Conjugation of immunostimulatory DNA to the short ragweed allergen Amb a 1enhances its immunogenicity and reduces its allergenicity

Background: Allergen immunotherapy is inconvenient and associated with the risk of anaphylaxis. Efforts to improve the safety of immunotherapy by mean s of chemical modification of allergens have not been successful because it greatly reduced their antigenicity. Recently, immunostimulatory DNA sequen ces (ISS or CpG motifs) have been shown to act as strong T(H)1 response-ind ucing adjuvants. Objective: We sought to determine whether conjugation of ISS to the major s hort ragweed allergen Amb a 1 results in enhanced immunotherapeutic potenti al in mice and decreased allergenicity in human subjects. Methods: A 22-mer ISS oligodeoxynucleotide (ISS-ODN) was coupled to Amb a 1 and used for immunization of mice, rabbits, and monkeys. Results: In mice the Amb a I-ISS conjugate induced a T(H)1 response (IFN-ga mma secretion), whereas Amb a 1 induced a T(H)2 response (IL-5 secretion). The T(H)1 response was not observed with an Amb a I-non-ISS conjugate. Coin jection of Amb a 1 with ISS-ODN was much less effective in inducing a T(H)1 response. In mice primed for a T(H)2 response, injection with Amb a I-ISS conjugate induced a de novo T(H)1 response and suppressed IgE antibody form ation after challenge with Amb a 1. Amb a 1-ISS conjugate induced high-tite r anti-Amb al IgG antibodies in rabbits and cynomolgus monkeys, whereas Amb a 1 alone or Amb a 1 coinjected with ISS-ODN did not induce a detectable r esponse. Amb a I-ISS conjugate was less allergenic than Amb a 1 alone, as s hown by a 30-fold lower histamine release from human basophils of patients with ragweed allergy, whereas mixing ISS-ODN with Amb a 1 did not reduce hi stamine release. Conclusion: Amb a 1-ISS conjugate has an enhanced T(H)1-biased immunogenici ty and reduced allergenicity. It may offer a more effective and safer appro ach for allergen immunotherapy than currently available methods.