By Hendra Lukman 
The advent of messenger RNA (mRNA) vaccines, propelled into the global consciousness by the COVID-19 pandemic, heralded a new era in infectious disease prevention. Following rigorous clinical trials, the first COVID-19 mRNA vaccine was administered on December 8, 2020, a landmark event that quickly demonstrated its profound impact. Subsequent modeling efforts revealed that these vaccines were instrumental in averting an estimated 14.4 million deaths worldwide within their inaugural year. This remarkable success has catalyzed extensive research into expanding mRNA technology to combat a spectrum of other infectious agents. However, ongoing studies of existing COVID-19 mRNA vaccines have also illuminated inherent limitations, underscoring the critical need for innovative vaccine strategies.
The Promise and Perils of mRNA Vaccines
The groundbreaking success of mRNA vaccines in curbing the COVID-19 pandemic has spurred a rapid expansion of research and development into their application against other infectious diseases. Scientists are actively pursuing mRNA vaccine candidates for influenza virus, Respiratory Syncytial Virus (RSV), HIV, Zika, Epstein-Barr virus, and even tuberculosis bacteria, with numerous clinical trials currently underway. This broad application highlights the transformative potential of the mRNA platform.
Despite their triumphs, current mRNA vaccine technology faces several significant challenges that temper expectations for universal application and require careful consideration for future pandemic preparedness.
Performance Limitations
One of the primary hurdles is the variability in immune protection elicited by COVID-19 mRNA vaccines. The strength and duration of immune responses can differ substantially from person to person. Furthermore, the protection afforded by these vaccines is not indefinite, necessitating booster shots to maintain efficacy. This challenge is compounded by the relentless evolution of the SARS-CoV-2 virus, which continuously generates new variants capable of partially evading pre-existing immune defenses. Consequently, vaccine formulations often require frequent updates to remain effective against emerging strains.
Production and Practical Hurdles
Beyond performance limitations, practical and logistical challenges also present significant obstacles. The manufacturing of mRNA vaccines is an intricate and costly process. Precise control over the quantity of mRNA molecules encapsulated within lipid nanoparticles (LNPs), a crucial component for vaccine delivery, remains technically demanding. Additionally, these vaccines necessitate stringent cold-chain storage conditions, which can complicate distribution, particularly in resource-limited regions. The potential for unintended off-target effects, though generally considered low with current mRNA vaccines, also remains an area of ongoing investigation. Overcoming these multifaceted limitations is paramount to enhancing global preparedness and response capabilities for future infectious disease threats.
DNA Origami: A Novel Nanotechnology Platform for Vaccine Development
In response to these challenges, a multidisciplinary team from the Wyss Institute at Harvard University, the Dana-Farber Cancer Institute (DFCI), and collaborating institutions has pioneered an innovative approach utilizing a DNA origami nanotechnology platform. This platform, named DoriVac, functions as a dual-purpose entity, acting as both a vaccine and an adjuvant.
The researchers designed DoriVac vaccines to target the conserved HR2 peptide region found within the spike proteins of a variety of viruses, including SARS-CoV-2, HIV, and Ebola. This strategic targeting aims to elicit robust immune responses against conserved viral components, potentially offering broader protection across different viral strains and even across different viruses.
Preclinical Success in Mice and Human Models
In preclinical studies conducted in mice, the SARS-CoV-2 HR2 DoriVac vaccine demonstrated its capacity to induce potent immune responses, encompassing both antibody-driven (humoral) and T cell-driven (cellular) immunity. This dual-pronged attack is considered essential for effective viral clearance and long-term immunological memory.
Further validating its potential, the research team extended their investigations to a preclinical human model. Employing the Wyss Institute’s advanced microfluidic human Organ Chip technology, which meticulously simulates a human lymph node in vitro, the scientists observed that the SARS-CoV-2 HR2 DoriVac vaccine also generated robust antigen-specific immune responses within human cells. This in vitro human model offers a more predictive platform for assessing vaccine efficacy compared to traditional animal models, which often fail to fully recapitulate human immune responses.
In a direct comparison with current SARS-CoV-2 mRNA vaccines delivered via lipid nanoparticles, a DoriVac vaccine encoding the same spike protein variant elicited similarly strong immune activation in these human models. Crucially, the DNA origami vaccine demonstrated distinct advantages in terms of stability and ease of storage and manufacture. These groundbreaking findings were recently published in the prestigious journal Nature Biomedical Engineering.
Expert Perspectives on DoriVac’s Advantages
William Shih, Ph.D., a co-corresponding author on the study and a Core Faculty member at the Wyss Institute, highlighted the platform’s inherent flexibility and critical advantages. "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 Dr. Shih, who is also a Professor at Harvard Medical School and DFCI. He further elaborated on the study’s demonstration of DoriVac’s versatility and potential, particularly in understanding the precise immune changes required to combat infectious viruses.
The Architecture and Development of DNA Origami Vaccines
The conceptualization and development of DoriVac as a DNA nanotechnology-based vaccine platform with broad potential applications began in 2024 under Dr. Shih’s leadership at the Wyss Institute and DFCI. Yang (Claire) Zeng, M.D., Ph.D., spearheaded this effort, demonstrating DoriVac’s capacity to precisely present immune-stimulating adjuvant molecules to cells at the nanoscale.
A Foundation in Cancer Research
Initial studies of the DoriVac platform were focused on cancer applications. These earlier investigations in tumor-bearing mice revealed that DoriVac vaccines were capable of eliciting stronger immune responses compared to vaccine formulations lacking the DNA origami structure. This established a precedent for the platform’s ability to enhance immune engagement.
DoriVac vaccines are constructed from microscopic, self-assembling square DNA nanostructures. One surface of these nanostructures is engineered to display adjuvant molecules arranged at precisely controlled nanometer distances, while the opposing surface presents selected antigens, such as peptides or proteins derived from tumors or pathogens. This intricate nanoscale architecture allows for a highly controlled presentation of immune-stimulating components.
Pivoting to Infectious Diseases
The onset and persistent impact of the COVID-19 pandemic prompted a crucial question: could DoriVac’s superior adjuvant activity be harnessed for infectious disease prevention? "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 a first and co-corresponding author on the new study. Dr. Zeng has since co-founded DoriNano, a company dedicated to translating this technology into clinical applications.
To explore this avenue, Dr. Zeng and co-first author Olivia Young, Ph.D., a former graduate student in Dr. Shih’s group, collaborated with Donald Ingber’s team at the Wyss Institute. Dr. Ingber’s research group is at the forefront of antiviral innovation, leveraging artificial intelligence, multiomics approaches, and microfluidic human Organ Chip systems. Working alongside co-first author Longlong Si, Ph.D., a former postdoctoral researcher in Dr. Ingber’s lab, the researchers successfully developed DoriVac vaccines targeting SARS-CoV-2, HIV, and Ebola. These vaccines were designed to present HR2 peptides, acting as conserved antigens within viral spike proteins, a strategy aimed at eliciting broad and durable immune responses.
Encouraging Findings in Mouse Models
The initial analysis of immune responses triggered by these pioneering DoriVac vaccines in mice yielded highly encouraging results. "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," reported Dr. Zeng. The study observed marked increases in antibody-producing B cells, activated antigen-presenting dendritic cells (DCs), and antigen-specific memory and cytotoxic T cell populations – all vital for long-term protection. These enhancements were particularly pronounced in the context of the SARS-CoV-2 HR2 vaccine.
Bridging the Gap: From Mouse Studies to Human Relevance
A persistent challenge in vaccine development is the frequent disconnect between immune responses observed in mouse models and those that occur in humans. This translational gap has unfortunately led to the failure of numerous promising therapeutic candidates during clinical trials. To mitigate this risk and improve the predictability of human outcomes, the research team strategically employed the human lymph node-on-a-chip (human LN Chip) system. This sophisticated in vitro model effectively mimics key aspects of the human immune system.
Predictive Power of the Human LN Chip
The human LN Chip system, further advanced by co-first author Min Wen Ku and co-corresponding author Girija Goyal, Ph.D., Director of Bioinspired Therapeutics at the Wyss Institute, demonstrated that the SARS-CoV-2-HR2 DoriVac vaccine effectively activated human DCs. This activation was accompanied by a significant increase in their production of inflammatory cytokines when compared to non-origami-based components. Moreover, the system showed an increased presence of CD4+ and CD8+ T cells exhibiting multiple protective functions, providing robust evidence for the platform’s potential utility in human applications.
Dr. Ingber, M.D., Ph.D., a co-corresponding author and a distinguished professor at Harvard Medical School, Boston Children’s Hospital, and the Harvard John A. Paulson School of Engineering and Applied Sciences, emphasized the predictive capabilities of this technology. "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. 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," Dr. Ingber stated.
Head-to-Head Comparison: DoriVac Versus mRNA Vaccines
To provide a definitive assessment of DoriVac’s performance relative to existing mRNA vaccine technology, the researchers conducted a direct comparison. They evaluated a DoriVac vaccine designed to present the full SARS-CoV-2 spike protein. Under the leadership of Dr. Zeng and co-author Qiancheng Xiong, the team pitted this DoriVac formulation against commercially available Moderna and Pfizer/BioNTech mRNA lipid nanoparticle (LNP) vaccines, both of which encode the same spike protein.
Comparable Efficacy, Superior Practicality
Utilizing a standard booster immunization approach in mice, both vaccine types demonstrated comparable efficacy in eliciting antiviral T cell and antibody-producing B cell responses. This finding underscores DoriVac’s potential as a viable alternative to current mRNA vaccines.
However, the advantages of DoriVac extend beyond comparable immunogenicity. "This underscored DoriVac’s potential as a DNA nanotechnology-enabled, self-adjuvanted vaccine platform. 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," explained Dr. Shih. Recent studies conducted at DoriNano have also indicated a promising safety profile for DoriVac.
Broader Implications and Future Directions
The development of the DoriVac platform represents a significant stride in vaccine innovation, offering a compelling alternative with distinct advantages over existing mRNA technology. Its inherent stability, simplified storage requirements, and potentially less complex manufacturing processes could revolutionize vaccine accessibility and distribution, particularly in low-resource settings. This could be instrumental in addressing global health disparities and improving pandemic preparedness worldwide.
The versatility of the DNA origami approach also opens doors for the development of multi-valent vaccines capable of targeting multiple pathogens or multiple strains of a single pathogen simultaneously. Furthermore, the ability to precisely control the presentation of antigens and adjuvants at the nanoscale provides an unprecedented level of customization for optimizing immune responses against a wide range of diseases, including challenging infectious agents and cancers.
The research team’s commitment to rigorous preclinical validation, including the use of advanced human Organ Chip models, significantly de-risks the translation of this technology into human clinical trials. The convergence of nanotechnology, immunology, and advanced modeling techniques employed in this study sets a new benchmark for future vaccine development. As the world continues to grapple with existing and emerging infectious disease threats, platforms like DoriVac offer a beacon of hope for more robust, accessible, and effective immunization strategies.
The study’s comprehensive list of authors includes 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 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).
