Immunostimulatory DNA inhibits IL-4-dependent IgE synthesis by human B cells.

BACKGROUND: Immunostimulatory sequence oligodeoxynucleotide (ISS-ODN) is a potent antiallergic immunomodulating agent in mice. However, few studies have addressed its antiallergic potential in human subjects. OBJECTIVE: We sought to determine whether a phosphoro-thioate ISS-ODN could inhibit IL-4-dependent IgE synthesis by human B cells. METHODS: Initially, nonatopic- and atopic-donor PBMCs were incubated with ISS-ODN or mutated oligodeoxynucleotide, and cytokine production and B-cell expression of IFN-gamma receptor and IL-4 receptor were measured by using ELISA and flow cytometry, respectively. In subsequent studies atopic-donor PBMCs were incubated with IL-4 alone or with ISS-ODN or mutated oligodeoxynucleotide. After 14 days, IgE production and IgM, IgG, and IgA production were determined by using ELISA. In select IgE studies cytokines were neutralized with mAbs. RESULTS: ISS-ODN induced IL-12, IFN-alpha, IFN-gamma, IL-10, and IL-6 production from both nonatopic- and atopic-donor PBMCs. ISS-ODN also increased IFN-gamma receptor and inhibited IL-4 receptor expression on B cells from both donor populations. Furthermore, ISS-ODN inhibited IL-4-dependent IgE production by atopic-donor PBMCs. Neutralization of IL-12, IFN-alpha, IFN-gamma, and IL-10, but not IL-6, attenuated the inhibitory activity of ISS-ODN on IgE production. In contrast to its inhibition of IgE synthesis, ISS-ODN stimulated the production of IgM, IgG, and IgA. CONCLUSION: These in vitro studies demonstrate that phos-phorothioate ISS-ODN elicits an innate immune response by PBMCs, which inhibits IL-4-dependent IgE synthesis. In addition, these results provide further support for consideration of ISS-ODN therapy for the treatment of allergic disease in clinical practice.

DNA-based vaccination reduces the risk of lethal anaphylactic hypersensitivity in mice.

BACKGROUND: Anaphylactic hypersensitivity is the most serious clinical concern facing allergists. However, for the majority of anaphylactic hypersensitivities, avoidance is the only therapeutic option presently available. OBJECTIVE: This study evaluated the effectiveness of primary gene and protein-immunostimulatory DNA vaccination in the prevention of anaphylactic hypersensitivity in a murine model. METHODS: Female C3H/HeJ mice were immunized with a plasmid encoding beta-galactosidase (beta-gal) or beta-gal protein plus an immunostimulatory sequence oligodeoxynucleotide. The mice were then T(H2) sensitized to beta-gal by coinjection with alum and pertussis and then intravenously challenged with this model allergen. RESULTS: Primary gene and protein-immunostimulatory DNA vaccination of subsequently T(H2)-sensitized mice reduced the risk of death after anaphylactic challenge from 100% to 67% and 58%, respectively (P<.018 vs control mice). In addition, gene and protein-immunostimulatory DNA vaccination reduced postchallenge plasma histamine levels by greater than 4-fold (P <.05 vs control mice). Consistent with previous studies, these DNA-based vaccination strategies were further shown to blunt the development of T(H2)-biased immune responses after allergen sensitization. Vaccination with protein alone, the experimental equivalent of a traditional immunotherapy reagent, provided no protection from anaphylaxis nor did it prevent the development of a T(H2)-biased immune profile after allergen sensitization. CONCLUSION: The present series of experiments demonstrate that both gene vaccination and coimmunization with protein and immunostimulatory DNA are effective in attenuating the development of anaphylactic hypersensitivity in subsequently T(H2) sensitized mice.

Immunostimulatory DNA is a potent mucosal adjuvant.

Most proteins delivered to mucosal surfaces fail to induce mucosal or systemic immune responses. We demonstrate that a single intranasal (i.n.) coadministration of a model antigen (beta-galactosidase, beta-gal) with immunostimulatory sequence oligodeoxynucleotide (ISS-ODN) induces a mucosal IgA response equivalent to that induced by i.n. codelivery of beta-gal with cholera toxin (CT). Furthermore, i.n. and intradermal (i.d.) delivery of the beta-gal/ISS-ODN mix stimulates equivalent Th1-biased systemic immune responses with high-level cytotoxic T lymphocyte (CTL) activity. In contrast, i.n. immunization with beta-gal and CT results in a Th2-biased systemic immune response with poor CTL activity. Our data show that i.n. delivery of ISS-ODN provides effective adjuvant activity for the induction of both mucosal and systemic Th1-biased immune responses. This immunization approach deserves consideration in the development of vaccines against mucosal pathogens.

Immunostimulatory DNA sequences function as T helper-1-promoting adjuvants.

An adjuvant role for certain short bacterial immunostimulatory DNA sequences (ISSs) has recently been proposed on the basis of their ability to stimulate T helper-1 (Th1) responses in gene-vaccinated animals. We report here that noncoding, ISS-enriched plasmid DNAs or ISS oligonucleotides (ISS-ODNs) potently stimulate immune responses to coadministered antigens. The ISS-DNAs suppress IgE synthesis, but promote IgG and interferon-gamma (IFN-gamma) production. They furthermore initiate the production of IFN-gamma, IFN-alpha, IFN-beta, and interleukins 12 and 18, all of which foster Th1 responses and enhance cell-mediated immunity. Consideration should be given to adding noncoding DNA adjuvants to inactivated or subunit viral vaccines that, by themselves, provide only partial protection from infection.