SLIT: Specific Mechanism of Action
Induction of tolerance via similar mechanisms as SCIT but via uptake of antigen by dendritic cells in the sublingual region of the oral cavity
• Sublingual allergen extracts are primarily taken up by dendritic cells in the mucosa and presented to T cells in the corresponding lymph nodes.
1. Likely mechanisms of action in immune tolerance is similar to what is described above.
2. Within the oral and sublingual mucosa, effector cells, such as mast cells, are less numerous—a possible factor in the lower rates of adverse systemic allergic reactions seen with SLIT.
Allergic Rhinoconjunctivitis and Allergic Asthma
Level I evidence that both SCIT and SLIT are effective at decreasing symptoms, prevent new sensitizations, prevent asthma, and provide long-term symptom control
• Duration of efficacy: effects can last for several years after treatment (7 to 12 years)
• Multiple studies have demonstrated improvement in symptom score, medication score, favorable changes in immunologic markers, and improvements in quality of life.
• Both SLIT and SCIT reduce topical corticosteroid use and improve allergic disease severity.
Prevention
• SCIT and SLIT appear to prevent progression of allergic rhinitis to asthma and the development of new allergen sensitivities.
Cost Comparison
• Studies comparing cost effectiveness have indicated that immunotherapy compared to pharmacotherapy might be associated with cost savings as high as 80% 3 years after completion of treatment.
Currently no direct head-to-head studies have been completed but both methods of immunotherapy appear to convey benefit.
• Meta-analyses comparing the two treatment options for grass pollen found greater overall benefit with SCIT; however, the data was indirect and limited by a very high degree of heterogeneity.
• A small number of trials have directly compared SLIT and SCIT, finding SCIT to be at least somewhat more effective than SLIT.
• SLIT appears to be safer with less risk of anaphylaxis.
Indications for Use of Immunotherapy (SCIT or SLIT)
Immunotherapy may be used for:
• Allergic rhinitis (seasonal or perennial), with or without allergic conjunctivitis
• Allergic asthma (seasonal or perennial)
• Stinging insect hypersensitivity
• Atopic dermatitis: may respond if the patient is sensitized to inhalant allergen (aeroallergen)
Must Have Clinically Relevant Allergic Component to Their Disease Established By
• History of symptoms with exposure to the allergen. This is the most important consideration when deciding whether to test and treat a patient with immunotherapy since a high percentage of the US population is atopic basic on allergy testing, but not all patients with a positive test have clinically relevant symptoms.
• Presence of specific IgE to that allergen, demonstrated through allergen skin testing or serum tests (positive allergen test that is clinically significant).
Trial of Control Measures
A trial of pharmacotherapy and environmental control measures is reasonable prior to initiation of immunotherapy; the data regarding environmental control measures and efficacy is weak.
• Patients should be considered for immunotherapy for the following:
1. Side effects of medication use
2. Noncompliance with medication regimen or suboptimal use of medication devices
3. Persistent symptoms with inadequate or partial response to pharmacotherapy/environmental controls
4. Patient preference
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