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Epstein–Barr virus (EBV) was discovered in 1964 in the cell line of Burkitt lymphoma and became first known human oncogenic virus. EBV belongs to the Herpesviridae family, and is present worldwide as it infects 95% of people. Infection with EBV usually happens during childhood when it remains asymptomatic; however, in adults, it can cause an acute infection known as infectious mononucleosis. In addition, EBV can cause wide range of tumors with origins in B lymphocytes, T lymphocytes, and NK cells. Its oncogenicity and wide distribution indicated the need for vaccine development. Research on mice and cultured cells as well as human clinical trials have been in progress for a few decades for both prophylactic and therapeutic EBV vaccines. The main targets of the vaccines are EBV envelope glycoproteins such as gp350 and EBV latent genes. The long wait for the EBV vaccine is due to the complexity of the EBV replication cycle and the wide range of its host cells. Although some strategies such as the use of dendritic cells and recombinant Vaccinia viral vectors have shown success, ongoing clinical trials using mRNA-based vaccines as well as new delivery systems as nanoparticles are yet to show the best choice of vaccine target and its production strategy.

Nasopharyngeal carcinoma (NPC) is a serious and highly invasive epithelial malignancy that is closely associated with Epstein—Barr virus (EBV). Due to the lack of therapeutic vaccines for NPC, we selected EBV latent membrane protein 2 (LMP2) as a preferable targeting antigen to develop a lipid-based LMP2-mRNA (mLMP2) vaccine. Full-length mLMP2 expressing LMP2 was first synthesized using an in vitro transcription method and then encapsulated into (2,3-dioleacyl propyl) trimethylammonium chloride (DOTAP)-based cationic liposomes to obtain the mRNA vaccine (LPX-mLMP2). The cell assays showed that the antigen-presenting cells were capable of highly efficient uptake of LPX-mLMP2 and expression of LMP2. LMP2 could subsequently be presented to form the peptide-major histocompatibility complex (pMHC). Furthermore, LPX-mLMP2 could accumulate in the spleen, express antigens, promote the maturation of dendritic cells and stimulate antigen-specific T-cell responses in vivo. It dramatically inhibited the tumor growth of the LMP2-expressing tumor model after three doses of vaccination. Additionally, the proliferation of antigen-specific T cells in the tumor site made a good sign for the promise of mRNA vaccines in virus-induced cancer. Overall, we provided a newly developed antigen-encoding mRNA vaccine with advantages against NPC. We also demonstrated that mRNA vaccines are attractive candidates for cancer immunotherapy.

Background Targeting EBV-proteins with mRNA vaccines is a promising way to treat EBV-related tumors like nasopharyngeal carcinoma (NPC). We assume that it may sensitize tumors to immune checkpoint inhibitors. Results We developed an LMP2-mRNA lipid nanoparticle (C2@mLMP2) that can be delivered to tumor-draining lymph nodes. C2@mLMP2 exhibited high transfection efficiency and lysosomal escape ability and induced an increased proportion of CD8 + central memory T cells and CD8 + effective memory T cells in the spleen of the mice model. A strong synergistic anti-tumor effect of C2@mLMP2 in combination with αPD-1 was observed in tumor-bearing mice. The mechanism was identified to be associated with a reverse of CD8 + T cell exhaustion in the tumor microenvironment. The pathological analysis further proved the safety of the vaccine and the combined therapy. Conclusions This is the first study proving the synergistic effect of the EBV-mRNA vaccine and PD-1 inhibitors for EBV-related tumors. This study provides theoretical evidence for further clinical trials that may expand the application scenario and efficacy of immunotherapy in NPC. Graphical Abstract

Epstein‐Barr virus (EBV) is associated with various malignancies and infects >90% of the global population. EBV latent proteins are expressed in numerous EBV‐associated cancers and contribute to carcinogenesis, making them critical therapeutic targets for these cancers. Thus, this study aims to develop mRNA‐based therapeutic vaccines that express the T‐cell‐epitope‐rich domain of truncated latent proteins of EBV, including truncatedlatent membrane protein 2A (Trunc‐LMP2A), truncated EBV nuclear antigen 1 (Trunc‐EBNA1), and Trunc‐EBNA3A. The vaccines effectively activate both cellular and humoral immunity in mice and show promising results in suppressing tumor progression and improving survival time in tumor‐bearing mice. Furthermore, it is observed that the truncated forms of the antigens, Trunc‐LMP2A, Trunc‐EBNA1, and Trunc‐EBNA3A, are more effective than full‐length antigens in activating antigen‐specific immune responses. In summary, the findings demonstrate the effectiveness of mRNA‐based therapeutic vaccines targeting the T‐cell‐epitope‐rich domain of EBV latent proteins and providing new treatment options for EBV‐associated cancers. mRNA‐based vaccines expressing truncated Epstein‐Barr virus (EBV) latent protein domains effectively elicit cellular and humoral immunity, inhibit tumor progression, and improve the survival of tumor‐bearing mice. Truncated antigens show superior immune activation compared to full‐length antigens, offering promising therapeutic options for EBV‐related malignancies.