Influenza Flashcards
What is the structure and type of nucleic acid found in influenza?
Single Stranded RNA
- polarity: meaning it is complementary to mRNA and must be converted
Describe the capsid of influenza virus.
Helical nucleocapsid composed of RNA
Structural proteins: NP, PB1, PB2, PA
What are the two glycoproteins contained within the influenze envelope?
H - hemaglutinin
N - neuraminidase
What is RNA transcriptase?
RNA-RNA polymerase contained in the nucleocapsid complex
Converts -RNA to +RNA
Cells do not have this
What are the antigens of the influenza virus?
Nucleocapsid and M protein
How are the H antigens detected?
Hemagglutination
Neutralization
C-fixation
How does influenza attach to the cell surface receptor?
Hemagglutinin of the virus binds to sialic acid containing receptors
How does influenza penetrate the cell?
Via an endocytic process and is enclosed within a vacuole
How does the influenza virus exit the vacuole?
The acidic environment of the vacuole facilitates hemagglutinin to initiate fusion between the virus envelop and vacuole membrane
What is the site of both transcription of viral mRNAs and viral genomic RNA for influenza?
Nucleus
What two functions does the +RNA made from -RNA serve?
mRNA
Template RNA involved in genome replication
What is the structure of the viral mRNAs in influenza?
3’ poly A tail
Donated short capped RNA at 5’ end (donated by cellular mRNA)
Where are viral mRNAs translated?
Both H and N glycoproteins are translated on ER ribosomes and free ribosomes
What happens to the H and proteins after translation?
Accumulate in the Golgi Apparatus and are then inserted into the cell membrane where budding sites are formed
How is the influenza genome replicated?
Viral RNA polymerase copies -RNA into +RNAs
The +RNAs serve as a template for synthesis of many negative stranded RNAs
What results in infectious influenza virus particles?
Proteolytic cleavage of H
What are the two functions of Neuraminidase?
Important in budding of progeny virus particles
Lowers viscosity of mucus in vivo during infections
What is the major anitgen for influenza immunity?
H
How does influenza exhibit antigenic drift?
Point mutations in H and N
How does influenza exhibit antigenic shift?
Animal influenza virus and human influenza virus exchange RNA segments
Results in pandemic about every 10 years
What does antigenic shift result in?
The presentation of entirely new antigens to population with no immunity
What is antigenic sin?
With each new infection with influenza A an individual responds with the strongest antibody against the 1st subtype which infected that individual
