Induction of Specific Th1 Responses and Suppression of IgE Antibody Formation by Vaccination with Plasmid DNA Encoding Cyn d 1

Background: DNA vaccines encoding allergens have been developed to prevent or to treat specific IgE responses. Objective: To evaluate the potential preventive and therapeutic effect of DNA vaccines encoding Cyn d 1 alone or combined with different adjuvants on specific allergies. Methods: Recombinant plasmid Cyn d 1 (pCyn d 1) was constructed by insertion of Cyn d 1 cDNA into the vector pcDNA3. BALB/c mice were injected with pCyn d 1 alone or plus adjuvants such as bupivacaine, bestatin, liposome, or CpG. Control mice were treated with pcDNA3 or PBS. They were boosted 3 weeks later and then sensitized twice with recombinant Cyn d 1 and alum. Their serum antibody responses and cytokine profiles of spleen cells were studied. Adoptive transfer of spleen cells of pCyn d 1-vaccinated mice was also performed. Results: Vaccination of mice with pCyn d 1 induced Th1 responses characterized by IgG2a responses and spleen cell secretion of interferon-γ. Vaccination with pCyn d 1 not only prevented the induction of specific IgE responses but also suppressed ongoing IgE responses. The mice receiving untreated, CD4+- or CD8+-depleted spleen cells from pCyn d 1-vaccinated mice all had suppression of IgE responses. Conclusion: This study confirms the prophylactic and therapeutic effects of DNA vaccines encoding Bermuda grass pollen allergen Cyn d 1 on specific IgE responses. Both CD4+ and CD8+ T cells are crucial for the immunomodulatory effect of pCyn d 1 on specific IgE responses.