Flashcards in Viral Respiratory Infections Deck (79)
What family is Rhinovirus in?
What is the major disease caused by Rhinovirus?
Common cold (rhinitis)
How is rhinovirus transmitted?
Airborne, person to person
Why does rhinovirus preferentially infect nasal epithelium?
Prefers the cooler temperature of nasopharynx (33) than internal body temp (37)
What is the structure of the virion of Rhinovirus?
Non-enveloped, single strand RNA virus
VP1, VP2, VP3 make up capsid
Has IRES (internal ribosome entry site)
Why is there no vaccine for rhinovirus?
Too many epitopes of the capsid proteins, gives >100 different subtypes
What is the funtion of IRES?
Internal ribosome entry site
In front of each gene, ribosome finds it and starts translation
What are the steps of replication of Rhinovirus?
Endocytosed in vesicle
Uncoats and releases RNA into cytoplasm
RNA translated in *cytoplasm* with host ribosomes (targeted to IRES)
Long polyproteins get cleaved by proteases
New vesicles are formed with new viral RNA
Virions form and are released by cell lysis
What is the host response to Rhinovirus infection?
Induction of chemokines and cytokines that recruit inflammatory cells
Airways respond by contracting, increasing in mucus, increasing inflammation
What family is Influenza virus in?
Myxovirus - specifically orthomyxoviridae
What are major difference between orthomyxoviridae (influenza) and paramyxoviridae (parainfluenza, measles)?
Ortho - nuclear replication, segmented -sense RNA
Para - cytoplasmic replication, non-segmented -sense RNA
What is the most pathogenic type of influenza? (A, B, or C)
How many segments are in the influenza virion?
How are strains of influenza named?
Type/Place/Number of isolate/Year (Major type of HA and NA)
Example: A/California/07/2009 (H1N1)
What is the mode of transmission of influenza?
Aerosols, direct contact
What are the steps of replication of influenza virus?
HA binds to sialic acid on surface of cell
Virus is endocytosed and endosome acidified
*Acidic environment* causes conformational change in HA, causing it to fuse with membrane and release viral RNA into cytoplasm
Viral RNA goes to nucleus for replication
Viral RNAs exported from nucleus and translated
New virions made, bud from cell
What cells does influenza primarily infect during infection?
Less cilia = less mucus, higher titer virus, more infected cells
What is antigenic drift?
Minor year to year variation that occurs by random mutations in HA and NA
What is antigenic shift?
Major reassortment of gene segments that leads to novel viral allele combination and can lead to increased virulence
What family is Parainfluenza in?
What disease do Parainfluenza type 1, 2, and 3 cause?
What is a major similarity and a major difference in the virion/genome of Influenza and Parainfluenza?
Similarity: Both contain own polymerase that starts working to replicate virus right when it enters cell
- Influenza requires acidic pH for fusion, parainfluenza requires neutral pH
- Influenza replicates in nucleus, parainfluenza in cytoplasm
What are the steps of replication of parainfluenza?
Virus binds sialic acid on surface of cells
Fusion occurs at neutral pH
Viral mRNA is transcribed in cytoplasm
Proteins are processed in ER and Golgi
Virions bud from cell
How does parainfluenza block innate immune response?
Like other paramyxoviruses, can inhibit induction of interferon or degrade the proteins that turn on interferon induced genes
What is the mode of transmission of Parainfluenza?
Aerosols, direct contact
What virus causes most serious pediatric respiratory infections?
RSV (respiratory syncytial virus)
What is the structure of the virion of RSV and metapneumovirus?
Nucleocapsid in lipid envelope
Also contains own polymerase (like influenza and parainfluenza)
Where do RSV and metapneumovirus replicate (cytoplasm or nucleus)?
Which is more severe, RSV or metapneumovirus?