Characterization of the molecular mechanism and optimization of anti-inflammatory peptides

The innate immune system is a major barrier against invading pathogens. However, dysregulation of innate immunity during successful viral infections manifests in excessive or chronic innate immune activation (inflammation) that defines acute severe disease (cytokine storms) or even long-term symptoms such as post-acute sequalae (LongCOVID). Of note, chronic inflammation is well-known to contribute to the development, progression and treatment resistance of cancer. Thus, excessive or chronic inflammation exacerbates diseases and therefore has to be avoided. To counteract inflammation, currently mainly unspecific immunosuppressive drugs (e.g. corticosteroids), JAK/STAT inhibitors, and antibodies are used in the clinics which are accompanied by severe side effects or very high costs. The human peptidome is a unique source of specific modulators of innate immune processes. Further, human-derived peptides are ideally suited for this purpose, as the innate immune system is highly effectively and specifically regulated by small proteins and peptides. Recently, a novel endogenous anti-inflammatory peptide (DF01) was identified in a human hemofiltrate peptide library. It is derived from the h-part of the signal peptide sequence of hBPIFB1. In this thesis, the precursor protein and other h-regions of signal sequences from family members were analyzed towards anti-inflammatory properties. Further, a less cytotoxic and more water-soluble version of DF01, DF02 was generated. Both peptides form fibrillar- like structures which are important for its function. DF02 is self-delivering into cells and is able to specifically downregulate a certain set of type-I IFN ISGs, without affecting other inflammatory pathways. Phosphoproteome analyses suggests that DF02 acts via inhibition of STAT1 and STAT3 phosphorylation. As expected, DF02 amplifies viral replication but efficiently reduces inflammation in a type-I interferonopathy model. Further analysis will allow us to gain insights into the down-regulation of inflammatory processes by physiological peptides, potentially culminating in novel therapeutic approaches.