## 2 Tumor Neoantigen Vaccines
### RNA/DNA-Based Neoantigen Vaccines  
RNA and DNA vaccines are all genetic vaccines based on exogenous gene replication coding information such as TSA or TAA on the surface of the tumor in the individual body to activate the immune response. As a critical research neighborhood in recent years, nucleic acid vaccines' design and synthesis methods are convenient and highly safe.  
The first successful mRNA transfection followed the discovery of mRNA transfection by [PERSON] in 1987 in frog embryos in vivo and the suggestion that \"RNA could be used as a form of medicine\" [31]. The advantages of RNA vaccines are that they do not insert into the host genome [32], avoid potential safety issues and allow for targeting multiple targets [33], have intrinsic adjuvant properties [34], and only need to be presented to the immune system through entry into the host cytoplasm, where their translational mechanisms are utilized to produce sufficient antigens. [PERSON] et al. utilized mRNA vaccines to treat pancreatic ductal adenocarcinoma (PDAC), inducing neoantigen-specific CD8\({}^{+}\) T cells in eight patients, and expanding more specific T cells with boosters resulted in a longer median recurrence-free survival (at 18-month median follow-up) [35]. Over the last decade, there has also been some progress in investigating neoantigen-based RNA vaccines to treat gastrointestinal cancers [36], renal cancers [37], hepatocellular carcinomas [38], melanomas [39], and lung cancers [40].  
To solve the problem of easy degradation and expression of RNA, RNA structure can be modified, such as through codon optimization [41], nucleotide modification [42], appropriate modification of structural elements (UTR's, 5' capping, ORF, Poly(A) tail) [43], or piggybacking with liposomes [44], nanosheets [45], and so on.  
Unlike RNA vaccines, DNA vaccines must cross cellular and nuclear membrane barriers to enter the nucleus to be effective, and when delivered with the aid of electroporation, they are capable of generating high MHC class I affinity, driving CD8\({}^{+}\) T cell immunity, and effectively generating antitumor effects [46]. Combining immunosuppressive agents can improve the DNA vaccine effects, and neoantigen DNA vaccines utilize erythrocyte capture to target the spleen and inhibit the growth of hepatocellular carcinoma. The antitumor efficacy was increased even further when combined with anti-PD-1 inhibitors, resulting in a 75% regression of subcutaneous tumors and a complete regression of in situ tumors, prolonging survival [47].  
For the integration of multiple antigens, DNA vaccines are an efficient platform. [PERSON] et al. developed and optimized a DNA vaccine that targets multiple neoantigens in the E0771 and 4T1 models of mammary carcinoma in mice, as predicted by genome sequencing and computational methods. Most neoantigen-specific T cell responses could be induced after vaccination. Sustained immune responses were also achieved during vaccination with the anti-PD-L1 combination. Excellent results have also been shown in pancreatic cancer models [48].  
There are several limitations to the development of nucleic vaccines: naked mRNA is degraded and inactivated by extracellular enzymes [49], inappropriate modification of RNA may reduce the effectiveness of the immune response [39], immunogenicity limits the applications of DNA vaccines, and there is a risk when integrating the DNA strand into the host gene. Other side effects include headache, fever, and pain or swelling at the injection site [50].