Lecture 23 - Influenza Flashcards
What type of genome does influenza virus have?
8 segments of (-)ssRNA
What viral family does influenza virus belong to?
Orthymyxoviridae
What can change your immunity to a type of influenza?
when it mutates
What are the 2 types of mutations?
antigenic shift and antigenic drift
What are the characteristics of the influenza viral capsid?
enveloped containing hemagglutinin (HA) and neraminidase (NA) antigenic glycoprotein spikes on the surface
What helps us name the influenza viruses? What is it based on?
HA and NA proteins
What are the 4 influenza viral capsid proteins?
HA, NA, M1 and M2
What are M2 influenza viral proteins?
ion channel proteins
What species is influenza A H1 found in?
human, swine, bird
What species is influenza A N1 found in?
human, swine, bird
What species are most of the H and N subtypes of influenza A are found in?
birds
What is the issue with the influenza A H1N1?
it is in 3 different species including humans
What does HA protein bind to?
sialic acid
Where is sialic acid found?
present on glycoproteins of ciliated cells lining the sinuses and airways
How does the influenza virus enter the cell?
receptor-mediated endocytosis
In order for the influenza viral genome to exit the endosome, what must happen?
drop the pH from 7 to 5 to expose fusion peptide proteins = triggers fusion with endosomal membrane and viral membrane to deliver the viral RNPs (ribonucleoproteins)
What is the function of M2 proteins?
the ion channels allow hydrogen ions to penetrate virion
Where does the influenza virus replicate its genome?
cytoplasm
What is the function of the M1 protein?
matrix proteins that holds the vRNPs together
How are the M1 proteins dissociated from the vRNPs?
increase in hydrogen ions weakens the matrix proteins association from the vRNPs
What happens to the vRNPs once released into cytoplasm?
is directed towards the nucleus and enters it
What helps initiate genome replication?
the proteins on the end of the genome
What are 2 things that will be synthesized from copying the (-)ssRNA genome?
the viral mRNA and the (+)ssRNA template (antigenome)
In order for the viral mRNA to be translated by the host cell ribosomes, what modification must the virus do its viral mRNA?
snatch a 5’ cap to put on it
What is the function of the influenza viral protein NS1?
prevents nuclear export of cellular pre-mRNAs by trapping them in the nucleus
What is the 5’ cap used/beneficial for the influenza virus?
as a primer to initiate transcription of viral RNA
What intermediate is formed during influenza viral replication?
double-stranded RNA (dsRNA)
Which influenza viral protein binds and sequesters the dsRNA intermediate?
NS1
Where does assembly of the progeny influenza virion occur in the cell?
cell membrane
How are new influenza virions released?
budding off
Which organ does influenza virus initially enter the body through?
respiratory tract
In the lungs, what does influenza virus infect?
pneumocytes lining alveoli of the lungs
What do the pneumocytes release as the influenza virus replicates?
cytokines and chemokines
What mediates genetic variation that causes new strains of influenza to appear more often than yearly?
antigenic shift and antigenic drift
What is antigenic drift responsible for?
localized/seasonal influenza epidemics caused by types A or B
Where do the mutations in the influenza virus occur in the antigenic drift process?
in the HA and/or NA genes
What is antigenic shift responsible for?
pandemic strains
In which genetic variation process are new influenza virions produced?
antigenic shift
Which genetic variation process allows for influenza viruses to move from animals to birds in order to infect humans?
antigenic shift
Why was the H1N1 Swine flu pandemic alarming?
traced to an antigenic shift resulting in triple reassortment of bird, human, and pig viruses
What is a consequence of a single mutation within the H5N1 strain?
allow the influenza virus spread more efficiently
What was significant of the H5N1 influenza virus strain?
jumped directly to infecting humans which never observed before; same strain was killing chickens
What animal reservoir does the H5N1 infleunza virus strain infect?
birds
What type of genetic variation process did the H5N1 strain undergo?
antigenic drift – did not combine with human strain
What happens when the M2 ion channels are inhibited?
prevents uncoating step
What is the issue with using antivirals that inhibit the M2 ion channels?
the virus develops drug resistance
What happens with the NA capsid protein is inhibited?
prevents NA from cleaving sialic acid during budding
What is the most effective way to prevent influenza?
vaccines
Why does recombination occur within influenza?
due to segmented genome
What are 3 distinguishing characteristics about the H7N9 strain?
in birds and humans | combo of 3 viruses fromwild birds and domesticated ducks and chickens | short lived
