ABSTRACT
Interleukin-10 (IL-10) is an anti-inflammatory cytokine that works through IL-10 receptor alpha subunit- and suppresses immune responses in many infectious diseases such as leishmaniasis as well as in cancer. Therefore, in order to restore the host-protective immune responses in such diseases, an antagonist to this cytokine is a pressing need. Herein, using phage peptide library display, we have identified a dodecameric peptide that functions as an antagonist to human IL-10 receptor in an IL-10-induced STAT3 phosphorylation assay. The peptide antagonist's ability to restore anti-leishmanial function in CD40-activated macrophages was also tested. We observed that the peptide reduced IL-10-induced STAT-3 phosphorylation and enhanced CD40-activated leishmanial functions in macrophages.
Subject(s)
Antiprotozoal Agents/pharmacology , Leishmania donovani/drug effects , Macrophages/drug effects , Oligopeptides/pharmacology , Peptide Library , Receptors, Interleukin-10/antagonists & inhibitors , Antiprotozoal Agents/immunology , Antiprotozoal Agents/metabolism , Binding, Competitive , CD40 Antigens/genetics , CD40 Antigens/immunology , Cell Line , Gene Expression/drug effects , High-Throughput Screening Assays , Host-Parasite Interactions/drug effects , Host-Parasite Interactions/immunology , Humans , Interleukin-10/immunology , Interleukin-10/metabolism , Leishmania donovani/physiology , Macrophages/immunology , Macrophages/parasitology , Models, Molecular , Oligopeptides/immunology , Oligopeptides/metabolism , Phosphorylation/drug effects , Protein Binding , Receptors, Interleukin-10/immunology , Receptors, Interleukin-10/metabolism , STAT3 Transcription Factor/antagonists & inhibitors , STAT3 Transcription Factor/genetics , STAT3 Transcription Factor/immunology , Signal Transduction/drug effectsABSTRACT
The antigen-presenting cellexpressed CD40 is implied in the regulation of counteractive immune responses such as induction of pro-inflammatory and anti-inflammatory cytokines interleukin (IL)12 and IL-10, respectively. The mechanism of this duality in CD40 function remains unknown. Here, we investigated whether such duality depends on ligand binding. Based on CD40 binding, we identifed two dodecameric peptides, peptide-7 and peptide-19, from the phage peptide library. Peptide-7 induces IL-10 and increases Leishmania donovani infection in macrophages, whereas peptide-19 induces IL-12 and reduces L. donovani infection. CD40-peptide interaction analyses by surface plasmon resonance and atomic force microscopy suggest that the functional differences are not associated with the studied interaction parameters. The molecular dynamic simulation of the CD40-peptides interaction suggests that these two peptides bind to two different places on CD40. Thus, we suggest for the first time that differential binding of the ligands imparts functional duality to CD40.
