Development of a dengue mRNA vaccine candidate targeting all four serotypes simultaneously through consensus antigen design
Background
Dengue fever is a major mosquito-borne infectious disease that poses a significant global health problem. Dengue virus (DENV) exists in four distinct serotypes (DENV-1 to 4). A medical challenge arises when a patient infected with a specific serotype is exposed to another serotype, which can lead to a rapid worsening of symptoms. This phenomenon, known as antibody-dependent enhancement (ADE), has been a long-standing obstacle in vaccine development. A vaccine design that can equally block all four viruses is required.
The scientific community has identified non-structural protein 1 (NS1), which is released from DENV-infected cells, as a new alternative. This protein promotes vascular leakage in patients, exacerbating symptoms, and also acts as an antigen that stimulates immune cells. Research continues to develop vaccines that incorporate NS1 to prevent severe dengue fever. However, overcoming the genetic variations between serotypes and inducing uniform immunity is not easy.
Key Findings
The researchers performed integrated sequence analysis of the four DENV serotypes to design a single consensus antigen (cNS1). This consensus antigen exhibits 78-89% amino acid sequence similarity to the NS1 proteins of the four serotypes found in nature. The researchers created a vaccine formulation (mRNA-LNP) by incorporating the designed cNS1 sequence into a modified messenger RNA (mRNA) and encapsulating it in lipid nanoparticles (LNP).
Animal experiments were conducted to directly verify the efficacy of the vaccine. When a low dose (0.2 µg) of the cNS1 vaccine was administered to BALB/c mice, a broad immunoglobulin G (IgG) antibody response was observed, recognizing the NS1 protein of all four serotypes. In addition to humoral immunity, cellular immune responses were also induced. This was confirmed by the presence of T cell immune responses that produce interferon-gamma (IFN-γ) in response to peptides derived from multiple DENV serotypes.
However, some trade-offs were revealed in the process of achieving a broad immune response. While the ability to recognize all four serotypes was achieved, the production of serotype-specific antibodies was somewhat reduced compared to when only a single serotype was targeted. This is a common challenge encountered when developing multivalent vaccines.
Significance and Prospects
This study demonstrates the potential of a single antigen design to simultaneously inhibit multiple variants of DENV. Existing dengue vaccines mainly target envelope proteins. This approach carries the risk of adverse effects due to incomplete antibody formation, which can worsen infection. In contrast, targeting the NS1 protein released from infected cells can easily avoid these concerns.
Ultimately, the cNS1 antigen designed in this study is expected to be used as an adjuvant component of next-generation dengue vaccines. When administered together with an envelope protein-based vaccine, it can simultaneously activate antibody responses and cellular immunity, enhancing protective efficacy. Due to the characteristics of mRNA technology, which allows for rapid adjustment of gene sequences, it also has advantages in establishing a large-scale production system.
However, several obstacles must be overcome before the vaccine can be commercialized. This study is in the basic research stage and uses only a mouse model. A challenge experiment is also essential to verify whether the vaccinated animals can defend against actual viral infection. Furthermore, further research on formulations is needed to compensate for the relatively low induction of antibodies targeting specific serotypes.
Dengue virus (DENV) remains a major global health burden, with four antigenically distinct serotypes (DENV-1-4) posing a significant challenge for vaccine development. Dengue non-structural protein 1 (NS1) has been associated with additional protection and reduced disease severity, supporting its inclusion in vaccine design. In this study, we designed a consensus NS1 (cNS1) antigen by integrating sequence elements from all four DENV serotypes (78-89% amino acid identity) to enhance cross-serotype antigenic coverage. The cNS1 sequence was encoded as a nucleoside-modified mRNA and formulated in lipid nanoparticles (mRNA-LNPs). Immunization of BALB/c mice with a low dose (0.2 µg) of cNS1 mRNA-LNP induced broadly reactive NS1-specific IgG responses that recognized NS1 proteins from all four serotypes. In addition, the vaccine elicited interferon-γ (IFN-γ)-producing T cell responses against peptide pools derived from multiple DENV serotypes, indicating the activation of cross-reactive cellular immunity. While broad immune recognition was achieved, this was accompanied by lower serotype-specific response magnitudes as a trade-off. In conclusion, the cNS1 mRNA vaccine induces cross-serotype humoral and cellular immune responses in mice, highlighting the potential of consensus antigen design to broaden immune recognition of DENV NS1. These findings support the further development of NS1-based immunogens as complementary components of next-generation dengue vaccines aimed at achieving broad and effective protection.
The consensus antigen-based mRNA vaccine technology has the potential to diversify the design approaches in the vaccine development industry. Specifically, it can be immediately introduced into a combination therapy to overcome the incomplete protective efficacy of existing dengue vaccines. For example, a scenario in which the commercially available existing multivalent vaccine formulation and this cNS1 vaccine are administered in combination to maximize preventive efficacy and block severe progression is representative. From the perspective of vaccine manufacturers, producing a raw material that reacts to all four serotypes with only one mRNA synthesis process provides the benefits of shortening the manufacturing process and reducing costs. There is also ample room to expand this consensus sequence model to other infectious disease vaccines with diverse variants, such as dengue virus, to significantly shorten the commercialization period of multivalent vaccines.