Vaccine terms
Vaccines
Adjuvants: Antibody enhancing
agents. Chemical substances which are supposed to enhance the immune response to the
vaccine.
Attenuated: Heat or chemically treated.
Conjugated: segments of one antigen are linked with those of
another antigen. Eg Hib antigen & diptheria antigen.
Killed or inactivated vaccines:
Live vaccines:
diploid cells (aborted fetal tissue)
Cell lines (Human fetal):
MRC-5 (Medical Research Council 5): MRC5 originates from the lung tissue taken from
a 14 week male fetus aborted for "psychiatric reasons" from a 27 year old woman
in the UK in the 1970s
WI-38: WI -38 originates from a female fetus aborted for "psychiatric reasons" in the 1960s. These abortions were not done for the purpose of producing vaccines
A toxoid is a modified bacterial toxin that has been rendered nontoxic but retains the ability to stimulate the formation of antibodies.
13) Attenuation
(a) Attenuation is a decline in virulence imposed on a pathogen by growing the pathogen
under conditions that decrease its adaptation to growth on a given host; this is often
done by growth in tissue culture or in otherwise non-host species
(b) That is, by increasing a pathogen’s adaptation to one condition (e.g., tissue
culture), the pathogen’s adaptation to another condition (e.g., us) may be reduced
(c) Attenuation is often employed in the development of live vaccines (e.g., Sabin oral
polio vaccine)
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Live vaccine (live-attenuated vaccine)
(a) Live vaccines result in infection but not disease, and confer the most long-lasting
immunity
(b) Live vaccines typically are attenuated so that while they can still cause infection,
they have a reduced propensity to cause disease
http://www.google.com/search?q=%22live-attenu...
http://www.stanford.edu/group/virus/1999/tomm...
Live Attenuated Vaccines
Most of the live attenuated vaccines in use today are derived from serial passage in
cultured cells, including human diploid cells (e.g. fetal lung tissue, other fibroblasts),
monkey kidney cells, and chick embryos, among others. Adaptation of the virus to growth in
the cultured cells is accompanied by a gradual loss of virulence for the natural host. The
neurovirulence of the attenuated virus is tested in mice and primates before conducting
trials with humans. This procedure relies on the accumulation of point mutations to confer
avirulence; however, more exact mutations can be attained through genetic engineering.
Temperature sensitive mutants, deletion mutants, site-directed mutatgenesis, and live
recombinant viruses are all methods that are commonly employed to achieve viral
attenuation. These vaccines generally possess the following properties:
derived from wild virus
attenuated through repeated culturing or recombination
must replicate to be effective
produces strong cellular immune response similar to natural infection
severe reactions possible in immunosuppressed vaccinees
can revert to pathogenic form
require only one or two doses
interference from circulating antibody
require refrigeration or lyophilization (freeze-dry)
unstable