Synthetic Peptide Vaccine Research Articles

Peptide Vaccines in Cancer Immunotherapy

Traditional cancer treatment is based on surgery, supplemented by chemotherapy and radiotherapy. In recent years, new treatment options, such as targeted therapy, have gradually entered the clinic. However, for some patients who are inoperable or have metastasized, there are currently no sufficiently effective therapies to support long-term survival. Peptide vaccines are autoimmune system-based therapies that typically target the uptake of tumor antigens by antigen-presenting cells (APCs). Current clinical trials of peptide vaccines primarily target tumor-associated or tumor-specific antigens (TAAs or TSAs) and can be classified into two types: synthetic peptide vaccines and peptide vaccines derived from whole tumor cells. Although the peptide vaccines that have been reported are promising, the tumor microenvironment (TME) is a significant obstacle to the effectiveness of cancer immunotherapy. Using peptide vaccines as a future treatment for inoperable tumors, surgical follow-up, and as a complement to other treatments such as immune checkpoint inhibitors, tyrosine kinase inhibitors, chemotherapy, and radiotherapy is a possibility. This study aims to examine the various types and clinical applications of peptide-based therapeutic vaccines, which may offer significant insights into the current and future development of these vaccines.

Neoantigen landscape supports feasibility of personalized cancer vaccine for follicular lymphoma

AbstractPersonalized cancer vaccines designed to target neoantigens represent a promising new treatment paradigm in oncology. In contrast to classical idiotype vaccines, we hypothesized that “polyvalent” vaccines could be engineered for the personalized treatment of follicular lymphoma (FL) using neoantigen discovery by combined whole-exome sequencing (WES) and RNA sequencing (RNA-seq). Fifty-eight tumor samples from 57 patients with FL underwent WES and RNA-seq. Somatic and B-cell clonotype neoantigens were predicted and filtered to identify high-quality neoantigens. B-cell clonality was determined by the alignment of B-cell receptor (BCR) CDR3 regions from RNA-seq data, grouping at the protein level, and comparison with the BCR repertoire from healthy individuals using RNA-seq data. An average of 52 somatic mutations per patient (range, 2-172) were identified, and ≥2 (median, 15) high-quality neoantigens were predicted for 56 of 58 FL samples. The predicted neoantigen peptides were composed of missense mutations (77%), indels (9%), gene fusions (3%), and BCR sequences (11%). Building off of these preclinical analyses, we initiated a pilot clinical trial using personalized neoantigen vaccination combined with PD-1 blockade in patients with relapsed or refractory FL (#NCT03121677). Synthetic long peptide vaccines targeting predicted high-quality neoantigens were successfully synthesized for and administered to all 4 patients enrolled. Initial results demonstrate feasibility, safety, and potential immunologic and clinical responses. Our study suggests that a genomics-driven personalized cancer vaccine strategy is feasible for patients with FL, and this may overcome prior challenges in the field. This trial was registered at www.ClinicalTrials.gov as #NCT03121677.

Abstract CT022: Mutant KRAS peptide-based vaccine in patients at high risk of developing pancreatic cancer: Preliminary analysis from a phase I study

Abstract Background: The development of pancreatic ductal adenocarcinoma (PDAC) from the first driver event takes >10 years, providing a unique window of opportunity for early interception. As a frequent alteration identified in both PDAC and pancreatic premalignancy, mutant KRAS (mKRAS) has emerged as a potential target for immune-based interception strategies in individuals at high risk of developing pancreatic cancer. Methods: This is a single-arm, open-label, second-in-human phase I study of a pooled synthetic long peptide (SLP) vaccine with poly-ICLC adjuvant targeting up to six mKRAS subtypes (G12D, G12R, G12V, G12A, G12C, G13D) in patients with hereditary predisposition to developing PDAC (NCT05013216). Key inclusion: radiographic evidence of a pancreatic abnormality and eligibility under at least one of three high-risk groups based on family history of PDAC and/or germline mutation status. Vaccination schema: mKRAS vaccine given on weeks 1, 3, 5, and 13. Peripheral blood collected at baseline and weeks 5, 13, and 17 for analysis of immunogenicity by IFN-gamma ELISpot. Co-primary endpoints: safety and mKRAS-specific T cell response. Results: At the time of data cutoff (November 15, 2023), 15 out of 20 planned patients were vaccinated on study and evaluable for immunogenicity. All 15 patients achieved a mKRAS-specific T cell response, defined by the maximal fold change in the pooled average IFN-gamma-producing mKRAS-specific T cell density within 17 weeks post-vaccination (median: 12.3, range: 3.1-167). Differential immunogenicity elicited by individual mKRAS epitopes was noted in this cohort. Specifically, the mKRAS G12V peptide induced the highest fold change increase in antigen-specific T cell expansion (median: 32.6, range: 2.9-243) while the mKRAS G12D peptide was the least immunogenic (median: 7.6, range: 0.4-104). Regarding safety, all adverse events were grade 1 or grade 2 in severity per NCI CTCAE v5.0. The most frequent vaccine-related adverse events were injection site reactions (93.8%), fatigue (62.5%), chills (43.8%), and headache (37.5%). No safety signals were observed. Conclusions: For the first time, we demonstrate mKRAS-specific T cell responses induced by vaccination in a cohort of high-risk individuals with inherited predisposition to PDAC. These findings directly serve as proof-of-concept to advance vaccine strategies focused on intercepting the development of pancreatic cancer in high-risk populations. Support: Stand Up To Cancer, Lustgarten Foundation, and NIH/NCI. Citation Format: Saurav D. Haldar, Amanda Huff, Elizabeth Abou Diwan, Anna Ferguson, Carol Judkins, Jiayun Lu, Hao Wang, Hassan Sinan, Christopher Thoburn, Katherine M. Bever, Mark Yarchoan, Amy M. Thomas, Julie M. Nauroth, Daniel A. Laheru, Michael G. Goggins, Elizabeth M. Jaffee, Nilofer S. Azad, Neeha Zaidi. Mutant KRAS peptide-based vaccine in patients at high risk of developing pancreatic cancer: Preliminary analysis from a phase I study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT022.

Abstract 4106: A novel synthetic long peptide vaccine composition targeting multiple PD-L1 T-cell epitopes exhibits anti-tumor efficacy in a syngeneic mouse colorectal cancer model

Abstract Background Cancer immunotherapy targeting immune checkpoints has shown promising clinical anti-tumor efficacy over the past decades. Monoclonal antibodies against PD-1 or PD-L1 have demonstrated clinical efficacy in a wide spectrum of cancer types. Despite the clinical success of therapies using immune checkpoint inhibitors (ICI), only a subset of patients shows long-lasting tumor remission, while resistance and toxicities to these agents remain to be addressed. This supports the need to explore alternative immunotherapeutic approaches or additional therapies for synergistic combinations to augment the anti-tumor efficacy for cancer patients receiving ICI therapies. Methods As an active immunotherapy approach, we developed a blend of four novel synthetic peptide vaccines each containing one PD-L1 T-cell epitope with individual covalent conjugation of the carrier protein, keyhole limpet haemocyanin (KLH), which is to break immune tolerance towards self-molecules. The four PD-L1 epitopes range from 30 to 40 amino acids in length, which target different domains of mouse PD-L1 protein. The PD-L1 peptides were synthesized using the technique of solid-phase peptide synthesis and purified by high performance liquid chromatography. All naked peptides were conjugated to KLH protein by thiol-maleimide reaction, followed by dialysis for purification. The peptide vaccines were formulated with a Toll-like receptor 9 agonist CpG ODN 1826 and aluminum hydroxide gel for animal immunization. Results These synthetic long PD-L1 peptide vaccines are highly immunogenic in a syngeneic BALB/c mouse model for a cell-mediated immune response when admixed and formulated with adjuvants. The vaccine composition is well tolerated by the mice with no evidence of toxicity and autoimmunity. In vivo administration of the vaccine formulation can elicit a positive PD-L1-specific T cell response in splenocytes with an IFN-γ ELISPOT assay. Moreover, in vivo vaccination of these PD-L1 peptide vaccines in a CT26 syngeneic mouse preventive colorectal cancer model exhibits a potent anti-tumor activity, with a 54% tumor growth inhibition (p<0.001) in tumor volume compared to that of the adjuvant-control group at the end of the study. Conclusions Taken together, our data demonstrate a proof-of-concept that T cell-based PD-L1 peptide vaccines are a promising therapeutic strategy for inducing anti-tumor immunity to combat cancers. Citation Format: Kenneth Nansheng Lin, Melvin Toh. A novel synthetic long peptide vaccine composition targeting multiple PD-L1 T-cell epitopes exhibits anti-tumor efficacy in a syngeneic mouse colorectal cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4106.

Safety and immunogenicity of a synthetic nanoparticle-based, T cell priming peptide vaccine against dengue in healthy adults in Switzerland: a double-blind, randomized, vehicle-controlled, phase 1 study

Vaccines that minimize the risk of vaccine-induced antibody-dependent enhancement and severe dengue are needed to address the global health threat posed by dengue. This study assessed the safety and immunogenicity of a gold nanoparticle (GNP)-based, multi-valent, synthetic peptide dengue vaccine candidate (PepGNP-Dengue), designed to provide protective CD8+ T cell immunity, without inducing antibodies. In this randomized, double-blind, vehicle-controlled, phase 1 trial (NCT04935801), healthy naïve individuals aged 18-45 years recruited at the Centre for primary care and public health, Lausanne, Switzerland, were randomly assigned to receive PepGNP-Dengue or comparator (GNP without peptides [vehicle-GNP]). Randomization was stratified into four groups (low dose [LD] and high dose [HD]), allocation was double-blind from participants and investigators. Two doses were administered by intradermal microneedle injection 21 days apart. Primary outcome was safety, secondary outcome immunogenicity. Analysis was by intention-to-treat for safety, intention-to-treat and per protocol for immunogenicity. 26 participants were enrolled (August-September 2021) to receive PepGNP-Dengue (LD or HD, n=10 each) or vehicle-GNP (LD or HD, n=3 each). No vaccine-related serious adverse events occurred. Most (90%) related adverse events were mild; injection site pain and transient discoloration were most frequently reported. Injection site erythema occurred in 58% of participants. As expected, PepGNP-Dengue did not elicit anti-DENV antibodies of significance. Significant increases were observed in specific CD8+ T cells and dengue dextramer+memory cell subsets in the LD PepGNP-Dengue but not in the HD PepGNP-Dengue or vehicle-GNP groups, specifically PepGNP-activated CD137+CD69+CD8+ T cells (day 90,+0.0318%, 95% CI: 0.0088-0.1723, p=0.046), differentiated effector memory (TemRA) and central memory (Tcm) CD8+ T cells (day 35,+0.8/105 CD8+, 95% CI: 0.19-5.13, p=0.014 and +1.34/105 CD8+, 95% CI: 0.1-7.34, p=0.024, respectively). Results provide proof of concept that a synthetic nanoparticle-based peptide vaccine can successfully induce virus-specific CD8+ T cells. The favourable safety profile and cellular responses observed support further development of PepGNP-Dengue. Emergex Vaccines Holding Limited.

Identification of pan-cancer/testis genes and validation of therapeutic targeting in triple-negative breast cancer: Lin28a-based and Siglece-based vaccination induces antitumor immunity and inhibits metastasis

BackgroundCancer–testis (CT) genes are targets for tumor antigen-specific immunotherapy given that their expression is normally restricted to the immune-privileged testis in healthy individuals with aberrant expression in tumor tissues. While...

Abstract B004: Neoantigen adenoviral cancer vaccine generates improved CD8+ T-cell responses compared to adjuvanted peptide vaccine

Abstract Development of large, functional CD8+ T cell responses is crucial for successful cancer vaccine therapeutics. Neoantigens have demonstrated their potential as cancer vaccine immunogens, but improvements in delivery method are still necessary. In this work, we characterized five candidate Adenovirus Serotype 26 (Ad26) cancer vaccines for prophylactic efficacy in the MC-38 cancer model. All five single shot vaccines generated cellular immune responses at a higher level than prime boost peptide vaccination. The vaccines generated varying degrees of protection against tumor growth. The best Ad26 vaccine candidates showed improved protection compared to long synthetic peptide vaccines containing the same immunogens, the current standard in the field. Ad26 expressing seven neoantigens conjugated to the Herpes Viral Protein 22 (VP22) (Ad26.VP22.7Epi) was found to reduce tumor growth the most. Ad26.VP227Epi was compared to peptide vaccination in immune recall post challenge studies, in both the spleen and the tumor. Both Ad26.VP22.7Epi and Peptide showed a clear recall response after challenge in the spleen. This response was primarily focused on the Adpgk neoantigen but Ad26.VP22.7Epi additionally induced responses to the Irgq neoantigen while the peptide vaccine had stronger responses against the Reps1 neoantigen. The Ad26.VP227Epi vaccine generated increased numbers of infiltrating CD8+ T-cells, IFN+ CD8+ T-cells, and CD107a+ CD8+ T-cells, which all correlated with reduced tumor growth. We used single cell RNA-seq (scRNA-seq) to characterize tumor infiltrating lymphocyte populations (defined as CD45+) generated by the two platforms. We found that both Ad26.VP22.7Epi and Peptide induced higher numbers of infiltrating CD8+ T-cells within the tumor as compared to Sham. Single-cell analysis also showed higher numbers of tumor infiltrating Tregs in peptide vaccinated mice. Higher numbers of CD8+ T-cells correlated with protection as expected but interestingly increased numbers of Tregs positively correlated with tumor volume only among vaccinated mice, which could further explain differences between Ad vector and peptide vaccination. Differential gene expression analysis of CD8+ T-cells showed an upregulation of Th1 pathways and general T cell activation when comparing Ad vector vaccinated mice to peptide vaccinated. Peptide vaccinated CD8+ T-cells showed upregulation in the IL-10 pathway, potentially caused by an increased Tregs. Further investigation of these differences among CD8+ T cell and Treg populations could further elucidate potential mechanisms explaining the differences in platform efficacy. Citation Format: Gabriel Dagotto, Alessandro Colarusso, Robert Patio, David Li, Tochi Anioke, Victoria Giffin, Malika Aid, Dan Barouch. Neoantigen adenoviral cancer vaccine generates improved CD8+ T-cell responses compared to adjuvanted peptide vaccine [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2023 Oct 1-4; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2023;11(12 Suppl):Abstract nr B004.

In Vivo Validation of Novel Synthetic tbp1 Peptide-Based Vaccine Candidates against Haemophilus influenzae Strains in BALB/c Mice.

Haemophilus influenzae is a Gram-negative bacterium characterized as a small, nonmotile, facultative anaerobic coccobacillus. It is a common cause of a variety of invasive and non-invasive infections. Among six serotypes (a-f), H. influenzae type b (Hib) is the most familiar and predominant mostly in children and immunocompromised individuals. Following Hib vaccination, infections due to other serotypes have increased in number, and currently, there is no suitable effective vaccine to induce cross-strain protective antibody responses. The current study was aimed to validate the capability of two 20-mer highly conserved synthetic tbp1 (transferrin-binding protein 1) peptide-based vaccine candidates (tbp1-E1 and tbp1-E2) predicted using in silico approaches to induce immune responses against H. influenzae strains. Cytokine induction ability, immune simulations, and molecular dynamics (MD) simulations were performed to confirm the candidacy of epitopic docked complexes. Synthetic peptide vaccine formulations in combination with two different adjuvants, BGs (Bacterial Ghosts) and CFA/IFA (complete/incomplete Freund's adjuvant), were used in BALB/c mouse groups in three booster shots at two-week intervals. An indirect ELISA was performed to determine endpoint antibody titers using the Student's t-distribution method. The results revealed that the synergistic use of both peptides in combination with BG adjuvants produced better results. Significant differences in absorbance values were observed in comparison to the rest of the peptide-adjuvant combinations. The findings of this study indicate that these tbp1 peptide-based vaccine candidates may present a preliminary set of peptides for the development of an effective cross-strain vaccine against H. influenzae in the future due to their highly conserved nature.

Efficacy of a synthetic peptide Chlamydia pecorum major outer membrane protein vaccine in a wild koala (Phascolarctos cinereus) population

Chlamydiosis is a significant disease affecting Eastern Australian koala (Phascolarctos cinereus) populations, impacting individual animal welfare and fecundity and therefore influencing population dynamics. The aim of this study was to investigate the effect of a synthetic peptide vaccine based on 4 components of the Chlamydia pecorum major outer membrane protein (MOMP), over an 18-month period in a koala population severely impacted by chlamydiosis. Wild koalas were recruited into a vaccination or a placebo treatment group on a random allocation, then followed through a period of 18 months, with recapture at 6 monthly intervals. Vaccination did not alter clinical disease expression or chlamydial shedding from the ocular or urogenital sites. Vaccination did not stimulate a significant plasma anti-MOMP IgG response, when compared to the placebo group. There was no significant effect of vaccination on IFN-γ and IL-17A mRNA expression of peripheral blood lymphocytes when stimulated with rMOMP. We have demonstrated that a synthetic peptide vaccination against chlamydiosis is not an effective management tool in a koala population with a high prevalence of C. pecorum infection and related disease. The lack of antigenic response found in this study suggests that further research utilising a larger, full-length antigen is an avenue worth investigation if we are to consider vaccination as a part of a management strategy in diseased koala populations.

Therapeutic Vaccination against Human Papillomavirus Type 16 for the Treatment of High-Grade Anal Intraepithelial Neoplasia in HIV+ Men.

Anal cancer is increasing in HIV+ men who have sex with men (MSM). Treatment options for its precursor, high-grade anal intraepithelial neoplasia (HGAIN), are suboptimal. In this phase I to II dose-finding study, we assessed the safety and efficacy of the human papillomavirus type 16 (HPV16) synthetic long peptide vaccine (SLP-HPV-01) in HIV+ MSM with HPV16-positive HGAIN. Four dosage schedules (1-5-10; 5-10-20; 10-20-40; and 40-40-40-40 μg) of SLP-HPV-01 were administered intradermally with a 3-week interval in 10 patients per dose level (DL). In each dose group, 5 patients also received 1 μg/kg pegylated IFNα-2b subcutaneously. Primary endpoints were safety and regression of HGAIN at 3, 6, and 12 months. Eighty-one of 134 screened patients (60%) had HPV16-negative HGAIN lesions, leaving 53 eligible patients. Thirteen patients were excluded, leaving 40 men. The vaccine was well tolerated. One patient developed a generalized rash. The highest dosage level induced the strongest immune responses. There was no indication for stronger reactivity in the IFNα groups. Up to 18 months of follow-up, 8/38 intention-to-treat patients had a complete clinical and histologic response and one had a partial response (in total 9/38, 23.7%). At the highest dosage level, the clinical response was 4/10 (40%). Stronger immune responses were detected among clinical responders. The highest DL is safe, immunogenic, and associated with clinical responses to HPV16-induced lesions. However, as the majority of HGAIN is caused by the other HPV types, further studies should aim at pan-HPV vaccination to prevent or treat HGAIN.

Design of a Synthetic Long Peptide Vaccine Targeting HPV-16 and -18 Using Immunoinformatic Methods.

Human papillomavirus types 16 and 18 cause the majority of cervical cancers worldwide. Despite the availability of three prophylactic vaccines based on virus-like particles (VLP) of the major capsid protein (L1), these vaccines are unable to clear an existing infection. Such infected persons experience an increased risk of neoplastic transformation. To overcome this problem, this study proposes an alternative synthetic long peptide (SLP)-based vaccine for persons already infected, including those with precancerous lesions. This new vaccine was designed to stimulate both CD8+ and CD4+ T cells, providing a robust and long-lasting immune response. The SLP construct includes both HLA class I- and class II-restricted epitopes, identified from IEDB or predicted using NetMHCPan and NetMHCIIPan. None of the SLPs were allergenic nor toxic, based on in silico studies. Population coverage studies provided 98.18% coverage for class I epitopes and 99.81% coverage for class II peptides in the IEDB world population's allele set. Three-dimensional structure ab initio prediction using Rosetta provided good quality models, which were assessed using PROCHECK and QMEAN4. Molecular docking with toll-like receptor 2 identified potential intrinsic TLR2 agonist activity, while molecular dynamics studies of SLPs in water suggested good stability, with favorable thermodynamic properties.

Enhanced HPV16 E6/E7+ tumor eradication via induction of tumor-specific T cells by therapeutic vaccination with virosomes presenting synthetic long peptides

Therapeutic cancer vaccines trigger CD4 + and CD8 + T cell responses capable of established tumor eradication. Current platforms include DNA, mRNA and synthetic long peptide (SLP) vaccines, all aiming at robust T cell responses. SLPs linked to the Amplivant® adjuvant (Amplivant-SLP) have shown effective delivery to dendritic cells, resulting in improved immunogenicity in mice. We have now tested virosomes as a delivery vehicle for SLPs. Virosomes are nanoparticles made from influenza virus membranes and have been used as vaccines for a variety of antigens. Amplivant-SLP virosomes induced the expansion of more antigen-specific CD8 + T memory cells in ex vivo experiments with human PBMCs than Amplivant-SLP conjugates alone. The immune response could be further improved by including the adjuvants QS-21 and 3D-PHAD in the virosomal membrane. In these experiments, the SLPs were anchored in the membrane through the hydrophobic Amplivant adjuvant. In a therapeutic mouse model of HPV16 E6/E7+ cancer, mice were vaccinated with virosomes loaded with either Amplivant-conjugated SLPs or lipid-coupled SLPs. Vaccination with both types of virosomes significantly improved the control of tumor outgrowth, leading to elimination of the tumors in about half the animals for the best combinations of adjuvants and to their survival beyond 100 days.

Induction of cancer neoantigens facilitates development of clinically relevant models for the study of pancreatic cancer immunobiology

Neoantigen burden and CD8 T cell infiltrate are associated with clinical outcome in pancreatic ductal adenocarcinoma (PDAC). A shortcoming of many genetic models of PDAC is the lack of neoantigen burden and limited T cell infiltrate. The goal of the present study was to develop clinically relevant models of PDAC by inducing cancer neoantigens in KP2, a cell line derived from the KPC model of PDAC. KP2 was treated with oxaliplatin and olaparib (OXPARPi), and a resistant cell line was subsequently cloned to generate multiple genetically distinct cell lines (KP2-OXPARPi clones). Clones A and E are sensitive to immune checkpoint inhibition (ICI), exhibit relatively high T cell infiltration, and have significant upregulation of genes involved in antigen presentation, T cell differentiation, and chemokine signaling pathways. Clone B is resistant to ICI and is similar to the parental KP2 cell line in terms of relatively low T cell infiltration and no upregulation of genes involved in the pathways noted above. Tumor/normal exome sequencing and in silico neoantigen prediction confirms successful generation of cancer neoantigens in the KP2-OXPARPi clones and the relative lack of cancer neoantigens in the parental KP2 cell line. Neoantigen vaccine experiments demonstrate that a subset of candidate neoantigens are immunogenic and neoantigen synthetic long peptide vaccines can restrain Clone E tumor growth. Compared to existing models, the KP2-OXPARPi clones better capture the diverse immunobiology of human PDAC and may serve as models for future investigations in cancer immunotherapies and strategies targeting cancer neoantigens in PDAC.

Abstract CT036: Safety and immunogenicity of a first-in-human mutant KRAS long peptide vaccine combined with ipilimumab/nivolumab in resected pancreatic cancer: Preliminary analysis from a phase I study

Abstract Background: Novel strategies are needed to decrease the high recurrence rates of pancreatic ductal adenocarcinoma (PDAC) after curative-intent surgery. Mutant KRAS (mKRAS) is an oncogenic driver found in approximately 90% of PDAC that has emerged as a target for neoantigen-specific vaccination. Methods: This is a single-arm, open-label, first-in-human phase I study of a pooled synthetic long peptide (SLP) vaccine targeting six mKRAS subtypes (G12D, G12R, G12V, G12A, G12C, G13D) combined with ipilimumab/nivolumab (ipi/nivo) in patients with resected PDAC (NCT04117087). Key inclusion criteria: presence of a vaccine-targeted KRAS mutation, disease-free status after completing adjuvant chemotherapy within 6 months of enrollment. Priming phase: mKRAS vaccine given on days 1, 8, 15, and 22 along with ipi 1 mg/kg every 6 weeks for 2 doses and nivo 3 mg/kg every 3 weeks for 4 doses. Boost phase: mKRAS vaccine given on weeks 13, 21, 29, 37, and 45 along with nivo 480 mg every 4 weeks for 10 doses. Co-primary endpoints: safety, mKRAS-specific T cell response. Secondary endpoints: disease-free survival (DFS), overall survival (OS). Results: At the time of data cutoff (December 1, 2022), 11 patients were treated with a median follow-up time of 10.7 months. 8/11 patients achieved a mKRAS-specific T cell response, defined as >5-fold change in IFN-gamma-producing mKRAS-specific T cells within 17 weeks post-vaccination, as assessed by serial ELISpot. The median fold change in IFN-gamma-producing mKRAS-specific T cells within 17 weeks post-vaccination was 10.2 (range: 1.5-686.3). The majority of all adverse events were grade 1 (79.5%) or grade 2 (15.2%) in severity per NCI CTCAE v5.0. Four grade 3 immune-related adverse events (pneumonitis, adrenal insufficiency, arthralgias, myalgias) and discontinuation of checkpoint blockade occurred in 2/11 patients. The median DFS for the entire cohort was 6.4 months and not reached for OS. Patients who mounted a mKRAS-specific T cell response demonstrated a significant improvement in median DFS compared to immune non-responders (not reached vs 2.8 months, p = 0.045). Conclusions: The combination of a pooled SLP mKRAS vaccine and dual checkpoint blockade is tolerable and immunogenic in patients with resected PDAC. Induction of an mKRAS-specific T cell response is associated with improved DFS in this cohort. Ongoing correlative studies will apply multi-omic approaches to identify novel biomarkers of immune response and resistance. Citation Format: Saurav D. Haldar, Amanda Huff, Thatcher R. Heumann, Maureen Berg, Anna Ferguson, Su Jin Lim, Hao Wang, Amy M. Thomas, Julie M. Nauroth, Marina Baretti, Katherine M. Bever, Mark Yarchoan, Daniel A. Laheru, Elizabeth M. Jaffee, Nilofer S. Azad, Neeha Zaidi. Safety and immunogenicity of a first-in-human mutant KRAS long peptide vaccine combined with ipilimumab/nivolumab in resected pancreatic cancer: Preliminary analysis from a phase I study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT036.

The emerging role of vaccines in cancer therapies

Globally, there is a severe public health issue with cancer. Comprehensive funding has been provided for the creation of medicinal vaccines against cancer. The efficiency of vaccines in preventing bacterial and viral illnesses has been demonstrated. Over the past 200 years, they have averted many fatal diseases and saved countless lives. Vaccines protect against diseases brought on by viruses and bacteria by exposing recipients to attenuated or inactivated pathogens. Thereby, the individual's immune system can identify the antigen and behave. DNA vaccines, mRNA vaccines, and synthetic peptide vaccines are just a few of the innovative vaccinations created in recent years using modern biotechnology. Immune adjuvants or drug delivery systems are utilized to enhance immunogenicity through extensive immune system research, tests on animal models, and clinical trials of vaccines. This review paper will discuss therapeutic cancer vaccine mechanisms and cancer vaccine delivery methods.

A Synthetic SARS-CoV-2-Derived T-Cell and B-Cell Peptide Cocktail Elicits Full Protection against Lethal Omicron BA.1 Infection in H11-K18-hACE2 Mice.

Emerging variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been developing the capacity for immune evasion and resistance to existing vaccines and drugs. To address this, development of vaccines against coronavirus disease 2019 (COVID-19) has focused on universality, strong T cell immunity, and rapid production. Synthetic peptide vaccines, which are inexpensive and quick to produce, show low toxicity, and can be selected from the conserved SARS-CoV-2 proteome, are promising candidates. In this study, we evaluated the effectiveness of a synthetic peptide cocktail containing three murine CD4+ T-cell epitopes from the SARS-CoV-2 nonspike proteome and one B-cell epitope from the Omicron BA.1 receptor-binding domain (RBD), along with aluminum phosphate (Al) adjuvant and 5' cytosine-phosphate-guanine 3' oligodeoxynucleotide (CpG-ODN) adjuvant in mice. The peptide cocktail induced good Th1-biased T-cell responses and effective neutralizing-antibody titers against the Omicron BA.1 variant. Additionally, H11-K18-hACE2 transgenic mice were fully protected against lethal challenge with the BA.1 strain, with a 100% survival rate and reduced pulmonary viral load and pathological lesions. Subcutaneous administration was found to be the superior route for synthetic peptide vaccine delivery. Our findings demonstrate the effectiveness of the peptide cocktail in mice, suggesting the feasibility of synthetic peptide vaccines for humans. IMPORTANCE Current vaccines based on production of neutralizing antibodies fail to prevent the infection and transmission of SARS-CoV-2 Omicron and its subvariants. Understanding the critical factors and avoiding the disadvantages of vaccine strategies are essential for developing a safe and effective COVID-19 vaccine, which would include a more effective and durable cellular response, minimal effects of viral mutations, rapid production against emerging variants, and good safety. Peptide-based vaccines are an excellent alternative because they are inexpensive, quick to produce, and very safe. In addition, human leukocyte antigen T-cell epitopes could be targeted at robust T-cell immunity and selected in the conserved region of the SARS-CoV-2 variants. Our study showed that a synthetic SARS-CoV-2-derived peptide cocktail induced full protection against lethal infection with Omicron BA.1 in H11-K18-hACE2 mice for the first time. This could have implications for the development of effective COVID-19 peptide vaccines for humans.

Cancer-specific T helper shared and neo-epitopes uncovered by expression of the MHC class II master regulator CIITA.

We report an approach to identify tumor-specific CD4+ Tcell neo-epitopes of both mouse and human cancer cells by analysis of major histocompatibility complex (MHC) class II-eluted natural peptides. MHC class II-presented peptide sequences are identified by introducing the MHC class II transactivator (CIITA) in tumor cells that were originally MHC class II negative. CIITA expression facilitates cell-surface expression of MHC class II molecules and the appropriate peptide-loading machinery. Peptide elution of purified MHC class II molecules and subsequent mass spectrometry reveals oncoviral- and neo-epitopes as well as shared epitopes. Immunological relevance of these epitopes is shown by natural presentation by dendritic cells and immunogenicity. Synthetic peptide vaccination induced functional CD4+ Tcell responses, which helped tumor control invivo. Thus, this CIITA transfection approach aids to identify relevant T helper epitopes presented by any MHC class II allele that would be otherwise very difficult to predict and reveals important targets for cancer immunotherapy.

A third vaccination with a single T cell epitope confers protection in a murine model of SARS-CoV-2 infection

Understanding the mechanisms and impact of booster vaccinations are essential in the design and delivery of vaccination programs. Here we show that a three dose regimen of a synthetic peptide vaccine elicits an accruing CD8+ T cell response against one SARS-CoV-2 Spike epitope. We see protection against lethal SARS-CoV-2 infection in the K18-hACE2 transgenic mouse model in the absence of neutralizing antibodies, but two dose approaches are insufficient to confer protection. The third vaccine dose of the single T cell epitope peptide results in superior generation of effector-memory T cells and tissue-resident memory T cells, and these tertiary vaccine-specific CD8+ T cells are characterized by enhanced polyfunctional cytokine production. Moreover, fate mapping shows that a substantial fraction of the tertiary CD8+ effector-memory T cells develop from re-migrated tissue-resident memory T cells. Thus, repeated booster vaccinations quantitatively and qualitatively improve the CD8+ T cell response leading to protection against otherwise lethal SARS-CoV-2 infection.

Abstract 4160: Promoting immunogenicity of synthetic long peptide vaccines based on in vivo IgG complex formation: Preclinical evaluation and clinical entry of the TET platform

Abstract Vaccines based on synthetic long peptides, targeting immunogenic region(s) of tumor associated proteins, are becoming increasingly used in oncology. Synthetic long peptides require endogenous processing by antigen presenting cells to be presented to T cells, thus reducing the risk of antigen presentation by non-professional antigen presenting cells lacking co-stimulation receptors. The formulation and delivery strategies require further development as peptides degrade rapidly in vivo. Herein we make use of a novel targeting and adjuvant strategy to deliver peptides to antigen presenting cells. Tumor-derived peptides are coupled to a B cell epitope element (the MTTE sequence, a tetanus toxin-derived universal B cell epitope) which induce the formation of peptide-conjugate -complex formation in vivo. This strategy, further named the TET technology, makes use of pre-existing antibodies to improve the bioavailability, stability, and immunogenicity of tumor-derived peptide therapeutics. The TET technology is here used in TENDU, a first-in-class prostate cancer vaccine candidate. TENDU incorporates selected immunogenic prostate cancer epitopes derived from PAP and PSMA. The peptides are designed to include proteasome processing elements along with a unique TAP translocation element. To assess the design, a conjugate with a known DR4 epitope embedded in a longer peptide was evaluated for T cell priming in HLA-DR4 animals and displayed T cell expansion in response to a prime/boost vaccination. To ensure that prostate cancer patients respond with antibodies to the MTTE sequence after a tetanus toxoid (TTd) vaccination, both healthy controls and patients (age and gender matched) were vaccinated using a TTd-based vaccine regime. Anti-MTTE antibody titers were evaluated. Patients and HCs responded with increased IgG1 type antibodies against MTTE after TTd vaccination. Safety with regards to hypersensitivity in response to the vaccine platform was evaluated in rabbits and a human whole blood loop system without any identified adverse events. Based on preclinical data the no-observed-adverse-effect level (NOAEL) was set to 1440µg/dose. The vaccine is currently assessed in a First-in-Human clinical study (TENDU-101, 3+3 study design) in patients with relapse after a primary radical prostatectomy. No safety concerns were noted at the lowest dose level and the 400 µg dose cohort has been initiated with the first patient dosed with no reported adverse events. The study’s primary endpoints are safety and tolerability. Secondary endpoints involve cellular immune responses, systemic PSA and PAP levels along with dose level selection. In conclusion, TENDU, a first-in-class vaccine candidate is under clinical development evaluating safety and tolerability for the TET vaccine platform technology. Citation Format: Erika Fletcher, Iliana Kerzeli, Robert Cordfunke, Aikaterini Nasi, Gunilla Törnqvist, Robert Valentijn, Frida Lindqvist, Inken Dillmann, Martin Lord, Neanke Bouwman, Jacques Neefjes, Natasja Dolezal, Kees Franken, Stephanie McArdle, Murrium Ahmad, Silvia Johansson, Ferry Ossendorp, Michael Haggman, Wolfgang Lilleby, Gustav Ullenhag, Sam Ladjevardi, Justyna Jarblad, Jan Wouter Drijfhout, Sara Mangsbo. Promoting immunogenicity of synthetic long peptide vaccines based on in vivo IgG complex formation: Preclinical evaluation and clinical entry of the TET platform [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4160.

Immunity Evaluation of an Experimental Designed Nanoliposomal Vaccine Containing FMDV Immunodominant Peptides.

Foot-and-mouth disease (FMD) is a highly contagious viral disease affecting cloven-hoofed animals. The particular virus causing FMD disease is called FMD virus and is a member of the Aphthovirus genus in the Picornaviridae family. The FMD virus has an 8500 nt long single strain positive RNAgenome with one open reading frame (ORF) trapped in an icosahedral capsid protein. This virus genome doesn't have proofreading property which leads to high mutagenesis. It has seven serotypes, including O, A, ASIA, SAT1, SAT2, and C serotypes, as well as many subtypes. Iran is an endemic region for foot-and-mouth disease. Vaccination of susceptible animals with an inactivated whole-virus vaccine is the only way to control the epidemic in many developing countries. Today, conventionally attenuated and killed virus vaccines are being used worldwide. In Iran, animals have been vaccinated every 105 days with an inactivated FMD vaccine. Although commercially available FMD vaccines are effective, they provide short-term immunity requiring regular boosters. A new FMD vaccine is needed to improve immunization, safety, and long-term immune responses. A synthetic peptide vaccine is one of the safe and important vaccines. Peptide vaccine has low immunogenicity, requiring strong adjuvants. Nanoliposomes can be used as new adjuvants to improve immune response. In the current study, nanoliposomal carriers were selected using Dimyristoylphosphatidylcholine (DMPC), dimyristoyl phosphoglycerol (DMPG), and Cholesterol (Chol) as an adjuvant containing two immunodominant synthetic FMDV peptides. The liposomal formulations were characterized by various physicochemical properties. The size, zeta potential, and encapsulation efficiency were optimized, and the obtained nanoliposome was suitable as a vaccine. The efficacy of vaccines has been evaluated in guinea pigs as animal models. Indirect ELISA was used to detect FMDV-specific IgG. The obtained results indicated that although antibody titer was observed, the amount was lower compared to the groups that received inactivated virus-containing liposomes. In addition, the results showed that liposome was an appropriate adjuvant, compared to other adjuvants, such as Alum and Freund, and can act as a depot and induce an immune response.