New allergy vaccine brings relief to rats.

New allergy vaccine brings relief to rats

An experimental vaccine blocks allergic reactions in rats and shows promise as a novel treatment for humans, British immunologists report. But other researchers express concern that the vaccine's design rests on an unconfirmed theory of immune function.

Denis R. Stanworth and his colleagues at the University of Birmingham, England, hold a controversial view of the immunological events that culminate in allergic reactions. They agree with other scientists that allergens -- substances to which individuals are allergic -- cause circulating immune proteins called IgE to bind to mast cells in body tissues. The mast cells then secrete histamine and other potent chemicals that create the itching, sneezing and watery eyes characteristic of allergic reactions.

But Stanworth's team believes that another critical event must occur between these two steps: A subunit of the cellbound IgEprotein must stick to another molecule elsewhere on the mast cell. The new vaccine consists of a chemically synthesized version of this IgE "trigger" subunit. Rats vaccinated with a dose of the subunit create antibodies that block allergic reactions, presumably by interfering with this middle step, the researchers report in the Nov. 24 LANCET.

In their experiments, five of six vaccinated rats allergic to egg white showed no signs of allergic reaction after receiving challenge doses of the egg protein. In contrast, two of four unvaccinated rats died of severe allergic reactions following the egg-white challenge, and the other two showed serious signs of allergic distress, including difficult breathing. Blood histamine levels were significantly lower in the vaccinated group.

"The method is based upon a rather shaky hypothesis, and even in the context of this hypothesis it remains rather confusing just how it is working," comments Henry Metzger, an immunologist at the National Institutes of Health in Bethesda, Md., who is investigating alternative means of blocking IgE's effects. Still, he says, "if one way or another these antibodies are doing what they report, then it may be promising."

"We might be wrong about how this thing works, but it's damn effective," Stanworth argues. "We think we have the makings of a novel vaccine for use in humans." He notes that a vaccine that blocks the IgE response should, in theory, prove useful for virtually any allergy, precluding the need to identify the culprit allergen.

Immunologist Philip W. Askenase of Yale University calls the work "interesting." However, he adds, "this is not something that's going right to the bedside."