Birch allergy: could one shot change everything?

#AllergicRhinoconjunctivitis #IgG4 #Allergoid #BirchPollen #Immunotherapy  


Allergic rhinoconjunctivitis (ARC) induced by birch pollen is one of the most common forms of seasonal allergic disease in Europe. It affects up to 40% of the population, with a high concentration of cases in temperate regions where birch trees are prevalent. This condition presents with a combination of eye symptoms (conjunctivitis, itching, tearing) and nasal symptoms (runny nose, sneezing, congestion), severely impacting quality of life, concentration, and sleep.  

Conventional treatments, such as oral antihistamines, corticosteroid nasal sprays, and anti-allergic eye drops, aim to temporarily relieve symptoms. However, they do not target the underlying immunological mechanisms of the disease. Moreover, they do not prevent the worsening of the allergy, the development of new sensitivities, or the progression to allergic asthma.  

Allergen immunotherapy (AIT) is currently the only therapeutic option capable of durably modifying the natural course of ARC. By gradually exposing the body to the offending allergen, it induces specific immune tolerance, notably through the activation of regulatory T cells (Tregs) and the production of blocking IgG4 antibodies. AIT is therefore recommended for patients with moderate to severe forms or for those whose symptoms are poorly controlled by symptomatic treatments.  

One of the main obstacles to AIT is the duration of traditional protocols, which require either repeated injections (SCIT) or prolonged daily intake (SLIT). This often hampers patient adherence. As a result, there is growing interest in shorter, more convenient protocols that can offer comparable effectiveness. Allergoids conjugated to mannan illustrate this progress. By directly targeting dendritic cells, they induce tolerance more rapidly while reducing the number of necessary injections.    

Five injections, a peaceful spring?

For this study, 298 adults allergic to birch pollen were selected. Participants received five pre-seasonal subcutaneous injections of a mannan-conjugated allergoid (T502, 10,000 mTU/mL) or a placebo. Effectiveness was measured using the Combined Symptom and Medication Score (CSMS), quality-of-life questionnaires (RQLQ), and changes in immunological markers (IgE, IgG, and IgG4 specific to Bet v 1).  

The results showed a 33% drop in CSMS in the T502 group, with a 30.4% reduction in symptoms and a 56.3% decrease in medication use. Quality of life improved by 31.5%. Immunologically, there was a 6.2-fold increase in specific IgG4 and a 62.9% reduction in the IgE/IgG4 ratio, indicating a shift toward a tolerant immune response. Additionally, no deaths or serious adverse events were reported. Local reactions were mostly mild and transient, and grade I/II systemic reactions affected only 8.1% of patients. The absence of epinephrine use and the high completion rate (91%) underscore the good tolerability and acceptability of this short protocol.  

Excellent tolerability, confirmed efficacy

Birch pollen-induced allergic rhinoconjunctivitis is a common, seasonal condition that often significantly impairs quality of life during spring. In a context where symptomatic treatments remain limited, allergen immunotherapy emerges as a major therapeutic option capable of durably altering disease progression. However, traditional protocols hinder patient adherence. Against this backdrop, the study aimed to evaluate the effectiveness and tolerability of a short-course subcutaneous immunotherapy.  

The findings show that this protocol has significant clinical efficacy. Treated patients experienced reduced allergic symptoms, significantly decreased medication use, and marked improvements in quality of life. From an immunological perspective, the treatment is associated with a shift in the immune response toward tolerance. Tolerability was excellent, with mostly mild and transient local side effects and a very low incidence of moderate systemic reactions. No serious adverse events or deaths were reported.  

Although these results clearly support the potential of a short-course protocol, certain limitations should be noted. The study was conducted over a single pollen season, offering no insight into the long-term durability of clinical and immunological effects. The long-term impact of this treatment remains to be confirmed. Furthermore, the pediatric population was not included, and its effectiveness under real-life clinical conditions was not assessed.  

Nonetheless, these limitations do not detract from the promising potential of this protocol, which is particularly suitable for patients who are reluctant to commit to prolonged treatments. It could also be adapted for other seasonal allergies, paving the way for a new generation of immunotherapies that are more accessible, faster, and better aligned with patient needs.  

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