Efficacy of a therapeutic cocaine vaccine in rodent models.

Cocaine abuse is a major medical and public health concern in the United States, with approximately 2.1 million people dependent on cocaine. Pharmacological approaches to the treatment of cocaine addiction have thus far been disappointing, and new therapies are urgently needed. This paper describes an immunological approach to cocaine addiction. Antibody therapy for neutralization of abused drugs has been described previously, including a recent paper demonstrating the induction of anti-cocaine antibodies. However, both the rapidity of entry of cocaine into the brain and the high doses of cocaine frequently encountered have created challenges for an antibody-based therapy. Here we demonstrate that antibodies are efficacious in an animal model of addiction. Intravenous cocaine self-administration in rats was inhibited by passive transfer of an anti-cocaine monoclonal antibody. To actively induce anti-cocaine antibodies, a cocaine vaccine was developed that generated a high-titer, long-lasting antibody response in mice. Immunized mice displayed a significant change in cocaine pharmacokinetics, with decreased levels of cocaine measured in the brain of immunized mice only 30 seconds after intravenous (i.v.) administration of cocaine. These data establish the feasibility of a therapeutic cocaine vaccine for the treatment of cocaine addiction.

A universal T cell epitope-containing peptide from hepatitis B surface antigen can enhance antibody specific for HIV gp120.

Peptide-based vaccines that directly target T cell or B cell epitopes may have significant advantages over conventional vaccines. Further, synthetic chimeric peptides that combine strong T cell epitopes with poorly immunogenic, but immunodominant, B cell epitopes or strain-conserved B cell epitopes may be useful in eliciting antibody to such important regions. Here we characterize a human T cell epitope analyzed in 54 individuals immunized with a hepatitis B virus surface Ag vaccine. Primary cultures from a total of 59 immunized donors were assessed for their ability to respond to hepatitis B virus surface Ag and peptides, and five were non-responders (8.5%). T cell lines were established from the remaining 54 responders. Of the responders, it was found that the peptide representing amino acids 19 through 33 (19-33) elicited significant proliferation in lines derived from 50 donors. This "universal" T cell epitope, which was recognized in donors of many different HLA-DR and -DQ haplotypes, was then used to construct a chimeric peptide containing 19-33 and the third V region loop structure (V3 loop) of HIV-1 envelope gp 120, in an attempt to augment the immune response to the V3 loop peptide. The V3 loop is the region to which significant neutralizing antibody is directed. Thus, a strong immune response to a synthetic peptide that contains the strain-conserved V3 loop region could have significant therapeutic implications. The V3 loop/19-33 peptide was then used to prime mice, to determine whether V3 loop-specific antibody could be induced. The peptide elicited potent 19-33-specific proliferation in T cells isolated from draining lymph nodes, and in six of six mice anti-V3 loop antibody was elicited. Further, V3 loop/19-33-primed animals made significant levels of antibody that bound rgp120. These data suggest that, when a major T cell epitope is synthesized in tandem with the V3 loop, a significant immune response against the loop can be elicited. Thus, given the finding that neutralizing antibody may play a role in the control and/or prevention of HIV infection, an HIV vaccine composed of a T cell epitope-containing peptide may prove effective. In addition, this type of approach can be generalized to the design of peptide-based vaccines.

The potential use of T cell epitopes to alter the immune response.

Recent advances in the understanding of T cell specificity and activation have lead to the design of T cell specific immunomodulators. T cell epitope containing peptides have been proposed as agents which may either enhance or dampen the immune response. In this review, we examine two systems which can benefit from the application of this novel technology. Vaccine development is moving toward the use of defined cloned or synthetic molecules. T cell epitope identification and design can be used to augment the ability of a weak antigen to generate an immune response. In contrast, traditional allergy immunotherapy has been shown to alter the immune response to the allergenic antigen. T cell epitope approaches to allergy desensitization offer a new therapeutic modality.

Two signals are required for accessory cells to induce B cell unresponsiveness. Tolerogenic Ig and prostaglandin.

We previously demonstrated that a lymphoid dendritic cell-like tumor line (P388AD.2) presented a normally tolerogenic signal, fluoresceinated sheep gamma-globulin (FL-SGG), as an immunogenic one. In contrast, macrophages derived from the peritoneal cavity potentiated the ability of FL-SGG to induce B cell unresponsiveness. In this paper we examined whether two different Ia+ splenic accessory cells differentially presented tolerogen to spleen cells or fluorescein (FL)-binding B cells. Interestingly, lymphoid dendritic cells presented FL-SGG to spleen cells and elicited augmented anti-FL antibody responses, whereas splenic macrophages presented this same moiety and elicited hapten-specific B cell unresponsiveness. The mechanism of splenic macrophage-elicited B cell negative signaling was investigated, and it was found that B cell unresponsiveness was abrogated in the presence of the cyclooxygenase inhibitor indomethacin. This observation suggested a crucial role for PG in B cell negative signaling. The addition of 10 nM PGE2 restored unresponsiveness in cultures treated with indomethacin and tolerogen-pulsed macrophages, even though this dose of PG had no effect on the ability of B cells to be triggered by an immunogenic signal. A role for T cells was excluded, inasmuch as purified hapten-specific B cells were specifically tolerized by FL-SGG-pulsed macrophages. Lymphoid dendritic cells pulsed with FL-SGG did not deliver a tolerogenic or immunogenic signal to FL-specific B cells. However, when PGE2 was supplied, B cell unresponsiveness was induced. Finally, we tested whether "non-tolerogenic" doses of FL-SGG could render hapten-specific B cells unresponsive in the presence of PGE2, but in the absence of accessory cells. Interestingly, the combination of non-tolerogenic amounts (10 to 1000 pg/ml) of FL-SGG in conjunction with PGE2 induced unresponsiveness, whereas neither moiety alone was effective. These results suggest that splenic macrophages and lymphoid dendritic cells exert opposing effects on the immune system as evidenced by the induction of negative or positive B cell signaling. Our observations suggest that one of the key factors in controlling whether an accessory cell delivers a tolerogenic signal is the ability to secrete PG.