CD47 EnhancesIn VivoFunctionality of Artificial Antigen-Presenting Cells

Abstract

Purpose Artificial Antigen-Presenting Cells, aAPC, have successfully been used to stimulate antigen-specific T cell responses in vitro as well as in vivo. While aAPC compare favorable to autologous dendritic cells in vitro, their effect in vivo might be diminished through rapid clearance by macrophages. Therefore, to prevent uptake and minimize clearance of aAPC by macrophages, and thereby increasing in vivo functionality, we investigated the efficiency of “don’t eat me” three-signal aAPC compared to classical two-signal aAPC. Experimental Design To generate “don’t eat me” aAPC, CD47 was additionally immobilized onto classical aAPC (aAPCCD47+). aAPC and aAPCCD47+ were analyzed in in vitro human primary T cell and macrophage co-cultures. In vivo efficiency was compared in a NOD/SCID T cell proliferation and a B16-SIY melanoma model. Results This study demonstrates that aAPCCD47+ in co-culture with human macrophages show a CD47 concentration dependent inhibition of phagocytosis, while their ability to generate and expand antigen-specific T cells was not affected. Furthermore, aAPCCD47+ generated T cells displayed equivalent killing abilities and polyfunctionality when compared to aAPC generated T cells. In addition, in vivo studies demonstrated an enhanced stimulatory capacity and tumor inhibition of aAPCCD47+ over normal aAPC in conjunction with diverging bio-distribution in different organs. Conclusion Our data for the first time show that aAPC functionalized with CD47 maintain their stimulatory capacity in vitro and demonstrate enhanced in vivo efficiency. Thus this next generation aAPCCD47+ have a unique potential to enhance the application of the aAPC technology for future immunotherapy approaches.

<p>PEGylated and CD47-conjugated nanoellipsoidal artificial antigen-presenting cells minimize phagocytosis and augment anti-tumor T-cell responses</p>

“…In the nonspecific cytolysis controls, SPCs from all groups showed ,11% of baseline cytolysis against SP2/0 cells (Figure 11). Different from the previous studies of SaAPCs, 10,16 CD47-modified SaAPCs, 30 and SaAPCs, 28 the present study initially illustrated the EaAPC PEG and EaAPC PEG/CD47 . The results from in vivo experiments demonstrated that the superimposed or synergistic effects of ellipsoidal stretch, PEGylation, and self-marker CD47 conjugation onto nano-aAPC tailored much stronger in vivo functionality of the EaAPC PEG/CD47 to expand antigen-specific CTLs, facilitate their local infiltration, and eventually inhibit tumor growth, when compared to the control aAPCs with a function order Figure 8 eaaPc Peg/cD47 markedly augmented melanoma antigen-specific CTL responses in melanoma-bearing mice.…”

“…28,29 Meanwhile, the CD47-conjugated spherical nano-aAPCs have also been developed with the enhanced effects of anti-phagocytosis and tumor inhibition. 30 In this study, PEGylation, CD47 conjugation, and ellipsoidal stretch were integrated into the generation of new "stealth" nano-aAPCs with microscale contact surface to minimize internalization and augment anti-tumor CTL responses in melanoma-bearing mice. PLGA, a biocompatible, biodegradable, and nontoxic polymer widely used in drug and vaccine delivery systems in human, [31][32][33] was employed to fabricate the spherical NPs and then was further stretched to the ellipsoidal NPs, followed by surface modification with PEGylation and surface co-coupling with H-2K b /TRP2 180-188 -Ig dimers, anti-CD28, and CD47-Fc.…”

Direct modulation of myelin-autoreactive CD4⁺ and CD8⁺ T cells in EAE mice by a tolerogenic nanoparticle co-carrying myelin peptide-loaded major histocompatibility complexes, CD47 and multiple regulatory molecules

“…The results are also in agreement with the finding from Bruns et al that CD47 increased the penetration and retention of PLGA-NPs in the damaged brain, thus enhancing the in vivo functionality of artificial APCs. 58 Here, the 217 nm tNPs were decorated with CD47-Fc, which led to a longer retention time in vivo and much fewer co-localizations with macrophages and DCs than the CD47 − tNPs, implying that CD47 molecules onto tNPs may minimize the engulfment of tNPs by phagocytes as expected. But we cannot eliminate the possibility of endocytosis and phagocytosis occurring in vivo.…”

The use of CD47-modified biomaterials to mitigate the immune response

“…Similar results were seen when artificial antigen presenting cells, fabricated from epoxy beads were co-cultured with macrophages. 76 This study demonstrated that phagocytosis inhibition was CD47 concentration dependent. Additionally, it was shown that CD47 did not interfere with the ability to expand antigen-specific T cells.…”