Establishment of an Antiplasmodial Vaccine Based on PfRH5-Encoding RNA Replicons Stabilized by Cationic Liposomes

A universal viral capsid protein based one step RNA synthesis and packaging system for rapid and efficient mRNA vaccine development

The success of coronavirus disease 2019 mRNA vaccines highlights the transformative potential of mRNA technology. Current mRNA vaccine development involves complex steps, including plasmid construction, RNA transcription, 5' capping, poly(A) tailing, and lipid nanoparticle encapsulation, yet challenges in vaccine accessibility persist. Here, we present an innovative mRNA platform leveraging the self-assembly capabilities of the MS2 bacteriophage viral capsid protein (VCP). A dual-promoter plasmid has been designed where one promoter drives VCP expression while the other transcribes target RNA containing pac sites, enabling rapid mRNA self-assembly in Escherichia coli. Using an ovalbumin (OVA)-based tumor model, we validate the efficacy of this system. Tumor growth is significantly inhibited, accompanied by robust immune activation. Flow cytometry analyses reveal increased frequencies of OVA-specific CD8+, as well as activated and memory T cells. Additionally, the MS2-OVA vaccine favorably modulated the tumor immunosuppressive microenvironment by reducing myeloid-derived suppressor cells, while sustained antibody responses demonstrated the platform's ability to induce durable humoral immunity. These findings establish the feasibility of one-step mRNA synthesis and packaging in E. coli, providing a versatile and rapid platform for mRNA vaccine development, with broad implications for addressing global vaccination challenges.

Brief Comparison of the Efficacy of Cationic and Anionic Liposomes as Nonviral Delivery Systems

In recent decades, the development and application of nonviral vectors, such as liposomes and lipidic nanoparticles, for gene therapy and drug delivery have seen substantial progress. The interest in the physicochemical properties and structures of the complexes liposome/DNA and liposome/RNA is due to their potential to substitute viruses as carriers of drugs or genetic material into cells with minimal cytotoxicity, which could lead to their use in gene therapy. Initially, cationic liposomes were utilized as nonviral DNA delivery vectors; subsequently, different molecules, such as polymers, were incorporated to enhance transfection efficiency. Additionally, liposome/protein complexes have been developed as nonviral vectors for the treatment of diseases. The most relevant internalization pathways of these vectors and the few transfection results obtained using targeted and nontargeted liposomes are discussed below. The high cytotoxicity of cationic liposomes represents a significant challenge for the development of gene therapy and drug delivery. Anionic liposomes offer a promising alternative to address the limitations of conventional cationic liposomes, including immune response, short circulation time, and low toxicity. This review will discuss the advantages of cationic liposomes and the novel anionic liposome-based systems that have emerged as a result. The advent of novel designs and manufacturing techniques has facilitated the development of innovative systems, designated as lipid nanoparticles (LNPs), which serve as highly efficacious regulators of the immune system.

Emerging Cationic Nanovaccines

Cationic vaccines of nanometric sizes can directly perform the delivery of antigen(s) and immunomodulator(s) to dendritic cells in the lymph nodes. The positively charged nanovaccines are taken up by antigen-presenting cells (APCs) of the lymphatic system often originating the cellular immunological defense required to fight intracellular microbial infections and the proliferation of cancers. Cationic molecules imparting the positive charges to nanovaccines exhibit a dose-dependent toxicity which needs to be systematically addressed. Against the coronavirus, mRNA cationic nanovaccines evolved rapidly. Nowadays cationic nanovaccines have been formulated against several infections with the advantage of cationic compounds granting protection of nucleic acids in vivo against biodegradation by nucleases. Up to the threshold concentration of cationic molecules for nanovaccine delivery, cationic nanovaccines perform well eliciting the desired Th 1 improved immune response in the absence of cytotoxicity. A second strategy in the literature involves dilution of cationic components in biocompatible polymeric matrixes. Polymeric nanoparticles incorporating cationic molecules at reduced concentrations for the cationic component often result in an absence of toxic effects. The progress in vaccinology against cancer involves in situ designs for cationic nanovaccines. The lysis of transformed cancer cells releases several tumoral antigens, which in the presence of cationic nanoadjuvants can be systemically presented for the prevention of metastatic cancer. In addition, these local cationic nanovaccines allow immunotherapeutic tumor treatment.

Recent advances on vaccines against malaria: A review

This review aims to summarize the currently viable vaccine strategies including the approved vaccines and the those in trials for next-generation malaria vaccines. Data on malaria vaccine development was collected through a comprehensive review. The literature search was performed using databases including Google Scholar, PubMed, NIH, and Web of Science. Various novel approaches of vaccination are being developed, including those based on radiation-attenuated strategies, monoclonal antibodies, targeted immunogenic peptides, RNA and DNA vaccines, nanoparticle-based vaccines, protein-based vaccination protocols, and whole organism-based vaccination strategies. Trials on RTS, S have entered phase III testing, and those based on blood-stage vaccines and vaccines to interrupt malarial transmission have advanced to higher stages of trials. Mathematical modeling, combined drug and vaccine strategies, mass drug administration, polyvalent vaccine formulations, and targeted vaccination campaigns is playing an important role in malarial prevention. Furthermore, assessing coverage, accessibility, acceptability, deployment, compilation, and adherence to specific vaccination strategies in endemic regions is essential for vaccination drives against malaria.

RNA Combined with Nanoformulation to Advance Therapeutic Technologies

Nucleic acid-based therapies have the potential to address numerous diseases that pose significant challenges to more traditional methods. RNA-based therapies have emerged as a promising avenue, utilizing nanoformulation treatments to target a range of pathologies. Nanoformulation offers several advantages compared to other treatment modalities, including targeted delivery, low toxicity, and bioactivity suitable for drug loading. At present, various types of nanoformulations are available, such as liposomes, polymeric nanoparticles (NPs), magnetic NPs, nanoshells, and solid lipid nanoparticles (SLNs). RNA-based therapy utilizes intracellular gene nanoparticles with messenger RNA (mRNA) emerging prominently in cancer therapy and immunotechnology against infectious diseases. The approval of mRNA-based technology opens doors for future technological advancements, particularly self-amplifying replicon RNA (repRNA). RepRNA is a novel platform in gene therapy, comprising viral RNA with a unique molecular property that enables the amplification of all encoded genetic information countless times. As a result, repRNA-based therapies have achieved significant levels of gene expression. In this context, the primary objective of this study is to furnish a comprehensive review of repRNA and its applications in nanoformulation treatments, with a specific focus on encapsulated nanoparticles. The overarching goal is to provide an extensive overview of the use of repRNA in conjunction with nanoformulations across a range of treatments and therapies.

Malaria Vaccines: From the Past towards the mRNA Vaccine Era

Plasmodium spp. is the etiological agent of malaria, a life-threatening parasitic disease transmitted by infected mosquitoes. Malaria remains a major global health challenge, particularly in endemic regions. Over the years, various vaccine candidates targeting different stages of Plasmodium parasite life-cycle have been explored, including subunit vaccines, vectored vaccines, and whole organism vaccines with Mosquirix, a vaccine based on a recombinant protein, as the only currently approved vaccine for Plasmodium falciparum malaria. Despite the aforementioned notable progress, challenges such as antigenic diversity, limited efficacy, resistant parasites escaping protective immunity and the need for multiple doses have hindered the development of a highly efficacious malaria vaccine. The recent success of mRNA-based vaccines against SARS-CoV-2 has sparked renewed interest in mRNA vaccine platforms. The unique mRNA vaccine features, including their potential for rapid development, scalability, and flexibility in antigen design, make them a promising avenue for malaria vaccine development. This review provides an overview of the malaria vaccines' evolution from the past towards the mRNA vaccine era and highlights their advantages in overcoming the limitations of previous malaria vaccine candidates.