Effects of omalizumab treatment on gut microbiome in adolescent patients with chronic spontaneous urticaria

Abstract Background: Omalizumab is a humanized anti-immunoglobulin (Ig)E monoclonal antibody that is effective for some patients with chronic spontaneous urticaria (CSU) who do not respond to antihistamines. However, the mechanism by which omalizumab improves urticaria remains obscure. Gut microbiome plays a role in the pathogenesis of allergies. Here, we aimed to investigate differences in gut microbiome of adolescent CSU patients before and after omalizumab treatment, which has not been reported until date. Methods: Ten adolescent patients with CSU were given 300 mg omalizumab subcutaneously in three treatment sessions at 4-week intervals. The personal and clinical factors of patients before and after treatment were collected. Urticaria Activity Score (UAS7) was applied to evaluate the efficacy of omalizumab treatment every 4 weeks during the follow-up period. Fecal samples were collected before treatment and at 12 weeks after the first treatment. Total DNA of the gut microbiota in all fecal samples were extracted. The 16S rRNA gene-targeted sequencing technology was used for the analysis of the diversity and distribution of gut microbiome, followed by bioinformatics analysis. Results: UAS7 scores decreased significantly after each omalizumab treatment sessions compared with the baseline (all P < 0.0001). The dominant bacteria in fecal samples before and after treatment were Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria at the phylum level. Alpha diversity analysis showed no significant difference before and after omalizumab treatment (P > 0.05) whereas beta diversity analysis revealed significant difference in the bacterial abundance before and after omalizumab treatment (P < 0.01) in adolescent patients with CSU. The relative abundance of Alphaproteobacteria and Betaproteobacteria at the class level and Burkholderia, Rhodococcus, and Sphingomonas at the genus level decreased significantly after omalizumab treatment (linear discriminant analysis > 4, P < 0.05). The functional prediction results showed that the differences noted before and after treatment were mainly in the dioxin and xylene degradation pathways, which were more abundant in adolescent patients with CSU before omalizumab treatment.Conclusions: Omalizumab is effective in treating CSU and can reduce the abundance of Alphaproteobacteria and Betaproteobacteria, which may help improve the treatment outcomes of CSU in adolescent patients.