Manipulating calcium homeostasis with nanoplatforms for enhanced cancer therapy

Calcium ions (Ca2+) are indispensable and versatile metal ions that play a pivotal role in regulating cell metabolism, encompassing cell survival, proliferation, migration, and gene expression. Aberrant Ca2+ levels are frequently linked to cell dysfunction and a variety of pathological conditions. Therefore, it is essential to maintain Ca2+ homeostasis to coordinate body function. Disrupting the balance of Ca2+ levels has emerged as a potential therapeutic strategy for various diseases, and there has been extensive research on integrating this approach into nanoplatforms. In this review, the current nanoplatforms that regulate Ca2+ homeostasis for cancer therapy are first discussed, including both direct and indirect approaches to manage Ca2+ overload or inhibit Ca2+ signalling. Then, the applications of these nanoplatforms in targeting different cells to regulate their Ca2+ homeostasis for achieving therapeutic effects in cancer treatment are systematically introduced, including tumour cells and immune cells. Finally, perspectives on the further development of nanoplatforms for regulating Ca2+ homeostasis, identifying scientific limitations and future directions for exploitation are offered.

Recent Advances in Inhaled Nanoformulations of Vaccines and Therapeutics Targeting Respiratory Viral Infections

With the rapid outbreak of respiratory viral infections, various biological (e.g. vaccines, peptides, recombinant proteins, antibodies and genes) and antiviral agents (e.g. ribavirin, palivizumab and valaciclovir) have been successfully developed for the treatment of respiratory virus infections such as influenza, respiratory syncytial virus and SARS-CoV-2 infections. These therapeutics are conventionally delivered via oral, intramuscular or injection route and are associated with several adverse events due to systemic toxicity. The inherent in vivo instability of biological therapeutics may hinder them from being administered without proper formulations. Therefore, we have witnessed a boom in nanotechnology coupled with a needle-free administration approach such as the inhalation route for the delivery of complex therapeutics to treat respiratory infections. This review discussed the recent advances in the inhalation strategies of nanoformulations that target virus respiratory infections.

Nanovaccines to combat virus-related diseases

The invention and application of vaccines have made tremendous contributions to fight against pandemics for human beings. However, current vaccines still have shortcomings such as insufficient cellular immunity, the lack of cross-protection, and the risk of antibody-dependent enhancement (ADE). Thus, the prevention and control of pandemic viruses including Ebola Virus, human immunodeficiency virus (HIV), Influenza A viruses, Zika, and current SARS-CoV-2 are still extremely challenging. Nanoparticles with unique physical, chemical, and biological properties, hold promising potentials for the development of ideal vaccines against these viral infections. Moreover, the approval of the first nanoparticle-based mRNA vaccine BNT162b has established historic milestones that greatly inspired the clinical translation of nanovaccines. Given the safety and extensive application of subunit vaccines, and the rapid rise of mRNA vaccines, this review mainly focuses on these two vaccine strategies and provides an overview of the nanoparticle-based vaccine delivery platforms to tackle the current and next global health challenges. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Meeting vaccine formulation challenges in an emergency setting: Towards the development of accessible vaccines

Vaccination is considered one of the most successful strategies to prevent infectious diseases. In the event of a pandemic or epidemic, the rapid development and distribution of the vaccine to the population is essential to reduce mortality, morbidity and transmission. As seen during the COVID-19 pandemic, the production and distribution of vaccines has been challenging, in particular for resource-constrained settings, essentially slowing down the process of achieving global coverage. Pricing, storage, transportation and delivery requirements of several vaccines developed in high-income countries resulted in limited access for low-and-middle income countries (LMICs). The capacity to manufacture vaccines locally would greatly improve global vaccine access. In particular, for the development of classical subunit vaccines, the access to vaccine adjuvants is a pre-requisite for more equitable access to vaccines. Vaccine adjuvants are agents required to augment or potentiate, and possibly target the specific immune response to such type of vaccine antigens. Openly accessible or locally produced vaccine adjuvants may allow for faster immunization of the global population. For local research and development of adjuvanted vaccines to expand, knowledge on vaccine formulation is of paramount importance. In this review, we aim to discuss the optimal characteristics of a vaccine developed in an emergency setting by focusing on the importance of vaccine formulation, appropriate use of adjuvants and how this may help overcome barriers for vaccine development and production in LMICs, achieve improved vaccine regimens, delivery and storage requirements.

Local and systemic immune responses induced by intranasal immunization with biomineralized foot-and-mouth disease virus-like particles

Introduction

Foot-and-mouth disease virus (FMDV) infects the host by invading mucosal epithelial cells of the respiratory or digestive tract. Therefore, establishing a specific antiviral mucosal immune barrier can effectively block viral invasion.

Methods

We evaluated local mucosal and systemic immune responses elicited by intranasal immunization of mice with foot-and-mouth disease (FMD) calcium phosphate mineralized virus-like particles (CaP-VLPs) and tested whether three commercial mucosal adjuvants enhanced the immunogenicity of the antigen. The biosafety of the vaccine was verified through gross observation and pathological analysis of the lungs.

Results

CaP-VLPs effectively induced secretion of IgA (sIgA) from multiple sites in mouse mucosa and produced anti-FMD-specific IgG in the serum. Splenic lymphocytes specifically proliferated and secreted IFN-γ following antigen stimulation, indicating the vaccine can induce a certain level of cellular immune response. Finally, the pathological examination confirmed that CaP-VLPs did not cause substantial damage to the lungs of animals after immunization via mucosal administration. Notably, the vaccine mixed with S adjuvant increased the content of sIgA and serum IgG, and the high level of IgG in serum was maintained at least 7 weeks.

Discussion

Overall, this study reveals that FMD CaP-VLPs can induce good local mucosal immune and systemic immune response through intranasal immunization, and the immune response was specifically enhanced by S adjuvant. These data support that CaP-VLPs-S as a candidate mucosal vaccine for the prevention of FMD vaccine infection.

Emerging peptide-based nanovaccines: From design synthesis to defense against cancer and infection

Peptide-based vaccines, which form one of the most potent vaccine platforms, offer exclusive advantages over classical vaccines that use whole organisms or proteins. However, peptides alone are still poor stability and weak immunogenicity, thus need a delivery system that can overcome these shortcomings. Currently, nanotechnology has been extensively utilized to address this issue. Nanovaccines, as new formulations of vaccines using nanoparticles (NPs) as carriers or adjuvants, are undergoing development instead of conventional vaccines. Indeed, peptide-based nanovaccine is a rapidly developing field of research that is emerging out of the confluence of antigenic peptides with the nano-delivery system. In this review, we shed light on the rational design and preparation strategies based on various nanomaterials of peptide-based nanovaccines, and we spotlight progress in the development of peptide-based nanovaccines against cancer and infectious diseases. Finally, the future prospects for development of peptide-based nanovaccines are presented.

Bioinspired nano-vaccine construction by antigen pre-degradation for boosting cancer personalized immunotherapy

Cancer vaccines-based cancer immunotherapy has drawn widespread concern. However, insufficient cancer antigens and inefficient antigen presentation lead to low immune response rate, which greatly restrict the practical application of cancer vaccines. Here, inspired by intracellular proteasome-mediated protein degradation pathway, we report an antigen presentation simplification strategy by extracellular degradation of antigen proteins into peptides with proteolytic enzyme for improving the utilization of cancer antigens and arousing restricted cancer immunity. The pre-degraded antigen peptides are first validated to exhibit an increased capacity on antigen-presenting cell (APC) stimulation compared with proteins and still reserve antigen specificity and major histocompatibility complex (MHC) affinity. Furthermore, by coordinating the pre-degraded peptides with calcium phosphate nanoparticles (CaP), a CaP-peptide vaccine (CaP-Pep) is constructed, which is verified to induce an efficient personalized immune response in vivo for multi-model anti-cancer therapy. Notably, this bioinspired strategy based on extracellular enzymatic hydrolysis for vaccine construction is not only applicable for multiple types of cancers, but also shows great potential in expanding immunology fields and translational medicine.

Delivery of toll-like receptor 3 ligand poly(I:C) to the liver by calcium phosphate nanoparticles conjugated with an F4/80 antibody exerts an anti-hepatitis B virus effect in a mouse model

Hepatitis B virus (HBV) is a global health issue, but currently available anti-HBV drugs have limited success. Previously, introduction of the Toll-like receptor (TLR)-3 ligand poly(I:C) to the liver via hydrodynamic injection (HI) was shown to effectively suppress HBV replication in a chronic HBV replication mouse model. However, this method cannot be applied in human beings. To improve the liver targeting of poly(I:C) via intravenous injection, calcium phosphate nanoparticles (CPNs) carrying poly(I:C) with or without antibodies were constructed, and their anti-HBV effects were investigated. We found that significantly more anti-F4/80-conjugated and IgG2α-conjugated nanoparticles were taken up in liver cells both in vivo and in vitro. In addition, these nanoparticles produced pronounced immunostimulatory effects in vitro in primary liver cells. Importantly, treatment with nanoparticles carrying poly(I:C) increased the production of intrahepatic cytokines and chemokines and enhanced T cell responses, significantly reducing HBsAg, HBeAg and HBV DNA levels in the mice. Compared to nonconjugated and isotype-antibody-conjugated nanoparticles, the anti-F4/80-conjugated nanoparticles demonstrated the strongest anti-HBV effects. In summary, nanoparticles carrying poly(I:C) conjugated with an F4/80 antibody promoted liver targeting, and they may represent a suitable alternative to HI for future anti-HBV treatment. STATEMENT OF SIGNIFICANCE: HBV chronically infects approximately 250 million individuals worldwide but current anti-HBV drugs have limited success. Introduction of toll-like receptor 3 ligand poly(I:C) into liver by hydrodynamic injection has been proven to promote HBV clearance in mouse model. However, this technique is not clinically suitable for human patients. We have constructed calcium phosphate nanoparticles carrying poly(I:C) with specific antibody targeting liver nonparenchymal cells. The uptake into relevant liver cells and the anti-HBV effects were studied. After intravenous injection into mice, the uptake rate of anti-F4/80-conjugated nanoparticels was enhanced in liver, and these nanoparticles exert effective anti-HBV effects in vivo. This may provide important insight into future HBV immunotherapy based on nanoparticle-mediated drug delivery.

Metal-Based Nanomaterials: Work as Drugs and Carriers against Viral Infections

Virus infection is one of the threats to the health of organisms, and finding suitable antiviral agents is one of the main tasks of current researchers. Metal ions participate in multiple key reaction stages of organisms and maintain the important homeostasis of organisms. The application of synthetic metal-based nanomaterials as an antiviral therapy is a promising new research direction. Based on the application of synthetic metal-based nanomaterials in antiviral therapy, we summarize the research progress of metal-based nanomaterials in recent years. This review analyzes the three inhibition pathways of metal nanomaterials as antiviral therapeutic materials against viral infections, including direct inactivation, inhibition of virus adsorption and entry, and intracellular virus suppression; it further classifies and summarizes them according to their inhibition mechanisms. In addition, the use of metal nanomaterials as antiviral drug carriers and vaccine adjuvants is summarized. The analysis clarifies the antiviral mechanism of metal nanomaterials and broadens the application in the field of antiviral therapy.

Novel immunomodulatory properties of low dose cytarabine entrapped in a mannosylated cationic liposome

Cancer treatment remains unsatisfactory with high rates of recurrence and metastasis. Immunomodulatory agents capable of promoting cellular antitumor immunity while inhibiting the local immunosuppressive tumor microenvironment could greatly improve cancer treatment. We have developed a multi-targeted mannosylated cationic liposome delivery system containing muramyl dipeptide (DS) and low doses of the chemotherapeutic agent cytarabine (Ara-C). Immunomodulation of primary immune cells and immortalized cancer cell lines by Ara-C/DS was assessed by measuring cytokine levels and surface marker expression. As a proof of concept, the generation of targeted cellular immunity was investigated in the context of responses to viral antigens. This report is the first demonstrating that Ara-C combined with DS can modulate immune responses and revert immunosuppression as evidenced by increased IFN-γ and IL-12p40 without changes in IL-10 in peripheral blood mononuclear cells, and increased CD80 and decreased CD163 on immunosuppressive macrophages. Furthermore, Ara-C/DS increased MHC class I expression on cancer cells while increasing the production of antigen-specific IFN-γ⁺ CD8⁺ T cells in viral peptide-challenged lymphocytes from both humans and vaccinated mice. Taken together, these results are the first to document immunomodulatory properties of Ara-C linked with recognition of antigens and potentially the generation of antitumor immune memory.

Biological and Medical Applications of Calcium Phosphate Nanoparticles

Calcium phosphate nanoparticles have a high biocompatibility and biodegradability due to their chemical similarity to human hard tissue, for example, bone and teeth. They can be used as efficient carriers for different kinds of biomolecules such as nucleic acids, proteins, peptides, antibodies, or drugs, which alone are not able to enter cells where their biological effect is required. They can be loaded with cargo molecules by incorporating them, unlike solid nanoparticles, and also by surface functionalization. This offers protection, for example, against nucleases, and the possibility for cell targeting. If such nanoparticles are functionalized with fluorescing dyes, they can be applied for imaging in vitro and in vivo. Synthesis, functionalization and cell uptake mechanisms of calcium phosphate nanoparticles are discussed together with applications in transfection, gene silencing, imaging, immunization, and bone substitution. Biodistribution data of calcium phosphate nanoparticles in vivo are reviewed.

Biomaterials-based formulations and surfaces to combat viral infectious diseases

Rapidly growing viral infections are potent risks to public health worldwide. Accessible virus-specific antiviral vaccines and drugs are therapeutically inert to emerging viruses, such as Zika, Ebola, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Therefore, discovering ways to prevent and control viral infections is among the foremost medical challenge of our time. Recently, innovative technologies are emerging that involve the development of new biomaterial-based formulations and surfaces endowed with broad-spectrum antiviral properties. Here, we review emerging biomaterials technologies for controlling viral infections. Relevant advances in biomaterials employed with nanotechnology to inactivate viruses or to inhibit virus replication and further their translation in safe and effective antiviral formulations in clinical trials are discussed. We have included antiviral approaches based on both organic and inorganic nanoparticles (NPs), which offer many advantages over molecular medicine. An insight into the development of immunomodulatory scaffolds in designing new platforms for personalized vaccines is also considered. Substantial research on natural products and herbal medicines and their potential in novel antiviral drugs are discussed. Furthermore, to control contagious viral infections, i.e., to reduce the viral load on surfaces, current strategies focusing on biomimetic anti-adhesive surfaces through nanostructured topography and hydrophobic surface modification techniques are introduced. Biomaterial surfaces functionalized with antimicrobial polymers and nanoparticles against viral infections are also discussed. We recognize the importance of research on antiviral biomaterials and present potential strategies for future directions in applying these biomaterial-based approaches to control viral infections and SARS-CoV-2.

Non-viral COVID-19 vaccine delivery systems

The novel corona virus termed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread throughout the globe at a formidable speed, causing tens of millions of cases and more than one million deaths in less than a year of its report in December 2019. Since then, companies and research institutions have raced to develop SARS-CoV-2 vaccines, ranging from conventional viral and protein-based vaccines to those that are more cutting edge, including DNA- and mRNA-based vaccines. Each vaccine exhibits a different potency and duration of efficacy, as determined by the antigen design, adjuvant molecules, vaccine delivery platforms, and immunization method. In this review, we will introduce a few of the leading non-viral vaccines that are under clinical stage development and discuss delivery strategies to improve vaccine efficacy, duration of protection, safety, and mass vaccination.

An Insight into Nanomedicinal Approaches to Combat Viral Zoonoses

BACKGROUND

Emerging viral zoonotic diseases are one of the major obstacles to secure the "One Health" concept under the current scenario. Current prophylactic, diagnostic and therapeutic approaches often associated with certain limitations and thus proved to be insufficient for customizing rapid and efficient combating strategy against the highly transmissible pathogenic infectious agents leading to the disastrous socio-economic outcome. Moreover, most of the viral zoonoses originate from the wildlife and poor knowledge about the global virome database renders it difficult to predict future outbreaks. Thus, alternative management strategy in terms of improved prophylactic vaccines and their delivery systems; rapid and efficient diagnostics and effective targeted therapeutics are the need of the hour.

METHODS

Structured literature search has been performed with specific keywords in bibliographic databases for the accumulation of information regarding current nanomedicine interventions along with standard books for basic virology inputs.

RESULTS

Multi-arrayed applications of nanomedicine have proved to be an effective alternative in all the aspects regarding the prevention, diagnosis, and control of zoonotic viral diseases. The current review is focused to outline the applications of nanomaterials as anti-viral vaccines or vaccine/drug delivery systems, diagnostics and directly acting therapeutic agents in combating the important zoonotic viral diseases in the recent scenario along with their potential benefits, challenges and prospects to design successful control strategies.

CONCLUSION

This review provides significant introspection towards the multi-arrayed applications of nanomedicine to combat several important zoonotic viral diseases.

Promising Adjuvants and Platforms for Influenza Vaccine Development

Influenza is one of the major threats to public health. Current influenza vaccines cannot provide effective protection against drifted or shifted influenza strains. Researchers have considered two important strategies to develop novel influenza vaccines with improved immunogenicity and broader protective efficacy. One is applying fewer variable viral antigens, such as the haemagglutinin stalk domain. The other is including adjuvants in vaccine formulations. Adjuvants are promising and helpful boosters to promote more rapid and stronger immune responses with a dose-sparing effect. However, few adjuvants are currently licensed for human influenza vaccines, although many potential candidates are in different trials. While many advantages have been observed using adjuvants in influenza vaccine formulations, an improved understanding of the mechanisms underlying viral infection and vaccination-induced immune responses will help to develop new adjuvant candidates. In this review, we summarize the works related to adjuvants in influenza vaccine research that have been used in our studies and other laboratories. The review will provide perspectives for the utilization of adjuvants in developing next-generation and universal influenza vaccines.

Anti-Influenza Strategies Based on Nanoparticle Applications

Influenza virus has the potential for being one of the deadliest viruses, as we know from the pandemic's history. The influenza virus, with a constantly mutating genome, is becoming resistant to existing antiviral drugs and vaccines. For that reason, there is an urgent need for developing new therapeutics and therapies. Despite the fact that a new generation of universal vaccines or anti-influenza drugs are being developed, the perfect remedy has still not been found. In this review, various strategies for using nanoparticles (NPs) to defeat influenza virus infections are presented. Several categories of NP applications are highlighted: NPs as immuno-inducing vaccines, NPs used in gene silencing approaches, bare NPs influencing influenza virus life cycle and the use of NPs for drug delivery. This rapidly growing field of anti-influenza methods based on nanotechnology is very promising. Although profound research must be conducted to fully understand and control the potential side effects of the new generation of antivirals, the presented and discussed studies show that nanotechnology methods can effectively induce the immune responses or inhibit influenza virus activity both in vitro and in vivo. Moreover, with its variety of modification possibilities, nanotechnology has great potential for applications and may be helpful not only in anti-influenza but also in the general antiviral approaches.

Genetic immunization against hepatitis B virus with calcium phosphate nanoparticles in vitro and in vivo

Calcium phosphate nanoparticles were loaded with plasmid DNA and toll-like receptor ligands (TLR), i.e. CpG or flagellin, to activate antigen-presenting cells (APCs) like dendritic cells (DCs). The functionalized nanoparticles were studied in vitro on HeLa, C2C12 and BHK-21 cell lines, focusing on the expression of two specific proteins. EGFP-DNA, encoding for enhanced green fluorescent protein (EGFP), was used as a model plasmid to optimize the transfection efficiency in vitro by fluorescence microscopy and flow cytometry. Calcium phosphate nanoparticles loaded with TLR ligands and plasmid DNA encoding for the hepatitis B virus surface antigen (pHBsAg) were evaluated by in vitro and in vivo immunization experiments to identify a possible candidate for a prophylactic hepatitis B virus (HBV) vaccine. The nanoparticles induced a strong expression of HBsAg in the three cell lines. In splenocytes, the expression of the co-stimulatory molecules CD80 and CD86 was enhanced. After intramuscular injection in mice, the nanoparticles induced the expression of HBsAg, the antigen-specific T cell response, and the antigen-specific antibody response (IgG1). STATEMENT OF SIGNIFICANCE: Hepatitis B is one of the most frequent viral infections worldwide. For preventive immunization, nanoparticles can be used which carry both an adjuvant (a stimulatory molecule) and DNA encoding for a viral antigen. After administration of such nanoparticles to cells, they are taken up by cells where the DNA is transcribed into the viral antigen (a protein). This viral antigen is inducing a virus-specific immune response. This was shown both by in vitro cell culture as well as by an extensive in vivo study in mice.

Protein-only nanocapsules induce cross-presentation in dendritic cells, demonstrating potential as an antigen delivery system

Templating has been demonstrated to be an efficient method of nanocapsule preparation. However, there have been no reports of using protein-only nanocapsules as an antigen delivery system. Such a system would enable the delivery of antigen without additional polymers. This study focused on defining the structural and cellular characteristics of nanocapsules consisting of antigen (ovalbumin) alone, synthesized by the templating method using highly monodispersed solid core mesoporous shell (SC/MS) and mesoporous (MS) silica nanoparticles of 410 nm and 41 nm in diameter, respectively. The synthesized ovalbumin nanocapsules were homogeneous in structure, and cellular uptake was observed in DC2.4 murine immature dendritic cells with minimal cytotoxicity. The nanocapsules were localized intracellularly and induced antigen presentation by the cross-presentation pathway. The templating system, using SC/MS and MS silica nanoparticles, was demonstrated to be an effective nanocapsule synthesis method for a new antigen delivery system.

Integrating Biomaterials and Immunology to Improve Vaccines Against Infectious Diseases

Despite the success of vaccines in preventing many infectious diseases, effective vaccines against pathogens with ongoing challenges - such as HIV, malaria, and tuberculosis - remain unavailable. The emergence of new pathogen variants, the continued prevalence of existing pathogens, and the resurgence of yet other infectious agents motivate the need for new, interdisciplinary approaches to direct immune responses. Many current and candidate vaccines, for example, are poorly immunogenic, provide only transient protection, or create risks of regaining pathogenicity in certain immune-compromised conditions. Recent advances in biomaterials research are creating new potential to overcome these challenges through improved formulation, delivery, and control of immune signaling. At the same time, many of these materials systems - such as polymers, lipids, and self-assembly technologies - may achieve this goal while maintaining favorable safety profiles. This review highlights ways in which biomaterials can advance existing vaccines to safer, more efficacious technologies, and support new vaccines for pathogens that do not yet have vaccines. Biomaterials that have not yet been applied to vaccines for infectious disease are also discussed, and their potential in this area is highlighted.

Calcium Phosphate Nanoparticle-Based Vaccines as a Platform for Improvement of HIV-1 Env Antibody Responses by Intrastructural Help

Incorporation of immunodominant T-helper epitopes of licensed vaccines into virus-like particles (VLP) allows to harness T-helper cells induced by the licensed vaccines to provide intrastructural help (ISH) for B-cell responses against the surface proteins of the VLPs. To explore whether ISH could also improve antibody responses to calcium phosphate (CaP) nanoparticle vaccines we loaded the nanoparticle core with a universal T-helper epitope of Tetanus toxoid (p30) and functionalized the surface of CaP nanoparticles with stabilized trimers of the HIV-1 envelope (Env) resulting in Env-CaP-p30 nanoparticles. In contrast to soluble Env trimers, Env containing CaP nanoparticles induced activation of naïve Env-specific B-cells in vitro. Mice previously vaccinated against Tetanus raised stronger humoral immune responses against Env after immunization with Env-CaP-p30 than mice not vaccinated against Tetanus. The enhancing effect of ISH on anti-Env antibody levels was not attended with increased Env-specific IFN-γ CD4 T-cell responses that otherwise may potentially influence the susceptibility to HIV-1 infection. Thus, CaP nanoparticles functionalized with stabilized HIV-1 Env trimers and heterologous T-helper epitopes are able to recruit heterologous T-helper cells induced by a licensed vaccine and improve anti-Env antibody responses by intrastructural help.

Peritoneal Cells Mediate Immune Responses and Cross-Protection Against Influenza A Virus

Intraperitoneal inoculation with live influenza A virus confers protection against intranasal infections in mice and ferrets. However, the responses of peritoneal cells to influenza A virus have not been investigated. Here we show that intraperitoneal inoculation with A/WSN/1933 (H1N1) virus induced virus-reactive IgG production in the peritoneal cavity in mice. The infection resulted in substantial but transient B cell and macrophage depletion along with massive neutrophil infiltration, but virus growth was not detected. Influenza A viruses bound to α-2,6-linked sialic acids of B cells and macrophages and induced apoptotic death of peritoneal cavity cells. However, re-infection with A/WSN/1933 virus did not have adverse effects on immune cells most likely because of the neutralizing antibodies produced in response to the first exposure. Infection of BALB/c mice with A/WSN/1933 induced cross-protection against an otherwise lethal intraperitoneal dose of A/Hongkong/4801/2014 (H3N2) virus. This information suggests that immunological responses in the peritoneal cavity can induce effective defense against future virus infection. Considering the unexpected potent immunoregulatory activity of the peritoneal cells against influenza viruses, we suggest that comparative studies on various immune reactions after infection through different routes may contribute to better selection of vaccination routes in development of efficacious influenza vaccines.

Review of potential health risks associated with nanoscopic calcium phosphate

Calcium phosphate is applied in many products in biomedicine, but also in toothpastes and cosmetics. In some cases, it is present in nanoparticulate form, either on purpose or after degradation or mechanical abrasion. Possible concerns are related to the biological effect of such nanoparticles. A thorough literature review shows that calcium phosphate nanoparticles as such have no inherent toxicity but can lead to an increase of the intracellular calcium concentration after endosomal uptake and lysosomal degradation. However, cells are able to clear the calcium from the cytoplasm within a few hours, unless very high doses of calcium phosphate are applied. The observed cytotoxicity in some cell culture studies, mainly for unfunctionalized particles, is probably due to particle agglomeration and subsequent sedimentation onto the cell layer, leading to a very high local particle concentration, a high particle uptake, and subsequent cell death. There is no risk from an oral uptake of calcium phosphate nanoparticles due to their rapid dissolution in the stomach. The risk from dermal or mucosal uptake is very low. Calcium phosphate nanoparticles can enter the bloodstream by inhalation, but no adverse effects have been observed, except for a prolonged exposition to high particle doses. Calcium phosphate nanoparticles inside the body (e.g. after implantation or due to abrasion) do not pose a risk as they are typically resorbed and dissolved by osteoclasts and macrophages. There is no indication for a significant influence of the calcium phosphate phase or the particle shape (e.g. spherical or rod-like) on the biological response. In summary, the risk associated with an exposition to nanoparticulate calcium phosphate in doses that are usually applied in biomedicine, health care products, and cosmetics is very low and most likely not present at all.

STATEMENT OF SIGNIFICANCE

Calcium phosphate is a well-established biomaterial. However, there are occasions when it occurs in a nanoparticulate form (e.g. as nanoparticle or as nanoparticulate bone substitution material) or after abrasion from a calcium phosphate-coated metal implant. In the light of the current discussion on the safety of nanoparticles, there have been concerns about potential adverse effects of nano-calcium phosphate, e.g. in a statement of a EU study group from 2016 about possible dangers associated with non-spherical nano-hydroxyapatite in cosmetics. In the US, there was a discussion in 2016 about the dangers of nano-calcium phosphate in babyfood. In this review, the potential exposition routes for nano-calcium phosphate are reviewed, with special emphasis on its application as biomaterial.

Non-human papillomaviruses for gene delivery in vitro and in vivo

Papillomavirus capsids are known to have the ability to package DNA plasmids and deliver them both in vitro and in vivo. Of all known papillomavirus types, human papillomaviruses (HPVs) are by far the most intensely studied. Although HPVs work well as gene transfer vectors, their use is limited as most individuals are exposed to this virus either through a HPV vaccination or natural infection. To circumvent these constraints, we produced pseudovirions (PsVs) of ten non-human papillomavirus types and tested their transduction efficiencies in vitro. PsVs based on Macaca fascicularis papillomavirus-11 and Puma concolor papillomavirus-1 were further tested in vivo. Intramuscular transduction by PsVs led to months-long expression of a reporter plasmid, indicating that PsVs have potential as gene delivery vectors.

Induction of Type I Interferons by Therapeutic Nanoparticle-Based Vaccination Is Indispensable to Reinforce Cytotoxic CD8+ T Cell Responses During Chronic Retroviral Infection

T cell dysfunction and immunosuppression are characteristic for chronic viral infections and contribute to viral persistence. Overcoming these burdens is the goal of new therapeutic strategies to cure chronic infectious diseases. We recently described that therapeutic vaccination of chronic retrovirus infected mice with a calcium phosphate (CaP) nanoparticle (NP)-based vaccine carrier, functionalized with CpG and viral peptides is able to efficiently reactivate the CD8⁺ T cell response and improve the eradication of virus infected cells. However, the mechanisms underlying this effect were largely unclear. While type I interferons (IFNs I) are considered to drive T cell exhaustion by persistent immune activation during chronic viral infection, we here describe an indispensable role of IFN I induced by therapeutic vaccination to efficiently reinforce cytotoxic CD8⁺ T cells (CTL) and improve control of chronic retroviral infection. The induction of IFN I is CpG dependent and leads to significant IFN signaling indicated by upregulation of IFN stimulated genes. By vaccinating chronically retrovirus-infected mice lacking the IFN I receptor (IFNAR^−/−) or by blocking IFN I signaling in vivo during therapeutic vaccination, we demonstrate that IFN I signaling is necessary to drive full reactivation of CTLs. Surprisingly, we also identified an impaired suppressive capability of regulatory T cells in the presence of IFNα, which implicates an important role for vaccine-induced IFNα in the regulation of the T cell response during chronic retroviral infection. Our data suggest that inducing IFN I signaling in conjunction with the presentation of viral antigens can reactivate immune functions and reduce viral loads in chronic infections. Therefore, we propose CaP NPs as potential therapeutic tool to treat chronic infections.

Carbonate Apatite Nanoparticles Act as Potent Vaccine Adjuvant Delivery Vehicles by Enhancing Cytokine Production Induced by Encapsulated Cytosine-Phosphate-Guanine Oligodeoxynucleotides

Vaccine adjuvants that can induce not only antigen-specific antibody responses but also Th1-type immune responses and CD8⁺ cytotoxic T lymphocyte responses are needed for the development of vaccines against infectious diseases and cancer. Of many available adjuvants, oligodeoxynucleotides (ODNs) with unmethylated cytosine-phosphate-guanine (CpG) motifs are the most promising for inducing the necessary immune responses, and these adjuvants are currently under clinical trials in humans. However, the development of novel delivery vehicles that enhance the adjuvant effects of CpG ODNs, subsequently increasing the production of cytokines such as type-I interferons (IFNs), is highly desirable. In this study, we demonstrate the potential of pH-responsive biodegradable carbonate apatite (CA) nanoparticles as CpG ODN delivery vehicles that can enhance the production of type-I IFNs (such as IFN-α) relative to that induced by CpG ODNs and can augment the adjuvant effects of CpG ODNs in vivo. In contrast to CpG ODNs, CA nanoparticles containing CpG ODNs (designated CA-CpG) induced significant IFN-α production by mouse dendritic cells and human peripheral blood mononuclear cells in vitro; and production of interleukin-12, and IFN-γ was higher in CA-CpG-treated groups than in CpG ODNs groups. In addition, treatment with CA-CpG resulted in higher cytokine production in draining lymph nodes than did treatment with CpG ODNs in vivo. Furthermore, vaccination with CA-CpG plus an antigen, such as ovalbumin or influenza virus hemagglutinin, resulted in higher antigen-specific antibody responses and CD8⁺ cytotoxic T lymphocyte responses in vivo, in an interleukin-12- and type-I IFN-dependent manner, than did vaccination with the antigen plus CpG ODNs; in addition, the efficacy of the vaccine against influenza virus was higher with CA-CpG as the adjuvant than with CpG ODNs as the adjuvant. These data show the potential of CA nanoparticles to serve as CpG ODN delivery vehicles that increase the production of cytokines, especially IFN-α, induced by CpG ODNs and thus augment the efficacy of CpG ODNs as adjuvants. We expect that the strategy reported herein will facilitate the design and development of novel adjuvant delivery vehicles for vaccines.

Delivery of the TLR ligand poly(I:C) to liver cells in vitro and in vivo by calcium phosphate nanoparticles leads to a pronounced immunostimulation

The selective activation of the immune system is a concurrent problem in the treatment of persistent diseases like viral infections (e.g. hepatitis). For the delivery of the toll-like receptor ligand poly(I:C), an immunostimulatory action was discovered earlier by hydrodynamic injection. However, this technique is not clinically transferable to human patients. A modular system where the immunoactive toll-like-receptor ligand 3 (TLR-3) poly(I:C) was incorporated into calcium phosphate nanoparticles was developed. The nanoparticles had a hydrodynamic diameter of 275nm and a zeta potential of +20mV, measured by dynamic light scattering. The diameter of the solid core was 120nm by scanning electron microscopy. In vitro, the nanoparticle uptake was investigated after 1 and 24h of incubation of THP-1 cells (macrophages) with nanoparticles by fluorescence microscopy. After intravenous injection into BALB/c and C57BL/6J mice, respectively, the in vivo uptake was especially prominent in lung and liver, 1 and 3h after the injection. Pronounced immunostimulatory effects of the nanoparticles were found in vitro with primary liver cells, i.e. Kupffer cells (KC) and liver sinusoidal endothelial cells (LSEC) from wild-type C57BL/6J mice. Thus, they represent a suitable alternative to hydrodynamic injection treatments for future vaccination concepts.

STATEMENT OF SIGNIFICANCE

The selective activation of the immune system is a concurrent problem in the treatment of persistent diseases like viral infections (e.g. hepatitis). For the delivery of the toll-like receptor ligand poly(I:C), an immunostimulatory action has been discovered earlier by hydrodynamic injection. However, this technique is not clinically transferable to human patients. We have developed a modular system where poly(I:C) was incorporated into calcium phosphate nanoparticles. The uptake into relevant liver cells was studied both in vitro and in vivo. After intravenous injection into mice, the in vivo uptake was especially prominent in lung and liver, 1 and 3h after the injection. The corresponding strong immune reaction proves their high potential to turn up the immune system, e.g. against viral infections, without adverse side reactions.

A novel immunization approach for dengue infection based on conserved T cell epitopes formulated in calcium phosphate nanoparticles

Dengue virus (DV) is the etiologic agent of dengue fever, the most significant mosquito-borne viral disease in humans. Most DV vaccine approaches are focused on generating antibody mediated responses; one such DV vaccine is approved for use in humans but its efficacy is limited. While it is clear that T cell responses play important role in DV infection and subsequent disease manifestations, fewer studies are aimed at developing vaccines that induce robust T cells responses. Potent T cell based vaccines require 2 critical components: the identification of specific T cell stimulating MHC associated peptides, and an optimized vaccine delivery vehicle capable of simultaneously delivering the antigens and any required adjuvants. We have previously identified and characterized DV specific HLA-A2 and -A24 binding DV serotypes conserved epitopes, and the feasibility of an epitope based vaccine for DV infection. In this study, we build on those previous studies and describe an investigational DV vaccine using T cell epitopes incorporated into a calcium phosphate nanoparticle (CaPNP) delivery system. This study presents a comprehensive analysis of functional immunogenicity of DV CaPNP/multipeptide formulations in vitro and in vivo and demonstrates the CaPNP/multipeptide vaccine is capable of inducing T cell responses against all 4 serotypes of DV. This synthetic vaccine is also cost effective, straightforward to manufacture, and stable at room temperature in a lyophilized form. This formulation may serve as an effective candidate DV vaccine that protects against all 4 serotypes as either a prophylactic or therapeutic vaccine.

Consensus M2e peptide conjugated to gold nanoparticles confers protection against H1N1, H3N2 and H5N1 influenza A viruses

The extracellular domain of influenza A ion channel membrane matrix protein 2 (M2e) is considered to be a potential candidate to develop a universal influenza A vaccine. However poor immunogenicity of M2e presents a significant roadblock. We have developed a vaccine formulation comprising of the consensus M2e peptide conjugated to gold nanoparticles (AuNPs) with CpG as a soluble adjuvant (AuNP-M2e + sCpG). We demonstrate that intranasal delivery of AuNP-M2e + sCpG in mice induces lung B cell activation and robust serum anti-M2e immunoglobulin G (IgG) response, with stimulation of both IgG1 and IgG2a subtypes. Using Madin-Darby canine kidney (MDCK) cells infected with A/California/04/2009 (H1N1pdm) pandemic strain, or A/Victoria/3/75 (H3N2), or the highly pathogenic avian influenza virus A/Vietnam/1203/2004 (H5N1) as immunosorbants we further show that the antibodies generated are also capable of binding to the homotetrameric form of M2 expressed on infected cells. Lethal challenge of vaccinated mice with A/California/04/2009 (H1N1pdm) pandemic strain, A/Victoria/3/75 (H3N2), and the highly pathogenic avian influenza virus A/Vietnam/1203/2004 (H5N1) led to 100%, 92%, and 100% protection, respectively. Overall, this study helps to lay the foundation of a potential universal influenza A vaccine.

Nasal Vaccine Delivery

The mucosal surfaces represent the major site of entry of many pathogens, and major challenges in vaccine development include safety and stability in a suitable dosage form. Micro- and nanocarrier-based delivery systems as nasal vaccines induce humoral, cellular, and mucosal immunity. The nasal route of vaccination could also offer immunity at several distant mucosal sites (oral, rectal, vaginal, and pulmonary), which is considered a simplified and cost-effective mode of vaccination with enhanced patient compliance. Most of the nasal vaccine delivery systems in the form of microparticulates, nanoparticulates, and liposomes are currently under development and prove to offer immunity in animal models. The importance and potential of the nasal route of administration for vaccines is unexplored, and this chapter outlines the opportunities, challenges, and potential delivery solutions to facilitate the development of improved nasal vaccines for infectious diseases.

In vitro toxicity assessment of oral nanocarriers

The fascinating properties of nanomaterials opened new frontiers in medicine. Nanocarriers are useful systems in transporting drugs to site-specific targets. The unique physico-chemical characteristics making nanocarriers promising devices to treat diseases may also be responsible for potential adverse effects. In order to develop functional nano-based drug delivery systems, efficacy and safety should be carefully evaluated. To date, no common testing strategy to address nanomaterial toxicological challenges has been generated. Different cell culture models are currently used to evaluate nanocarrier safety using conventional in vitro assays, but overall they have generated a huge amount of conflicting data. In this review we describe state-of-the-art approaches for in vitro testing of orally administered nanocarriers, highlighting the importance of developing harmonized and validated standard operating procedures. These procedures should be applied in a safe-by-design context with the aim to reduce and/or eliminate the uncertainties and risks associated with nanomedicine development.

Biomaterials-Based Vaccination Strategies for the Induction of CD8+T Cell Responses

Natural and synthetic biomaterials are increasingly being used for the development of vaccines and immunotherapies as alternatives to traditional live-attenuated formulations due to their improved safety profiles and no risk of reversion to virulence. Polymeric materials in particular enjoy attention due to the ease of fabrication, control over physicochemical properties, and their wide range of immunogenicity. While the majority of studies focus on inducing protective antibody responses, in recent years, materials-based strategies for the delivery of antigens and immunomodulators to improve CD8⁺T cell immunity against infectious and non-infectious diseases have gained momentum. Notably, platforms based on polymeric nanoparticles, liposomes, micelles, virus-like particles, self-assembling peptides and peptidomimetics, and multilayer thin films show considerable promise in preclinical studies. In this Review, we first introduce the concepts of CD8⁺T cell activation, effector and memory functions, and cytotoxic activity, followed by vaccine design for eliciting robust and protective long-lived CD8⁺T cell immunity. We then discuss different materials-based vaccines developed in the past decade to elicit CD8⁺T cell responses based on molecular composition or fabrication methods and conclude with a summary and glimpse at the future trends in this area.

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.

Systemic and Mucosal Antibody Responses to Soluble and Nanoparticle-Conjugated Antigens Administered Intranasally

Nanoparticles (NPs) are increasingly being used for drug delivery, as well as antigen carriers and immunostimulants for the purpose of developing vaccines. In this work, we examined how intranasal (i.n.) priming followed by i.n. or subcutaneous (s.c.) boosting immunization affects the humoral immune response to chicken ovalbumin (Ova) and Ova conjugated to 20 nm NPs (NP-Ova). We show that i.n. priming with 20 mg of soluble Ova, a dose known to trigger oral tolerance when administered via gastric gavage, induced substantial systemic IgG1 and IgG2c, as well as mucosal antibodies. These responses were further boosted following a s.c. immunization with Ova and complete Freund’s adjuvant (Ova+CFA). In contrast, 100 µg of Ova delivered via NPs induced an IgG1-dominated systemic response, and primed the intestinal mucosa for secretion of IgA. Following a secondary s.c. or i.n. immunization with Ova+CFA or NP-Ova, systemic IgG1 titers significantly increased, and serum IgG2c and intestinal antibodies were induced in mice primed nasally with NP-Ova. Only Ova- and NP-Ova-primed mice that were s.c.-boosted exhibited substantial systemic and mucosal titers for up to 6 months after priming, whereas the antibodies of i.n.-boosted mice declined over time. Our results indicate that although the amount of Ova delivered by NPs was 1000-fold less than Ova delivered in soluble form, the antigen-specific antibody responses, both systemic and mucosal, are essentially identical by 6 months following the initial priming immunization. Additionally, both i.n.- and s.c.-boosting strategies for NP-Ova-primed mice were capable of inducing a polarized Th1/Th2 immune response, as well as intestinal antibodies; however, it is only by using a heterogeneous prime-boost strategy that long-lasting antibody responses were initiated. These results provide valuable insight for future mucosal vaccine development, as well as furthering our understanding of mucosal antibody responses.

Nanoparticle-based B-cell targeting vaccines: Tailoring of humoral immune responses by functionalization with different TLR-ligands

Induction of an appropriate type of humoral immune response during vaccination is essential for protection against viral and bacterial infections. We recently observed that biodegradable calcium phosphate (CaP) nanoparticles coated with proteins efficiently targeted and activated naïve antigen-specific B-cells in vitro. We now compared different administration routes for CaP-nanoparticles and demonstrated that intramuscular immunization with such CaP-nanoparticles induced stronger immune responses than immunization with monovalent antigen. Additional functionalization of the CaP-nanoparticles with TRL-ligands allowed modulating the IgG subtype response and the level of mucosal IgA antibodies. CpG-containing CaP-nanoparticles were as immunogenic as a virus-like particle vaccine. Functionalization of CaP-nanoparticles with T-helper cell epitopes or CpG also allowed overcoming lack of T-cell help. Thus, our results indicate that CaP-nanoparticle-based B-cell targeting vaccines functionalized with TLR-ligands can serve as a versatile platform for efficient induction and modulation of humoral immune responses in vivo.

Role of metal and metal oxide nanoparticles as diagnostic and therapeutic tools for highly prevalent viral infections

Nanotechnology is increasingly playing important roles in various fields including virology. The emerging use of metal or metal oxide nanoparticles in virus targeting formulations shows the promise of improved diagnostic or therapeutic ability of the agents while uniquely enhancing the prospects of targeted drug delivery. Although a number of nanoparticles varying in composition, size, shape, and surface properties have been approved for human use, the candidates being tested or approved for clinical diagnosis and treatment of viral infections are relatively less in number. Challenges remain in this domain due to a lack of essential knowledge regarding the in vivo comportment of nanoparticles during viral infections. This review provides a broad overview of recent advances in diagnostic, prophylactic and therapeutic applications of metal and metal oxide nanoparticles in human immunodeficiency virus, hepatitis virus, influenza virus and herpes virus infections. Types of nanoparticles commonly used and their broad applications have been explained in this review.

The administration route is decisive for the ability of the vaccine adjuvant CAF09 to induce antigen-specific CD8(+) T-cell responses: The immunological consequences of the biodistribution profile

A prerequisite for vaccine-mediated induction of CD8⁺ T-cell responses is the targeting of dendritic cell (DC) subsets specifically capable of cross-presenting antigen epitopes to CD8⁺ T cells. Administration of a number of cationic adjuvants via the intraperitoneal (i.p.) route has been shown to result in strong CD8⁺ T-cell responses, whereas immunization via e.g. the intramuscular (i.m.) or subcutaneous (s.c.) routes often stimulate weak CD8⁺ T-cell responses. The hypothesis for this is that self-drainage of the adjuvant/antigen to the lymphoid organs, which takes place upon i.p. immunization, is required for the subsequent activation of cross-presenting lymphoid organ-resident CD8α⁺ DCs. In contrast, s.c. or i.m. immunization usually results in the formation of a depot at the site of injection (SOI), which hinders the self-drainage and targeting of the vaccine to cross-presenting CD8α⁺ DCs. We investigated this hypothesis by correlating the biodistribution pattern and the adjuvanticity of the strong CD8⁺ T-cell inducing liposomal cationic adjuvant formulation 09 (CAF09), which is composed of dimethyldioctadecylammonium bromide/monomycoloyl glycerol liposomes with polyinosinic:polycytidylic acid electrostatically adsorbed to the surface. Biodistribution studies with radiolabeled CAF09 and a surface-adsorbed model antigen [ovalbumin (OVA)] showed that a significantly larger fraction of the vaccine dose localized in the draining lymph nodes (dLNs) and the spleen 6 h after i.p. immunization, as compared to after i.m. immunization. Studies with fluorescently labelled OVA + CAF09 demonstrated a preferential association of OVA + CAF09 to DCs/monocytes, as compared to macrophages and B cells, following i.p. immunization. Administration of OVA + CAF09 via the i.p. route did also result in DC activation, whereas no DC activation could be measured within the same period with unadjuvanted OVA and OVA + CAF09 administered via the s.c. or i.m. routes. In the dLNs, the highest level of activated, cross-presenting CD8α⁺ DCs was detected at 24 h post immunization, whereas an influx of activated, migrating and cross-presenting CD103⁺ DCs to the dLNs could be measured after 48 h. This suggests that the CD8α⁺ DCs are activated by self-draining OVA + CAF09 in the lymphoid organs, whereas the CD103⁺ DCs are stimulated by the OVA + CAF09 at the SOI. These results support the hypothesis that the self-drainage of OVA + CAF09 to the draining LNs is required for the activation of CD8α⁺ DCs, while the migratory CD103⁺ DCs may play a role in sustaining the subsequent induction of strong CD8⁺ T-cell responses.

Biomineralized vaccine nanohybrid for needle-free intranasal immunization

Frequent outbreaks and the rapid global spread of infectious diseases have increased the urgent need for massive vaccination especially in countries with limited resources. Intranasal vaccination facilitates the mass vaccination via needle-free delivery of vaccine through nasal mucosal surfaces. Inspired by the strong capability of calcium phosphate (CaP) materials to adhere to cells and tissues, we propose to improve nasal vaccination by using a biomineralization-based strategy. The vaccine nanohybrid was obtained by covering the viral surface with CaP nanoshell, which changed the physiochemical properties of original vaccine, resulting in the increase of mucosal adhesion to the nasal tissues. The core-shell structure was beneficial for the receptor-independent uptake and the induction of elevated local IgA response within the nasal cavity. Moreover, the vaccine complex elicited enhanced systemic antibody response that neutralized wild type of dengue virus and promoted the systemic cellular immune responses. This achievement presents the potential of CaP based vaccine biomineralization for the fabrication of needle-free vaccine formulation.

Toward RNA nanoparticle vaccines: synergizing RNA and inorganic nanoparticles to achieve immunopotentiation

Traditionally, vaccines have been composed of live attenuated or killed microorganisms. Alternatively, individual protein subunits or other molecular components of the microorganism can serve as the antigen and trigger an antibody response by the immune system. The immune system is a coordinated molecular and cellular response that works in concert to check the spread of infection. In the past decade, there has been much progress on DNA vaccines. DNA vaccination includes using the coding segments of a viral or bacterial genome to generate an immune response. However, the potential advantage of combining an RNA molecule with inorganic nanoparticle delivery should be considered, with the goal to achieve immuno-synergy between the two and to overcome some of the current limitations of DNA vaccines and traditional vaccines. WIREs Nanomed Nanobiotechnol 2017, 9:e1415. doi: 10.1002/wnan.1415 For further resources related to this article, please visit the WIREs website.

Combination of nanoparticle-based therapeutic vaccination and transient ablation of regulatory T cells enhances anti-viral immunity during chronic retroviral infection

Background

Regulatory T cells (Tregs) have been shown to limit anti-viral immunity during chronic retroviral infection and to restrict vaccine-induced T cell responses. The objective of the study was to assess whether a combinational therapy of nanoparticle-based therapeutic vaccination and concomitant transient ablation of Tregs augments anti-viral immunity and improves virus control in chronically retrovirus-infected mice. Therefore, chronically Friend retrovirus (FV)-infected mice were immunized with calcium phosphate (CaP) nanoparticles functionalized with TLR9 ligand CpG and CD8⁺ or CD4⁺ T cell epitope peptides (GagL_85–93 or Env gp70_123–141) of FV. In addition, Tregs were ablated during the immunization process. Reactivation of CD4⁺ and CD8⁺ effector T cells was analysed and the viral loads were determined.

Results

Therapeutic vaccination of chronically FV-infected mice with functionalized CaP nanoparticles transiently reactivated cytotoxic CD8⁺ T cells and significantly reduced the viral loads. Transient ablation of Tregs during nanoparticle-based therapeutic vaccination strongly enhanced anti-viral immunity and further decreased viral burden.

Conclusion

Our data illustrate a crucial role for CD4⁺ Foxp3⁺ Tregs in the suppression of anti-viral T cell responses during therapeutic vaccination against chronic retroviral infection. Thus, the combination of transient Treg ablation and therapeutic nanoparticle-based vaccination confers robust and sustained anti-viral immunity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-016-0258-9) contains supplementary material, which is available to authorized users.

Vaccine Engineering with Dual-Functional Mineral Shell: A Promising Strategy to Overcome Preexisting Immunity

Dual-functional biomineral-vaccine core-shell nanohybrids are obtained using recombinant adenovirus serotype 5 (rAd5) as templates, which efficiently masks the neutralizing epitope of vaccines and preserve their original immunogenicity. The versatile vaccine hybrid can evade the preexisting anti-Ad5 immunity, leading to boosted multifunctional antigen-specific cytokine-secreting T cell responses and presenting promising applications of vaccine-material hybrid for the rational design of vaccines.

Human-applicable dendrigraft poly-l-lysine-based nanoparticle-coated Plasmodium yoelii-transamidase DNA vaccine is immunogenic and protective as the polyethylenimine-based formulation

The objective was to assess the immunoequivalence and protective efficacy of the novel, relatively safe dendrigraft poly-l-lysine-based nanoparticle formulation in comparison to the non-degradable polyethylenimine-based system. Groups of 6-week-old female C57BL/6 mice were immunized three times biweekly. Each mouse received 100 µg of the Plasmodium yoelii GPI8p-transamidase PyTAM formulated with nanoball that consisted of PyTAM/PEI/γ-PGA or PyTAM/DGL/γ-PGA and their respective nanoparticle-coated blank vector controls. Two weeks after the last immunization, the humoral responses and cellular immune response were assessed. The survival and parasitemia were evaluated in each group challenged intraperitoneally with 106 of a lethal strain of P. yoelii 17XL-parasitized red blood cells. Mice immunized with PyTAM/PEI/γ-PGA or PyTAM/DGL/γ-PGA showed similar survival rates, humoral responses and T helper 1 pro-inflammatory cellular immune responses in vivo and ex vivo. In particular, the PyTAM/DGL/γ-PGA formulation showed a significant increase in conventional dendritic cells in the spleen, which were consistently associated with high interleukin-12 production, the driver of the T helper 1 response. We show that the substitution of non-degradable polyethylenimine with the biodegradable dendrigraft poly-l-lysine in the nanoparticle formulation is immunoequivalent and elicits protective immunity against the lethal strain of P. yoelii. Therefore, this new gene-delivery vehicle with a good safety profile presents an exciting prospect for application in vaccination strategies.