Alexander Kettner

Allergen‐derived long peptide immunotherapy down‐regulates specific IgE response and protects from anaphylaxis

To evaluate a long peptide‐based allergy vaccine in a murine model, CBA/J mice were sensitized with low dose alum‐adsorbed phospholipase A2 (PLA2), a major bee venom allergen. Presensitized mice were treated by daily i.p. injections of a mixture of three long overlapping peptides (44‐ to 60‐mer) spanning the entire PLA2 molecule (100 μ g/peptide) for 6 consecutive days. This therapeutic approach induced a sharp drop in PLA2‐specific IgE, an increase in specific IgG2a, and a marked T cell hyporesponsiveness. T cell cytokine secretion was characterized by a shift from a Th2 to a Th1 profile. Prophylactic treatment of naive mice with long peptides prior to sensitization with PLA2 induced a comparable modulation of B and T cell responses. Upon i.p. challenge with native PLA2, presensitized mice treated with the long peptide mixture were fully protected from anaphylaxis. This indicated that allergen‐derived long overlapping peptides were safe and able to modulate an established Th2 response or to prevent its development. Furthermore, long peptide‐based immunotherapy provided clinical protection against anaphylaxis, thus appearing as a promising approach of the therapy of allergic diseases.

Inducing Tolerance by Intranasal Administration of Long Peptides in Naive and Primed CBA/J Mice

To assess the capacity of a peptide-based immunotherapy to induce systemic tolerance via the nasal route, we designed three long overlapping peptides of 44–60 aa covering the entire sequence of phospholipase A2 (PLA2), a major bee venom allergen. Both prophylactic and therapeutic intranasal administrations of long peptides to PLA2-hypersensitive CBA/J mice induced specific T cell tolerance to the native allergen. In prophylactic conditions, this tolerance was marked by a suppression of subsequent specific IgE response, whereas the therapeutic approach in presensitized mice induced a more than 60% decrease in PLA2-specific IgE. This decline was associated with a shift in the cytokine response toward a Th1 profile, as demonstrated by decreased PLA2-specific IgG1 and enhanced IgG2a levels, and by a decline in the specific IL-4/IFN-γ ratios. T cell transfer from long peptide-tolerized mice to naive animals abrogated the expected anti-PLA2 IgE and IgG1 Ab response, as well as specific T cell proliferation, but enhanced specific IgG2a response upon sensitization with PLA2. These events were strongly suggestive of a clonal anergy affecting more profoundly Th2 than the Th1 subsets. In conclusion, these results demonstrate that allergen-derived long peptides delivered via the nasal mucosa may offer an alternative to immunotherapy with native allergens without the inherent risk of systemic anaphylactic reactions. Moreover, long peptides, in contrast to immunotherapy strategies based on short peptides, have the advantage of covering all potential T cell epitopes, and may represent novel and safe tools for the therapy of allergic diseases.

Modulation of T-cell response to phospholipase A2 and phospholipase A2–derived peptides by conventional bee venom immunotherapy

BACKGROUND Immunologic mechanisms of desensitization are still incompletely understood. Safer methods of immunotherapy with reduced risks of anaphylaxis need to be developed. OBJECTIVE To study the effects of conventional venom immunotherapy (VIT) on phospholipase A2(PLA2)-specific T cells and on T-cell reactivity to short and long synthetic peptides that map the PLA2 molecule. METHOD Proliferation of a CD4+ cell-enriched peripheral blood mononuclear cell fraction and cytokine secretion by T cell lines from patients hypersensitive to bee venom and undergoing VIT in response to PLA2 and PLA2 synthetic peptides were measured. RESULTS T-cell proliferation in response to three synthetic peptides, 40 to 60 amino acids long and mapping the entire PLA2 molecule with an overlap of 10 residues (1 to 59, 51 to 99, and 90 to 134) steadily increased during the first 14 weeks of VIT corresponding to the treatment period with incremental doses of antigen. These results are in contrast to the low proliferation indices obtained with short (15 amino acid-long) peptides, and the inability to characterize the immunodominant region of the molecule with short peptides. At the end of VIT (after 3 to 5 years), there was correspondingly, a marked decrease in T cell responsiveness to PLA2 and to its long synthetic peptides. This response was paralleled by a shift in the pattern of cytokine secretion by T cell lines from a T(H0)-type to a T(H1)-type pattern. CONCLUSION After a transient increase in T-cell proliferation, late VIT was characterized by T-cell hyporesponsiveness to allergen and by modulation of cytokine secretion from a T(H0)-type to a T(H1)-type pattern. Because of their capacity to recruit multiple T-cell epitopes, long peptides mapping the entire PLA2 molecule appear to be efficient T cell stimulators and may represent potential candidates for peptide immunotherapy.

Delineation of PLA2 epitopes using short or long overlapping synthetic peptides: interest for specific immunotherapy

Background Venom immunotherapy is definitely indicated in severe systemic anaphylactic reactions to bee stings. but is not devoided of risks of anaphylaxis. Safer methods of Immunotherapy need to be developed.

In vivo kinetics of the immunoglobulin E response to allergen: bystander effect of coimmunization and relationship with anaphylaxis

Background Murine models of hypersensitivity to allergens are useful tools for the evaluation of preclinical strategies to down‐regulate the IgE response.

Benefit of Bet v 1 contiguous overlapping peptide immunotherapy persists during first follow-up season

A short course of 5 injection AIT with Bet v 1 Contiguous Overlapping Peptides was well tolerated and improved allergic rhinitis during the 2nd pollen season after treatment. Long lasting efficacy was associated with a persistent allergen-specific IgG4 response.