Innate and adaptive immune responses toward nanomedicines.

Since the commercialization of the first liposomes used for drug delivery, Doxil/Caelyx® and Myocet®, tremendous progress has been made in understanding interactions between nanomedicines and biological systems. Fundamental work at the interface of engineering and medicine has allowed nanomedicines to deliver therapeutic small molecules and nucleic acids more efficiently. While nanomedicines are used in oncology for immunotherapy or to deliver combinations of cytotoxics, the clinical successes of gene silencing approaches like patisiran lipid complexes (Onpattro®) have paved the way for a variety of therapies beyond cancer. In parallel, the global severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has highlighted the potential of mRNA vaccines to develop immunization strategies at unprecedented speed. To rationally design therapeutic and vaccines, chemists, materials scientists, and drug delivery experts need to better understand how nanotechnologies interact with the immune system. This review presents a comprehensive overview of the innate and adaptative immune systems and emphasizes the intricate mechanisms through which nanomedicines interact with these biological functions.

Deletion of S100a8 and S100a9 Enhances Skin Hyperplasia and Promotes the Th17 Response in Imiquimod-Induced Psoriasis.

High concentrations of the damage-associated molecular patterns S100A8 and S100A9 are found in skin and serum from patients suffering from psoriasis, an IL-17-related disease. Notably, although the expression of these proteins correlates with psoriatic disease severity, the exact function of S100A8 and S100A9 in psoriasis pathogenesis remains unclear. In this study, we investigated the role of S100A8 and S100A9 in psoriasis-associated skin hyperplasia and immune responses using S100a8-/- and S100a9-/- mice in an imiquimod-induced model of psoriasis. We found that S100a8-/- and S100a9-/- psoriatic mice exhibit worsened clinical symptoms relative to wild-type mice and increased expression of S100A9 and S100A8 proteins in keratinocytes, respectively. In addition, the loss of S100A8 enhances proliferation of keratinocytes and disrupts keratinocyte differentiation. We further detected elevated production of IL-17A and -F from CD4+ T cells in the absence of S100A8 and S100A9, as well as increased infiltration of neutrophils in the skin. In addition, treatment with anti-IL-17A and -F was found to reduce psoriasis symptoms and skin hyperplasia in S100a8-/- and S100a9-/- mice. These data suggest that S100A8 and S100A9 regulate psoriasis by inhibiting production of IL-17A and -F, thereby, to our knowledge, providing new insights into their biological functions.

Role of the complement cascade in the biological fate of liposomes in rodents.

Nanomedicines, including liposomes, have been used to improve the clinical efficacy and safety of drugs. In some liposomal formulations, a hydrophilic polymer coating of poly(ethylene glycol) (PEG) is used to increase the circulation time. Understanding the biological mechanisms responsible for the clearance of PEGylated and non-PEGylated nanomedicines is necessary to develop better-performing materials. The purpose of this work is to explore the role of complement in the elimination of intravenously administered liposomes (PEGylated and non-PEGylated) in mice and rats. Here, the complement cascade was depleted by intraperitoneal injections of cobra venom factor (CVF) 12 and 24 hours before the intravenous injection of radiolabeled liposomes. In both mice and rats, non-PEGylated liposomes showed faster elimination than PEGylated liposomes. At a lipid dose of 20 mg kg-1, the abrogation of the complement cascade (in CVF group) did not alter the circulation time of either PEGylated or non-PEGylated liposomes. In contrast, at lower doses (2 mg kg-1), animals treated with CVF had slightly higher levels of circulating liposomes, especially during the 24 hours pharmacokinetic studies. The complement cascade seems to govern the uptake of non-PEGylated liposomes by splenic B cells. Altogether, these results suggest that although PEGylated and non-PEGylated liposomes can activate complement, the impact of this cascade on their circulation time is minor and mostly perceivable at later phases of distribution. This work enlightens biological pathways responsible for in vivo clearance of liposomes and will help in orienting future research in elucidating the nano-bio interface.

Enhanced myelopoiesis and aggravated arthritis in S100a8-deficient mice.

Expressed strongly by myeloid cells, damage-associated molecular pattern (DAMP) proteins S100A8 and S100A9 are found in the serum of patients with infectious and autoimmune diseases. Compared to S100A9, the role of S100A8 is controversial. We investigated its biological activity in collagen-induced arthritis using the first known viable and fertile S100a8-deficient (S100a8-/-) mouse. Although comparable to the wild type (WT) in terms of lymphocyte distribution in blood and in the primary and secondary lymphoid organs, S100a8-/- mice had increased numbers of neutrophils, monocytes and dendritic cells in the blood and bone marrow, and these all expressed myeloid markers such as CD11b, Ly6G and CD86 more strongly. Granulocyte-macrophage common precursors were increased in S100a8-/- bone marrow and yielded greater numbers of macrophages and dendritic cells in culture. The animals also developed more severe arthritic disease leading to aggravated osteoclast activity and bone destruction. These findings were correlated with increased inflammatory cell infiltration and cytokine secretion in the paws. This study suggests that S100A8 is an anti-inflammatory DAMP that regulates myeloid cell differentiation, thereby mitigating the development of experimental arthritis.

Tumor-Associated Macrophages Enhance Tumor Hypoxia and Aerobic Glycolysis.

Tumor hypoxia and aerobic glycolysis are well-known resistance factors for anticancer therapies. Here, we demonstrate that tumor-associated macrophages (TAM) enhance tumor hypoxia and aerobic glycolysis in mice subcutaneous tumors and in patients with non-small cell lung cancer (NSCLC). We found a strong correlation between CD68 TAM immunostaining and PET 18fluoro-deoxyglucose (FDG) uptake in 98 matched tumors of patients with NSCLC. We also observed a significant correlation between CD68 and glycolytic gene signatures in 513 patients with NSCLC from The Cancer Genome Atlas database. TAM secreted TNFα to promote tumor cell glycolysis, whereas increased AMP-activated protein kinase and peroxisome proliferator-activated receptor gamma coactivator 1-alpha in TAM facilitated tumor hypoxia. Depletion of TAM by clodronate was sufficient to abrogate aerobic glycolysis and tumor hypoxia, thereby improving tumor response to anticancer therapies. TAM depletion led to a significant increase in programmed death-ligand 1 (PD-L1) expression in aerobic cancer cells as well as T-cell infiltration in tumors, resulting in antitumor efficacy by PD-L1 antibodies, which were otherwise completely ineffective. These data suggest that TAM can significantly alter tumor metabolism, further complicating tumor response to anticancer therapies, including immunotherapy. SIGNIFICANCE: These findings show that tumor-associated macrophages can significantly modulate tumor metabolism, hindering the efficacy of anticancer therapies, including anti-PD-L1 immunotherapy.

Regulation of TLR3 Activation by S100A9.

Recognition of viral dsRNA by endosomal TLR3 activates innate immune response during virus infection. Trafficking of TLR3 to the endolysosomal compartment arising from fusion of late endosome (LE) with lysosome is required for recognition and detection of pathogen associated molecular patterns, which results in activation of the TLR3-dependent signaling cascade. Existing knowledge about the mechanism(s) and cellular factor(s) governing TLR3 trafficking is limited. In the current study, we identified intracellular S100A9 protein as a critical regulator of TLR3 trafficking. S100A9 was required for maturation of TLR3 containing early endosome (EE) into LE, the compartment that fuses with lysosome to form the endolysosomal compartment. A drastic reduction in cytokine production was observed in S100A9-knockout (KO) primary macrophages following RNA virus infection and treatment of cells with polyinosinic-polycytidylic acid (polyIC; a dsRNA mimetic that acts as a TLR3 agonist). Mechanistic studies revealed colocalization and interaction of S100A9 with TLR3 following polyIC treatment. S100A9-TLR3 interaction was critical for maturation of TLR3 containing EE into LE because TLR3 could not be detected in the LE of polyIC-treated S100A9-KO macrophages. Subsequently, TLR3 failed to colocalize with its agonist (i.e., biotin-labeled polyIC) in S100A9-deficient macrophages. The in vivo physiological role of S100A9 was evident from loss of cytokine production in polyIC-treated S100A9-KO mice. Thus, we identified intracellular S100A9 as a regulator of TLR3 signaling and demonstrated that S100A9 functions during pre-TLR3 activation stages by facilitating maturation of TLR3 containing EE into LE.