Bolus injection of aqueous antigen leads to a high density of T-cell-receptor ligand in the spleen, transient T-cell activation and anergy induction.

In vivo anergy can be modelled by administration of soluble peptide to T-cell receptor (TCR) transgenic mice specific for the moth cytochrome c peptide 88-103 (MCCp). Two weeks after initial peptide treatment, T cells were present in normal numbers but were unresponsive to antigen stimulation in vitro. Only bolus injections of peptide, either subcutaneous or intravenous, were effective at inducing tolerance, while slowly released antigen administered via mini-osmotic pump failed to result in anergy. Examination of T cells soon after bolus peptide administration revealed that anergy induction was preceded by a transient hyperactivation of T cells in vivo. Within 2 hr of peptide treatment, interleukin-2 was detectable in the plasma of the transgenic mice. Interestingly, only bolus injections of peptide led to high levels of T-cell activation, while adjuvant emulsified and pump-administered peptide resulted in very low stimulation in vivo. When the dose of bolus-injected peptide used for tolerization was titrated, the extent of anergy induction directly correlated with the intensity of early T-cell activation. Indirect measurements of TCR-ligand density on the surface of antigen-presenting cells following peptide administration revealed that aqueous peptide delivered via bolus injection generated a large number of major histocompatibility complex-peptide complexes, while pump-delivered and adjuvant-emulsified peptide did not. These data suggest that high levels of TCR ligand are required for in vivo T-cell hyperactivation and induction of anergy.

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.

Peripheral tolerance in T cell receptor-transgenic mice: evidence for T cell anergy.

T cell tolerance can be induced in adult mice by injection of soluble antigenic peptide. The underlying mechanism has been difficult to establish in normal mice due to the low precursor frequency of T cells specific for any given antigen. Therefore, we examined peripheral tolerance in mice transgenic for a T cell receptor specific for a cytochrome c peptide bound to I-Ek. Antigen-specific hyporesponsiveness could be induced in the transgenic mice. We followed the transgene-bearing T cells with a clonotypic monoclonal antibody and found similar numbers of clonotypic T cells in tolerized and control mice. To prevent de novo differentiation of T cells we analyzed thymectomized mice in which antigen-specific hyporesponsiveness was induced. Our analysis of thymectomized transgenic mice showed that antigen-specific T cell hyporesponsiveness following injection of peptide intravenously is not caused by gross elimination of T cells. These data provide evidence for the role of anergy in peripheral tolerance.

Peripheral T-cell tolerance induced in naive and primed mice by subcutaneous injection of peptides from the major cat allergen Fel d I.

T cells control the majority of antigen-specific immune responses. Therefore, influencing the activation of the T-cell response in order to modify immune responsiveness is an obvious therapeutic goal. We have used a mouse model of response to Fel d I, the major cat protein allergen in humans, to explore the ability of peptides derived from Fel d I to inhibit T-cell-dependent immune responses to the peptides themselves and to larger polypeptides. T cells from B6CBAF1 mice respond to the Fel d I peptide IPC-2 after challenge with IPC-2. However, subcutaneous tolerization with IPC-2 prevents this response as measured by production of interleukins 2 and 4 and interferon gamma. Fel d I immunization of B6D2F1 mice results in T-cell responses primarily to one peptide derived from Fel d I. Injecting this peptide in soluble form inhibits T-cell activation (as measured by interleukin 2 production) and antibody production in Fel d I-primed animals when they are subsequently challenged with peptide in adjuvant. Most of the cat-allergic human T-cell response to Fel d I is specific for two peptides on one of its two chains. Immunization of B6CBAF1 mice with recombinant Fel d I chain 1 results in T-cell responses to the same peptides. Subcutaneous administration of these two peptides, which contain some, but not all, of the T-cell epitopes from Fel d I chain I, decreases the T-cell response to the entire recombinant Fel d I chain 1. The ability to tolerize T-cell responses with subcutaneous injections suggests a practical approach to treating human diseases with peptides containing T-cell epitopes.

Multiple Amb a I allergens demonstrate specific reactivity with IgE and T cells from ragweed-allergic patients.

The relationship between the structure and abundance of an inhaled protein and its potential for causing an allergic response is unknown. This study analyzes Amb a I, a family of related proteins formerly known as Ag E, that comprise the major allergens of short ragweed (Ambrosia artemisiifolia). T cells isolated from ragweed allergic patients were shown to proliferate in response to purified Amb a I.1 protein from pollen in in vitro secondary cultures, demonstrating the presence of T cell stimulatory epitopes in Amb a I.1. Three recombinant forms of Amb a I (Amb a I.1, Amb a I.2, and Amb a I.3) obtained as cDNA derived from pollen mRNA were expressed in bacteria. All three recombinant forms were shown to be specifically recognized by pooled ragweed-allergic human IgE on immunoblots, confirming these gene products are important allergens. An examination of immunoblots probed with sera derived from allergic patients revealed a variation in IgE binding specificity. A minority of patients' IgE exclusively reacted with recombinant Amb a I.1, whereas most patients' IgE reacted with Amb a I.1 as well as Amb a I.2 and Amb a I.3 proteins. A detailed examination of the reactivity of T cells derived from 12 allergic patients to these recombinant Amb a I forms revealed that these allergens are all capable of stimulating T cell proliferation in in vitro assays. It is concluded that the allergic response to ragweed pollen in most allergic patients is composed of a reaction to multiple related Amb a I proteins at both the B and T cell levels.

Genetic recombination in the alpha 2 domain of the E alpha chain yields an Ed molecule with altered T cell activation.

We have used a novel T cell selection strategy to isolate a mutant of an H-2d/f murine macrophage line defective in its ability to present antigen to some Ed-restricted helper T cells. This mutant has an amino acid substitution in the alpha 2 domain of the Ed molecule. The mutation changes the sequence at codon 177 from ACC to CAC, which results in a threonine to histidine substitution and appears to be the first in vitro mutation to have arisen by genetic recombination. Even though the mutation is distal to the proposed antigen-binding groove, it affects antigen presentation, presumably by altering the scaffolding for the antigen-binding groove. This type of mutant might not be readily isolated using other selection techniques.

Murine MHC polymorphism and T cell specificities.

The major histocompatibility complex (MHC) genes are polymorphic in mouse and man. The products of these genes are receptors for peptides, which while bound, are displayed to T lymphocytes. When bound peptides from antigens are recognized by T lymphocytes, an immune response is initiated against the antigens. This study assessed the relation of the polymorphic MHC molecules to their peptide specificity. The results indicate that although an individual of the species has a limited ability to recognize antigens, the species as a whole has broad reactivity. This rationalizes the extreme polymorphism observed.

T cell receptor gene usage in the response to lambda repressor cI protein. An apparent bias in the usage of a V alpha gene element.

The T cell response to the lambda repressor cI protein is directed to the same region of the protein (residues 12-26) in both BALB/c and A/J mice. A panel of T cell hybridomas specific for P12-26 in the context of either I-Ek or I-Ad have been isolated To further understand the molecular interaction between the TCR and the Ia-P12-26 complex, the primary structures of the TCR of five T cell hybridomas have been determined. Southern and Northern analyses indicate that two members of the V alpha 3 gene family are used by 13 out of 14 I-Ek-restricted T cells. Four different V beta genes are used by these T cell hybridomas, while the majority (8 out of 13) express V beta 1 in combination with the J beta 2.1 element. No clear correlation can be seen in this system between gene usage and MHC restriction. In addition, the fine specificity of I-Ek-restricted T cells to a single amino acid substitution [Phe22/His22]P12-26 is not attributed to the usage of particular V alpha and V beta elements. The V alpha 3 family gene is also used by a few I-Ad-restricted T cells. Interestingly, these I-Ad T cells share a reactivity pattern more similar to that of I-Ek-restricted T cells than other I-Ad-restricted T cells. The nonrandom selection V alpha 3 is also demonstrated by the fact that V alpha 3 is used by P12-26-specific, but not by cytochrome c- or staphylococcal nucleus-specific, I-Ek-restricted T cells. This suggests that although antigen specificity may not be accounted for by either chain of the TCR, the members of V alpha 3 genes may be selected by the antigen (P12-26).

T lymphocyte response to bacteriophage lambda repressor cI protein. Recognition of the same peptide presented by Ia molecules of different haplotypes.

The murine T cell response to bacteriophage lambda cI repressor protein has been investigated. Isolation and characterization of class II-restricted T cell hybridomas from BALB/c and A/J mice undergoing a primary response has revealed that a single region of the protein, residues 12-26, is the immunodominant site. Fine specificity analysis using truncated peptides (P12-24 and P15-26) reveals a great deal of heterogeneity at the clonal level of I-Ad-restricted T cells. I-Ek-restricted T cells are less heterogeneous in their reactivity toward P12-24 and P15-26, but show diversity in their responses to peptide analogues with substitution at Tyr22. The specificity difference between T cell hybridomas of I-Ad-restriction and I-Ek-restriction and the inhibition effect of different inactive peptides suggest that the same peptide is presented in different configurations by different Ia molecules. Further, no cross-reactivity can be detected between T cells of these two haplotypes, Ia molecules and Ia bound-peptides.

Immunological self, nonself discrimination.

The ability of immunodominant peptides derived from several antigen systems to compete with each other for T cell activation was studied. Only peptides restricted by a given transplantation antigen are mutually competitive. There is a correlation between haplotype restriction, ability to bind to the appropriate transplantation antigen, and ability to inhibit activation of other T cells restricted by the same transplantation antigen. An exception was noted in that a peptide derived from an antigen, bacteriophage lambda cI repressor, binds to the I-Ed molecule in a specific way, yet is not I-Ed-restricted. Comparison of the sequence of the repressor peptide with that of other peptides able to bind to (and be restricted by) I-Ed and a polymorphic region of the I-Ed molecule itself revealed a significant degree of homology. Thus, peptides restricted by a given class II molecule appear to be homologous to a portion of the class II molecule itself. The repressor-derived peptide is identical at several polymorphic residues at this site, and this may account for the failure of I-Ed to act as a restriction element. Comparison of antigenic peptide sequences with transplantation antigen sequences suggests a model that provides a basis for explaining self, nonself discrimination as well as alloreactivity.

Interaction of peptide antigens and class II major histocompatibility complex antigens.

T lymphocytes require a foreign antigen to be presented on a cell surface in association with a self-transplantation antigen before they can recognize it effectively. This phenomenon is known as major histocompatibility complex (MHC) restriction. It is not clear how an incalculably large number of foreign proteins form unique complexes with a very limited number of MHC molecules. We studied the recognition properties of T cells specific for a peptide derived from bacteriophage lambda cI protein. Analogues of this peptide, as well as peptides derived from other unrelated antigens which can be presented in the context of the same MHC molecule, can competitively inhibit activation of these T cells by the cI peptide. Furthermore, these unrelated antigens can stimulate cI-specific T cells if certain specific amino-acid residues are replaced. Here we suggest a model in which all antigens give rise to peptides that can bind to the same site on the MHC molecule. T-cell recognition of this site (which is presumed to be polymorphic) with or without antigen bound can explain self-selection in the thymus and MHC restriction.

Cytolytic activity of antigen-specific T cells with helper phenotype.

We have investigated an unusual cytolytic activity displayed in vitro by cloned T cells which have the cell surface phenotype of helper T cells. When the cloned T cells are cultured with the appropriate antigen and antigen-presenting cells (APC), the T cells become activated in that they produce lymphokines and proliferate in an antigen-specific and major histocompatibility complex-restricted manner. At the same time, these T cells cause lysis of the APC. In addition, innocent non-histocompatible bystander cells present in the cultures can also be killed. The cytolytic activity may be involved in a mechanism of immune regulation.