Influenza & Ebola Flashcards
Influenza structure
enveloped negative sense ssRNA
Influenza entry & transmission
- droplets enter respiratory tract
- binds to sialic acid containing receptors (SA alpha 2-6 linkage with galactose)
- fusion of membranes via acidic conditions
- virus replicates, causing inflammatory response and therefore symptoms
types of Influenza
- type A, B & C
- A & B for humans
- A can infect animal reservoirs
hemaglutinin (HA)
assists virus entry into cell by binding to sialic acid linked to galactose receptors
neuraminidase (NA)
assists virus exiting the cell by cutting SA from HA receptor
M1
structural, rigid matrix that holds virion together
M2
ion protein
ribonucleoproteins (RNP)
polymerase, RNA, nucleoproteins
nuclear export proteins (NEP)
moves products into and out of nucleus
non structural protein (NSP 1)
anti-interferon activity
current influenza A subtype infecting humans
H1-N3 & H3-N2
How do replicated virions become infectious?
trypsin must bind to the hydrophobic fusion peptide of recently cleaved HA
Influenza innate immune response (immediate)
- lung surfactant proteins prevent viral binding
- collectins bind to HA & NA to block binding process
- triggers lectin pathway of complement cascade
Influenza innate immune response (delayed)
- infected epithelial cells produce type 1 interferons
- PAMP-PRR interactions trigger inflammatory cells
- cytokine release
Influenza adaptive immune response
- CD8+ cytotoxic T cells
- antibody to HA & NA
antigenic drift
single mutations in viral replication creates new strains within subtypes, mutations must occur in all 5 antigenic sites before antigenic drift occurs and an epidemic breaks
Influenza diagnosis - rapid diagnostic test
To determine if type A or type B
- positive for A: C & flu A line
- positive for B: C & flu B line
- positive for A & B: C, flu A & flu B
- just C = negative for influenza
Influenza diagnosis - culture & HIA test
To determine which strain/subtype
- allantoic fluid from infected embryonated avian eggs
- reference antisera (from ferrets/rabbits) inhibits agglutination of HA with red blood cell sialic acid
Influenza vaccine
inactivated trivalent vaccine: type A H1N1, type A H3N2, type B
Influenza treatment
- adamantanes: M2/ion channel blockers, only active for type A
- relenza (zanamivir) & tamiflu: NA inhibitors, active against A & B
Ebola structure
negative sense ssRNA
Why is ebola so dangerous?
- highly contagious, transmission through any direct contact with bodily fluids
- no vaccines or treatments
antigenic shift
introduction of new subtype of influenza, therefore creating a pandemic
