Respiratory Viruses - Middleton Flashcards
Influenza Family, Genome & Virion….
Family = Orthomyxoviridae Genome = Segmented (-)ssRNA Virion = Enveloped
Adenovirus family, Genome & Virion…
Family = Adenoviridae Genome = dsDNA Virion = Non-enveloped
Rhinovirus Family, Genome & Virion…
Family = Picornavirus Genome = (+)ssRNA Virion = Non-enveloped
Which type of influenza is most common and most severe?
Type A
Which type of Influenza has an animal reservoir?
Type A (Birds)
How many segments does the Genome of Type A, B & C influenza have?
a=8
b=8
c=7
How is influenza virus identified?
By surface antigens HA and NA.
* 16 HA stereotypes & 9 NA stereotypes
What is the major determinant for Avian vs Human strains of Type A influenza?
HA *HA is also the major determinant for human to human transmission.
_____ is critical to budding with influenza?
NA
Describe the process of infection with influenza…
- Exposure to aerosolized droplets.
- attachment
- Conformational change by pH change in the endosome.
- Membrane fusion
Where does transcription take place with influenza?
In the nucleus
Incubation time, Symptoms & Recovery for influenza?
Incubation time = 1-4 days (Contagious 1 day before symptoms to 5 days later, Children longer)
Symptoms = Fever, malaise sore throat (Lasts 3-7 days)
Current strains of influenza?
H3N2 & H1N1
What are some complications of the influenza virus?
- viral Pneumonia
- Bacterial Pneumonia
- Reyes syndrome
- Otitis Media
Prevention of influenza?
Live attenuated vaccine
* Virus may change every year so need yearly vaccine.
Antiviral treatment
- Amantidine, Rimantidine
- Blocks entry, inhibits M2 activity
Zanamivir or oseltamivir (Tamiflu)
- Blocks release of button virions.
H5 & H7 Strains can mutate into ________ strains.
HPAI
What are the 2 highly pathogenic Avian influenza strains?
H5 & H7
_______ strains have multi-basic residues at HA cleavage site allowing replication throughout the body.
HPAI (Causes skin lesions, necrotic & Swollen combs in chickens.)
How are Adenoviruses characterized?
By their serotype
3 Key proteins for Adenovirus?
Fiber: cell attachment
Penton base: Cell entry
Hexon: capsid
How does Adenovirus enter cell?
Via coxsackie-adenovirus receptor (CAR)
- pH triggered capsid disassembly
- Moves to nucleus
What are the 3 gene expression phases of Adenovirus?
- Immediate-early: E1A portion of genome
- 2 transcriptional regulators (cell & Virus)
- Necessary to reach early stage - Early Phase: 5 genome sections (E1B E2, E3, E4 & L1)
- DNA replication & Post transcriptional events. - Late Phase: take over cellular mRNA synthesis
_______ gene produces proteins important to immune evasion. What does the protein do?
E3
- Blocks MHC
- Blocks TNF induced apoptosis
- Blocks IFN-alpha & beta keeping protein translation active.
Describe the Genome replication process of Aden virus…
- initiated on either end, identical end sequences
- Replication in 5–>3 direction, one strand displaced
- Displaced strand circularizes to allow template copy to be made.
- Primed by the protein pTP, usual priming strategy.
Adenovirus: When does DNA replication occur?
During S phase
Adenovirus: E1A inactivates ____ leading to ______ phase gene expression.
pRb
S phase
Adenovirus: E1B inactivates____ leading to ___phase and preventing apoptosis.
p53
S phase
Adenovirus: Disease &Symptoms
Respiratory infections very common
- Typically same symptoms as common cold, nasal congestion, inflammation cough….
Acute respiratory disease (ARD)
- severe pneumonia (seen in military recruits & crowded conditions)
- Vaccine available to military
Reservoir for Rhinovirus?
Humans only!
Vaccines for rhinovirus?
No! there are over 100 serotypes which makes vaccine impractical.
True or false. Rhino virus is a frequent cause of mud upper respiratory infections.
True!
Symptoms & Prevention of Rhinovirus…
symptoms = red nose, nasal discharge, epithelial damage Prevention = No vaccines, No antivirals
Describe the infection process of Rhinovirus; Attachment, Incubation, recovery….
- attaches to ICAM-1 or the VLDL receptor
- Incubation = 1-4 days
- Duration 2-3 days with detectable virus shedding
- Virus shedding can take up to 3 weeks.
