Adipokines and sublingual immunotherapy: preliminary report

Mechanisms of Allergen Immunotherapy and Potential Biomarkers for Clinical Evaluation

Allergen-immunotherapy (AIT) is an efficacious and disease-modifying treatment option for IgE-mediated diseases. Among these allergic rhinitis, insect venom allergy, food allergy, and allergic asthma are the most common candidates for AIT. AIT gives rise to clinical immunotolerance which may last for years after the treatment cessation. Mechanisms of AIT include suppression of allergic inflammation in target tissues and stimulation of the production of blocking antibodies, especially IgG4 and IgA. These mechanisms are followed by a reduction of underlying allergen-specific Th2 cell-driven responses to the allergens. Tolerance induction takes place through the desensitization of effector cells and stimulation of regulatory T cells that show their effects by mechanisms involving cell-cell cross-talk, but also other mechanisms, e.g., by the production of immunomodulatory cytokines such as, e.g., IL-10 and TGF-beta. From a personalized medical perspective, there is a need for clinical biomarkers of value in selecting responders and optimizing patient care during AIT. Also, a deeper understanding of underlying mechanistic processes will improve AIT's future outcomes. In this paper, the current knowledge of mechanisms in AIT is reviewed with a special focus on biomarkers of this therapy.

Biomarkers for monitoring clinical efficacy of allergen immunotherapy for allergic rhinoconjunctivitis and allergic asthma: an EAACI Position Paper

BACKGROUND

Allergen immunotherapy (AIT) is an effective treatment for allergic rhinoconjunctivitis (AR) with or without asthma. It is important to note that due to the complex interaction between patient, allergy triggers, symptomatology and vaccines used for AIT, some patients do not respond optimally to the treatment. Furthermore, there are no validated or generally accepted candidate biomarkers that are predictive of the clinical response to AIT. Clinical management of patients receiving AIT and efficacy in randomised controlled trials for drug development could be enhanced by predictive biomarkers.

METHOD

The EAACI taskforce reviewed all candidate biomarkers used in clinical trials of AR patients with/without asthma in a literature review. Biomarkers were grouped into seven domains: (i) IgE (total IgE, specific IgE and sIgE/Total IgE ratio), (ii) IgG-subclasses (sIgG1, sIgG4 including SIgE/IgG4 ratio), (iii) Serum inhibitory activity for IgE (IgE-FAB and IgE-BF), (iv) Basophil activation, (v) Cytokines and Chemokines, (vi) Cellular markers (T regulatory cells, B regulatory cells and dendritic cells) and (vii) In vivo biomarkers (including provocation tests?).

RESULTS

All biomarkers were reviewed in the light of their potential advantages as well as their respective drawbacks. Unmet needs and specific recommendations on all seven domains were addressed.

CONCLUSIONS

It is recommended to explore the use of allergen-specific IgG4 as a biomarker for compliance. sIgE/tIgE and IgE-FAB are considered as potential surrogate candidate biomarkers. Cytokine/chemokines and cellular reponses provided insight into the mechanisms of AIT. More studies for confirmation and interpretation of the possible association with the clinical response to AIT are needed.

The expression of adiponectin receptor is altered in mild and moderate/severe persistent allergic nasal mucosa

BACKGROUND

Adiponectin, one of the adipokines, has been implicated in the inflammatory process in patients with allergic rhinitis. The level of adiponectin is affected by immunotherapy. Considering the fact that adiponectin receptors (AdipoRs) mediate intracellular signaling events in response to the binding of adiponectin, the role of AdipoRs in healthy and allergic nasal mucosa should be determined. This study investigates the level of expression and distribution pattern of AdipoR1 and AdipoR2 in healthy, mild, and moderate/severe persistent allergic nasal mucosa to understand the role of adiponectin in allergic rhinitis.

METHODS

The level of expression and distribution pattern of AdipoR1 and AdipoR2 were evaluated in healthy, mild, and moderate/severe persistent allergic nasal mucosa, using semiquantitative reverse-transcriptase-polymerase chain reaction (RT-PCR), immunohistochemistry, and Western blot analysis.

RESULTS

AdipoR1 was expressed in healthy, mild, and moderate/severe persistent allergic nasal mucosa where it was commonly localized to the vascular endothelium. However, AdipoR2 was not expressed in any samples of nasal mucosa tested in the present study. Semiquantitative RT-PCR and Western blot analysis showed that the level of expression of AdipoR1 mRNA and protein was decreased in mild and moderate/severe persistent allergic nasal mucosa in comparison with healthy nasal mucosa, but not significantly different between mild and moderate/severe persistent allergic nasal mucosa.

CONCLUSION

These results indicate that AdipoR1 may play an important role in the pathogenesis of allergic nasal mucosa, suggesting a role for AdipoR1 in vascular dysfunction in mild and moderate/severe persistent allergic nasal mucosa.

Antigen-specific immunotherapy against allergic rhinitis: the state of the art

Allergic rhinitis is the most prevalent type I allergy in industrialized countries. Pollen scattering from trees or grasses often induces seasonal allergic rhinitis, which is known as pollinosis or hay fever. The causative pollen differs across different areas and times of the year. Impaired performance due to pollinosis and/or medication used for treating pollinosis is considered to be an important reason for the loss of concentration and productivity in the workplace. Antigen-specific immunotherapy is an only available curative treatment against allergic rhinitis. Subcutaneous injection of allergens with or without adjuvant has been commonly used as an immunotherapy; however, recently, sublingual administration has come to be considered a safer and convenient alternative administration route of allergens. In this review, we focus on the safety and protocol of subcutaneous and sublingual immunotherapy against seasonal allergic rhinitis. We also describe an approach to selecting allergens for the vaccine so as to avoid secondary sensitization and adverse events. The biomarkers and therapeutic mechanisms for immunotherapy are not fully understood. We discuss the therapeutic biomarkers that are correlated with the improvement of clinical symptoms brought about by immunotherapy as well as the involvement of Tr1 and regulatory T cells in the therapeutic mechanisms. Finally, we focus on the current immunotherapeutic approach to treating Japanese cedar pollinosis, the most prevalent pollinosis in Japan, including sublingual immunotherapy with standardized extract, a transgenic rice-based edible vaccine, and an immunoregulatory liposome encapsulating recombinant fusion protein.

Serum adipsin levels in patients with seasonal allergic rhinitis: preliminary data

BACKGROUND

Several studies have outlined a possible relationship between adipokines and respiratory allergic diseases. However, there are no data about a role for adipsin in allergic rhinitis.

OBJECTIVE

The aim of the study was to evaluate the serum adipsin levels in patients with seasonal allergic rhinitis (SAR), subdivided into two sub-groups: treated or not treated with sublingual immunotherapy (SLIT), and in a group of healthy controls.

METHODS

The study included 110 subjects; i) 24 SLIT-treated SAR patients, ii) 62 untreated SAR patients, and iii) 24 normal subjects. All subjects were consecutively evaluated. A skin prick test and blood sampling for assessing serum adipsin levels were performed in all subjects.

RESULTS

Serum adipsin was increased in SAR patients, even though significant only in males. There was also a significant positive association between adipsin and adiponectin.

CONCLUSION

This preliminary study reports that adipsin serum levels may be increased in some SAR patients, but further functional studies should be performed.

Two year sublingual immunotherapy affects serum leptin

BACKGROUND

It has been demonstrated that serum leptin is elevated in females with allergic rhinitis. Recently, it has been reported that one course of sublingual immunotherapy (SLIT) does not affect serum leptin levels.

OBJECTIVE

The aim of this study was to evaluate the serum leptin levels in a cohort of patients with pollen-induced allergic rhinitis, before and after two pre-seasonal SLIT courses.

METHODS

Forty-one patients (22 males and 19 females, median age 39 years) with AR, due to pollen allergy, and 34 healthy subjects (16 males and 18 females, median age 43 years) were included in the study. Blood sampling for assessing serum leptin was performed in all subjects before and after the second SLIT course.

RESULTS

All patients were responders to SLIT. Serum leptin was significantly increased only in males (p=0.0056) after the second SLIT course.

CONCLUSION

This preliminary study shows that at least two pre-seasonal SLIT courses were required to induce significant modifications in serum leptin levels, but it occurred only in males. Some hypotheses might be outlined, including a leptin protective effect, however further studies must clarify this issue.