Macropinocytosis in phagocytes: regulation of MHC class-II-restricted antigen presentation in dendritic cells

Plasma membrane abundance dictates phagocytic capacity and functional cross-talk in myeloid cells

Professional phagocytes like neutrophils and macrophages tightly control what they consume, how much they consume, and when they move after cargo uptake. We show that plasma membrane abundance is a key arbiter of these cellular behaviors. Neutrophils and macrophages lacking the G protein subunit Gβ4 exhibited profound plasma membrane expansion, accompanied by marked reduction in plasma membrane tension. These biophysical changes promoted the phagocytosis of bacteria, fungus, apoptotic corpses, and cancer cells. We also found that Gβ4-deficient neutrophils are defective in the normal inhibition of migration following cargo uptake. Sphingolipid synthesis played a central role in these phenotypes by driving plasma membrane accumulation in cells lacking Gβ4. In Gβ4 knockout mice, neutrophils not only exhibited enhanced phagocytosis of inhaled fungal conidia in the lung but also increased trafficking of engulfed pathogens to other organs. Together, these results reveal an unexpected, biophysical control mechanism central to myeloid functional decision-making.

Pathways for macrophage uptake of cell-free circular RNAs

Circular RNAs (circRNAs) are stable RNAs present in cell-free RNA, which may comprise cellular debris and pathogen genomes. Here, we investigate the phenomenon and mechanism of cellular uptake and intracellular fate of exogenous circRNAs. Human myeloid cells and B cells selectively internalize extracellular circRNAs. Macrophage uptake of circRNA is rapid, energy dependent, and saturable. CircRNA uptake can lead to translation of encoded sequences and antigen presentation. The route of internalization influences immune activation after circRNA uptake, with distinct gene expression programs depending on the route of RNA delivery. Genome-scale CRISPR screens and chemical inhibitor studies nominate macrophage scavenger receptor MSR1, Toll-like receptors, and mTOR signaling as key regulators of receptor-mediated phagocytosis of circRNAs, a dominant pathway to internalize circRNAs in parallel to macropinocytosis. These results suggest that cell-free circRNA serves as an "eat me" signal and danger-associated molecular pattern, indicating orderly pathways of recognition and disposal.

Dendritic Cells: A Bridge between Tolerance Induction and Cancer Development in Transplantation Setting

Dendritic cells (DCs) are a heterogeneous group of antigen-presenting cells crucial for fostering allograft tolerance while simultaneously supporting host defense against infections and cancer. Within the tumor microenvironment, DCs can either mount an immune response against cancer cells or foster immunotolerance, presenting a dual role. In immunocompromised individuals, posttransplant malignancies pose a significant health concern, with DCs serving as vital players in immune responses against cancer cells. Both recipient- and donor-derived DCs play a critical role in the rejection process, infiltrating the transplanted organ and sustaining T-cell responses. The use of immunosuppressive drugs represents the predominant approach to control this immunological barrier in transplanted organs. Evidence has shed light on the immunopharmacology of these drugs and novel strategies for manipulating DCs to promote allograft survival. Therefore, comprehending the mechanisms underlying this intricate microenvironment and the effects of immunosuppressive therapy on DCs is crucial for developing targeted therapies to reduce graft failure rates. This review will delve into the fundamental immunobiology of DCs and provide a detailed exploration of their clinical significance concerning alloimmune responses and posttransplant malignancies.

Neoantigen Identification and Dendritic Cell-Based Vaccines for Lung Cancer Immunotherapy

Immunotherapies can treat many cancers, including difficult-to-treat cases such as lung cancer. Due to its tolerability, long-lasting therapeutic responses, and efficacy in a wide spectrum of patients, immunotherapy can also help to treat lung cancer, which has few treatment choices. Tumor-specific antigens (TSAs) for cancer vaccinations and T-cell therapies are difficult to discover. Neoantigens (NeoAgs) from genetic mutations, irregular RNA splicing, protein changes, or viral genetic sequences in tumor cells provide a solution. NeoAgs, unlike TSAs, are non-self and can cause an immunological response. Next-generation sequencing (NGS) and bioinformatics can swiftly detect and forecast tumor-specific NeoAgs. Highly immunogenic NeoAgs provide personalized or generalized cancer immunotherapies. Dendritic cells (DCs), which originate and regulate T-cell responses, are widely studied potential immunotherapeutic therapies for lung cancer and other cancers. DC vaccines are stable, reliable, and safe in clinical trials. The purpose of this article is to evaluate the current status, limitations, and prospective clinical applications of DC vaccines, as well as the identification and selection of major histocompatibility complex (MHC) class I and II genes for NeoAgs. Our goal is to explain DC biology and activate DC manipulation to help researchers create extremely potent cancer vaccines for patients.

Mechanical stretch regulates macropinocytosis in Hydra vulgaris

Cells rely on a diverse array of engulfment processes to sense, exploit, and adapt to their environments. Among these, macropinocytosis enables indiscriminate and rapid uptake of large volumes of fluid and membrane, rendering it a highly versatile engulfment strategy. Much of the molecular machinery required for macropinocytosis has been well established, yet how this process is regulated in the context of organs and organisms remains poorly understood. Here, we report the discovery of extensive macropinocytosis in the outer epithelium of the cnidarian Hydra vulgaris. Exploiting Hydra's relatively simple body plan, we developed approaches to visualize macropinocytosis over extended periods of time, revealing constitutive engulfment across the entire body axis. We show that the direct application of planar stretch leads to calcium influx and the inhibition of macropinocytosis. Finally, we establish a role for stretch-activated channels in inhibiting this process. Together, our approaches provide a platform for the mechanistic dissection of constitutive macropinocytosis in physiological contexts and highlight a potential role for macropinocytosis in responding to cell surface tension.

Mitochondria and diabetes: insights and potential therapies

INTRODUCTION

Type 2 diabetes (T2D) presents significant global health and economic challenges, contributing to complications such as stroke, cardiovascular disease, kidney dysfunction, and cancer. The current review explores the crucial role of mitochondria, essential for fuel metabolism, in diabetes-related processes.

AREAS COVERED

Mitochondrial deficits impact insulin-resistant skeletal muscles, adipose tissue, liver, and pancreatic β-cells, affecting glucose and lipid balance. Exercise emerges as a key factor in enhancing mitochondrial function, thereby reducing insulin resistance. Additionally, the therapeutic potential of mitochondrial uncoupling, which generates heat instead of ATP, is discussed. We explore the intricate link between mitochondrial function and diabetes, investigating genetic interventions to mitigate diabetes-related complications. We also cover the impact of insulin deficiency on mitochondrial function, the role of exercise in addressing mitochondrial defects in insulin resistance, and the potential of mitochondrial uncoupling. Furthermore, a comprehensive analysis of Mitochondrial Replacement Therapies (MRT) techniques is presented.

EXPERT OPINION

MRTs hold promise in preventing the transmission of mitochondrial disease. However, addressing ethical, regulatory, and technical considerations is crucial. Integrating mitochondrial-based treatments requires a careful balance between innovation and safety. Ethical dimensions and regulatory aspects of MRT are examined, emphasizing collaborative efforts for the responsible advancement of human health.

TRP Ion Channels in Immune Cells and Their Implications for Inflammation

The transient receptor potential (TRP) ion channels act as cellular sensors and mediate a plethora of physiological processes, including somatosensation, proliferation, apoptosis, and metabolism. Under specific conditions, certain TRP channels are involved in inflammation and immune responses. Thus, focusing on the role of TRPs in immune system cells may contribute to resolving inflammation. In this review, we discuss the distribution of five subfamilies of mammalian TRP ion channels in immune system cells and how these ion channels function in inflammatory mechanisms. This review provides an overview of the current understanding of TRP ion channels in mediating inflammation and may offer potential avenues for therapeutic intervention.

IgG and insulin enhance endocytosis in THP-1 cells via activation of phosphatidylinositol 3-kinase (PI3K)

Extracellular substances, including membrane-impermeable nutrients, are taken up by cells via endocytosis. Endocytosis is also an important pathway for antigen uptake by antigen-presenting cells such as monocytes, macrophages, dendritic cells, and B cells. In this study, we investigated the regulatory mechanism of endocytosis in THP-1 cells, a monocytic leukemia cell line. We analyzed the effect of IgG and insulin, which are abundant in the serum and play important roles in immunity and metabolism, respectively, on the endocytic activity in THP-1 cells. The results indicated that IgG and insulin enhance pinocytosis and phagocytosis via activation of phosphatidylinositol 3-kinase (PI3K). Our results suggest that IgG and insulin contribute to the maintenance of endocytic activity and are important for antigen presentation and nutrient uptake.

A Manifold-Based Framework for Studying the Dynamics of the Vaginal Microbiome

The vaginal bacterial community plays a crucial role in preventing infections. The composition of this community can be classified into five main groups, termed community state types (CSTs). Four of these CSTs, which are primarily consisted of Lactobacillus species, are considered healthy, while the fifth, which is composed of non-Lactobacillus populations, is considered less protective. This latter CST is often considered to represent a state termed Bacterial vaginosis (BV) - a common disease condition associated with unpleasant symptoms and increased susceptibility to sexually transmitted diseases. However, the exact mechanisms underlying BV development are not yet fully understood, including specifically, the dynamics of the vaginal microbiome in BV, and the possible routes it may take from a healthy to a BV state. This study aims to identify the progression from healthy Lactobacillus-dominant populations to symptomatic BV by analyzing 8,026 vaginal samples and using a manifold-detection framework. This approach is inspired by single-cell analysis and aims to identify low-dimensional trajectories in the high-dimensional composition space. This framework further order samples along these trajectories and assign a score (pseudo-time) to each sample based on its proximity to the BV state. Our results reveal distinct routes of progression between healthy and BV state for each CST, with pseudo-time scores correlating with community diversity and quantifying the health state of each sample. BV indicators, including Nugent score, positive Amsel's test, and several Amsel's criteria, can also be successfully predicted based on pseudo-time scores. Additionally, Gardnerella vaginalis can be identified as a key taxon in BV development using this approach, with increased abundance in samples with high pseudo-time, indicating an unhealthier state across all BV-development routes on the manifold. Taken together, these findings demonstrate how manifold detection can be used to successfully characterizes the progression from healthy Lactobacillus-dominant populations to BV and to accurately quantify the health condition of new samples along the route of BV development.

Tumor-associated macrophages in nanomaterial-based anti-tumor therapy: as target spots or delivery platforms

Targeting tumor-associated macrophages (TAMs) has emerged as a promising approach in cancer therapy. This article provides a comprehensive review of recent advancements in the field of nanomedicines targeting TAMs. According to the crucial role of TAMs in tumor progression, strategies to inhibit macrophage recruitment, suppress TAM survival, and transform TAM phenotypes are discussed as potential therapeutic avenues. To enhance the targeting capacity of nanomedicines, various approaches such as the use of ligands, immunoglobulins, and short peptides are explored. The utilization of live programmed macrophages, macrophage cell membrane-coated nanoparticles and macrophage-derived extracellular vesicles as drug delivery platforms is also highlighted, offering improved biocompatibility and prolonged circulation time. However, challenges remain in achieving precise targeting and controlled drug release. The heterogeneity of TAMs and the variability of surface markers pose hurdles in achieving specific recognition. Furthermore, the safety and clinical applicability of these nanomedicines requires further investigation. In conclusion, nanomedicines targeting TAMs hold great promise in cancer therapy, offering enhanced specificity and reduced side effects. Addressing the existing limitations and expanding our understanding of TAM biology will pave the way for the successful translation of these nano-therapies into clinical practice.

Leak current, even with gigaohm seals, can cause misinterpretation of stem cell-derived cardiomyocyte action potential recordings

AIMS

Human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) have become an essential tool to study arrhythmia mechanisms. Much of the foundational work on these cells, as well as the computational models built from the resultant data, has overlooked the contribution of seal-leak current on the immature and heterogeneous phenotype that has come to define these cells. The aim of this study is to understand the effect of seal-leak current on recordings of action potential (AP) morphology.

METHODS AND RESULTS

Action potentials were recorded in human iPSC-CMs using patch clamp and simulated using previously published mathematical models. Our in silico and in vitro studies demonstrate how seal-leak current depolarizes APs, substantially affecting their morphology, even with seal resistances (Rseal) above 1 GΩ. We show that compensation of this leak current is difficult due to challenges with obtaining accurate measures of Rseal during an experiment. Using simulation, we show that Rseal measures (i) change during an experiment, invalidating the use of pre-rupture values, and (ii) are polluted by the presence of transmembrane currents at every voltage. Finally, we posit that the background sodium current in baseline iPSC-CM models imitates the effects of seal-leak current and is increased to a level that masks the effects of seal-leak current on iPSC-CMs.

CONCLUSION

Based on these findings, we make recommendations to improve iPSC-CM AP data acquisition, interpretation, and model-building. Taking these recommendations into account will improve our understanding of iPSC-CM physiology and the descriptive ability of models built from such data.

Endoplasmic reticulum stress and the inflammatory response in allergic contact dermatitis

Maintaining homeostasis is central to organismal health. Deviation is detected by a variety of sensors that react to alarm signals arising from injury, infection, and other inflammatory triggers. One important element of this alarm system is the innate immune system, which recognizes pathogen-/microbe- or damage-associated molecular patterns via pattern recognition receptors localized in the cytosol or in membranes of innate immune cells such as macrophages, dendritic cells, and mast cells but also of T cells, B cells, and epithelial cells. Activation of the innate immune system results in inflammation and is a pre-requisite for activation of the adaptive immune system. Another important element is represented by the unfolded protein response (UPR), a stress response of the endoplasmic reticulum. The UPR regulates proteostasis and also contributes to the course of inflammatory diseases such as cancer, diabetes, obesity, and neurodegenerative diseases. In addition, the UPR is instrumental in allergic contact dermatitis. This inflammatory skin disease, affecting 5-10% of the population, is caused by T cells recognizing low-molecular weight organic chemicals and metal ions. In this mini-review, we discuss the orchestration of inflammatory responses by the interplay of the innate immune system with cellular stress responses in allergic contact dermatitis, with a focus on the UPR.

Vaccine-Induced Immunity Elicited by Microneedle Delivery of Influenza Ectodomain Matrix Protein 2 Virus-like Particle (M2e VLP)-Loaded PLGA Nanoparticles

This study focused on developing an influenza vaccine delivered in polymeric nanoparticles (NPs) using dissolving microneedles. We first formulated an influenza extracellular matrix protein 2 virus-like particle (M2e VLP)-loaded with poly(lactic-co-glycolic) acid (PLGA) nanoparticles, yielding M2e5x VLP PLGA NPs. The vaccine particles were characterized for their physical properties and in vitro immunogenicity. Next, the M2e5x VLP PLGA NPs, along with the adjuvant Alhydrogel® and monophosphoryl lipid A® (MPL-A®) PLGA NPs, were loaded into fast-dissolving microneedles. The vaccine microneedle patches were then evaluated in vivo in a murine model. The results from this study demonstrated that the vaccine nanoparticles effectively stimulated antigen-presenting cells in vitro resulting in enhanced autophagy, nitric oxide, and antigen presentation. In mice, the vaccine elicited M2e-specific antibodies in both serum and lung supernatants (post-challenge) and induced significant expression of CD4+ and CD8+ populations in the lymph nodes and spleens of immunized mice. Hence, this study demonstrated that polymeric particulates for antigen and adjuvant encapsulation, delivered using fast-dissolving microneedles, significantly enhanced the immunogenicity of a conserved influenza antigen.

Live Cell Imaging by Förster Resonance Energy Transfer Fluorescence to Study Trafficking of PLGA Nanoparticles and the Release of a Loaded Peptide in Dendritic Cells

Our previous study demonstrated that a selected β-lactoglobulin-derived peptide (BLG-Pep) loaded in poly(lactic-co-glycolic acid) (PLGA) nanoparticles protected mice against cow's milk allergy development. However, the mechanism(s) responsible for the interaction of the peptide-loaded PLGA nanoparticles with dendritic cells (DCs) and their intracellular fate was/were elusive. Förster resonance energy transfer (FRET), a distance-dependent non-radioactive energy transfer process mediated from a donor to an acceptor fluorochrome, was used to investigate these processes. The ratio of the donor (Cyanine-3)-conjugated peptide and acceptor (Cyanine-5) labeled PLGA nanocarrier was fine-tuned for optimal (87%) FRET efficiency. The colloidal stability and FRET emission of prepared NPs were maintained upon 144 h incubation in PBS buffer and 6 h incubation in biorelevant simulated gastric fluid at 37 °C. A total of 73% of Pep-Cy3 NP was internalized by DCs as quantified using flow cytometry and confirmed using confocal fluorescence microscopy. By real-time monitoring of the change in the FRET signal of the internalized peptide-loaded nanoparticles, we observed prolonged retention (for 96 h) of the nanoparticles-encapsulated peptide as compared to 24 h retention of the free peptide in the DCs. The prolonged retention and intracellular antigen release of the BLG-Pep loaded in PLGA nanoparticles in murine DCs might facilitate antigen-specific tolerance induction.

Asiatic acid in Centella asiatica extract towards morphological development in an intermittent hypoxia intrauterine embryo model and molecular prediction pathway of insulin-like growth factor-1 receptor signalling

Background

Hypoxia during pregnancy generates oxidative stress that alters the growth and development of the human fetus. Insulin-like growth factor-1 (IGF-1) receptors are essential for normal fetal growth. Asiatic acid in Centella asiatica (CA) has antioxidant properties to prevent growth impairment in hypoxia.

Aims

This study aimed to investigate the effect of asiatic acid on the morphological development of an intermittent hypoxia (IH) zebrafish embryo model and analyze molecular docking prediction in IGF-1 receptor (IGF-1R) signaling.

Methods

Embryos of zebrafish at 2 hours postfertilization (hpf) were assigned to control negative (C), IH, and combination IH and CA extract groups consisting of 1.25 (IHCA1), 2.5 (IHCA2), and 5 (IHCA3) µg/ml. Hypoxia treatment (conducted 4 hours/day) and CA extract were administered for 3 days (2-72 hpf). The parameters of body length and head length were evaluated at 3, 6, and 9 days postfertilization (dpf). The data were analyzed by a two-way analysis of variance (p < 0.05). Molecular docking was performed to explore the binding affinity of asiatic acid to IGF-1R by Molegro Virtual Docker ver.5 software.

Results

The body length and head length of embryos in the IH and treatment groups (IHCA) were shorter than those in the control group at 3 dpf (p < 0.05). However, the body length was more prolonged in the IHCA1 group, but the head length was longer in the IHCA2 group than in the IH group at 6 and 9 dpf. Molecular docking showed the reliable interaction of asiatic acid with IGF-1R signaling in an IH animal model.

Conclusion

The administration of CA extract benefits IH through the development and growth of zebrafish embryos at a dose of 2.5-5 µg/ml. Asiatic acid has a binding affinity for IGF-1R signaling.

Challenges and opportunities in analyzing and modeling peptide presentation by HLA-II proteins

The human leukocyte antigen (HLA) proteins are an indispensable component of adaptive immunity because of their role in presenting self and foreign peptides to T cells. Further, many complex diseases are associated with genetic variation in the HLA region, implying an important role for specific HLA-presented peptides in the etiology of these diseases. Identifying the specific set of peptides presented by an individual’s HLA proteins in vivo, as a whole being referred to as the immunopeptidome, has therefore gathered increasing attention for different reasons. For example, identifying neoepitopes for cancer immunotherapy, vaccine development against infectious pathogens, or elucidating the role of HLA in autoimmunity. Despite the tremendous progress made during the last decade in these areas, several questions remain unanswered. In this perspective, we highlight five remaining key challenges in the analysis of peptide presentation and T cell immunogenicity and discuss potential solutions to these problems. We believe that addressing these questions would not only improve our understanding of disease etiology but will also have a direct translational impact in terms of engineering better vaccines and in developing more potent immunotherapies.

Longitudinal analysis of DC subsets in patients with ovarian cancer: Implications for immunotherapy

Background

The use of circulating cDC1 to generate anti-cancer vaccines is among the most promising approaches to overcome the limited immunogenicity and clinical efficacy of monocyte-derived DC. However, the recurrent lymphopenia and the reduction of DC numbers and functionality in patients with cancer may represent an important limitation of such approach. In patients with ovarian cancer (OvC) that had received chemotherapy, we previously showed that cDC1 frequency and function were reduced.

Methods

We recruited healthy donors (HD, n=7) and patients with OvC at diagnosis and undergoing interval debulking surgery (IDS, n=6), primary debulking surgery (PDS, n=6) or at relapse (n=8). We characterized longitudinally phenotypic and functional properties of peripheral DC subsets by multiparametric flow cytometry.

Results

We show that the frequency of cDC1 and the total CD141+ DC capacity to take up antigen are not reduced at the diagnosis, while their TLR3 responsiveness is partially impaired in comparison with HD. Chemotherapy causes cDC1 depletion and increase in cDC2 frequency, but mainly in patients belonging to the PDS group, while in the IDS group both total lymphocytes and cDC1 are preserved. The capacity of total CD141+ DC and cDC2 to take up antigen is not impacted by chemotherapy, while the activation capacity upon Poly(I:C) (TLR3L) stimulation is further decreased.

Conclusions

Our study provides new information about the impact of chemotherapy on the immune system of patients with OvC and sheds a new light on the importance of considering timing with respect to chemotherapy when designing new vaccination strategies that aim at withdrawing or targeting specific DC subsets.

Biomimetic Nanovaccines Potentiating Dendritic Cell Internalization via CXCR4-Mediated Macropinocytosis

Although targeted delivery of nanoparticulate vaccines to dendritic cells (DCs) holds tremendous potential, it still faces insufficient internalization and endosome degradation via the receptor-mediated endocytosis pathway. Inspired by the advantages of CXC-chemokine receptor type 4 (CXCR4)-mediated macropinocytosis in the internalization of DCs, a multifunctional vaccine is constructed based on a reactive oxygen species (ROS)-responsive nanoparticulate core and macropinocytosis-inducing peptide-fused cancer membrane shell, allowing the direct cytosolic delivery of cancer membrane-associated antigen and a stimulator of interferon genes (STING) agonist, cGAMP for highly efficient cancer immunotherapy. The biomimetic nanovaccines show a dramatically enhanced cellular uptake by DCs via CXCR4-mediated macropinocytosis. Such a direct delivery process promotes cytosolic release of cGAMP in response to ROS, and together promoted DC maturation and T cell priming by activating the STING pathway. Consequently, the biomimetic nanovaccines not only result in a great tumor rejection in prophylactic B16-F10 melanoma murine model, but also markedly suppress the growth of established melanoma tumors when combined with anti-PD-1 checkpoint blockade. This study advances the design of biomimetic nanovaccines and provides a promising strategy for macropinocytosis-mediated cancer vaccination.

High extracellular sodium chloride concentrations induce resistance to LPS signal in human dendritic cells

Recent evidence showed that in response to elevated sodium dietary intakes, many body tissues retain Na⁺ ions for long periods of time and can reach concentrations up to 200 mM. This could modulate the immune system and be responsible for several diseases. However, studies brought contrasted results and the effects of external sodium on human dendritic cell (DC) responses to danger signals remain largely unknown. Considering their central role in triggering T cell response, we tested how NaCl-enriched medium influences human DCs properties. We found that DCs submitted to high extracellular Na⁺ concentrations up to 200 mM remain viable and maintain the expression of specific DC markers, however, their maturation, chemotaxis toward CCL19, production of pro-inflammatory cytokines and ROS in response to LPS were also partially inhibited. In line with these results, the T-cell allostimulatory capacity of DCs was also inhibited. Finally, our data indicate that high NaCl concentrations triggered the phosphorylation of SGK1 and ERK1/2 kinases. These results raised the possibility that the previously reported pro-inflammatory effects of high NaCl concentrations on T cells might be counterbalanced by a downregulation of DC activation.

Tilapia Lake Virus Vaccine Development: A Review on the Recent Advances

Tilapia tilapinevirus (or tilapia lake virus, TiLV) is a recently emerging virus associated with a novel disease affecting and decimating tilapia populations around the world. Since its initial identification, TiLV has been reported in 17 countries, often causing mortalities as high as 90% in the affected populations. To date, no therapeutics or commercial vaccines exist for TiLV disease control. Tilapia exposed to TiLV can develop protective immunity, suggesting that vaccination is achievable. Given the important role of vaccination in fish farming, several vaccine strategies are currently being explored and put forward against TiLV but, a comprehensive overview on the efficacy of these platforms is lacking. We here present these approaches in relation with previously developed fish vaccines and discuss their efficacy, vaccine administration routes, and the various factors that can impact vaccine efficacy. The overall recent advances in TiLV vaccine development show different but promising levels of protection. The field is however hampered by the lack of knowledge of the biology of TiLV, notably the function of its genes. Further research and the incorporation of several approaches including prime-boost vaccine regimens, codon optimization, or reverse vaccinology would be beneficial to increase the effectiveness of vaccines targeting TiLV and are further discussed in this review.

The Monocytic Cell Line THP-1 as a Validated and Robust Surrogate Model for Human Dendritic Cells

We have implemented an improved, cost-effective, and highly reproducible protocol for a simple and rapid differentiation of the human leukemia monocytic cell line THP-1 into surrogates for immature dendritic cells (iDCs) or mature dendritic cells (mDCs). The successful differentiation of THP-1 cells into iDCs was determined by high numbers of cells expressing the DC activation markers CD54 (88%) and CD86 (61%), and the absence of the maturation marker CD83. The THP-1-derived mDCs are characterized by high numbers of cells expressing CD54 (99%), CD86 (73%), and the phagocytosis marker CD11b (49%) and, in contrast to THP-1-derived iDCs, CD83 (35%) and the migration marker CXCR4 (70%). Treatment of iDCs with sensitizers, such as NiSO4 and DNCB, led to high expression of CD54 (97%/98%; GMFI, 3.0/3.2-fold induction) and CD86 (64%/96%; GMFI, 4.3/3.2-fold induction) compared to undifferentiated sensitizer-treated THP-1 (CD54, 98%/98%; CD86, 55%/96%). Thus, our iDCs are highly suitable for toxicological studies identifying potential sensitizing or inflammatory compounds. Furthermore, the expression of CD11b, CD83, and CXCR4 on our iDC and mDC surrogates could allow studies investigating the molecular mechanisms of dendritic cell maturation, phagocytosis, migration, and their use as therapeutic targets in various disorders, such as sensitization, inflammation, and cancer.

Assessing the Ability of Human Dendritic Cells to Stimulate Naive CD4+ and CD8+ T Cells

Dendritic cells orient T cell responses via antigen presentation and provision of polarizing signals. The ability of human dendritic cells to polarize effector T cells can be assessed in mixed lymphocyte reactions. Here we describe a protocol that can be used with any human dendritic cell to assess their ability to polarize CD4⁺ T helper cells or CD8⁺ cytotoxic T cells.

Nano-enabled agriculture: How do nanoparticles cross barriers in plants?

Nano-enabled agriculture is a topic of intense research interest. However, our knowledge of how nanoparticles enter plants, plant cells, and organelles is still insufficient. Here, we discuss the barriers that limit the efficient delivery of nanoparticles at the whole-plant and single-cell levels. Some commonly overlooked factors, such as light conditions and surface tension of applied nano-formulations, are discussed. Knowledge gaps regarding plant cell uptake of nanoparticles, such as the effect of electrochemical gradients across organelle membranes on nanoparticle delivery, are analyzed and discussed. The importance of controlling factors such as size, charge, stability, and dispersibility when properly designing nanomaterials for plants is outlined. We mainly focus on understanding how nanoparticles travel across barriers in plants and plant cells and the major factors that limit the efficient delivery of nanoparticles, promoting a better understanding of nanoparticle-plant interactions. We also provide suggestions on the design of nanomaterials for nano-enabled agriculture.

The Vitruvian spider: Segmenting and integrating over different body parts to describe ecophenotypic variation

Understanding what drives the existing phenotypic variability has been a major topic of interest for biologists for generations. However, the study of the phenotype may not be straightforward. Indeed, organisms may be interpreted as composite objects, comprising different ecophenotypic traits, which are neither necessarily independent from each other nor do they respond to the same evolutionary pressures. For this reason, a deep biological understanding of the focal organism is essential for any morphological analysis. The spider genus Dysdera provides a particularly well-suited system for setting up protocols for morphological analyses that encompass a suit of morphological structures in any nonmodel system. This genus has undergone a remarkable diversification in the Canary Islands, where different species perform different ecological roles, exhibiting different levels of trophic specialization or troglomorphic adaptations, which translate into a remarkable interspecific morphological variability. Here, we seek to develop a broad guide, of which morphological characters must be considered, to study the effect of different ecological pressures in spiders and propose a general workflow that will be useful whenever researchers set out to investigate variation in the body plans of different organisms, with data sets comprising a set of morphological traits. We use geometric morphometric methods to quantify variation in different body structures, all of them with diverse phenotypic modifications in their chelicera, prosoma, and legs. We explore the effect of analyzing different combined landmark (LM) configurations of these characters and the degree of morphological integration that they exhibit. Our results suggest that different LM configurations of each of these body parts exhibit a higher degree of integration compared to LM configurations from different structures and that the analysis of each of these body parts captures different aspects of morphological variation, potentially related to different ecological factors.

HIV-1-Infected CD4+ T Cells Present MHC Class II-Restricted Epitope via Endogenous Processing

HIV-1-specific CD4⁺ T cells (T_CD4+s) play a critical role in controlling HIV-1 infection. Canonically, T_CD4+s are activated by peptides derived from extracellular ("exogenous") Ags displayed in complex with MHC class II (MHC II) molecules on the surfaces of "professional" APCs such as dendritic cells (DCs). In contrast, activated human T_CD4+s, which express MHC II, are not typically considered for their APC potential because of their low endocytic capacity and the exogenous Ag systems historically used for assessment. Using primary T_CD4+s and monocyte-derived DCs from healthy donors, we show that activated human T_CD4+s are highly effective at MHC II-restricted presentation of an immunodominant HIV-1-derived epitope postinfection and subsequent noncanonical processing and presentation of endogenously produced Ag. Our results indicate that, in addition to marshalling HIV-1-specific immune responses during infection, T_CD4+s also act as APCs, leading to the activation of HIV-1-specific T_CD4+s.

The Role and Therapeutic Potential of Macropinocytosis in Cancer

Macropinocytosis, a unique endocytosis pathway characterized by nonspecific internalization, has a vital role in the uptake of extracellular substances and antigen presentation. It is known to have dual effects on cancer cells, depending on cancer type and certain microenvironmental conditions. It helps cancer cells survive in nutrient-deficient environments, enhances resistance to anticancer drugs, and promotes invasion and metastasis. Conversely, overexpression of the RAS gene alongside drug treatment can lead to methuosis, a novel mode of cell death. The survival and proliferation of cancer cells is closely related to macropinocytosis in the tumor microenvironment (TME), but identifying how these cells interface with the TME is crucial for creating drugs that can limit cancer progression and metastasis. Substantial progress has been made in recent years on designing anticancer therapies that utilize the effects of macropinocytosis. Both the induction and inhibition of macropinocytosis are useful strategies for combating cancer cells. This article systematically reviews the general mechanisms of macropinocytosis, its specific functions in tumor cells, its occurrence in nontumor cells in the TME, and its application in tumor therapies. The aim is to elucidate the role and therapeutic potential of macropinocytosis in cancer treatment.

Abnormal lipid metabolism in epidermal Langerhans cells mediates psoriasis-like dermatitis

Psoriasis is a chronic, inflammatory skin disease, frequently associated with dyslipidemia. Lipid disturbance in psoriasis affects both circulatory system and cutaneous tissue. Epidermal Langerhans cells (LCs) are tissue-resident DCs that maintain skin immune surveillance and mediate various cutaneous disorders, including psoriasis. However, the role of LCs in psoriasis development and their lipid metabolic alternation remains unclear. Here, we demonstrate that epidermal LCs of psoriasis patients enlarge with longer dendrites and possess elevated IL-23p19 mRNA and a higher level of neutral lipids when compared with normal LCs of healthy individuals. Accordantly, epidermal LCs from imiquimod-induced psoriasis-like dermatitis in mice display overmaturation, enhanced phagocytosis, and excessive secretion of IL-23. Remarkably, these altered immune properties in lesional LCs are tightly correlated with elevated neutral lipid levels. Moreover, the increased lipid content of psoriatic LCs might result from impaired autophagy of lipids. Bulk RNA-Seq analysis identifies dysregulated genes involved in lipid metabolism, autophagy, and immunofunctions in murine LCs. Overall, our data suggest that dysregulated lipid metabolism influences LC immunofunction, which contributes to the development of psoriasis, and therapeutic manipulation of this metabolic process might provide an effective measurement for psoriasis.

Exploration of Deformation of F-Actin during Macropinocytosis by Confocal Microscopy and 3D-Structured Illumination Microscopy

Since their invention, confocal microscopy and super-resolution microscopy have become important choices in cell biology research. Macropinocytosis is a critical form of endocytosis. Deformation of the cell membrane is thought to be closely related to the movement of F-actin during macropinocytosis. However, it is still unclear how the morphology of F-actin and the membrane change during this process. In this study, confocal microscopy was utilized for macroscopic time-series imaging of the cell membranes and F-actin in cells induced by phorbol 12-myristate 13-acetate (PMA). Super-resolution structured illumination microscopy (SIM), which can overcome the diffraction limit, was used to demonstrate the morphological characteristics of F-actin filaments. Benefiting from the advantages of SIM in terms of resolution and 3D imaging, we speculated on the regular pattern of the deformation of F-actin during macropinocytosis. The detailed visualization of structures also helped to validate the speculation regarding the role of F-actin filaments in macropinocytosis in previous studies. The results obtained in this study will provide a better understanding of the mechanisms underlying macropinocytosis and endocytosis.

Fluorescent Artificial Antigens Revealed Extended Membrane Networks Utilized by Live Dendritic Cells for Antigen Uptake

Dendritic cells (DCs) can infiltrate tight junctions of the epithelium to collect remote antigens during immune surveillance. While elongated membrane structures represent a plausible structure to perform this task, their functional mechanisms remain elusive owing to the lack of high-resolution characterizations in live DCs. Here, we developed fluorescent artificial antigens (FAAs) based on quantum dots coated with polyacrylic acid. Single-particle tracking of FAAs enables us to superresolve the membrane fiber network responsible for the antigen uptake. Using the DC2.4 cell line as a model system, we discovered the extensive membrane network approaching 200 μm in length with tunnel-like cavities about 150 nm in width. The membrane fiber network also contained heterogeneous circular migrasomes. Disconnecting the membrane network from the cell body decreased the intracellular FAA density. Our study enables mechanistic investigations of DC membrane networks and nanocarriers that target this mechanism.

Effects of Low-Intensity and Long-Term Aerobic Exercise on the Psoas Muscle of mdx Mice: An Experimental Model of Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a muscle disease characterized by the absence of the protein dystrophin, which causes a loss of sarcolemma integrity, determining recurrent muscle injuries, decrease in muscle function, and progressive degeneration. Currently, there is a need for therapeutic treatments to improve the quality of life of DMD patients. Here, we investigated the effects of a low-intensity aerobic training (37 sessions) on satellite cells, peroxisome proliferator-activated receptor-gamma coactivator (PGC)-1α protein (PGC-1α), and different types of fibers of the psoas muscle from mdx mice (DMD experimental model). Wildtype and mdx mice were randomly divided into sedentary and trained groups (n = 24). Trained animals were subjected to 37 sessions of low-intensity running on a motorized treadmill. Subsequently, the psoas muscle was excised and analyzed by immunofluorescence for dystrophin, satellite cells, myosin heavy chain (MHC), and PGC-1α content. The minimal Feret’s diameters of the fibers were measured, and light microscopy was applied to observe general morphological features of the muscles. The training (37 sessions) improved morphological features in muscles from mdx mice and caused an increase in the number of quiescent/activated satellite cells. It also increased the content of PGC-1α in the mdx group. We concluded that low-intensity aerobic exercise (37 sessions) was able to reverse deleterious changes determined by DMD.

Macropinocytosis and Cancer: From Tumor Stress to Signaling Pathways

Macropinocytosis is an evolutionarily conserved endocytic pathway that mediates the nonselective acquisition of extracellular material via large endocytic vesicles known as macropinosomes. In addition to other functions, this uptake pathway supports cancer cell metabolism through the uptake of nutrients. Cells harboring oncogene or tumor suppressor mutations are known to display heightened macropinocytosis, which confers to the cancer cells the ability to survive and proliferate despite the nutrient-scarce conditions of the tumor microenvironment. Thus, macropinocytosis is associated with cancer malignancy. Macropinocytic uptake can be induced in cancer cells by different stress stimuli, acting as an adaptive mechanism for the cells to resist stresses in the tumor milieu. Here, we review the cellular stresses that are known to promote macropinocytosis, as well as the underlying molecular mechanisms that drive this process.

Self-Assembly of Flagellin into Immunostimulatory Ring-like Nanostructures as an Antigen Delivery System

Proteinaceous nanoparticles represent attractive antigen carriers for vaccination as their size and repetitive antigen displays that mimic most viral particles enable efficient immune processing. However, these nanocarriers are often unable to stimulate efficiently the innate immune system, requiring coadministration with adjuvants to promote long-lasting protective immunity. The protein flagellin, which constitutes the primary constituent of the bacterial flagellum, has been widely evaluated as an antigen carrier due to its intrinsic adjuvant properties involving activation of the innate immune receptor Toll-like receptor 5 (TLR5). Although flagellin is known for its ability to self-assemble into micron-scale length nanotubes, few studies have evaluated the potential usage of flagellin-based nanostructures as immunostimulatory antigen carriers. In this study, we reported for the first time a strategy to guide the self-assembly of a flagellin protein from Bacillus subtilis, Hag, into lower aspect ratio nanoparticles by hindering non-covalent interactions responsible for its elongation into nanotubes. We observed that addition of an antigenic sequence derived from the influenza A virus (3M2e) at the C-terminus of this flagellin, as opposed to positioning the epitope into mid-sequence, precluded filament elongation and resulted in low aspect ratio ring-like nanostructures upon salting-out-induced self-assembly. These nanostructures displayed the antigen at their surface and shared morphological and structural characteristics with flagellin nanotubes, with a diameter of approximately 12 nm, and an α-helix-rich secondary structure. Flagellin ring-like nanostructures were efficiently internalized by antigen-presenting cells, and avidly activated the TLR5 in vitro as well as the innate and adaptive immune responses. Intranasal immunization of mice with these nanostructures resulted in the potentiation of the antigen-specific antibody response and protection against a lethal infection with the influenza A virus, illustrating the potential of these intrinsically immunostimulatory nanostructures as antigen carriers.

Extracellular ATP and Macropinocytosis: Their Interactive and Mutually Supportive Roles in Cell Growth, Drug Resistance, and EMT in Cancer

Macropinocytosis is one of the major mechanisms by which cancer cells uptake extracellular nutrients from tumor microenvironment (TME) and plays very important roles in various steps of tumorigenesis. We previously reported the unexpected finding that intratumoral and extracellular ATP (eATP), as one of the major drastically upregulated extracellular nutrients and messengers in tumors, is taken up by cancer cells through macropinocytosis in large quantities and significantly contributing to cancer cell growth, survival, and increased resistance to chemo and target drugs. Inhibition of macropinocytosis substantially reduced eATP uptake by cancer cells and slowed down tumor growth in vivo. More recently, we have found the eATP also plays a very important role in inducing epithelial-to-mesenchymal transition (EMT), and that macropinocytosis is an essential facilitator in the induction. Thus, macropinocytosis and eATP, working in coordination, appear to play some previously unrecognized but very important roles in EMT and metastasis. As a result, they are likely to be interactive and communicative with each other, regulating each other's activity for various needs of host tumor cells. They are also likely to be an integral part of the future new anticancer therapeutic strategies. Moreover, it is undoubted that we have not identified all the important activities coordinated by ATP and macropinocytosis. This review describes our findings in how eATP and macropinocytosis work together to promote cancer cell growth, resistance, and EMT. We also list scientific challenges facing eATP research and propose to target macropinocytosis and eATP to reduce drug resistance and slow down metastasis.

Effect of micro- and nanoparticle shape on biological processes

In the drug delivery field, there is beyond doubt that the shape of micro- and nanoparticles (M&NPs) critically affects their biological fate. Herein, following an introduction describing recent technological advances for designing nonspherical M&NPs, we highlight the role of particle shape in cell capture, subcellular distribution, intracellular drug delivery, and cytotoxicity. Then, we discuss theoretical approaches for understanding the effect of particle shape on internalization by the cell membrane. Subsequently, recent advances on shape-dependent behaviors of M&NPs in the systemic circulation are detailed. In particular, the interaction of M&NPs with blood proteins, biodistribution, and circulation under flow conditions are analyzed. Finally, the hurdles and future directions for developing nonspherical M&NPs are underscored.

Transfer of Cellular Content from the Allogeneic Cell-Based Cancer Vaccine DCP-001 to Host Dendritic Cells Hinges on Phosphatidylserine and Is Enhanced by CD47 Blockade

DCP-001 is a cell-based cancer vaccine generated by differentiation and maturation of cells from the human DCOne myeloid leukemic cell line. This results in a vaccine comprising a broad array of endogenous tumor antigens combined with a mature dendritic cell (mDC) costimulatory profile, functioning as a local inflammatory adjuvant when injected into an allogeneic recipient. Intradermal DCP-001 vaccination has been shown to be safe and feasible as a post-remission therapy in acute myeloid leukemia. In the current study, the mode of action of DCP-001 was further characterized by static and dynamic analysis of the interaction between labelled DCP-001 and host antigen-presenting cells (APCs). Direct cell-cell interactions and uptake of DCP-001 cellular content by APCs were shown to depend on DCP-001 cell surface expression of calreticulin and phosphatidylserine, while blockade of CD47 enhanced the process. Injection of DCP-001 in an ex vivo human skin model led to its uptake by activated skin-emigrating DCs. These data suggest that, following intradermal DCP-001 vaccination, local and recruited host APCs capture tumor-associated antigens from the vaccine, become activated and migrate to the draining lymph nodes to subsequently (re)activate tumor-reactive T-cells. The improved uptake of DCP-001 by blocking CD47 rationalizes the possible combination of DCP-001 vaccination with CD47 blocking therapies.

Transdermal Vaccination with the Matrix-2 Protein Virus-like Particle (M2e VLP) Induces Immunity in Mice against Influenza A Virus

In this study, our goal was to utilize the extracellular domain matrix-2 protein virus-like particle (M2e VLP) that has been found to be highly conserved amongst all strains of influenza and could serve as a potential vaccine candidate against influenza. Previous studies have demonstrated that the VLP of the M2e showed increased activation of innate and adaptive immune responses. Therefore, to further explore its level of efficacy and protection, this vaccine was administered transdermally and tested in a pre-clinical mouse model. The M2e VLP was encapsulated into a polymeric matrix with the addition of Alhydrogel® and Monophosphoryl Lipid-A (MPL-A®), together referred to as AS04. The M2e VLP formulations induced IgG titers, with increased levels of IgG1 in the M2e VLP MP groups and further elevated levels of IgG2a were found specifically in the M2e VLP MP Adjuvant group. This trend in humoral immunity was also observed from a cell-mediated standpoint, where M2e VLP MP groups showed increased expression in CD4+ T cells in the spleen and the lymph node and high levels of CD8+ T cells in the lymph node. Taken together, the results illustrate the immunogenic potential of the matrix-2 protein virus-like particle (M2e VLP) vaccine.

Purification of infection-associated macropinosomes by magnetic isolation for proteomic characterization

Macropinocytosis refers to the nonselective uptake of extracellular molecules into many different types of eukaryotic cells within large fluid-filled vesicles named macropinosomes. Macropinosomes are relevant for a wide variety of cellular processes, such as antigen sampling in immune cells, homeostasis in the kidney, cell migration or pathogen uptake. Understanding the molecular composition of the different macropinosomes formed during these processes has helped to differentiate their regulations from other endocytic events. Here, we present a magnetic purification protocol that segregates scarce macropinosomes from other endocytic vesicles at a high purity and in a low-cost and unbiased manner. Our protocol takes advantage of moderate-sized magnetic beads of 100 nm in diameter coupled to mass-spectrometry-based proteomic analysis. Passing the cell lysate through a table-top magnet allows the quick retention of the bead-containing macropinosomes. Unlike other cell-fractionation-based methodologies, our protocol minimizes sample loss and production cost without prerequisite knowledge of the macropinosomes and with minimal laboratory experience. We describe a detailed procedure for the isolation of infection-associated macropinosomes during bacterial invasion and the optimization steps to readily adapt it to various studies. The protocol can be performed in 3 d to provide highly purified and enriched macropinosomes for qualitative proteomic composition analysis.

Translocation of LSR from tricellular corners causes macropinocytosis at cell-cell interface as a trigger for breaking out of contact inhibition

Withdrawal from contact inhibition is necessary for epithelial cancer precursor cells to initiate cell growth and motility. Nevertheless, little is understood about the mechanism for the sudden initiation of cell growth under static conditions. We focused on cellular junctions as one region where breaking out of contact inhibition occurs. In well-differentiated endometrial cancer cells, Sawano, the ligand administration for tricellular tight junction protein LSR, which transiently decreased the robust junction property, caused an abrupt increase in cell motility and consequent excessive multilayered cell growth despite being under contact inhibition conditions. We observed that macropinocytosis essentially and temporarily occurred as an antecedent event for the above process at intercellular junctions without disruption of the junction apparatus but not at the apical plasma membrane. Collectively, we concluded that the formation of macropinocytosis, which is derived from tight junction-mediated signaling, was triggered for the initiation of cell growth in static precancerous epithelium.

From influenza to COVID-19: Lipid nanoparticle mRNA vaccines at the frontiers of infectious diseases

Vaccination represents the best line of defense against infectious diseases and is crucial in curtailing pandemic spread of emerging pathogens to which a population has limited immunity. In recent years, mRNA vaccines have been proposed as the new frontier in vaccination, owing to their facile and rapid development while providing a safer alternative to traditional vaccine technologies such as live or attenuated viruses. Recent breakthroughs in mRNA vaccination have been through formulation with lipid nanoparticles (LNPs), which provide both protection and enhanced delivery of mRNA vaccines in vivo. In this review, current paradigms and state-of-the-art in mRNA-LNP vaccine development are explored through first highlighting advantages posed by mRNA vaccines, establishing LNPs as a biocompatible delivery system, and finally exploring the use of mRNA-LNP vaccines in vivo against infectious disease towards translation to the clinic. Furthermore, we highlight the progress of mRNA-LNP vaccine candidates against COVID-19 currently in clinical trials, with the current status and approval timelines, before discussing their future outlook and challenges that need to be overcome towards establishing mRNA-LNPs as next-generation vaccines. STATEMENT OF SIGNIFICANCE: With the recent success of mRNA vaccines developed by Moderna and BioNTech/Pfizer against COVID-19, mRNA technology and lipid nanoparticles (LNP) have never received more attention. This manuscript timely reviews the most advanced mRNA-LNP vaccines that have just been approved for emergency use and are in clinical trials, with a focus on the remarkable development of several COVID-19 vaccines, faster than any other vaccine in history. We aim to give a comprehensive introduction of mRNA and LNP technology to the field of biomaterials science and increase accessibility to readers with a new interest in mRNA-LNP vaccines. We also highlight current limitations and future outlook of the mRNA vaccine technology that need further efforts of biomaterials scientists to address.

From Pinocytosis to Methuosis-Fluid Consumption as a Risk Factor for Cell Death

The volumes of a cell [cell volume (CV)] and its organelles are adjusted by osmoregulatory processes. During pinocytosis, extracellular fluid volume equivalent to its CV is incorporated within an hour and membrane area equivalent to the cell's surface within 30 min. Since neither fluid uptake nor membrane consumption leads to swelling or shrinkage, cells must be equipped with potent volume regulatory mechanisms. Normally, cells respond to outwardly or inwardly directed osmotic gradients by a volume decrease and increase, respectively, i.e., they shrink or swell but then try to recover their CV. However, when a cell death (CD) pathway is triggered, CV persistently decreases in isotonic conditions in apoptosis and it increases in necrosis. One type of CD associated with cell swelling is due to a dysfunctional pinocytosis. Methuosis, a non-apoptotic CD phenotype, occurs when cells accumulate too much fluid by macropinocytosis. In contrast to functional pinocytosis, in methuosis, macropinosomes neither recycle nor fuse with lysosomes but with each other to form giant vacuoles, which finally cause rupture of the plasma membrane (PM). Understanding methuosis longs for the understanding of the ionic mechanisms of cell volume regulation (CVR) and vesicular volume regulation (VVR). In nascent macropinosomes, ion channels and transporters are derived from the PM. Along trafficking from the PM to the perinuclear area, the equipment of channels and transporters of the vesicle membrane changes by retrieval, addition, and recycling from and back to the PM, causing profound changes in vesicular ion concentrations, acidification, and-most importantly-shrinkage of the macropinosome, which is indispensable for its proper targeting and cargo processing. In this review, we discuss ion and water transport mechanisms with respect to CVR and VVR and with special emphasis on pinocytosis and methuosis. We describe various aspects of the complex mutual interplay between extracellular and intracellular ions and ion gradients, the PM and vesicular membrane, phosphoinositides, monomeric G proteins and their targets, as well as the submembranous cytoskeleton. Our aim is to highlight important cellular mechanisms, components, and processes that may lead to methuotic CD upon their derangement.

In vitro immunogenicity prediction: bridging between innate and adaptive immunity

Development of antidrug antibodies (ADAs) is an undesirable potential outcome of administration of biotherapeutics and involves the innate and adaptive immune systems. ADAs can have detrimental clinical consequences: they can reduce biotherapeutic efficacy or produce adverse events. Because animal models are considered poor predictors of immunogenicity in humans, in vitro assays with human innate and adaptive immune cells are commonly used alternatives that can reveal cell-mediated unwanted immune responses. Multiple methods have been developed to assess the immune cell response following exposure to biotherapeutics and estimate the potential immunogenicity of biotherapeutics. This review highlights the role of innate and adaptive immune cells as the drivers of immunogenicity and summarizes the use of these cells in assays to predict clinical ADA.

Ionizing Radiation Curtails Immunosuppressive Effects From Cancer-Associated Fibroblasts on Dendritic Cells

Cancer-associated fibroblasts (CAFs) participate actively in tumor development and affect treatment responses, by among other mechanisms, promoting an immunosuppressive tumor microenvironment. In contrast to normal fibroblasts, reactive CAFs secrete a myriad of immunomodulatory soluble factors at high levels, i.e. growth factors, cytokines, and chemokines, which directly influence tumor immunity and inflammation. CAFs have been identified as important players in tumor radioresistance. However, knowledge on the immunomodulatory functions of CAFs during/after radiotherapy is still lacking. In this study, we investigated the effects of ionizing radiation on CAF-mediated regulation of dendritic cells (DCs). CAFs were obtained from freshly operated lung cancer tissues, while DCs were procured from peripheral blood of healthy donors. Experimental settings comprised both co-cultures and incubations with conditioned medium from control and irradiated CAFs. Functional assays to study DC differentiation/activation consisted on cytokine release, expression of cell-surface markers, antigen uptake, migration rates, T cell priming, and DC-signaling analysis. We demonstrate that CAFs induce a tolerogenic phenotype in DCs by promoting down-regulation of: i) signature DC markers (CD14, CD1a, CD209); ii) activation markers (CD80, CD86, CD40, and HLA-DR) and iii) functional properties (migration, antigen uptake, and CD4⁺ T cell priming). Notably, some of these effects were lost in conditioned medium from CAFs irradiated at fractionated medium-dose regimens (3x6 Gy). However, the expression of relevant CAF-derived regulatory agents like thymic stromal lymphopoietin (TSLP) or tryptophan 2,3-dioxygenase (TDO2) was unchanged upon irradiation. This study demonstrates that CAFs interfere with DC immune functions and unveil that certain radiation regimens may reverse CAF-mediated immunosuppressive effects.

The Emerging Role of the Innate Immune Response in Idiosyncratic Drug Reactions

Idiosyncratic drug reactions (IDRs) range from relatively common, mild reactions to rarer, potentially life-threatening adverse effects that pose significant risks to both human health and successful drug discovery. Most frequently, IDRs target the liver, skin, and blood or bone marrow. Clinical data indicate that most IDRs are mediated by an adaptive immune response against drug-modified proteins, formed when chemically reactive species of a drug bind to self-proteins, making them appear foreign to the immune system. Although much emphasis has been placed on characterizing the clinical presentation of IDRs and noting implicated drugs, limited research has focused on the mechanisms preceding the manifestations of these severe responses. Therefore, we propose that to address the knowledge gap between drug administration and onset of a severe IDR, more research is required to understand IDR-initiating mechanisms; namely, the role of the innate immune response. In this review, we outline the immune processes involved from neoantigen formation to the result of the formation of the immunologic synapse and suggest that this framework be applied to IDR research. Using four drugs associated with severe IDRs as examples (amoxicillin, amodiaquine, clozapine, and nevirapine), we also summarize clinical and animal model data that are supportive of an early innate immune response. Finally, we discuss how understanding the early steps in innate immune activation in the development of an adaptive IDR will be fundamental in risk assessment during drug development. SIGNIFICANCE STATEMENT: Although there is some understanding that certain adaptive immune mechanisms are involved in the development of idiosyncratic drug reactions, the early phase of these immune responses remains largely uncharacterized. The presented framework refocuses the investigation of IDR pathogenesis from severe clinical manifestations to the initiating innate immune mechanisms that, in contrast, may be quite mild or clinically silent. A comprehensive understanding of these early influences on IDR onset is crucial for accurate risk prediction, IDR prevention, and therapeutic intervention.

Brain-specific functions of the endocytic machinery

Endocytosis is an essential cellular process required for multiple physiological functions, including communication with the extracellular environment, nutrient uptake, and signaling by the cell surface receptors. In a broad sense, endocytosis is accomplished through either constitutive or ligand-induced invagination of the plasma membrane, which results in the formation of the plasma membrane-retrieved endocytic vesicles, which can either be sent for degradation to the lysosomes or recycled back to the PM. This additional function of endocytosis in membrane retrieval has been adopted by excitable cells, such as neurons, for membrane equilibrium maintenance at synapses. The last two decades were especially productive with respect to the identification of brain-specific functions of the endocytic machinery, which additionally include but not limited to regulation of neuronal differentiation and migration, maintenance of neuron morphology and synaptic plasticity, and prevention of neurotoxic aggregates spreading. In this review, we highlight the current knowledge of brain-specific functions of endocytic machinery with a specific focus on three brain cell types, neuronal progenitor cells, neurons, and glial cells.

Exploration and insights into the cellular internalization and intracellular fate of amphiphilic polymeric nanocarriers

The beneficial or deleterious effects of nanomedicines emerge from their complex interactions with intracellular pathways and their subcellular fate. Moreover, the dynamic nature of plasma membrane accounts for the movement of these nanocarriers within the cell towards different organelles thereby not only influencing their pharmacokinetic and pharmacodynamic properties but also bioavailability, therapeutic efficacy and toxicity. Therefore, an in-depth understanding of underlying parameters controlling nanocarrier endocytosis and intracellular fate is essential. In order to direct nanoparticles towards specific sub-cellular organelles the physicochemical attributes of nanocarriers can be manipulated. These include particle size, shape and surface charge/chemistry. Restricting the particle size of nanocarriers below 200 nm contributes to internalization via clathrin and caveolae mediated pathways. Similarly, a moderate negative surface potential confers endolysosomal escape and targeting towards mitochondria, endoplasmic reticulum (ER) and Golgi. This review aims to provide an insight into these physicochemical attributes of nanocarriers fabricated using amphiphilic graft copolymers affecting cellular internalization. Fundamental principles understood from experimental studies have been extrapolated to draw a general conclusion for the designing of optimized nanoparticulate drug delivery systems and enhanced intracellular uptake via specific endocytic pathway.

Biomaterials to enhance antigen-specific T cell expansion for cancer immunotherapy

T cells are often referred to as the 'guided missiles' of our immune system because of their capacity to traffic to and accumulate at sites of infection or disease, destroy infected or mutated cells with high specificity and sensitivity, initiate systemic immune responses, sterilize infections, and produce long-lasting memory. As a result, they are a common target for a range of cancer immunotherapies. However, the myriad of challenges of expanding large numbers of T cells specific to each patient's unique tumor antigens has led researchers to develop alternative, more scalable approaches. Biomaterial platforms for expansion of antigen-specific T cells offer a path forward towards broadscale translation of personalized immunotherapies by providing "off-the-shelf", yet modular approaches to customize the phenotype, function, and specificity of T cell responses. In this review, we discuss design considerations and progress made in the development of ex vivo and in vivo technologies for activating antigen-specific T cells, including artificial antigen presenting cells, T cell stimulating scaffolds, biomaterials-based vaccines, and artificial lymphoid organs. Ultimate translation of these platforms as a part of cancer immunotherapy regimens hinges on an in-depth understanding of T cell biology and cell-material interactions.

The double-edged sword effect of macrophage targeting delivery system in different macrophage subsets related diseases

Background

Monocyte/macrophage-targeting delivery systems (MTDSs) have been focused upon as an emerging routine for delivering drugs to treat various macrophage-related diseases. However, the ability of MTDSs to distinguish different macrophage-related diseases and their impact on macrophage function and disease progression have not been systematically revealed, which is important for actively targeted therapeutic or diagnostic strategies.

Results

Herein, we used dextran-modified polystyrene nanoparticles (DEX-PS) to demonstrate that modification of nanoparticles by dextran can specifically enhance their recognition by M2 macrophages in vitro, but it is obstructed by monocytes in peripheral blood according to in vivo assays. DEX-PS not only targeted and became distributed in tumors, an M2 macrophage-related disease, but was also highly distributed in an M1 macrophage-related disease, namely acute peritonitis. Thus, DEX-PS acts as a double-edged sword in these two different diseases by reeducating macrophages to a pro-inflammatory phenotype.

Conclusions

Our results suggest that MTDSs, even those designed based on differential expression of receptors on specific macrophage subtypes, lack the ability to distinguish different macrophage subtype-related diseases in vivo. In addition to the potential impact of these carrier materials on macrophage function, studies of MTDSs should pay greater attention to the distribution of nanoparticles in non-target macrophage-infiltrated disease sites and their impact on disease processes.

SLIT2/ROBO1-signaling inhibits macropinocytosis by opposing cortical cytoskeletal remodeling

Macropinocytosis is essential for myeloid cells to survey their environment and for growth of RAS-transformed cancer cells. Several growth factors and inflammatory stimuli are known to induce macropinocytosis, but its endogenous inhibitors have remained elusive. Stimulation of Roundabout receptors by Slit ligands inhibits directional migration of many cell types, including immune cells and cancer cells. We report that SLIT2 inhibits macropinocytosis in vitro and in vivo by inducing cytoskeletal changes in macrophages. In mice, SLIT2 attenuates the uptake of muramyl dipeptide, thereby preventing NOD2-dependent activation of NF-κB and consequent secretion of pro-inflammatory chemokine, CXCL1. Conversely, blocking the action of endogenous SLIT2 enhances CXCL1 secretion. SLIT2 also inhibits macropinocytosis in RAS-transformed cancer cells, thereby decreasing their survival in nutrient-deficient conditions which resemble tumor microenvironment. Our results identify SLIT2 as a physiological inhibitor of macropinocytosis and challenge the conventional notion that signals that enhance macropinocytosis negatively regulate cell migration, and vice versa.

Macropinocytosis in Different Cell Types: Similarities and Differences

Macropinocytosis is a unique pathway of endocytosis characterised by the nonspecific internalisation of large amounts of extracellular fluid, solutes and membrane in large endocytic vesicles known as macropinosomes. Macropinocytosis is important in a range of physiological processes, including antigen presentation, nutrient sensing, recycling of plasma proteins, migration and signalling. It has become apparent in recent years from the study of specialised cells that there are multiple pathways of macropinocytosis utilised by different cell types, and some of these pathways are triggered by different stimuli. Understanding the physiological function of macropinocytosis requires knowledge of the regulation and fate of the macropinocytosis pathways in a range of cell types. Here, we compare the mechanisms of macropinocytosis in different primary and immortalised cells, identify the gaps in knowledge in the field and discuss the potential approaches to analyse the function of macropinocytosis in vivo.

Incorporation of the Tat cell-penetrating peptide into nanofibers improves the respective antitumor immune response

A major challenge for the development of anticancer vaccines is the induction of a safe and effective immune response, particularly mediated by CD8+ T lymphocytes, in an adjuvant-free manner. In this respect, we present a simple strategy to improve the specific CD8+ T cell responses using KFE8 nanofibers bearing a Class I (Kb)-restricted peptide epitope (called E. nanofibers) without the use of adjuvant. We demonstrate that incorporation of Tat, a cell-penetrating peptide (CPP) of the HIV transactivator protein, into E. nanofibers remarkably enhanced tumor-specific CD8+ T cell responses. E. nanofibers containing 12.5% Tat peptide (E.Tat_12.5 nanofiber) increased antigen cross-presentation by bone marrow-derived dendritic cells as compared with E. nanofibers, or E. nanofibers containing 25 or 50% the Tat peptide. Uptake of KFE8.Tat_12.5 nanofibers by dendritic cells (DCs) was significantly increased compared with KFE8 nanofiber lacking Tat. Peritoneal and lymph node DCs of mice immunized with E.Tat_12.5 nanofibers exhibited increased presentation of the H2kb-epitope (reminiscent for cross-presentation) compared with DCs obtained from E. nanofiber vaccinated mice. Tetrameric and intracellular cytokine staining revealed that vaccination with E.Tat_12.5 triggered a robust and specific CD8+ T lymphocyte response, which was more pronounced than in mice vaccinated with E. nanofibers alone. Furthermore, E.Tat_12.5 nanofibers were more potent than E. nanofiber to induce antitumor immune response and tumor-infiltrating IFN-γ CD8 T lymphocyte. In terms of cancer vaccine development, we propose that harnessing the nanofiber-based vaccine platform with incorporated Tat peptide could present a simple and promising strategy to induce highly effective antitumor immune response.