By Hendra Lukman 
The COVID-19 pandemic irrevocably altered the global health landscape, thrusting messenger RNA (mRNA) vaccines into unprecedented public and scientific prominence. Following rigorous clinical trials, the first COVID-19 mRNA vaccine was administered on December 8, 2020, marking a watershed moment in pandemic response. Subsequent modeling by researchers estimated that these groundbreaking vaccines were instrumental in preventing at least 14.4 million deaths worldwide within their initial year of deployment, a testament to their remarkable efficacy.
This profound impact has catalyzed a significant acceleration in mRNA vaccine research and development, extending beyond SARS-CoV-2 to target a spectrum of formidable infectious diseases. Promisingly, ongoing clinical trials are actively investigating mRNA vaccine candidates for influenza virus, Respiratory Syncytial Virus (RSV), HIV, Zika, Epstein-Barr virus, and even tuberculosis bacteria. However, parallel studies examining the performance and limitations of existing COVID-19 mRNA vaccines have illuminated critical areas for improvement, underscoring the imperative for novel vaccine strategies that can overcome inherent challenges.
Addressing the Hurdles: Performance and Production Challenges of mRNA Vaccines
Despite their historic success, COVID-19 mRNA vaccines are not without their limitations. A key concern is the variability in the immune protection they elicit, which can differ significantly from one individual to another. Furthermore, this protective immunity is not enduring, waning over time. This challenge is exacerbated by the relentless evolution of the SARS-CoV-2 virus, which continuously generates new variants capable of partially evading pre-existing immune defenses. Consequently, the need for frequent vaccine updates becomes a recurring necessity, placing a strain on public health systems and vaccine manufacturers alike.
Beyond immunological performance, practical considerations present substantial obstacles. The manufacturing of mRNA vaccines is an intricate and costly process. Precisely controlling the quantity of mRNA molecules encapsulated within lipid nanoparticles, a critical component for delivering the genetic material into cells, remains a significant technical hurdle. These vaccines also necessitate stringent cold storage conditions to maintain their stability and efficacy, a logistical challenge particularly in resource-limited settings. Moreover, concerns persist regarding potential unintended off-target effects. Addressing these multifaceted limitations is paramount to enhancing global preparedness and improving the effectiveness of responses to future infectious disease threats.
A Novel Approach: The DoriVac DNA Origami Vaccine Platform
In response to these pressing challenges, a multidisciplinary team comprising researchers from the Wyss Institute at Harvard University, the Dana-Farber Cancer Institute (DFCI), and collaborating institutions has embarked on an exploration of an innovative alternative: the DoriVac DNA origami nanotechnology platform. This novel approach functions as both a vaccine and an adjuvant, a substance that enhances the immune system’s response to an antigen.
The DoriVac vaccines are meticulously engineered to target specific peptide regions, such as the HR2 domain found within the spike proteins of a variety of viruses, including SARS-CoV-2, HIV, and Ebola. Initial preclinical studies in mouse models demonstrated that the SARS-CoV-2 HR2 DoriVac vaccine elicited robust immune responses, characterized by both antibody-driven (humoral) immunity and T cell-driven (cellular) immunity. These two arms of the immune system are crucial for combating viral infections, with antibodies neutralizing the virus and T cells directly killing infected cells.
To further validate the platform’s potential in a human context, the research team utilized the Wyss Institute’s advanced microfluidic human Organ Chip technology. This sophisticated system simulates key aspects of the human immune system, including the microenvironment of a lymph node, in vitro. Within this preclinical human model, the SARS-CoV-2 HR2 DoriVac vaccine similarly generated potent antigen-specific immune responses in human cells, mirroring the findings in mice and offering a more predictive assessment of human immune activity.
In a pivotal head-to-head comparison against SARS-CoV-2 mRNA vaccines delivered via lipid nanoparticles, a DoriVac vaccine encoding the same spike protein variant demonstrated comparable levels of immune activation in these human models. However, the DNA origami vaccine exhibited distinct advantages, notably in its enhanced stability and simplified storage and manufacturing requirements. These groundbreaking findings were recently published in the esteemed journal Nature Biomedical Engineering, marking a significant advancement in vaccine technology.
"With the DoriVac platform, we have developed an extremely flexible chassis with a number of critical advantages, including an unprecedented control over vaccine composition, and the ability to program immune recognition in targeted immune cells on a molecular level to achieve better responses," stated co-corresponding author William Shih, Ph.D., a Core Faculty member at the Wyss Institute and a pioneering figure in the development of this new vaccine concept. Dr. Shih, who also holds professorships at Harvard Medical School and DFCI, elaborated, "Our study demonstrates DoriVac’s versatility and potential by taking a close look at the immune changes that are required to fight infectious viruses."
The Architecture of DNA Origami Vaccines: Precision at the Nanoscale
The genesis of the DoriVac platform traces back to 2024, when Dr. Shih’s team at the Wyss Institute and Dana-Farber introduced it as a DNA nanotechnology-based vaccine solution with broad applicability. Yang (Claire) Zeng, M.D., Ph.D., who spearheaded this initiative alongside collaborators, showcased DoriVac’s ability to precisely present immune-stimulating adjuvant molecules to cells at the nanoscale, a feat of molecular engineering.
Earlier investigations, conducted in tumor-bearing mice, had already indicated that DoriVac vaccines could elicit more potent immune responses compared to vaccine formulations lacking the intricate DNA origami structure. The construction of DoriVac vaccines involves the self-assembly of minuscule, square DNA nanostructures. One surface of these nanostructures is adorned with adjuvant molecules, strategically positioned at carefully controlled nanometer distances. The opposite surface is designed to present selected antigens, such as peptides or proteins derived from tumors or pathogens, thereby directing the immune system’s attention to specific threats.
"While we were developing the platform for cancer applications, the COVID-19 pandemic was still moving with full force. So, the question quickly arose whether DoriVac’s superior adjuvant activity could also be leveraged in infectious disease settings," explained Dr. Zeng, who is the first and co-corresponding author on the recent study and has since become a co-founder and CEO/CTO of DoriNano, a company focused on translating this technology into clinical applications.
Driven by this compelling question, Dr. Zeng, in collaboration with co-first author Olivia Young, Ph.D., a former graduate student in Dr. Shih’s group, joined forces with Donald Ingber’s team at the Wyss Institute. Dr. Ingber’s research group is at the forefront of antiviral innovation, employing artificial intelligence, multiomics approaches, and microfluidic human Organ Chip systems. Together, with co-first author Longlong Si, Ph.D., a former postdoctoral researcher in Dr. Ingber’s lab, the researchers successfully developed DoriVac vaccines specifically targeting SARS-CoV-2, HIV, and Ebola. These vaccines were designed to present HR2 peptides, which serve as conserved antigens within the spike proteins of these viruses, meaning they are less likely to mutate and evade immune responses.
"Our analysis of the immune responses provoked by these first DoriVac vaccines in mice led to several encouraging observations, including significantly greater and broader activation of humoral and cellular immunity across a range of relevant immune cell types than what the origami-free antigens and adjuvants could produce," Dr. Zeng reported. She further elaborated on the specific immune enhancements observed: "We found that the numbers of antibody-producing B cells, activated antigen-presenting dendritic cells (DCs), and antigen-specific memory and cytotoxic T cell types that are vital for long-term protection were all increased, especially in the case of the SARS-CoV-2 HR2."
Bridging the Gap: From Mouse Models to Human Systems
A persistent challenge in vaccine development is the often-observed divergence between immune responses in mice and their manifestation in humans. This translational gap has historically led to the failure of numerous promising preclinical treatments during human clinical trials. To mitigate this risk and improve the predictability of human outcomes, the research team strategically employed a human lymph node-on-a-chip (human LN Chip) system. This advanced microfluidic device is designed to meticulously mimic key aspects of the human immune system.
This innovative system, further refined by co-first author Min Wen Ku and co-corresponding author Girija Goyal, Ph.D., Director of Bioinspired Therapeutics at the Wyss Institute, provided a crucial testing ground. The results from the human LN Chip experiments demonstrated that the SARS-CoV-2-HR2 DoriVac vaccine effectively activated human dendritic cells (DCs), leading to a significant increase in their production of inflammatory cytokines – signaling molecules that orchestrate immune responses. Moreover, the vaccine enhanced the numbers of CD4+ and CD8+ T cells, both of which play critical roles in protective immunity, further bolstering the platform’s potential for human application.
"The predictive capabilities of human LN Chips gave us an ideal testing ground for DoriVac vaccines and the induced, antigen-specific immune cell profiles and activities very likely reflect those that would occur in human recipients of the vaccines," stated co-corresponding author Donald Ingber, M.D., Ph.D. Dr. Ingber, who also holds distinguished professorships at Harvard Medical School, Boston Children’s Hospital, and the Harvard John A. Paulson School of Engineering and Applied Sciences, emphasized the convergence of technologies: "This convergence of technologies enabled us to dramatically raise the chances of success for a new class of vaccines and create a new testbed for future vaccine developments."
A Direct Confrontation: DoriVac Versus mRNA Vaccines
In a critical phase of their research, the team conducted a direct comparison between a DoriVac vaccine presenting the full SARS-CoV-2 spike protein and commercially available mRNA lipid nanoparticle (LNP) vaccines from Moderna and Pfizer/BioNTech, which encode the same spike protein. Led by Dr. Zeng and co-author Qiancheng Xiong, the researchers subjected both vaccine types to a standard booster regimen in mice. The results indicated that both the DoriVac vaccine and the mRNA vaccines elicited comparable antiviral T cell and antibody-producing B cell responses.
"This underscored DoriVac’s potential as a DNA nanotechnology-enabled, self-adjuvanted vaccine platform," Dr. Shih remarked. He further highlighted the distinct advantages of DoriVac: "But DoriVac vaccines have a number of other advantages: they don’t have the same cold-chain requirements as mRNA-LNP vaccines do and thus could be distributed much more effectively, especially in under-resourced regions; and they could overcome some of the enormous manufacturing complexities of LNP-formulated vaccines, to name two major ones." Recent studies conducted at DoriNano have also indicated a promising safety profile for DoriVac vaccines, further strengthening their potential.
The comprehensive study involved a broad team of researchers, with additional authors including Sylvie Bernier, Hawa Dembele, Giorgia Isinelli, Tal Gilboa, Zoe Swank, Su Hyun Seok, Anjali Rajwar, Amanda Jiang, Yunhao Zhai, LaTonya Williams, Caleb Hellman, Chris Wintersinger, Amanda Graveline, Andyna Vernet, Melinda Sanchez, Sarai Bardales, Georgia Tomaras, Ju Hee Ryu, and Ick Chan Kwon. Funding for this groundbreaking research was provided by several esteemed organizations, including the Director’s Fund and Validation Project program of the Wyss Institute; the Claudia Adams Barr Program at DFCI; the National Institutes of Health (U54 grant CA244726-01); the US-Japan CRDF global fund (grant R-202105-67765); the National Research Foundation of Korea (grants MSIT, RS-2024-00463774, RS-2023-00275456); the Intramural Research Program of the Korea Institute of Science and Technology (KIST); and the Bill and Melinda Gates Foundation (INV-002274). The collective efforts and diverse funding sources underscore the global significance and collaborative nature of this pioneering work in vaccine development.