Clinical and immunologic effects of component peptides in Allervax Cat

On Peptides and Altered Peptide Ligands: From Origin, Mode of Action and Design to Clinical Application (Immunotherapy)

T lymphocytes equipped with clonotypic T cell antigen receptors (TCR) recognize immunogenic peptides only when presented in the context of their own major histocompatibility complex (MHC) molecules. Peptide loading to MHC molecules occurs in intracellular compartments (ER for class I and MIIC for class II molecules) and relies on the interaction of the respective peptides and peptide binding pockets on MHC molecules. Those peptide residues not engaged in MHC binding point towards the TCR screening for possible peptide MHC complex binding partners. Natural or intentional modification of both MHC binding registers and TCR interacting residues of peptides - leading to the formation of altered peptide ligands (APLs) - might alter the way peptides interact with TCRs and hence influence subsequent T cell activation events, and consequently T cell effector functions. This review article summarizes how APLs were detected and first described, current concepts of how APLs modify T cellular signaling, which biological mechanisms might force the generation of APLs in vivo, and how peptides and APLs might be used for the benefit of patients suffering from allergic or autoimmune diseases.

Advances in synthetic peptide immuno-regulatory epitopes

Synthetic peptide immuno-regulatory epitopes (SPIRE) represent a new class of therapeutics for allergen immunotherapy that offer the potential to suppress the IgE-mediated allergic disease process through induction of T-cell tolerance. These synthetic T-cell-tolerizing peptides have been designed to induce immunologic tolerance via binding to MHC class II molecules on antigen presenting cells, with subsequent upregulation of regulatory T-cells.

Cat peptide antigen desensitisation for treating cat allergic rhinoconjunctivitis

INTRODUCTION

Allergic rhinoconjunctivitis is an increasingly common source of morbidity with sensitivity to cats accounting for 10-15% of the disease burden. Allergy to cats is a major risk factor for the development of asthma.

AREAS COVERED

Within the present manuscript, the current data on a novel therapeutic approach to treat cat allergy is reviewed. Cat Peptide Antigen Desensitisation (Cat-PAD) is a mixture of seven small peptides developed for the treatment of cat allergy. It is designed to induce immunological tolerance via binding to MHC class II on antigen presenting cells and interacting with regulatory T cells without triggering the cross-linking of IgE on mast cells and basophils. The peptide sequences are derived from the major cat allergen Fel d 1. The peptides have been selected to ensure a similar T cell response to that generated to whole cat dander in ex-vivo PBMC derived from cat allergic individuals. The size of the peptides is insufficient to induce cross-linking of IgE. Clinical data from a series of studies shows that Cat-PAD is able to significantly reduce allergic rhinoconjunctivitis symptoms after a short course of four injections over 12 weeks, and that the treatment effect is persistent lasting 2 years after the start of treatment.

EXPERT OPINION

Taken together Cat-PAD is a novel, well tolerated and promising therapeutic approach to treat cat allergic patients. Data from the current international Phase III study will unravel whether the concept is also efficient and tolerable under daily life circumstances.

Prospects for a vaccine in allergic diseases and asthma

Allergen-specific immunotherapy is widely used to treat allergic diseases, and current research is now focusing on the development of therapeutic vaccines acting on the IgE immune response following allergen challenge. The IgE immune response is dependent on genetic and environmental factors; production of IgE results from complex interactions among B cells, T cells, mast cells, basophils,surface and adhesion molecules and various cytokines. New vaccination methods under investigation involve allergen-specific or nonspecific methodology. Allergen-specific methods currently being developed include allergoids, passive saturation of effector cells, plasmid DNA immunisation and antigen-antibody complexes. The mechanisms of immunotherapy using allergen-specific methods differ with the allergens and the route of immunisation used (parenteral, intranasal, sublingual, oral or bronchial). Many vaccines being developed at present comprise synthetic, recombinant or highly purified subunit antigens, which although they have increased safety may also be less immunogenic.It is hoped that the addition of adjuvants will overcome this drawback. Methods of increasing the dose of allergen while reducing the possibility of an anaphylactic reaction include the use of non-anaphylactic isoforms of the allergens, alteration of the tertiary structure of the allergens and construction of minimal allergen-derived T cell peptides. Nonspecific approaches include humanised anti-IgE antibodies,moderation of the T(H)2 cytokine network and antisense oligodeoxynucleotide therapy.

Epitope-specific T-cell responses and allergic phenotypes: implications for T-cell peptide therapy

In the 1990s, elucidation of the primary amino acid sequence of several major allergens using molecular cloning techniques opened the door to T-cell epitope mapping studies. Such analyses underscored the complexity of the allergen-specific T-cell repertoire and the challenges to using allergen-derived peptides to identify epitope-specific differences associated with allergic and nonallergic responses. This review highlights important factors that may influence the nature of epitope-specific T-cell responses observed in vitro. These include the properties of the allergen, genetics of the host and selection of patients with defined allergic phenotypes based on serum antibody profiles and skin test reactivity. By taking these factors into account, T-cell epitope-specific differences associated with distinct allergic phenotypes can be identified. Observations at the T-cell epitope level undermine the Th1/Th2 paradigm as a model for the development of allergic versus nonallergic responses. Instead, they support the mounting data that point to a network of interactions between T helper cells and regulatory T cells, which controls the allergic response. The ability of peptides that localize to polypeptide chain 2 of the major cat allergen, Fel d 1, to preferentially induce interleukin-10 and interferon-gamma is discussed. Mechanisms whereby specific allergen-derived peptides may modify the T-cell repertoire and influence the immune outcome are also outlined. Further investigation of allergen-derived T-cell epitopes is warranted in order to optimize the design of peptide vaccines for the treatment of allergic disease.

Antigen-specific tolerogenic and immunomodulatory strategies for the treatment of autoimmune arthritis

OBJECTIVES

To review various antigen-specific tolerogenic and immunomodulatory approaches for arthritis in animal models and patients in regard to their efficacy, mechanisms of action, and limitations.

METHODS

We reviewed the published literature in Medline (PubMed) on the induction of antigen-specific tolerance and its effect on autoimmune arthritis, as well as the recent work on B-cell-mediated tolerance from our laboratory. The prominent key words used in different combinations included arthritis, autoimmunity, immunotherapy, innate immunity, tolerance, treatment, and rheumatoid arthritis (RA). Although this search spanned the years 1975 to 2007, the majority of the short-listed articles belonged to the period 1990 to 2007. The relevant primary as well as cross-referenced articles were then collected from links within PubMed and reviewed.

RESULTS

Antigen-specific tolerance has been successful in the prevention and/or treatment of arthritis in animal models. The administration of soluble native antigen or an altered peptide ligand intravenously, orally, or nasally, and the delivery of the DNA encoding a particular antigen by gene therapy have been the mainstay of immunomodulation. Recently, the methods for in vitro expansion of CD4+CD25+ regulatory T-cells have been optimized. Furthermore, interleukin-17 has emerged as a promising new therapeutic target in arthritis. However, in RA patients, non-antigen-specific therapeutic approaches have been much more successful than antigen-specific tolerogenic regimens.

CONCLUSION

An antigen-specific treatment against autoimmune arthritis is still elusive. However, insights into newly emerging mechanisms of disease pathogenesis provide hope for the development of effective and safe immunotherapeutic strategies in the near future.

Use of altered peptide ligands to modulate immune responses as a possible immunotherapy for allergies

Allergies are dramatically increasing in prevalence, and the management of these diseases is a heavy burden on the health-care systems of developed countries. In recent years, many efforts have been made to improve the therapy of allergies and to develop new approaches for immunotherapy. Here we briefly review the use of peptides to modulate T-cell responses to allergens. We focus mainly on the possibility of using altered peptide ligands (APLs), i.e., peptides tailored on immunodominant T epitopes and bearing a single amino-acid substitution, as a tool to modulate immune responses to allergens. These peptides may be recognized by the specific T cells triggered by the agonist peptides, but they are unable to elicit T-cell responses; thus, they could be ideal candidates to modulate immune responses to allergens. The availability of these peptides could allow new approaches for immunotherapies.

Antigen-specific T cell tolerance down-regulates mast cell responses in vivo

Fel d I is the major cat allergen that induces asthma and allergic rhinitis in humans. To investigate the mechanism of allergic responses to this allergen, a mouse model was developed. Mice sensitized to chain 1 of Fel d I exhibited T cell responses, B cell responses, and mast cell responses when challenged with the protein. Subcutaneous injections of peptides containing the dominant T cell epitopes of the allergen induced T cell tolerance in presensitized mice. When challenged with the allergen intratracheally, these tolerized mice produced a decreased amount of histamine in vivo. The decrease in histamine release was not solely dependent on the reduction of allergen-specific IgE. These data show that mast cell activity in mice with an ongoing sensitivity to allergen can be regulated through peptide-induced T cell tolerance.

Fungal allergens and peptide epitopes

Fungal allergens represent a major cause of atopic disorders. Immunochemical and molecular characterization of fungal allergens has been hampered by the lack of pure proteins and to inherent variation among fungal proteins and in their poor yields. With the advent of molecular biology techniques, a number of allergens have been cloned, sequenced, and expressed from a variety of fungal species. The knowledge of the primary, secondary, and tertiary structures of these allergens, the immunodominant regions of these proteins, and their interaction with T and B-cell epitopes, results in better understanding of the molecular mechanisms of allergy and may provide avenues of immunologic intervention to treat patients. The present review deals with the current understanding of fungal allergen epitopes.

Mutant derivatives of the main respiratory allergen of cow are less allergenic than the intact molecule

BACKGROUND

Allergen immunotherapy offers an alternative for drug treatment in the management of allergic diseases. Because immunotherapy often induces side-effects, less allergenic preparations would be beneficial.

OBJECTIVE

The purpose of this study was to examine whether the allergenicity of a cow-derived lipocalin allergen, Bos d 2, could be diminished by substituting or deleting carboxy-terminal amino acids including the cysteine which forms a disulphide bond with a cysteine inside the molecule.

METHODS

Four recombinant mutants of Bos d 2 were created by substituting or deleting the four most carboxy-terminal amino acids. The immunological characteristics of the mutant preparations were compared with the unmodified rBos d 2 by Western blotting, ELISA inhibition, skin prick tests, and the proliferative responses of allergen-specific T-cell clones.

RESULTS

In Western blot, one of the two monoclonal antibodies showed reduced binding to the preparations without the terminal cysteine. In contrast, the other monoclonal antibody, human IgE and rabbit immune serum bound equally well to all the preparations. ELISA inhibition analyses revealed, however, that the preparations without the terminal cysteine bound antibody less efficiently. They were needed 15-38 times more than the unmodified rBos d 2 to cause the same level of inhibition. Surprisingly, one of the mutants with the terminal cysteine but a mutated adjacent amino acid turned out to be the weakest in inducing skin reactivity. All the preparations stimulated well allergen-specific T-cell clones.

CONCLUSIONS

The results show that the allergenicity of a lipocalin allergen, Bos d 2, can be diminished by modifying the carboxy-terminal end of the molecule. Modifications in the area which encompasses a disulphide bond impaired the antibody binding without affecting the T-cell stimulatory capacity. It was also shown that in vivo tests are necessary for determining the allergenicity of a modified allergen.

Genetically engineered and synthetic allergen derivatives: candidates for vaccination against type I allergy

Type I allergy, a hypersensitivity disease affecting almost 20% of the population worldwide, is based on the IgE recognition of otherwise harmless antigens (i.e., allergens). Allergen-induced crosslink of effector cell-bound IgE antibodies leads to the release of biological mediators and thus to immediate disease symptoms (allergic rhinitis, conjunctivitis and asthma). Specific immunotherapy, the only causative treatment of Type I allergy, is based on the administration of increasing doses of allergens to allergic patients in order to yield allergen-specific non-responsiveness. Major disadvantages are 1. that current forms of allergen immunotherapy are performed with allergens difficult to standardize which cannot be matched to the patients reactivity profile and 2. that the administration of active allergen preparations can cause anaphylactic side effects. Through the application of molecular biological techniques many relevant environmental allergens have been produced as active recombinant proteins which allow component-resolved allergy diagnosis and thus represent the basis for patient-tailored forms of immunotherapy. Here we review molecular strategies which have been recently applied to generate genetically engineered and synthetic hypoallergenic allergen derivatives for patient-tailored and safe vaccination against Type I allergy.

“Allergen Engineering”: Variants of the Timothy Grass Pollen Allergen Phl p 5b with Reduced IgE-Binding Capacity but Conserved T Cell Reactivity

One problem of conventional allergen-specific immunotherapy is the risk of anaphylactic reactions. A new approach to make immunotherapy safer and more efficient might be the application of engineered allergens with reduced IgE-binding capacity but retained T cell reactivity. Using overlapping dodeca-peptides, the dominant T cell epitopes of the timothy grass pollen allergen Phl p 5b were identified. By site-directed mutagenesis outside these regions, point and deletion mutants were generated. Allergen variants were analyzed for IgE-binding capacity with sera of different grass pollen allergic patients by Western blotting, Dot blotting, and EAST inhibition test, and for histamine releasing capacity with peripheral blood basophils from different patients. The deletion mutants revealed significantly reduced IgE reactivity and histamine releasing capacity, compared with the wild-type Phl p 5b. Furthermore, in vivo skin prick tests showed that the deletion mutants had a significantly lower potency to induce cutaneous reactions than the wild-type Phl p 5b. On the other hand, T cell clones and T cell lines from different allergic patients showed comparable proliferation after stimulation with allergen variants and wild-type Phl p 5b. Considering their reduced anaphylactogenic potential together with their conserved T cell reactivity, the engineered allergens could be important tools for efficient and safe allergen-specific immunotherapy.

Hyposensitization to allergic reaction in rDer f 2-sensitized mice by the intranasal administration of a mutant of rDer f 2, C8/119S

C8/119S is a mutant of recombinant Der f 2 (rDer f 2), and lacks a disulphide bond possessed by wild-type rDer f 2. In humans and mice, C8/119S has a very weak IgE-binding capacity compared with the wild-type, but possesses a T cell reactivity comparable to that of the wild-type. C8/119S may thus be a safe immunotherapeutic agent for house dust mite allergy. The aim of the present study was to evaluate whether the intranasal administration of C8/119S could suppress an immediate allergic reaction in mice sensitized with wild-type rDer f 2, possessing an allergic activity comparable to native counterparts purified from mite extract. Seven-week-old male A/J mice were immunized with wild-type rDer f 2 four times, and then intranasally administered 0.2-2 microg of wild-type, 0.2-20 microg of C8/119S, or PBS alone, three times a week for 4 weeks. Seven days after the last administration, the mice were examined for an immediate allergic reaction. The animals administered 2 microg of C8/119S (C2.0 group) showed significantly reduced immediate bronchoconstriction provoked by the i.v. injection of 1 and 10 microg of wild-type rDer f 2, compared with the PBS-treated mice. Similar results were obtained when we examined mice 10 weeks after the last administration. The reactions in the other groups given wild-type or C8/119S also tended to decrease in severity in comparison with the animals of the PBS group. The allergic phenotypes of the T cells, B cells, and basophils in the C2.0 group were shifted to that of naive mice without immunization. We conclude that C8/119S has hyposensitizing activities in mice sensitized with wild-type rDer f 2. C8/119S may be useful for immunotherapy of house dust mite allergy.

T Cell Epitopes in Japanese Cedar (Cryptomeria japonica) Pollen Allergens: Choice of Major T Cell Epitopes in Cry j 1 and Cry j 2 Toward Design of the Peptide-Based Immunotherapeutics for the Management of Japanese Cedar Pollinosis

Japanese cedar pollinosis is caused by exposure to Japanese cedar (Cryptomeria japonica) pollen, of which two components, Cry j 1 and Cry j 2, are believed to be the major allergens. T cell lines specific to either Cry j 1 or rCry j 2 were reactive to various portions of each panel of overlapping peptides derived from Cry j 1 or Cry j 2. Two peptides, p211–225 and p108–120, from among six major T cell epitopes identified in Cry j 1 sequence, and three peptides, p182–200, p344–355, and p66–80, from among five in Cry j 2, were chosen to design an artificial polypeptide (named Cry-consensus) based on a difference among the types of the restriction molecules capable of presenting these peptides. After construction of a DNA encoding these peptides in order, Cry-consensus was expressed in Escherichia coli. Five of six T cell epitopes, except for Cry j 2 p344–355, in Cry-consensus were recognized by the T cell clones specific to each peptide. PBMC from allergic patients induced higher proliferation under stimulation from Cry-consensus than individual peptides. Eighty-eight percent of the PBMC (15 of 17) showed proliferation under the Cry-consensus stimulation. Thus, several major T cell epitopes from Cry j 1 and Cry j 2 can be chosen in the design of peptide-based immunotherapeutics for the management of Japanese cedar pollinosis in subjects having various types of HLA class II molecules.

Molecular and crystal properties of Bos d 2, an allergenic protein of the lipocalin family

The relationship between the molecular structure of allergenic proteins and the allergenic determinants is one of the central issues in allergology. We report here that the natural preparation of Bos d 2, a mammalian lipocalin allergen, comprises three molecular variant proteins of 17,829, 17,781, and 17,800 Da. When cDNA of Bos d 2 (Genome Sequence Data Base No. L42867) was recloned and expressed in Pichia pastoris, two proteins were produced. One of the proteins (17,831 Da) and the proteins in the natural preparation had pyroglutamate as the N-terminal residue; in the other (17,849 Da) the N-terminal residue was glutamine. Recombinant Bos d 2 protein was crystallized and the native data set was collected at 1.8 A resolution.

Recombinant allergens

A great variety of recombinant plant, mite, mold, mammal, and insect allergens have been expressed in heterologous hosts (e.g., Escherichia coli), their cDNA being used as a template. The number of biologically active recombinant allergens available for experimental, diagnostic, and therapeutic purposes is increasing tremendously. Recombinant allergens have proven to be valuable tools to investigate T-cell and B-cell recognition of allergens as well as to study mechanisms of specific IgE regulation. The immunologic equivalence of many relevant recombinant allergens with their natural counterparts has been demonstrated, and the three-dimensional structures of several recombinant allergens have been described recently. As a result of extensive cross-reactivities among the relevant allergens, it appears that the number of epitopes needed for diagnosis and specific immunotherapy is less diverse than originally anticipated and might be soon covered by recombinant molecules. Recombinant allergens have been used for successful in vitro, as well as in vivo, allergy diagnosis, and work is in progress to produce recombinant allergen derivatives with reduced anaphylactic potential to improve current forms of immunotherapy.