Plasma membrane vesicles decorated with glycolipid-anchored antigens and adjuvants via protein transfer as an antigen delivery platform for inhibition of tumor growth

(Patho)Physiology of Glycosylphosphatidylinositol-Anchored Proteins II: Intercellular Transfer of Matter (Inheritance?) That Matters

Glycosylphosphatidylinositol (GPI)-anchored proteins (APs) are anchored at the outer leaflet of the plasma membrane (PM) bilayer by covalent linkage to a typical glycolipid and expressed in all eukaryotic organisms so far studied. Lipolytic release from PMs into extracellular compartments and intercellular transfer are regarded as the main (patho)physiological roles exerted by GPI-APs. The intercellular transfer of GPI-APs relies on the complete GPI anchor and is mediated by extracellular vesicles such as microvesicles and exosomes and lipid-free homo- or heteromeric aggregates, and lipoprotein-like particles such as prostasomes and surfactant-like particles, or lipid-containing micelle-like complexes. In mammalian organisms, non-vesicular transfer is controlled by the distance between donor and acceptor cells/tissues; intrinsic conditions such as age, metabolic state, and stress; extrinsic factors such as GPI-binding proteins; hormones such as insulin; and drugs such as anti-diabetic sulfonylureas. It proceeds either "directly" upon close neighborhood or contact of donor and acceptor cells or "indirectly" as a consequence of the induced lipolytic release of GPI-APs from PMs. Those displace from the serum GPI-binding proteins GPI-APs, which have retained the complete anchor, and become assembled in aggregates or micelle-like complexes. Importantly, intercellular transfer of GPI-APs has been shown to induce specific phenotypes such as stimulation of lipid and glycogen synthesis, in cultured human adipocytes, blood cells, and induced pluripotent stem cells. As a consequence, intercellular transfer of GPI-APs should be regarded as non-genetic inheritance of (acquired) features between somatic cells which is based on the biogenesis and transmission of matter such as GPI-APs and "membrane landscapes", rather than the replication and transmission of information such as DNA. Its operation in mammalian organisms remains to be clarified.

Antigen transfer and its effect on vaccine-induced immune amplification and tolerance

Antigen transfer refers to the process of intercellular information exchange, where antigenic components including nucleic acids, antigen proteins/peptides and peptide-major histocompatibility complexes (p-MHCs) are transmitted from donor cells to recipient cells at the thymus, secondary lymphoid organs (SLOs), intestine, allergic sites, allografts, pathological lesions and vaccine injection sites via trogocytosis, gap junctions, tunnel nanotubes (TNTs), or extracellular vesicles (EVs). In the context of vaccine inoculation, antigen transfer is manipulated by the vaccine type and administration route, which consequently influences, even alters the immunological outcome, i.e., immune amplification and tolerance. Mainly focused on dendritic cells (DCs)-based antigen receptors, this review systematically introduces the biological process, molecular basis and clinical manifestation of antigen transfer.

Influenza Virus-like Particle-Based Hybrid Vaccine Containing RBD Induces Immunity against Influenza and SARS-CoV-2 Viruses

Several approaches have produced an effective vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Since millions of people are exposed to influenza virus and SARS-CoV-2, it is of great interest to develop a two-in-one vaccine that will be able to protect against infection of both viruses. We have developed a hybrid vaccine for SARS-CoV-2 and influenza viruses using influenza virus-like particles (VLP) incorporated by protein transfer with glycosylphosphatidylinositol (GPI)-anchored SARS-CoV-2 RBD fused to GM-CSF as an adjuvant. GPI-RBD-GM-CSF fusion protein was expressed in CHO-S cells, purified and incorporated onto influenza VLPs to develop the hybrid vaccine. Our results show that the hybrid vaccine induced a strong antibody response and protected mice from both influenza virus and mouse-adapted SARS-CoV-2 challenges, with vaccinated mice having significantly lower lung viral titers compared to naive mice. These results suggest that a hybrid vaccine strategy is a promising approach for developing multivalent vaccines to prevent influenza A and SARS-CoV-2 infections.

Metformin reduces PD-L1 on tumor cells and enhances the anti-tumor immune response generated by vaccine immunotherapy

Background

PD-L1 is one of the major immune checkpoints which limits the effectiveness of antitumor immunity. Blockade of PD-L1/PD-1 has been a major improvement in the treatment of certain cancers, however, the response rate to checkpoint blockade remains low suggesting a need for new therapies. Metformin has emerged as a potential new drug for the treatment of cancer due to its effects on PD-L1 expression, T cell responses, and the immunosuppressive environment within tumors. While the benefits of metformin in combination with checkpoint blockade have been reported in animal models, little remains known about its effect on other types of immunotherapy.

Methods

Vaccine immunotherapy and metformin were administered to mice inoculated with tumors to investigate the effect of metformin and TMV vaccine on tumor growth, metastasis, PD-L1 expression, immune cell infiltration, and CD8 T cell phenotype. The effect of metformin on IFN-γ induced PD-L1 expression in tumor cells was assessed by flow cytometry, western blot, and RT-qPCR.

Results

We observed that tumors that respond to metformin and vaccine immunotherapy combination show a reduction in surface PD-L1 expression compared with tumor models that do not respond to metformin. In vitro assays showed that the effect of metformin on tumor cell PD-L1 expression was mediated in part by AMP-activated protein kinase signaling. Vaccination results in increased T cell infiltration in all tumor models, and this was not further enhanced by metformin. However, we observed an increased number of CD8 T cells expressing PD-1, Ki-67, Tim-3, and CD62L as well as increased effector cytokine production after treatment with metformin and tumor membrane vesicle vaccine.

Conclusions

Our data suggest that metformin can synergize with vaccine immunotherapy to augment the antitumor response through tumor-intrinsic mechanisms and also alter the phenotype and function of CD8 T cells within the tumor, which could provide insights for its use in the clinic.

Nanovaccine: an emerging strategy

INTRODUCTION

Vaccination is so far the most effective way of eradicating infections. Rapidly emerging drug resistance against infectious diseases and chemotherapy-related toxicities in cancer warrant immediate vaccine development to save mankind. Subunit vaccines alone, however, fail to elicit sufficiently strong and long-lasting protective immunity against deadly pathogens. Nanoparticle (NP)-based delivery vehicles like microemulsions, liposomes, virosomes, nanogels, micelles and dendrimers offer promising strategies to overcome limitations of traditional vaccine adjuvants. Nanovaccines can improve targeted delivery, antigen presentation, stimulation of body's innate immunity, strong T cell response combined with safety to combat infectious diseases and cancers. Further, nanovaccines can be highly beneficial to generate effective immutherapeutic formulations against cancer.

AREAS COVERED

This review summarizes the emerging nanoparticle strategies highlighting their success and challenges in preclinical and clinical trials in infectious diseases and cancer. It provides a concise overview of current nanoparticle-based vaccines, their adjuvant potential and their cellular delivery mechanisms.

EXPERT OPINION

The nanovaccines (50-250 nm in size) are most efficient in terms of tissue targeting, prolonged circulation and preferential uptake by the professional APCs chiefly due to their small size. More rational designing, improved antigen loading, extensive functionalization and targeted delivery are some of the future goals of ideal nanovaccines.

Dendritic Cells Pulsed with Cytokine-Adjuvanted Tumor Membrane Vesicles Inhibit Tumor Growth in HER2-Positive and Triple Negative Breast Cancer Models

Dendritic cells (DCs) are the most effective antigen presenting cells for the development of T cell responses. The only FDA approved DC-based immunotherapy to date is Sipuleucel-T, which utilizes a fusion protein to stimulate DCs ex vivo with GM-CSF and simultaneously deliver the antigen PAP for prostate cancer. This approach is restricted by the breadth of immunity elicited to a single antigen, and to cancers that have a defined tumor associated antigen. Other multi-antigen approaches have been restricted by poor efficacy of vaccine adjuvants. We have developed a vaccine platform that consists of autologous DCs pulsed with cytokine-adjuvanted tumor membrane vesicles (TMVs) made from tumor tissue, that encapsulate the antigenic landscape of individual tumors. Here we test the efficacy of DCs pulsed with TMVs incorporated with glycolipid-anchored immunostimulatory molecules (GPI-ISMs) in HER2-positive and triple negative breast cancer murine models. Pulsing of DCs with TMVs containing GPI-ISMs results in superior uptake of vesicles, DC activation and cytokine production. Adaptive transfer of TMV-pulsed DCs to tumor bearing mice results in the inhibition of tumor growth, reduction in lung metastasis, and an increase in immune cell infiltration into the tumors. These observations suggest that DCs pulsed with TMVs containing GPI-GM-CSF and GPI-IL-12 can be further developed to be used as a personalized immunotherapy platform for cancer treatment.

Emerging nanomaterials for cancer immunotherapy

Immunotherapy is a unique approach to treat cancer that targets tumours besides triggering the immune cells. It attempts to harness the supremacy and specificity of immune cells for the regression of malignancy. The key strategy of immunotherapy is that it boosts the natural defence and manipulates the immune system at both cellular and molecular levels. Long-lasting anti-tumour response, reduced metastasis, and recurrence can be achieved with immunotherapy than conventional treatments. For example, targeting cytotoxic T-lymphocyte antigen-4 (CTLA4) by monoclonal antibody is reported as an effective strategy against cancer progression in vivo and chimeric antigen receptor (CAR) modified T-cells are known to express a stronger anti-tumour activity. CTLA4 and CAR are, therefore, beneficial in cancer immunotherapy; however, in clinical settings, both are expensive and cause adverse side effects. Nanomaterials have augmented advantages in cancer immunotherapy, besides their utility in effective delivery and diagnostics. In particular, materials based on lipids, polymers, and metals have been sought-after for delivery technologies. Moreover, the surface of nanomaterials can be engineered using ligands, antigens, and antibodies to target immune cells. In this sense, checkpoint inhibitors, cytokines, agonistic antibodies, surface receptors, and engineered T-cells are promising to regulate the immune system against tumours. Therefore, emerging nanomaterials that can be used for the treatment of cancer is the prime focus of this review. The correlation of mode of administration and biodistribution of various nanomaterials is reviewed here. Besides, the acute and chronic side effects and outcome of clinical trials in the context of cancer immunotherapy are discussed.

Cancer Vaccines: Promising Therapeutics or an Unattainable Dream

The advent of cancer immunotherapy has revolutionized the field of cancer treatment and offers cancer patients new hope. Although this therapy has proved highly successful for some patients, its efficacy is not all encompassing and several cancer types do not respond. Cancer vaccines offer an alternate approach to promote anti-tumor immunity that differ in their mode of action from antibody-based therapies. Cancer vaccines serve to balance the equilibrium of the crosstalk between the tumor cells and the host immune system. Recent advances in understanding the nature of tumor-mediated tolerogenicity and antigen presentation has aided in the identification of tumor antigens that have the potential to enhance anti-tumor immunity. Cancer vaccines can either be prophylactic (preventative) or therapeutic (curative). An exciting option for therapeutic vaccines is the emergence of personalized vaccines, which are tailor-made and specific for tumor type and individual patient. This review summarizes the current standing of the most promising vaccine strategies with respect to their development and clinical efficacy. We also discuss prospects for future development of stem cell-based prophylactic vaccines.

The Emerging World of Membrane Vesicles: Functional Relevance, Theranostic Avenues and Tools for Investigating Membrane Function

Lipids are essential components of cell membranes and govern various membrane functions. Lipid organization within membrane plane dictates recruitment of specific proteins and lipids into distinct nanoclusters that initiate cellular signaling while modulating protein and lipid functions. In addition, one of the most versatile function of lipids is the formation of diverse lipid membrane vesicles for regulating various cellular processes including intracellular trafficking of molecular cargo. In this review, we focus on the various kinds of membrane vesicles in eukaryotes and bacteria, their biogenesis, and their multifaceted functional roles in cellular communication, host-pathogen interactions and biotechnological applications. We elaborate on how their distinct lipid composition of membrane vesicles compared to parent cells enables early and non-invasive diagnosis of cancer and tuberculosis, while inspiring vaccine development and drug delivery platforms. Finally, we discuss the use of membrane vesicles as excellent tools for investigating membrane lateral organization and protein sorting, which is otherwise challenging but extremely crucial for normal cellular functioning. We present current limitations in this field and how the same could be addressed to propel a fundamental and technology-oriented future for extracellular membrane vesicles.

Recent Advances in Cell Membrane-Derived Biomimetic Nanotechnology for Cancer Immunotherapy

Immunotherapy will significantly impact the standard of care in cancer treatment. Recent advances in nanotechnology can improve the efficacy of cancer immunotherapy. However, concerns regarding efficiency of cancer nanomedicine, complex tumor microenvironment, patient heterogeneity, and systemic immunotoxicity drive interest in more novel approaches to be developed. For this purpose, biomimetic nanoparticles are developed to make innovative changes in the delivery and biodistribution of immunotherapeutics. Biomimetic nanoparticles have several advantages that can advance the clinical efficacy of cancer immunotherapy. Thus there is a greater push toward the utilization of biomimetic nanotechnology for developing effective cancer immunotherapeutics that demonstrate increased specificity and potency. The recent works and state-of-the-art strategies for anti-tumor immunotherapeutics are highlighted here, and particular emphasis has been given to the applications of cell-derived biomimetic nanotechnology for cancer immunotherapy.

Glycosylation of Cancer Extracellular Vesicles: Capture Strategies, Functional Roles and Potential Clinical Applications

Glycans are major constituents of extracellular vesicles (EVs). Alterations in the glycosylation pathway are a common feature of cancer cells, which gives rise to de novo or increased synthesis of particular glycans. Therefore, glycans and glycoproteins have been widely used in the clinic as both stratification and prognosis cancer biomarkers. Interestingly, several of the known tumor-associated glycans have already been identified in cancer EVs, highlighting EV glycosylation as a potential source of circulating cancer biomarkers. These particles are crucial vehicles of cell–cell communication, being able to transfer molecular information and to modulate the recipient cell behavior. The presence of particular glycoconjugates has been described to be important for EV protein sorting, uptake and organ-tropism. Furthermore, specific EV glycans or glycoproteins have been described to be able to distinguish tumor EVs from benign EVs. In this review, the application of EV glycosylation in the development of novel EV detection and capture methodologies is discussed. In addition, we highlight the potential of EV glycosylation in the clinical setting for both cancer biomarker discovery and EV therapeutic delivery strategies.

Tumor membrane-based vaccine immunotherapy in combination with anti-CTLA-4 antibody confers protection against immune checkpoint resistant murine triple-negative breast cancer

Triple-negative breast cancer (TNBC) afflicts women at a younger age than other breast cancers and is associated with a worse clinical outcome. This poor clinical outcome is attributed to a lack of defined targets and patient-to-patient heterogeneity in target antigens and immune responses. To address such heterogeneity, we tested the efficacy of a personalized vaccination approach for the treatment of TNBC using the 4T1 murine TNBC model. We isolated tumor membrane vesicles (TMVs) from homogenized 4T1 tumor tissue and incorporated glycosyl phosphatidylinositol (GPI)-anchored forms of the immunostimulatory B7-1 (CD80) and IL-12 molecules onto these TMVs to make a TMV vaccine. Tumor-bearing mice were then administered with the TMV vaccine either alone or in combination with immune checkpoint inhibitors. We show that TMV-based vaccine immunotherapy in combination with anti-CTLA-4 mAb treatment upregulated immunomodulatory cytokines in the plasma, significantly improved survival, and reduced pulmonary metastasis in mice compared to either therapy alone. The depletion of CD8⁺ T cells, but not CD4⁺ T cells, resulted in the loss of efficacy. This suggests that the vaccine acts via tumor-specific CD8⁺ T cell immunity. These results suggest TMV vaccine immunotherapy as a potential enhancer of immune checkpoint inhibitor therapies for metastatic triple-negative breast cancer.

Tumor Membrane Vesicle Vaccine Augments the Efficacy of Anti-PD1 Antibody in Immune Checkpoint Inhibitor-Resistant Squamous Cell Carcinoma Models of Head and Neck Cancer

Immune checkpoint inhibitor (ICI) immunotherapy improved the survival of head and neck squamous cell carcinoma (HNSCC) patients. However, more than 80% of the patients are still resistant to this therapy. To test whether the efficacy of ICI therapy can be improved by vaccine-induced immunity, we investigated the efficacy of a tumor membrane-based vaccine immunotherapy in murine models of HNSCC. The tumors, grown subcutaneously, are used to prepare tumor membrane vesicles (TMVs). TMVs are then incorporated with glycolipid-anchored immunostimulatory molecules GPI-B7-1 and GPI-IL-12 by protein transfer to generate the TMV vaccine. This TMV vaccine inhibited tumor growth and improved the survival of mice challenged with SCCVII tumor cells. The tumor-free mice survived for several months, remained tumor-free, and were protected following a secondary tumor cell challenge, suggesting that the TMV vaccine induced an anti-tumor immune memory response. However, no synergy with anti-PD1 mAb was observed in this model. In contrast, the TMV vaccine was effective in inhibiting MOC1 and MOC2 murine oral cancer models and synergized with anti-PD1 mAb in extending the survival of tumor-bearing mice. These observations suggest that tumor tissue based TMV vaccines can be harnessed to develop an effective personalized immunotherapy for HNSCC that can enhance the efficacy of immune checkpoint inhibitors.

Cell-Derived Plasma Membrane Vesicles Are Permeable to Hydrophilic Macromolecules

Giant plasma membrane vesicles (GPMVs) are a widely used experimental platform for biochemical and biophysical analysis of isolated mammalian plasma membranes (PMs). A core advantage of these vesicles is that they maintain the native lipid and protein diversity of the PM while affording the experimental flexibility of synthetic giant vesicles. In addition to fundamental investigations of PM structure and composition, GPMVs have been used to evaluate the binding of proteins and small molecules to cell-derived membranes and the permeation of drug-like molecules through them. An important assumption of such experiments is that GPMVs are sealed, i.e., that permeation occurs by diffusion through the hydrophobic core rather than through hydrophilic pores. Here, we demonstrate that this assumption is often incorrect. We find that most GPMVs isolated using standard preparations are passively permeable to various hydrophilic solutes as large as 40 kDa, in contrast to synthetic giant unilamellar vesicles. We attribute this leakiness to stable, relatively large, and heterogeneous pores formed by rupture of vesicles from cells. Finally, we identify preparation conditions that minimize poration and allow evaluation of sealed GPMVs. These unexpected observations of GPMV poration are important for interpreting experiments utilizing GPMVs as PM models, particularly for drug permeation and membrane asymmetry.

Nanoparticle Delivery of Immunostimulatory Agents for Cancer Immunotherapy

Immunostimulatory agents, including adjuvants, cytokines, and monoclonal antibodies, hold great potential for the treatment of cancer. However, their direct administration often results in suboptimal pharmacokinetics, vulnerability to biodegradation, and compromised targeting. More recently, encapsulation into biocompatible nanoparticulate carriers has become an emerging strategy for improving the delivery of these immunotherapeutic agents. Such approaches can address many of the challenges facing current treatment modalities by endowing additional protection and significantly elevating the bioavailability of the encapsulated payloads. To further improve the delivery efficiency and subsequent immune responses associated with current nanoscale approaches, biomimetic modifications and materials have been employed to create delivery platforms with enhanced functionalities. By leveraging nature-inspired design principles, these biomimetic nanodelivery vehicles have the potential to alter the current clinical landscape of cancer immunotherapy.

Recent development in biodegradable nanovehicle delivery system-assisted immunotherapy

A schematic illustration of BNDS biodegradation and release antigen delivery for assisting immunotherapy.

Recombinant Porcine Reproductive and Respiratory Syndrome Virus Expressing Membrane-Bound Interleukin-15 as an Immunomodulatory Adjuvant Enhances NK and γδ T Cell Responses and Confers Heterologous Protection

Cytokines are often used as adjuvants to improve vaccine immunogenicity, since they are important in initiating and shaping the immune response. The available commercial modified live-attenuated vaccines (MLVs) against porcine reproductive and respiratory syndrome virus (PRRSV) are unable to mount sufficient heterologous protection, as they typically induce weak innate and inadequate T cell responses. In this study, we investigated the immunogenicity and vaccine efficacy of recombinant PRRSV MLVs incorporated with the porcine cytokine interleukin-15 (IL-15) or IL-18 gene fused to a glycosylphosphatidylinositol (GPI) modification signal that can anchor the cytokines to the cell membrane. We demonstrated that both cytokines were successfully expressed on the cell membrane of porcine alveolar macrophages after infection with recombinant MLVs. Pigs vaccinated with recombinant MLVs or the parental Suvaxyn MLV had significantly reduced lung lesions and viral RNA loads in the lungs after heterologous challenge with the PRRSV NADC20 strain. The recombinant MLVs SUV-IL-15 and SUV-IL-18 recovered the inhibition of the NK cell response seen with Suvaxyn MLV. The recombinant MLV SUV-IL-15 significantly increased the numbers of gamma interferon (IFN-γ)-producing cells in circulation at 49 days postvaccination (dpv), especially for IFN-γ-producing CD4^- CD8⁺ T cells and γδ T cells, compared to the Suvaxyn MLV and SUV-IL-18. Additionally, MLV SUV-IL-15-vaccinated pigs also had elevated levels of γδ T cell responses observed at 7 dpv, 49 dpv, and 7 days postchallenge. These data demonstrate that the recombinant MLV expressing membrane-bound IL-15 enhances NK and T cell immune responses after vaccination and confers improved heterologous protection, although this was not statistically significant compared to the parental MLV.IMPORTANCE Porcine reproductive and respiratory syndrome (PRRS) has arguably been the most economically important global swine disease, causing immense economic losses worldwide. The available commercial modified live-attenuated vaccines (MLVs) against PRRS virus (PRRSV) are generally effective against only homologous or closely related virus strains but are ineffective against heterologous strains, partially due to the insufficient immune response induced by the vaccine virus. To improve the immunogenicity of MLVs, in this study, we present a novel approach of using porcine IL-15 or IL-18 as an adjuvant by directly incorporating its encoding gene into a PRRSV MLV and expressing it as an adjuvant. Importantly, we directed the expression of the incorporated cytokines to the cell membrane surface by fusing the genes with a membrane-targeting signal from CD59. The recombinant MLV virus expressing the membrane-bound IL-15 cytokine greatly enhanced NK cell and γδ T cell responses and also conferred improved protection against heterologous challenge with the PRRSV NADC20 strain.

Polymer Vesicles: Modular Platforms for Cancer Theranostics

As an emerging field that is receiving an increasing amount of interest, theranostics is becoming increasingly important in the field of nanomedicine. Among the various smart platforms that have been proposed for use in theranostics, polymer vesicles (or polymersomes) are among the most promising candidates for integration of designated functionalities and modalities. Here, a brief summary of typical theranostic platforms is presented with a focus on modular polymer vesicles. To highlight modularity, the different methodologies for designing therapeutic and diagnostic modules are classified and current examples of theranostic vesicles that excel in both performance and design principle are provided. Finally, future prospects for theranostic polymer vesicles that can be readily prepared with functional modules are proposed. Overall, theranostic polymer vesicles with modular modalities and functions are more promising in nanomedicine than simply being "over-engineered".

Application of Nanocomposites in Cancer Immunotherapy

Despite the clinical advances in oncology, cancer is still the major cause of death worldwide. Recent research demonstrates that the immune system plays a critical role in preventing tumor occurrence and development. The focus on cancer treatment has been shifted from directly targeting the tumor cells to motivating the immune system to achieve this goal. However, the activity of immune system is often suppressed in cancer patients. To boost the anti-tumor immunity against cancers, various nanocomposites have been developed to enhance the efficacy of immunostimulatory agents. Here, we review current advances in nanomaterial-mediated immunotherapy for the treatment of cancer, with an emphasis on applications of nanocomposites as immunoadjuvants in cancer therapy.

Nanotechnology based therapeutic modality to boost anti-tumor immunity and collapse tumor defense

Cancer is still the leading cause of death. While traditional treatments such as surgery, chemotherapy and radiotherapy play dominating roles, recent breakthroughs in cancer immunotherapy indicate that the influence of immune system on cancer development is virtually beyond our expectation. Manipulating the immune system to fight against cancer has been thriving in recent years. Further understanding of tumor anatomy provides opportunities to put a brake on immunosuppression by overcoming tumor intrinsic resistance or modulating tumor microenvironment. Nanotechnology which provides versatile engineered approaches to enhance therapeutic effects may potentially contribute to the development of future cancer treatment modality. In this review, we will focus on the application of nanotechnology both in boosting anti-tumor immunity and collapsing tumor defense.

Immune Protection of Retroviral Vectors Upon Molecular Painting with the Complement Regulatory Protein CD59

Glycosylphosphatidylinositol anchoring is a type of post-translational modification that allows proteins to be presented on the exterior side of the cell membrane. Purified glycosylphosphatidylinositol-anchored protein can spontaneously re-insert into lipid bilayer membranes in a process termed Molecular Painting. Here, we demonstrate the possibility of inserting purified, recombinant CD59 into virus particles produced from a murine retroviral producer cell line. CD59 is a regulator of the complement system that helps protect healthy cells from the lytic activity of the complement cascade. In this study, we could show that Molecular Painting confers protection from complement activity upon murine retroviral vector particles. Indeed, increased infectivity of CD59-modified virus particles was observed upon challenge with human serum, indicating that Molecular Painting is suitable for modulating the immune system in gene therapy or vaccination applications.

Biomedical applications of glycosylphosphatidylinositol-anchored proteins

Glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) use a unique posttranslational modification to link proteins to lipid bilayer membranes. The anchoring structure consists of both a lipid and carbohydrate portion and is highly conserved in eukaryotic organisms regarding its basic characteristics, yet highly variable in its molecular details. The strong membrane targeting property has made the anchors an interesting tool for biotechnological modification of lipid membrane-covered entities from cells through extracellular vesicles to enveloped virus particles. In this review, we will take a closer look at the mechanisms and fields of application for GPI-APs in lipid bilayer membrane engineering and discuss their advantages and disadvantages for biomedicine.

Delivery of therapeutics with nanoparticles: what's new in cancer immunotherapy?

The application of nanotechnology to the treatment of cancer or other diseases has been boosted during the last decades due to the possibility to precise deliver drugs where needed, enabling a decrease in the drug's side effects. Nanocarriers are particularly valuable for potentiating the simultaneous co-delivery of multiple drugs in the same particle for the treatment of heavily burdening diseases like cancer. Immunotherapy represents a new concept in the treatment of cancer and has shown outstanding results in patients treated with check-point inhibitors. Thereby, researchers are applying nanotechnology to cancer immunotherapy toward the development of nanocarriers for delivery of cancer vaccines and chemo-immunotherapies. Cancer nanovaccines can be envisioned as nanocarriers co-delivering antigens and adjuvants, molecules often presenting different physicochemical properties, in cancer therapy. A wide range of nanocarriers (e.g., polymeric, lipid-based and inorganic) allow the co-formulation of these molecules, or the delivery of chemo- and immune-therapeutics in the same system. Finally, there is a trend toward the use of biologically inspired and derived nanocarriers. In this review, we present the recent developments in the field of immunotherapy, describing the different systems proposed by categories: polymeric nanoparticles, lipid-based nanosystems, metallic and inorganic nanosystems and, finally, biologically inspired and derived nanovaccines. WIREs Nanomed Nanobiotechnol 2017, 9:e1421. doi: 10.1002/wnan.1421 For further resources related to this article, please visit the WIREs website.

A Facile Approach to Functionalize Cell Membrane-Coated Nanoparticles

Convenient strategies to provide cell membrane-coated nanoparticles (CM-NPs) with multi-functionalities beyond the natural function of cell membranes would dramatically expand the application of this emerging class of nanomaterials. We have developed a facile approach to functionalize CM-NPs by chemically modifying live cell membranes prior to CM-NP fabrication using a bifunctional linker, succinimidyl-[(N-maleimidopropionamido)-polyethyleneglycol] ester (NHS-PEG-Maleimide). This method is particularly suitable to conjugate large bioactive molecules such as proteins on cell membranes as it establishes a strong anchorage and enable the control of linker length, a critical parameter for maximizing the function of anchored proteins. As a proof of concept, we show the conjugation of human recombinant hyaluronidase, PH20 (rHuPH20) on red blood cell (RBC) membranes and demonstrate that long linker (MW: 3400) is superior to short linker (MW: 425) for maintaining enzyme activity, while minimizing the changes to cell membranes. When the modified membranes were fabricated into RBC membrane-coated nanoparticles (RBCM-NPs), the conjugated rHuPH20 can assist NP diffusion more efficiently than free rHuPH20 in matrix-mimicking gels and the pericellular hyaluronic acid matrix of PC3 prostate cancer cells. After quenching the unreacted chemical groups with polyethylene glycol, we demonstrated that the rHuPH20 modification does not reduce the ultra-long blood circulation time of RBCM-NPs. Therefore, this surface engineering approach provides a platform to functionlize CM-NPs without sacrificing the natural function of cell membranes.