Multivalent, Soluble Nano-Self Peptides Increase Phagocytosis of Antibody-Opsonized Targets while Suppressing “Self” Signaling

Abstract

Macrophages engulf "foreign" cells and particles, but phagocytosis of healthy cells and cancer cells is inhibited by expression of the ubiquitous membrane protein CD47 which binds SIRPα on macrophages to signal "self". Motivated by some clinical efficacy of anti-CD47 against liquid tumors and based on past studies of CD47-derived polypeptides on particles that inhibited phagocytosis of the particles, here we design soluble, multivalent peptides to bind and block SIRPα. Bivalent and tetravalent nano-Self peptides prove more potent (K eff ∼ 10 nM) than monovalent 8-mers as agonists for phagocytosis of antibody opsonized cells, including cancer cells. Multivalent peptides also outcompete soluble CD47 binding to human macrophages, consistent with SIRPα binding, and the peptides suppress phosphotyrosine in macrophages, consistent with inhibition of SIRPα's "self" signaling. Peptides exhibit minimal folding, but functionality suggests an induced fit into SIRPα's binding pocket. Pre-clinical studies in mice indicate safety, with no anemia that typifies clinical infusions of anti-CD47. Multivalent nano-Self peptides thus constitute an alternative approach to promoting phagocytosis of "self", including cancer cells targeted clinically.

Human CD47-Derived Cyclic Peptides Enhance Engulfment of mAb-Targeted Melanoma by Primary Macrophages

“…Scrambled nS-X peptide does not affect opsonization-driven eating of the two B16 lines. The maximum levels of eating with soluble nS-F, nS-F-Cyc, and nS-Cyc are consistent with disruption of both trans and cis interactions between CD47−SIRPα on the macrophages, per previous studies showing suppression of a basal level of inhibitory "don't eat me" signal; 15,19 nS peptides are unlikely to bind and inhibit SIRPα on WT B16 cells because excess peptide is washed away in our assay before adding B16s to the macrophages. Regardless, the increased phagocytosis follows the trend cyclic > wildtype > scrambled activity, and though the mutant Phe residue makes linear > wildtype, it has no effect on the cyclic peptide.…”

“…14 We have recently demonstrated disruption of the CD47−SIRPα axis with potent linear nano-Self (nS) peptides that promote macrophage phagocytosis of opsonized cancer cells. 15 In this study, the activity of cyclic nano-Self (nS-Cyc) variants that share the same core sequences as their linear counterparts are tested and compared to linear nS peptides. We find that macrophage engulfment of opsonized cells is enhanced in the presence of nS-Cyc peptide with wildtype sequence, particularly compared to the linear form.…”

Colostral immunity of piglets to the Aujeszky disease virus in case of active immunization sows

“…У свою чергу, специфічний імунітет активується за дії антигенного подразника. Механізм специфічного імунного захисту обумовлюється взаємодією специфічних антитіл з антигенами збудника, подальшою їх опсонізацією та елімінацією з організму шляхом поглинання і фагоцитозу імунними клітинами (Jalil et al, 2020).…”

A siRNA-Assisted Assembly Strategy to Simultaneously Suppress “Self” and Upregulate “Eat-Me” Signals for Nanoenabled Chemo-Immunotherapy

“…As innate immune cells and antigen-presenting cells, macrophages are one of the first lines of defense in the innate immune system and can directly engulf cancer cells, thus playing a critical role in preventing tumor progression. − However, tumor cells usually upregulate their expression of CD47, which interacts with its ligand, signal regulatory protein-α (SIRPα), , on the surface of macrophages to provide a “self” signal, resulting in escape from recognition and phagocytosis by macrophages. − Blocking CD47 can suppress this “self” signal and reactivate macrophages to phagocytose tumor cells. − However, accumulating evidence has demonstrated that blocking the “self” signal of the CD47-SIRPα interaction alone is insufficient to realize engulfment of the target cell, , and the prophagocytic signal (“eat-me”) calreticulin (CRT) can evidently enhance phagocytosis after binding its macrophage receptor, low-density lipoprotein-related protein (LRP). , Accordingly, phagocytic potency was shown to depend on both the blockade of antiphagocytic “self” signals and exposure of prophagocytic “eat-me” signals. , Therefore, simultaneous suppression of CD47 and upregulation of CRT on the tumor cell surface would be a promising strategy to promote macrophage phagocytosis and may eventually improve macrophage-based cancer immunotherapy.…”

“…A s innate immune cells and antigen-presenting cells, macrophages are one of the first lines of defense in the innate immune system and can directly engulf cancer cells, thus playing a critical role in preventing tumor progression. 1−3 However, tumor cells usually upregulate their expression of CD47, which interacts with its ligand, signal regulatory protein-α (SIRPα), 4,5 on the surface of macrophages to provide a "self" signal, 6 resulting in escape from recognition and phagocytosis by macrophages. 7−10 Blocking CD47 can suppress this "self" signal and reactivate macrophages to phagocytose tumor cells.…”