Local nasal immunotherapy: experimental evidences and general considerations

30 years of sublingual immunotherapy

Allergen Immunotherapy (AIT) was introduced in clinical practice on an empirical basis more than 100 years ago. Since the first attempts, AIT was administered subcutaneously. Indeed, other routes of administration were proposed and studied, in particular to improve the safety, but only the sublingual route (SLIT) achieved a credibility based on evidence and was then accepted as a viable "alternative" option to the subcutaneous route. SLIT was largely used in clinical trials and clinical practice in this last 30 years. Thus, a large amount of data is available, coming from either controlled trials and postmarketing surveillance studies. It is clear that SLIT is overall effective, but it is also clear that the efficacy is not "class-related," as derived from meta-analyses, but restricted to each specific product. The 30-year lasting use of SLIT allowed to clarify many clinical aspects, such as efficacy, safety, use in asthma, regimens of administration, and optimal doses. In parallel, the mechanisms of action of AIT were elucidated, and new indications were proposed (eg food allergy, atopic dermatitis). In addition, the introduction of molecular-based diagnosis, allowed to better refine the prescription of SLIT, based on specific sensitization profiles. The present article will describe the origin and evolution of SLIT for respiratory allergy, taking into account the clinical context that suggested this form of treatment, the recently developed aspects, the future perspectives and unmet needs, This is not, therefore, a systematic review, rather a narrative historical description of the past history, and a look forward to the future opportunities.

New Routes of Allergen Immunotherapy

Objectives

Allergen immunotherapy is the only cure for immunoglobulin E mediated type I respiratory allergies. Subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT) are the most common treatments. In this article, we reviewed new routes of allergen immunotherapy.

Methods

Data on alternative routes to allow intralymphatic immunotherapy (ILIT), epicutaneous immunotherapy (EPIT), local nasal immunotherapy (LNIT), oral immunotherapy (OIT), and oral mucosal immunotherapy (OMIT) were gathered from the literature and were discussed.

Results

ILIT features direct injection of allergens into lymph nodes. ILIT may be clinically effective after only a few injections and induces allergen-specific immunoglobulin G, similarly to SCIT. A limitation of ILIT is that intralymphatic injections are required. EPIT features allergen administration by using patches mounted on the skin. EPIT seeks to target epidermal antigen–presenting Langerhans cells rather than mast cells or the vasculature; this should reduce both local and systemic adverse effects. LNIT involves the spraying of allergen extracts into the nasal cavity. Natural or chemically modified allergens (the latter, termed allergoids, lack immunoglobulin E reactivity) are prepared in a soluble form. OIT involves the regular administration of small amounts of a food allergen by mouth and commences with low oral doses, which are then increased as tolerance develops. OMIT seeks to deliver allergenic proteins to an expanded population of Langerhans cells in the mucosa of the oral cavity.

Conclusions

ILIT, EPIT, LNIT, OIT, and OMIT are new routes for allergen immunotherapy. They are safe and effective.

Novel routes for allergen immunotherapy: safety, efficacy and mode of action

Allergen immunotherapy is the only curative treatment of IgE-mediated type I respiratory allergies. Subcutaneous immunotherapy (SCIT) is used as a reference therapy and has transformed allergic treatments; it improves symptoms (asthma and rhinitis) as well as the quality of life of patients. SCIT requires repetitive administration and carries the risk of severe systemic adverse effects, including anaphylaxis. Sublingual immunotherapy is now a valid noninvasive alternative to SCIT, as a safe and efficacious treatment for respiratory allergies. In this article, we compare various routes of allergen immunotherapy, including SCIT and sublingual immunotherapy, as well as more exploratory routes currently under investigation (i.e., intralymphatic, epicutaneous, intranasal and oral). We discuss their respective advantages, as well as their foreseen modes of action.

Novel ways for immune intervention in immunotherapy: mucosal allergy vaccines

Allergen-specific immunotherapy is currently the only curative treatment for allergy. Subcutaneous immunotherapy (SCIT) has been successfully used to treat patients who are allergic to insect venom, house dust mites, or tree or grass pollens. In the context of potentially severe, albeit infrequent, side effects associated with SCIT, mucosal routes of administration are being investigated to conduct allergenic desensitization. This article reviews recent developments in the field of nasal, oral, and sublingual immunotherapy as they relate to safety, clinical efficacy, and immune mechanisms of action. Implications for the design and development of improved allergy vaccines that could be used through such nonparenteral routes are discussed. Specifically, allergen presentation platforms and adjuvants facilitating the targeting of immune cells at mucosal surfaces to promote tolerance induction are reviewed.

Efficacy of sublingual swallow immunotherapy in children with severe grass pollen allergic symptoms: a double-blind placebo-controlled study

BACKGROUND

Local application of allergen extracts in specific immunotherapy is accompanied by increased compliance and significantly reduced side effects. However, efficacy of local immunotherapy in children has yet not been sufficiently demonstrated. This study was performed to determine clinical efficacy of high dose sublingual swallow immunotherapy (SLIT) by a double-blind placebo-controlled study in children with grass pollen allergy using high dose allergen extracts.

METHODS

A total of 161 children with seasonal rhinoconjunctivitis of which, 68 had also asthma symptoms were enrolled in a multicenter double-blind placebo-controlled study for 1 year and treated on a daily basis with sublingually applied allergen drops. After 1 year all children were given treatment for another 2 years in an open-controlled setting. Symptom scores and medication were assessed during the pollen seasons with structured interviews. Applied allergen dosage, compliance, and side effects were documented by daily diary cards. Primary endpoint was a clinical index (CI) combining symptom scores with medication index. Titrated skin prick tests (SPT) and specific antibody measurements were performed each year.

RESULTS

Combining symptom with medication scores to CI was highly reliable (reliability coefficient = 0.89, standard error = 9.6%). Allergen-specific IgE- and IgG-subclass antibodies increased significantly in patients treated with SLIT indicating an activation of the immune response induced by the locally applied grass pollen extract. SPT reactivity did not change during therapy. After 1 year of SLIT in the original design we observed no significant difference in the CI between treatment and placebo analyzing all patients included in the study per intention to treat and per protocol. However, subgroup analysis in a repeated measures model revealed that patients with SLIT and severe symptoms before the beginning of treatment (CI > mean/ > 1.51) showed a significant improvement of clinical symptoms after 3 years.

CONCLUSION

In this study SLIT was accompanied by a significant placebo effect. Efficacy of treatment could only be seen in children with severe clinical symptoms and this became clinically marked after 3 years of therapy.

Immune response of the coeliac nasal mucosa to locally-instilled gliadin

We previously demonstrated a specific gluten-induced response in the rectal mucosa of coeliac patients. In the present study, we have evaluated the immune response to local gliadin challenge in the nasal mucosa of coeliac patients preliminary to exploring the feasibility of immune modulation by the nasal route. The local response to gliadin was evaluated on non-invasive scrapings of nasal mucosa. Cells harvested from the nasal scrapings of 21 coeliac patients and 12 healthy controls were counted after immunohistochemical staining. Six hours after gliadin challenge, the total number of cells was increased in coeliacs but not in controls. The increase was due principally to lymphoid cells and granulocytes. CD3+ cells doubled after gliadin challenge, but not after albumin control challenge. There was a similar rise in CD25+ cells, whereas the number of ICAM-expressing cells did not increase significantly. In control subjects, both gliadin and albumin induced a moderate but not significant increase in total cell number. In conclusion, the gliadin antigen provokes a mild inflammatory response in coeliac nasal mucosa.

Pharmaceuticals--cost or investment? An employer's perspective

Employers are becoming increasingly concerned about rising pharmaceutical costs. Are improved health and cost outcomes achieved as a result of increasing pharmaceutical costs? One should approach this issue with a holistic view that considers the overall impact that disease conditions have on health and productivity. To illustrate, we first identified the "top ten" most expensive physical and mental health concerns facing American businesses, using data from over 60 firms from the 1996 MarketScan Private Pay Fee-For-Service Research Database. For some of these top ten conditions, the literature already addresses the drug cost versus investment issue, with mixed results. For conditions in which uncertainty prevails and for other high-cost conditions, empirical analyses should address the drug cost versus investment issue to minimize the risk of a penny-wise and pound-foolish payment/coverage policy. A similar strategy should be applied to individual corporate diagnostic assessments.