Experimental vaccine prevents dangerous allergic attack for a year

Mice can be protected from the life-threatening allergic reaction anaphylaxis for at least a year using an experimental vaccine. The hope is that it will work in humans too.

The threat of anaphylaxis constantly hangs over hundreds of millions of people globally, with allergies to foods like peanuts or shellfish one common risk factor. In the UK, for example, around 6 per cent of adults – or 2.4 million people – are estimated to have a clinically confirmed food allergy.

Eating contaminated food, or even kissing someone who has recently eaten a food that makes you react, can cause a spike in molecules produced by the immune system called immunoglobulin E (IgE) antibodies, leading to swelling of the tongue or throat, difficulty breathing and a drop in blood pressure. This can result in a hospital visit – even if you have an adrenaline auto-injector like an EpiPen on hand to reverse the symptoms. In severe cases, anaphylaxis can be fatal.

Aside from attempting to avoid the allergen, options to prevent such attacks are limited. You can try oral immunotherapy, which involves consuming small, gradually increasing amounts of an allergenic food under supervision to build tolerance, or take a drug called an anti-IgE monoclonal antibody, such as omalizumab, which binds to IgE, stopping it from causing a reaction. But omalizumab is expensive and needs to be injected every few weeks, potentially for life.

Now, Laurent Reber at the Toulouse Institute for Infectious and Inflammatory Diseases, France, and his colleagues have developed a vaccine named IgE-K. This primes the immune system to produce antibodies that target IgE, preventing it from binding to its receptors on immune cells, and halting a subsequent runaway allergic reaction.

“We wanted to come up with a solution that could be long-term, because when you are food allergic, you can be exposed anytime by accident, so you really want to be protected all the time,” says Reber.

In tests on mice modified to produce a human version of IgE, the researchers found that two doses of the vaccine induced the mice to generate neutralising antibodies against IgE.

“It blocks up the molecule that makes us allergic,” says Josh Koenig at McMaster University in Ontario, Canada.

The researchers then gave the mice a substance that would cause an allergic reaction. Unvaccinated mice had a strong reaction, but vaccinated ones were protected against anaphylaxis for as long as a year without showing any adverse effects.

“It could be longer, but we haven’t tested longer,” says Reber.

IgE is part of the body’s immune system, and as well as generating allergic reactions, it fires up in response to venoms and some intestinal parasites. “It’s probably an ancestral system that helps fight against toxins,” says Reber.

Reber says many people at risk of serious allergic reactions have received anti-IgE therapies for years without discontinuation and experienced no ill-effects, so there is good evidence that it is safe to target the molecule long-term. But to see whether dampening down IgE could reduce the body’s effectiveness at fighting parasites, the researchers did an additional experiment in mice. They found that the vaccine didn’t impair the immune response to an infection by Strongyloides ratti, a parasitic nematode worm.

Koenig is optimistic that such a vaccine would be effective in people. “They know that the mouse made the antibody that bound up the human IgE molecule properly. If humans make that same molecule, then I think there’s a pretty high chance that this will work out quite nicely.”

Still, clinical trials are needed to evaluate the vaccine’s safety, efficacy and duration in humans, says Reber. If it does come to market, he thinks it could be a cost-effective way to treat people with severe allergies because it would require far fewer injections than an anti-IgE monoclonal antibody like omalizumab.