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Researchers Cracking Peanut Allergy Puzzle

April 05, 1999|THOMAS H. MAUGH II

Comedians have had great fun commenting on proposed Federal Aviation Administration rules that would create "peanut-free zones" on aircraft, but peanut allergies are a severe problem. An estimated 0.5% to 1% of Americans are allergic to peanuts, according to the American Academy of Allergy, Asthma and Immunology, and violent reactions to peanuts account for most of the 125 deaths every year from food allergies.

The only treatment for peanut allergies now is complete avoidance of exposure, but authorities estimate that half of all cases of severe reactions result from accidental exposure, such as breathing in dust from a peanut bag opened by someone else.

But researchers at Johns Hopkins University may be on the road to developing a vaccine against peanut allergies. They took the gene in peanuts that is thought to be most responsible for severe reactions and combined it with chitosan, a product from crab shells that is often used for controlling drug delivery. They then ground the mixture into very small particles and fed it to mice specially bred to be allergic to peanuts.

Dr. Kam Leong and his colleagues reported in Tuesday's Nature Medicine that when the mice thus immunized were later exposed to the protein produced from the gene, they showed only a mild immune reaction. Untreated mice, in contrast, showed classic anaphylactic (allergic) shock and many died.

Technique Aids Fight Against Deadly Bacteria

It may be possible also to use a new technique to immunize against Pseudomonas aeruginosa and other bacteria that cause most infections among hospitalized patients, UC San Francisco researchers report in the same issue of Nature Medicine. P. aeruginosa is also responsible for the untreatable lung infections that devastate the lives of half a million people with cystic fibrosis.

Such bacteria now kill half the people they infect in hospitals. More than $2 billion per year is spent treating such infections, but control is difficult because the bacteria are becoming resistant to commonly used antibiotics.

UCSF microbiologist Dara W. Frank and her colleagues focused on a network of 25 proteins that are used by the bacteria to invade lung cells and inject deadly toxins. These toxins wipe out the cells' primary line of defense--the white blood cells called macrophages that would normally engulf and destroy the bacteria.

Frank's team made antibodies against five proteins involved in the invasion and tested each separately in mice. They found that antibodies against one of the proteins, called the PcrV antigen, prevented the bacteria from destroying the lung cell's macrophages. They are now developing antibodies to PcrV antigen that can be tested in humans.

Panel Lists Vaccines Worth Investing In

Increased funding for vaccines against cytomegalovirus, group B streptococcus and streptococcal pneumonia would provide the most benefit for the money, according to an Institute of Medicine report to be released this week. "These are the ones we really want society to invest in," said Dr. Robert Lawrence of Johns Hopkins University.

Cytomegalovirus is so common that nearly everyone is exposed at some point in their lives, but about 5,000 infected newborns every year suffer severe complications, including retardation and even death. A vaccine could be developed in seven years at a cost of $360 million, according to the report.

Group B streptococcus also is a problem in newborns, affecting one in every 500. About 10% of victims die and as many as 50% suffer neurologic damage. A vaccine could be completed in seven years at a cost of $400 million.

Better vaccines against streptococcal pneumonia could decrease the incidence of meningitis and ear infections in the newborn at a cost of about $240 million.

Other useful vaccines, the panel said, would target Helicobacter pylori, which causes ulcers; hepatitis C, which destroys the liver; and human papillomavirus, which cause cervical cancer.

Tumor-Fighting Ability of Green Tea Identified

Green tea has been hailed as a potential cancer fighter, and now some researchers believe they know why. A team from the Karolinska Institutet in Stockholm reported in Thursday's Nature that green tea contains chemicals that block the formation of blood vessels needed by tumors to grow.

Angiogenesis inhibitors, which block blood vessel recruitment by tumors, have been a hot topic for the last couple of years because of reports that some can cure cancer in mice. Several candidate drugs are already being tested in humans.

The Karolinska team found that the angiogenesis inhibitor in green tea is a chemical called epigallocatechin-2-gallate. They also found in mice that a diet of green tea blocked the spread of lung tumors. They said that the mice were given the human equivalent of two to three cups of tea per day, but cautioned that the tea would have to be consumed over long periods to be effective.

'Hot' Protein Could Aid in Pain Relief

UC San Francisco scientists have pinpointed a protein that responds to the hottest temperature nerve cells can tolerate, a finding that could lead to the development of new drugs to control pain.

The same team had earlier discovered the receptor protein that enables people to detect the heat in chili peppers. They reported in Thursday's Nature that the newly discovered protein in humans is tuned to respond to 120 degrees Fahrenheit and higher. It is part of a wide range of receptors that detect temperatures.

The hot protein, known as VRL-1, is found on sensory nerves, but pharmacologist David Julius and his colleagues turned up evidence that it is also present in the brain, spinal cord, spleen and intestines, indicating it responds to more than just temperature.

"The number of targets to relieve pain is limited. Any discovery of a receptor for extreme temperatures or other noxious stimuli broadens the range of targets for which you can develop candidate drugs," Julius said.

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