Optimized conjugation ratios lead to allergen immunostimulatory oligodeoxynucleotide conjugates with retained immunogenicity and minimal anaphylactogenicity.

BACKGROUND: Immunotherapy has gradually fallen out of favor for the treatment of many allergic diseases because of the overall convenience, safety, and efficacy of medications. However, investigations suggest that allergen/immunostimulatory sequence oligodeoxynucleotide (ISS-ODN) conjugates (AICs) might have improved safety and efficacy compared with allergen extracts. OBJECTIVE: We determined whether changes in the ISS-ODN conjugation ratio would effect the immunogenicity and allergenicity of AIC. METHODS: Immunogenicity was determined by means of AIC vaccination of mice, followed by analysis of antigen-specific antibody and cytokine responses. The allergenicity of AIC was determined in mast cell release studies and in murine models of anaphylaxis and the Arthus reaction. RESULTS: AIC induced a stronger immune response than allergen alone or allergen mixed with ISS-ODN, but higher-level ISS-ODN conjugation reduced its immunogenicity modestly. In mast cell degranulation studies AIC was approximately 100-fold less allergenic than native allergen, with stepwise increases in the ODN conjugation ratio leading to stepwise decreases in allergenicity. In anaphylaxis studies death rates were reduced from 100% with native allergen challenge to as low as 0% with high-ratio ISS-ODN AIC challenge. Similar results were obtained in an Arthus reaction model. CONCLUSION: These investigations establish that AIC is both significantly more immunogenic and less allergenic than native allergens and the techniques used might have further utility for the standardization and optimization of AIC formulations for use in allergic patients.

DNA-based approaches to the treatment of allergies.

Although excellent pharmacological treatments for allergies exist, they do not change the underlying pathogenesis of allergic diseases and do not cure the disease. Only allergen-specific immunotherapy, the injection of small but increasing amounts of allergen, has been shown to change a pre-existing allergic Th2 immune response to a non-allergic Th1 response. However, since injection of allergen is associated with the risk of allergic and sometimes even life-threatening anaphylactic reactions, immunotherapy is no longer used as extensively as in the past. In the search for a novel immunotherapy having a low risk-to-benefit ratio, immunostimulatory CpG motif DNA sequences have recently been shown to provide an excellent tool for designing safer and more efficient forms of allergen immunotherapy. These DNA-based immunotherapeutics include allergen gene vaccines, immunization with allergen-DNA conjugates and immunomodulation with immunostimulatory oligodeoxynucleotides. All three DNA-based immunotherapeutics have been shown to be very effective in animal models of allergic diseases and, at present, allergen-DNA conjugates are being tested for their safety and efficacy in allergic patients. This review describes the preclinical findings and the data of the first clinical trials in allergic patients of DNA-based immunotherapeutics for allergic disorders.

Allergen-immunostimulatory oligodeoxynucleotide conjugate: a novel allergoid for immunotherapy.

PURPOSE OF REVIEW: To summarize the data of both preclinical studies and initial clinical trials of a novel allergoid for allergen specific immunotherapy. This allergoid consists of allergen covalently coupled to immunostimulatory oligodeoxynucleotide DNA sequences. RECENT FINDINGS: Recently, immunostimulatory oligodeoxynucleotide sequences, also called unmethylated cytosin-guanine dinucleotide motifs, have been discovered that act as strong T helper 1 response inducing adjuvants in mice. Although mixing allergens with immunostimulatory DNA sequences induces T helper 1 responses in T helper 2 biased mice, the allergens in such mixes could still cause anaphylactic reactions when used in humans which is one of the reasons why immunotherapy has gradually been falling out of favor. Therefore, we made allergen-immunostimulatory oligodeoxynucleotide conjugates and investigated their immunogenicity and allergenicity in animal models of allergy. These conjugates were highly immunogenic for inducing T helper 1-like antiallergen responses and reversed T helper 2 responses and symptoms of asthma in mouse models. They were also less allergenic, as shown by the reaction with human immunoglobulin E antibodies and by histamine release from basophils of allergic patients. Preliminary phase I and II trials in ragweed allergic patients showed that allergen-immunostimulatory oligodeoxynucleotide conjugates are well tolerated, less allergenic and induce immunoglobulin G antiallergen antibodies more rapidly than allergen extracts without significantly increasing the immunoglobulin E titer. SUMMARY: Allergen-immunostimulatory DNA conjugates induce T helper 1 and down regulate preexisting T helper 2 anti-allergen responses in mice. Initial phase I and II trials in ragweed allergic patients showed that ragweed allergen-DNA conjugates are well tolerated and induce a rapid immunoglobulin G but not E response. The data show that allergen-DNA conjugates are a novel type of allergoid that have great potential for a safe and potent form of allergen specific immunotherapy.

DNA-based vaccines for allergic disease.

Allergen-specific immunotherapy, although efficacious, is now less frequently used because of potential adverse reactions. Recently, two new types of allergen immunotherapy have been developed that appear to overcome this problem, namely allergen gene vaccination and vaccination with allergen-immunstimulatory DNA conjugates. In animal models of allergy, both have been shown to induce nonallergic T-helper cell type 1 immune responses to allergens and downregulate pre-existing T-helper cell type 2 responses. In initial clinical trials with allergic patients, allergen-immunostimulatory DNA conjugates were well-tolerated, induced immunoglobulin-G but not immunoglobulin-E antibodies and appeared to have great potential as a novel, safe and efficacious type of allergen specific immunotherapy.