Vitamin E Scaffolds of pH-Responsive Lipid Nanoparticles as DNA Vaccines in Cancer and Protozoan Infection

Lipid- and Polymer-Based Nanocarrier Platforms for Cancer Vaccine Delivery

Cancer immunotherapy has gained popularity in recent years in the search for effective treatment modalities for various malignancies, particularly those that are resistant to conventional chemo- and radiation therapy. Cancer vaccines target the cancer-immunity cycle by boosting the patient's own immune system to recognize and kill cancer cells, thus serving as both preventative and curative therapeutic tools. Among the different types of cancer vaccines, those based on nanotechnology have shown great promise in advancing the field of cancer immunotherapy. Lipid-based nanoparticles (NPs) have become the most advanced platforms for cancer vaccine delivery, but polymer-based NPs have also received considerable interest. This Review aims to provide an overview of the nanotechnology-enabled cancer vaccine landscape, focusing on recent advances in lipid- and polymer-based nanovaccines and their hybrid structures and discussing the challenges against the clinical translation of these important nanomedicines.

An Ionizable Lipid Material with a Vitamin E Scaffold as an mRNA Vaccine Platform for Efficient Cytotoxic T Cell Responses

RNA vaccines based on lipid nanoparticles (LNPs) with in vitro transcribed mRNA (IVT-mRNA) encapsulated are now a currently successful but still evolving modality of vaccines. One of the advantages of RNA vaccines is their ability to induce CD8+ T-cell-mediated cellular immunity that is indispensable for excluding pathogen-infected cells or cancer cells from the body. In this study, we report on the development of LNPs with an enhanced capability for inducing cellular immunity by using an ionizable lipid with a vitamin E scaffold. An RNA vaccine that contained this ionizable lipid and an IVT-mRNA encoding a model antigen ovalbumin (OVA) induced OVA-specific cytotoxic T cell responses and showed an antitumor effect against an E.G7-OVA tumor model. Vaccination with the LNPs conferred protection against lethal infection by Toxoplasma gondii using its antigen TgPF. The vitamin E scaffold-dependent type I interferon response was important for effector CD8+ T cell differentiation induced by the mRNA-LNPs. Our findings also revealed that conventional dendritic cells (cDCs) were essential for achieving CD8+ T cell responses induced by the mRNA-LNPs, while the XCR1-positive subset of cDCs, cDC1 specialized for antigen cross-presentation, was not required. Consistently, the mRNA-LNPs were found to selectively transfect another subset of cDCs, cDC2 that had migrated from the skin to lymph nodes, where they could make vaccine-antigen-dependent contacts with CD8+ T cells. The findings indicate that the activation of innate immune signaling by the adjuvant activity of the vitamin E scaffold and the expression of antigens in cDC2 are important for subsequent antigen presentation and the establishment of antigen-specific immune responses.

Nanovaccine-based strategies for lymph node targeted delivery and imaging in tumor immunotherapy

Therapeutic tumor vaccines have attracted considerable attention in the past decade; they can induce tumor regression, eradicate minimal residual disease, establish lasting immune memory and avoid non-specific and adverse side effects. However, the challenge in the field of therapeutic tumor vaccines is ensuring the delivery of immune components to the lymph nodes (LNs) to activate immune cells. The clinical response rate of traditional therapeutic tumor vaccines falls short of expectations due to inadequate lymph node delivery. With the rapid development of nanotechnology, a large number of nanoplatform-based LN-targeting nanovaccines have been exploited for optimizing tumor immunotherapies. In addition, some nanovaccines possess non-invasive visualization performance, which is benefit for understanding the kinetics of nanovaccine exposure in LNs. Herein, we present the parameters of nanoplatforms, such as size, surface modification, shape, and deformability, which affect the LN-targeting functions of nanovaccines. The recent advances in nanoplatforms with different components promoting LN-targeting are also summarized. Furthermore, emerging LNs-targeting nanoplatform-mediated imaging strategies to both improve targeting performance and enhance the quality of LN imaging are discussed. Finally, we summarize the prospects and challenges of nanoplatform-based LN-targeting and /or imaging strategies, which optimize the clinical efficacy of nanovaccines in tumor immunotherapies.

Preparation of selective organ-targeting (SORT) lipid nanoparticles (LNPs) using multiple technical methods for tissue-specific mRNA delivery

A new methodology termed selective organ targeting (SORT) was recently developed that enables controllable delivery of nucleic acids to target tissues. SORT lipid nanoparticles (LNPs) involve the inclusion of SORT molecules that accurately tune delivery to the liver, lungs and spleen of mice after intravenous administration. Nanoparticles can be engineered to target specific cells and organs in the body by passive, active and endogenous targeting mechanisms that require distinct design criteria. SORT LNPs are modular and can be prepared using scalable, synthetic chemistry and established engineering formulation methods. This protocol provides detailed procedures, including the synthesis of a representative ionizable cationic lipid, preparation of multiple classes of SORT LNPs by pipette, vortex and microfluidic mixing methods, physical characterization, and in vitro/in vivo mRNA delivery evaluation. Depending on the scale of the experiments, the synthesis of the ionizable lipid requires 4-6 d; LNPs can be formulated within several hours; LNP characterization can be completed in 2-4 h; and in vitro/in vivo evaluation studies require 1-14 d, depending on the design and application. Our strategy offers a versatile and practical method for rationally designing nanoparticles that accurately target specific organs. The SORT LNPs generated as described in this protocol can therefore be applied to multiple classes of LNP systems for therapeutic nucleic acid delivery and facilitate the development of protein replacement and genetic medicines in target tissues. This protocol does not require specific expertise, is modular to various lipids within defined physicochemical classes, and should be accomplishable by researchers from various backgrounds.

Lymph node-targeting nanovaccines for cancer immunotherapy

Cancer immunotherapies such as tumor vaccines, chimeric antigen receptor T cells and immune checkpoint blockades, have attracted tremendous attention. Among them, tumor vaccines prime immune response by delivering antigens and adjuvants to the antigen presenting cells (APCs), thus enhancing antitumor immunotherapy. Despite tumor vaccines have made considerable achievements in tumor immunotherapy, it remains challenging to efficiently deliver tumor vaccines to activate the dendritic cells (DCs) in lymph nodes (LNs). Rational design of nanovaccines on the basis of biomedical nanotechnology has emerged as one of the most promising strategies for boosting the outcomes of cancer immunotherapy. In recent years, great efforts have been made in exploiting various nanocarrier-based LNs-targeting tumor nanovaccines. In view of the rapid advances in this field, we here aim to summarize the latest progression in LNs-targeting nanovaccines for cancer immunotherapy, with special attention to various nano-vehicles developed for LNs-targeting delivery of tumor vaccines, including lipid-based nanoparticles, polymeric nanocarriers, inorganic nanocarriers and biomimetic nanosystems. Moreover, the recent trends in nanovaccines-based combination cancer immunotherapy are provided. Finally, the rationality, advantages and challenges of LNs-targeting nanovaccines for clinical translation and application are spotlighted.

Nanomaterial-Based Drug Delivery System Targeting Lymph Nodes

The lymphatic system plays an indispensable role in humoral balance, lipid metabolism, and immune regulation. The lymph nodes (LNs) are known as the primary sites of tumor metastasis and the metastatic LNs largely affected the prognosis of the patiens. A well-designed lymphatic-targeted system favors disease treatment as well as vaccination efficacy. In recent years, development of nanotechnologies and emerging biomaterials have gained increasing attention in developing lymph-node-targeted drug-delivery systems. By mimicking the endogenous macromolecules or lipid conjugates, lymph-node-targeted nanocarries hold potential for disease diagnosis and tumor therapy. This review gives an introduction to the physiological functions of LNs and the roles of LNs in diseases, followed by a review of typical lymph-node-targeted nanomaterial-based drug-delivery systems (e.g., liposomes, micelles, inorganic nanomaterials, hydrogel, and nanocapsules). Future perspectives and conclusions concerned with lymph-node-targeted drug-delivery systems are also provided.

Recent advances in nanotechnology-based COVID-19 vaccines and therapeutic antibodies

COVID-19 has caused a global pandemic and millions of deaths. It is imperative to develop effective countermeasures against the causative viral agent, SARS-CoV-2 and its many variants. Vaccines and therapeutic antibodies are the most effective approaches for preventing and treating COVID-19, respectively. SARS-CoV-2 enters host cells through the activities of the virus-surface spike (S) protein. Accordingly, the S protein is a prime target for vaccines and therapeutic antibodies. Dealing with particles with dimensions on the scale of nanometers, nanotechnology has emerged as a critical tool for rapidly designing and developing safe, effective, and urgently needed vaccines and therapeutics to control the COVID-19 pandemic. For example, nanotechnology was key to the fast-track approval of two mRNA vaccines for their wide use in human populations. In this review article, we first explore the roles of nanotechnology in battling COVID-19, including protein nanoparticles (for presentation of protein vaccines), lipid nanoparticles (for formulation with mRNAs), and nanobodies (as unique therapeutic antibodies). We then summarize the currently available COVID-19 vaccines and therapeutics based on nanotechnology.

Toxoplasma gondii GRA15 DNA Vaccine with a Liposomal Nanocarrier Composed of an SS-Cleavable and pH-Activated Lipid-like Material Induces Protective Immunity against Toxoplasmosis in Mice

Toxoplasma gondii affects the health of humans and livestock and causes severe illness in the fetus and immunocompromised individuals. Because of the high incidence and severe consequences of T. gondii infection, a safe and suitable vaccine is needed. We found that lipid nanoparticles (LNPs) consisting of a series of functional materials prepared with vitamin E, such as SS-cleavable and pH-activated lipid-like materials (ssPalmE), were a safe and efficient way to develop next-generation DNA vaccines. In this study, we prepared ssPalmE-LNP to encapsulate pCpG-free-T. gondii dense granule protein 15 DNA (ssPalmE-LNP_TgGRA15). Following a challenge infection with avirulent PLK strain of T. gondii, the mice immunized with ssPalmE-LNP_TgGRA15 had a significantly higher survival rate and lower clinical scores compared with unimmunized and ssPalmE-LNP_non-coding-immunized mice. Immunization of mice with the ssPalmE-LNP_TgGRA15 led to a significantly higher production of specific IgG1 and IG2c antibodies compared with unimmunized and ssPalmE-LNP_non-coding-immunized mice, while there was no statistically significant difference in the concentration of serum interferon-gamma at the acute stage of the infection. These findings indicate that ssPalmE-LNP is an effective cargo for the transportation of DNA vaccines for protozoan infections. To explore the mechanism of protective immunity induced by ssPalmE-LNP_TgGRA15, further immunological study is needed in the future.

Development of an SS-Cleavable pH-Activated Lipid-Like Material (ssPalm) as a Nucleic Acid Delivery Device

Gene and nucleic acid-based medication is an ultimate strategy in the field of personalized medicine. A gene or short interference RNA (siRNA) molecule needs to be delivered to the appropriate organelle (i.e., nucleus and cytoplasm, respectively). We recently focused on improving the intrinsic activity of my original material (ssPalm) in terms of endosomal/lysosomal membrane destabilization activity by chemically modifying the tertiary amine structure. In parallel, I have been expanding the range of applications of ssPalms. The first application is a DNA or RNA vaccine. My crucial finding is that the vitamin E-scaffold ssPalm (ssPalmE) is highly immune-stimulative when combined with DNA. Thereafter, I redesigned the hydrophobic scaffold structure, and found that an oleic acid-scaffold ssPalm (ssPalmO) can confer anti-inflammatory characteristics. Based on this result, I further upgraded the ssPalmO, by inserting a newly designed linker with self-degradable properties.

Oxidative Stress as a Possible Target in the Treatment of Toxoplasmosis: Perspectives and Ambiguities

Toxoplasma gondii is an apicomplexan parasite causing toxoplasmosis, a common disease, which is most typically asymptomatic. However, toxoplasmosis can be severe and even fatal in immunocompromised patients and fetuses. Available treatment options are limited, so there is a strong impetus to develop novel therapeutics. This review focuses on the role of oxidative stress in the pathophysiology and treatment of T. gondii infection. Chemical compounds that modify redox status can reduce the parasite viability and thus be potential anti-Toxoplasma drugs. On the other hand, oxidative stress caused by the activation of the inflammatory response may have some deleterious consequences in host cells. In this respect, the potential use of natural antioxidants is worth considering, including melatonin and some vitamins, as possible novel anti-Toxoplasma therapeutics. Results of in vitro and animal studies are promising. However, supplementation with some antioxidants was found to promote the increase in parasitemia, and the disease was then characterized by a milder course. Undoubtedly, research in this area may have a significant impact on the future prospects of toxoplasmosis therapy.

Advances in Toxoplasma gondii Vaccines: Current Strategies and Challenges for Vaccine Development

Toxoplasmosis, caused by the apicomplexan parasite Toxoplasma gondii, is one of the most damaging parasite-borne zoonotic diseases of global importance. While approximately one-third of the entire world’s population is estimated to be infected with T. gondii, an effective vaccine for human use remains unavailable. Global efforts in pursuit of developing a T. gondii vaccine have been ongoing for decades, and novel innovative approaches have been introduced to aid this process. A wide array of vaccination strategies have been conducted to date including, but not limited to, nucleic acids, protein subunits, attenuated vaccines, and nanoparticles, which have been assessed in rodents with promising results. Yet, translation of these in vivo results into clinical studies remains a major obstacle that needs to be overcome. In this review, we will aim to summarize the current advances in T. gondii vaccine strategies and address the challenges hindering vaccine development.

Dawn of lipid nanoparticles in lymph node targeting: Potential in cancer immunotherapy

It is generally known that the lymph nodes (LNs) are important tissues in cancer immunotherapy. Therefore, delivering immune functional compounds to LNs is a useful strategy for enhancing cancer immunotherapy. Lipid-based nanocarriers have been widely used as delivery systems that target LNs, but lipid nanoparticle (LNP) technology has recently attracted increased interest. High levels of nucleic acids can be efficiently loaded in LNPs, they can be used to actively deliver nucleic acids into the cytoplasm, and they can be produced on an industrial scale. The use of microfluidic devices has been particularly valuable for producing small-sized LNPs, thus paving the way for successful LN targeting. In the review, we focus on the potential of LNP technology for targeting LNs.