The Johns Hopkins News-Letter
As the dreaded allergy season gets underway, many are taking the time to stock up on various medications in an attempt to ward off the inevitable sneezing, coughing and watery eyes that mark this time of year. However all that effort may soon be unnecessary, thanks to a new vaccine developed by researchers at the Hopkins School of Medicine.
The experimental vaccine uses a DNA-based approach to help prevent ragweed allergies known commonly as "hay fever." The vaccine is delivered through six injections and has been shown to significantly reduce symptoms of allergic reactions in a study completed by researchers at the JHU Asthma and Allergy Center.
Ragweed allergies, the main cause of hay fever in the fall in the United States, affect as many as 40 million people per year. The vaccine may soon bring long-lasting relief to sufferers of hay fever as well as other pollen allergies that could be similarly treated.
A specific DNA sequence, derived from bacteria, was isolated by researchers in 2000 at the University of California, San Diego, and was found to restrict the activity of a particular type of immune cell known as Th2 cells. T-helper cells, including Th2 cells, are involved in the inflammatory response in the body when it is attacked by a foreign particle.
Recognizing that most allergic diseases are caused by Th2-mediated inflammation, the Hopkins team began studying ways to use this DNA sequence for therapeutic purposes. By attaching the sequence that shuts down Th2 cells to a protein found on ragweed pollen, lead investigator Peter Creticos, M.D., and his group, in conjunction with Dynavax Technology Corps of Berkeley, Calif., were able to develop a vaccine that prevented the onset of hay fever symptoms.
The study was funded by the Immune Tolerance Network, which is supported by the National Institute of Allergy and Infectious Diseases at the National Institutes of Health. The findings are published in the Oct. 5 issue of the New England Journal of Medicine.
The vaccine acts by helping the body handle inflammation of the nose and eyes and preventing typical allergic reactions such as sneezing and coughing. Th2 cells signal the body to produce the protein IgE, which is responsible for causing most allergy symptoms. By preventing Th2 action, the vaccine reduces levels of IgE, thereby reducing the natural inflammatory response.
The vaccine may also activate a type of immune cell called dendritic cells, which balance the inflammatory response in the immune system in response to disease. The combined interaction of these pathways helps the body return to its normal state by essentially "turning off" the allergic response.
A clinical study was conducted during two fall seasons when hay fever incidence is at its highest. Twenty-five volunteers who had a significant previous history of allergies to ragweed were enrolled and divided into two groups.
Over the course of six weeks, 14 volunteers received the vaccine while 11 received a placebo injection once a week. Allergy symptoms were recorded for all patients, including coughing, sneezing, watery eyes and runny noses.
When compared to the subjects receiving the placebo, the vaccinated group experienced a 60 percent reduction in all of the measured allergy symptoms.
Allergy symptoms were equally reduced when measured one year later, during the next hay fever season, even though the subjects did not receive any new injections of the vaccine. This lingering effect was cited by the team as proof of the effectiveness of the vaccine.
Because the effects of the vaccine did not wear off quickly, this vaccine is a good candidate for the future treatment of hay fever. A new study with an even larger group of participants is currently underway to further examine the lasting effects of the DNA-vaccine.
If the DNA-based vaccine proves to be effective in larger studies, it could be a major advancement in therapy for allergies, replacing complicated immunotherapy treatment that can last five or six years with a simple six-week injection program.
Its use could also dramatically reduce the need for conventional medicines that aid in managing allergy symptoms, such as antihistamines and decongestants, and in turn would improve quality of life for chronic victims of allergic rhinitis.
