What’s a vaccine to you?

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A vaccine against ignorance?  “Humanity certainly needs to be immunized with a vaccine for ignorance, and we propose that that vaccine is education. But education would have to be coupled to restrictions on people, agencies, and corporations determined to follow the profit motive, and in so doing, undermine the intelligence of the populace.”

Vaccines have been so good at preventing disease, that the above article uses ‘vaccine’ metaphorically to describe prevention of ignorance.  And has been used to describe other preventive interventions: what would you like a vaccine for?  Something to stop what you don’t want.  I would like a vaccine to be more kind and less mean; to love.  Sadly, we have not yet discovered that.  But education and changing the economic system could help.

The picture above uses shapes, sizes, and colours to show different bugs; and the hand as defence that stops them. Vaccines stop harmful bugs by preparing our defences. A vaccine does not protect against bugs in general, only the specific bug that it targets. It does this by ‘looking like’ the bug to our immune system.

History of vaccines

For nearly half its history, the word ‘vaccine’ only referred to smallpox vaccine. In 1796 (end of 18th century) Edward Jenner showed that  inoculation with cowpox protected against smallpox.  Jenner described the process as vaccination.  Vacca is Latin for cow, and vaccinus means ‘of a cow’.

The next vaccine creator was  Louis Pasteur. His experiments helped to establish the germ theory of disease by the late 19th century (around 1880). He modified both bacteria (Cholera, Anthrax) and viruses (Rabies) to develop vaccines against these bugs.  And used the word ‘vaccine’ for agents that provided immunity.  He did this in honour of Jenner’s vaccination for his proof that artificial immunity led to protection.

In 1996 (just before the millennium), we celebrated the bicentenary (200th) birthday of immunisation. For nearly a century (100 years) after Jenner,  the term ‘vaccine’ only referred to smallpox vaccine.

: rough calculation to understand the first fraction: half or 1 divide by 2 or 1/2 ->

In 1996, it was 200 years of immunisation and about 100 years of the word vaccine being used more widely. If we divide, we use two very long words: numerator and denominator.  But it’s easier to just think of them as top and bot(tom), and perhaps a bit funnier?

Here the top is 100 and the bot is 200 (100/200).  And as the great thing about zeros is that they can be cancelled out, if you balance and do it top and bot. And we are left with 1/2; half.  Also known as 50%, where the percent symbol (%) means divided by 100: 50/100, or 5/10, or 1/2.   (note actual calculation is 2016: 2016-1880-1796 = 136/220.

<: back to the story of vaccine…

Antibodies and antigens

How do our clever cells of immunity use vaccines to prevent future infection? A vaccine  stimulates an immune reaction, including antibodies in the short term and immune memory, usually for life.

When the harmful bug appears, the immune system is primed to destroy it before it can cause illness. So, each vaccine is unique and specific to the to that bug.  There  are different types of vaccines, most are injected, some are taken orally or through the nose. Vaccines all contain the antigen(s) needed to stimulate the antibodies that protect against that bug.

 

 

The antigens of cowpox and smallpox virus were close enough for cowpox to protect against smallpox virus.  The antigen(s) in a vaccine and those of the bug must ‘look alike’ enough so that the antibodies that the vaccine stimulates can destroy the bug.  (Some vaccines only contain one antigen, others contain the whole bug with its many, and those in between)

The pictures show the shape of an antibody molecule.  In the first one below, the orange ‘hand’ is the site that binds the antigen. The antigen binding site is part of the variable region.  Natural selection is the force that drives evolution.  This is simplified to survival of the fittest.  In the same way, those antibodies that have the best fit to a foreign agent, like a bug that should not be there, will be selected for.  Random changes allows millions of different shapes for the variable part, and practically infinite kinds of ‘shapes’ that the immune system can ‘recognise’.

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Antibody (IgG) molecule, with orange 'hand' binding site.
(From:  http://www.novimmune.com/science/antibodies.html)

The traditional analogy is the fit of key into a lock, with complementary grooves and peaks.  The variable part of the antibody protein is selected by ‘best-fit’ to a specific antigen. The antigen is the target that the immune system selects to attack that bug.  When there is enough antibody in our blood, and invaders with that antigen will be mopped up before they can invade.

The orange fingers of the claw are shown on the picture above, but it is not so easy to see in the ribbon diagram below that shows the shape of an antibody.  Both are Immunoglobulin G (IgG) which is one of several types of antibody; but all have this as the unit model, with two ‘hands’ that can lock onto the antigen.

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Immunoglobulin G (IgG) model  (Wikipedia)

 

 

 

 

 

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