Carlos Pérez-Medina

INTRODUCTION: A subset of Alzheimer's disease (AD) patients exhibits a procoagulant state that remains undiagnosed despite available treatments. We developed positron emission tomography (PET) strategies to in vivo detect cerebral microthrombi in TgCRND8 mice. METHODS: PET was performed with a fibrin‐binding probe (FBP) in TgCRND8 and wild‐type mice using a zirconium‐89–radiolabeled and a click‐chemistry pre‐targeted gallium‐68 radiotracer. Platelet content was assessed in post mortem brain tissue from AD patients and TgCRND8 mice, and evaluated by PET using a CD41 pre‐targeted gallium‐68 nanoradiotracer. RESULTS: Cerebral FBP uptake differentiated TgCRND8 from wild‐type mice, particularly ex vivo and with advancing age. Cerebral fibrin burden correlated with platelet content in AD patients, and elevated cerebral platelet burden in TgCRND8 mice was confirmed in post mortem tissue and in vivo by PET. DISCUSSION: Our findings support PET‐based detection of AD‐associated cerebral microthrombi and the development of imaging biomarkers to stratify AD patients by procoagulant status and inform personalized therapies.

Hematopoietic bone marrow progenitors are increasingly implicated as an origin of immunosuppression in cancer. We have previously shown that trained immunity induction using nanomedicine potentiates checkpoint blockade therapy. Here, we studied how this approach’s induction of trained immunity systemically overcomes the immunosuppressive tumor microenvironment. We found changes in the tumor microenvironment to mirror functional changes in the hematopoietic system in a melanoma mouse model. Single cell sequencing methods disclosed a shift in the tumor-associated macrophage population from immunosuppressive to antitumorigenic. Uniquely, a trained immunity and checkpoint blockade combination therapy mobilized natural killer cells which, in conjunction with the functional changes in the myeloid cell compartment, effectively activated T cells. Last, we established the effectiveness of our approach in mouse models of breast, lung, and pancreatic cancer. Collectively, our data show that the systemic induction of trained immunity rebalances the immune system for effective checkpoint blockade therapy.

Background and aims: Lipids play a critical role in atherosclerosis. Low-density lipoprotein (LDL)-cholesterol and certain lipid classes like sphingomyelins are associated with inflammation and poor cardiovascular outcomes. Phosphatidylserine (PS), on the other hand, is a negatively charged anti-inflammatory phospholipid class involved in efferocytosis. In this study, we sought to investigate its anti-atherosclerotic properties through a combination of complementary human lipidomics analyses, in vitro assays and in vivo experiments in Apoe ^-/- mice. Methods: Human lipidomics studies were performed on the 300OB cohort comprising 300 obese and overweight individuals at risk of cardiovascular disease. In vitro assays were carried out using human monocytes and macrophages, and in vivo experiments included histopathological, immunophenotyping and single-cell transcriptomic analyses. Results: In humans, we identified PS as an anti-inflammatory and atheroprotective biomarker. Hence, we developed a high-density lipoprotein (HDL)-like formulation enriched in PS to exploit its properties in a targeted fashion in mice. In vitro , this formulation potently inhibited inflammatory cytokine production on human myeloid cells. Our in-depth in vivo experiments provided evidence of the formulation’s potent plaque-stabilizing and anti-inflammatory actions. These effects were mediated by a shift in the monocyte/macrophage compartment toward homeostatic/repairing phenotypes. Conclusions: Collectively, our results demonstrate that HDL-associated PS potently suppresses inflammation and atheroprogression, and holds promise as a viable approach to improve immunomodulatory therapies.

Immunoparalysis is a compensatory and persistent anti-inflammatory response to trauma, sepsis or another serious insult, which increases the risk of opportunistic infections, morbidity and mortality. Here, we show that in cultured primary human monocytes, interleukin-4 (IL4) inhibits acute inflammation, while simultaneously inducing a long-lasting innate immune memory named trained immunity. To take advantage of this paradoxical IL4 feature in vivo, we developed a fusion protein of apolipoprotein A1 (apoA1) and IL4, which integrates into a lipid nanoparticle. In mice and non-human primates, an intravenously injected apoA1-IL4-embedding nanoparticle targets myeloid-cell-rich haematopoietic organs, in particular, the spleen and bone marrow. We subsequently demonstrate that IL4 nanotherapy resolved immunoparalysis in mice with lipopolysaccharide-induced hyperinflammation, as well as in ex vivo human sepsis models and in experimental endotoxemia. Our findings support the translational development of nanoparticle formulations of apoA1-IL4 for the treatment of patients with sepsis at risk of immunoparalysis-induced complications.

Macrophages play a central role in the pathogenesis of atherosclerosis. The inflammatory properties of these cells are dictated by their metabolism, of which the mechanistic target of rapamycin (mTOR) signaling pathway is a key regulator. Using myeloid cell–specific nanobiologics in apolipoprotein E–deficient (Apoe^−/−) mice, we found that targeting the mTOR and ribosomal protein S6 kinase-1 (S6K1) signaling pathways rapidly diminished plaque macrophages’ inflammatory activity. By investigating transcriptome modifications, we identified Psap, a gene encoding the lysosomal protein prosaposin, as closely related with mTOR signaling. Subsequent in vitro experiments revealed that Psap inhibition suppressed both glycolysis and oxidative phosphorylation. Transplantation of Psap^−/− bone marrow to low-density lipoprotein receptor knockout (Ldlr^−/−) mice led to a reduction in atherosclerosis development and plaque inflammation. Last, we confirmed the relationship between PSAP expression and inflammation in human carotid atherosclerotic plaques. Our findings provide mechanistic insights into the development of atherosclerosis and identify prosaposin as a potential therapeutic target.

Modular production methods allow the efficient development of nanoimmunotherapies targeting the innate immune system.

Multimodal intravital microscopy and PET imaging of S. aureus endocarditis can monitor adjuvant immunotherapy in mice and pigs.

Although the first nanomedicine was clinically approved more than two decades ago, nanoparticles’ (NP) in vivo behavior is complex and the immune system’s role in their application remains elusive. At present, only passive-targeting nanoformulations have been clinically approved, while more complicated active-targeting strategies typically fail to advance from the early clinical phase stage. This absence of clinical translation is, amongst others, due to the very limited understanding for in vivo targeting mechanisms. Dynamic in vivo phenomena such as NPs’ real-time targeting kinetics and phagocytes’ contribution to active NP targeting remain largely unexplored. To better understand in vivo targeting, monitoring NP accumulation and distribution at complementary levels of spatial and temporal resolution is imperative. Here, we integrate in vivo positron emission tomography / computed tomography (PET/CT) imaging with intravital microscopy (IVM) and flow cytometric analyses to study αvβ3-integrin-targeted cyclic arginine-glycine-aspartate (cRGD) decorated liposomes and oil-in-water nanoemulsions in tumor mouse models. We observed that ligand-mediated accumulation in cancerous lesions is multifaceted and identified “NP hitchhiking” with phagocytes to contribute considerably to this intricate process. We anticipate that this understanding can facilitate rational improvement of nanomedicine applications and that immune cell-NP interactions can be harnessed to develop clinically viable nanomedicine-based immunotherapies.

Cardiovascular disease due to atherosclerosis is still the main cause of morbidity and mortality worldwide. This disease is a complex systemic disorder arising from a network of pathological processes within the arterial vessel wall, and, outside of the vasculature, in the hematopoietic system and organs involved in metabolism. Recent years have seen tremendous efforts in the development and validation of quantitative imaging technologies for the noninvasive evaluation of patients with atherosclerotic cardiovascular disease. Specifically, the advent of combined positron emission tomography and magnetic resonance imaging scanners has opened new exciting opportunities in cardiovascular imaging. In this review, we will describe how combined positron emission tomography/magnetic resonance imaging scanners can be leveraged to evaluate atherosclerotic cardiovascular disease at the whole-body level, with specific focus on preclinical animal models of disease, from mouse to nonhuman primates. We will broadly describe 3 major areas of application: (1) vascular imaging, for advanced atherosclerotic plaque phenotyping and evaluation of novel imaging tracers or therapeutic interventions; (2) assessment of the ischemic heart and brain; and (3) whole-body imaging of the hematopoietic system. Finally, we will provide insights on potential novel technical developments which may further increase the relevance of integrated positron emission tomography/magnetic resonance imaging in preclinical atherosclerosis studies.

Ischaemic heart disease evokes a complex immune response. However, tools to track the systemic behaviour and dynamics of leukocytes non-invasively in vivo are lacking. Here, we present a multimodal hot-spot imaging approach using an innovative high-density lipoprotein-derived nanotracer with a perfluoro-crown ether payload (¹⁹F-HDL) to allow myeloid cell tracking by ¹⁹F magnetic resonance imaging. The ¹⁹F-HDL nanotracer can additionally be labelled with zirconium-89 and fluorophores to detect myeloid cells by in vivo positron emission tomography imaging and optical modalities, respectively. Using our nanotracer in atherosclerotic mice with myocardial infarction, we observed rapid myeloid cell egress from the spleen and bone marrow by in vivo ¹⁹F-HDL magnetic resonance imaging. Concurrently, using ex vivo techniques, we showed that circulating pro-inflammatory myeloid cells accumulated in atherosclerotic plaques and at the myocardial infarct site. Our multimodality imaging approach is a valuable addition to the immunology toolbox, enabling the study of complex myeloid cell behaviour dynamically.