Any new information on peanut vaccines?
Actually yes; and it seems to be very promising news. As you may recall from previous articles in this newsletter, the one FDA approved oral peanut vaccine is less than ideal: it causes a lot of side effects including occasional anaphylaxis and it confers very modest protection. But, a breath of fresh air came to peanut vaccine research based on astute observation by immunologists at Boston Children’s Hospital. They discovered a major difference in the stool microbiome of children with food allergies versus those without.
The non-allergic children had two “protective” bacteria Subdoligranulum variable and Clostridia species. Based on this discovery they did experiments in mice who were peanut allergic. Transferring these bacteria to the mice stopped the anaphylaxis they would otherwise have if given peanut. As it turns out the healthy bacteria stimulated a subset of immune cells called regulatory T cells (Treg’s). The Treg’s protect against allergic reactions.
With this exciting result they have moved forward to small clinical trials in children. (“small” in terms of number of participants, not because of the size of the patients). By adding the bacteria to the peanut protein in the oral peanut vaccine the patients did not experience allergic reactions from the vaccine and they developed good protective response.
In a second phase of the study, they gave a brief course of oral antibiotics targeted to killing bad colon bacteria and then the oral vaccine. This group had an even better protective response. The only bad news in all of this is that the Boston researchers couldn’t refrain from referring to their new vaccine as “Poop Pills”.
A peanut patch vaccine is the newest option being studied for children with severe allergy to
The two types of “vaccine” that have received the greatest study are oral immunotherapy (OIT), and
sublingual immune therapy (SLIT). Both approaches are flawed and thus have not been approved by the
Oral therapy provides the best results in terms of vaccine protection against peanut exposure, but it
has an intolerably high frequency of side effects. Sublingual therapy is less prone to side effects, but,
unfortunately, does not provide very good vaccine protection.
The new approach: epicutaneous immunotherapy (EPIT) seems to be the answer. It provides an
excellent level of protection with few side effects.
The peanut extract is administered by a patch worn on the skin. The dosage is gradually increased by
increasing the length of time the patch is in place.
The much-anticipated arrival of a vaccine for severe peanut allergy is still unfulfilled. There seem to be too many unresolved issues with the vaccines currently being tested — whether they be injectable or oral vaccines.
Safety concerns and avoidance of unwanted reactions are instrumental in this delay.
Enter nanoparticle technology. Perhaps because the amount of peanut protein used in nanoparticle vaccines is so small, there have been no severe reactions to the vaccine. Also, early studies show that the nano-vaccine provides as good protection from peanut allergy as the traditional mega-protein vaccine.
Exciting results are out from an eight-year study by the Harvard Medical School that questioned the outcomes of allergy in children if their mothers either avoided completely – or purposefully consumed – peanut, milk and wheat during pregnancy.
These three foods were chosen because they account for a large proportion of food allergies found in young children, and cause or contribute to asthma, eczema and allergic rhinitis. The study included 1,277 mother/child pairs.
The results were quite dramatic:
- Ingestion of peanut, especially during the first trimester, reduced the chance of peanut allergy by 47 percent!
- Daily milk intake during pregnancy, again especially in the first trimester, markedly reduced the risk for asthma and allergic rhinitis.
- Daily wheat intake, in both the first and second trimesters, significantly reduced the chance for the child developing eczema.
So, moms-to-be can relax a little. Based on their results, these Harvard researchers concluded that ingestion as indicated above of peanut, milk and wheat during pregnancy has a marked ability to reduce childhood allergies.
Dear Dr. K: Please give us an update on the vaccine for peanut allergy.
Your request is very timely as I recently finished reading a pro/con editorial in the journal Asthma and Allergy Proceedings. I think these two editorial viewpoints sum things up quite nicely. The first of the two is titled, “Oral and Sublingual Peanut Immunotherapy Is Not Ready for General Use.” In this article written by the director of allergy at the University of Michigan, the focus in on the high frequency of patients who experience symptoms from the oral vaccine – including anaphylaxis – which required use of epinephrine.
Analyzing five recently published trials on peanut vaccine revealed that in each study, more than one half of patients had some type of reaction as the vaccine was built up. The reactions led to some parents removing their children from the study. In the five protocols reviewed the drop-out rate varied from 5 to 25 percent.
The author points out that the vaccine works by two mechanisms: tolerance and desensitization. Tolerance occurs by depleting the allergic antibody (IgE) to peanut. To maintain the depletion, the vaccine must be continued daily. If the vaccine is stopped, tolerance also stops because IgE rebuilds itself.
Desensitization is what occurs with traditional allergy shots. It leads to an increase in protective IgG against peanut (called blocking antibody), and a decrease in IgE. This type of protection is more desirable and can persist even after the vaccine is stopped. The author points out that even though the vaccines do seem to elicit both modes of protection, no long-term study has been done to show how long-lasting the benefit is. Therefore, the author concludes that for now, the vaccine should be restricted to research protocols until the risk/benefit ratio is better understood and the long-term benefit is fully determined. The contrasting editorial is from the Paul Foster School of Medicine in El Paso, Texas, and is titled, “Oral Immunotherapy for Peanut Allergy in a Clinical Practice is Ready.” This author argues that the annual rate for accidental peanut ingestion is 10 percent which leads to severe symptoms, including anaphylaxis and the need for epinephrine. This number far exceeds the number of vaccine-induced reactions requiring epinephrine. He further argues that peanut allergy has a major effect on the quality of life of the patient and his/her family, and can be psychosocially debilitating. Also, unlike other food allergies where remission is high, less than 20 percent of peanut allergic children have spontaneous remission. Finally, he cites the outcome of three clinical trials done in office-based settings that treated a total of 150 children. Of these, 111 were successfully able to take the vaccine and were protected in a purposeful challenge of eight peanuts.
Sharp rise in peanut allergy emerges in study; strict preventive protections said justified
The recent Journal of Allergy and Clinical Immunology had a research paper from the University of Minnesota looking at peanut allergy. By means of a long-term study these scientists found a tripling of peanut allergy in children since 1999.
More than three-quarters of the peanut-allergic children in their study were under the age of 2. Also, 70 percent of the peanut allergy was in boys.
The scientists don’t know what accounts for this dramatic increase. One theory they are considering is low vitamin D levels. Remember, the population studied was in Minnesota. The researchers recommend active steps to create peanut-free environments, such as peanut bans on airplanes, peanut-free sections at baseball parks and “school safe” lunch programs.
They feel such severe measures are justifiable since peanut allergy reactions tend to be severe and even potentially life-threatening.
Food families have similar proteins and this can lead to cross-reactive allergy. That having been said, not all families have the same degree of cross-reactivity.
Peanut allergy is often severe but, luckily, has one of the lowest levels of cross-reactivity with other legumes. There is only a 5 percent risk of cross-reactivity for peanut with beans, peas and soybeans.
Cow-milk allergy is the highest (at 90 percent), with other mammals and milks from sheep and goat. Yet, people with cow-milk allergy almost never react to mare’s milk, donkey’s milk or dolphin’s milk.
Shellfish cross-reactivity is high at 75 percent. Thus if an individual is allergic to shrimp, he or she has a three in four chance of also being allergic to lobster, crabs or crawfish. This high degree of cross-reactivity is not true for non-crustacean shellfish such as clams and oysters.
Fish cross-reactivity is roughly 50 percent.
Tree nut allergy is about 35 percent cross-reactive across the board. However, certain nuts seem more closely linked. Pistachio is very similar to cashew, walnut to pecan and almond to hazelnut. Nut allergy does not translate to seed allergy such as sesame seed, but sesame, poppy and sunflower tend to be cross-reactive with one another.
On a practical level, if an individual with a specific food allergy has already tolerated other foods in the same family, that person should continue to be safe in eating these family-related foods. Still, foods in the same family that have not yet been tried should be considered suspect, and the individual may want to undergo allergy testing to determine the safety of the particular food.