Respiratory Viruses Flashcards
Influenza Genome
segmented (-)ssRNA
Influenza Virion
Enveloped
Influenza Incubation
1-4 days
Influenza Strains
Three types: A, B, C
A is the most common
H3N2 and H1N1 are in circulation right now
Influenza Replication
In the nucleus, but the protected genome (RNP core) escapes the nucleus and buds from the cell surface
What are the major surface antigens of Influenza
HA and NA
What is the role of HA for influenza, and how many serotypes are there?
Cell attachment
16
What is the role of NA for Influenza, and how many serotypes are there?
Viral budding and release
9
What is the difference between Avian and Human strains of Influenza?
The linkage of HA is the major determinant
Avial = a2,3 linkage
Human - a2,6 linkage
Influenza Symptoms
Fever, malaise, nonproductive cough, sore throat
Symptoms have a 1-5 day onset (can be longer in children)
Symptoms last 3-7 days after they develop
Influenza Transmission
Aerosol, large and small droplets
Contagious a day before symptoms even occur
Influenza Prevention
Vaccine - live attenuated
- Antigens shift every year, that’s why we need one every year
- vaccine contains H3N2, H1N1, and Type B strains; Type A is generated through reassortment via coinfection
Influenza Treatment
Antiviral treatments -Amantidine, rimantidine -these block viral entry -resistance development is common Tamiflu -blocks release of budding virions
Avian Influenza
H5N1 H5 or H7 strain lethal in >75% of 6-8 week old chicks HPAI strains have multi-basic residues at HA cleavage sit allowing replication through the body H5 and H7 can mutate to HPAI strains
Low Pathogenic Avian Influenz
Asymptomatic to slight respiratory infection, no lesions
What was the controversy surrounding the Dutch research regarding Avian Influenza?
Tried to find out if H5N1 strain can adapt to humans (high mortality rate)
Passaged virus in ferrets (as human model)
After 10 generations, the virus was capable of airborne transmission between animals
Adenovirus Genome
dsDNA
Adenovirus virion
Non-enveloped
Adenovirus Strains
Characterized by their serotype
Different serotypes are associated with different diseases
Ad 2 & 5 are the most frequently studied
Adenovirus replication
In the nucleus
Initiated on either end from 5’ to 3’ end; one strand gets displaced
The displaced strand circularizes to allow template copy to be made
Primed by the protein pTP - unusual priming strategy
What are the 3 gene expression phases of Adenovirus?
Immediate-Early
Early
Late
Immediate-Early phase of Adenovirus gene expressoin
E1A portion of gene
2 transcriptional regulators - cell and virus
Necessary to reach the early stage
Early phase of Adenovirus gene expression
5 genome sections:
E1B, E2, E3, E4, L1
DNA replication and post-transcriptional evnts
Late phase of Adenovirus gene expression
Take over mRNA synthesis
What does the E1A protein of Adenovirus effect?
Inactivated pRb, leading to S phase gene expression
What does the E1B protein of Adenovirus effect?
Inactivates p53 - leading to S phase and preventing apoptosis
What does the E3 gene protein of Adenovirus effect?
Produces proteins important to host immune invasion
How does Adenovirus effect the host cell immune system?
Blocks MHC class I expression - reducing CTL cell killing
Blocks TNF induced apoptosis
Blocks INF-a and INF-B action - keeping protein translation alive
Adenovirus symptoms
Respiratory infections are very common
Similar to common cold
Acute respiratory disease (ARD) - severe pneumonia, seen in military recruits, crowded conditions
Adenovirus Prevention
Vaccine is available for milirary personnel 17-50 years old
What virus can be used for gene therapy?
Adenovirus
Rhinovirus Genome
(+)ssRNa
Rhinovirus Virion
Non-enveloped
Rhinovirus Incubation
1-4 days
Rhinovirus Strains
over 100 different serotypes
Very large antigenic diversity
Rhinovirus replication
Cytoplasm
Attaches to intercellular adhesion molecule 1 (ICAM-1) or the very low density lipoprotein (VLDL) receptor
Rhinovirus Symptoms
Frequent cause of upper respiratory infection
Red nose (hyperemic)
Nasal discharge becomes mucorepelent (neutrophils)
Lasts 2-3 days with viable shedding - shedding can last up to 3 weeks
Rhinovirus Transmission
Humans are the only known reservoir
Rhinovirus Complications
Epithelial damage - likely due to the immune system
Rhinovirus Treatment
No antivirals
Rhinovirus Prevention
Because there are so many serotypes, vaccine development is impractical
