Screening and characterization of activin A inhibitory peptides by phage display technology

Background: Activin A has been reported to play a proinflammatory role in the development and progression of idiopathic pulmonary fibrosis (IPF). Follistatin, an activin A inhibitor, is activated by a feedback loop causing increased activin A production, resulting in fibrosis. Aims: To develop binding peptides with the ability to inhibiting activin A action without triggering a feedback loop involving follistatin and activin A overexpression. We hypothesized that activin A inhibition by this mechanism can ameliorate IPF symptoms and slow the disease progression. Methods: Phage display was used to select 48 peptides against activin A. Neutralizing anti-activin A antibody was used for competitive elution. Through phage DNA sequencing 10 different sequences were obtained. Binding activities were evaluated by phage-ELISA. Bioinformatics was used to predict peptides tridimensional structure and binding site to activin A molecule model. Results: Peptides corresponding to the three most reactive phages in phage-ELISA were chosen to be chemically synthesized. Structure prediction by Pepfold2 and docking analysis by GalaxyPepDock software revealed similarities between the selected peptides and the extracellular domain of the activin A receptor type 2, ActRIIB. Conclusions: Selection of binding peptides against activin A can allow us to target activin A for antifibrotic therapy. Although bioinformatics analysis demonstrated a certain degree of success in peptides selection and their ability to bind to activin A in the same site as the receptor ActRIIB, further in vivo and in vitro assays will be conducted to evaluate peptides inhibitory activity and their potential to counteract IPF progression.