A new oral vaccine has been developed that uses probiotic bacteria as the delivery system, raising hopes of safer, more effective vaccinations, without the painful needle factor.
Researchers led by Mansour Mohamadzadeh, associate professor of medicine in gastroenterology at the Northwestern University Feinberg School of Medicine, has successfully created immunity to anthrax using a probiotic delivered vaccine in a preclinical study. He is also working on vaccines for a number of other infectious diseases, as well as breast cancer, using the same approach.
Aside from eliminating the need for a needle, the use of probiotics in delivering vaccines offers the promise of harnessing the full power of the body's immune system, much of which is located in the lymphatic tissues of the gut. The gut is the major route for pathogens to gain access to the body. The immune defences which prevent this from happening are not stimulated by traditional injected vaccines which bypass the gut.
"This is potentially a great advance in the way we give vaccines to people," said Professor Mohamadzadeh.
"You swallow the vaccine, and the bacteria colonize your intestine and start to produce the vaccine in your gut. Then it's quickly dispatched throughout your body. If you can activate the immune system in your gut, you get a much more powerful immune response than by injecting it. The pathogenic bacteria will be eliminated faster."
Most vaccines are proteins which would normally be broken down by the stomach acid and digestive enzymes if given orally. In Mohamadzadeh's new approach the probiotic lactobacilli protect the vaccine until it reaches the small intestine.
The new oral vaccine offers other benefits. Probiotics, are natural immune stimulators, elimating the need for additional chemicals used in traditional vaccines to trigger a local immune response. These chemicals, known as adjuvants, are often cited as the cause of many side-effects associated with injected vaccines including dizziness, arm swelling and vomiting. Probiotic vaccines also are inexpensive to produce.
The probiotic vaccine is also preferable because it stimulates both a local and systemic immune response rather than just the local response at the site of an injection. The vaccine targets the first line of gut immune cells called dendritic cells -- the commanders-in-chiefs of the immune system. They engulf the vaccine then instruct the immune system's foot soldiers -- killer T-cells and B-cells -- to seek out and destroy any cells in the body infected with a particular bacterium or virus.
Professor Mohamadzadeh's study was published in a recent issue of the journal Proceedings of the National Academy of Science. In it he fed mice the new oral anthrax vaccine, and then exposed them to anthrax bacteria. Eighty percent of the mice survived, which is comparable to the results when mice were injected with anthrax vaccine, he reports.
"Their immune response was higher and more robust than with the injected vaccine," Mohamadzadeh said. The mice generated a much higher T and B immunity against the pathogenic bacteria.
Terrence Barrrett, M.D., chief and professor of gastroenterology at the Feinberg School, said delivering a vaccine to the gut is the most logical route.
"Nature isn't used to seeing antigens injected into a muscle," said Barrett, who also is a physician at Northwestern Memorial Hospital. "The place where your immune system is designed to encounter and mount a defense against antigens is your gut."
In theory then, the new probiotic vaccine should also turn out to be safer and less likely to cause side-effects than traditional vaccines. It has been hypothesised that injected vaccines, in bypassing the gut's immune defences, triggers a shift in the balance of the immune system, resulting in a pro-inflammatory Th2 response which is associated with autoimmune disease, allergies, and possibly poorly understood chronic illnesses such as chronic fatigue syndrome (ME/CFS) and Gulf War syndrome (See: How Vaccinations Work by Philip Incao, MD).
Source: Mohamadzadeh M Duong T Sandwick SJ Hoover T Klaenhammer TR (2009) Dendritic cell targeting of Bacillus anthracis protective antigen expressed by Lactobacillus acidophilus protects mice from lethal challenge Proceedings of the National Academy of Science 106(11):4331-6
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