Modified Recombinant Allergens for Safer Immunotherapy

Abstract

Molecular cloning and recombinant production of allergens offered new perspectives for the increasing problem of allergies. A variety of preparations are being developed aiming to increase safety and improve efficacy of specific immunotherapy. Recombinant-based approaches are mostly focused on genetic modification of allergens to produce molecules with reduced allergenic activity and conserved antigenicity, i.e. hypoallergens. Studies dealing with genetic modifications of allergen genes reported the production of site-directed mutants, deletion mutants, allergen fragments and oligomers, and allergen chimeras. An alternative to genetic engineering is the chemical modification of pure recombinant allergens. It has been shown that allergens modified with immunostimulatory DNA sequences (allergen-ISS conjugates), which masks IgE epitopes and adds a desirable Th1-inducing character to the allergen molecule. Other chemical modifications include oligomerization by aldehydes (allergoids) and maleylation, which seems to target allergens to particular antigen presenting cells. Several of these modified allergen preparations have been already evaluated for their safety in clinical provocation studies. So far, clinical trials showed the efficacy and safety of immunotherapy with an Amb a 1-ISS conjugate for ragweed pollen-allergic patients. In addition, a preparation consisting of hypoallergenic fragments of Bet v 1 was evaluated for immunotherapy of birch pollen-allergic patients. In parallel, several animal studies have now demonstrated the potential of genetic immunization for allergy treatment in the future.

Amino Acid Substitution in Par j 2 Recombinant Allergen and Its Effect on IgE Binding Capacity

“…There are several medicines on the market used for alleviating allergy symptoms, but they do not prevent the onset of the allergic reaction. Nowadays, with the use of modern biotechnologies and recombinant DNA, it is possible to isolate and structurally and immunologically characterize many allergens that, used in immunotherapy, could help diminish allergic reactions [2,[12][13][14]. Allergenic molecules can be modified in such way as to dissociate the useful components (the T linear epitopes) from the harmful ones (the IgEs B epitopes).…”

“…A further contribution to the allergic reaction derives from the recognition of the T epitopes, by allergens. These data together could be used in a therapeutic strategy as an alternative to the one cited above, based on the employment of modified allergens which are unable to bind to IgEs on the surface of the basophils but retain the ability to interact with the T cells [12].…”

Allergen Extract Analysis and Quality Control

“…The latter should ideally be prepared according to a patient-tailored approach, whereby only allergen components one given patient is sensitized to are administered (Vrtala, 2008). Although available allergen preparations do not allow this approach, yet numerous double-blind placebo-controlled studies using unmodified aqueous allergens (Gurka and Rocklin, 1988) and allergoids (Ferreira et al, 2006) (modified allergens) have demonstrated efficacy. Sublingual immunotherapy, using drops of aqueous allergen extracts under the tongue and then swallowed (Radulovic et al, 2010), or tablets (Bufe et al, 2009;Dahl et al, 2008) with similar type of extracts, also appear to be clinically beneficial, particularly for grass-induced rhinoconjunctivitis.…”

Proteomic analysis of Parietaria judaica pollen and allergen profiling by an immunoproteomic approach

“…2 Pie-chart representing the percentage distribution of identified pollen proteins within functional classes be responsible of the shifts in isoelectric points. At the same time, post-translational modifications might have an influence on the Ig binding so that the knowledge of the structure of allergens is important to improve diagnosis and therapy of allergy (Ferreira et al 2006). …”