The influenza virus remains a formidable public health challenge due to its rapid antigenic drift and occasional antigenic shift, mechanisms that allow it to evade immune recognition and reduce vaccine effectiveness. Traditionally, flu vaccines have primarily targeted hemagglutinin, the main protein responsible for viral attachment and entry into host cells. However, the new mRNA vaccine uniquely incorporates coding sequences for neuraminidase as well, an enzyme that facilitates viral release and propagation. This dual-targeting strategy is designed to elicit a broader and more robust immune response, potentially overcoming the limitations of current vaccines that often show variable effectiveness from year to year.

The researchers engineered a lipid nanoparticle (LNP)-encapsulated mRNA vaccine encoding full-length HA and NA proteins derived from the predominant influenza strains predicted for the upcoming season. By leveraging the mRNA vaccine platform, which gained widespread recognition during the COVID-19 pandemic, this approach enables rapid and precise antigen production within host cells, eliciting both humoral and cellular immunity. The inclusion of neuraminidase is particularly notable, as antibodies against NA can inhibit viral spread and are correlated with reduced disease severity, yet have been historically underrepresented in vaccine formulations.

Preclinical studies demonstrated that the vaccine prompts robust antigen expression in vivo, leading to a potent neutralizing antibody response against multiple influenza subtypes. The dual antigen design also showed promise in eliciting cross-reactive immunity, an essential feature given the high mutation rate of influenza viruses. Importantly, the safety profile was thoroughly assessed in animal models, with no significant adverse effects observed, providing compelling evidence for the potential of this vaccine to progress through clinical trials.

A critical aspect of this research is the detailed evaluation of immunogenicity—the vaccine’s ability to stimulate an immune response. Hemagglutination inhibition (HAI) assays revealed significantly higher titers of neutralizing antibodies compared to monovalent HA-only vaccines. Additionally, neuraminidase inhibition (NAI) assays confirmed that the immune system effectively recognized NA, a milestone that has been challenging to achieve in the context of influenza vaccination. The synergy between HA and NA antigens may contribute to a more durable immunity, reducing the frequency and severity of infections during flu season.

The safety analysis encompassed both local and systemic reactions, typical of vaccine studies, recorded in preclinical models. Researchers reported minimal injection site reactions and no systemic toxicity, underscoring the biocompatibility of the LNP-mRNA platform when used for influenza vaccination. These findings not only bolster confidence in the vaccine’s safety but also highlight the potential for this technology to be adapted rapidly to emerging influenza strains or other respiratory pathogens.

From a molecular standpoint, the mRNA constructs were optimized for enhanced stability and translational efficiency. Codon usage was meticulously designed to match human cellular machinery, while untranslated regions (UTRs) were engineered to improve mRNA half-life without triggering excessive innate immune activation, which can interfere with antigen expression. This balance is critical to achieving high protein yield and robust immune priming, a hallmark of successful mRNA vaccines.

Moreover, the vaccine’s ability to induce T-cell responses was thoroughly investigated. CD8+ cytotoxic T lymphocytes (CTLs) play an important role in clearing influenza-infected cells and providing long-term immunity. Flow cytometry and ELISpot assays revealed that vaccinated subjects mounted significant T-cell responses directed against both HA and NA epitopes. This cellular immunity complements the antibody-mediated protection, offering a multi-layered defense against viral infection and possibly contributing to reduced viral replication and transmission.

Another highlight of the study involves the assessment of mucosal immunity, an often-overlooked yet critical component of influenza protection. Secretory IgA antibodies at mucosal surfaces can neutralize viruses at entry points, preventing infection establishment. Preliminary data indicate that the mRNA vaccine may stimulate mucosal immune responses when administered intramuscularly, a finding that warrants further exploration and could have profound implications for vaccine delivery strategies.

One of the paramount challenges in influenza vaccine development is antigenic mismatch; the virus’s high mutation rate often leads to strain variants that escape immunity induced by prior vaccination. The inclusion of neuraminidase antigens might mitigate this issue by presenting conserved regions of the viral NA protein that are less prone to mutation. This potentially broadens the vaccine’s effectiveness against diverse influenza strains and may reduce the necessity for annual reformulation.

The study also addresses manufacturing and scalability considerations inherent in mRNA vaccine technologies. The modular nature of mRNA design allows for rapid adaptation to circulating influenza strains, significantly shortening production timelines compared to traditional egg-based or recombinant protein vaccines. Moreover, the established cold chain logistics and mass production infrastructure developed during the COVID-19 vaccine rollout provide a framework for efficient global distribution of influenza mRNA vaccines.

Looking to the future, experts anticipate that this dual-antigen mRNA vaccine could revolutionize the annual influenza vaccination paradigm, potentially improving global vaccine coverage and efficacy rates. By providing enhanced immunity and a favorable safety profile, this approach aligns with the broader goal of preventing seasonal influenza epidemics and minimizing the burden on healthcare systems worldwide. Ongoing clinical trials are expected to validate these promising preclinical results and bring this transformative vaccine closer to licensure.

The integration of neuraminidase into seasonal influenza vaccines could also influence vaccine policy and public health strategies. Surveillance systems may need to incorporate NA antigenic data to inform vaccine strain selection more comprehensively. Additionally, the enhanced vaccine efficacy might reduce influenza-related hospitalizations and mortalities, contributing to improved population health outcomes, particularly among vulnerable groups such as the elderly and immunocompromised.

This advancement also opens avenues for mRNA vaccine applications beyond influenza. By demonstrating the successful co-expression of multiple antigens and eliciting broad immune responses, the platform can be adapted to complex pathogens requiring multivalent protection. The scientific community anticipates a surge in research leveraging mRNA technology to combat emerging infectious diseases, leveraging lessons learned from this pioneering influenza vaccine study.

Ultimately, the convergence of molecular innovation and immunological insight embodied in this research marks a pivotal step toward more effective, safe, and adaptable vaccines. As global health challenges intensify, such scientific breakthroughs underscore the relentless pursuit required to outpace evolving pathogens and safeguard human health. The study by Rudman Spergel, Lee, Koslovsky, and colleagues ushers in a new era of influenza vaccination that could transform the landscape of infectious disease prevention.

Subject of Research: Immunogenicity and safety evaluation of mRNA-based seasonal influenza vaccines encoding both hemagglutinin and neuraminidase proteins.

Article Title: Immunogenicity and safety of mRNA-based seasonal influenza vaccines encoding hemagglutinin and neuraminidase.

Article References:
Rudman Spergel, A.K., Lee, I.T., Koslovsky, K. et al. Immunogenicity and safety of mRNA-based seasonal influenza vaccines encoding hemagglutinin and neuraminidase. Nat Commun 16, 5933 (2025). https://doi.org/10.1038/s41467-025-60938-4

Image Credits: AI Generated

Central to this innovative vaccine’s success is its ability to precisely incorporate two pivotal viral proteins: hemagglutinin (H5) and neuraminidase (N1). These proteins are integral to the virus’s infectious cycle, with hemagglutinin facilitating viral entry into host cells, while neuraminidase plays a crucial role in the release and spread of new viral particles. Unlike many existing vaccines that primarily target the hemagglutinin protein, this platform explores a bivalent approach, combining immune targets to potentially enhance protection and broaden the vaccine’s efficacy against viral mutations.

The platform leverages recombinant protein technology, eschewing traditional egg-based vaccine production methods. Instead, the H5 and N1 proteins are engineered with a histidine tag—a short amino acid sequence with a natural affinity for metals—that allows them to bind efficiently and specifically to cobalt ions embedded within cobalt-porphyrin-phospholipid (CoPoP) nanoparticles. This nanoparticle scaffold forms the core of the vaccine delivery system, providing a stable and versatile platform that presents antigens in a manner that effectively stimulates the immune system.

Preclinical trials conducted on mice exhibited compelling results: administration of hemagglutinin alone conferred full protection, completely preventing signs of illness, weight reduction, and viral replication within lung tissues. The neuraminidase-only formulation, while providing partial immunity with approximately 70% effectiveness, demonstrated the capacity to reduce viral load and disease severity, underscoring the importance of neuraminidase antibodies in modulating infection. Interestingly, the combination of H5 and N1 as a bivalent vaccine did not surpass the efficacy observed with hemagglutinin alone, suggesting a predominant role for hemagglutinin in protective immunity but reaffirming the supportive benefits of neuraminidase-targeted responses.

The CoPoP nanoparticle’s design not only supports antigen presentation but also incorporates potent adjuvants—including QS-21, a saponin derivative known to enhance cellular and humoral immune responses, and PHAD, a synthetic monophosphoryl lipid A derivative acting as a Toll-like receptor 4 agonist. Both adjuvants are embedded within the phospholipid bilayer shell, amplifying the vaccine’s immunogenicity by promoting a robust and durable immune activation. This molecular synergy enables the platform to elicit broad-spectrum protection with potentially improved durability and response quality compared to conventional vaccines.

What distinctly sets this vaccine platform apart is its manufacturing advantage. Traditional influenza vaccines rely heavily on egg-based propagation of live or attenuated viruses—a time-consuming process susceptible to supply chain constraints. In contrast, the UB strategy produces antigenic proteins through recombinant expression systems, which are then effortlessly conjugated to nanoparticles via rapid and stable metal-affinity interactions. This method promises expedited vaccine production timelines, scalability, and adaptability critical in responding swiftly to emergent virus strains during pandemics or zoonotic spillovers.

The CoPoP nanoparticle technology underlying this vaccine platform is not a nascent concept; it has undergone advanced clinical evaluations in unrelated viral contexts, notably as a COVID-19 vaccine candidate. These phase 2 and 3 trials, conducted in collaboration with industry partners and international research bodies, have demonstrated the platform’s safety and immunogenic profile in humans, bolstering confidence that the technology can be effectively translated into licensed vaccines for other pathogens, including avian influenza.

From a molecular perspective, the strategic use of histidine-tagged antigens exploits the affinity between imidazole side chains of histidine residues and transition metal ions, fostering swift and stable antigen attachment without compromising protein conformation or function. This design ensures that the antigens display native epitopes essential for inducing neutralizing antibodies and T-cell responses, a feat difficult to achieve in many subunit vaccine approaches.

Moreover, the research highlights the nuanced roles of viral glycoproteins in immune defense. Hemagglutinin serves as the viral key for host cell interaction, dictating entry specificity and initial infection, which makes it a prime neutralizing antibody target. Neuraminidase, acting as an enzymatic scissors, cleaves sialic acid residues to facilitate virion release, and while antibodies targeting N1 are non-neutralizing in the classical sense, they reduce viral dissemination and disease severity, contributing to overall vaccine efficacy. This understanding of immunological mechanisms reinforces the rationale for including multiple antigenic components to counteract viral escape mutations.

Looking ahead, the UB team intends to expand their evaluations by experimenting with dosage variations, vaccination schedules, and administration routes to optimize the vaccine’s protective effect and practical deployment. The multi-institution collaboration, spanning public health agencies, national microbiology laboratories, veterinary research centers, and biotech firms, exemplifies the integrative approach necessary to combat complex zoonotic threats effectively.

The promise of this vaccine platform extends beyond avian influenza. Its modular design, speed of production, and potent immune activation could serve as a blueprint for rapid response vaccines against other emerging infectious diseases. In an era marked by the continuous emergence of viral variants with pandemic potential, innovative technologies such as this herald a new paradigm in vaccinology, where precision engineering, nanotechnology, and immunology converge to safeguard both animal and human health.

The research, slated for publication in the prestigious journal Cell Biomaterials, epitomizes cutting-edge advances that could redefine influenza vaccination frameworks and fortify global preparedness against evolving viral pathogens.

Subject of Research: Avian influenza vaccine development targeting H5N1 variant 2.3.4.4b using a cobalt-porphyrin-phospholipid nanoparticle platform.

Article Title: University at Buffalo Develops Novel Nanoparticle Platform Achieving Complete Protection Against Deadly H5N1 Avian Influenza Variant in Mice

News Publication Date: 17-Apr-2025

Image Credits: University at Buffalo

Keywords: Avian influenza, Flu vaccines, Animal research, Influenza viruses, Bond formation, Vaccine development, Wild birds, Public health, COVID 19, Recombinant proteins, Cell division, Animal models