Lecture 87_88: Respiratory Viruses Flashcards
The Common Cold -
What is primary etiology?
what are some other causes?
Rhino virus
Other etiology: Coronavirus, adenovirus, enterovirus
Rhinovirus –
what is its common infection known as?
describe its Virology ?
seasonality; How is it transmitted?
The common cold (coryza)
Virology: PicoRNAvirus
Non enveloped; Icosohedral, Linear SS RNA
airborne transmission, fomites,
Rhinovirus - What are some unique features of its genome ? Describe its replication what receptor does it bind to? what initiates translation?
Describe its pathogenesis
what environment does it prefer?
Genome:
IRES – Internal Ribosome Entry Site (hairpin loop at end recognized by ribosome to initiate translation)
Capsid Proteins: VP1, 2, 3 – high variable; therefore cannot make vaccine
Replication: Binds to ICAM –> endosome –> fusion event –> RNA released to Cytoplasm –> IRES initiates translation –> process through ER and Golgi –> Mature Virions –> released via lysis
Pathogenesis:
Prefers nasal epithelium (34C)
Binding to ICAM induces bradykinin release — increased vascular permeability and inflammation
Limited cytolysis
Rhinovirus
- clinical manifestations
- Diagnosis
- therapy
- prevention
- NO FEVER
- Sneezing, rhinitis, runny nose, sore throat, HA, malaise
- can exacerbate asthma
dx – usually not done, but can do serologic testing
Therapy –
Hydration and humidified air
Zinc has been used but has adverse effects
Prevention – none
what are the two divisions of myxoviruses?
what are the differences?
what are some viruses in each class?
Orthomyxoviriae – Nuclear replication; segmented RNA
- examples: Influenza
Paramyxoviridae: Cytoplasmic replication; nonsegmented RNA
Examples: Parainfluenza virus, Morbilliviruse (measles)
The flu + Infleunza Like Illness
- what family of virus is influenza in?
- which serotype is the most common in human infections
- virology
- what are some features of the virion
- Influenza A
- orthomyxovirus – Enveloped, Segmented, negative sense RNA; Nuclear replication
8 RNA segments
Hemaglutinnin and Neuraminidase – immnuno dominant antigens
M2 – allows for acidification of the endosome
Carries its own Polymerase
describe the lifecycle of influenza virus?
Lifecycle: HA binds sialic acid receptor –> endosomal entry –> acidifcation via the M2 –> conformational change to HA –> fusion –> replication in the nucleus —> translation —> budding —> neuraminidase cleavage necessary for final budding off (cleaves HA from sialic acid)
why must a new influenza vaccine be manufactured every year?
describe some of the vaccines ? How do they work
Antigenic drift – mutation prone RNA Polyerase + Selection Pressures lead to changes of HA and NA which are the primary antigens of immunity = Epidemic
Antigenic shift – different combinations of the 8 segments of RNA leads to major changes rendering the entire population susceptible to the virus = Pandemic
Vaccines – Trivalent vaccine; heat killed combination of the three most prevalent strains. Focus on HA binding; NA
Inactivated Intramuscualar IM
high dose Inactivated Intramuscualr IM for elderly
Flumist – live attenuated
describe the pathogenesis of the influenza virus
what is the tropism?
Infects epithelial cells along the ENTIRE respiratory tract
Causes lysis and cell death; necrosis; local inflammation;
Influx of large numbers of Inflammatroy cells
Describe the clinical presentation of the flu;
Diagnosis of the flu
how is the flu treated
what used to me an effective treatment but now useless bc of resistance
Abrupt onset of systemic symptoms: high Fever, Retro-orbital HA; myalgia; malaise; URI symptoms; GI symptoms
Dx: Clinical
Rapid antigen tests; PCR and other Molecular Dx
Treatment:
-Neuraminidase Inhibitors: Oseltamivir, Zanmivir, Peramivir
Adamantanes – Resistnace; M2 inhibition prevneting acidication of the endosome
Acute Laryngotracheobronchitis – Croup
- what is the primary etiology?
- what family of virus is this in?
- describe the virology?
- what are some unique features of the genome?
- Parainfluenza Virus – 1, 2, 3 (PIV 1, 2, 3)
- Paramyxoviridae Family — replicates in the cytoplasm
- Enveloped, Non Segmented ss RNA;
- Hemaglutitin & Fusion Proteins, Own polymerase
- Immunomodulatory enzymes to block innate immune response (P, V, C)
Describe the lifecycle of the parainfluenza virus
HN binds Sialic acid receptor
Fuses with PM via Fusion protein at Neutral pH
Uncoating — RNA in cytoplasm
Translation / Replication
Viral Proteins processed through golgi, ER and trafficked to cell surface
Virions bud from the PM
Describe the pathogenesis of parainfluenza virus
PIV replicates in ciliated epithelial cells
Begins in Nasopharyngeal Mucosa – spreads to larynx, trachea and bronchi
Clinical presentation of parainflueza virus
- Diagnosis
- therapy
Prevention
Seal bark cough = croup — due to subglottal swelling
Stridor
Dx: clinical Presentation; PCR;
Xray: Steeple Sign
Supportive care – hydration, humidified air; monitor airway
No vaccine
Bronchiolitis:
- what is the primary etiology?
- what is the virology of this?
- Epidemiology – what is the seasonality
RSV (and Human Metapneumovirus)
Virology: Paramyxovirus family ; Enveloped; negative sense; ss RNA; replicates in the cytosol
Leading cause of childhood hospitalizations
followed by Croup
Winter seasonality
