Virus Like Particles Present New Allergy Treatment Option

The rapid growth of severe allergies and anaphylaxis in populations around the world has triggered efforts to find faster, safer and more effective cures than conventional immunotherapy.

Now, a new review of existing research suggests that virus-like particles (VLPs) might be used to vaccinate many people against allergic reactions without exposing them to any actual allergens.

“Omitting the allergen from the vaccine would strike two birds with one stone,” the review authors wrote in Current Treatment Options in Allergy. “First, this would make immunotherapy safer by avoiding allergic adverse events. Second, one vaccine could be used for all allergies.”

Conventional immunotherapy typically requires patients who are allergic to particular compounds to expose themselves to slowly increasing doses of that compound over the course of 3 to 5 years. Serious reactions such as anaphylaxis are rare, but they do occur, and mild side effects such as itching are common.

Immunotherapy is usually effective in ameliorating or even eliminating allergies among patients who have the patience to follow protocol religiously over such a long period, but the rigors of treatment are such that less than 5% of all people with allergies ever start immunotherapy and far fewer complete it.

Even fewer people with allergies have completed treatment with VLP vaccinations, of course, but VLPs are widely used to make vaccinations against hepatitis C and human papilloma virus. They have, moreover, produced promising results in several trials on patients with allergies.

In one randomized, double-blind, placebo-controlled phase 2 study, 25 adult patients with allergic rhinitis from ragweed received a total of 6 weekly injections of a vaccine that included VLPs and the allergen. The patients did not achieve the primary trial endpoint: vascular permeability as measured by the serum albumin concentration in nasal lavage. They did, however, experience far fewer symptoms and report significantly higher quality-of-life scores for the 2 years between their injections and the end of trial follow-up.

Another study, a phase 2b trial on 229 adults with serious dust mite allergies, randomized patients to 6 weekly injections of either placebo or a VLP-based vaccination that contained no trace of dust mites. The treatment proved to be safe and well tolerated. Symptom and medication scores improved significantly in the treatment group, confirming that treatment with VLPs filled with nonmethylated CG motifs (CpGs) could ameliorate allergic rhinitis, even without injection of allergen.

The rationale for using VLPs to train the immune system’s response to allergens differs little from the rationale for using viruses to train its response to other conditions.

“The human immune system has evolved to efficiently recognize highly repetitive structures, because such structures are typically found on the surfaces of viruses and bacteria,” the review authors wrote. “To speed up the antibody response, such repetitive arrays of epitopes can crosslink such large numbers of B cell surface receptors that antibody production is induced even in the absence of T cell help.”

The review authors had several theories to explain why allergen-free vaccinations had proven so effective in the few trial that have been performed to date, but said that considerably more research would be needed to confirm any of the theories and, more importantly, to discover how broadly the mechanism would work against different types of allergies.

The potential advantages of VLP-based vaccinations — particularly a generalized vaccination with no allergens — justify an aggressive course of research, the review authors wrote.