Strain-dependent induction of allergic sensitization caused by peanut allergen DNA immunization in mice

To investigate the potential application of allergen gene immunization in t he modulation of food allergy, C3H/HeSn (C3H) mice received i.m. injections of pAra h2 plasmid DNA encoding one of the major peanut allergens, Ara h2, Three weeks following pDNA immunization, serum Ara h2-specific IgG2a, IgG1 , but not IgE, were increased significantly in a dose-dependent manner. IgG 1 was 30-fold higher in multiply compared with singly immunized mice, Ara h 2 or peanut protein injection of immunized mice induced anaphylactic reacti ons, which were more severe in multiply immunized mice, Heat-inactivated im mune serum induced passive cutaneous anaphylaxis, suggesting that anaphylax is in C3H mice was mediated by IgG1, IgG1 responses were also induced by in tradermal injection of pAra h2, and by i.m. injection of pOMC, the plasmid DNA encoding the major egg allergen protein, ovomucoid. To elucidate whethe r the pDNA immunization-induced anaphylaxis was a strain-dependent phenomen on, AKR/J and BALB/c mice also received multiple i.m. pAra h2 immunizations . Injection of peanut protein into these strains at weeks 3 or 5 following immunization did not induce reactions. Although IgG2a was increased signifi cantly from week 2 in AKR/J mice and from week 4 in BALB/c mice and remaine d elevated for at least 6 wk, no IgG1 or IgE was detected. These results in dicate that the type of immune responses to pDNA immunization in mice is st rain dependent. Consequently, models for studying human allergen gene immun ization require careful selection of suitable strains. In addition, this su ggests that similar interindividual variation is likely in humans.