Multigenic single-chain mRNA vaccine provides full protection against Dabie bandavirus infection

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Dabie bandavirus (DBV) represents an emerging public health threat for which no licensed vaccines currently exist, underscoring an urgent need for effective countermeasures.¹ In a recent study published in Molecular Therapy Nucleic Acids, Li and colleagues report the development of a novel single-chain mRNA vaccine that simultaneously encodes the DBV glycoprotein precursor (GPC) and nucleoprotein (NP), delivered via lipid nanoparticles (LNPs).¹ The vaccine elicits robust humoral and cellular immune responses and confers complete protection against lethal viral challenge in mice, with no detectable viral loads in major organs (Figure 1). These findings establish a strong preclinical rationale for multigenic mRNA vaccine strategies against DBV, while also raising important questions regarding durability of protection, translational relevance across viral genotypes, and long-term safety.

Figure 1.

Schematic representation of a single-chain mRNA vaccine encoding the glycoprotein GPC and nucleoprotein NP of DBV (GFN-mRNA), encapsulated in lipid nanoparticles (GFN-LNPs)

Following administration, the vaccine induces humoral and cellular immune responses, resulting in complete protection and enhanced survival in a lethal mouse model of DBV infection.

DBV is a highly pathogenic tick-borne virus associated with severe febrile illness and significant mortality.¹ Despite increasing recognition of its clinical burden, vaccine development has lagged, with most prior efforts focusing narrowly on viral surface glycoproteins.^2,3 While glycoproteins such as Gn and Gc are well-established targets of neutralizing antibodies, growing evidence suggests that protective immunity against complex viral pathogens often requires coordinated humoral and cellular immune responses.^3,4 This has fueled interest in vaccine designs that incorporate multiple antigens to broaden immune coverage and enhance protective efficacy.

Within this context, Li et al. engineered a single-chain mRNA construct encoding both DBV GPC and NP, linked via a flexible (G₄S₁)₃ peptide linker and encapsulated in LNPs (GFN-LNP). This design enables coordinated intracellular expression of both antigens from a single transcript, potentially ensuring balanced antigen availability and synchronized immune priming. The immunogenicity and protective efficacy of GFN-LNP were directly compared with three control formulations: GPC-LNP alone, NP-LNP alone, and a physical mixture of the two single-antigen vaccines. NP is a highly conserved viral structural protein that polymerizes into oligomeric complexes and binds viral RNA to form ribonucleoprotein particles, protecting the genome from degradation. Importantly, NP is also a potent inducer of T cell-mediated immunity, particularly CD8⁺ T cell responses, which play a critical role in viral clearance and disease control. By combining GPC-driven neutralizing antibody responses with NP-driven cellular immunity, the authors aim to overcome the limitations of monovalent vaccine approaches.

In mouse immunization studies, both GFN-LNP and GPC-LNP induced strong antigen-specific antibody responses and activated CD4⁺ and CD8⁺ T cells. Notably, immune enhancement did not follow a strictly uniform pattern: in some assays, single-antigen formulations elicited higher cytokine production or IgG subclass responses than the dual-antigen construct. These findings highlight the complexity of immune modulation by multigenic vaccines and suggest that qualitative differences in immune responses may be as important as magnitude alone. Protective efficacy was evaluated using a lethal DBV challenge in A129 mice, a commonly employed interferon receptor-deficient model. Strikingly, animals vaccinated with GFN-LNP, GPC-LNP, or the antigen mix exhibited complete protection, with no weight loss, mortality, or detectable viral RNA in major organs. Histopathological analysis further revealed an absence of pathological alterations in vaccinated animals, supporting the functional relevance of the induced immune responses. Together, these data demonstrate that simultaneous expression of GPC and NP within a single mRNA molecule can generate a broad and effective immune response, potentially producing synergistic protection that exceeds what might be expected from individual antigens alone. Importantly, the single-chain design may also reduce manufacturing complexity and cost compared with multicomponent vaccine formulations.

The findings reported by Li et al. align with prior studies demonstrating the value of multigenic mRNA vaccines. For example, earlier work showed that a single-chain mRNA encoding both Spike and NP antigens of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enhanced CD8⁺ T cell-mediated protection,⁵ while a trivalent mRNA vaccine against mpox virus provided complete protection in mice.⁶ Collectively, these studies reinforce the concept that integrating multiple antigenic targets into a single mRNA construct can expand the immune response.

An additional strength of the present work lies in its consideration of DBV genetic diversity. DBV circulates as at least six genotypes (A–F), raising concerns about strain-specific immunity. Sequence analyses presented by the authors demonstrate high conservation of both GPC and NP across all known genotypes. Although direct cross-protection studies were not performed, these conservation patterns strongly suggest that the GFN-LNP vaccine could provide broad protection against diverse circulating DBV strains. The use of flexible (G₄S₁)₃ linkers represents another crucial element of the vaccine design. Such linkers are commonly employed to preserve independent folding and epitope exposure of fused proteins. In this context, the linker likely facilitates proper antigen presentation and may enhance immunogenicity.

Despite its strengths, the study has limitations that warrant consideration. First, the durability of the immune response was assessed only over a short time frame. Establishing whether the vaccine induces long-lasting protective immunity is critical for evaluating its clinical viability. Second, the A129 mouse model, while useful for initial efficacy testing, has inherent immunological deficiencies that may limit extrapolation to immunocompetent hosts. Third, the protective efficacy of a single-dose regimen remains unknown, as the current study employed a prime-boost strategy. Additional mechanistic studies are also needed to clarify how NP-specific immune responses contribute to protection and how antigen fusion influences memory formation.

In conclusion, Li et al. present a compelling preclinical demonstration of a dual-antigen, single-chain mRNA vaccine against DBV that achieves complete protection in lethal challenge models. This work highlights the continued evolution of mRNA vaccine technology and provides a strong rationale for multigenic vaccine strategies targeting emerging viral threats. More broadly, it illustrates how adaptable mRNA platforms, validated during the coronavirus disease 2019 (COVID-19) pandemic, can be rapidly repurposed to address neglected or newly emerging pathogens, strengthening global preparedness against high-impact infectious diseases.

Declaration of interests

The authors declare no competing interests.