Dendritic-Cell-Targeting Virus-Like Particles as Potent mRNA Vaccine Carriers

Infectious Diseases Rheumatology and Immunology Biochemistry Bioengineering Life Sciences Immunology Medicine Cell Biology
dendritic cells virus-like particles mRNA vaccine SARS-CoV-2 high efficacy

Dendritic-cell-targeting Virus-like Particles as Potent mRNA Vaccine Carriers

Introduction

In vaccine development, especially mRNA vaccines, significant achievements have been made in recent years. The mRNA vaccines developed by Moderna and Pfizer/BioNTech against COVID-19 have set a successful precedent, greatly advancing the development of mRNA vaccines. However, the existing mRNA vaccines lack specificity for certain cell types, particularly dendritic cells (DCs), which are crucial in antigen presentation. Dendritic cells are the primary antigen-presenting cells that can effectively initiate T cell immune responses and antibody responses. Yet, existing mRNA vaccines, such as LNPs (Lipid Nanoparticles), cannot specifically deliver mRNA to these cells. Moreover, there are some viral infections, like HIV and HSV, and even some non-infectious diseases such as cancer, for which there are still no effective preventive or therapeutic vaccines.

Paper Source

This paper was published by Nature Biomedical Engineering, titled “Dendritic-cell-targeting virus-like particles as potent mRNA vaccine carriers.” The research team primarily comes from the Ministry of Education Key Laboratory of Systems Biomedicine at Shanghai Jiao Tong University, the Basic Medical School of Fudan University, and other research institutions in Shanghai, Hangzhou, and relevant research centers. This paper describes the development of a novel dendritic-cell-targeting virus-like particle (dVLP) and its study as an mRNA vaccine carrier.

Research Workflow

Design and Characterization

To verify the potential of dVLP as an mRNA vaccine carrier, the research team designed a candidate SARS-CoV-2 mRNA vaccine. This vaccine contains the full-length SARS-CoV-2 spike protein mRNA and incorporates the MS2 hairpin structure at its end to enhance the stability and expression level of the mRNA, while introducing two proline substitution mutations (K986P/V987P) to improve stability. The research team used electron microscopy to observe the morphology of dVLP and found these particles to exhibit a circular structure of approximately 120nm.

To verify whether the spike protein mRNA was successfully packaged into VLPs, the team conducted reverse transcription quantitative polymerase chain reaction (RT-qPCR) and RNA immunoprecipitation (RIP) experiments. They found that the mRNA could be specifically packaged into VLPs through RNA-protein interactions. Next, the team used Western blotting to analyze the successful incorporation of the spike protein into VLPs, indicating that dVLP could effectively deliver spike protein mRNA.

Immunogenicity Experiments

When the dVLP-SARS-CoV-2 mRNA vaccine was injected into the mice’s footpads, it was found that this vaccine induced higher and more durable antigen-specific IgG titers and cellular immune responses compared to non-targeted VLP and LNP formulations. Mass spectrometry analysis showed that the spike protein on the VLP surface was N-linked glycosylated, similar to the characteristics of SARS-CoV-2. Subsequently, the team examined the immunogenicity of the spike protein sequence, using mutation experiments in E. coli and bacteriophages to validate the expression and translation of the spike protein in dVLP.

Main Research Results

Antibody Response

Using enzyme-linked immunosorbent assay (ELISA), the research team demonstrated that a single injection of 2 μg of dVLP–S-mut was sufficient to trigger a potent neutralizing immune response in mice. Next, through pseudovirus neutralization assays, the neutralizing capacity of the vaccinated mice sera was validated, revealing that high titers of neutralizing antibodies could effectively resist live virus infection. Similarly, short-term and long-term follow-up experiments in mice showed that a single dose of the vaccine elicited a lasting spike-specific IgG response. Notably, the study also found that intranasal administration could induce spike-specific IgA in the lungs, indicating that the vaccine technology might be used for intranasal vaccines to block SARS-CoV-2 infection.

Cellular Immune Response

To analyze the effects of dVLP–mRNA vaccine on cellular immune response, the research team stimulated mouse spleen cells with spike protein peptide mixtures. ELISPOT experiments revealed that dVLP–mRNA vaccine, particularly dVLP pseudotyped with SV-G, induced significant production of cytokines (IFN-γ, TNF-α, and IL-2). This result indicated that dVLP–mRNA vaccine elicited a stronger T cell response compared to LNP–mRNA vaccine.

In vivo Distribution

To explore the mechanisms leading to the improved efficacy of dVLP vaccines, the research team directly compared the performance of LNPs, VSV-G VLPs, and dVLPs at mRNA and protein levels. It was found that dVLPs significantly enriched mRNA in lymph nodes within 12 hours after injection, while VLPs showed similar amounts of mRNA at the injection site and in lymph nodes. Moreover, immunofluorescence analysis showed that the spike protein delivered by dVLP could be specifically expressed in dendritic cells within the lymph nodes.

Vaccine Efficacy

To verify the protective efficacy of dVLP–mRNA vaccine in mice, the research team used live SARS-CoV-2 to infect hACE2 transgenic mice. The results showed that mice vaccinated with dVLP–mRNA vaccine maintained stable weight, significantly reduced viral load, and showed no obvious SARS-CoV-2 lesions in the lungs. Similarly, the study demonstrated that dVLP–mRNA vaccine also protected mice from HSV infection, significantly reducing viral replication in the skin and nervous system.

Conclusion and Significance

This study developed a novel dVLP–mRNA vaccine carrier, demonstrating its potential in specifically delivering mRNA to dendritic cells and verifying its superior immune effect and effective protection against viral infections through various experiments. Compared to existing LNP–mRNA vaccines, dVLP–mRNA vaccines offer significant advantages in inducing stronger antibody and cell immune responses. In the future, this technology may be applied to therapeutic vaccines for cancer or chronic viral infections, enhancing vaccine efficacy and safety.

This research is expected to provide new ideas and technical support for the development of mRNA vaccine technology, addressing many challenges currently faced in vaccine development. The research team pointed out that future efforts could involve further optimizing the efficacy of dVLP–mRNA vaccines using circular RNA or self-amplifying RNA, thereby reducing vaccine dosage and cost.