Vaccination: The original paper       ;           other treatments

How it works by Anne R. Lindsay, Ph.D.

The principle behind an Alzheimer's disease vaccine is the same as that behind all other vaccines.  By injecting the substance contained in a vaccine, we provoke an immune system response that leads to the production of antibodies, cells that bind to disease-causing agents and set of a sequence of events that destroy the disease-causing organisms. 

Our immune systems are remarkable machines.  We develop protection against all kinds of pathogens (agents capable of causing disease) in the environment.  When such a pathogen is detected in the body, lymphocytes (a type of white blood cell) produce the antibodies and begin the attack on the foreign substance and eventually kill the pathogen.  The efficiency of the immune system is the reason people who have had organ transplants must take anti-rejection drugs.  Without the drugs, the immune system recognizes the new organ as foreign and attacks the organ, leading to organ rejection.

The immune system also maintains a kind of memory bank.  When pathogens are encountered that have been in the system before, antibodies recognize the old pathogen and immediately attack and destroy it.  Responses are specific for diseases.  Thus, a person who has had the chicken pox is immune from the disease and will not contract it again despite exposure to it.  Those antibodies, though, will not protect you from other diseases.

Vaccines almost seem counter-intuitive.  By injecting a form of the disease from which we want to protect the individual, we create immunity to that disease.  But there are important differences between the substances used in vaccines and the actual pathogen.  Vaccines are produced in different ways.  One way is to kill the pathogen.  The polio vaccine is an example of a vaccine that uses pathogens that have been "killed."  What are left are the antigens (substances that the immune system bind to, eventually “recognize,” and kill) that will provoke an immune response.  Another way of making a vaccine is to isolate part of the pathogen and use only the part that will not cause the disease that we are trying to prevent.  Still another way is to attenuate the pathogen so that the immune system will recognize and kill it but it is not strong enough to cause the disease – the measles vaccine is an attenuated vaccine.  There are other means by which vaccines are created, but the above provide enough overview to make the point: vaccines are created out of the very substances we are trying to kill.  They are created in a way that will both protect the individual from developing the disease as a result of being vaccinated and which will protect the individual from contracting the disease due to naturally occurring pathogens.

Again, the principle behind the Alzheimer’s vaccine is the same as that behind all other vaccines.  Dr. Delacourte describes the vaccine as being directed at the amyloid deposits that are so prevalent in the brains of people with Alzheimer’s disease.  In the case of Alzheimer’s disease, it is believed that amyloid proteins are neurotoxins responsible for killing brain cells in the brains of people with Alzheimer’s disease.  These are, effectively, the pathogens that will be targeted.  By injecting amyloid proteins that will provoke an immune response to those proteins and protect the brain from the neurotoxic effects of the amyloid proteins.

Dr. Delacourte goes on to say that studies on special mice bred to produce this destructive amyloid show that the brain can produce mount an immune response and produce antibodies that rid the brain of the amyloid deposits.  It is not yet known if the vaccine will have the same result in humans.  If it does, we can block the pathogens that cause the disease, thus providing a way of preventing Alzheimer’s disease and possibly even ameliorating and halting the effects of the disease for those who have already developed Alzheimer’s.

The success of the Alzheimer’s vaccine is predicated, in large part, on the premise that amyloid is the neurotoxin and that there are not other causative factors in play.  Only time and continued clinical trials will tell.

Anne R. Lindsay, Ph.D.