(1) Background: Biomarkers of efficacy for subcutaneous immunotherapy (SCIT) on allergic rhinitis have not been evaluated in details. The present study aims to assess the relevance of measuring of sIgE, sIgG4 and IgE/IgG4 ratio during SCIT in patients with allergic rhinitis; (2) Methods: 20 patients, 13 men and 7 women aged 19 to 58 years, with clinically manifested seasonal and perennial allergic rhinitis were studied. At the initiation and in the end of the three-year course of SCIT serum allergen-specific IgE and IgG4 were measured with ImmunoCAP system. The sIgE/sIgG4 ratio was calculated as a biomarker for immunologic effectiveness; (3) Results: There was a significant increase of sIgG4 antibodies (p < 0.05), while at the end of SCIT for the sIgE levels no significant changes were seen (p > 0.05). Moreover, 90% of patients showed a decrease of the IgE/IgG4 ratio; (4) Conclusions: In most of treated patients with AR, SCIT with Bulgarian allergen products leads to clear immunological changes. After a 3-year of SCIT there is a significant increase in allergen specific IgG4 levels and both decrease of sIgE and IgE/IgG4 ratio. sIgE, sIgG4 and IgE/IgG4 ratio can be used as a substantial biomarker for predicting immunological effectiveness of SCIT.

Introduction. In Bulgaria, mold allergies are common, and sensitization to different fungal species is found in many patients with atopy.The objective of this study is to explore sensitization to the most widespread mold species in Bulgaria, and to determine the extent of sensitization to Alt a1, a major allergen of Alternaria alternata, by using component-resolved diagnosis.Materials and Methods. 21 patients (14 males and 7 females, age range 5-40 years), with respiratory allergy participated in the study. All patients are sensitized to mix of fungal allergens containing: Alternaria alternata, Aspergillus sp., Cladosporium herbarum, Penicillium notatum, proved by in vivo and in vitro methods. All patients underwent the ImmunoCAP test and were assessed for sIgE to individual fungal allergens: m1 Penicillium notatum, m2 Cladosporium herbarum, m3 Aspergillus fumigatus and m6 Alternaria alternata. The component-resolved diagnosis to Alt a1 was performed for 10 patients with increased sIgE to m6 Alternaria alternata.Results. All studied patients (100%) had elevated sIgE to Alternaria alternata. Eight (38%) patients were sensitized to Penicillium notatum. 11 (52%) and 10 (48%) patients were sensitized to Cladosporium herbarum and to Aspergillus fumigatus, respectively. Ten patients (48%) were monosensitized to Alternaria alternata. Nine (90%) patients with sensitization to Alternaria alternata demonstrated elevated levels of IgE to Alt a1.Conclusion. Alternaria alternata most often causes sensitization in patients with respiratory allergy. The component-resolved diagnosis using Alt a1 is a precision marker to prove species-specific sensitization to Alternaria alternata.