We have recently described SARS-COV-2 antigens showing sequence and conformational homology to tumor associated antigens (TAAs). Moreover, cross-reactive T cells have been identified in individuals either infected by the SARS-CoV-2 virus or vaccinated with the BNT162b2 preventive vaccine. In the present study, we analyzed the specific cross-binding TCRs by single cell RNA TCR sequencing. The paired SARS-CoV-2 epitope LLLDDFVEI (VIR) and the PRDX5 tumor associated antigen LLLDDLLVS (TAA) were selected to elicit cross-reacting T cells ex vivo . PBMCs from 5 healthy individuals were cultured for 10 days with 10 ug every 3 days of one of the two peptides and cells were selected for single cell RNA TCR sequencing. Results in CD8 + T Effector cells (T TE ) showed the amplification or the de novo identification of a handful number of TRAV/TRBV genes and of CDR3αβ motifs upon treatment ex vivo with both epitopes, which are specific for each subject in the analysis. The very same clonotypes were identified also in the CD8 + T proliferating subset, confirming that both epitopes induced a highly activated and plastic state. Conformational prediction analyses of pMHC-TCR complexes showed perfect structural overlap, supporting the functional cross-reaction of CD8+ T cells with both the viral and the tumor antigens. Our results describe for the first time the TCR CDR3αβ motifs amplified or de novo expanded by induction with a viral antigen showing a molecular mimicry with a tumor antigen. They are strictly individual and do not match with any motif in the publicly available TCR repository. However, considering the significant degeneracy in the TCR binding to the same epitope, the finding of identical TCR CDR3αβ motifs elicited by two homologous epitopes is of the highest functional relevance. Such results provide a clear experimental validation proof that microbial epitopes mimicking TAAs can be used to develop off-the-shelf preventive/therapeutic vaccine formulations. Indeed, such non-self antigens are much stronger immunogens and may elicit a potent cross-reacting anti-cancer T cell response.

Lifelong microbial exposure progressively shapes antiviral antibody repertoires, yet whether their global organization follows distinct trajectories during physiological ageing and cancer remains unknown. Here, we used high-throughput VirScan serological profiling to compare antiviral antibody repertoires from healthy adult women, exceptionally healthy elderly women and patients with breast cancer, aiming to distinguish physiological immune remodeling from tumor-associated immune reorganization. Physiological ageing was characterized by a coordinated expansion of repertoire breadth and microbial richness, reflecting progressive diversification of antiviral immune memory accumulated throughout life. In contrast, breast cancer was not associated with comparable repertoire expansion but with increased antibody reactivity and selective redistribution of pre-existing antiviral responses. Although only a limited number of peptide-specific differences distinguished breast cancer from age-matched controls, these converged into coordinated microbial signatures involving multiple viral species, predominantly members of the Herpesviridae family. Global repertoire analyses further demonstrated that ageing and breast cancer are associated with distinct patterns of serological organization rather than discrete antiviral signatures, indicating alternative modes of adaptive immune remodeling. Together, these findings identify lifelong antiviral antibody repertoires as systems-level descriptors of immune organization and show that physiological ageing and breast cancer follow distinct trajectories of adaptive immune remodeling. Our study provides a framework for interpreting large-scale serological repertoires as integrated biomarkers of systemic immune state rather than collections of independent pathogen-specific antibody responses.

We have recently described SARS-COV-2 antigens showing sequence and conformational homology to tumor associated antigens (TAAs). Moreover, cross-reactive T cells have been identified in individuals either infected by the SARS-CoV-2 virus or vaccinated with the BNT162b2 preventive vaccine. In the present study, we analyzed the specific cross-binding TCRs by single cell RNA TCR sequencing. The paired SARS-CoV-2 epitope LLLDDFVEI (VIR) and the PRDX5 tumor associated antigen LLLDDLLVS (TAA) were selected to elicit cross-reacting T cells ex vivo. PBMCs from 5 healthy individuals were cultured for 10 days with 10 ug every 3 days of one of the two peptides and cells were selected for single cell RNA TCR sequencing. Results in CD8+ T Effector cells (TTE) showed the amplification or the de novo identification of a handful number of TRAV/TRBV genes and of CDR3αβ motifs upon treatment ex vivo with both epitopes, which are specific for each subject in the analysis. The very same clonotypes were identified also in the CD8+ T proliferating subset, confirming that both epitopes induced a highly activated and plastic state. Conformational prediction analyses of pMHC-TCR complexes showed perfect structural overlap, suggesting the functional cross-reaction of CD8 + T cells with both the viral and the tumor antigens. Our results describe for the first time the TCR CDR3αβ motifs amplified or de novo expanded by induction with a viral antigen showing a molecular mimicry with a tumor antigen. They are strictly individual and do not match with any motif in the publicly available TCR repository. However, considering the significant degeneracy in the TCR binding to the same epitope, the finding of identical TCR CDR3αβ motifs elicited by two homologous epitopes is of the highest functional relevance. Such results provide a clear experimental validation proof that microbial epitopes mimicking TAAs can be used to develop off-the-shelf preventive/therapeutic vaccine formulations. Indeed, such non-self antigens are much stronger immunogens and may elicit a potent cross-reacting anti-cancer T cell response.

The human public T-cell receptor (TCR) repertoire provides a shared immunological framework across individuals, yet whether it possesses a conserved higher-order structural organization and how this organization is affected by lifelong immune ageing remain unknown. Here, we constructed a structural atlas of the human public TCRβ repertoire from 1.33 million unique public CDR3β sequences derived from healthy Adults (<70 years) and Elders (>80 years). The atlas comprised 64 reproducible Structural Sequence Modules (SSMs) representing sequence-coherent neighborhoods supported by quantitative model selection and independent topological validation. Projection of individual repertoires onto this common framework demonstrated complete preservation of all SSMs across both cohorts. Although 18 modules exhibited significant differences in unweighted occupancy, the global module hierarchy remained highly conserved, indicating that exceptional longevity is associated primarily with quantitative redistribution among pre-existing structural compartments rather than loss or replacement of repertoire organization. Rarefaction analysis demonstrated that unequal cohort size strongly influenced public-clonotype discovery but had minimal impact on the direction and magnitude of module-level occupancy differences, whereas frequency-weighted analysis indicated that remodeling was not primarily driven by expansion of highly abundant public clonotypes. Susceptibility to remodeling was associated mainly with module size and within-module CDR3β length variability. Module publicness was highly conserved across age groups and associated with coordinated sequence, germline and network properties, while TRBJ usage was substantially more strongly associated with SSM identity than TRBV usage. Finally, curated antigen annotations were non-randomly distributed across SSMs, demonstrating module-level functional biases, although structural proximity did not generally predict similarity in antigen-recognition profiles. Together, these findings identify higher-order structural organization as a robust property of the human public TCRβ repertoire. Exceptional longevity preserves this organization while selectively remodeling the occupancy of pre-existing Structural Sequence Modules, distinguishing age-associated quantitative redistribution from cohort-size effects and clonal expansion. The structural atlas therefore provides a reproducible framework for investigating the organization and remodeling of adaptive immune repertoires across ageing and immune-mediated conditions.

Shared tumor antigens are needed for developing off-the-shelf preventive/therapeutic cancer vaccines. To this aim, shared mutated neoantigens (TSAs) cannot be exploited for highly prevalent tumors in the majority of worldwide cancer patients. Therefore, TAAs must be used, which may suffer from the potential immunological tolerance. Analogue peptides with improved antigenicity and immunogenicity, able to elicit a cross-reactive T cell response are needed. To this aim, non-self-antigens derived from microorganisms (MoAs) may be of great benefit. We will describe several examples of MoAs sharing sequence homology with TAAs (“molecular mimicry”), able to elicit a cross-reacting CD8+ T cell response. In particular, the homology to cancer testis TAA (e.g. MAGE-A1) allows to develop cancer vaccines useful for several tumor types, “one-vaccine-for-many-tumors”. In conclusion, non-self MoAs should be selected and included in preventive/therapeutic cancer vaccines with a more potent anti-tumor efficacy compared to those based on TAAs. This would allow the development of ready to be used “off-the-shelf” cancer vaccines for the global population of patients affected by one or more cancer types (Tagliamonte M, et al., Molecular mimicry and cancer vaccine development. Mol Cancer. 2023 Apr 26;22(1):75. doi: 10.1186/s12943-023-01776-0). Maria Tagliamonte, Beatrice Cavalluzzo, Angela Mauriello, Concetta Ragone, Biancamaria Cembrola, Simona Mangano, Luigi Buonaguro. Exploiting the molecular mimicry for preventive/therapeutic cancer vaccine development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 856.

We have previously reported that microorganism-associated antigens (MAAs) share high sequence and conformational homology with tumor-associated antigens (TAAs) as well as T cells cross-react with homologous MAA/TAA pairs. More recently, we have also shown that the SARS-CoV-2 preventive vaccine, besides the humoral response, is able to elicit also a T cell response which cross-react with homologous TAAs. In the present study we analyzed the mandatory pediatric vaccines, namely the hexavalent vaccine (Diphtheria, Tetanus, Pertussis (whooping cough), Polio, Haemophilus influenzae type b (Hib), Hepatitis B) and the MMR (measles, mumps and rubella), and the chickenpox vaccine. MHC class I epitopes (9 mers) from each of these vaccines were predicted for the most frequent 12 HLA A and B alleles. Overall, 3177 strong binders (SBs) were identified and the most frequently associated allele is the HLA-A*02:01. Of these, 397 are predicted for the hexavalent vaccine and 571 in the MMR vaccine. A molecular mimicry with 59 SBs derived from cellular proteins has been identified and 13 of these proteins are significantly overexpressed in several human cancers. All these results strongly suggest that the mandatory pediatric vaccinations may potentially elicit a CD8+ T cell response against several microbial epitopes in individuals with different genetic background. Such microbial epitopes show high homology with epitopes from cellular proteins overexpressed in multiple cancer types. Therefore, a potential anti-microbial CD8+ T cell response may cross-react against cancer cells. This would imply that the pediatric vaccinations may be a preventive measure against both microbial infections and a broad spectrum of tumors. A large-scale immune-epidemiological study will be needed to confirm the proposed suggestive results.

We have recently described that the most prevalent 100 mutations identified in human cancers, both single nucleotide variations (SNVs) and InDels, generate a handful number of shared mutated neoantigens (SNV and InDel-NeoAgs) in association with 5 HLA-A and 7 B haplotypes. In the present study, we expanded such analysis to 50 haplotypes in the three MHC class I loci (10 HLA-A, 27 HLA-B and 13 HLA-C), including all the mutated proteins identified in at least 5

Abstract The entire SARS-CoV-2 proteome was scanned to predict potential T cell antigens linked to HLA-A*02:01 and homology to TAAs (tumor-associated antigens) was searched by BLAST. Viral epitopes with high affinity (<100nM) to the HLA-A*02:01 allele were predicted. Shared and variant-specific epitopes were identified. Significant homologies in amino acidic sequence have been found between SARS-CoV-2 peptides and multiple TAAs, mainly associated with breast, liver, melanoma and colon cancers. The molecular mimicry of the viral epitopes and the TAAs was found in all viral proteins, mostly the Orf 1ab and the Spike, which is included in the BNT162b2 vaccine. Predicted structural similarities confirmed the sequence homology and comparable patterns of contact with both HLA and TCR α and β chains were observed. CD8+ T cell clones cross-reactive with the paired peptides have been found by MHC class l-dextramer staining. Our results show for the first time that several SARS-COV-2 antigens are highly homologous to TAAs and cross-reactive T cells are identified in infected and BNT162b2 preventive vaccinated individuals. The implication would be that the SARS-Cov-2 pandemic could represent a natural preventive immunization for breast, liver, melanoma and colon cancers. In the coming years, real-world evidences will provide the final proof for such immunological experimental evidence. Moreover, such SARS-CoV-2 epitopes can be used to develop “multi-cancer” off-the-shelf preventive/therapeutic vaccine formulations, with higher antigenicity and immunogenicity than over-expressed tumor self-antigens, for the potential valuable benefit of thousands of cancer patients around the World. Ragone et al., Front. Immunol. 15:1398002 Citation Format: Concetta Ragone, Angela Mauriello, Beatrice Cavalluzzo, Ernesta Cavalcanti, Luigi Russo, Simona Mangano, Biancamaria Cembrola, Maria Tagliamonte, Luigi Buonaguro. Molecular mimicry of SARS-COV-2 antigens with tumor associated antigens [abstract]. In: Proceedings of the AACR IO Conference: Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2025 Feb 23-26; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2025;13(2 Suppl):Abstract nr B124.

Background We have recently shown extensive sequence and conformational homology between tumor-associated antigens (TAAs) and antigens derived from microorganisms (MoAs). The present study aimed to assess the breadth of T-cell recognition specific to MoAs and the corresponding TAAs in healthy subjects (HS) and patients with cancer (CP). Method A library of > 100 peptide-MHC (pMHC) combinations was used to generate DNA-barcode labelled multimers. Homologous peptides were selected from the Cancer Antigenic Peptide Database, as well as Bacteroidetes/Firmicutes-derived peptides. They were incubated with CD8 + T cells from the peripheral blood of HLA-A*02:01 healthy individuals ( n = 10) and cancer patients ( n = 16). T cell recognition was identified using tetramer-staining analysis. Cytotoxicity assay was performed using as target cells TAP-deficient T2 cells loaded with MoA or the paired TuA. Results A total of 66 unique pMHC recognized by CD8+ T cells across all groups were identified. Of these, 21 epitopes from microbiota were identified as novel immunological targets. Reactivity against selected TAAs was observed for both HS and CP. pMHC tetramer staining confirmed CD8+ T cell populations cross-reacting with CTA SSX2 and paired microbiota epitopes. Moreover, PBMCs activated with the MoA where shown to release IFNγ as well as to exert cytotoxic activity against cells presenting the paired TuA. Conclusions Several predicted microbiota-derived MoAs are recognized by T cells in HS and CP. Reactivity against TAAs was observed also in HS, primed by the homologous bacterial antigens. CD8+ T cells cross-reacting with MAGE-A1 and paired microbiota epitopes were identified in three subjects. Therefore, the microbiota can elicit an extensive repertoire of natural memory T cells to TAAs, possibly able to control tumor growth (“natural anti-cancer vaccination”). In addition, non-self MoAs can be included in preventive/therapeutic off-the-shelf cancer vaccines with more potent anti-tumor efficacy than those based on TAAs.

BackgroundIn the present study we investigated whether peptides derived from the entire SARS-CoV-2 proteome share homology to TAAs (tumor-associated antigens) and cross-reactive CD8+ T cell can be elicited by the BNT162b2 preventive vaccine or the SARS-CoV-2 natural infection.Methods and resultsViral epitopes with high affinity (<100nM) to the HLA-A*02:01 allele were predicted. Shared and variant-specific epitopes were identified. Significant homologies in amino acidic sequence have been found between SARS-CoV-2 peptides and multiple TAAs, mainly associated with breast, liver, melanoma and colon cancers. The molecular mimicry of the viral epitopes and the TAAs was found in all viral proteins, mostly the Orf 1ab and the Spike, which is included in the BNT162b2 vaccine. Predicted structural similarities confirmed the sequence homology and comparable patterns of contact with both HLA and TCR α and β chains were observed. CD8+ T cell clones cross-reactive with the paired peptides have been found by MHC class l-dextramer staining. ConclusionsOur results show for the first time that several SARS-COV-2 antigens are highly homologous to TAAs and cross-reactive T cells are identified in infected and BNT162b2 preventive vaccinated individuals. The implication would be that the SARS-Cov-2 pandemic could represent a natural preventive immunization for breast, liver, melanoma and colon cancers. In the coming years, real-world evidences will provide the final proof for such immunological experimental evidence. Moreover, such SARS-CoV-2 epitopes can be used to develop “multi-cancer” off-the-shelf preventive/therapeutic vaccine formulations, with higher antigenicity and immunogenicity than over-expressed tumor self-antigens, for the potential valuable benefit of thousands of cancer patients around the World.

Tumors are mostly characterized by genetic instability, as result of mutations in surveillance mechanisms, such as DNA damage checkpoint, DNA repair machinery and mitotic checkpoint. Defect in one or more of these mechanisms causes additive accumulation of mutations. Some of these mutations are drivers of transformation and are positively selected during the evolution of the cancer, giving a growth advantage on the cancer cells. If such mutations would result in mutated neoantigens, these could be actionable targets for cancer vaccines and/or adoptive cell therapies. However, the results of the present analysis show, for the first time, that the most prevalent mutations identified in human cancers do not express mutated neoantigens. The hypothesis is that this is the result of the selection operated by the immune system in the very early stages of tumor development. At that stage, the tumor cells characterized by mutations giving rise to highly antigenic non-self-mutated neoantigens would be efficiently targeted and eliminated. Consequently, the outgrowing tumor cells cannot be controlled by the immune system, with an ultimate growth advantage to form large tumors embedded in an immunosuppressive tumor microenvironment (TME). The outcome of such a negative selection operated by the immune system is that the development of off-the-shelf vaccines, based on shared mutated neoantigens, does not seem to be at hand. This finding represents the first demonstration of the key role of the immune system on shaping the tumor antigen presentation and the implication in the development of antitumor immunological strategies.

Introduction:Currently, conventional treatments of hepatocellular carcinoma (HCC) are not selective enough for tumor tissue and lead to multidrug resistance and drug toxicity. Although sorafenib (SOR) is the standard first-line systemic therapy approved for the clinical treatment of HCC, its poor aqueous solubility and rapid clearance result in low absorption efficiency and severely limit its use for local treatment.Methods:Herein, we present the synthesis of biodegradable polymeric Poly (D, L-Lactide-co-glycolide) (PLGA) particles loaded with SOR (PS) by emulsion-solvent evaporation process. The particles are carefully characterized focusing on particle size, surface charge, morphology, drug loading content, encapsulation efficiency, in vitro stability, drug release behaviour and tested on HepG2 cells. Additionally, PLGA particles have been coupled on side emitting optical fibers (seOF) integrated in a microfluidic device for light-triggered local release.Results:PS have a size of 248 nm, tunable surface charge and a uniform and spherical shape without aggregation. PS shows encapsulation efficiency of 89.7% and the highest drug loading (8.9%) between the SOR-loaded PLGA formulations. Treating HepG2 cells with PS containing SOR at 7.5 µM their viability is dampened to 40%, 30% and 17% after 48, 129 and 168 hours of incubation, respectively.Conclusion:The high PS stability, their sustained release profile and the rapid cellular uptake corroborate the enhanced cytotoxicity effect on HepG2. With the prospect of developing biomedical tools to control the spatial and temporal release of drugs, we successfully demonstrated the potentiality of seOF for light-triggered local release of the carriers. Our prototypical system paves the way to new devices integrating microfluidics, optical fibers, and advanced carriers capable to deliver minimally invasive locoregional cancer treatments.

BACKGROUND:The development of cancer immunotherapeutic strategies relies on the identification and validation of optimal target tumor antigens, which should be tumor-specific as well as able to elicit a swift and potent anti-tumor immune response. The vast majority of such strategies are based on tumor associated antigens (TAAs) which are shared wild type cellular self-epitopes highly expressed on tumor cells. Indeed, TAAs can be used to develop off-the-shelf cancer vaccines appropriate to all patients affected by the same malignancy. However, given that they may be also presented by HLAs on the surface of non-malignant cells, they may be possibly affected by immunological tolerance or elicit autoimmune responses.MAIN BODY:In order to overcome such limitations, analogue peptides with improved antigenicity and immunogenicity able to elicit a cross-reactive T cell response are needed. To this aim, non-self-antigens derived from microorganisms (MoAs) may be of great benefit.

Cancer prevention is one of the aim with the highest priority in order to reduce the burden of cancer diagnosis and treatment on individuals as well as on healthcare systems. To this aim, vaccines represent the most efficient primary cancer prevention strategy. Indeed, anti-cancer immunological memory elicited by preventive vaccines might promptly expand and prevent tumor from progressing. Antigens derived from microorganisms (MoAs), represent the obvious target for developing highly effective preventive vaccines for virus-induced cancers. In this respect, the drastic reduction in cancer incidence following HBV and HPV preventive vaccines are the paradigmatic example of such evidence. More recently, experimental evidences suggest that MoAs may represent a "natural" anti-cancer preventive vaccination or can be exploited for developing vaccines to prevent cancers presenting highly homologous tumor-associated antigens (TAAs) (e.g. molecular mimicry). The present review describes the different preventive anti-cancer vaccines based on antigens derived from pathogens at the different stages of development.

Background TAAs are shared wild-type cellular self-epitopes highly expressed on tumor cells and are used to develop off-the-shelf cancer vaccines appropriate to all patients affected by the same malignancy. However, they may be also presented by HLAs on the surface of non-malignant cells and affected by immunological tolerance or elicit autoimmune responses. In order to overcome such limitations, analogue peptides with improved antigenicity and immunogenicity able to elicit a cross-reactive T cell response are needed. To this aim, non-self-antigens derived from microorganisms (MoAs) may be of great benefit. Indeed, data suggest that MoAs share sequence homology with TAAs ('molecular mimicry') and elicit a cross-reacting CD8+ T cell response. Methods We looked for homology between published TAAs and non-self epitopes derived from viruses as well as microbiota species of the Firmicutes and the Bacteroidetes phyla, which together account for 90% of gut microbiota (MoAs). Blast search for sequence homology was combined with extensive bioinformatics analyses. Cross-reactive T cells were evaluated by tetramer staining as well as IFNg EliSpot assay. Results Several pieces of evidence for homology between TAAs and MoAs have been found. Strikingly, 100% homology between paired sequences has been identified. The predicted average affinity to HLA molecules of MoAs is very high (< 100 nM). The predicted structural conformation of the MoAs is, in general, highly similar to the corresponding TAA, and, in some cases, contact areas with both HLA and TCR chains are indistinguishable. Moreover, the spatial conformation of TCR-facing residues can be identical in paired epitopes, with exactly the same values of planar as well as dihedral angles. T cells cross-reactive with the paired TAAs and MoAs have been identified by tetramer staining as well as IFNg EliSpot assay, confirming the predicted sequence and conformational homology. Conclusions The data reported in the present study show for the first time a comprehensive homology analysis between published TAAs and peptides derived from viruses as well as microbiota species. Cross-reacting CD8+ T cell responses confirm the possibility of eliciting an anti-tumor immunity by non-self peptides derived from viruses as well as microbiota species. This may have a two-fold relevance: 1) the natural T cell memory elicited by MoAs during the lifetime may turn out to be an anti-cancer T cell memory, able to control the tumor growth; 2) such non-self MoAs may be included in preventive/therapeutic cancer vaccines with a more potent anti-tumor efficacy compared to those based on TAAs.1 2 References Ragone C, Manolio C, Cavalluzzo B, Mauriello A, Tornesello ML, Buonaguro FM, Castiglione F, Vitagliano L, Iaccarino E, Ruvo M, Tagliamonte M, Buonaguro L. Identification and validation of viral antigens sharing sequence and structural homology with tumor-associated antigens (TAAs). J Immunother Cancer. 2021 May;9(5):e002694. Tagliamonte M, Cavalluzzo B, Mauriello A, Ragone C, Buonaguro FM, Tornesello ML, Buonaguro L. Molecular mimicry and cancer vaccine development. Mol Cancer. 2023 Apr 26;22(1):75.

Background The gut microbiota profile is unique for each individual and are composed by different bacteria species according to individual birth-to-infant transitions. In the last years, the local and systemic effects of microbiota on cancer onset, progression and response to treatments, such as immunotherapies, has been extensively described. Here we offer a new perspective, proposing a role for the microbiota based on the molecular mimicry of tumor associated antigens by microbiome-associated antigens. Methods In the present study we looked for homology between published TAAs and non-self microbiota-derived epitopes. Blast search for sequence homology was combined with extensive bioinformatics analyses. Results Several evidences for homology between TAAs and microbiota-derived antigens have been found. Strikingly, three cases of 100% homology between the paired sequences has been identified. The predicted average affinity to HLA molecules of microbiota-derived antigens is very high (< 100 nM). The structural conformation of the microbiota-derived epitopes is, in general, highly similar to the corresponding TAA. In some cases, it is identical and contact areas with both HLA and TCR chains are indistinguishable. Moreover, the spatial conformation of TCR-facing residues can be identical in paired TAA and microbiota-derived epitopes, with exactly the same values of planar as well as dihedral angles. Conclusions The data reported in the present study show for the first time the high homology in the linear sequence as well as in structure and conformation between TAAs and peptides derived from microbiota species of the Firmicutes and the Bacteroidetes phyla, which together account for 90% of gut microbiota. Cross-reacting CD8 + T cell responses are very likely induced. Therefore, the anti-microbiota T cell memory may turn out to be an anti-cancer T cell memory, able to control the growth of a cancer developed during the lifetime if the expressed TAA is similar to the microbiota epitope. This may ultimately represent a relevant selective advantage for cancer patients and may lead to a novel preventive anti-cancer vaccine strategy.

Hepatocellular carcinoma (HCC) is the third leading cause of death from cancer globally. Indeed, only a few treatments are available, most of which are effective only for the early stages of the disease. Therefore, there is an urgent needing for potential markers for a specifically targeted therapy. Candidate proteins were selected from datasets of The Human Protein Atlas, in order to identify specific tumor-associated proteins overexpressed in HCC samples associated with poor prognosis. Potential epitopes were predicted from such proteins, and homology with peptides derived from viral proteins was assessed. A multiparametric validation was performed, including recognition by PBMCs from HCC-patients and healthy donors, showing a T-cell cross-reactivity with paired epitopes. These results provide novel HCC-specific tumor-associated antigens (TAAs) for immunotherapeutic anti-HCC strategies potentially able to expand pre-existing virus-specific CD8+ T cells with superior anticancer efficacy.