Influenza Flashcards
Pathogenesis
causes 3 diseases:
- URI (upper respiratory illness) or cold
- Bacterial Pneumonia
- Viral Pneumonia
(1) Upper Respiratory Illness (URI) or cold
occurs by sneezing: spectrum of particle sizes released
Incubation period: 1-2 days
fever, muscle aches
1 week in adults vs. 1.5 weeks in kids
kids who have virus for the 1st time have it longer and get more sick- more virus produced (cell mediated immunity helps adults recover faster since we’ve had it before)
cilia beat/move mucus up the tract
“bald” cells put out the mucus
– non specific response –
3 days post infection= epithelium covered in basal cells (hole between cells=runny nose)
7-10 days post infection= basal cells regenerate to become ciliated and mucus cells (mucus cells come back faster)
What flu diseases will hand washing prevent?
How effective do you think surgical masks are?
Hand washing would prevent contact transfer
Surgical masks traps particles
Diagnosis of URI
influenza like illness (ILI)
- fever >100, cough/sore throat
proven flu (PCR or viral isolation)
acute onset of profound malaise
(2) Bacterial Pneumonia
start to get sick again on day 4 or 5 (unlike URI)
inflammatory response within the pulmonary alveoli
- become solid due to build and debris
- walls of alveoli infected
(3) Viral Pneumonia
drastically high severity very quickly
walls of pulmonary alveoli become extremely thin
fluid leaks out
Prior Flu Infection
NO:
Nasal= N –> T –> L–> Survival
Total= N+T+L –> Death
YES (has cell mediated immunity):
Nasal= N -//->
Total= N+T+L –> Survival
Given a non-immune animal, how would you prove that antibody to a germ could prevent infection by that germ?
Give antibodies to one group of mice, then infect both groups
One group lives and the other dies of viral pneumonia
Host Defense Against Influenza
IgG prevents viral pneumonia, but not URI
- in blood serum (specific)
- speeds recovery from viral infection
- antibody leaks out into fluid film so when the virus comes in, it meets the antibody and can’t infect the cells
- doesn’t leak across membrane in the URI
IgA prevents viral infection of the upper respiratory tracts
- in mucus and snot (general)
Cell mediated immunity (CMI) promotes recovery
- deters spread down the respiratory tract
Components of immune system
Host Defense
Cell Mediated Immunity (CMI)
Kills virus infected cells
Not live virus
Antibody “kills” virus
1. IgG in blood and tissues
2. IgA in mucus secretions
Immunization
2 vaccines
Shots: Quadrivalent Inactivated Vaccine (QIV)
Spray: Live Attenuated Influenza Vaccine (LAIV)
both contain:
H1N1, H3N2
B (Victoria), B (Yamagata) - 2 strains of the B virus
Influenza virus
named by strain/city/isolate/year
8 (-)ssRNA segments encode 11 proteins of the virus
Error prone polymerase results in accumulation of mutations that select for hemagglutinin (HA) and to a lesser extent neuraminidase (NA) proteins present on external surface of virus
RNA makes sloppy replications = lots of mutation
how does HA function in virus attachment?
HA grabs hold of the cell enabling the virus to stick and then penetrate
CDC Vaccine Recommendation
all children 6 months and up should be immunized against flu with either the spray or shot
Shots only give antibodies in blood stream (IgG)
Spray gives antibodies in mucus secretions (IgA)
Which vaccine is better for most children?
Live Attenuated Influenza Vaccine (LAIV)
why doesn’t it work for older people? Elderly have enough IgA
Live Attenuated Influenza Vaccine (LAIV)
Induces:
- serum IgG antibody (drift sensitive) –specific
- secretory IgA antibody (cross protective) –grabs hold of virus
- CMI (cross protective)
has no mercury in it
Live virus induces cell mediated and the other 2 antibodies
Quadrivalent Inactivated Vaccine (QIV)
Induces only serum IgG antibody (drift sensitive)
cannot cause the flu
- injected in arm & virus only grows in epithelium
which vaccine is more effective for adults?
Trivalent influenza vaccine (dead virus)
Although in theory LAIV should be better than TIV;
TIVs have been shown to be more effective for adults
Vaccine: Shots induce…
serum antibody (drift sensitive)
Vaccine: Spray induces…
serum antibody (drift sensitive) secretory antibody (cross protective) CMI (cross protective)
M2SR Vaccine
flu vaccine of the future
M gene codes for 2 proteins.
M2 is a trans membrane protein
SR stands for Single Replication
Membrane through the channel of the virus that allows protons to go through
Issue with M2SR
Vaccine given by spray infects the nasal epithelium but can’t replicate or spread
Grown in tissue culture
How do you grow a vaccine that can’t replicate?
grow the virus in tissue culture and put the M2 gene into the tissue culture cells, so the virus can grow (bad gene, but good M2)
Insert the normal M gene into the cells of the tissue culture
Why do vaccines change each year?
shifts & drifts
mutations in HA and NA
