MicroRNAs—Are They Possible Markers of Allergic Diseases and Efficient Immunotherapy?

Micro-RNAs (miRNAs) are short, non-coding RNA molecules regulating genes' expression. Studies published over last years demonstrated that they play an important role in allergic diseases by regulating humoral and cellular immunity, cytokine secretion and epithelium function. Some of them seem potential non-invasive biomarkers facilitating diagnosis of the most common allergic diseases, such as allergic rhinitis (miR-21, miR-126, miR-142-3p, miR-181a, miR-221), asthma (miR-16, miR-21, miR-126, miR-146a, miR-148a, miR-221, miR-223) and atopic dermatitis (miR-24, miR-124, miR-155, miR-191, miR-223, miR-483-5p), or objectively assessing severity of inflammation and endotype of the disease. In spite of the large body of literature available, its scientific value is limited due to the small numbers of study participants, heterogeneity of populations enrolled, and diverse methodology. Some studies have revealed significant changes in miRNAs' profile in the course of allergen immunotherapy. Tolerance induction is associated with processes controlled by miRNAs: enhanced activity of Treg cells and increased production of tolerogenic IL-10 and TGF-β. Thus, miRNAs may be candidates as biomarkers of successful immunotherapy. Finally, they are also possible therapeutic agents or targets of therapies based on antagomirs blocking their activity. However, so far no studies are available that demonstrate efficacy in overcoming delivery barriers, tissue targeting or drugs' safety. As a consequence, despite promising results of in vitro and animal model studies, translation into human therapeutic agents is uncertain.