Emory University scientists reported today at the Experimental Biology 2000 meeting in San Diego that glutathione, a naturally occurring anti-oxidant compound, could help prevent infection by the influenza virus if administered directly to the tissues lining the mouth and upper airway. The scientists suggested that glutathione concentrated in a lozenge or spray might be the most effective way to use the compound as a flu preventive.
Glutathione, which occurs naturally in a variety of foods, has been shown in research studies to reduce cellular damage by reactive oxygen from a variety of cancer causing agents, including ionizing radiation and environmental carcinogens. Studies by Dr. Jones and his colleagues on the potential role of dietary glutathione, however, have previously found that the body does not appear to use the compound on a systemic basis to ward off disease.
While studying the role of glutathione as an anti-cancer agent, the Emory scientists discovered that one of the enzymes that uses glutathione to detoxify cancer-causing chemicals and oxidants is deposited in the mucous layer lining the mouth and nose, thus providing an extracellular barrier to toxic chemicals. This led them to consider a possible role for glutathione as an anti-flu protectant.
The flu virus is normally released from infected cells as an inactive particle. To infect another cell, it must be activated by having one of its proteins cleaved (split into two pieces) by a protease enzyme. Proteases, along with proteins that normally inhibit their activation, are present in the fluid that lines the epithelial cells (the cells that line the mouth, upper airways and intestine). Scientists have found through studies in mice that viral infections result in oxidative responses that inactivate natural protease inhibitors, thus enhancing viral activation. They also have found that activation of the virus particles could be controlled by oxidation reduction reactions.
Knowing that glutathione is an anti-oxidant and that it is present in the mouth and nose linings, Dr. Jones exposed normal human airway epithelial cells in culture to flu virus either without or with glutathione in order to test its protective ability against the flu. With high concentrations of flu virus, the glutathione showed no protective effect, but with lower concentrations similar to the amount present during a normal human flu infection, the cells were completely protected against infection.
Dr. Jones then infected two groups of mice with a mouse-adapted strain of a human influenza virus. The mice that had been given drinking water containing glutathione had a significant decrease in viral production compared to animals whose water did not contain glutathione.
"It appears that by going directly to the site of infection with we can block the influenza infection in the upper airway," says Jones. "We believe that if we put the glutathione in a lozenge, we could directly expose the virus-susceptible tissues to glutathione over a relatively long period of time. This could be very helpful, for example, if you were sitting next to someone with the flu on an airplane. You could effectively block the infection for a period of several hours."
Although the data suggest that a glutathione lozenge would probably work, the concept should be tested in humans, Jones says. And a glutathione lozenge should not be considered an alternative to taking the flu vaccine.
"There is a natural variation among people in resistance to viruses and in our natural antioxidant system," he explains. "If we are smokers, if we are deficient in anti-oxidant vitamins, if we are under stress, or as we become older, we become more oxidized, which makes us more vulnerable to viral infection. This direct exposure to glutathione could be part of an overall strategy to enhance our anti-oxidant defenses."