Next-Generation Immunotherapy Strategies Based on mRNA Lipid Nanoparticle Antibody Delivery

 

Monoclonal antibodies (mAbs) have become one of the most powerful therapeutic tools in modern medicine, particularly in the fight against viral pathogens. Highly potent neutralising antibodies have demonstrated clinical success against viruses such as Ebola, respiratory syncytial virus (RSV), influenza, and SARS-CoV-2 by directly blocking viral entry into host cells and preventing infection. These therapies provide immediate passive immunity and are especially valuable for vulnerable populations including immunocompromised patients and the elderly, for whom vaccines may not elicit adequate protection. Despite their therapeutic value, the traditional paradigm of recombinant monoclonal antibody production faces several major limitations. Manufacturing requires complex mammalian cell culture systems, large-scale bioreactors, extensive purification steps, and stringent cold-chain distribution. These requirements make antibody therapeutics expensive, slow to produce, and difficult to deploy rapidly during emerging outbreaks or pandemics.

The remarkable success of mRNA–lipid nanoparticle (mRNA/LNP) technology during the COVID-19 pandemic demonstrated the feasibility of delivering genetic instructions directly to human cells to produce therapeutic proteins in vivo. This concept has opened a transformative possibility: instead of manufacturing antibodies in industrial bioreactors, the body’s own cells can be instructed to synthesize therapeutic antibodies following delivery of mRNA encoding the antibody sequence. The study by Vu, Neil, Mackenzie-Kludas and colleagues provides a comprehensive preclinical evaluation of this approach. Their work investigates the delivery of mRNA encoding two human IgG1 monoclonal antibodies-PDI204 targeting the SARS-CoV-2 spike receptor-binding domain and HV-B10 targeting influenza hemagglutinin-using lipid nanoparticles. By comparing mRNA-encoded antibodies with conventionally administered recombinant proteins, the study provides critical insights into antibody design, pharmacokinetics, immunogenicity, biodistribution, and protective efficacy. Together, these findings highlight both the promise and the challenges of mRNA-encoded antibody therapeutics.

Engineering Antibodies Through mRNA Delivery

The central concept behind mRNA-encoded antibodies is straightforward but technologically sophisticated. Rather than delivering purified antibody proteins, synthetic mRNA molecules encoding the antibody heavy and light chains are packaged within lipid nanoparticles and administered to the host. After cellular uptake, the mRNA is translated by host ribosomes, allowing the transfected cells to assemble and secrete fully functional antibodies.

Vu et al. investigated two strategies for encoding full-length IgG antibodies. In the first approach, separate mRNA molecules encode the heavy chain (HC) and light chain (LC) of the antibody and are delivered together in a 1:1 ratio. The second approach uses a single bicistronic construct in which the heavy and light chains are linked by a furin cleavage sequence and a self-cleaving P2A peptide (HC-P2A-LC). The P2A element induces ribosomal skipping during translation, producing two separate proteins from a single open reading frame.

Both designs successfully generated functional antibody in HEK293T cells in vitro. However, when administered intravenously to mice, the single HC-P2A-LC construct produced significantly higher serum antibody concentrations and stronger viral neutralising activity than the two-mRNA mixture. The explanation is intuitive: when heavy and light chains are delivered as separate mRNAs, individual cells may receive only one of the two transcripts, preventing proper antibody assembly. In contrast, the bicistronic construct ensures that every successfully transfected cell produces both chains in equimolar amounts, greatly increasing the efficiency of IgG assembly and secretion.

This design strategy also simplifies manufacturing. Instead of producing two independent mRNA molecules and optimizing their encapsulation ratio, only a single transcript must be synthesized and formulated into lipid nanoparticles. All mRNA constructs in the study incorporated N1-methylpseudouridine, a modified nucleoside that reduces innate immune activation and enhances translation efficiency, a modification widely used in mRNA vaccines.

Lipid Nanoparticle Formulation and Biodistribution

The efficiency of mRNA delivery depends heavily on lipid nanoparticle formulation and route of administration. The investigators compared two LNP formulations: an anionic nanoparticle based on the ionisable lipid ALC-0315, similar to the lipid used in the Pfizer/BioNTech COVID-19 vaccine, and a cationic formulation containing MC3 and DOTAP.

Following intravenous or intramuscular administration, the ALC-0315 nanoparticles produced robust antibody expression in serum. Importantly, measurable antibody levels were also detected in bronchoalveolar lavage fluid, indicating that antibodies produced systemically can distribute to mucosal tissues in the respiratory tract. This observation is particularly relevant for respiratory pathogens, where neutralising antibodies at the airway surface represent the first line of defense against infection.

In contrast, the MC3-DOTAP nanoparticles performed poorly across all tested delivery routes. Even though positively charged nanoparticles were predicted to exhibit enhanced affinity for pulmonary cells, they generated only minimal antibody expression in vivo. Intranasal delivery of either nanoparticle formulation was largely ineffective, suggesting that standard vaccine-optimized LNPs are poorly suited for direct mucosal transfection.

These findings underscore an important principle in nucleic acid therapeutics: nanoparticle chemistry critically determines organ tropism and transfection efficiency. Formulations optimized for intramuscular vaccine delivery may not automatically translate into optimal systems for antibody production or mucosal targeting. Future improvements in lipid chemistry will likely be required to enhance targeted expression at respiratory epithelial surfaces.

Pharmacokinetics of mRNA-Encoded Antibodies

The pharmacokinetic profiles of mRNA-delivered antibodies differ fundamentally from those of recombinant protein therapeutics. When purified antibody proteins are administered intravenously, serum concentrations peak immediately and then decline slowly as the antibody undergoes FcRn-mediated recycling and clearance.

In contrast, mRNA-encoded antibodies exhibit a delayed peak in serum concentration. In the study by Vu et al., antibody levels gradually increased following mRNA/LNP administration and reached peak concentrations approximately three to five days after injection. This delay reflects the time required for cellular uptake of the nanoparticles, translation of the mRNA, and secretion of the assembled antibody.

Remarkably, peak antibody concentrations achieved through mRNA delivery were comparable to—and in the case of the influenza antibody HV-B10 even higher than—those obtained with equivalent doses of recombinant protein. This phenomenon illustrates one of the most intriguing aspects of nucleic acid therapeutics: biological amplification. A single mRNA molecule can be translated repeatedly by ribosomes, enabling transfected cells to produce large quantities of antibody over several days.

However, the elimination phase revealed an important limitation. Recombinant antibodies persisted in circulation for up to 70 days in mice, consistent with the long half-life characteristic of IgG molecules. In contrast, antibodies produced from mRNA/LNPs were largely cleared by day 28. The primary reason for this accelerated clearance was the development of anti-drug antibodies (ADAs) directed against the human monoclonal antibodies.

Anti-Drug Antibodies and Immunogenicity

All mice receiving mRNA-encoded antibodies developed significant anti-drug antibody responses beginning around day 7 post-administration. These ADA responses were largely absent in animals receiving recombinant protein alone. The difference arises from two interacting factors.

First, the lipid nanoparticles themselves possess intrinsic adjuvant activity. Ionisable lipids such as ALC-0315 can stimulate innate immune pathways and promote dendritic cell activation. While this property is beneficial in vaccine applications, where strong immune stimulation enhances antigen-specific immunity, it becomes problematic in therapeutic antibody delivery because it promotes immune recognition of the expressed antibody.

Second, the study employed human IgG antibodies in mice, creating a xenogeneic mismatch that naturally provokes immune recognition. The combination of xenogeneic protein and LNP-mediated immune stimulation produced strong ADA responses that accelerated antibody clearance.

Importantly, this limitation may be less severe in clinical settings. In humans receiving fully human antibodies, the species mismatch would not exist, and immunogenicity is expected to be significantly reduced. Nevertheless, minimizing LNP-induced immune stimulation remains an important goal for therapeutic applications.

Protective Efficacy Against SARS-CoV-2

The antiviral potential of mRNA-encoded antibodies was evaluated using a SARS-CoV-2 challenge model in transgenic mice expressing human ACE2 receptors. Animals received either recombinant PDI204 protein or PDI204 mRNA/LNPs and were challenged with SARS-CoV-2 seven days later.

Recombinant antibody administration provided strong protection, completely eliminating detectable viral replication in the lungs at the highest dose. The mRNA-encoded antibody also reduced viral loads, but the protective effect was more variable. This reduced efficacy was attributed to the emergence of anti-drug antibodies that diminished circulating antibody levels by the time of viral challenge.

Although the mRNA-delivered antibody did not achieve sterilizing immunity in this model, the results nevertheless demonstrated dose-dependent antiviral protection and confirmed that antibodies produced in vivo from mRNA are functionally active.

Superior Protection in an Influenza Challenge Model

A strikingly different outcome emerged in the influenza challenge experiments. In this model, mice were infected with a lethal dose of influenza virus only 24 hours after antibody administration. Because the challenge occurred before ADA responses could develop, the advantages of mRNA-encoded antibody production became apparent.

All animals receiving HV-B10 mRNA/LNP survived the infection across multiple dose levels, while recombinant protein administration provided only partial protection at the highest dose. The improved efficacy was attributed to higher early antibody concentrations achieved through mRNA-mediated expression. By harnessing the host’s translational machinery, the mRNA platform generated antibody levels that exceeded those achievable through a single protein infusion.

This experiment highlights the therapeutic window in which mRNA-encoded antibodies can outperform traditional approaches. When administered shortly before viral exposure, the platform can rapidly produce high concentrations of protective antibodies capable of preventing lethal infection

Advantages of the mRNA/LNP Antibody Platform

Beyond the specific experimental findings, the mRNA-encoded antibody platform offers several broader advantages over traditional recombinant protein therapeutics.

Rapid development and manufacturing: Recombinant antibody production requires months of cell line development, bioreactor optimization, and purification. In contrast, mRNA can be synthesized through cell-free in vitro transcription within days once the antibody sequence is known. This speed is especially valuable during emerging viral outbreaks.

Manufacturing scalability and cost: mRNA production requires far less infrastructure than mammalian cell culture systems. The same manufacturing pipeline can produce many different antibodies simply by changing the template DNA sequence.

Biological amplification: mRNA-based therapeutics exploit the host’s protein synthesis machinery, enabling each transfected cell to produce thousands of antibody molecules. This amplification can produce higher early antibody concentrations than direct protein infusion.

Platform flexibility: Multiple antibody sequences can be delivered simultaneously in a single nanoparticle formulation, potentially enabling combination therapies or simultaneous vaccination and passive immunization.

Human-native post-translational processing: Antibodies expressed by host cells acquire glycosylation patterns produced by the patient’s own cellular machinery, which may enhance compatibility and reduce immunogenicity.

Future Directions

Despite its promise, several challenges must be addressed to fully realize the therapeutic potential of mRNA-encoded antibodies. Reducing immunogenicity is a key priority. Next-generation lipid nanoparticles designed specifically for therapeutic delivery—rather than vaccine applications—may reduce innate immune activation and ADA formation. Self-amplifying RNA technologies may also allow effective antibody production at significantly lower doses, minimizing exposure to immunostimulatory lipids.

Improving mucosal delivery is another important objective. Respiratory viruses initiate infection at epithelial surfaces, and achieving high antibody concentrations at these sites would enhance prophylactic efficacy.

Conclusion

The work of Vu and colleagues provides a comprehensive evaluation of mRNA lipid nanoparticle delivery as a platform for monoclonal antibody therapeutics. Their findings demonstrate that mRNA-encoded antibodies can be efficiently produced in vivo, achieve therapeutically relevant concentrations, and protect against viral infection in animal models. While anti-drug antibody responses currently limit durability in preclinical systems, this limitation may be less pronounced in human applications and can be addressed through advances in nanoparticle engineering and RNA design.

More broadly, the mRNA antibody platform represents a fundamental shift in the paradigm of biologic drug development. Instead of manufacturing therapeutic proteins in centralized facilities, the genetic instructions for those proteins can be delivered directly to the patient, allowing the body itself to become a transient bioreactor. By combining rapid design, scalable manufacturing, and powerful biological amplification, mRNA-encoded antibodies have the potential to transform how passive immunity is deployed against emerging infectious diseases.

Reference

Vu, M.N., Neil, J.A., Mackenzie-Kludas, C., Kelly, A., Tan, H.-X., Subbarao, K., Lee, W.S., & Wheatley, A.K. (2026). Delivery of monoclonal antibodies using mRNA lipid nanoparticles confers protection against SARS-CoV-2 and influenza. Molecular Therapy – Nucleic Acids. https://doi.org/10.1016/j.omtn.2026.102873

Image credit: Portions of the figure in this article were generated using ChatGPT (OpenAI) or Google Gemini.

Disclaimer: This blog post is intended solely for educational and scientific informational purposes. Any mention of therapeutic drug names, including FDA-approved medications, is for the purpose of accurate reporting and discussion of biomedical research and does not constitute medical advice, endorsement, or promotion. Readers should not interpret the content as a recommendation for any specific treatment. Always consult a qualified healthcare professional for medical advice or treatment decisions.

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