Dr. Margaret G. McKernan, MD Parkinson’s disease is a devastating brain disorder causing a number of neurological symptoms including tremors, muscle stiffness and slowing of movement. The disease usually strikes individuals over the age of 50, although young-onset forms of Parkinson’s can occasionally run in families. Parkinson’s is progressive, meaning that the symptoms continue to worsen over time. What starts as a mild tremor at the time of diagnosis eventually evolves into the inability to perform the most basic everyday tasks. It is estimated that four to six million people worldwide suffer from Parkinson’s disease, or as many as 1 in 100 people over the age of 60.
Current therapy for Parkinson’s disease
There is currently no cure for Parkinson’s disease. Available drug therapies focus on replacing or mimicking the actions of dopamine, a neurotransmitter (chemical in the brain). Loss of dopamine-producing cells in a specific part of the brain called the substantia nigra leads to the problems with coordination and muscle activity that characterize Parkinson’s disease. Two main classes of drugs are utilized: Levodopa and dopamine agonists. Levodopa (L-dopa) is a precursor to dopamine, meaning that the body can use administered levodopa to increase the amount of dopamine in the brain. Levodopa significantly improves motor function, but can cause side effects including involuntary movements, and tends to become less effective after four to five years. Dopamine agonists such as bromocriptine (Parlodel) mimic dopamine by stimulating the same nerve cells in the brain. These medications are less effective than levodopa, but can be useful in early stages of the disease.
Vaccines as therapeutic agents
Most people are familiar with the use of vaccines to prevent disease. Childhood immunizations are a series of vaccinations that prevent children from contracting serious illnesses including measles and rubella. Many adults receive yearly flu vaccinations. These vaccines all work by exposing the body to a small amount of weakened virus or bacteria, causing the immune system to form antibodies that protect against future infection.
Scientists are starting to use this same strategy to fight noninfectious diseases. One example is a vaccine for the skin cancer, melanoma. Given to patients already diagnosed with the disease, the vaccine ‘teaches’ immune cells known as T cells how to recognize specific proteins on the cancer cells, known as antigens. This allows the ‘killer’ T cells to specifically seek out melanoma cancer cells and destroy them. In clinical studies, this leads to increased survival, without some of the significant side effects of standard chemotherapy, which destroys normal healthy cells as well as tumor cells.
Introduction of the first vaccine for Parkinson’s disease
In June of 2012, Austrian company AFFiRiS AG announced that it had begun clinical trials on the first ever vaccine to attempt to treat Parkinson’s disease. The aim of the vaccine is to teach the immune system to produce antibodies directed against a specific protein linked to Parkinson’s disease known as alpha-Synuclein (alpha-syn). Scientists believe that alpha-syn binds to a protein disposal site, known as a lysosome, inside dopamine nerve cells. Alpha-syn remains tightly bound to the lysosome, blocking the disposal of other proteins. This leads to a build-up of toxic proteins within the cell, eventually leading to cell death. Blocking this sequence of events via the actions of a targeted antibody is hoped to slow the progression or even reverse the course of Parkinson’s.
Vaccine represents a significant new direction in the treatment of Parkinson’s
This study is being supported in part by the American Michael J. Fox Foundation. A well-known actor from such films as Back to the Future, Michael J. Fox has become the public face of Parkinson’s since going public with his diagnosis in 1998. Up until now, treatment for Parkinson’s disease has focused on treating the symptoms of the disease, the tremors and muscle stiffness, by increasing the amount of dopamine available to brain cells. This vaccine represents the first therapy aimed at the root cause of the disease, with the potential to modify the course of the disease, rather than simply slowing symptom progression. For patients like Fox, facing the inevitable failure of the currently available drugs after a number of years, the vaccine offers new hope for the future.