Lec 16 - Viral Vaccines 1 Flashcards
first origins of vaccination
variolation
2000yrs ago, inhalation of powdered small pox scabs
how did variolation develop in the 1700s
scab crust from mild smallpox cases inoculated into the skin
= a form of live attenuated vaccine
Edward Jenner
first successful vaccination
cowpox material to prevent smallpox
formed the basis of the modern smallpox vaccine
why was the initial vaccine by eddy jenner not the best
unstable
lost potency over time
so they freeze dried it = could be more widely distributed
what was first inactivated vaccine
by Pasteur and Roux
against rabies
based on dried spine material of infected rabbits
how has the rabies vaccine developed
now use human cell lines to generate the material
- purified via a filter
- inactivated by beta-propriolactone
5 types of vaccines
- whole inactivated virus
- attenuated live virus
- purified subunits
- DNA (not approved in humans yet)
- RNA
which vaccine gives lifelong immunity
attenuated live virus
ways to get an attenuated live virus
- using related virus from another animal
-administration of pathogenic/attenuated virus through unnatural route - passage of virus through unnatural host
- passage of virus at sub optimal temp.
problems with live attenuated
- under attenuation
- reversion of the mutations
- instability
- heat labile
(hard to distribute) - contamination of viral cell culture
example of virus produced via the use of unnatural host cells and sub optimal temperatures
measles vaccine
common chemicals used to inactivate viruses
formalin
beta-propiolactone
what do inactivated vaccines require to stay effficient
boosters
general dose needed for live vs attenuated
live = low
inactivated = high
what is adjuvant
a substance that enhances the body’s immune response to an antigen
antibody response from live vs attenuated
live = good = IgG from bloodstream, IgA from mucosal membranes
and cell mediated response
attenuated = IgG only, no cell mediated response
why doesnt live vaccine need boosters
strong enough immune response on its own
also
replicates itself (unlike inactive) = amplifies the immune response itself
what is the current polio vaccine given
Inactivated Polio vaccines IPV
what kind of immunity does IPV give
IgG mediated immunity in blood
so can still injest polio and it replicates in gut
but prevents progression to CNS via blood
= need 3 doses for 99% immunity
OPV
trivalent oral polio vaccine
the live attenuated version which targeted all 3 serotypes
primary attenuating mutation of OPV
One of the mutations was the virus had reduced ability to translate its RNA template in the host cell
how is OPV effiecient in protecting non-vaccinated individuals
live virus shedding in stools of vaccinated people
so non vaccinated people gaining immunity
what serotypes of polio still around
3 serotypes
2 have been eradicated
only Type 1 still circulating
how many cases of paralytic polio occured with OPV
1 in 750,000
but in areas where chance of getting gpolio was 1 in 100, was deemed acceptable risk
then was replaced by IPV
