Positively charged liposome functions as an efficient immunoadjuvant in inducing cell-mediated immune response to soluble proteins

A safe and potentiated multi-type HPV L2-E7 nanoparticle vaccine with combined prophylactic and therapeutic activity

Persistent infection with high-risk human papillomavirus (HPV) is widely recognized as the primary cause of cervical and other malignant cancers. There are six licensed prophylactic vaccines available against HPV, but none of them shows any significant therapeutic effect on pre-existing infections or lesions. Thus, a prophylactic vaccine also endowed with therapeutic activity would afford protection regardless of the vaccine recipients HPV-infection status. Here, we describe the refinement and further potentiation of a dual-purpose HPV nanoparticle vaccine (hereafter referred to as cPANHPVAX) relying on eight different HPV L2 peptide epitopes and on the E7 oncoantigens from HPV16 and 18. cPANHPVAX not only induces anti-HPV16 E7 cytotoxic T-cell responses in C57BL/6 mice, but also anti-HPV18 E7 T-cell responses in transgenic mice with the A2.DR1 haplotype. These cytotoxic responses add up to a potent, broad-coverage humoral (HPV-neutralizing) response. cPANHPVAX safety was further improved by deletion of the pRb-binding domains of E7. Our dual-purpose vaccine holds great potential for clinical translation as an immune-treatment capable of targeting active infections as well as established HPV-related malignancies, thus benefiting both uninfected and infected individuals.

Intrinsic immunogenicity of liposomes for tuberculosis vaccines: Effect of cationic lipid and cholesterol

Tuberculosis (TB) is still among the deadliest infectious diseases, hence there is a pressing need for more effective TB vaccines. Cationic liposome subunit vaccines are excellent vaccine candidates offering effective protection with a better safety profile than live vaccines. In this study, we aim to explore intrinsic adjuvant properties of cationic liposomes to maximize immune activation while minimizing aspecific cytotoxicity. To achieve this, we developed a rational strategy to select liposomal formulation compositions and assessed their physicochemical and immunological properties in vitro models using human monocyte-derived dendritic cells (MDDCs). A broad selection of commercially available cationic compounds was tested to prepare liposomes containing Ag85B-ESAT6-Rv2034 (AER) fusion protein antigen. 1,2-Dioleoyl-sn‑glycero-3-ethylphosphocholine (EPC)-based liposomes exhibited the most advantageous activation profile in MDDCs as assessed by cell surface activation markers, cellular uptake, antigen-specific T-cell activation, cytokine production, and cellular viability. The addition of cholesterol to 20 mol% improved the performance of the tested formulations compared to those without it; however, when its concentration was doubled there was no further benefit, resulting in reduced cell viability. This study provides new insights into the role of cationic lipids and cholesterol in liposomal subunit vaccines.

In vivo evaluation of new adjuvant systems based on combination of Salmonella Typhi porins with particulate systems: Liposomes versus polymeric particles

Subunit vaccines that have weak immunogenic activity require adjuvant systems for enhancedcellular and long-acting humoral immune responses. Both lipid-based and polymeric-based particulate adjuvants have been widely investigated to induce the desired immune responses against the subunit vaccines. The adjuvant efficacy of these particulate adjuvants depends upon their physicochemical properties such as particle size, surface charge, shape and their composition. Previously, we showed in vitro effect of adjuvant systems based on combination of chitosan and Salmonella Typhi porins in microparticle or nanoparticle form, which were spherical with positive surface charge. In the present study, we have further developed an adjuvant system based on combination of porins with liposomes (cationic and neutral) and investigated the adjuvant effect of both the liposomal and polymeric systems in BALB/c mice using a model antigen, ovalbumin. Humoral immune responses were determined following priming and booster dose at 15-day intervals. In overall, IgM and IgG levels were induced in the presence of both the liposomal and polymeric adjuvant systems indicating the positive impact of combination with porins. The highest IgM levels were obtained on Day 8, and liposomal adjuvant systems were found to elicit significantly higher IgM levels compared to polymeric systems. IgG levels were increased significantly after booster, particularly more profound with the micro-sized polymeric system when compared to cationic liposomal system with nano-size. Our results demonstrated that the developed particulate systems are promising both as an adjuvant and delivery system, providing enhanced immune responses against subunit antigens, and have the potential for long-term protection.

Liposomes - Human phagocytes interplay in whole blood: effect of liposome design

Nanomedicine holds immense potential for therapeutic manipulation of phagocytic immune cells. However, in vitro studies often fail to accurately translate to the complex in vivo environment. To address this gap, we employed an ex vivo human whole-blood assay to evaluate liposome interactions with immune cells. We systematically varied liposome size, PEG-surface densities and sphingomyelin and ganglioside content. We observed differential uptake patterns of the assessed liposomes by neutrophils and monocytes, emphasizing the importance of liposome design. Interestingly, our results aligned closely with published in vivo observations in mice and patients. Moreover, liposome exposure induced changes in cytokine release and cellular responses, highlighting the potential modulation of immune system. Our study highlights the utility of human whole-blood models in assessing nanoparticle-immune cell interactions and provides insights into liposome design for modulating immune responses.

Immunogenicity of lipid nanoparticles and its impact on the efficacy of mRNA vaccines and therapeutics

Several studies have utilized a lipid nanoparticle delivery system to enhance the effectiveness of mRNA therapeutics and vaccines. However, these nanoparticles are recognized as foreign materials by the body and stimulate innate immunity, which in turn impacts adaptive immunity. Therefore, it is crucial to understand the specific type of innate immune response triggered by lipid nanoparticles. This article provides an overview of the immunological response in the body, explores how lipid nanoparticles activate the innate immune system, and examines the adverse effects and immunogenicity-related development pathways associated with these nanoparticles. Finally, we highlight and explore strategies for regulating the immunogenicity of lipid nanoparticles.

Lipid-based nanoparticles as drug delivery systems for cancer immunotherapy

Immune checkpoint inhibitors (ICIs) have shown remarkable success in cancer treatment. However, in cancer patients without sufficient antitumor immunity, numerous data indicate that blocking the negative signals elicited by immune checkpoints is ineffective. Drugs that stimulate immune activation-related pathways are emerging as another route for improving immunotherapy. In addition, the development of nanotechnology presents a promising platform for tissue and cell type-specific delivery and improved uptake of immunomodulatory agents, ultimately leading to enhanced cancer immunotherapy and reduced side effects. In this review, we summarize and discuss the latest developments in nanoparticles (NPs) for cancer immuno-oncology therapy with a focus on lipid-based NPs (lipid-NPs), including the characteristics and advantages of various types. Using the agonists targeting stimulation of the interferon genes (STING) transmembrane protein as an exemplar, we review the potential of various lipid-NPs to augment STING agonist therapy. Furthermore, we present recent findings and underlying mechanisms on how STING pathway activation fosters antitumor immunity and regulates the tumor microenvironment and provide a summary of the distinct STING agonists in preclinical studies and clinical trials. Ultimately, we conduct a critical assessment of the obstacles and future directions in the utilization of lipid-NPs to enhance cancer immunotherapy.

A liposomal vaccine promotes strong adaptive immune responses via dendritic cell activation in draining lymph nodes

Subunit proteins provide a safe source of antigens for vaccine development especially for intracellular infections which require the induction of strong cellular immune responses. However, those antigens are often limited by their low immunogenicity. In order to achieve effective immune responses, they should be encapsulated into a stable antigen delivery system combined with an appropriate adjuvant. As such cationic liposomes provide an efficient platform for antigen delivery. In the present study, we describe a liposomal vaccine platform for co-delivery of antigens and adjuvants able to elicit strong antigen-specific adaptive immune responses. Liposomes are composed of the cationic lipid dimethyl dioctadecylammonium bromide (DDAB), cholesterol (CHOL) and oleic acid (OA). Physicochemical characterization of the formulations showed that their size was in the range of ∼250 nm with a positive zeta potential which was affected in some cases by the enviromental pH facilitating endosomal escape of potential vaccine cargo. In vitro, liposomes were effectively taken up by bone marrow dendritic cells (BMDCs) and when encapsulated IMQ they promoted BMDCs maturation and activation. Upon in vivo intramuscular administration, liposomes' active drainage to lymph nodes was mediated by DCs, B cells and macrophages. Thus, mice immunization with liposomes having encapsulated LiChimera, a previously characterized anti-leishmanial antigen, and IMQ elicited infiltration of CD11b^low DCs populations in draining LNs followed by increased antigen-specific IgG, IgG2a and IgG1 levels production as well as indcution of antigen-specific CD4⁺ and CD8⁺ T cells. Collectively, the present work provides a proof-of-concept that cationic liposomes composed of DDAB, CHOL and OA adjuvanted with IMQ provide an efficient delivery platform for protein antigens able to induce strong adaptive immune responses via DCs targeting and induction of maturation.

Novel microfluidic swirl mixers for scalable formulation of curcumin loaded liposomes for cancer therapy

Liposomes have been widely used in nanomedicine for the delivery of hydrophobic and hydrophilic anticancer agents. The most common applications of these formulations are vaccines and anticancer formulations (e.g., mRNA, small molecule drugs). However, large-scale production with precise control of size and size distribution of the lipid-based drug delivery systems (DDSs) is one of the major challenges in the pharmaceutical industry. In this study, we used newly designed microfluidic swirl mixers with simple 3D mixing chamber structures to prepare liposomes at a larger scale (up to 320 mL/min or 20 L/h) than the commercially available devices. This design demonstrated high productivity and better control of liposome size and polydispersity index (PDI) than conventional liposome preparation methods. The microfluidic swirl mixer devices were used to produce curcumin-loaded liposomes under different processing conditions which were later characterized and studied in vitro to evaluate their efficiency as DDSs. The obtained results demonstrated that the liposomes can effectively deliver curcumin into cancer cells. Therefore, the microfluidic swirl mixers are promising devices for reproducible and scalable manufacturing of DDSs.

Nanomedicine in leishmaniasis: A promising tool for diagnosis, treatment and prevention of disease - An update overview

Leishmaniasis is a neglected tropical disease that has a wide spectrum of clinical manifestations, ranging from visceral to cutaneous, with millions of new cases and thousands of deaths notified every year. The severity of the disease and its various clinical forms are determined by the species of the causative agent, Leishmania, as well as the host's immune response. Major challenges still exist in the diagnosis and treatment of leishmaniasis, and there is no vaccine available to prevent this disease in humans. Nanotechnology has emerged as a promising tool in a variety of fields. In this review, we highlight the main and most recent advances in nanomedicine to improve the diagnosis and treatment, as well as for the development of vaccines, for leishmaniasis. Nanomaterials are nanometric in size and can be produced by a variety of materials, including lipids, polymers, ceramics, and metals, with varying structures and morphologies. Nanotechnology can be used as biosensors to detect antibodies or antigens, thus improving the sensitivity and specificity of such immunological and molecular diagnostic tests. While in treatment, nanomaterials can act as drug carriers or, be used directly, to reduce any toxic effects of drug compounds to the host and to be more selective towards the parasite. Furthermore, preclinical studies show that different nanomaterials can carry different Leishmania antigens, or even act as adjuvants to improve a Th1 immune response in an attempt to produce an effective vaccine.

Direct nose to the brain nanomedicine delivery presents a formidable challenge

This advanced review describes the anatomical and physiological barriers and mechanisms impacting nanomedicine translocation from the nasal cavity directly to the brain. There are significant physiological and anatomical differences in the nasal cavity, olfactory area, and airflow reaching the olfactory epithelium between humans and experimentally studied species that should be considered when extrapolating experimental results to humans. Mucus, transporters, and tight junction proteins present barriers to material translocation across the olfactory epithelium. Uptake of nanoparticles through the olfactory mucosa and translocation to the brain can be intracellular via cranial nerves (intraneuronal) or other cells of the olfactory epithelium, or extracellular along cranial nerve pathways (perineural) and surrounding blood vessels (perivascular, the glymphatic system). Transport rates vary greatly among the nose to brain pathways. Nanomedicine physicochemical properties (size, surface charge, surface coating, and particle stability) can affect uptake efficiency, which is usually less than 5%. Incorporation of therapeutic agents in nanoparticles has been shown to produce pharmacokinetic and pharmacodynamic benefits. Assessment of adverse effects has included olfactory mucosa toxicity, ciliotoxicity, and olfactory bulb and brain neurotoxicity. The results have generally suggested the investigated nanomedicines do not present significant toxicity. Research needs to advance the understanding of nanomedicine translocation and its drug cargo after intranasal administration is presented. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

Attacking the Intruder at the Gate: Prospects of Mucosal Anti SARS-CoV-2 Vaccines

The sudden outbreak of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic in December 2019 caused crises and health emergencies worldwide. The rapid spread of the virus created an urgent need for the development of an effective vaccine and mass immunization to achieve herd immunity. Efforts of scientific teams at universities and pharmaceutical companies around the world allowed for the development of various types of preparations and made it possible to start the vaccination process. However, it appears that the developed vaccines are not effective enough and do not guarantee long-lasting immunity, especially for new variants of SARS-CoV-2. Considering this problem, it is promising to focus on developing a Coronavirus Disease 2019 (COVID-19) mucosal vaccine. Such a preparation applied directly to the mucous membranes of the upper respiratory tract might provide an immune barrier at the primary point of virus entry into the human body while inducing systemic immunity. A number of such preparations against SARS-CoV-2 are already in various phases of preclinical and clinical trials, and several of them are very close to being accepted for general use, constituting a milestone toward pandemic containment.

I.p.-injected cationic liposomes are retained and accumulate in peritoneally disseminated tumors

Intraperitoneal (i.p) chemotherapy is an attractive approach to treat peritoneally disseminated cancers by delivering therapeutic agents directly to the peritoneal cavity where some disseminated tumors are located. Cationic liposomes (CLs) have been used as a viable delivery carrier for i.p. chemotherapy to improve the peritoneal retention of anticancer agents. However, there are no reports on the fate of CLs following i.p. administration to the peritoneal cavity in the presence of disseminated tumors. We prepared a tumor xenograft murine model of peritoneally disseminated gastric cancer by i.p. inoculation of human gastric cancer cells and followed the fate of either CLs or PEGylated CLs (PEG-CLs) after i.p. injection in the model. I.p.-injected CLs were retained in peritoneal cavity for at least 3 days post-injection as a result of clustering with ascites fluid proteins, mainly albumin, while i.p. PEG-CLs was rapidly cleared from the peritoneal cavity to the circulation within 3 h post-injection. Importantly, i.p. CLs efficiently accumulated in the targeted disseminated tumor cells, but not in other abdominal organs including liver, spleen, and kidney. The tumor selectivity upon i.p. administration of CLs may be associated with the lymphatic drainage system. A lipoplex formulation composed of CLs with short hairpin RNA (shRNA) against luciferase, a model therapeutic agent, suppressed luciferase activity in peritoneally disseminated tumors by 80%, with no cytokine secretion in serum. This suggests that i.p. CLs can efficiently deliver a therapeutic agent to peritoneally disseminated tumors with few systemic adverse events. These results suggest that i.p. treatment with CLs or non-PEGylated lipoplexes may be a promising approach for the treatment of peritoneally disseminated cancers through their ability to selectively deliver therapeutic agents to i.p. target sites with minimal systemic adverse events.

Pharmaceutical Aspects and Clinical Evaluation of COVID-19 Vaccines

COVID-19, the disease caused by the novel severe acute respiratory syndrome-associated coronavirus 2 (SARS-CoV-2), was first detected in December 2019 and has since morphed into a global pandemic claiming over 2.4 million human lives and severely impacting global economy. The race for a safe and efficacious vaccine was thus initiated with government agencies as well as major pharmaceutical companies as frontrunners. An ideal vaccine would activate multiple arms of the adaptive immune system to generate cytotoxic T cell responses as well as neutralizing antibody responses, while avoiding pathological or deleterious immune responses that result in tissue damage or exacerbation of the disease. Developing an effective vaccine requires an inter-disciplinary effort involving virology, protein biology, biotechnology, immunology and pharmaceutical sciences. In this review, we provide a brief overview of the pathology and immune responses to SARS-CoV-2, which are fundamental to vaccine development. We then summarize the rationale for developing COVID-19 vaccines and provide novel insights into vaccine development from a pharmaceutical science perspective, such as selection of different antigens, adjuvants, delivery platforms and formulations. Finally, we review multiple clinical trial outcomes of novel vaccines in terms of safety and efficacy.

Antigen Uptake After Intradermal Microinjection Depends on Antigen Nature and Formulation, but Not on Injection Depth

The skin is an attractive alternative administration route for allergy vaccination, as the skin is rich in dendritic cells (DCs) and is easily accessible. In the skin multiple subsets of DCs with distinct roles reside at different depths. In this study antigen (=allergen for allergy) formulations were injected in ex vivo human skin in a depth-controlled manner by using a hollow microneedle injection system. Biopsies were harvested at the injection site, which were then cultured for 72 h. Subsequently, the crawled-out cells were collected from the medium and analyzed with flow cytometry. Intradermal administration of ovalbumin (OVA, model antigen) solution at various depths in the skin did not affect the migration and maturation of DCs. OVA was taken up efficiently by the DCs, and this was not affected by the injection depth. In contrast, Bet v 1, the major allergen in birch pollen allergy, was barely taken up by dermal DCs (dDCs). Antigens were more efficiently taken up by CD14⁺ dDCs than CD1a⁺ dDCs, which in turn were more efficient at taken up antigen than Langerhans cells. Subsequently, both OVA and Bet v 1 were formulated in cationic and anionic liposomes, which altered antigen uptake drastically following intradermal microinjection. While OVA uptake was reduced by formulation in liposomes, Bet v 1 uptake in dDCs was increased by encapsulation in both cationic and anionic liposomes. This highlights the potential use of liposomes as adjuvant in intradermal allergy vaccine delivery. In conclusion, we observed that antigen uptake after intradermal injection was not affected by injection depth, but varied between different antigens and formulation.

Recent Advances in Hyperthermia Therapy-Based Synergistic Immunotherapy

The past decades have witnessed hyperthermia therapy (HTT) as an emerging strategy against malignant tumors. Nanomaterial-based photothermal therapy (PTT) and magnetic hyperthermia (MHT), as highly effective and noninvasive treatment models, offer advantages over other strategies in the treatment of different types of tumors. However, both PTT and MHT cannot completely cure cancer due to recurrence and distal metastasis. In recent years, cancer immunotherapy has attracted widespread attention owing to its capability to activate the body's own natural defense to identify, attack, and eradicate cancer cells. Significant efforts have been devoted to studying the activated immune responses caused by hyperthermia-ablated tumors. In this article, the synergistic mechanism of HTT in immunotherapy, including immunogenic cell death and reversal of the immunosuppressive tumor microenvironment is discussed. The reports of the combination of HTT or HTT-based multimodal therapy with immunotherapy, including immunoadjuvant exploitation, immune checkpoint blockade therapy, and adoptive cellular immunotherapy are summarized. As highlighted, these strategies could achieve synergistically enhanced therapeutic outcomes against both primary tumors and metastatic lesions, prevent cancer recurrence, and prolong the survival period. Finally, current challenges and prospective developments in HTT-synergized immunotherapy are also reviewed.

The dry powder formulation of mixed cross-linked dextran microspheres and tetanus toxoid-loaded trimethyl chitosan nanospheres as a potent adjuvant for nasal delivery system

OBJECTIVES

The present study aimed to determine the immunoadjuvant efficacy of mixed cross-linked dextran microspheres (CDM) and tetanus toxoid (TT)-loaded trimethyl chitosan (TMC) nanospheres in dry powder form.

MATERIALS AND METHODS

The TMC nanoparticles (NPs) containing TT were produced using the ionic gelation method. Co-administration of TT-loaded TMC NPs and CDM as an absorption enhancer was performed to improve immunity against the antigen. Dry powder formulations were delivered via the nasal route in a rabbit model.

RESULTS

Among immunization groups, mixing of CDM with TT encapsulated in TMC NPs could elicit the highest titer of systemic IgG antibody. Furthermore, the addition of CDM to TT-loaded TMC enhanced the sIgA response relative to the TT solution.

CONCLUSION

The TMC NPs had a considerable effect on mucosal and systemic immunity against the TT antigen. Therefore, the CDM excipient can be utilized for nasal immunization to elevate systemic and mucosal responses.

Nanoparticles as Smart Carriers for Enhanced Cancer Immunotherapy

Cancer immunotherapy has emerged as a promising strategy for the treatment of many forms of cancer by stimulating body's own immune system. This therapy not only eradicates tumor cells by inducing strong anti-tumor immune response but also prevent their recurrence. The clinical cancer immunotherapy faces some insurmountable challenges including high immune-mediated toxicity, lack of effective and targeted delivery of cancer antigens to immune cells and off-target side effects. However, nanotechnology offers some solutions to overcome those limitations, and thus can potentiate the efficacy of immunotherapy. This review focuses on the advancement of nanoparticle-mediated delivery of immunostimulating agents for efficient cancer immunotherapy. Here we have outlined the use of the immunostimulatory nanoparticles as a smart carrier for effective delivery of cancer antigens and adjuvants, type of interactions between nanoparticles and the antigen/adjuvant as well as the factors controlling the interaction between nanoparticles and the receptors on antigen presenting cells. Besides, the role of nanoparticles in targeting/activating immune cells and modulating the immunosuppressive tumor microenvironment has also been discussed extensively. Finally, we have summarized some theranostic applications of the immunomodulatory nanomaterials in treating cancers based on the earlier published reports.

Liposome-Based Drug Delivery Systems in Cancer Immunotherapy

Cancer immunotherapy has shown remarkable progress in recent years. Nanocarriers, such as liposomes, have favorable advantages with the potential to further improve cancer immunotherapy and even stronger immune responses by improving cell type-specific delivery and enhancing drug efficacy. Liposomes can offer solutions to common problems faced by several cancer immunotherapies, including the following: (1) Vaccination: Liposomes can improve the delivery of antigens and other stimulatory molecules to antigen-presenting cells or T cells; (2) Tumor normalization: Liposomes can deliver drugs selectively to the tumor microenvironment to overcome the immune-suppressive state; (3) Rewiring of tumor signaling: Liposomes can be used for the delivery of specific drugs to specific cell types to correct or modulate pathways to facilitate better anti-tumor immune responses; (4) Combinational therapy: Liposomes are ideal vehicles for the simultaneous delivery of drugs to be combined with other therapies, including chemotherapy, radiotherapy, and phototherapy. In this review, different liposomal systems specifically developed for immunomodulation in cancer are summarized and discussed.

Synthesis and Cytotoxicity Studies of Wood-Based Cationic Cellulose Nanocrystals as Potential Immunomodulators

Polysaccharides have been shown to have immunomodulatory properties. Modulation of the immune system plays a crucial role in physiological processes as well as in the treatment and/or prevention of autoimmune and infectious diseases. Cellulose nanocrystals (CNCs) are derived from cellulose, the most abundant polysaccharide on the earth. CNCs are an emerging class of crystalline nanomaterials with exceptional physico-chemical properties for high-end applications and commercialization prospects. The aim of this study was to design, synthesize, and evaluate the cytotoxicity of a series of biocompatible, wood-based, cationic CNCs as potential immunomodulators. The anionic CNCs were rendered cationic by grafting with cationic polymers having pendant +NMe3 and +NH3 moieties. The success of the synthesis of the cationic CNCs was evidenced by Fourier transform infrared spectroscopy, dynamic light scattering, zeta potential, and elemental analysis. No modification in the nanocrystals rod-like shape was observed in transmission electron microscopy and atomic force microscopy analyses. Cytotoxicity studies using three different cell-based assays (MTT, Neutral Red, and LIVE/DEAD®) and three relevant mouse and human immune cells indicated very low cytotoxicity of the cationic CNCs in all tested experimental conditions. Overall, our results showed that cationic CNCs are suitable to be further investigated as immunomodulators and potential vaccine nanoadjuvants.

The Impact of Engineered Silver Nanomaterials on the Immune System

Over the last decades there has been a tremendous volume of research efforts focused on engineering silver-based (nano)materials. The interest in silver has been mostly driven by the element capacity to kill pathogenic bacteria. In this context, the main area of application has been medical devices that are at significant risk of becoming colonized by bacteria and subsequently infected. However, silver nanomaterials have been incorporated in a number of other commercial products which may or may not benefit from antibacterial protection. The rapid expansion of such products raises important questions about a possible adverse influence on human health. This review focuses on examining currently available literature and summarizing the current state of knowledge of the impact of silver (nano)materials on the immune system. The review also looks at various surface modification strategies used to generate silver-based nanomaterials and the immunomodulatory potential of these materials. It also highlights the immune response triggered by various silver-coated implantable devices and provides guidance and perspective towards engineering silver nanomaterials for modulating immunological consequences.

Toxicological profile of lipid-based nanostructures: are they considered as completely safe nanocarriers?

Nanoparticles are ubiquitous in the environment and are widely used in medical science (e.g. bioimaging, diagnosis, and drug therapy delivery). Due to unique physicochemical properties, they are able to cross many barriers, which is not possible for traditional drugs. Nevertheless, exposure to NPs and their following interactions with organelles and macromolecules can result in negative effects on cells, especially, they can induce cytotoxicity, epigenicity, genotoxicity, and cell death. Lipid-based nanomaterials (LNPs) are one of the most important achievements in drug delivery mainly due to their superior physicochemical and biological characteristics, particularly its safety. Although they are considered as the completely safe nanocarriers in biomedicine, the lipid composition, the surfactant, emulsifier, and stabilizer used in the LNP preparation, and surface electrical charge are important factors that might influence the toxicity of LNPs. According to the author's opinion, their toxicity profile should be evaluated case-by-case regarding the intended applications. Since there is a lack of all-inclusive review on the various aspects of LNPs with an emphasis on toxicological profiles including cyto-genotoxiciy, this comprehensive and critical review is outlined.

Current and New Approaches for Mucosal Vaccine Delivery

Mucosal surfaces are the interface between the host’s internal milieu and the external environment, and they have dual functions, serving as physical barriers to foreign antigens and as accepting sites for vital materials. Mucosal vaccines are more favored to prevent mucosal infections from the portal of entry. Although mucosal vaccination has many advantages, licensed mucosal vaccines are scarce. The most widely studied mucosal routes are oral and intranasal. Licensed oral and intranasal vaccines are composed mostly of whole cell killed or live attenuated microorganisms serving as both delivery systems and built-in adjuvants. Future mucosal vaccines should be made with more purified antigen components, which will be relatively less immunogenic. To induce robust protective immune responses against well-purified vaccine antigens, an effective mucosal delivery system is an essential requisite. Recent developments in biomaterials and nanotechnology have enabled many innovative mucosal vaccine trials. For oral vaccination, the vaccine delivery system should be able to stably carry antigens and adjuvants and resist harsh physicochemical conditions in the stomach and intestinal tract. Besides many nano/microcarrier tools generated by using natural and chemical materials, the development of oral vaccine delivery systems using food materials should be more robustly researched to expand vaccine coverage of gastrointestinal infections in developing countries. For intranasal vaccination, the vaccine delivery system should survive the very active mucociliary clearance mechanisms and prove safety because of the anatomical location of nasal cavity separated by a thin barrier. Future mucosal vaccine carriers, regardless of administration routes, should have certain common characteristics. They should maintain stability in given environments, be mucoadhesive, and have the ability to target specific tissues and cells.

Biocompatibility in regenerative nanomedicine

Biocompatibility is a very common word that is used within biomaterial science and used for description of the interactions between the foreign material and the body. However, the meaning of biocompatibility as well as the mechanisms that collectively constitutes is still unclear. With the advance of nanotechnology, new concerns have been observed related to biocompatibility of these biomaterials. Due to their small size and variability of their physical and chemical properties, nanoparticles' (NP) distribution within the body and interactions with the target cells and tissues are highly variable. Here, we tried to provide an overview about NPs, the concept of biocompatibility and biocompatibility-related issues in nanomedicine and several different NPs.

A surface charge dependent enhanced Th1 antigen-specific immune response in lymph nodes by transfersome-based nanovaccine-loaded dissolving microneedle-assisted transdermal immunization

The efficient delivery of vaccines to draining lymph nodes and the induction of robust local immune responses are crucial for immunotherapy.

A polymer-free, biomimicry drug self-delivery system fabricated via a synergistic combination of bottom-up and top-down approaches

Compared to conventional carrier-assistant drug delivery systems (DDSs), drug self-delivery systems (DSDSs) have advantages of unprecedented drug loading capacity, minimized carrier-related toxicity and ease of preparation. However, the colloidal stability and blood circulation time of DSDSs still need to be improved. Here we report on the development of a novel biomimicry drug self-delivery system by the integration of a top-down cell membrane complexing technique into our self-delivery multifunctional nano-platform made from bottom-up approach that contains 100% active pharmaceutical ingredients (API) of Pheophorbide A and Irinotecan conjugates (named PI). Compared to conventional cell membrane coated nanoparticles with polymer framework as core and relatively low drug loading, this system consisting of red blood cell membrane vesicles complexed PI (RBC-PI) is polymer-free with up to 50% API loading. RBC-PI exhibited 10 times higher area under curve in pharmacokinetic study and much lower macrophage uptake compared with the parent PI nanoparticles. RBC-PI retained the excellent chemophototherapeutic effects of the PI nanoparticles, but possessed superior anti-cancer efficacy with prolonged blood circulation, improved tumor delivery, and enhanced photothermal effects in animal models. This system represents a novel example of using cell membrane complexing technique for effective surface modification of DSDSs. This is also an innovative study to form a polymer-free cell membrane nanoparticle complexing with positive surface charged materials. This biomimicry DSDS takes advantages of the best features from both systems to make up for each other's shortcomings and posed all the critical features for an ideal drug delivery system.

Nanoparticles for Immune Stimulation Against Infection, Cancer, and Autoimmunity

Vaccination using nanocarrier-based delivery systems has recently emerged as a promising approach for meeting the continued challenge posed by infectious diseases and cancer. A diverse portfolio of nanocarriers of various sizes, compositions, and physical parameters have now been developed, and this diversity provides an opportunity for the rational design of vaccines that can mediate targeted delivery of various antigens and adjuvants or immune regulatory agents in ways unachievable with classical vaccination approaches. This flexibility allows control over the characteristics of vaccine-elicited immune responses such that they can be tailored to be effective in circumstances where classical vaccines have failed. Furthermore, the utility of nanocarrier-based immune modulation extends to the treatment of autoimmune disease where precisely targeted inhibition of immune responses is desirable. Clearly, the selection of appropriate nanocarriers, antigens, adjuvants, and other components underpins the efficacy of these nanoimmune interventions. Herein, we provide an overview of currently available nanocarriers of various types and their physical and pharmacological properties with the goal of providing a resource for researchers exploring nanomaterial-based approaches for immune modulation and identify some information gaps and unexplored questions to help guide future investigation.

Robust mucosal and systemic responses against HTLV-1 by delivery of multi-epitope vaccine in PLGA nanoparticles

In this investigation, the immunogenicity of HTLV-1 fusion epitope-loaded PLGA nanoparticles (NPs) was assessed in the absence or presence of co-encapsulated CpG ODN adjuvant, in a mice model. For this purpose, the multi-epitope chimera including Tax, env, and gag immunodominant HTLV-1 epitopes was encapsulated in biodegradable PLGA NPs with or without CpG adjuvant. PLGA nanospheres produced by a double emulsion method had a size of <200 nm, and encapsulation efficiency of chimera antigen was 85%. The release profile of radiolabeled chimera indicated that only 17.4% and 20.1% of chimera were released from PLGA NPs without or with co-encapsulated CPG ODN during one month, respectively. The PLGA formulations significantly elevated titers of IgG1, IgG2a, and sIgA antibodies, as well as IL-10, and IFN-γ cytokines and also reduced the amount of TGF-β1 production relative to the other vaccines. Additionally, co-delivery of chimera and CpG ODN in PLGA NPs significantly promoted cellular and mucosal responses compared to the incorporation of CpG and chimera antigen. In summary, these results revealed that the sustained release of chimera from PLGA as an efficient polymeric system elicited potent cell-mediated and mucosal immunity without inflammatory responses against HTLV-1. Therefore, the proper design of vaccine formulation and immunization strategy are crucial factors to construct an efficient vaccine.

Liposomal vaccine formulations as prophylactic agents: design considerations for modern vaccines

Vaccinology is one of the most important cornerstones in modern medicine, providing better quality of life. The human immune system is composed of innate and adaptive immune processes that interplay when infection occurs. Innate immunity relies on pathogen-associated molecular patterns which are recognized by pathogen recognition receptors localized in antigen presenting cells. After antigen processing and presentation, CD4+ T cell polarization occurs, further leading to B cell and CD8+ activation and humoral and cell-mediated adaptive immune responses. Liposomes are being employed as vaccine technologies and their design is of importance to ensure proper immune responses. Physicochemical parameters like liposome size, charge, lamellarity and bilayer fluidity must be completely understood to ensure optimal vaccine stability and efficacy. Liposomal vaccines can be developed to target specific immune cell types for the induction of certain immune responses. In this review, we will present promising liposomal vaccine approaches for the treatment of important viral, bacterial, fungal and parasitic infections (including tuberculosis, TB). Cationic liposomes are the most studied liposome types due to their enhanced interaction with the negatively charged immune cells. Thus, a special section on the cationic lipid dimethyldioctadecylammonium and TB is also presented.

Vaccine adjuvants: smart components to boost the immune system

Vaccination is an effective approach to prevent the consequences of infectious diseases. Vaccines strengthen immunity and make individuals resistant to infections with pathogens. Although conventional vaccines are highly immunogenic, they are associated with some safety issues. Subunit vaccines are safe, but they require adjuvants to stimulate the immune system because of their weaker immunogenicity. Adjuvants are entities incorporated into vaccines to increase the immunogenic responses of antigens. They play a crucial role in increasing the potency and efficacy of vaccines. Different adjuvants have different modes of action; therefore, a better understanding of their immunology could provide guidance for the development of novel adjuvants. Numerous studies have been conducted using different types of adjuvants to characterize their potency and safety; however, in practice, only few are used in human or animal vaccines. This review aims to introduce the different modes of action of adjuvants and give insight into the types of adjuvants that possess the greatest potential for adjuvanticity.

Structure and Computation in Immunoreagent Design: From Diagnostics to Vaccines

Novel immunological tools for efficient diagnosis and treatment of emerging infections are urgently required. Advances in the diagnostic and vaccine development fields are continuously progressing, with reverse vaccinology and structural vaccinology (SV) methods for antigen identification and structure-based antigen (re)design playing increasingly relevant roles. SV, in particular, is predicted to be the front-runner in the future development of diagnostics and vaccines targeting challenging diseases such as AIDS and cancer. We review state-of-the-art methodologies for structure-based epitope identification and antigen design, with specific applicative examples. We highlight the implications of such methods for the engineering of biomolecules with improved immunological properties, potential diagnostic and/or therapeutic uses, and discuss the perspectives of structure-based rational design for the production of advanced immunoreagents.

Nanoliposomes carrying HER2/neu-derived peptide AE36 with CpG-ODN exhibit therapeutic and prophylactic activities in a mice TUBO model of breast cancer

This study was designed to prepare and characterize nanoliposomal vaccine formulation encapsulating AE36 HER2/neu-derived peptide with or without CpG and evaluate the immunologic and therapeutic responses of that in BALB/c mice model of Her2 overexpressing breast cancer. AE36 was encapsulated in liposomes composed of DOTAP, DOPE and Cholesterol (DDC) or DD with. The formulations could induce both CD8+ and CD4+ responses and stimulate production of cytokines which was detected by Enzyme-linked immunospot assay (ELISpot) kits, cytotoxicity test and intracellular cytokine assay by flow cytometry. The formulation showed both therapeutic and prophylactic effects in BALB/c mice bearing Her2⁺ breast cancer. DDC+CpG showed the best effect in prophylactic study and DD+pG showed the best effect in therapeutic study, which both of them decreased the size of tumors significantly. The engineered nanoliposomes containing AE36 could be a candidate vaccine for the treatment or prophylaxis of HER2⁺ breast cancer and merits further investigation.

Dendrimer-conjugated peptide vaccine enhances clearance of Chlamydia trachomatis genital infection

Peptide-based vaccines have emerged in recent years as promising candidates in the prevention of infectious diseases. However, there are many challenges to maintaining in vivo peptide stability and enhancement of peptide immunogenicity to generate protective immunity which enhances clearance of infections. Here, a dendrimer-based carrier system is proposed for peptide-based vaccine delivery, and shows its anti-microbial feasibility in a mouse model of Chlamydia trachomatis. Chlamydiae are the most prevalent sexually transmitted bacteria worldwide, and also the causal agent of trachoma, the leading cause of preventable infectious blindness. In spite of the prevalence of this infectious agent and the many previous vaccine-related studies, there is no vaccine commercially available. The carrier system proposed consists of generation 4, hydroxyl-terminated, polyamidoamine (PAMAM) dendrimers (G4OH), to which a peptide mimic of a chlamydial glycolipid antigen-Peptide 4 (Pep4, AFPQFRSATLLL) was conjugated through an ester bond. The ester bond between G4OH and Pep4 is expected to break down mainly in the intracellular environment for antigen presentation. Pep4 conjugated to dendrimer induced Chlamydia-specific serum antibodies after subcutaneous immunizations. Further, this new vaccine formulation significantly protected immunized animals from vaginal challenge with infectious Chlamydia trachomatis, and it reduced infectious loads and tissue (genital tract) damage. Pep4 conjugated to G4OH or only mixed with peptide provided enhanced protection compared to Pep4 and adjuvant (i.e. alum), suggesting a potential adjuvant effect of the PAMAM dendrimer. Combined, these results demonstrate that hydroxyl-terminated PAMAM dendrimer is a promising polymeric nanocarrier platform for the delivery of peptide vaccines and this approach has potential to be expanded to other infectious intracellular bacteria and viruses of public health significance.

Platform technologies for modern vaccine manufacturing

Improved understanding of antigenic components and their interaction with the immune system, as supported by computational tools, permits a sophisticated approach to modern vaccine design. Vaccine platforms provide an effective tool by which strategically designed peptide and protein antigens are modularized to enhance their immunogenicity. These modular vaccine platforms can overcome issues faced by traditional vaccine manufacturing and have the potential to generate safe vaccines, rapidly and at a low cost. This review introduces two promising platforms based on virus-like particle and liposome, and discusses the methodologies and challenges.

Vaccine technologies: From whole organisms to rationally designed protein assemblies

Vaccines have been the single most significant advancement in public health, preventing morbidity and mortality in millions of people annually. Vaccine development has traditionally focused on whole organism vaccines, either live attenuated or inactivated vaccines. While successful for many different infectious diseases whole organisms are expensive to produce, require culture of the infectious agent, and have the potential to cause vaccine associated disease in hosts. With advancing technology and a desire to develop safe, cost effective vaccine candidates, the field began to focus on the development of recombinantly expressed antigens known as subunit vaccines. While more tolerable, subunit vaccines tend to be less immunogenic. Attempts have been made to increase immunogenicity with the addition of adjuvants, either immunostimulatory molecules or an antigen delivery system that increases immune responses to vaccines. An area of extreme interest has been the application of nanotechnology to vaccine development, which allows for antigens to be expressed on a particulate delivery system. One of the most exciting examples of nanovaccines are rationally designed protein nanoparticles. These nanoparticles use some of the basic tenants of structural biology, biophysical chemistry, and vaccinology to develop protective, safe, and easily manufactured vaccines. Rationally developed nanoparticle vaccines are one of the most promising candidates for the future of vaccine development.

A semi-synthetic whole parasite vaccine designed to protect against blood stage malaria

Although attenuated malaria parasitized red blood cells (pRBCs) are promising vaccine candidates, their application in humans may be restricted for ethical and regulatory reasons. Therefore, we developed an organic microparticle-based delivery platform as a whole parasite malaria-antigen carrier to mimic pRBCs. Killed blood stage parasites were encapsulated within liposomes that are targeted to antigen presenting cells (APCs). Mannosylated lipid core peptides (MLCPs) were used as targeting ligands for the liposome-encapsulated parasite antigens. MLCP-liposomes, but not unmannosylated liposomes, were taken-up efficiently by APCs which then significantly upregulated expression of MHC-ll and costimulatory molecules, CD80 and CD86. Two such vaccines using rodent model systems were constructed - one with Plasmodium chabaudi and the other with P. yoelii. MLCP-liposome vaccines were able to control the parasite burden and extended the survival of mice. Thus, we have demonstrated an alternative delivery system to attenuated pRBCs with similar vaccine efficacy and added clinical advantages. Such liposomes are promising candidates for a human malaria vaccine.

STATEMENT OF SIGNIFICANCE

Attenuated whole parasite-based vaccines, by incorporating all parasite antigens, are very promising candidates, but issues relating to production, storage and safety concerns are significantly slowing their development. We therefore developed a semi-synthetic whole parasite malaria vaccine that is easily manufactured and stored. Two such prototype vaccines (a P. chabaudi and a P. yoelii vaccine) have been constructed. They are non-infectious, highly immunogenic and give good protection profiles. This semi-synthetic delivery platform is an exciting strategy to accelerate the development of a licensed malaria vaccine. Moreover, this strategy can be potentially applied to a wide range of pathogens.

In vitro toxicity of cationic micelles and liposomes in cultured human hepatocyte (HepG2) and lung epithelial (A549) cell lines

The aim of this study was to compare the effects of cationic micelle and liposome drug delivery systems on liver and lung cells in a toxicological in vitro screening model, with observations on cytotoxicity and genotoxicity. A screening battery was established for assessment of a broad range of parameters related to adverse effects. Clear concentration response effects were observed related to impairment of mitochondrial function, membrane integrity and oxidative stress markers, but no effect was observed on genotoxicity. The adverse effects were highest for the liposomes. The High Content Screening seems optimal for initial screening of adverse effects, and combined with standard cytotoxicity measurements initial screening can be performed for predictive toxicological screening.