Adenoviral vaccine targeting multiple neoantigens as strategy to eradicate large tumors combined with checkpoint blockade

Generalization of neoantigen-based tumor vaccine by delivering peptide-MHC complex via oncolytic virus

Neoantigen vaccine is a promising breakthrough in tumor immunotherapy. However, the application of this highly personalized strategy in the treatment of solid tumors is hindered by several obstacles, including very costly and time-consuming preparation steps, uncertainty in prediction algorithms and tumor heterogeneity. Universalization of neoantigen vaccine is an ideal yet currently unattainable solution to such limitations. To overcome these limitations, we engineered oncolytic viruses co-expressing neoantigens and neoantigen-binding major histocompatibility complex (MHC) molecules to force ectopic delivery of peptide-MHC ligands to T cell receptors (TCRs), enabling specific targeting by neoantigen vaccine-primed host immunity. When integrated with neoantigen vaccination, the engineered viruses exhibited potent cytolytic activity in a variety of tumor models irrespective of the neoantigen expression profiles, eliciting robust systemic antitumor immunity to reject tumor rechallenge and inhibit abscopal tumor growth with a favorable safety profile. Thus, this study provides a powerful approach to enhance the universality and efficacy of neoantigen vaccines, meeting the urgent need for universal neoantigen vaccines in the clinic to facilitate the further development of tumor immunotherapy.

Targeting B7-H3 enhances the efficacy of neoantigen-based cancer vaccine in combination with radiotherapy

The clinical response to immune checkpoint blockade (ICB) is limited in the majority of patients with colorectal cancer. These immune checkpoint proteins may not only inhibit T-cell-mediated antitumor immunity but also attenuate antigen presentation, including mutation-associated neoantigens. Here, we found that tumor B7-H3 levels may limit the therapeutic response to chemoradiotherapy in patients with locally-advanced rectal cancer. Knockdown of tumor B7-H3 significantly increased antigen presentation to increase T cell infiltration and killing ability, including neoantigen-specific T-cell response. Blockade of B7-H3 significantly augmented neoantigen-specific T cells response and remarkably enhanced the therapeutic efficacy of neoantigen-based cancer vaccines combined with radiotherapy, decreasing the risk of distant tumors in vivo. Taken together, these results demonstrated that targeting B7-H3 significantly enhanced the therapeutic efficacy of neoantigen cancer vaccines as well as radiotherapy by increasing the extent of neoantigen-specific T cells, even for PD-1/PD-L1 blockade-resistant colorectal cancers.

Zinc Ion-Coordinated Sericin Calcium Phosphate Nanovaccines Induce Hyperactive Dendritic Cells and Synergistic Activation of T Cells for Cancer Immunotherapy

Peptide-based neoantigen vaccines are promising cancer immunotherapy strategies because of their capability to induce durable tumor-specific immune responses. However, insufficient neoantigen-specific T-lymphocyte activation greatly limits their clinical efficacy. Here, we developed sericin-coordinated zinc ion-modified calcium phosphate (CP) nanovaccines that codeliver tumor antigen peptides and a Toll-like receptor 9 agonist (SZCP/APs-CpG) for potentiating antigen-specific T cell immunity. SZCP/APs-CpG nanovaccines could yield efficient codelivery of antigen peptides and adjuvants to dendritic cells (DCs) in draining lymph nodes (dLNs), induce hyperactive DCs depending on the inflammasome-dependent interleukin-1β secretion, and coordinate the released Zn2+-induced T cell activation to elicit robust and durable antigen-specific T cell immune responses. Vaccination with SZCP/APs-CpG exhibited potent anticancer efficacy and superior safety in multiple murine cancer models and significantly protected against B16-OVA tumor rechallenge and eradicated orthotopic colon cancer in mice when combined with immune checkpoint blockade. Thus, our work presents an efficient and versatile nanovaccine platform for boosting antigen-specific T cell activation for cancer immunotherapy.

Neoantigen Vaccines in Cancer Prevention

Recent advances in cancer immunotherapy have established neoantigen-based vaccines as a promising approach to cancer prevention. Unlike tumor-associated antigens, neoantigens originate exclusively from somatic mutations, thus enabling tumor-specific targeting without harm to normal tissues. This distinctive feature promotes robust immune responses while reducing the risk of autoimmune side effects. Developing standardized "off-the-shelf" vaccines targeting shared neoantigens offers a scalable strategy for cancer prevention, particularly benefitting genetically predisposed high-risk populations. These vaccines can be administered to high-risk individuals before malignant transformation to potentially intercept cancer development through early immune activation. Advances in next-generation sequencing and computational biology have increased the accuracy of neoantigen prediction, while advances in vaccine delivery platforms have boosted vaccine efficacy. The integration of neoantigen-based vaccines with immune checkpoint inhibitors, immune stimulants, and classic chemopreventive agents has a synergistic potential to improve cellular immunity. This review examines biological mechanisms, clinical development, and future directions of neoantigen-based vaccines in cancer prevention, emphasizing their clinical potential to revolutionize risk-reduction strategies.

Depletion of regulatory T cells enhances the T cell response induced by the neoantigen vaccine with weak immunogenicity

BACKGROUND

The neoantigen vaccine has remarkable potential in treating advanced cancer due to its tumor specificity and ability to bypass central tolerance mechanisms. However, numerous neoantigens show poor immunogenicity, and the immune inhibitory factors of present in both tumors and tumor-draining lymph nodes impair the efficacy of cancer neoantigen vaccine. Eliminating immunosuppressive cells will improve the priming and expansion of anti-tumor immune cells induced by the vaccine.

METHODS

In this study, a Treg-depleting regimen (consisting of CD25mAb and low-dose cyclophosphamide (LD-CTX)) was used in conjunction with a neoantigen vaccine for treating mice with solid tumors. We constructed two types of tumor models and investigated differences in therapy efficacy in the four groups (PBS, vaccine, CD25mAb+CTX and combination) at the genetic and protein levels. ELISPOT and TCR sequencing were applied to detect the expansion of neoantigen reactive T cells (NRT) and tumor antigen spreading.

RESULTS

In the combinational group, the ELISPOT results showed an obvious expansion of NRT cells induced by weak immunogenic peptides. The combinational group exhibited significant improvement in inhibiting the tumor growth extended the survival time of tumor-bearing mice, and promoted T cells infiltration into tumors. Besides, compared to the Vac group, more neoantigen-targeted and TAA-targeted T cells were detected in the combinational group by TCR sequencing. The results of transcriptomic sequencing and flow cytometry showed that the number of Tregs in the combinational group was lower, while the proportions of memory effector T cells and effector T cells were higher than those in the vaccine group. An increase in mature DCs was also observed in vaccinated mice after receiving this Treg-depleting strategy.

CONCLUSION

Our research first revealed that inhibiting the normal function of Tregs transformed "weaker" neoantigens into "stronger" ones, while also contributing to the proliferation of NRT cells. This Treg-depleting strategy allowed neoantigens with poor immunogenicity to elicit a robust immune response, thereby augmenting the efficacy of the neoantigen vaccine in delaying tumor growth and prolonging the survival of the hosts.

Co-immunization with IFI35 enhances the therapeutic effect of an adenovirus vaccine against renal carcinoma

Interferon-induced protein 35 (IFI35), an immunomodulator, is highly expressed in tumor cells, yet its role in enhancing tumor vaccine efficacy remains unclear. In this study, an adenovirus (Ad) vaccine encoding dual targets, IFI35 and carbonic anhydrase IX (CAIX), was developed for renal carcinoma treatment. Co-immunization with Ad-IFI35/CAIX effectively inhibited tumor growth in a subcutaneous model and significantly increased the infiltration of CD8+ T cells and dendritic cells (DCs). Furthermore, Ad-IFI35/CAIX administration induced strong cytotoxic T lymphocyte (CTL) responses and expanded multifunctional CD8+ T cell populations. Depletion of CD8+ T cells abolished the vaccine's tumor regression effects, confirming that its therapeutic effect relies on CD8+ T cell-mediated immunity. In addition, Ad-IFI35/CAIX treatment enhanced the induction of memory CTL responses, effectively suppressing the growth of tumors implanted contralaterally. The Ad-IFI35/CAIX vaccine also elicited a strong CD8+ T cell-mediated immunity against tumor metastasis and growth in lung metastasis and orthotopic renal carcinoma models. These results indicate that the Ad vaccine dual targeting IFI35 and CAIX is a potential strategy for renal carcinoma treatment.

Adenoviral-vectored neoantigen vaccine augments hyperexpanded CD8+ T cell control of tumor challenge in mice

BACKGROUND

Neoantigens are promising immunogens for cancer vaccines and are often delivered as adjuvanted peptide vaccines. Adenoviral (Ad) vectors have been shown to induce strong CD8+ T cell responses as vaccines against SARS-CoV-2, Ebola, and Zika, but their utility as neoantigen delivery vectors remains largely unexplored. In this study, we examine how an Ad-vectored neoantigen vaccine would impact tumor immunity compared with a peptide neoantigen vaccine.

METHODS

We generated Ad serotype 26 (Ad26) vaccine candidates encoding B16-F10-ovalbumin (OVA) and MC38-specific neoantigens. Ad26 vaccines were compared with adjuvanted peptide delivery as prophylactic vaccines in B16-F10-OVA and MC38 challenge models. Immune responses induced by the best Ad26 vaccine (Ad26.VP22.7Epi) were compared with peptide vaccination systemically and within the tumor. Following vaccination with Ad26.VP22.7Epi, peptide, or sham, tumor-infiltrating CD45+ cells were analyzed using single-cell RNA sequencing (scRNA-seq) and T cell receptor sequencing (TCR-seq) to identify vaccine-induced differences in the tumor microenvironment.

RESULTS

Single-shot Ad26 vaccines induced greater neoantigen-specific interferon-γ CD8+ T cell immune responses than two-shot adjuvanted peptide vaccines in mice, and Ad26.VP22.7Epi also provided superior protective efficacy compared with the peptide vaccine following tumor challenge. Ad26.VP22.7Epi induced a robust immunodominant CD8+ T cell response against the Adpgk neoantigen, while the peptide vaccine-induced lower responses against both Adpgk and Reps1 neoantigens. scRNA-seq analysis of CD45+ tumor-infiltrating cells demonstrated that both Ad26.VP22.7Epi and peptide vaccine-induced similar numbers of infiltrating CD8+ T cells. However, Ad26.VP22.7Epi induced CD8+ T cells showed more upregulation of T cell maturation, activation, and Th1 pathways compared with peptide vaccine induced CD8+ T cells, suggesting improved functional T cell quality. TCR-seq of these tumor-infiltrating lymphocytes also demonstrated that Ad26.VP22.7Epi generated larger T cell hyperexpanded clones compared with the peptide vaccine.

CONCLUSIONS

These results suggest that the Ad26.VP22.7Epi vaccine led to improved tumor control compared with the peptide vaccine due to increased T cell hyperexpansion and functional activation. Our data suggest that future cancer vaccine development strategies should focus on inducing functional hyperexpanded CD8+ T cell responses and not only maximizing tumor infiltrating CD8+ T cell numbers.

Therapeutic vaccine targeting dual immune checkpoints induces potent multifunctional CD8+ T cell anti-tumor immunity

BACKGROUND

Vaccines targeting immune checkpoints represent a promising immunotherapeutic approach for solid tumors. However, the therapeutic efficacy of dual targeting immune checkpoints is still unclear in renal carcinoma.

METHODS

An adenovirus (Ad) vaccine targeting B7H1 and B7H3 was developed and evaluated for its therapeutic efficacy in subcutaneous, lung metastasis or orthotopic renal carcinoma mouse and humanized models using flow cytometry, Enzyme-linked immunosorbent spot (ELISPOT), cytotoxic T lymphocyte (CTL) killing, cell deletion, hematoxylin and eosin (HE) staining, and immunohistochemistry (IHC) assays.

RESULTS

The Ad-B7H1/B7H3 immunization effectively inhibited tumor growth and increased the induction and percentages of CD8+ T cells in subcutaneous tumor models. The vaccine enhanced the induction and maturation of CD11c+ or CD8+CD11c+ cells, promoting tumor-specific CD8+ T cell immune responses. This was evidenced by increased proliferation of CD8+ T cells and enhanced CTL killing activity. Deletion of CD8+ T cells in vivo abolished the anti-tumor effect of the Ad-B7H1/B7H3 vaccine, highlighting the pivotal role of functional CD8+ T cell immune responses. Moreover, significant therapeutic efficacy of the Ad-B7H1/B7H3 vaccine was observed in lung metastasis, orthotopic, and humanized tumor models through multifunctional CD8+ T cell immune responses.

CONCLUSIONS

The Ad vaccine targeting dual immune checkpoints B7H1 and B7H3 exerts a potent therapeutic effect for renal carcinoma and holds promise for solid tumor treatment.

Comparing neoantigen cancer vaccines and immune checkpoint therapy unveils an effective vaccine and anti-TREM2 macrophage-targeting dual therapy

The goal of therapeutic cancer vaccines and immune checkpoint therapy (ICT) is to promote T cells with anti-tumor capabilities. Here, we compared mutant neoantigen (neoAg) peptide-based vaccines with ICT in preclinical models. NeoAg vaccines induce the most robust expansion of proliferating and stem-like PD-1+TCF-1+ neoAg-specific CD8 T cells in tumors. Anti-CTLA-4 and/or anti-PD-1 ICT promotes intratumoral TCF-1- neoAg-specific CD8 T cells, although their phenotype depends in part on the specific ICT used. Anti-CTLA-4 also prompts substantial changes to CD4 T cells, including induction of ICOS+Bhlhe40+ T helper 1 (Th1)-like cells. Although neoAg vaccines or ICTs expand iNOS+ macrophages, neoAg vaccines maintain CX3CR1+CD206+ macrophages expressing the TREM2 receptor, unlike ICT, which suppresses them. TREM2 blockade enhances neoAg vaccine efficacy and is associated with fewer CX3CR1+CD206+ macrophages and induction of neoAg-specific CD8 T cells. Our findings highlight different mechanisms underlying neoAg vaccines and different forms of ICT and identify combinatorial therapies to enhance neoAg vaccine efficacy.

Probiotic neoantigen delivery vectors for precision cancer immunotherapy

Microbial systems have been synthetically engineered to deploy therapeutic payloads in vivo1,2. With emerging evidence that bacteria naturally home in on tumours3,4 and modulate antitumour immunity5,6, one promising application is the development of bacterial vectors as precision cancer vaccines2,7. Here we engineered probiotic Escherichia coli Nissle 1917 as an antitumour vaccination platform optimized for enhanced production and cytosolic delivery of neoepitope-containing peptide arrays, with increased susceptibility to blood clearance and phagocytosis. These features enhance both safety and immunogenicity, achieving a system that drives potent and specific T cell-mediated anticancer immunity that effectively controls or eliminates tumour growth and extends survival in advanced murine primary and metastatic solid tumours. We demonstrate that the elicited antitumour immune response involves recruitment and activation of dendritic cells, extensive priming and activation of neoantigen-specific CD4+ and CD8+ T cells, broader activation of both T and natural killer cells, and a reduction of tumour-infiltrating immunosuppressive myeloid and regulatory T and B cell populations. Taken together, this work leverages the advantages of living medicines to deliver arrays of tumour-specific neoantigen-derived epitopes within the optimal context to induce specific, effective and durable systemic antitumour immunity.

Neoantigen sequestrated autophagosomes as therapeutic cancer vaccines

Neoantigens serve as ideal personalized cancer vaccines because of their high immunogenicity, ability to evade central thymic tolerance, and minimal risk of eliciting autoimmune responses. Herein, we describe a genetically engineered autophagosome-based neoantigen vaccine (APNV) in combination with an immune checkpoint inhibitor (anti-PD-1 antibody) for cancer immunotherapy. The APNV was derived from engineered NIH 3T3 cells, which co-express melanoma neoantigens and autophagosome maker microtubule-associated proteins 1 A/1B light chain 3B (LC3), from which the LC3-labeled neoantigen-autophagosomes were isolated. These purified autophagosomes, in conjunction with vaccine adjuvants high-mobility group box 1 (HMGB1) and granulocyte-macrophage colony-stimulating factor (GM-CSF), were integrated into a hydrogel to create an APNV. The APNV effectively activated dendritic cells both in vitro and in vivo. Moreover, APNV, in combination with checkpoint blockade therapy, significantly hampered post-surgical tumor recurrence in a subcutaneous melanoma tumor model and effectively impeded metastatic progression in a melanoma lung metastasis model. This APNV may be conducive to making personalized therapeutic neoantigen vaccines for cancer immunotherapy.

Immunoprevention Strategies for Colorectal Cancer in Lynch Syndrome Carriers

ABSTRACT

The immune revolution that swept the field of oncology in the mid-2010s with the advent of checkpoint inhibitors has led to a paradigm shift in approaches toward adapting new cancer prevention modalities. Cancer vaccines have emerged from this era with astounding potential as a durable intervention to prevent cancers especially for patients with hereditary susceptibilities such as Lynch syndrome carriers. This review covers new insights in the immunoprevention landscape for patients living with Lynch syndrome including highlights ranging from clinical trials exploring the use of chemoprevention agents to boost immune cellularity to investigative studies using novel vaccine approaches to induce long-term antitumor immunity.

Reprogramming the tumor immune microenvironment using engineered dual-drug loaded Salmonella

Synergistic combinations of immunotherapeutic agents can improve the performance of anti-cancer therapies but may lead to immune-mediated adverse effects. These side-effects can be overcome by using a tumor-specific delivery system. Here, we report a method of targeted immunotherapy using an attenuated Salmonella typhimurium (SAM-FC) engineered to release dual payloads: cytolysin A (ClyA), a cytolytic anti-cancer agent, and Vibrio vulnificus flagellin B (FlaB), a potent inducer of anti-tumor innate immunity. Localized secretion of ClyA from SAM-FC induces immunogenic cancer cell death and promotes release of tumor-specific antigens and damage-associated molecular patterns, which establish long-term antitumor memory. Localized secretion of FlaB promotes phenotypic and functional remodeling of intratumoral macrophages that markedly inhibits tumor metastasis in mice bearing tumors of mouse and human origin. Both primary and metastatic tumors from bacteria-treated female mice are characterized by massive infiltration of anti-tumorigenic innate immune cells and activated tumor-specific effector/memory T cells; however, the percentage of immunosuppressive cells is low. Here, we show that SAM-FC induces functional reprogramming of the tumor immune microenvironment by activating both the innate and adaptive arms of the immune system and can be used for targeted delivery of multiple immunotherapeutic payloads for the establishment of potent and long-lasting antitumor immunity.

Biomaterials-assisted cancer vaccine delivery: preclinical landscape, challenges, and opportunities

INTRODUCTION

Cancer vaccines (protein and peptide, DNA, mRNA, and tumor cell) have achieved remarkable success in the treatment of cancer. In particular, advances in the design and manufacture of biomaterials have made it possible to control the presentation and delivery of vaccine components to immune cells.

AREAS COVERED

This review summarizes findings from major databases, including PubMed, Scopus, and Web of Science, focusing on articles published between 2005 and 2024 that discuss biomaterials in cancer vaccine delivery.

EXPERT OPINION

The development of cancer vaccines is hindered by several bottlenecks, including low immunogenicity, instability of vaccine components, and challenges in evaluating their clinical efficacy. To transform preclinical successes into viable treatments, it is essential to pursue continued innovation, collaborative research, and address issues related to scalability, regulatory pathways, and clinical validation, ultimately improving outcomes against cancer.

Phase I Trial of Viral Vector-Based Personalized Vaccination Elicits Robust Neoantigen-Specific Antitumor T-Cell Responses

PURPOSE

Personalized vaccines targeting multiple neoantigens (nAgs) are a promising strategy for eliciting a diversified antitumor T-cell response to overcome tumor heterogeneity. NOUS-PEV is a vector-based personalized vaccine, expressing 60 nAgs and consists of priming with a nonhuman Great Ape Adenoviral vector (GAd20) followed by boosts with Modified Vaccinia Ankara. Here, we report data of a phase Ib trial of NOUS-PEV in combination with pembrolizumab in treatment-naïve patients with metastatic melanoma (NCT04990479).

PATIENTS AND METHODS

The feasibility of this approach was demonstrated by producing, releasing, and administering to 6 patients 11 of 12 vaccines within 8 weeks from biopsy collection to GAd20 administration.

RESULTS

The regimen was safe, with no treatment-related serious adverse events observed and mild vaccine-related reactions. Vaccine immunogenicity was demonstrated in all evaluable patients receiving the prime/boost regimen, with detection of robust neoantigen-specific immune responses to multiple neoantigens comprising both CD4 and CD8 T cells. Expansion and diversification of vaccine-induced T-cell receptor (TCR) clonotypes was observed in the posttreatment biopsies of patients with clinical response, providing evidence of tumor infiltration by vaccine-induced neoantigen-specific T cells.

CONCLUSIONS

These findings indicate the ability of NOUS-PEV to amplify and broaden the repertoire of tumor-reactive T cells to empower a diverse, potent, and durable antitumor immune response. Finally, a gene signature indicative of the reduced presence of activated T cells together with very poor expression of the antigen-processing machinery genes has been identified in pretreatment biopsies as a potential biomarker of resistance to the treatment.

Immune landscape and response to oncolytic virus-based immunotherapy

Oncolytic virus (OV)-based immunotherapy has emerged as a promising strategy for cancer treatment, offering a unique potential to selectively target malignant cells while sparing normal tissues. However, the immunosuppressive nature of tumor microenvironment (TME) poses a substantial hurdle to the development of OVs as effective immunotherapeutic agents, as it restricts the activation and recruitment of immune cells. This review elucidates the potential of OV-based immunotherapy in modulating the immune landscape within the TME to overcome immune resistance and enhance antitumor immune responses. We examine the role of OVs in targeting specific immune cell populations, including dendritic cells, T cells, natural killer cells, and macrophages, and their ability to alter the TME by inhibiting angiogenesis and reducing tumor fibrosis. Additionally, we explore strategies to optimize OV-based drug delivery and improve the efficiency of OV-mediated immunotherapy. In conclusion, this review offers a concise and comprehensive synopsis of the current status and future prospects of OV-based immunotherapy, underscoring its remarkable potential as an effective immunotherapeutic agent for cancer treatment.

Current Trends in Vaccine Development for Hereditary Colorectal Cancer Syndromes

The coming of age for cancer treatment has experienced exponential growth in the last decade with the addition of immunotherapy as the fourth pillar to the fundamentals of cancer treatment-chemotherapy, surgery, and radiation-taking oncology to an astounding new frontier. In this time, rapid developments in computational biology coupled with immunology have led to the exploration of priming the host immune system through vaccination to prevent and treat certain subsets of cancer such as melanoma and hereditary colorectal cancer. By targeting the immune system through tumor-specific antigens-namely, neoantigens (neoAgs)-the future of cancer prevention may lie within arm's reach by employing neoAg vaccines as an immune-preventive modality for hereditary cancer syndromes like Lynch syndrome. In this review, we discuss the history, current trends, utilization, and future direction of neoAg-based vaccines in the setting of hereditary colorectal cancer.

Tumor Burden Dictates the Neoantigen Features Required to Generate an Effective Cancer Vaccine

Tumor neoantigens (nAg) represent a promising target for cancer immunotherapy. The identification of nAgs that can generate T-cell responses and have therapeutic activity has been challenging. Here, we sought to unravel the features of nAgs required to induce tumor rejection. We selected clinically validated Great Ape-derived adenoviral vectors (GAd) as a nAg delivery system for differing numbers and combinations of nAgs. We assessed their immunogenicity and efficacy in murine models of low to high disease burden, comparing multi-epitope versus mono-epitope vaccines. We demonstrated that the breadth of immune response is critical for vaccine efficacy and having multiple immunogenic nAgs encoded in a single vaccine improves efficacy. The contribution of each single neoantigen was examined, leading to the identification of 2 nAgs able to induce CD8+ T cell-mediated tumor rejection. They were both active as individual nAgs in a setting of prophylactic vaccination, although to different extents. However, the efficacy of these single nAgs was lost in a setting of therapeutic vaccination in tumor-bearing mice. The presence of CD4+ T-cell help restored the efficacy for only the most expressed of the two nAgs, demonstrating a key role for CD4+ T cells in sustaining CD8+ T-cell responses and the necessity of an efficient recognition of the targeted epitopes on cancer cells by CD8+ T cells for an effective antitumor response. This study provides insight into understanding the determinants of nAgs relevant for effective treatment and highlights features that could contribute to more effective antitumor vaccines. See related Spotlight by Slingluff Jr, p. 382.

Optimal Neoantigen Cancer Vaccines Target CD8+ and CD4+ T Cells with Multiple Antigens

Cancer vaccines targeting mutated neoantigens offer promise for prevention of cancer recurrence and for treatment of established cancers. Questions remain about whether vaccines need to target multiple neoantigens and whether they need to target both CD8+ and CD4+ T cells. In this issue, Garzia and colleagues demonstrate the importance of including multiple antigens to stimulate both CD4+ T cells and CD8+ T cells for treatment of established cancer. See related article by Garzia et al., p. 440 (4).

Prime and pull of T cell responses against cancer-exogenous antigens is effective against CPI-resistant tumors

Neoantigen (neoAg)-based cancer vaccines expand preexisting antitumor immunity and elicit novel cancer-specific T cells. However, at odds with prophylactic vaccines, therapeutic antitumor immunity must be induced when the tumor is present and has already established an immunosuppressive environment capable of rapidly impairing the function of anticancer neoAg T cells, thereby leading to lack of efficacy. To overcome tumor-induced immunosuppression, we first vaccinated mice bearing immune checkpoint inhibitor (CPI)-resistant tumors with an adenovirus vector encoding a set of potent cancer-exogenous CD8 and CD4 T cell epitopes (Ad-CAP1), and then "taught" cancer cells to express the same epitopes by using a tumor-retargeted herpesvirus vector (THV-CAP1). Potent CD8 effector T lymphocytes were elicited by Ad-CAP1, and subsequent THV-CAP1 delivery led to a significant delay in tumor growth and even cure.

A Trinity Nano-Vaccine System with Spatiotemporal Immune Effect for the Adjuvant Cancer Therapy after Radiofrequency Ablation

Cancer vaccine gains great attention with the advances in tumor immunology and nanotechnology, but its long-term efficacy is restricted by the unsustainable immune activity after vaccination. Here, we demonstrate the vaccine efficacy is negatively correlated with the tumor burden. To maximum the vaccine-induced immunity and prolong the time-effectiveness, we design a priming-boosting vaccination strategy by combining with radiofrequency ablation (RFA), and construct a bisphosphonate nanovaccine (BNV) system. BNV system consists of nanoparticulated bisphosphonates with dual electric potentials (BNV(+&-)), where bisphosphonates act as the immune adjuvant by blocking mevalonate metabolism. BNV(+&-) exhibits the spatial and temporal heterogeneity in lymphatic delivery and immune activity. As the independent components of BNV(+&-), BNV(-) is drained to the lymph nodes, and BNV(+) is retained at the injection site. The alternately induced immune responses extend the time-effectiveness of antitumor immunity and suppress the recurrence and metastasis of colorectal cancer liver metastases after RFA. As a result, this trinity system integrated with RFA therapy, bisphosphonate adjuvant, and spatiotemporal immune effect provides an orientation for the sustainable regulation and precise delivery of cancer vaccines.

Immunotherapy for colorectal cancer: Rational strategies and novel therapeutic progress

There are increasing incidences and mortality rates for colorectal cancer in the world. It is common for chemotherapy and radiation given to patients with colorectal cancer to cause toxicities that limit their effectiveness and cause cancer cells to become resistant to these treatments. Additional targeted treatments are needed to improve patient's quality of life and outcomes. Immunotherapy has rapidly emerged as an incredibly exciting and promising avenue for cancer treatment in recent years. This innovative approach provides novel options for tackling solid tumors, effectively establishing itself as a new cornerstone in cancer treatment. Specifically, in the realm of colorectal cancer (CRC), there is great promise in developing new drugs that target immune checkpoints, offering a hopeful and potentially transformative solution. While immunotherapy of CRC has made significant advances, there are still obstacles and limitations. CRC patients have a poor response to treatment because of the immune-suppressing function of their tumor microenvironment (TME). In addition to blocking inhibitory immune checkpoints, checkpoint-blocking antibodies may also boost immune responses against tumors. The review summarizes recent advances in immune checkpoint inhibitors (ICIs) for CRC, including CTLA-4, PD-1, PD-L1, LAG-3, and TIM-3.

Oncolytic adenovirus coding for shedding-resistant MICA enhances immune responses against tumors

Cancer immunotherapies strive to overcome tumor-induced immune suppression and activate antitumor immune responses. Although cytotoxic T lymphocytes (CTLs) play a pivotal role in this process, natural killer (NK) cells have also demonstrated remarkable tumor-killing abilities, given their ability to discriminate tumor cells from normal cells and mediate specific antitumoral cytotoxicity. NK cells activation depends on a balance between activation and inhibition signals from several ligands/receptors. Among them, MICA/NKG2D axis is a master regulator of NK activation. MHC class I chain-related polypeptide A (MICA) expression is upregulated by many tumor cell lines and primary tumors and serves as a ligand for the activating NK group 2D (NKG2D) receptor on NK cells and subpopulations of T cells. However, cancer cells can cleave MICA, making it soluble and de-targeting tumor cells from NK cells, leading to tumor immune escape.In this study, we present ICOVIR15KK-MICAMut, an oncolytic adenovirus (OAdv) armed with a transgene encoding a non-cleavable MICA to promote NK-mediated cell-killing capacity and activate the immune response against cancer cells. We first demonstrated the correct MICA overexpression from infected cells. Moreover, our MICA-expressing OAdv promotes higher NK activation and killing capacity than the non-armed virus in vitro. In addition, the armed virus also demonstrated significant antitumor activity in immunodeficient mice in the presence of human PBMCs, indicating the activation of human NK cells. Finally, OAdv-MICA overexpression in immunocompetent tumor-bearing mice elicits tumor-specific immune response resulting in a greater tumor growth control.In summary, this study highlights the significance of NK cells in cancer immunotherapy and presents an innovative approach using a modified oncolytic virus to enhance NK cell activation and antitumor immune response. These findings suggest promising potential for future research and clinical applications.

Virus-like particle-mediated delivery of structure-selected neoantigens demonstrates immunogenicity and antitumoral activity in mice

BACKGROUND

Neoantigens are patient- and tumor-specific peptides that arise from somatic mutations. They stand as promising targets for personalized therapeutic cancer vaccines. The identification process for neoantigens has evolved with the use of next-generation sequencing technologies and bioinformatic tools in tumor genomics. However, in-silico strategies for selecting immunogenic neoantigens still have very low accuracy rates, since they mainly focus on predicting peptide binding to Major Histocompatibility Complex (MHC) molecules, which is key but not the sole determinant for immunogenicity. Moreover, the therapeutic potential of neoantigen-based vaccines may be enhanced using an optimal delivery platform that elicits robust de novo immune responses.

METHODS

We developed a novel neoantigen selection pipeline based on existing software combined with a novel prediction method, the Neoantigen Optimization Algorithm (NOAH), which takes into account structural features of the peptide/MHC-I interaction, as well as the interaction between the peptide/MHC-I complex and the TCR, in its prediction strategy. Moreover, to maximize neoantigens' therapeutic potential, neoantigen-based vaccines should be manufactured in an optimal delivery platform that elicits robust de novo immune responses and bypasses central and peripheral tolerance.

RESULTS

We generated a highly immunogenic vaccine platform based on engineered HIV-1 Gag-based Virus-Like Particles (VLPs) expressing a high copy number of each in silico selected neoantigen. We tested different neoantigen-loaded VLPs (neoVLPs) in a B16-F10 melanoma mouse model to evaluate their capability to generate new immunogenic specificities. NeoVLPs were used in in vivo immunogenicity and tumor challenge experiments.

CONCLUSIONS

Our results indicate the relevance of incorporating other immunogenic determinants beyond the binding of neoantigens to MHC-I. Thus, neoVLPs loaded with neoantigens enhancing the interaction with the TCR can promote the generation of de novo antitumor-specific immune responses, resulting in a delay in tumor growth. Vaccination with the neoVLP platform is a robust alternative to current therapeutic vaccine approaches and a promising candidate for future personalized immunotherapy.

Oncolytic Viruses in the Era of Omics, Computational Technologies, and Modeling: Thesis, Antithesis, and Synthesis

Oncolytic viruses (OVs) are the frontier therapy for refractory cancers, especially in integration with immunomodulation strategies. In cancer immunovirotherapy, the many available "omics" and systems biology technologies generate at a fast pace a challenging huge amount of data, where apparently clashing information mirrors the complexity of individual clinical situations and OV used. In this review, we present and discuss how currently big data analysis, on one hand and, on the other, simulation, modeling, and computational technologies, provide invaluable support to interpret and integrate "omic" information and drive novel synthetic biology and personalized OV engineering approaches for effective immunovirotherapy. Altogether, these tools, possibly aided in the future by artificial intelligence as well, will allow for the blending of the information into OV recombinants able to achieve tumor clearance in a patient-tailored way. Various endeavors to the envisioned "synthesis" of turning OVs into personalized theranostic agents are presented.

Personalized Cancer Vaccines Go Viral: Viral Vectors in the Era of Personalized Immunotherapy of Cancer

The aim of personalized cancer vaccines is to elicit potent and tumor-specific immune responses against neoantigens specific to each patient and to establish durable immunity, while minimizing the adverse events. Over recent years, there has been a renewed interest in personalized cancer vaccines, primarily due to the advancement of innovative technologies for the identification of neoantigens and novel vaccine delivery platforms. Here, we review the emerging field of personalized cancer vaccination, with a focus on the use of viral vectors as a vaccine platform. The recent advancements in viral vector technology have led to the development of efficient production processes, positioning personalized viral vaccines as one of the preferred technologies. Many clinical trials have shown the feasibility, safety, immunogenicity and, more recently, preliminary evidence of the anti-tumor activity of personalized vaccination, fostering active research in the field, including further clinical trials for different tumor types and in different clinical settings.

Advances in vaccine development for cancer prevention and treatment in Lynch Syndrome

Lynch Syndrome (LS) is one of the most common hereditary cancer syndromes, and is caused by mutations in one of the four DNA mismatch repair (MMR) genes, namely MLH1, MSH2, MSH6 and PMS2. Tumors developed by LS carriers display high levels of microsatellite instability, which leads to the accumulation of large numbers of mutations, among which frameshift insertion/deletions (indels) within microsatellite (MS) loci are the most common. As a result, MMR-deficient (MMRd) cells generate increased rates of tumor-specific neoantigens (neoAgs) that can be recognized by the immune system to activate cancer cell killing. In this context, LS is an ideal disease to leverage immune-interception strategies. Therefore, the identification of these neoAgs is an ongoing effort for the development of LS cancer preventive vaccines. In this review, we summarize the computational methods used for in silico neoAg prediction, including their challenges, and the experimental techniques used for in vitro validation of their immunogenicity. In addition, we outline results from past and on-going vaccine clinical trials and highlight avenues for improvement and future directions.

Organoids and metastatic orthotopic mouse model for mismatch repair-deficient colorectal cancer

Background

Genome integrity is essential for the survival of an organism. DNA mismatch repair (MMR) genes (e.g., MLH1, MSH2, MSH6, and PMS2) play a critical role in the DNA damage response pathway for genome integrity maintenance. Germline mutations of MMR genes can lead to Lynch syndrome or constitutional mismatch repair deficiency syndrome, resulting in an increased lifetime risk of developing cancer characterized by high microsatellite instability (MSI-H) and high mutation burden. Although immunotherapy has been approved for MMR-deficient (MMRd) cancer patients, the overall response rate needs to be improved and other management options are needed.

Methods

To better understand the biology of MMRd cancers, elucidate the resistance mechanisms to immune modulation, and develop vaccines and therapeutic testing platforms for this high-risk population, we generated organoids and an orthotopic mouse model from intestine tumors developed in a Msh2-deficient mouse model, and followed with a detailed characterization.

Results

The organoids were shown to be of epithelial origin with stem cell features, to have a high frameshift mutation frequency with MSI-H and chromosome instability, and intra- and inter-tumor heterogeneity. An orthotopic model using intra-cecal implantation of tumor fragments derived from organoids showed progressive tumor growth, resulting in the development of adenocarcinomas mixed with mucinous features and distant metastasis in liver and lymph node.

Conclusions

The established organoids with characteristics of MSI-H cancers can be used to study MMRd cancer biology. The orthotopic model, with its distant metastasis and expressing frameshift peptides, is suitable for evaluating the efficacy of neoantigen-based vaccines or anticancer drugs in combination with other therapies.

Worth a Pound of Cure? Emerging Strategies and Challenges in Cancer Immunoprevention

Cancer immunoprevention applies immunologic approaches such as vaccines to prevent, rather than to treat or cure, cancer. Despite limited success in the treatment of advanced disease, the development of cancer vaccines to intercept premalignant states is a promising area of current research. These efforts are supported by the rationale that vaccination in the premalignant setting is less susceptible to mechanisms of immune evasion compared with established cancer. Prophylactic vaccines have already been developed for a minority of cancers mediated by oncogenic viruses (e.g., hepatitis B and human papillomavirus). Extending the use of preventive vaccines to non-virally driven malignancies remains an unmet need to address the rising global burden of cancer. This review provides a broad overview of clinical trials in cancer immunoprevention with an emphasis on emerging vaccine targets and delivery platforms, translational challenges, and future directions.

The co-delivery of adenovirus-based immune checkpoint vaccine elicits a potent anti-tumor effect in renal carcinoma

Immune-based checkpoint therapy has made significant progress in cancer treatment, but its therapeutic effect is limited. A replication-defective adenovirus (Ad) vaccine encoding tumor antigen carbonic anhydrase IX (CAIX) combined with Ad-encoding immune checkpoint PD-L1 was developed to treat renal carcinoma. Three tumor models, subcutaneous, lung metastasis and orthotopic tumor were established, and Ad vaccines were used to immunize them and evaluate the vaccine's therapeutic effect. Compared to the single Ad vaccine group, the subcutaneous tumor growth was significantly reduced in Ad-CAIX/Ad-PD-L1 combination group. Co-immunization of Ad-CAIX/Ad-PD-L1 enhanced the induction and maturation of CD11c+ or CD8+CD11c+ DCs in the spleen and tumor and promoted the strong tumor-specific CD8+ T cell immune responses. In vivo CD8 T cell deletion assay showed that the anti-tumor effect of the Ad-CAIX/Ad-PD-L1 vaccine was mainly dependent on functional CD8+ T cell immune responses. Furthermore, the Ad-CAIX/Ad-PD-L1 vaccine effectively inhibited tumor growth and lung metastasis in metastatic or orthotopic models. These results indicate that the combination strategy of the immune checkpoint vaccine shows promising potential as an approach for malignant tumor therapy.

Comparison of Three Different Methods of Transfection for the Production of Recombinant Adenovirus Expressing Human Carcinoembryonic Antigen Gene

Adenoviral vectors (AdVs) are widely used as a gene delivery vehicle and vaccine design due to their genetic stability, transfer capacity of large genes, production at high titers, and remarkable efficacy of transduction. One of the most important applications of AdVs is in cancer immunotherapy. Tumor-associated antigens are overexpressed in cancer cells; however, they cannot induce immune responses sufficiently. Therefore, the immune system must be stimulated against these antigens to kill the cancer cells. This study described the construction steps of a recombinant AdV expressing human carcinoembryonic antigen (CEA) gene. Furthermore, in order to achieve a high titer of the virus, an efficient transfection was required. Three various transfection reagents were compared to achieve the best method of transfection. Carcinoembryonic antigen was cloned into the pAdV and transfected into the A293 cells using three different reagents, including polyethylenimine (PEI), calcium phosphate, and DMRIE-C. The PEI had the highest transfection efficiency, which was selected for the transfection of the recombinant plasmid. It has low toxicity for cells and is suitable for large-scale transfection. The virus produced in this study can be applied as a vaccine in cancer immunotherapy for stimulating the immune system against CEA-expressing tumors.

DNA based neoepitope vaccination induces tumor control in syngeneic mouse models

Recent findings have positioned tumor mutation-derived neoepitopes as attractive targets for cancer immunotherapy. Cancer vaccines that deliver neoepitopes via various vaccine formulations have demonstrated promising preliminary results in patients and animal models. In the presented work, we assessed the ability of plasmid DNA to confer neoepitope immunogenicity and anti-tumor effect in two murine syngeneic cancer models. We demonstrated that neoepitope DNA vaccination led to anti-tumor immunity in the CT26 and B16F10 tumor models, with the long-lasting presence of neoepitope-specific T-cell responses in blood, spleen, and tumors after immunization. We further observed that engagement of both the CD4+ and CD8+ T cell compartments was essential to hamper tumor growth. Additionally, combination therapy with immune checkpoint inhibition provided an additive effect, superior to either monotherapy. DNA vaccination offers a versatile platform that allows the encoding of multiple neoepitopes in a single formulation and is thus a feasible strategy for personalized immunotherapy via neoepitope vaccination.

Adenovirus Encoded Adjuvant (AdEnA) anti-CTLA-4, a novel strategy to improve Adenovirus based vaccines against infectious diseases and cancer

Introduction

Virus vectored genetic vaccines (Vvgv) represent a promising approach for eliciting immune protection against infectious diseases and cancer. However, at variance with classical vaccines to date, no adjuvant has been combined with clinically approved genetic vaccines, possibly due to the detrimental effect of the adjuvant-induced innate response on the expression driven by the genetic vaccine vector. We reasoned that a potential novel approach to develop adjuvants for genetic vaccines would be to "synchronize" in time and space the activity of the adjuvant with that of the vaccine.

Methods

To this aim, we generated an Adenovirus vector encoding a murine anti-CTLA-4 monoclonal antibody (Ad-9D9) as a genetic adjuvant for Adenovirus based vaccines.

Results

The co-delivery of Ad-9D9 with an Adeno-based COVID-19 vaccine encoding the Spike protein resulted in stronger cellular and humoral immune responses. In contrast, only a modest adjuvant effect was achieved when combining the vaccine with the same anti-CTLA-4 in its proteinaceous form. Importantly, the administration of the adjuvant vector at different sites of the vaccine vector abrogates the immunostimulatory effect. We showed that the adjuvant activity of Ad-α-CTLA-4 is independent from the vaccine antigen as it improved the immune response and efficacy of an Adenovirus based polyepitope vaccine encoding tumor neoantigens.

Discussion

Our study demonstrated that the combination of Adenovirus Encoded Adjuvant (AdEnA) with an Adeno-encoded antigen vaccine enhances immune responses to viral and tumor antigens, representing a potent approach to develop more effective genetic vaccines.

Neoantigen vaccination augments antitumor effects of anti-PD-1 on mouse hepatocellular carcinoma

Immune checkpoint inhibitors are groundbreaking resources for cancer therapy. However, only a few patients with hepatocellular carcinoma (HCC) have shown positive responses to anti-PD-1 therapy. Neoantigens are sequence-altered proteins resulting from somatic mutations in cancer. This study identified the neoantigens of Hep-55.1C and Dt81 Hepa1-6 HCCs by comparing their whole exome sequences with those of a normal C57BL/6 mouse liver. Immunogenic long peptides were pooled as peptide vaccines. The vaccination elicited tumor-reactive immune responses in C57BL/6 mice, as demonstrated by IFN-γ ELISPOT and an in vitro killing assay of splenocytes. In the treatment of three mouse HCC models, combined neoantigen vaccination and anti-PD-1 resulted in more significant tumor regression than monotherapies. Flow cytometry of the tumor-infiltrating lymphocytes showed decreased Treg cells and monocytic myeloid-derived suppressor cells, increased CD8⁺ T cells, enhanced granzyme B expression, and reduced exhaustion-related markers PD-1 and Lag-3 on CD8⁺ T cells in the combination group. These findings provide a strong rationale for conducting clinical studies of using neoantigen vaccination in combination with anti-PD-1 to treat patients with HCC.

Viral vectored vaccines: design, development, preventive and therapeutic applications in human diseases

Human diseases, particularly infectious diseases and cancers, pose unprecedented challenges to public health security and the global economy. The development and distribution of novel prophylactic and therapeutic vaccines are the prioritized countermeasures of human disease. Among all vaccine platforms, viral vector vaccines offer distinguished advantages and represent prominent choices for pathogens that have hampered control efforts based on conventional vaccine approaches. Currently, viral vector vaccines remain one of the best strategies for induction of robust humoral and cellular immunity against human diseases. Numerous viruses of different families and origins, including vesicular stomatitis virus, rabies virus, parainfluenza virus, measles virus, Newcastle disease virus, influenza virus, adenovirus and poxvirus, are deemed to be prominent viral vectors that differ in structural characteristics, design strategy, antigen presentation capability, immunogenicity and protective efficacy. This review summarized the overall profile of the design strategies, progress in advance and steps taken to address barriers to the deployment of these viral vector vaccines, simultaneously highlighting their potential for mucosal delivery, therapeutic application in cancer as well as other key aspects concerning the rational application of these viral vector vaccines. Appropriate and accurate technological advances in viral vector vaccines would consolidate their position as a leading approach to accelerate breakthroughs in novel vaccines and facilitate a rapid response to public health emergencies.

An Endogenous Retrovirus Vaccine Encoding an Envelope with a Mutated Immunosuppressive Domain in Combination with Anti-PD1 Treatment Eradicates Established Tumours in Mice

Endogenous retroviruses (ERVs) account for 8% of our genome, and, although they are usually silent in healthy tissues, they become reactivated and expressed in pathological conditions such as cancer. Several studies support a functional role of ERVs in tumour development and progression, specifically through their envelope (Env) protein, which contains a region described as an immunosuppressive domain (ISD). We have previously shown that targeting of the murine ERV (MelARV) Env using virus-like vaccine (VLV) technology, consisting of an adenoviral vector encoding virus-like particles (VLPs), induces protection against small tumours in mice. Here, we investigate the potency and efficacy of a novel MelARV VLV with a mutated ISD (ISDmut) that can modify the properties of the adenoviral vaccine-encoded Env protein. We show that the modification of the vaccine's ISD significantly enhanced T-cell immunogenicity in both prime and prime-boost vaccination regimens. The modified VLV in combination with an α-PD1 checkpoint inhibitor (CPI) exhibited excellent curative efficacy against large established colorectal CT26 tumours in mice. Furthermore, only ISDmut-vaccinated mice that survived CT26 challenge were additionally protected against rechallenge with a triple-negative breast cancer cell line (4T1), showing that our modified VLV provides cross-protection against different tumour types expressing ERV-derived antigens. We envision that translating these findings and technology into human ERVs (HERVs) could provide new treatment opportunities for cancer patients with unmet medical needs.

Integrating immunopeptidome analysis for the design and development of cancer vaccines

The repertoire of naturally presented peptides within the MHC (major histocompatibility complex) or HLA (human leukocyte antigens) system on the cellular surface of every mammalian cell is referred to as ligandome or immunopeptidome. This later gained momentum upon the discovery of CD8 + T cells able to recognize and kill cancer cells in an MHC-I antigen-restricted manner. Indeed, cancer immune surveillance relies on T cell recognition of MHC-I-restricted peptides, making the identification of those peptides the core for designing T cell-based cancer vaccines. Moreover, the breakthrough of antibodies targeting immune checkpoint molecules has led to a new and strong interest in discovering suitable targets for CD8 +T cells. Therapeutic cancer vaccines are designed for the artificial generation and/or stimulation of CD8 +T cells; thus, their combination with ICIs to unleash the breaks of the immune system comes as a natural consequence to enhance anti-tumor efficacy. In this context, the identification and knowledge of peptide candidates take advantage of the fast technology updates in immunopeptidome and mass spectrometric methodologies, paying the way to the rational design of vaccines for immunotherapeutic approaches. In this review, we discuss mainly the role of immunopeptidome analysis and its application for the generation of therapeutic cancer vaccines with main focus on HLA-I peptides. Here, we review cancer vaccine platforms based on two different preparation methods: pathogens (viruses and bacteria) and not (VLPs, nanoparticles, subunits vaccines) that exploit discoveries in the ligandome field to generate and/or enhance anti-tumor specific response. Finally, we discuss possible drawbacks and future challenges in the field that remain still to be addressed.

Immunotherapy for HER-2 positive breast cancer

Immunotherapy is a developing treatment for advanced breast cancer. Immunotherapy has clinical significance for the treatment of triple-negative breast cancers and human epidermal growth factor receptor-2 positive (HER2+) breast cancers. As a proved effective passive immunotherapy, clinical application of the monoclonal antibodies trastuzumab, pertuzumab and T-DM1 (ado-trastuzumab emtansine) has significantly improved the survival of patients with HER2+ breast cancers. Immune checkpoint inhibitors that block programmed death receptor-1 and its ligand (PD-1/PD-L1) have also shown benefits for breast cancer in various clinical trials. Adoptive T-cell immunotherapies and tumor vaccines are emerging as novel approaches to treating breast cancer, but require further study. This article reviews recent advances in immunotherapy for HER2+ breast cancers.

Getting personal in metastatic melanoma: neoantigen-based vaccines as a new therapeutic strategy

PURPOSE OF REVIEW

Cancer vaccines are facing renewed interest, thanks to the progress recently achieved in the immunotherapy field, including the success of immune checkpoint inhibitors (CPIs). The advances in understanding the CPI mode of action revealed a central role of neoantigens for the outcome of such treatments. Neoantigens became the preferred antigens for cancer vaccines and have been evaluated in several clinical trials. Here, we review the recent results from neoantigen-based vaccines in melanoma patients and discuss avenues for improvement.

RECENT FINDINGS

The importance of neoantigens for tumor control comes from the positive correlation between tumor mutational burden (TMB) and response to CPI. Preclinical studies have proved the effectiveness of neoantigen vaccines in models, expediting their clinical testing. Tumor mutations are not shared in most tumor types including melanoma, mandating the need of a personalized approach. Several clinical studies have shown the safety, feasibility, immunogenicity and preliminary evidence of antitumor activity of personalized vaccination. Currently, new trials have been started aiming to both confirm clinical activity and combining vaccines with other immunotherapies for improved efficacy.

SUMMARY

Personalized vaccines hold the promise for highly mutated and immunogenic cancers, including melanoma. Continuous efforts are underway to increase their likelihood of success.

Challenges in neoantigen-directed therapeutics

A fundamental prerequisite for the efficacy of cancer immunotherapy is the presence of functional, antigen-specific T cells within the tumor. Neoantigen-directed therapy is a promising strategy that aims at targeting the host's immune response against tumor-specific antigens, thereby eradicating cancer cells. Initial forays have been made in clinical environments utilizing vaccines and adoptive cell therapy; however, many challenges lie ahead. We provide an in-depth overview of the current state of the field with an emphasis on in silico neoantigen discovery and the clinical aspects that need to be addressed to unlock the full potential of this therapy.

A Novel Engineered AAV-Based Neoantigen Vaccine in Combination with Radiotherapy Eradicates Tumors

The potency of tumor-specific antigen (TSA) vaccines, such as neoantigen (neoAg)-based cancer vaccines, can be compromised by host immune checkpoint inhibitory mechanisms, such as programmed cell death protein 1 (PD-1)/programmed death ligand 1 (PD-L1), that attenuate neoAg presentation on dendritic cells (DC) and hinder T cell-mediated cytotoxicity. To overcome PD-1/PD-L1 inhibition in DCs, we developed a novel adeno-associated virus (meAAV) neoAg vaccine, modified with TLR9 inhibitory fragments, PD-1 trap, and PD-L1 miRNA, which extend the persistence of meAAV and activate neoAg-specific T-cell responses in immune-competent colorectal and breast cancer murine models. Moreover, we found that in combination with radiotherapy, the meAAV-based neoAg cancer vaccine not only elicited higher antigen presentation ability, but also maintained neoAg-specific cytotoxic T lymphocyte (CTL) responses. These functional PD-1 traps and PD-L1 miRNAs overcome host PD-1/PD-L1 inhibitory mechanisms and boost the therapeutic efficacy of radiotherapy. More importantly, combined radiotherapy and meAAV neoAg cancer vaccines significantly enhanced neoAg-specific CTL responses, increased CTL infiltration in tumor microenvironment, and decreased tumor-associated immunosuppression. This process led to the complete elimination of colorectal cancer and delayed tumor growth of breast cancer in tumor-bearing mice. Taken together, our results demonstrated a novel strategy that combines neoAg cancer vaccine and radiotherapy to increase the therapeutic efficacy against colorectal and breast cancers.

Full Remission of CAR-Deficient Tumors by DOTAP-Folate Liposome Encapsulation of Adenovirus

Adenovirus (Ad)-based vectors have shown considerable promise for gene therapy. However, Ad requires the coxsackievirus and adenovirus receptor (CAR) to enter cells efficiently and low CAR expression is found in many human cancers, which hinder adenoviral gene therapies. Here, cationic 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP)-folate liposomes (Df) encapsulating replication-deficient Ad were synthesized, which showed improved transfection efficiency in various CAR-deficient cell lines, including epithelial and hematopoietic cell types. When encapsulating replication-competent oncolytic Ad (TAV255) in DOTAP-folate liposome (TAV255-Df), the adenoviral structural protein, hexon, was readily produced in CAR-deficient cells, and the tumor cell killing ability was 5× higher than that of the non-encapsulated Ad. In CAR-deficient CT26 colon carcinoma murine models, replication-competent TAV255-Df treatment of subcutaneous tumors by intratumoral injection resulted in 67% full tumor remission, prolonged survival, and anti-cancer immunity when mice were rechallenged with cancer cells with no further treatment. The preclinical data shows that DOTAP-folate liposomes could significantly enhance the transfection efficiency of Ad in CAR-deficient cells and, therefore, could be a feasible strategy for applications in cancer treatment.

Engineering neoantigen vaccines to improve cancer personalized immunotherapy

Immunotherapy treatments harnessing the immune system herald a new era of personalized medicine, offering considerable benefits for cancer patients. Over the past years, tumor neoantigens emerged as a rising star in immunotherapy. Neoantigens are tumor-specific antigens arising from somatic mutations, which are proceeded and presented by the major histocompatibility complex on the cell surface. With the advancement of sequencing technology and bioinformatics engineering, the recognition of neoantigens has accelerated and is expected to be incorporated into the clinical routine. Currently, tumor vaccines against neoantigens mainly encompass peptides, DNA, RNA, and dendritic cells, which are extremely specific to individual patients. Due to the high immunogenicity of neoantigens, tumor vaccines could activate and expand antigen-specific CD4+ and CD8+ T cells to intensify anti-tumor immunity. Herein, we introduce the origin and prediction of neoantigens and compare the advantages and disadvantages of multiple types of neoantigen vaccines. Besides, we review the immunizations and the current clinical research status in neoantigen vaccines, and outline strategies for enhancing the efficacy of neoantigen vaccines. Finally, we present the challenges facing the application of neoantigens.

Adenoviral-based vaccine promotes neoantigen-specific CD8+ T cell stemness and tumor rejection

Upon chronic antigen exposure, CD8⁺ T cells become exhausted, acquiring a dysfunctional state correlated with the inability to control infection or tumor progression. In contrast, stem-like CD8⁺ T progenitors maintain the ability to promote and sustain effective immunity. Adenovirus (Ad)-vectored vaccines encoding tumor neoantigens have been shown to eradicate large tumors when combined with anti-programmed cell death protein 1 (αPD-1) in murine models; however, the mechanisms and translational potential have not yet been elucidated. Here, we show that gorilla Ad vaccine targeting tumor neoepitopes enhances responses to αPD-1 therapy by improving immunogenicity and antitumor efficacy. Single-cell RNA sequencing demonstrated that the combination of Ad vaccine and αPD-1 increased the number of murine polyfunctional neoantigen-specific CD8⁺ T cells over αPD-1 monotherapy, with an accumulation of Tcf1⁺ stem-like progenitors in draining lymph nodes and effector CD8⁺ T cells in tumors. Combined T cell receptor (TCR) sequencing analysis highlighted a broader spectrum of neoantigen-specific CD8⁺ T cells upon vaccination compared to αPD-1 monotherapy. The translational relevance of these data is supported by results obtained in the first 12 patients with metastatic deficient mismatch repair (dMMR) tumors vaccinated with an Ad vaccine encoding shared neoantigens. Expansion and diversification of TCRs were observed in post-treatment biopsies of patients with clinical response, as well as an increase in tumor-infiltrating T cells with an effector memory signature. These findings indicate a promising mechanism to overcome resistance to PD-1 blockade by promoting immunogenicity and broadening the spectrum and magnitude of neoantigen-specific T cells infiltrating tumors.

Oncolytic viruses combined with immune checkpoint therapy for colorectal cancer is a promising treatment option

Immunotherapy is one of the promising strategies in the treatment of oncology. Immune checkpoint inhibitors, as a type of immunotherapy, have no significant efficacy in the clinical treatment of patients with pMMR/MSS/MSI-L mCRC alone. Therefore, there is an urgent need to find combination therapies that can improve the response rate of immune checkpoint inhibitors. Oncolytic viruses are a new class of cancer drugs that, in addition to directly lysing tumor cells, can facilitate the action of immune checkpoint inhibitors by modulating the tumor microenvironment and transforming “cold” tumors into “hot” ones. The combination of oncolytic viruses and immune checkpoint inhibitors is currently being used in several primary and clinical studies to treat tumors with exciting results. The combination of genetically modified “armed” OV with ICIs is expected to be one of the treatment options for pMMR/MSS/MSI-L mCRC. In this paper, we will analyze the current status of oncolytic viruses and ICIs available for the treatment of CRC. The feasibility of OV in combination with ICI for CRC will be discussed in terms of the mechanism of action of OV in treating tumors.

Tumor-targeted nano-delivery system of therapeutic RNA

The birth of RNAi technology has pioneered actionability at the molecular level. Compared to DNA, RNA is less stable and therefore requires more demanding delivery vehicles. With their flexible size, shape, structure, and accessible surface modification, non-viral vectors show great promise for application in RNA delivery. Different non-viral vectors have different ways of binding to RNA. Low immunotoxicity gives RNA significant advantages in tumor treatment. However, the delivery of RNA still has many limitations in vivo. This manuscript summarizes the size-targeting dependence of different organs, followed by a summary of nanovesicles currently in or undergoing clinical trials. It also reviews all RNA delivery systems involved in the current study, including natural, bionic, organic, and inorganic systems. It summarizes the advantages and disadvantages of different delivery methods, which will be helpful for future RNA vehicle design. It is hoped that this will be helpful for gene therapy of clinical tumors.

Identification of neoantigens for individualized therapeutic cancer vaccines

Somatic mutations in cancer cells can generate tumour-specific neoepitopes, which are recognized by autologous T cells in the host. As neoepitopes are not subject to central immune tolerance and are not expressed in healthy tissues, they are attractive targets for therapeutic cancer vaccines. Because the vast majority of cancer mutations are unique to the individual patient, harnessing the full potential of this rich source of targets requires individualized treatment approaches. Many computational algorithms and machine-learning tools have been developed to identify mutations in sequence data, to prioritize those that are more likely to be recognized by T cells and to design tailored vaccines for every patient. In this Review, we fill the gaps between the understanding of basic mechanisms of T cell recognition of neoantigens and the computational approaches for discovery of somatic mutations and neoantigen prediction for cancer immunotherapy. We present a new classification of neoantigens, distinguishing between guarding, restrained and ignored neoantigens, based on how they confer proficient antitumour immunity in a given clinical context. Such context-based differentiation will contribute to a framework that connects neoantigen biology to the clinical setting and medical peculiarities of cancer, and will enable future neoantigen-based therapies to provide greater clinical benefit.

Neoantigen cancer vaccine augments anti-CTLA-4 efficacy

Immune checkpoint inhibitors (ICI) based on anti-CTLA-4 (αCTLA-4) and anti-PD1 (αPD1) are being tested in combination with different therapeutic approaches including other immunotherapies such as neoantigen cancer vaccines (NCV). Here we explored, in two cancer murine models, different therapeutic combinations of ICI with personalized DNA vaccines expressing neoantigens and delivered by electroporation (EP). Anti-cancer efficacy was evaluated using vaccines with or without CD4 epitopes. Therapeutic DNA vaccines showed synergistic effects in different therapeutic protocols including established large tumors. Flow cytometry (FC) was utilized to measure CD8, CD4, Treg, and switched B cells as well as neoantigen-specific immune responses, which were also measured by IFN-γ ELIspot. Immune responses were augmented in combination with αCTLA4 but not with αPD1 in the MC38 tumor-bearing mice, significantly impacting tumor growth. Similarly, neoantigen-specific T cell immune responses were enhanced in combined treatment with αCTLA-4 in the CT26 tumor model where large tumors regressed in all mice, while monotherapy with αCTLA-4 was less efficacious. In line with previous evidence, we observed an increased switched B cells in the spleen of mice treated with αCTLA-4 alone or in combination with NCV. These results support the use of NCV delivered by DNA-EP with αCTLA-4 and suggest a new combined therapy for clinical testing.

Systemic immune responses to irradiated tumours via the transport of antigens to the tumour periphery by injected flagellate bacteria

Because the tumour microenvironment is typically immunosuppressive, the release of tumour antigens mediated by radiotherapy or chemotherapy does not sufficiently activate immune responses. Here we show that, following radiotherapy, the intratumoural injection of a genetically attenuated strain of Salmonella coated with antigen-adsorbing cationic polymer nanoparticles caused the accumulation of tumour antigens at the tumour's periphery. This enhanced the crosstalk between the antigens and dendritic cells, and resulted in large increases in activated ovalbumin-specific dendritic cells in vitro and in systemic antitumour effects, and extended survival in multiple tumour models in mice, including a model of metastasis and recurrence. The antitumour effects were abrogated by the antibody-mediated depletion of CD8⁺ T cells, indicating that systemic tumour regression was caused by adaptive immune responses. Leveraging flagellate bacteria to transport tumour antigens to the periphery of tumours to potentiate the activation of dendritic cells may open up new strategies for in situ cancer vaccination.

Personalized therapy with peptide-based neoantigen vaccine (EVX-01) including a novel adjuvant, CAF®09b, in patients with metastatic melanoma

The majority of neoantigens arise from unique mutations that are not shared between individual patients, making neoantigen-directed immunotherapy a fully personalized treatment approach. Novel technical advances in next-generation sequencing of tumor samples and artificial intelligence (AI) allow fast and systematic prediction of tumor neoantigens. This study investigates feasibility, safety, immunity, and anti-tumor potential of the personalized peptide-based neoantigen vaccine, EVX-01, including the novel CD8⁺ T-cell inducing adjuvant, CAF®09b, in patients with metastatic melanoma (NTC03715985). The AI platform PIONEER^TM was used for identification of tumor-derived neoantigens to be included in a peptide-based personalized therapeutic cancer vaccine. EVX-01 immunotherapy consisted of 6 administrations with 5–10 PIONEER^TM-predicted neoantigens as synthetic peptides combined with the novel liposome-based Cationic Adjuvant Formulation 09b (CAF®09b) to strengthen T-cell responses. EVX-01 was combined with immune checkpoint inhibitors to augment the activity of EVX-01-induced immune responses. The primary endpoint was safety, exploratory endpoints included feasibility, immunologic and objective responses. This interim analysis reports the results from the first dose-level cohort of five patients. We documented a short vaccine manufacturing time of 48–55 days which enabled the initiation of EVX-01 treatment within 60 days from baseline biopsy. No severe adverse events were observed. EVX-01 elicited long-lasting EVX-01-specific T-cell responses in all patients. Competitive manufacturing time was demonstrated. EVX-01 was shown to be safe and able to elicit immune responses targeting tumor neoantigens with encouraging early indications of a clinical and meaningful antitumor efficacy, warranting further study.