Treating Disease With Vaccines
Can therapeutic vaccines cure illnesses we already have -- like HIV, Alzheimer's disease, and cancer?
While traditional vaccines are designed to prevent disease, researchers are
working on something new: therapeutic vaccines, vaccinations that treat an
illness after you have it.
Therapeutic vaccines have the potential to change medical treatment
radically and may be able to treat all sorts of scourges, such as:
"We're at a fascinating crossroads in the development of therapeutic
vaccines," says Hildegund C. J. Ertl, MD, program leader in the Immunology
Program at the Wistar Institute at the University of Pennsylvania. "We
understand so much more about the underlying science."
But Ertl and other experts urge cautious optimism. While therapeutic
vaccines seem to be on the horizon, they've seemed that way for a long
"I remember when therapeutic vaccines were first developed for skin
cancer in the 1960s," says Richard L. Wasserman, MD, PhD,
clinical professor in the department of pediatrics at the University of Texas
Southwestern Medical School in Dallas. "But forty years later, we still
don't have one."
How Do Therapeutic Vaccines Work?
Standard preventative vaccines work by helping your immune system develop
immunity to a weakened or dead form of a germ. Then, when you actually come
into contact with the live germ, your immune system knows how to fight it
Therapeutic vaccines would be used after a person contracts a
disease, yet they would still work by boosting your own immune system's
response to an illness.
While the immune system works very well most of the time, some illnesses --
like cancer, HIV, and Alzheimer's -- don't trigger an
effective immune response. In the case of some cancers, the immune system
simply fails to recognize the invading cells. Other viruses, like HIV, can
overwhelm the immune system and shut it down before it can work.
Therapeutic vaccines help by forcing the immune system to recognize a virus
or cancerous cell. Some specific types of therapeutic vaccines include:
- Antigen vaccines. When an antigen is introduced into the
body, it provokes the immune system to create an antibody to fight it. Some
researchers are working on vaccines that will use specific cancer antigens to
force the immune system into action.
- Dendritic cell vaccines. Dendritic cells are immune cells
which prowl your bloodstream, grabbing foreign germs and bringing them to other
immune cells, which create antibodies to attack them. Researchers have had some
success in removing dendritic cells from a person, "loading" them with
dead tumor cells or dead viruses, and then injecting them back into the person.
Once the dendritic cells have been "taught" how to recognize the
invading cells, they may spur the immune system to attack.
- DNA vaccines. One problem with many therapeutic vaccines
is that the effects wear off. After a vaccination, the immune system might be
aggressive for awhile, but eventually return to normal. Some researchers hope
they can inject bits of DNA into cells, instructing them to keep the immune
system revved up and alert.
- Tumor cell vaccines. These vaccines use actual cancer
cells that are removed during surgery. The cells are then killed -- so they
can't cause cancer growth -- and tweaked in some way, often by adding new genes
or chemicals. They are then introduced into the body. The hope is that the
modified gene will get the attention of the immune system, which will then
target other cancer cells. Some of these vaccines are autologous
(using cancer cells from your own body), others are allogeneic (using
cells that came from someone else).