell priming is partially dependent on the secretion of soluble factors by HMPV infected DCs
  • Downstream effect on activation of B cells
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15
Q

Soluble factors secreted by HMPV infected DCs

A

Impair the upregulation of the TCR driven activation marker CD69 and proliferation of stimulated T cells

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16
Q

Rubella virus

A
  • Group 4 (+ssRNA)
  • Rubivirus genus, Metaonaviridae family
  • MIld childhood illness, rash
  • More severe in adults (arthralgia)
  • Causes miscarriage or congenial rubella syndrome (blueberry muffin skin lesions and cataracts)
  • Causes systemic infection
17
Q

Genetic effect on differences in rubella induced

A

Single nucleotide polymorphisms in innate immune receptors (cytokines or chemokine receptors, TLRs) are associated with measurable differences in humoral and cellular immune responses after rubella vaccination

18
Q

MEasles

A
  • (-)ssRNA
  • Morbillivirus if Paramyxoviridae family
  • Airborne virus transmitted by droplets and aerosols (remain in the air for 2+ hours)
  • Transmissible from 4 days prior to onset of rash to 4 days after rash erupts
  • Prodromal phase involves sneezing and coughing, which enhances virus transmission
  • Acute respiratory infection that becomes systemic
  • Rare complications: otitis media; croup; bronchopneumonia; encephalitis; subacute sclerosing
    panencephalitis
19
Q

Measles ‘immune amnesia’

A
  • Infects memory B and T cells, and naive B cells
  • Elimination of MeV infected cells deletes memory of past infections
20
Q

Mumps

A
  • Paramyxoiviridae family
  • (-)ssRNA, enveloped
  • Respiratory transmission by inhalation of aerosols
  • Preferentially infects activated T cells
  • hallmark is swelling of parotid gland
21
Q

Mumps infection

A
  • Infect cells of RT
  • Replicates in salivary glands, testes, RT, CNS
  • Can cause aseptic meningitis, encephalitis, deafness
22
Q

Parainfluenza

A
  • (-)ssRNA
  • Resipovirus genus, Paramyxoviridae family
  • Hemagglutinin ligates sialic acid receptor on respiratory mucosa-neuraminidase
  • Commonly cause URT infections
  • More serious disease: Croup, bronchitis, pneumonia
23
Q

Adenovirus

A
  • dsDNA
  • Adenoviridae family
  • Causes URT and LRT infections
  • Less frequently, infection is associated with hepatitis, meningoencephalitis
  • Transmitted by droplets, fecal matter, fomite and close contact (poorly sanitised swimming pools)
24
Q

Adenovirus infection

A
  • Infects mucoepithelial cells of respiratory and gastrointestinal tract, and cornea
  • High rates of mortality in patients with disseminated disease, who are immunocompromised (HIV, solid organ transplant)
  • Persists in lymphoid tissue
  • Type 1 IFN and IFN gamma suppressed by infection
25
Q

JC virus

A
  • Acquired by respiratory route
  • Disseminated infection that spreads to kidneys in early life
  • Persistent and latent infection is established in lungs, brain
  • In immunocompromised, virus is reactivated to replicate
  • Causes PML: progressive multifocal leukoencephalopathy
26
Q

Three groups that respiratory viruses cause more severe disease in

A
  • Young children
  • Elderly
  • Immunosuppressed

MICR3320 (25 decks)

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