The build-up phase outcome of subcutaneous immunotherapy for pediatric allergic asthma: A retrospective cohort study from Surabaya, Indonesia

Open access: www.balimedicaljournal.org and ojs.unud.ac.id/index.php/b j The build-up phase outcome of subcutaneous immunotherapy for pediatric allergic asthma: A retrospective cohort study from


INTRODUCTION
House dust mite (HDM) allergen exposure is increasingly recognized as an essential cause of allergic asthma in children, particularly in Indonesia. The prevalence of asthma in Indonesia ranges from 3-16%. HDM allergens induce sensitization in 77% of asthmatic patients. 1,2 Subcutaneous immunotherapy (SCIT) is an established recommended treatment for allergic asthma with a broad and potential evidencebased treatment. [3][4][5][6] Although data are limited, the efficacy of allergen-specific immunotherapy against pediatric asthma in Surabaya, Indonesia has been reported in a small number of placebo-controlled studies. 7- 10 SCIT provides symptomatic relief and is potentially curative. The immunologic mechanisms of SCIT include all parts of the immune system. Regulatory T cells (T reg ) have a major pivotal role in the immunotherapy triumph. In addition to T regs , elevated suppressor cytokine levels (TGF-β), suppression of TH 2 cells, increased titers of IgG 4 as well as gradual declines in the number and function both of basophils and mast cells also contribute to the successful treatment. 11 The aforementioned immune mechanisms are connected and related to each other, acting at different times during SCIT. Allergen-specific immunotherapy reduces health care costs within three months of initiation 12 and produces sustained clinical benefits after the completion of a treatment course, approximately 3-5 years. 13 Clinically successful SCIT is accompanied by altered allergen-specific T cell responses such as a decreased TH 2 /TH 1 ratio, enhanced TGF-β secretion, and T reg induction. 14 SCIT is administered at a physician's office at least every six weeks for 3-5 years, 12 but it does not usually confer immediate symptom relief. Successful clinical outcomes require a strong patient commitment to treatment adherence. Available data suggest that patient demographics, illness, and insurance characteristics may substantially ORIGINAL ARTICLE wheals. Total IgE levels were measured using the ImmunoCAP system (Thermo-Fisher, Uppsala, Sweden).
Informed consent was obtained from either each patient or his or her legal guardians before study inclusion. The ethics committee of Dr. Soetomo Hospital approved this study. General dataincluding name, address, age, gender, body weight, body height, and telephone number -were collected and recorded for all participants. A comprehensive medical and allergy history was obtained for all subjects, especially on allergic asthma and its duration, as well as details about allergies and controller medications for family members.

Clinical evaluations
Based on Dr. Soetomo General Hospital guidelines for SCIT, the authors reviewed subjects' diaries, medical records on drug prescriptions, the presence of exacerbation, AEs during immunotherapy, and the results of lung function tests and serum total IgE levels over the treatment period. The subjects' diary cards recorded symptoms and medication scores, including daytime symptoms, limitation of activities, nocturnal symptoms or awakening, need for reliever or rescue treatment, lung function, and exacerbation history.
The level of asthma control was recorded in each patient's standardized hospital medical record based on GINA guidelines. Controlled asthma was defined as daytime symptoms no more than two types per week, no limitation of activities, no nocturnal symptoms or awakening, use of reliever or rescue treatment no more than two types per week, normal lung function, and no exacerbation history. Second, partially controlled, the presence of at least one criterion among daytime symptoms more than twice per week, any limitation of activities, any nocturnal symptoms or awakening, need for reliever or rescue treatment more than twice per week, less than 80% predicted or normal lung function result and one or more exacerbations per year. At least, uncontrolled asthma, the presence of at least three of the criteria for partial control.
As for each patient, the total number of medications taken daily (systemic antihistamines, nasal cromoglycate, ocular cromoglycate, beta-2 agonist) was recorded on the daily diary cards. Symptoms and medication scores were determined as the monthly cumulative values obtained by summing the daily scores. The clinical evaluation also included SPTs for Der p 1 and Der f 1, eosinophil counts, and assessment of the reversibility of FEV1. The immunological assessment included an examination of the plasma levels of IFN-γ (TH 1 ), IL-4 (TH 2 ), TGF-β (T regs ), IL-17 (TH 17 ), and total IgE. influence treatment adherence. 15 Patient education regarding the treatment course and the slow effect are important factors for improving compliance and treatment outcomes. 16 One-third of treated patients fail to complete SCIT. Among those who complete SCIT, another one-third (34.6%) did not believe that the therapy was effective. 17 The SCIT satisfaction scores at the end of treatment were higher than those in the first year of therapy among adherent patients. 18 The duration of SCIT may be prolonged (5 years or more) depending on the clinical response of the subjects. Currently, no specific laboratory tests or biomarkers are available to distinguish patients who will relapse from those who will enjoy prolonged clinical remission after discontinuing SCIT. 19 The duration of SCIT should be individualized from the patients' clinical response, disease severity, adverse events (AEs), and preferences. 20 The build-up phase (3 months) clinical outcomes of SCIT represent valuable information for patient education to improve patient compliance and treatment outcomes. Those could be according to disease severity, clinical response, and immune response to SCIT.

Subjects
The retrospective cohort study comprised 65 children with allergic asthma due to HDM allergens who finished the initial build-up phase of SCIT (3 months) from 2009 until 2012 at Dr. Soetomo General Hospital in Surabaya, Indonesia. The subjects were 6-17 years old and they had a diagnosis of asthma as defined by the American Thoracic Society (i.e., "a disease characterized by increased responsiveness of the trachea and bronchi to various stimuli and manifested by widespread narrowing of the airway that changes in severity either spontaneously or as a result of therapy") for ³ 3 months. The inclusion criteria were as follows: pre-bronchodilator forced expiratory volume in 1 s (FEV1) ³ 60% and £ 90% of the Polgar predicted normal value, reveals the reversibility criteria defined as an increase in FEV1 ³ 12% from the prebronchodilator value 15-30 min after two actuation of salbutamol pMDI (100 mg/actuation), and fits them with the GINA criteria for uncontrolled asthma.
A skin prick test (SPT) was applied to examine sensitivity to the following HDM allergens (Allergopharma, Reinbek, Germany): Dermatophagoides pteronyssinus (Der p 1) and Dermatophagoides farinae (Der f 1). Reactivity to HDM allergens in the SPT was identified via allergen-induced wheals with an equal or larger diameter mean than histamine-induced every week for 14 weeks, followed by once-monthly maintenance doses. Outcomes were evaluated after the initial build-up phase.

Statistical analysis
The sample size of 65 patients provided sufficient power (90%) to detect a difference of 10% among 3 groups ( = 0.05). Statistical analysis was performed via multivariate testing, as well as used SPSS software. Data are presented as the mean ± SD, and p-values of 0.05 or less were considered statistically significant. Table 1 showed the demographic and clinical parameters of the patients (n = 65) prior to the initial treatment. The standardized hospital medical records revealed that all subjects were sensitive to HDMs, as evaluated via skin test (wheal ≥ 3 mm), and all met the GINA criteria for uncontrolled

Symptoms and lung function
The clinical parameters of the subjects after the initial build-up phase are shown in Table 2. Symptoms and lung function significantly differed among subjects with controlled, partially controlled, and uncontrolled asthma. Improvements of symptoms and lung function were observed in 48 of 65 subjects (73.8%) after three months of SCIT, including partial and complete control in 37 (56.9%) and 11 (26.2%) subjects, respectively ( Table 2). Table 3 presented data for various laboratory parameters after the initial build-up phase of SCIT. The results illustrated that subjects with uncontrolled asthma had significantly higher eosinophil counts than those with controlled or partially controlled asthma (p = 0.029). Additionally, IL-4 (p = 0.008) and IL-17 levels (p= 0.000) were also significantly elevated among subjects with uncontrolled asthma, whereas these subjects exhibited significantly lower IFN-γ levels (p= 0.002) and significantly smaller wheal diameters for Der p 1 (p = 0.000) and Der f 1 (p = 0.000). Total IgE and TGF-β levels did not significantly differ according to the improvement of asthma. Figure 1 and 2 illustrated that the non-improved group had significantly higher eosinophil counts (p = 0.009) than the improved one (both partially controlled and controlled asthma), as well as had significantly higher IL-4 (p = 0.045) and IL-17 levels (p = 0.000). Meanwhile, IFN-γ levels (p = 0.001)

In vitro cytokine measurements
Plasma cytokines levels were measured via ELISA using a human TH 1 /TH 2 /T reg cytometric bead array kit according to the manufacturer's instructions (BD Biosciences). All samples were examined in duplicate.

Immunotherapy
All subjects conducted SCIT with HDM allergen extract produced by the Dr. Soetomo General Hospital Pharmaceutical Unit. The treatment period was divided into two phases: an initial build-up phase and a maintenance phase. In the initial buildup phase, subjects received subcutaneous injections of gradually increasing doses of allergen extract

DISCUSSION
The goals of asthma therapy are to alleviate symptoms, minimize risks of adverse outcomes (e.g., hospitalization, loss of lung function), and minimize AEs associated with treatment. 21-24 In our retrospective cohort study, SCIT using HDM allergen extract improved symptoms and lung function in nearly three-fourths of subjects within 3 months. In line with this finding, the previous studies reported that the majority of patients receiving immunotherapy exhibit increased FEV 1 within 3 months. 7,25 However, these findings conflicted with those obtained by Maggie et al. 26 Larger wheal diameters for Der p 1 and Der f 1 in patients with uncontrolled asthma indicates that we can create these variables to predict the clinical outcomes of SCIT. 27 The findings were different from those of other studies in children and adults, which observed significantly higher baseline levels of specific IgE to HDM allergens in responders. [28][29][30][31] A previous study demonstrated the effectiveness of immunotherapy was in line with the increased levels of TH 1 and T regs . 32 There were also some reports that IFN-γ levels were identified more increased against post-immunotherapy. 33-35 On the other hand, post-immunotherapic TGF-β levels were also turned up progressively as gained from the previous study. 32,36,37 The wheal diameters for Der p 1 and Der f 1 represent the reactivity of patients to the HDM allergens, which is caused by high levels of allergen-specified IgE. IgG 4 levels were remained low after HDM SCIT in some patients. 38 High IgG 4 levels are associated with high levels of IFN-γ as well as a previous research confirmed high IgG 4 levels were in line with high levels of IL-10 and TGF-β. 39 Higher IFN-γ levels in uncontrolled asthma and wheal diameters for both Der p 1 (p = 0.000) and Der f 1 (p = 0.000) were significantly lower in the non-improved group. Total IgE and TGF-β levels were not significantly different between the groups. patients indicated an opportunity to provide other immunomodulators as adjunct immunotherapies. 40 Most clinical trials that evaluated the efficacy of SCIT had a treatment period of approximately 1-2 years. 41 The current study evaluated an early efficacy because the effects of SCIT after the build-up phase are considered as important data for a patient education program to improve compliance and treatment outcomes. Nevertheless, the endotype, phenotype, and severity of allergic diseases differ among patients. In this regard, lower eosinophil counts and stronger TH 1 and T reg immune responses were significantly associated with uncontrolled asthma at the end of the build-up phase of SCIT in pediatric allergic asthma provoked by HDM allergens.

CONCLUSION
This retrospective cohort study found that SCIT improved symptoms in 73.8% of pediatric allergic asthma at the end of the build-up phase. The improved outcome was associated with lower eosinophil counts, lower IL-10 and IFN-γ levels, higher IL-4 levels, and smaller wheal diameters for Der p 1 and Der f 1.

LIMITATIONS
The present study had several limitations. In addition to its retrospective nature, the lack of a control group that did not receive SCIT made it difficult to estimate the true effectiveness of SCIT. In addition, the study covered maintenance durations of 3 months in patients at a single institution. and improved groups (both partial controlled and controlled asthma) at the end of the build-up phase of subcutaneous immunotherapy.