Vaccine for Parkinson’s Disease Enters Phase 1 Clinical Trial
The word “vaccination” generally brings to mind the prevention of infectious disease. However, significant advances have recently been made in the field of therapeutic vaccination for the treatment of chronic human disorders including neurological conditions and cancer.
Simply put, a vaccine is a mixture of compounds (most often proteins) that are selected for their ability to activate the immune system. These compounds, also known as antigens, are then injected into the body where they prepare the immune system for a future assault. The result of such prophylactic vaccination is either complete immunity to the illness, or at least a significant reduction in disease severity.
While a prophylactic vaccine is administered as a preventative measure, therapeutic vaccines are intended to help fight a disease that has already taken root. For example, a therapeutic vaccine might be given to a patient with cancer in order to enlist the patient’s own immune system in the fight against the disease.
The problem with this kind of approach is ensuring that the antigen used in the vaccine does not induce an immune response against healthy parts of the body. Again, using cancer as an example, diseased cells often contain mutated proteins, or proteins that are not usually expressed in adult tissue (known as onco-fetal genes). This means that vaccines using these antigens specifically target cancer cells.
Recently, a therapeutic vaccine for Parkinson’s disease developed by Austrian pharmaceutical company Affiris entered a clinical trial, a landmark move in the management of a disease that is currently only treated at a symptomatic level.
Patients with Parkinson’s disease suffer from a number of debilitating symptoms that are the result of the loss of a particular class of neurons in the brain. These neurons are involved in the control of muscle function and are particularly sensitive to the neurotransmitter dopamine. It is for this reason that current treatments revolve around modulation of the levels of this chemical.
The underlying molecular cause of the disease is a protein called alpha-synuclein. Ordinarily this protein is found throughout the neocortex, hippocampus, thalamus, substantia nigra, and cerebellum, although its precise function remains unknown. Importantly, this protein is very unusual in that it does not fold up like the majority of proteins. Its “floppy”, unfolded appearance means that it is particularly susceptible to getting tangled up and forming protein aggregates within brain cells, thus sentencing the affected cell to death. The formation of protein aggregates also underlies other brain disorders, including Alzheimer’s disease and Creutzfeld-Jacob disease.
It is the alpha-synuclein protein tangles that are targeted by the vaccine currently in trials, PD01A. The study, funded by the Michael J. Fox Foundation to the tune of $1.5 million, will assess the safety of the vaccine in both men and women with Parkinson’s disease, with the results expected in July of 2014.
Given the prevalence of protein aggregates in brain diseases, therapeutic vaccination might therefore represent a promising future treatment for several neurological conditions.
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