[Effect of 1-year specific immunotherapy with standardized house dust mite vaccine on mild to moderate allergic asthmatic patients].

OBJECTIVE: To evaluate the clinical efficacy and safety of specific immunotherapy (SIT) with standardized house dust mite (HDM) vaccine on allergic asthmatic patients.

METHODS: The investigation was a multicentre, randomized, double-blind, placebo-controlled clinical study. 132 patients with mild to moderate asthma who were allergic to HDM, recruited from three hospitals of China (The First Affiliated Hospital of Guangzhou Medical College, Shenyang General Military Hospital, Suzhou Children's Hospital), were randomly allocated to the active group (n = 66) or the control group (n = 66) respectively. The active group received SIT with a standardized depot Dermatophagoides pteronyssinus (Der p) extract absorbed to aluminium hydroxide (Alutard SQ, ALK-Abelló, Denmark), while the control group received a placebo containing histamine dihydrochloride by subcutaneous injections for 1 year. Treatment of each group was started from the initial concentration. Updosing was performed with weekly injections from four 10-fold dose-increase vials (active group: 100, 1,000, 10,000, 100,000 SQ-U/ml, control group: 0.01, 0.1, 1.0, 10 microg/ml. 100,000 SQ-U/ml of Der p extract contains 9.8 microg/ml of the majoy allergen Der p1). The single-dose was injected weekly with 0.2, 0.4, 0.8 ml of each concentration in turn from the preceding 3 vials, totally for 9 weeks. Subsequently, the dose with 0.1, 0.2, 0.4, 0.6, 0.8 ml of the highest concentration was injected weekly from the 10th-14th week and a maintenance dose with 1 ml was reached at the 15th week. The dosing interval was then gradually increased to 2, 4, 6 weeks until the end of the first 26-weeks updosing phase (phase I, H(1)). Thereafter, the dosing continued at 6-week intervals for maintenance phase (phase II, H(2)) till the end of the complete treatment. The patient was observed for at least 30 minutes in the clinic after each injection.

RESULTS: A total of 132 subjects were randomized and 129 subjects (64 in the active group, 65 in the control group) completed the whole study. Dropouts included three females because of poor compliance, being afraid of the epidemic of Severe Acute Respiratory Syndrome (SARS) and emigration respectively. Both groups were comparable at baseline in all clinical and laboratory parameters. The mean daily symptom scores in 4-weekly began to diverge at the 29th-32nd week with the active group showing a significant lower scores (0.17 +/- 0.33) than the control group (0.39 +/- 0.74, Z = 2.031, P < 0.05) till the end of the study. Significant difference was found in average daily symptom scores between H(1) (0.29 +/- 0.39) and H(2) (0.19 +/- 0.27) in the active group (Z = 2.923, P < 0.01), while no significant difference was found between H(1) (0.45 +/- 0.62) and H(2) (0.40 +/- 0.68) in the placebo group (Z = 1.885, P > 0.05). There were significant differences in subjective judgement of the improvement about overall asthmatic symptoms, exacerbation severity and exacerbation frequency between the active group (96.9%, 95.3%, 95.4%) and the control group (80.0%, 75.4%, 83.1%) with the self-evaluation questionnaire (chi(2) = 13.246, 11.576, 16.204, all P < 0.01). The trend line of daily medication scores in weekly intervals showed a significant decline. The mean daily medication score of phase II (0.20 +/- 0.36) was significant lower than that of phase I (0.33 +/- 0.67, Z = 3.344, P < 0.01), whereas the control group did not show a significant difference between phase II (0.35 +/- 0.96) and phase I (0.32 +/- 0.95, Z = 0.744, P > 0.05). After 1-year treatment, no significant differences were found in morning and evening peak expiratory flow of predicted value (PEF%), forced expiratory volume in one second of predicted value (FEV(1)/FVC), forced vital capacity of predicted value (FVC%), forced expiratory volume in one second to forced vital capacity ratio (FEV(1)/FVC), provoking dose decreasing FEV(1) by 20% (PD(20)-FEV(1)) between the active group [(97 +/- 17)%, (98 +/- 18)%, (91 +/- 11)%, (98 +/- 9)%, (82 +/- 10)%, 2.35 (7.9) micromol] and the control group [(99 +/- 19)%, (100 +/- 19)%, (90 +/- 14)%, (99 +/- 13)%, (82 +/- 9)%, 1.80 (7.8) micromol] (t = 0.170 - 0.630, Z = 0.264, all P > 0.05). Skin index (SI) to Der p in the active group (1.2 +/- 0.5) was significantly lower than that of the control group (1.5 +/- 0.6) after treatment (t = 2.395, P < 0.05). There was no significant difference in the level of serum sIgE against Der p between groups, which was 76.80 (97.0) kU/L in active group and 66.50 (99.3) kU/L in the control group (Z = 0.232, P > 0.05). The frequency of systemic adverse reactions graded by guidelines based on the position paper of European Academy of Allergology and Clinical Immunology (EAACI), was 5.7% and 1.8% of the total injections in the active group and the control group, respectively. Although significant difference was found in adverse reactions between groups (chi(2) = 4.705, P < 0.05), all were mild or moderate. The majority occurred within 30 minute after injection and were controlled well with symptomatic therapy. No any severe systemic adverse reaction was shown in the study.

CONCLUSION: One year specific immunotherapy with standardized house dust mite (HDM) vaccine significantly improved symptoms and reduced medication use in mild to moderate allergic asthmatic patients. SIT also reduced skin prick test reactivity to Der p. Complying with the EAACI immunotherapy guidelines, SIT with standardized HDM vaccine was a safe treatment.