High-throughput screening for small molecule inhibitors of the type-I interferon signaling pathway

Interferons (IFNs) are cytokines with fundamental roles in resistance to infections, cancer and other diseases. Type-I IFNs, interferon α (IFN-α) and interferon β (IFN-β), act through a shared receptor complex (IFNAR) comprised of IFNAR1 and IFNAR2 subunits. Binding of type-I IFN to IFNAR1 will robustly activate Janus activated kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway. Aberrant activation of the type-I IFN response results in a spectrum of disorders called interferonopathies. The purpose of this research is to develop an assay for high-throughput screening (HTS) of small molecule inhibitors of the type-I IFN signaling pathway. Inhibition of type-I IFN signaling can be beneficial in terms of therapeutic use and understanding the underlying mechanism of action. We report here a HTS campaign with the secreted embryonic alkaline phosphatase (SEAP) reporter gene assay against 32,000 compounds which yielded 25 confirmed hits. These compounds were subsequently characterized for their cytotoxicity, effects on STAT phosphorylation and activities in IFN regulatory factor (IRF) transcription.

A new nucleic acid-based agent inhibits cytotoxic T lymphocyte-mediated immune disorders

BACKGROUND

Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and graft-versus-host disease (GVHD) are distinct immune reactions elicited by drugs or allogeneic antigens; however, they share a pathomechanism with the activation of cytotoxic T lymphocytes (CTLs). CTLs produce cytotoxic proteins, cytokines, chemokines, or immune alarmins, such as granulysin (GNLY), leading to the extensive tissue damage and systemic inflammation seen in patients with SJS/TEN or GVHD. Currently, there is no effective therapeutic agent specific for CTL-mediated immune disorders.

OBJECTIVES

By targeting GNLY(+) CTLs, we aimed to develop a nucleic acid-based agent consisting of an anti-CD8 aptamer with GNLY small interfering RNA (siRNA).

METHODS

We performed systematic evolution of ligands using exponential enrichment to select and identify effective anti-CD8 aptamers. We developed an aptamer-siRNA chimera using a "sticky bridge" method by conjugating the aptamer with siRNA. We analyzed the inhibitory effects of the aptamer-siRNA chimera on CTL responses in patients with SJS/TEN or GVHD.

RESULTS

We identified a novel DNA aptamer (CD8AP17s) targeting CTLs. This aptamer could be specifically internalized into human CTLs. We generated the CD8AP17s aptamer-GNLY siRNA chimera, which showed a greater than 79% inhibitory effect on the production of GNLY by drug/alloantigen-activated T cells. The CD8AP17s aptamer-GNLY siRNA chimera decreased cytotoxicity in in vitro models of both SJS/TEN (elicited by drug-specific antigen) and GVHD (elicited by allogeneic antigens).

CONCLUSIONS

Our results identified a new nucleic acid-based agent (CD8 aptamer-GNLY siRNA chimera) that can significantly inhibit CTL-mediated drug hypersensitivity, such as that seen in patients with SJS/TEN, as well as the alloreactivity seen in patients with GVHD. This study provides a novel therapeutic strategy for CTL-mediated immune disorders.