A Bacterial and Ganglioside-based Nanoparticle Initiates Reprogramming of Macrophages and Promotes Antitumor Phenotypes.

Macrophages represent the most abundant immune component of the tumor microenvironment and often exhibit protumorigenic (M2-like) phenotypes that contribute to disease progression. Despite their generally accepted protumorigenic role, macrophages can also display tumoricidal (or M1-like) behavior, revealing that macrophages can be functionally reprogrammed, depending on the cues received within the tumor microenvironment. Moreover, such plasticity may be achieved by pharmacologic or biologic interventions. To that end, we previously demonstrated that a novel immunomodulator termed the "very small size particle" (VSSP) facilitates maturation of dendritic cells and differentiation of myeloid-derived suppressor cells to APCs with reduced suppressive activity in cancer models. VSSP was further shown to act in the bone marrow to drive the differentiation of progenitors toward monocytes, macrophages, and dendritic cells during emergency myelopoiesis. However, the underlying mechanisms for VSSP-driven alterations in myeloid differentiation and function remained unclear. In this study, in mouse models, we focused on macrophages and tested the hypothesis that VSSP drives macrophages toward M1-like functional states via IRF8- and PU.1-dependent mechanisms. We further hypothesized that such VSSP-mediated actions would be accompanied by enhanced antitumor responses. Overall, we showed that (1) VSSP drives naive or M2-derived macrophages to M1-like states, (2) the M1-like state induced by VSSP occurs via IRF8- and PU.1-dependent mechanisms, and (3) single-agent VSSP induces an antitumor response that is accompanied by alterations in the intratumoral myeloid compartment. These results provide a deeper mechanistic underpinning of VSSP and strengthen its use to drive M1-like responses in host defense, including cancer.

Molecular reshaping of phage-displayed Interleukin-2 at beta chain receptor interface to obtain potent super-agonists with improved developability profiles.

Interleukin-2 (IL-2) engineered versions, with biased immunological functions, have emerged from yeast display and rational design. Here we reshaped the human IL-2 interface with the IL-2 receptor beta chain through the screening of phage-displayed libraries. Multiple beta super-binders were obtained, having increased receptor binding ability and improved developability profiles. Selected variants exhibit an accumulation of negatively charged residues at the interface, which provides a better electrostatic complementarity to the beta chain, and faster association kinetics. These findings point to mechanistic differences with the already reported superkines, characterized by a conformational switch due to the rearrangement of the hydrophobic core. The molecular bases of the favourable developability profile were tracked to a single residue: L92. Recombinant Fc-fusion proteins including our variants are superior to those based on H9 superkine in terms of expression levels in mammalian cells, aggregation resistance, stability, in vivo enhancement of immune effector responses, and anti-tumour effect.

VSSP-activated macrophages mediate senescence and tumor inhibition in a preclinical model of advanced prostate cancer.

Androgen deprivation therapy (ADT) is a standard therapy for prostate cancer (PCa). Though disseminated disease is initially sensitive to ADT, an important fraction of the patients progresses to castration-resistant prostate cancer (CRPC). For this reason, the identification of novel effective therapies for treating CRPC is needed. Immunotherapeutic strategies focused on macrophages as antitumor effectors, directly enhancing their tumoricidal potential at the tumor microenvironment or their adoptive transfer after ex vivo activation, have arisen as promising therapies in several cancer types. Despite several approaches centered on the activation of tumor-associated macrophages (TAMs) in PCa are under investigation, to date there is no evidence of clinical benefit in patients. In addition, the evidence of the effectiveness of macrophage adoptive transfer on PCa is poor. Here we find that VSSP, an immunomodulator of the myeloid system, decreases TAMs and inhibits prostatic tumor growth when administered to castrated Pten-deficient prostate tumor-bearing mice. In mice bearing castration-resistant Ptenpc-/-; Trp53pc-/- tumors, VSSP administration showed no effect. Nevertheless, adoptive transfer of macrophages activated ex vivo with VSSP inhibited Ptenpc-/-; Trp53pc-/- tumor growth through reduction of angiogenesis and tumor cell proliferation and induction of senescence. Taken together, our results highlight the rationale of exploiting macrophage functional programming as a promising strategy for CRPC therapy, with particular emphasis on ex vivo-activated proinflammatory macrophage adoptive transfer. Video abstract.

Evidence of SARS-CoV-2 infection in postmortem lung, kidney, and liver samples, revealing cellular targets involved in COVID-19 pathogenesis.

There is an urgent need to understand severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-host interactions involved in virus spread and pathogenesis, which might contribute to the identification of new therapeutic targets. In this study, we investigated the presence of SARS-CoV-2 in postmortem lung, kidney, and liver samples of patients who died with coronavirus disease (COVID-19) and its relationship with host factors involved in virus spread and pathogenesis, using microscopy-based methods. The cases analyzed showed advanced stages of diffuse acute alveolar damage and fibrosis. We identified the SARS-CoV-2 nucleocapsid (NC) in a variety of cells, colocalizing with mitochondrial proteins, lipid droplets (LDs), and key host proteins that have been implicated in inflammation, tissue repair, and the SARS-CoV-2 life cycle (vimentin, NLRP3, fibronectin, LC3B, DDX3X, and PPARγ), pointing to vimentin and LDs as platforms involved not only in the viral life cycle but also in inflammation and pathogenesis. SARS-CoV-2 isolated from a patient´s nasal swab was grown in cell culture and used to infect hamsters. Target cells identified in human tissue samples included lung epithelial and endothelial cells; lipogenic fibroblast-like cells (FLCs) showing features of lipofibroblasts such as activated PPARγ signaling and LDs; lung FLCs expressing fibronectin and vimentin and macrophages, both with evidence of NLRP3- and IL1ß-induced responses; regulatory cells expressing immune-checkpoint proteins involved in lung repair responses and contributing to inflammatory responses in the lung; CD34+ liver endothelial cells and hepatocytes expressing vimentin; renal interstitial cells; and the juxtaglomerular apparatus. This suggests that SARS-CoV-2 may directly interfere with critical lung, renal, and liver functions involved in COVID-19-pathogenesis.