Immunological mechanisms of specific immunotherapy with pollen vaccines: implications for diagnostics and the development of improved vaccination strategies

Modern approaches to therapeutic vaccination as treatment for Type 1 respiratory hypersensitivity (allergy) treatment

The incidence of respiratory and other allergies has increased dramatically in many countries over the last few decades. Drug treatment is symptomatic and has a minimal effect on the underlying immunological dysfunction. This disease process may, however, be modified by allergy vaccination, which is typically applied by injecting increasing strengths of the offending allergens. Its use has been fairly limited owing to long injection schedules involving many visits to the physician, occasional local or systemic side effects, perceived limited efficacy and poor compliance. A greater understanding of the immunological mechanisms involved in allergy vaccination has led recently to the development of new generations of products with properties that address some of these issues, and these advances are likely to increase the successful use of the therapy.

Tolerability and clinical efficacy of oral immunotherapy with house dust mites in a model of canine atopic dermatitis: a pilot study

Atopic dermatitis (AD) is a chronic, life-long disease. In humans, immunotherapy (IT) is the only treatment that can alter the course of AD. Oral IT is appealing owing to the ease of administration and the potential for increased compliance. The purposes of this study were to investigate the tolerability, clinical efficacy and effects on allergen-specific IgE of oral IT using a canine AD model. Thirteen atopic beagles sensitized to house dust mites (HDMs) were randomly divided into two groups. One group received daily oral doses of HDMs while the other group received vehicle only for 7 months. The investigator evaluating the dogs was blinded to the allocation of treatments. Prior to and after 2 and 7 months of IT, dogs were challenged daily with HDMs for 3 days concurrently, and clinical signs were scored using a modified Canine Atopic Dermatitis Extent and Severity Index (CADESI). Prior to and at completion of oral IT, serum was collected for measurement of allergen-specific IgE. Oral IT was well tolerated, and no adverse effects were noted. Analysis of variance showed no significant effect of time, group and group × time interaction for CADESI scores. In addition, there were no significant differences in allergen-specific IgE levels. In conclusion, it appears that oral administration of HDMs is well tolerated in these atopic beagles but that this protocol was not sufficient to induce clinical improvement. Further, longer-term studies will be necessary to explore the potential of oral IT in veterinary medicine.

Engineering of major house dust mite allergens Der p 1 and Der p 2 for allergen-specific immunotherapy

BACKGROUND

Specifically designed recombinant allergens with reduced IgE reactivity are promising candidates for a more defined, effective, and safer specific immunotherapy (SIT).

OBJECTIVE

We sought to obtain hypoallergenic hybrid molecules which could potentially be applied to house dust mite (HDM) allergy treatment.

METHODS

Two hybrid molecules (QM1 and QM2) derived from the two major Dermatophagoides pteronyssinus allergens, Der p 1 and Der p 2, were engineered by PCR, produced in Escherichia coli, and purified. The overall IgE-binding capacity of the hybrids was compared with their single components by Western blot, specific IgE, skin prick test (SPT), and IgE-inhibition assays. T cell proliferation assay were performed to confirm their retention of T cell reactivity. Immune responses to the hybrid molecules were studied in BALB/c mice.

RESULTS

The IgE reactivity of both hybrid proteins was strongly reduced as evaluated by in vitro methods. Furthermore, in vivo SPTs performed on 106 HDM-allergic patients showed that the hybrid proteins had a significantly lower potency to induce cutaneous reactions than the individual components. Hybrid molecules induced higher T cell proliferation responses than those produced by an equimolecular mixture of Der p 1 and Der p 2. Immunization of mice with the hybrid proteins induced Der p 1- and Der p 2-specific IgG, which inhibited the binding of allergic patients' IgE to these natural allergens.

CONCLUSION

QM1 and QM2 hybrids exhibited less IgE-binding activity but preserved immunogenicity and fulfilled the basic requirements for hypoallergenic molecules suitable for a future SIT of HDM allergy.