Effective induction of anti-melanoma immunity following genetic vaccination with synthetic mRNA coding for the fusion protein EGFP.TRP2

Cationic cycloamylose based nucleic acid nanocarriers

Nucleic acid delivery by viral and non-viral methods has been a cornerstone for the contemporary gene therapy aimed at correcting the defective genes, replacing of the missing genes, or downregulating the expression of anomalous genes is highly desirable for the management of various diseases. Ostensibly, it becomes paramount for the delivery vectors to intersect the biological barriers for accessing their destined site within the cellular environment. However, the lipophilic nature of biological membranes and their potential to limit the entry of large sized, charged, hydrophilic molecules thus presenting a sizeable challenge for the cellular integration of negatively charged nucleic acids. Furthermore, the susceptibility of nucleic acids towards the degrading enzymes (nucleases) in the lysosomes present in cytoplasm is another matter of concern for their cellular and nuclear delivery. Hence, there is a pressing need for the identification and development of cationic delivery systems which encapsulate the cargo nucleic acids where the charge facilitates their cellular entry by evading the membrane barriers, and the encapsulation shields them from the enzymatic attack in cytoplasm. Cycloamylose bearing a closed loop conformation presents a robust candidature in this regard owing to its remarkable encapsulating tendency towards nucleic acids including siRNA, CpG DNA, and siRNA. The presence of numerous hydroxyl groups on the cycloamylose periphery provides sites for its chemical modification for the introduction of cationic groups, including spermine, (3-Chloro-2 hydroxypropyl) trimethylammonium chloride (Q188), and diethyl aminoethane (DEAE). The resulting cationic cycloamylose possesses a remarkable transfection efficiency and provides stability to cargo oligonucleotides against endonucleases, in addition to modulating the undesirable side effects such as unwanted immune stimulation. Cycloamylose is known to interact with the cell membranes where they release certain membrane components such as phospholipids and cholesterol thereby resulting in membrane destabilization and permeabilization. Furthermore, cycloamylose derivatives also serve as formulation excipients for improving the efficiency of other gene delivery systems. This review delves into the various vector and non-vector-based gene delivery systems, their advantages, and limitations, eventually leading to the identification of cycloamylose as an ideal candidate for nucleic acid delivery. The synthesis of cationic cycloamylose is briefly discussed in each section followed by its application for specific delivery/transfection of a particular nucleic acid.

Recent Findings on Therapeutic Cancer Vaccines: An Updated Review

Cancer remains one of the global leading causes of death and various vaccines have been developed over the years against it, including cell-based, nucleic acid-based, and viral-based cancer vaccines. Although many vaccines have been effective in in vivo and clinical studies and some have been FDA-approved, there are major limitations to overcome: (1) developing one universal vaccine for a specific cancer is difficult, as tumors with different antigens are different for different individuals, (2) the tumor antigens may be similar to the body's own antigens, and (3) there is the possibility of cancer recurrence. Therefore, developing personalized cancer vaccines with the ability to distinguish between the tumor and the body's antigens is indispensable. This paper provides a comprehensive review of different types of cancer vaccines and highlights important factors necessary for developing efficient cancer vaccines. Moreover, the application of other technologies in cancer therapy is discussed. Finally, several insights and conclusions are presented, such as the possibility of using cold plasma and cancer stem cells in developing future cancer vaccines, to tackle the major limitations in the cancer vaccine developmental process.

COVID-19: Clinical status of vaccine development to date

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-induced COVID-19 is a complicated disease. Clinicians are continuously facing difficulties to treat infected patients using the principle of repurposing of drugs as no specific drugs are available to treat COVID-19. To minimize the severity and mortality, global vaccination is the only hope as a potential preventive measure. After a year-long global research and clinical struggle, 165 vaccine candidates have been developed and some are currently still in the pipeline. A total of 28 candidate vaccines have been approved for use and the remainder are in different phases of clinical trials. In this comprehensive report, the authors aim to demonstrate, classify and provide up-to-date clinical trial status of all the vaccines discovered to date and specifically focus on the approved candidates. Finally, the authors specifically focused on the vaccination of different types of medically distinct populations.

Recent Advances in the Molecular Design and Delivery Technology of mRNA for Vaccination Against Infectious Diseases

Vaccines can prevent many millions of illnesses against infectious diseases and save numerous lives every year. However, traditional vaccines such as inactivated viral and live attenuated vaccines cannot adapt to emerging pandemics due to their time-consuming development. With the global outbreak of the COVID-19 epidemic, the virus continues to evolve and mutate, producing mutants with enhanced transmissibility and virulence; the rapid development of vaccines against such emerging global pandemics becomes more and more critical. In recent years, mRNA vaccines have been of significant interest in combating emerging infectious diseases due to their rapid development and large-scale production advantages. However, their development still suffers from many hurdles such as their safety, cellular delivery, uptake, and response to their manufacturing, logistics, and storage. More efforts are still required to optimize the molecular designs of mRNA molecules with increased protein expression and enhanced structural stability. In addition, a variety of delivery systems are also needed to achieve effective delivery of vaccines. In this review, we highlight the advances in mRNA vaccines against various infectious diseases and discuss the molecular design principles and delivery systems of associated mRNA vaccines. The current state of the clinical application of mRNA vaccine pipelines against various infectious diseases and the challenge, safety, and protective effect of associated vaccines are also discussed.

Advanced Biomaterials for Cell-Specific Modulation and Restore of Cancer Immunotherapy

The past decade has witnessed the explosive development of cancer immunotherapies. Nevertheless, low immunogenicity, limited specificity, poor delivery efficiency, and off-target side effects remain to be the major limitations for broad implementation of cancer immunotherapies to patient bedside. Encouragingly, advanced biomaterials offering cell-specific modulation of immunological cues bring new solutions for improving the therapeutic efficacy while relieving side effect risks. In this review, focus is given on how functional biomaterials can enable cell-specific modulation of cancer immunotherapy within the cancer-immune cycle, with particular emphasis on antigen-presenting cells (APCs), T cells, and tumor microenvironment (TME)-resident cells. By reviewing the current progress in biomaterial-based cancer immunotherapy, here the aim is to provide a better understanding of biomaterials' role in targeting modulation of antitumor immunity step-by-step and guidelines for rationally developing targeting biomaterials for more personalized cancer immunotherapy. Moreover, the current challenge and future perspective regarding the potential application and clinical translation will also be discussed.

Anti-COVID-19 Nanomaterials: Directions to Improve Prevention, Diagnosis, and Treatment

Following the announcement of the outbreak of COVID-19 by the World Health Organization, unprecedented efforts were made by researchers around the world to combat the disease. So far, various methods have been developed to combat this "virus" nano enemy, in close collaboration with the clinical and scientific communities. Nanotechnology based on modifiable engineering materials and useful physicochemical properties has demonstrated several methods in the fight against SARS-CoV-2. Here, based on what has been clarified so far from the life cycle of SARS-CoV-2, through an interdisciplinary perspective based on computational science, engineering, pharmacology, medicine, biology, and virology, the role of nano-tools in the trio of prevention, diagnosis, and treatment is highlighted. The special properties of different nanomaterials have led to their widespread use in the development of personal protective equipment, anti-viral nano-coats, and disinfectants in the fight against SARS-CoV-2 out-body. The development of nano-based vaccines acts as a strong shield in-body. In addition, fast detection with high efficiency of SARS-CoV-2 by nanomaterial-based point-of-care devices is another nanotechnology capability. Finally, nanotechnology can play an effective role as an agents carrier, such as agents for blocking angiotensin-converting enzyme 2 (ACE2) receptors, gene editing agents, and therapeutic agents. As a general conclusion, it can be said that nanoparticles can be widely used in disinfection applications outside in vivo. However, in in vivo applications, although it has provided promising results, it still needs to be evaluated for possible unintended immunotoxicity. Reviews like these can be important documents for future unwanted pandemics.

Messenger RNA-Based Vaccines Against Infectious Diseases

In vitro-transcribed, messenger RNA-based infectious disease vaccines have the potential to successfully address many of the weaknesses of traditional vaccine platforms, such as the lack of potency and/or durability of vaccine protection, time-consuming, and expensive manufacturing, and, in some cases, safety issues. This optimism is fueled by a great deal of impressive recent data demonstrating that mRNA vaccines have many of the attributes that are necessary for a viable new vaccine class for human use. This review briefly describes mRNA vaccine types, discusses the most relevant and recent publications on infectious disease mRNA vaccines, and highlights the hurdles that need to be overcome to bring this promising novel vaccine modality to the clinic.

The Current Status of COVID-19 Vaccines

The current COVID-19 pandemic has substantially accelerated the demands for efficient vaccines. A wide spectrum of approaches includes live attenuated and inactivated viruses, protein subunits and peptides, viral vector-based delivery, DNA plasmids, and synthetic mRNA. Preclinical studies have demonstrated robust immune responses, reduced viral loads and protection against challenges with SARS-CoV-2 in rodents and primates. Vaccine candidates based on all delivery systems mentioned above have been subjected to clinical trials in healthy volunteers. Phase I clinical trials have demonstrated in preliminary findings good safety and tolerability. Evaluation of immune responses in a small number of individuals has demonstrated similar or superior levels of neutralizing antibodies in comparison to immunogenicity detected in COVID-19 patients. Both adenovirus- and mRNA-based vaccines have entered phase II and study protocols for phase III trials with 30,000 participants have been finalized.

A Guide to Nucleic Acid Vaccines in the Prevention and Treatment of Infectious Diseases and Cancers: From Basic Principles to Current Applications

Faced with the challenges posed by infectious diseases and cancer, nucleic acid vaccines present excellent prospects in clinical applications. Compared with traditional vaccines, nucleic acid vaccines have the characteristics of high efficiency and low cost. Therefore, nucleic acid vaccines have potential advantages in disease prevention and treatment. However, the low immunogenicity and instability of nucleic acid vaccines have limited their development. Therefore, a large number of studies have been conducted to improve their immunogenicity and stability by improving delivery methods, thereby supporting progress and development for clinical applications. This article mainly reviews the advantages, disadvantages, mechanisms, delivery methods, and clinical applications of nucleic acid vaccines.

Vaccination with Messenger RNA: A Promising Alternative to DNA Vaccination

The first proof-of-concept studies about the feasibility of genetic vaccines were published over three decades ago, opening the way for future development. The idea of nonviral antigen delivery had multiple advantages over the traditional live or inactivated pathogen-based vaccines, but a great deal of effort had to be invested to turn the idea of genetic vaccination into reality. Although early proof-of-concept studies were groundbreaking, they also showed that numerous aspects of genetic vaccines needed to be improved. Until the early 2000s, the vast majority of effort was invested into the development of DNA vaccines due to the potential issues of instability and low in vivo translatability of messenger RNA (mRNA). In recent years, numerous studies have demonstrated the outstanding abilities of mRNA to elicit potent immune responses against infectious pathogens and different types of cancer, making it a viable platform for vaccine development. Multiple mRNA vaccine platforms have been developed and evaluated in small and large animals and humans and the results seem to be promising. RNA-based vaccines have important advantages over other vaccine approaches including outstanding efficacy, safety, and the potential for rapid, inexpensive, and scalable production. There is a substantial investment by new mRNA companies into the development of mRNA therapeutics, particularly vaccines, increasing the number of basic and translational research publications and human clinical trials underway. This review gives a broad overview about genetic vaccines and mainly focuses on the past and present of mRNA vaccines along with the future directions to bring this potent vaccine platform closer to therapeutic use.

Adjuvant-pulsed mRNA vaccine nanoparticle for immunoprophylactic and therapeutic tumor suppression in mice

Synthetic mRNA represents an exciting cancer vaccine technology for the implementation of effective cancer immunotherapy. However, inefficient in vivo mRNA delivery along with a requirement for immune co-stimulation present major hurdles to achieving anti-tumor therapeutic efficacy. Here, we demonstrate a proof-of-concept adjuvant-pulsed mRNA vaccine nanoparticle (NP) that is composed of an ovalbumin-coded mRNA and a palmitic acid-modified TLR7/8 agonist R848 (C16-R848), coated with a lipid-polyethylene glycol (lipid-PEG) shell. This mRNA vaccine NP formulation retained the adjuvant activity of encapsulated C16-R848 and markedly improved the transfection efficacy of the mRNA (>95%) and subsequent MHC class I presentation of OVA mRNA derived antigen in antigen-presenting cells. The C16-R848 adjuvant-pulsed mRNA vaccine NP approach induced an effective adaptive immune response by significantly improving the expansion of OVA-specific CD8+ T cells and infiltration of these cells into the tumor bed in vivo, relative to the mRNA vaccine NP without adjuvant. The approach led to an effective anti-tumor immunity against OVA expressing syngeneic allograft mouse models of lymphoma and prostate cancer, resulting in a significant prevention of tumor growth when the vaccine was given before tumor engraftment (84% reduction vs. control) and suppression of tumor growth when given post engraftment (60% reduction vs. control). Our findings indicate that C16-R848 adjuvant pulsation to mRNA vaccine NP is a rational design strategy to increase the effectiveness of synthetic mRNA vaccines for cancer immunotherapy.

mRNA Vaccine Era-Mechanisms, Drug Platform and Clinical Prospection

Messenger ribonucleic acid (mRNA)-based drugs, notably mRNA vaccines, have been widely proven as a promising treatment strategy in immune therapeutics. The extraordinary advantages associated with mRNA vaccines, including their high efficacy, a relatively low severity of side effects, and low attainment costs, have enabled them to become prevalent in pre-clinical and clinical trials against various infectious diseases and cancers. Recent technological advancements have alleviated some issues that hinder mRNA vaccine development, such as low efficiency that exist in both gene translation and in vivo deliveries. mRNA immunogenicity can also be greatly adjusted as a result of upgraded technologies. In this review, we have summarized details regarding the optimization of mRNA vaccines, and the underlying biological mechanisms of this form of vaccines. Applications of mRNA vaccines in some infectious diseases and cancers are introduced. It also includes our prospections for mRNA vaccine applications in diseases caused by bacterial pathogens, such as tuberculosis. At the same time, some suggestions for future mRNA vaccine development about storage methods, safety concerns, and personalized vaccine synthesis can be found in the context.

Recent developments of RNA-based vaccines in cancer immunotherapy

INTRODUCTION

Cancer immunotherapy is more dependent on monoclonal antibodies, proteins, and cells, as therapeutic agents, to attain prominent outcomes. However, cancer immunotherapy's clinical benefits need to be enhanced, as many patients still do not respond well to existing treatments, or their diseases may relapse after temporary control. RNA-based approaches have provided new options for advancing cancer immunotherapy. Moreover, considerable efforts have been made to utilize RNA for vaccine production. RNA vaccines, which encode tumor-associated or specific epitopes, stimulate adaptive immunity. This adaptive immune response is capable of elimination or reduction of tumor burden. It is crucial to develop effective RNA transfer technologies that penetrate the lipid bilayer to reach the cytoplasm for translation into functional proteins. Two important delivery methods include the loading of mRNA into dendritic cells ex vivo; and direct injection of naked RNA with or without a carrier.

AREAS COVERED

The latest results of pre-clinical and clinical studies with RNA vaccines in cancer immunotherapy are summarized in this review.

EXPERT OPINION

RNA vaccines are now in early clinical development with promising safety and efficacy outcomes. Also, the translation capacity and durability of these vaccines can be increased with chemical modifications and sequence engineering.

Nanotechnology for COVID-19: Therapeutics and Vaccine Research

The current global health threat by the novel coronavirus disease 2019 (COVID-19) requires an urgent deployment of advanced therapeutic options available. The role of nanotechnology is highly relevant to counter this "virus" nano enemy. Nano intervention is discussed in terms of designing effective nanocarriers to counter the conventional limitations of antiviral and biological therapeutics. This strategy directs the safe and effective delivery of available therapeutic options using engineered nanocarriers, blocking the initial interactions of viral spike glycoprotein with host cell surface receptors, and disruption of virion construction. Controlling and eliminating the spread and reoccurrence of this pandemic demands a safe and effective vaccine strategy. Nanocarriers have potential to design risk-free and effective immunization strategies for severe acute respiratory syndrome coronavirus 2 vaccine candidates such as protein constructs and nucleic acids. We discuss recent as well as ongoing nanotechnology-based therapeutic and prophylactic strategies to fight against this pandemic, outlining the key areas for nanoscientists to step in.

Breakthrough concepts in immune-oncology: Cancer vaccines at the bedside

Clinical approval of the immune checkpoint blockade (ICB) agents for multiple cancer types has reinvigorated the long-standing work on cancer vaccines. In the pre-ICB era, clinical efforts focused on the Ag, the adjuvants, the formulation, and the mode of delivery. These translational efforts on therapeutic vaccines range from cell-based (e.g., dendritic cells vaccine Sipuleucel-T) to DNA/RNA-based platforms with various formulations (liposome), vectors (Listeria monocytogenes), or modes of delivery (intratumoral, gene gun, etc.). Despite promising preclinical results, cancer vaccine trials without ICB have historically shown little clinical activity. With the anticipation and expansion of combinatorial immunotherapeutic trials with ICB, the cancer vaccine field has entered the personalized medicine arena with recent advances in immunogenic neoantigen-based vaccines. In this article, we review the literature to organize the different cancer vaccines in the clinical space, and we will discuss their advantages, limits, and recent progress to overcome their challenges. Furthermore, we will also discuss recent preclinical advances and clinical strategies to combine vaccines with checkpoint blockade to improve therapeutic outcome and present a translational perspective on future directions.

Synthesis and Evaluation of a Thermoresponsive Degradable Chitosan-Grafted PNIPAAm Hydrogel as a "Smart" Gene Delivery System

Thermoresponsive hydrogels demonstrate tremendous potential as sustained drug delivery systems. However, progress has been limited as formulation of a stable biodegradable thermosensitive hydrogel remains a significant challenge. In this study, free radical polymerization was exploited to formulate a biodegradable thermosensitive hydrogel characterized by sustained drug release. Highly deacetylated chitosan and N-isopropylacrylamide with distinctive physical properties were employed to achieve a stable, hydrogel network at body temperature. The percentage of chitosan was altered within the copolymer formulations and the subsequent physical properties were characterized using ¹H-NMR, FTIR, and TGA. Viscoelastic, swelling, and degradation properties were also interrogated. The thermoresponsive hydrogels were loaded with RALA/pEGFP-N1 nanoparticles and release was examined. There was sustained release of nanoparticles over three weeks and, more importantly, the nucleic acid cargo remained functional and this was confirmed by successful transfection of the NCTC-929 fibroblast cell line. This tailored thermoresponsive hydrogel offers an option for sustained delivery of macromolecules over a prolonged considerable period.

Nucleic Acid Immunotherapeutics for Cancer

The past decade has witnessed the blossom of two fields: nucleic acid therapeutics and cancer immunotherapy. Unlike traditional small molecule medicines or protein biologics, nucleic acid therapeutics have characteristic features such as storing genetic information, immunomodulation, and easy conformational recovery. Immunotherapy uses the patients' own immune system to treat cancer. A variety of strategies have been developed for cancer immunotherapy including immune checkpoint blockade, adoptive cell transfer therapy, therapeutic vaccines, and oncolytic virotherapy. Interestingly, nucleic acid therapeutics have emerged as a pivotal class of regimen for cancer immunotherapy. Examples of such nucleic acid immunotherapeutics include immunostimulatory DNA/RNA, mRNA/plasmids that can be translated into immunotherapeutic proteins/peptides, and genome-editing nucleic acids. Like many other therapeutic nucleic acids, nucleic acid immunotherapeutics often require chemical modifications to protect them from enzymatic degradation and need drug delivery systems for optimal delivery to target tissues and cells and subcellular locations. In this review, we attempted to summarize recent advancement in the interfacial field of nucleic acid immunotherapeutics for cancer treatment.

Strong Immune Responses Induced by Direct Local Injections of Modified mRNA-Lipid Nanocomplexes

In vitro transcribed mRNAs hold the promises of many medical applications in disease prevention and treatment, such as replacement or supplement of missing or inadequately expressed endogenous proteins and as preventive vaccines against infectious diseases, therapeutic vaccines, or other protein-based biopharmaceutics for cancer therapy. A safe and efficient delivery system for mRNA is crucial to the success of mRNA therapeutic applications. In this study, we report that InstantFECT, a liposome-based transfection reagent, can pack pseudouridine-incorporated mRNA into nanocomplexes that are highly efficient in mediating in vivo transfection in multiple organs after local delivery. High levels of expression of EGFP and luciferase reporters after intratumoral and intramuscular injections were observed, which lasted for up to 96 hrs. Immunogenicity of antigens encoded by mRNA delivered with nanocomplex was investigated by subcutaneous delivery of modified mRNAs encoding Staphylococcus aureus adenosine synthase A (AdsA) and a model tumor-associated antigen ovalbumin (OVA). Strong T cell responses were provoked by both mRNAs delivered. Therapeutic and protective treatment with the OVA mRNA-liposome nanocomplex significantly inhibited B16-OVA tumor progression and increased mouse survival. There was no sign of obvious toxicity related to the treatment both in tissue culture and in mice. An intravenous injection of the same dosage of the modified mRNA-lipid nanocomplex showed minimal transfection in major organs, indicating an excellent safety feature as the gene transfer occurred only at the injection sites, whereas intravenous (i.v.) injection with the same amount of mRNA complexed with a commercial transfection reagent Trans-IT showed luciferase expression in the spleen. In summary, InstantFECT cationic liposomes provide a safe and efficient in vivo locoregional delivery of mRNA and could be a useful tool for basic research and for the development of mRNA-based therapies.

Transcutaneous delivery of DNA/mRNA for cancer therapeutic vaccination

Therapeutic vaccination is a promising strategy for the immunotherapy of cancers. It eradicates cancer cells by evoking and strengthening the patient's own immune system. Because of the easy access and sophisticated immune networks, the skin becomes an ideal target organ for vaccination. Genetic vaccines have been widely investigated, with the advantages of the delivery of multiple antigens and a lower cost for production compared to protein/peptide vaccines. This review summarizes the advances made with respect to the transcutaneous delivery of DNA/mRNA for cancer therapeutic vaccination and also gives a brief description of the immunological milieu of the skin and the importance of dendritic cell-targeting in vaccine delivery, as well as the technologies that aim to facilitate antigen delivery and modulate antigen-presenting cells, thus improving cellular responses. The applications of genetic vaccines encoding tumor antigens delivered through the skin route, both in preclinical and clinical trials, are outlined.

Biomedical applications of mRNA nanomedicine

As an attractive alternative to plasmid DNA, messenger RNA (mRNA) has recently emerged as a promising class of nucleic acid therapeutics for biomedical applications. Advances in addressing the inherent shortcomings of mRNA and in the development of nanoparticle-based delivery systems have prompted the development and clinical translation of mRNA-based medicines. In this review, we discuss the chemical modification strategies of mRNA to improve its stability, minimize immune responses, and enhance translational efficacy. We also highlight recent progress in nanoparticle-based mRNA delivery. Considerable attention is given to the increasingly widespread applications of mRNA nanomedicine in the biomedical fields of vaccination, protein-replacement therapy, gene editing, and cellular reprogramming and engineering.

New Vaccine Technologies to Combat Outbreak Situations

Ever since the development of the first vaccine more than 200 years ago, vaccinations have greatly decreased the burden of infectious diseases worldwide, famously leading to the eradication of small pox and allowing the restriction of diseases such as polio, tetanus, diphtheria, and measles. A multitude of research efforts focuses on the improvement of established and the discovery of new vaccines such as the HPV (human papilloma virus) vaccine in 2006. However, radical changes in the density, age distribution and traveling habits of the population worldwide as well as the changing climate favor the emergence of old and new pathogens that bear the risk of becoming pandemic threats. In recent years, the rapid spread of severe infections such as HIV, SARS, Ebola, and Zika have highlighted the dire need for global preparedness for pandemics, which necessitates the extremely rapid development and comprehensive distribution of vaccines against potentially previously unknown pathogens. What is more, the emergence of antibiotic resistant bacteria calls for new approaches to prevent infections. Given these changes, established methods for the identification of new vaccine candidates are no longer sufficient to ensure global protection. Hence, new vaccine technologies able to achieve rapid development as well as large scale production are of pivotal importance. This review will discuss viral vector and nucleic acid-based vaccines (DNA and mRNA vaccines) as new approaches that might be able to tackle these challenges to global health.

Latest development on RNA-based drugs and vaccines

Drugs and vaccines based on mRNA and RNA viruses show great potential and direct translation in the cytoplasm eliminates chromosomal integration. Limitations are associated with delivery and stability issues related to RNA degradation. Clinical trials on RNA-based drugs have been conducted in various disease areas. Likewise, RNA-based vaccines for viral infections and various cancers have been subjected to preclinical and clinical studies. RNA delivery and stability improvements include RNA structure modifications, targeting dendritic cells and employing self-amplifying RNA. Single-stranded RNA viruses possess self-amplifying RNA, which can provide extreme RNA replication in the cytoplasm to support RNA-based drug and vaccine development. Although oligonucleotide-based approaches have demonstrated potential, the focus here is on mRNA- and RNA virus-based methods.

Drug development has suffered from inefficiency, side effects and high costs. For this reason novel approaches for drug discovery are of great importance. RNA-based methods provide the advantage of targeting ‘production’ of drugs to diseased cells and vaccines to immune response-stimulating cells. RNA drugs have demonstrated therapeutic efficacy in eye and heart diseases and in various cancers in clinical trials. Likewise, RNA-based vaccines have provided protection against challenges with lethal doses of viruses such as Ebola and cancer cells in animal models.

Comparison of the Expression Kinetics and Immunostimulatory Activity of Replicating mRNA, Nonreplicating mRNA, and pDNA after Intradermal Electroporation in Pigs

Synthetic mRNA is becoming increasingly popular as an alternative to pDNA-based gene therapy. Currently, multiple synthetic mRNA platforms have been developed. In this study we investigated the expression kinetics and the changes in mRNA encoding cytokine and chemokine levels following intradermal electroporation in pigs of pDNA, self-replicating mRNA, and modified and unmodified mRNA. The self-replicating mRNA tended to induce the highest protein expression, followed by pDNA, modified mRNA, and unmodified mRNA. Interestingly, the self-replicating mRNA was able to maintain its high expression levels during at least 12 days. In contrast, the expression of pDNA and the nonreplicating mRNAs dropped after respectively one and two days. Six days after intradermal electroporation a dose-dependent expression was observed for all vectors. Again, also at lower doses, the self-replicating mRNA tended to show the highest expression. All the mRNA vectors, including the modified mRNA, induced elevated levels of mRNA encoding cytokines and chemokines in the porcine skin after intradermal electroporation, while no such response was noticed after intradermal electroporation of the pDNA vector.

mRNA vaccines - a new era in vaccinology

mRNA vaccines represent a promising alternative to conventional vaccine approaches because of their high potency, capacity for rapid development and potential for low-cost manufacture and safe administration. However, their application has until recently been restricted by the instability and inefficient in vivo delivery of mRNA. Recent technological advances have now largely overcome these issues, and multiple mRNA vaccine platforms against infectious diseases and several types of cancer have demonstrated encouraging results in both animal models and humans. This Review provides a detailed overview of mRNA vaccines and considers future directions and challenges in advancing this promising vaccine platform to widespread therapeutic use.

Natural and artificial small RNAs: a promising avenue of nucleic acid therapeutics for cancer

Since the failure of traditional therapy, gene therapy using functional DNA sequence and small RNA/DNA molecules (oligonucleotide) has become a promising avenue for cancer treatment. The discovery of RNA molecules has impelled researchers to investigate small regulatory RNA from various natural and artificial sources and determine a cogent target for controlling tumor progression. Small regulatory RNAs are used for therapeutic silencing of oncogenes and aberrant DNA repair response genes. Despite their advantages, therapies based on small RNAs exhibit limitations in terms of stability of therapeutic drugs, precision-based delivery in tissues, precision-based intercellular and intracellular targeting, and tumor heterogeneity-based responses. In this study, we summarize the potential and drawbacks of small RNAs in nucleic acid therapeutics for cancer.

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.

The messenger's great message for vaccination

Poly ribonucleic acid (RNA) is the only polymer capable to recapitulate all processes of life: containment of genetic information, enzymatic activities and capacity to create defined 3D structures. Since it has a remarkable chemical stability (at neutral or acidic pH) and can be modified to enhance/reduce particular features (e.g., stability in biological RNase containing milieus or recognition by immune sensors), it is a particularly versatile and ideal active pharmaceutical ingredient. However, the utilization of RNA as a gene vehicle (messenger RNA, mRNA) for therapy has only recently been exploited. Within this scope, mRNA-based vaccines designed to trigger anti-cancer, anti-virus or anti-allergy immune responses have been developed. Modifications of mRNA vectors and implementation of adequate formulations have allowed to turn this natural superlative biological molecule into a safe active pharmaceutical ingredient that can virtually address any medical need including vaccination or immunotherapy. This is the newest great message delivered by this messenger.

RNA-Based Vaccines in Cancer Immunotherapy

RNA vaccines traditionally consist of messenger RNA synthesized by in vitro transcription using a bacteriophage RNA polymerase and template DNA that encodes the antigen(s) of interest. Once administered and internalized by host cells, the mRNA transcripts are translated directly in the cytoplasm and then the resulting antigens are presented to antigen presenting cells to stimulate an immune response. Alternatively, dendritic cells can be loaded with either tumor associated antigen mRNA or total tumor RNA and delivered to the host to elicit a specific immune response. In this review, we will explain why RNA vaccines represent an attractive platform for cancer immunotherapy, discuss modifications to RNA structure that have been developed to optimize mRNA vaccine stability and translational efficiency, and describe strategies for nonviral delivery of mRNA vaccines, highlighting key preclinical and clinical data related to cancer immunotherapy.

Induction of HIV-1 gag specific immune responses by cationic micelles mediated delivery of gag mRNA

In recent years, mRNA-based vaccines have emerged to be a great alternative to DNA-based vaccines due to the safety of not inserting into host genome. However, mRNA molecules are single-stranded nucleic acids that are vulnerable under RNase existing in human skin and tissues. In this study, a self-assembled cationic nanomicelles based on polyethyleneimine-stearic acid (PSA) copolymer were developed to delivery HIV-1 gag encoding mRNA to dendritic cells and BALB/c mice. We evaluated the transfection efficiency and cell uptake efficiency of naked EGFP mRNA, PSA, PEI-2k and PEI-25k nanoparticles format on DC2.4 cell lines. Immune responses after sub-cutaneous administration of gag mRNA to BALB/c mice were notably induced by PSA as compared with naked gag mRNA. We found the PSA/mRNA nanomicelles were potent systems that can effectively deliver mRNA and induce antigen-specific immune response, stimulating various new vaccine strategies using mRNA.

Bridging infectious disease vaccines with cancer immunotherapy: a role for targeted RNA based immunotherapeutics

Tumor-specific immunotherapy holds the promise of eradicating malignant tumors with exquisite precision without additional toxicity to standard treatments. Cancer immunotherapy has conventionally relied on cell-mediated immunity while successful infectious disease vaccines have been shown to induce humoral immunity. Efficacious cancer immunotherapeutics likely require both cellular and humoral responses, and RNA based cancer vaccines are especially suited to stimulate both arms of the immune system. RNA is inherently immunogenic, inducing innate immune responses to initiate cellular and humoral adaptive immunity, but has limited utility based on its poor in vivo stability. Early work utilized ‘naked’ RNA vaccines, whereas more recent efforts have attempted to encapsulate RNA thereby protecting it from degradation. However, feasibility has been limited by a lack of defined and safe targeting mechanisms for the in vivo delivery of stabilized RNA. As new cancer antigens come to the forefront with novel RNA encapsulation and targeting techniques, RNA vaccines may prove to be a vital, safe and robust method to initiate patient-specific anti-tumor efficacy.

Intranasal mRNA nanoparticle vaccination induces prophylactic and therapeutic anti-tumor immunity

Direct in vivo administration of messenger RNA (mRNA) delivered in both naked and nanoparticle formats are actively investigated because the use of dendritic cells transfected ex vivo with mRNA for cancer therapy is expensive and needs significant infrastructure. Notably, intravenous and subcutaneous injections are the only routes of administration tested for mRNA nanoparticle tumor vaccination. In this report, we demonstrate that tumor immunity can be achieved via nasal administration of mRNA. Mice nasally immunized with mRNA delivered in nanoparticle format demonstrate delayed tumor progression in both prophylactic and therapeutic immunization models. The observed tumor immunity correlates with splenic antigen-specific CD8+ T cells and is achieved only when mRNA is delivered in nanoparticle but not in naked format. In conclusion, we demonstrate, as a proof-of-concept, a non-invasive approach to mRNA tumor vaccination, increasing its potential as a broadly applicable and off-the-shelf therapy for cancer treatment.

Development of nucleic acid vaccines: use of self-amplifying RNA in lipid nanoparticles

Self-amplifying RNA or RNA replicon is a form of nucleic acid-based vaccine derived from either positive-strand or negative-strand RNA viruses. The gene sequences encoding structural proteins in these RNA viruses are replaced by mRNA encoding antigens of interest as well as by RNA polymerase for replication and transcription. This kind of vaccine has been successfully assayed with many different antigens as vaccines candidates, and has been shown to be potent in several animal species, including mice, nonhuman primates, and humans. A key challenge to realizing the broad potential of self-amplifying vaccines is the need for safe and effective delivery methods. Ideally, an RNA nanocarrier should provide protection from blood nucleases and extended blood circulation, which ultimately would increase the possibility of reaching the target tissue. The delivery system must then be internalized by the target cell and, upon receptor-mediated endocytosis, must be able to escape from the endosomal compartment into the cell cytoplasm, where the RNA machinery is located, while avoiding degradation by lysosomal enzymes. Further, delivery systems for systemic administration ought to be well tolerated upon administration. They should be safe, enabling the multiadministration treatment modalities required for improved clinical outcomes and, from a developmental point of view, production of large batches with reproducible specifications is also desirable. In this review, the concept of self-amplifying RNA vaccines and the most promising lipid-based delivery systems are discussed.

Nucleic acid vaccines: prospects for non-viral delivery of mRNA vaccines

INTRODUCTION

Nucleic acid-based vaccines are being developed as a means to combine the positive attributes of both live-attenuated and subunit vaccines. Viral vectors and plasmid DNA vaccines have been extensively evaluated in human clinical trials and have been shown to be safe and immunogenic, although none have been licensed for human use. More recently, mRNA-based vaccine alternatives have emerged and might offer certain advantages over their DNA-based counterparts.

AREAS COVERED

This review describes the two main categories of mRNA vaccines: conventional non-amplifying and self-amplifying mRNA. It summarizes the initial clinical proof-of-concept studies and outlines the preclinical testing of the next wave of innovations for the technology. Finally, this review highlights the versatile functionality of the mRNA molecule and introduces opportunities for future improvements in vaccine design.

EXPERT OPINION

The prospects for mRNA vaccines are very promising. Like other types of nucleic acid vaccines, mRNA vaccines have the potential to combine the positive attributes of live attenuated vaccines while obviating many potential safety limitations. Although data from initial clinical trials appear encouraging, mRNA vaccines are far from a commercial product. These initial approaches have spurred innovations in vector design, non-viral delivery, large-scale production and purification of mRNA to quickly move the technology forward. Some improvements have already been tested in preclinical models for both prophylactic and therapeutic vaccine targets and have demonstrated their ability to elicit potent and broad immune responses, including functional antibodies, type 1 T helper cells-type T cell responses and cytotoxic T cells. Though the initial barriers for this nucleic acid vaccine approach seem to be overcome, in our opinion, the future and continued success of this approach lies in a more extensive evaluation of the many non-viral delivery systems described in the literature and gaining a better understanding of the mechanism of action to allow rational design of next generation technologies.

Antigen-specific mRNA transfection of autologous dendritic cells

Several reports have described the use of tumor-extracted RNA as source of tumor antigen for the preparation of vaccines based on dendritic cells (DC) and its potential use for antigen-specific or polyvalent tumor vaccination. Upon transfection, RNA is transcribed into proteins that enter the cytoplasmic degradation pathway and can be presented by DC through class I major histocompatibility complex (MHC)-I, thus inducing specific T cell cytotoxic responses. In this chapter, we present a protocol to transfect murine dendritic cells with tumor mRNA by means of electroporation.

RNA vaccines for anti-tumor therapy

The immune system is able to recognize tumor antigens and this has been the basis for the development of cancer immunotherapies. The immune system can be instructed to recognize and attack tumor cells by means of vaccination strategies. One such strategy involves the delivery of tumor antigen as genetic material. Herewith we describe the use of RNA encoding tumor antigens for vaccination purposes in tumor settings. RNA has features that are interesting for vaccination. Upon transfection, the RNA has no possibility of integration into the genome, and the tumor translated proteins enter the intrinsic antigen processing pathway thus enabling presentation by MHC-I molecules. This can specifically activate cytotoxic CD8 T cells that can attack and kill tumor cells. RNA can be delivered as a naked molecule for vaccination purposes or can be used to transfect dendritic cells. The combination of RNA technology with dendritic cell vaccination provides a powerful tool for cancer immunotherapies.

Mannosylated and histidylated LPR technology for vaccination with tumor antigen mRNA

mRNA-based vaccines are currently being developed for treating various diseases including cancers. For this purpose, synthetic or in vitro transcribed (IVT) mRNA encoding tumor antigen offers several advantages over plasmid DNA encoding tumor antigen including better delivery and security. In this chapter, we report the preparation of mannosylated mRNA nanoparticles termed mannosylated lipopolyplexes or Man-LPR loaded with mRNA encoding a melanoma antigen. This formulation enhances the transfection of dendritic cells (DCs) in vivo and the anti-B16F10 melanoma vaccination in mice. The mRNA is formulated with histidylated liposomes and a histidylated polymer. Those pH-sensitive vectors promote membrane destabilization in endosomes upon the protonation of their histidine groups, allowing nucleic acid delivery in the cytosol. To favor DCs targeting via the mannose receptor, a mannose lipid is incorporated in the liposomes. Here, we provide protocols for the preparation of mannosylated liposomes, the synthesis of mRNA, mice immunization based on systemic injection, measurement of the cellular immune response and determination of the number of transfected splenic DC.

Synthetic vehicles for DNA vaccination

DNA vaccination is an attractive immunization method able to induce robust cellular immune responses in pre-clinical models. However, clinical DNA vaccination trials performed thus far have resulted in marginal responses. Consequently, strategies are currently under development to improve the efficacy of DNA vaccines. A promising strategy is the use of synthetic particle formulations as carrier systems for DNA vaccines. This review discusses commonly used synthetic carriers for DNA vaccination and provides an overview of in vivo studies that use this strategy. Future recommendations on particle characteristics, target cell types and evaluation models are suggested for the potential improvement of current and novel particle delivery systems. Finally, hurdles which need to be tackled for clinical evaluation of these systems are discussed.

Intranasal vaccination with messenger RNA as a new approach in gene therapy: use against tuberculosis

BACKGROUND

mRNAs are highly versatile, non-toxic molecules that are easy to produce and store, which can allow transient protein expression in all cell types. The safety aspects of mRNA-based treatments in gene therapy make this molecule one of the most promising active components of therapeutic or prophylactic methods. The use of mRNA as strategy for the stimulation of the immune system has been used mainly in current strategies for the cancer treatment but until now no one tested this molecule as vaccine for infectious disease.

RESULTS

We produce messenger RNA of Hsp65 protein from Mycobacterium leprae and show that vaccination of mice with a single dose of 10 μg of naked mRNA-Hsp65 through intranasal route was able to induce protection against subsequent challenge with virulent strain of Mycobacterium tuberculosis. Moreover it was shown that this immunization was associated with specific production of IL-10 and TNF-alpha in spleen. In order to determine if antigen presenting cells (APCs) present in the lung are capable of capture the mRNA, labeled mRNA-Hsp65 was administered by intranasal route and lung APCs were analyzed by flow cytometry. These experiments showed that after 30 minutes until 8 hours the populations of CD11c+, CD11b+ and CD19+ cells were able to capture the mRNA. We also demonstrated in vitro that mRNA-Hsp65 leads nitric oxide (NO) production through Toll-like receptor 7 (TLR7).

CONCLUSIONS

Taken together, our results showed a novel and efficient strategy to control experimental tuberculosis, besides opening novel perspectives for the use of mRNA in vaccines against infectious diseases and clarifying the mechanisms involved in the disease protection we noticed as well.

Immunotherapy can reject intracranial tumor cells without damaging the brain despite sharing the target antigen

Although vaccines targeting tissue differentiation Ags represent a promising strategy for cancer immunotherapy, the risk of triggering autoimmune damage to normal tissues remains to be determined. Immunizing against a melanoma-associated Ag, dopachrome tautomerase (DCT), which normal melanocytes and glial cells also express, allowed concurrent analysis of autoimmune consequences in multiple tissues. We show that vaccination with recombinant adenovirus expressing DCT elicited a strong CTL response in C57BL/6 mice, leading to protection against intracranial challenge with B16-F10 melanoma cells. Both histological analysis and behavioral testing indicated that there was no evidence of neuropathology in vaccinated animals and long-term survivors. Although vitiligo or demyelination could be induced by additional stimuli (i.e., surgery or inflammation) in DCT-vaccinated mice, it did not extend beyond the inflammatory area, suggesting that there is self-regulatory negative feedback in normal tissues. These results demonstrate that it is possible to vaccinate against a tumor embedded in a vital organ that shares the target Ag.

Optimization of intradermal vaccination by DNA tattooing in human skin

The intradermal administration of DNA vaccines by tattooing is a promising delivery technique for genetic immunization, with proven high immunogenicity in mice and in nonhuman primates. However, the parameters that result in optimal expression of DNA vaccines that are applied by this strategy to human skin are currently unknown. To address this issue we set up an ex vivo human skin model in which DNA vaccine-induced expression of reporter proteins could be monitored longitudinally. Using this model we demonstrate the following: First, the vast majority of cells that express DNA vaccine-encoded antigen in human skin are formed by epidermal keratinocytes, with only a small fraction (about 1%) of antigen-positive epidermal Langerhans cells. Second, using full randomization of DNA tattoo variables we show that an increase in DNA concentration,needle depth, and tattoo time all significantly increase antigen expression ( p < 0.001), with DNA concentration forming the most critical variable influencing the level of antigen expression. Finally, in spite of the marked immunogenicity of this vaccination method in animal models, transfection efficiency of the technique is shown to be extremely low, estimated at approximately 2 to 2000 out of 1 x 10(10) copies of plasmid applied. This finding, coupled with the observed dependency of antigen expression on DNA concentration, suggests that the development of strategies that can enhance in vivo transfection efficacy would be highly valuable. Collectively, this study shows that an ex vivo human skin model can be used to determine the factors that control vaccine-induced antigen expression and define the optimal parameters for the evaluation of DNA tattoo or other dermal delivery techniques in phase 1 clinical trials.

Optimization of intradermal vaccination by DNA tattooing in human skin

The intradermal administration of DNA vaccines by tattooing is a promising delivery technique for genetic immunization, with proven high immunogenicity in mice and in nonhuman primates. However, the parameters that result in optimal expression of DNA vaccines that are applied by this strategy to human skin are currently unknown. To address this issue we set up an ex vivo human skin model in which DNA vaccine-induced expression of reporter proteins could be monitored longitudinally. Using this model we demonstrate the following: First, the vast majority of cells that express DNA vaccine-encoded antigen in human skin are formed by epidermal keratinocytes, with only a small fraction (about 1%) of antigen-positive epidermal Langerhans cells. Second, using full randomization of DNA tattoo variables we show that an increase in DNA concentration,needle depth, and tattoo time all significantly increase antigen expression ( p < 0.001), with DNA concentration forming the most critical variable influencing the level of antigen expression. Finally, in spite of the marked immunogenicity of this vaccination method in animal models, transfection efficiency of the technique is shown to be extremely low, estimated at approximately 2 to 2000 out of 1 x 10(10) copies of plasmid applied. This finding, coupled with the observed dependency of antigen expression on DNA concentration, suggests that the development of strategies that can enhance in vivo transfection efficacy would be highly valuable. Collectively, this study shows that an ex vivo human skin model can be used to determine the factors that control vaccine-induced antigen expression and define the optimal parameters for the evaluation of DNA tattoo or other dermal delivery techniques in phase 1 clinical trials.

Lack of functionally active Melan-A(26-35)-specific T cells in the blood of HLA-A2+ vitiligo patients

Vitiligo, a skin disorder characterized by the spontaneous destruction of melanocytes, is believed to be of autoimmune origin. We investigated the presence and functionality of CD8(+) T-cells specific for the melanocyte-associated antigens Melan-A, gp100, tyrosinase, and TRP-2 in the blood of HLA-A2(+) vitiligo patients. We enumerated antigen-specific CD8(+) T cells by major histocompatibility complex multimer staining directly ex vivo, as well as after 9 days of in vitro stimulation and assessed IFN-gamma secretion by enzyme-linked immunospot (Elispot) assay. Tyrosinase-, gp100-, or TRP-2-specific CD8(+) T cells could not be identified in the peripheral blood of individuals with vitiligo. Although Melan-A-specific T cells were detectable at levels comparable to Flu-MP-specific T cells by multimer staining, these lymphocytes did not express the skin-homing receptor cutaneous lymphocyte antigen, were phenotypically naïve (CD45RA(+)), and were unresponsive in the IFN-gamma Elispot assay, suggesting that they are unlikely to be involved in the etiopathogenesis of vitiligo.

Vaccination with messenger RNA (mRNA)

Both DNA and mRNA can be used as vehicles for gene therapy. Because the immune system is naturally activated by foreign nucleic acids thanks to the presence of Toll-like Receptors (TLR) in endosomes (TLR3, 7, and 8 detect exogenous RNA, while TLR9 can detect exogenous DNA), the delivery of foreign nucleic acids usually induces an immune response directed against the encoded protein. Many preclinical and clinical studies were performed using DNA-based experimental vaccines. However, no such products are yet approved for the human population. Meanwhile, the naturally transient and cytosolically active mRNA molecules are seen as a possibly safer and more potent alternative to DNA for gene vaccination. Optimized mRNA (improved for codon usage, stability, antigen-processing characteristics of the encoded protein, etc.) were demonstrated to be potent gene vaccination vehicles when delivered naked, in liposomes, coated on particles or transfected in dendritic cells in vitro. Human clinical trials indicate that the delivery of mRNA naked or transfected in dendritic cells induces the expected antigen-specific immune response. Follow-up efficacy studies are on the way. Meanwhile, mRNA can be produced in large amounts and GMP quality, allowing the further development of mRNA-based therapies. This chapter describes the structure of mRNA, its possible optimizations for immunization purposes, the different methods of delivery used in preclinical studies, and finally the results of clinical trial where mRNA is the active pharmaceutical ingredient of new innovative vaccines.

Elevated frequencies of self-reactive CD8+ T cells following immunization with a xenoantigen are due to the presence of a heteroclitic CD4+ T-cell helper epitope

Immunization of mice with human dopachrome tautomerase (hDCT) provides greater protection against melanoma than immunization with the murine homologue (mDCT). We mapped the CD8(+) and CD4(+) T-cell epitopes in both proteins to better understand the mechanisms of the enhanced protection. The dominant CD8(+) T-cell epitopes were fully conserved between both proteins, yet immunization with hDCT produced frequencies of CD8(+) T cells that were 5- to 10-fold higher than immunization with mDCT. This difference was not intrinsic to the two proteins because comparable frequencies of CD8(+) T cells were elicited by both antigens in DCT-deficient mice. Strikingly, only hDCT elicited a significant level of specific CD4(+) T cells in wild-type (WT) mice. The murine protein was not devoid of CD4(+) T-cell epitopes because immunization of DCT-deficient mice with mDCT resulted in robust CD4(+) T-cell immunity directed against two epitopes that were not identified in WT mice. These results suggested that the reduced immunogenicity of mDCT in WT mice may be a function of insufficient CD4(+) T-cell help. To address this possibility, the dominant CD4(+) T-cell epitope from hDCT was introduced into mDCT. Immunization with the mutated mDCT evoked CD8(+) T-cell frequencies and protective immunity comparable with hDCT. These results reveal a novel mechanism by which xenoantigens overcome tolerance. Our data also suggest that immunologic tolerance is more stringent for CD4(+) T cells than CD8(+) T cells, providing a mechanism of peripheral tolerance where autoreactive CD8(+) T cells fail to be activated due to a lack of autoreactive CD4(+) T cells specific for the same antigen.

mRNA-based cancer vaccine: prevention of B16 melanoma progression and metastasis by systemic injection of MART1 mRNA histidylated lipopolyplexes

Immunization with mRNA encoding tumor antigen is an emerging vaccine strategy for cancer. In this paper, we demonstrate that mice receiving systemic injections of MART1 mRNA histidylated lipopolyplexes were specifically and significantly protected against B16F10 melanoma tumor progression. The originality of this work concerns the use of a new tumor antigen mRNA formulation as vaccine, which allows an efficient protection against the growth of a highly aggressive tumor model after its delivery by intravenous route. Synthetic melanoma-associated antigen MART1 mRNA was formulated with a polyethylene glycol (PEG)ylated derivative of histidylated polylysine and L-histidine-(N,N-di-n-hexadecylamine)ethylamide liposomes (termed histidylated lipopolyplexes). Lipopolyplexes comprised mRNA/polymer complexes encapsulated by liposomes. The tumor protective effect was induced with MART1 mRNA carrying a poly(A) tail length of 100 adenosines at an optimal dose of 12.5 microg per mouse. MART1 mRNA lipopolyplexes elicited a cellular immune response characterized by the production of interferon-gamma and the induction of cytotoxic T lymphocytes. Finally, the anti-B16 response was enhanced using a formulation containing both MART1 mRNA and MART1-LAMP1 mRNA encoding the antigen targeted to the major histocompatibility complex class II compartments by the lysosomal sorting signal of LAMP1 protein. Our results provide a basis for the development of mRNA histidylated lipopolyplexes for cancer vaccine.

New strategy for the identification of squamous carcinoma antigens that induce therapeutic immune responses in tumor-bearing mice

This study describes a new strategy for the identification of squamous carcinoma antigens tumor-associated antigens (TAA). The antigens were discovered by comparing microarrays of squamous carcinoma vaccines highly enriched for immunotherapeutic cells with non-enriched vaccines. The vaccines were prepared by transferring sheared genomic DNA fragments (25 kb) from KLN205 cells, a squamous carcinoma cell line (DBA/2 mouse origin (H-2(d)) into LM fibroblasts (C3H/He origin, H-2(k)). The transferred tumor DNA segments integrate spontaneously into the genome of the recipient cells, replicate as the cells divide and are expressed. As only a small proportion of the transfected cell population was expected to have incorporated DNA segments that included genes specifying TAA (the vast majority specify normal cellular constituents), a novel strategy was employed to enrich the vaccine for TAA-positive cells. Microarrays were used to compare genes expressed by enriched and non-enriched vaccines. Seventy-five genes were overexpressed in cells from the enriched vaccine. One, the gene for Cytochrome P450 (family 2, subfamily e, polypeptide 1) (Cyp2e1), was overexpressed in the enriched but not the non-enriched vaccine. A vaccine for squamous carcinoma was prepared by transfer of a 357 bp fragment of the gene for Cyp2e1 into the fibroblast cell line. Robust immunity, sufficient to result in indefinite survival, was induced in tumor-bearing mice immunized with cells transfected with this gene fragment.