A collaborative research team from The Wistar Institute, the University of Pennsylvania Perelman School of Medicine, and Pennsylvania-based biotechnology company INOVIO has successfully developed a next-generation vaccination technology that combines plasmid DNA with lipid nanoparticle (LNP) delivery systems, potentially transforming how DNA vaccines are administered and enhancing their effectiveness.
The breakthrough findings, published in Cell Reports Medicine in a paper titled "Modulation of lipid nanoparticle-formulated plasmid DNA drives innate immune activation promoting adaptive immunity," demonstrate how researchers overcame longstanding challenges in DNA vaccine delivery.
Overcoming DNA Delivery Challenges
While lipid-based approaches, including LNPs, have successfully delivered various forms of RNA and protein-based therapeutics in marketed products, DNA has proven more difficult to formulate effectively due to its larger size and double-stranded nature.
Led by Nicholas Tursi, a doctoral student in Dr. David Weiner's laboratory at The Wistar Institute, the research team focused on modifying lipid-based formulations to better stabilize DNA in LNPs, which could simplify delivery and improve vaccine-induced immunity.
"DNA vaccines have traditionally required specialized delivery devices to achieve efficient cellular uptake and potent T cell immunity," explained Dr. Weiner, Wistar executive vice president and a leading expert in DNA vaccines. "Our goal was to develop an LNP formulation that would enable administration by standard needle and syringe while potentially enhancing humoral immunity."
Optimized Formulation Yields Superior Results
The researchers discovered that DNA-LNPs formulated at higher N/P ratios—the relationship between the lipid nanoparticle and the larger DNA backbone—led to improved particle profiles, smaller particle sizes, and enhanced immune responses.
Using a model DNA-LNP expressing influenza hemagglutinin (HA), the team examined how modulating the formulation could improve particle assembly and stability for direct injection. Their findings revealed that these optimized DNA-LNPs demonstrated a unique mechanism for priming the immune system compared to mRNA and protein-in-adjuvant formulations.
"The DNA-LNP induced a unique activation pattern of innate immune populations—cells that respond early in the development of a protective immune response," Tursi noted. "This distinctive immunological signature appears to contribute to the robust adaptive immunity we observed."
Robust and Durable Immune Responses
When compared to benchmark mRNA and protein-in-adjuvant vaccines, the HA DNA-LNPs induced robust antibody and T cell responses after a single dose. Importantly, these responses proved durable, with memory responses in small animals persisting beyond a year after immunization.
The team also examined the immunogenicity of HA DNA-LNPs in a rabbit model, where they observed strong T cell and antibody responses that persisted into the memory phase, confirming the technology's potential across different animal models.
Protective Efficacy Against SARS-CoV-2
In perhaps the most compelling demonstration of the technology's potential, the researchers tested whether DNA-LNP vaccines could provide protection in a live SARS-CoV-2 challenge model. Using a DNA-LNP vaccine expressing the SARS-CoV-2 spike protein, they showed that a single immunization successfully prevented morbidity and mortality from viral challenge.
"The positive results highlight the potential of DNA-LNPs to simplify vaccine delivery and provide durable protection. This is a significant step forward in DNA-based immunization," said Dr. Weiner.
Implications for Future Vaccine Development
This study supports the continued development of DNA-LNP vaccines as a unique vaccination modality. The ability for this approach to trigger strong, long-lasting immune responses highlights its potential to complement existing approaches or be developed as a next-generation immunization platform.
The technology could potentially address several limitations of current vaccine platforms. Unlike traditional DNA vaccines, the DNA-LNP formulation eliminates the need for specialized delivery devices. Compared to mRNA vaccines, DNA is inherently more stable, potentially reducing cold chain requirements for storage and distribution.
The research was supported by multiple NIH grants, including funding from the Collaborative Influenza Vaccine Innovation Centers (CIVIC), as well as INOVIO Pharmaceuticals and other foundations.
As vaccine technology continues to evolve, this DNA-LNP platform represents a promising addition to the immunization toolkit, potentially offering advantages in terms of simplicity, durability, and protective efficacy for addressing future infectious disease challenges.
