Colorectal cancer (CRC) is one of the leading causes of cancer-related mortality worldwide. In the Unites States, an estimated 151,300 Americans will be diagnosed with CRC and over 52,580 are expected to die from the disease in 2022 alone (https://seer.cancer.gov/statfacts/html/colorect.html). While the five-year survival rate for localized CRC is excellent at 90%, more than half of new CRC cases have the disease spread to regional lymph nodes and/or distant organs at the time of diagnosis. CRC with distant metastasis has a dismal five-year survival rate of 14.7%. These data clearly indicate that CRC-related mortality can be significantly improved if the disease is detected early and proper interventions could be deployed. Because CRC typically originates from precancerous colorectal polyps, routine colonoscopy screening provides an excellent opportunity to detect precursor or early lesions and reduce CRC-related morbidity and mortality. Indeed, the US Preventive Services Task Force recently updated its recommendation on CRC screening, noting the evidence that the screening in average-risk asymptomatic adults aged 50 to 75 years is of substantial benefit. Risk factors for CRC include age (>50), race (African American), obesity, cigarette smoking, type II diabetes, history of inflammatory bowel diseases, family history of colorectal polyps or CRC, and inherited genetic syndromes known to increase the CRC risks, such as familial adenomatous polyposis (FAP) and Lynch syndrome. FAP and Lynch syndrome are caused by germline mutations in the APC gene and DNA mismatch repair genes, respectively. The management of individuals with hereditary gastrointestinal cancer syndromes requires additional measures beyond what is recommended for the average-risk population to minimize the overall risk of cancer-associated morbidity and mortality. Management options for the confirmed mutation carriers include multiple aggressive screening, chemopreventive strategies, and prophylactic surgery. However, these interventions are associated with various degrees of adverse effects. Safer and more effective preventive measures are urgently needed for the individuals with FAP, Lynch syndrome, and other hereditary gastrointestinal cancer syndromes. Fusobacteria are common human oral gram-negative anaerobic microflora isolated from dental plaque and gum diseases, but rarely detectable in the colorectum of healthy individuals. In recent years, the enrichment of a specific pathotype, Fusobacterium nucleatum (Fn), has been demonstrated in the colonic tissues and stools from patients with colorectal adenomas and CRC. Clinical evidence suggests that the prevalence of Fn progressively increases from dysplasia, adenomas to CRC and the higher amount of Fn is significantly associated with CRC with high microsatellite instability, which is caused by DNA MMR deficiencies as seen in Lynch syndrome-associated CRC. The potential association of Fn with CRC tumorigenesis has been examined in a mouse model of FAP. ApcMin/+ mice, which carry a nonsense mutation at codon 850 of the Apc gene, had a significantly accelerated onset and increased multiplicity of both small intestinal and colorectal tumors after oral inoculation of Fn. These data strongly suggested the tumor-promoting role of Fn in ApcMin/+ mice. Interestingly, Fn did not induce colitis in these animals, in contrast to enterotoxigenic Bacteroides fragilis, which has been shown to cause colitis and accelerate tumorigenesis in ApcMin/+ mice. It has also been demonstrated that Fn promotes CRC, breast, and cervical cancer metastasis and can metastasizes with tumor cells. Although how Fn contributes to CRC tumorigenesis has yet to be fully elucidated, emerging evidence points to its virulence factors, such as FadA and Fap2, as potential enhancers of CRC tumorigenesis and progression. The Fap2 has been shown to bind to human T-cell immunoglobulin ITIM domain (TIGIT), an immunoglobulin superfamily receptor known to function as an immune co-inhibitory molecule. Fap2-binding to TIGIT on NK and other T cells protects tumor cells from NK cell-mediated cytotoxicity and blocks effector T cell functions in the tumor microenvironment. TIGIT has also been shown to promote Treg function. Taken together, Fn may exert tumor promoting effects not only by promoting CRC tumor growth, but also by exploiting the immune-suppressive function of TIGIT via its virulence factor protein and contributing to tumor immune evasion mechanisms. Cancers caused by infectious agents are theoretically preventable, if one can prevent the infection, eradicate oncogenic pathogens before tumor development, or suppress the functions of oncogenic molecules. Prophylactic vaccines for human papillomavirus and hepatitis B virus have been associated with significant reductions in infection rates, which are expected to result in the dramatic decrease in the incidence of cervical cancers and hepatocellular carcinoma, respectively. Compared to the prevention of infection, the eradication of oncogenic infectious agents already colonized in the host is in general highly challenging, if not impossible. For example, the well-established eradication regimens for Helicobacter pylori, which increases the risk of noncardia gastric cancers, do not eradicate the bacteria in all cases. Rather, emerging resistance to multiple antibiotics appears to be contributing to the recent decline in the eradication rate. Alternatively, the host immune defense system may be fortified by pathogen-targeted vaccines, if they can boost anti-pathogen immunity and lead to the containment of infection or suppression of pathogen-mediated tumorigenic functions. Fn is a gram-negative anaerobic bacillus, and can be isolated from 60-70% of children aged 5-7 years. As with other gram-negative bacteria, Fn produces outer membrane vesicles (OMVs), which contain much of the biological content of the Fn, but without replicative capacity and some of the soluble proteins found in OMVs may elicit anti-Fn immunity. As part of the PREVENT project to develop Fn OMV based anti-Fn vaccine (https://reporter.nih.gov/project-details/9358850), the proteomic characterization of Fn OMV led to the identification of putative immunogenic components, some of which may be useful as anti-Fn vaccine antigens. Lipid nanoparticle (LNP)-encapsulated mRNA vaccines against COVID-19 revolutionized the implementation of mRNA-based vaccinology. In addition to modifications of mRNA such as with pseudouridine incorporation to reduce innate immune responses and mRNA purification methodologies to remove contaminants, the development of biocompatible LNPs significantly boosted the advancement of COVID and other mRNA-based vaccines. LNP-RNA vaccine platform offers several advantages over conventional protein-based vaccination, including a rapid development, refined adjustment of antigenic epitopes, easier scale-up and timely deployment. The the current study aims to develop and evaluate the immunogenicity of soluble protein-based and LNP-RNA-based Fn vaccines and to determine anti-Fn activity and immunopreventive efficacy of Fn-associated CRC, using mouse models of FAP and Lynch syndrome.