Wednesday, May 2, 2012

Lymph node immunotherapy may be simpler, safer

A new, improved method of immunotherapy is emerging: injection of modified allergen, directly to the lymph node--which promises to prevent allergy to specific triggers with only a few treatments and minimal risk.

A group of Swiss, German, and Swedish scientists reports in the latest issue of the Journal of Allergy and Clinical Immunology that they reduced nasal tolerance of cat dander, a major trigger for atopic allergy, by a factor of 74 in a group of 20 subjects, using only three injections over two months. That means it took 74 times as much dander to cause the same amount of allergic reaction--the scientists used the flow of liquid from the nose as their measure--in a treated person as in a subject given placebo.

[This article featured in JACI's Journal Club.]

Immunotherapy for specific allergens currently requires 30 to 80 injections over three to five years and includes a risk of anaphylactic reaction. It is not popular. The new method, if confirmed, looks much more practical.

The researchers, Gabriela Senti of University Hospital Zurich and colleagues, were basically repeating an earlier, successful study that they had done with grass pollen. (I consider cat allergy avoidable but grass pollen is a big deal--you can't get away from it, unless you're in Antarctica.)

But the new study came with a twist--the researchers modified the cat dander allergen with two molecular changes. The first added a short chain of amino acids that helped the allergen enter the cell membrane--essentially, the membrane of B and T cells, since it was injected into the lymph nodes. This seems to have prevented other white blood cells, such as macrophages and mast cells, from encountering the allergen and provoking inflammation.

The second modification ensured that the allergen didn't get immediately destroyed inside the cells, but instead got chopped up and presented on the surface of antigen-presenting cells, which are a key element of the antibody arm of the immune system. Thus, by a process I don't really understand, your immune system becomes "tolerant" to that allergen.

Treatment with the modified cat allergen did not increase IgE antibody levels, or induce any "adverse events" in the treated group, which, it has to be said, numbered only 12. It's possible that in a larger test group some problems might reveal themselves.

If an environmental allergy is a big problem for your eczema, and you can stand nurses injecting things into your lymph nodes, this looks like good news. I don't know how long it might be until the FDA approves this treatment in the US though.

No comments:

Post a Comment