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Personalized cancer vaccines are a promising approach for inducing T cell immunity to tumor neoantigens. Using a self-assembling nanoparticle vaccine that links neoantigen peptides to a Toll-like receptor 7/8 agonist (SNP-7/8a), we show how the route and dose alter the magnitude and quality of neoantigen-specific CD8+ T cells. Intravenous vaccination (SNP-IV) induced a higher proportion of TCF1+PD-1+CD8+ T cells as compared to subcutaneous immunization (SNP-SC). Single-cell RNA sequencing showed that SNP-IV induced stem-like genes (Tcf7, Slamf6, Xcl1) whereas SNP-SC enriched for effector genes (Gzmb, Klrg1, Cx3cr1). Stem-like cells generated by SNP-IV proliferated and differentiated into effector cells upon checkpoint blockade, leading to superior antitumor response as compared to SNP-SC in a therapeutic model. The duration of antigen presentation by dendritic cells controlled the magnitude and quality of CD8+ T cells. These data demonstrate how to optimize antitumor immunity by modulating vaccine parameters for specific generation of effector or stem-like CD8+ T cells. Seder and colleagues use a self-assembling nanoparticle vaccine and adjuvant to expand stem-like CD8+ T cells and trigger potent antitumor responses.

Therapeutic cancer vaccines are designed to increase tumor-specific T cell immunity. However, suppressive mechanisms within the tumor microenvironment (TME) may limit T cell function. Here, we assessed how the route of vaccination alters intratumoral myeloid cells. Using a self-assembling nanoparticle vaccine that links tumor antigen peptides to a Toll-like receptor 7/8 agonist (SNP-7/8a), we treated tumor-bearing mice subcutaneously (SNP-SC) or intravenously (SNP-IV). Both routes generated antigen-specific CD8

Malignant tumors of the central nervous system (CNS) continue to be a leading cause of cancer-related mortality in both children and adults. Traditional therapies for malignant brain tumors consist of surgical resection and adjuvant chemoradiation; such approaches are often associated with extreme morbidity. Accordingly, novel, targeted therapeutics for neoplasms of the CNS, such as immunotherapy with oncolytic engineered herpes simplex virus (HSV) therapy, are urgently warranted. Herein, we discuss treatment challenges related to HSV virotherapy delivery, entry, replication, and spread, and in so doing focus on host anti-viral immune responses and the immune microenvironment. Strategies to overcome such challenges including viral re-engineering, modulation of the immunoregulatory microenvironment and combinatorial therapies with virotherapy, such as checkpoint inhibitors, radiation, and vaccination, are also examined in detail.

Though outcomes for pediatric cancer patients have significantly improved over the past several decades, too many children still experience poor outcomes and survivors suffer lifelong, debilitating late effects after conventional chemotherapy, radiation, and surgical treatment. Consequently, there has been a renewed focus on developing novel targeted therapies to improve survival outcomes. Cancer vaccines are a promising type of immunotherapy that leverage the immune system to mediate targeted, tumor-specific killing through recognition of tumor antigens, thereby minimizing off-target toxicity. As such, cancer vaccines are orthogonal to conventional cancer treatments and can therefore be used alone or in combination with other therapeutic modalities to maximize efficacy. To date, cancer vaccination has remained largely understudied in the pediatric population. In this review, we discuss the different types of tumor antigens and vaccine technologies (dendritic cells, peptides, nucleic acids, and viral vectors) evaluated in clinical trials, with a focus on those used in children. We conclude with perspectives on how advances in combination therapies, tumor antigen (eg, neoantigen) selection, and vaccine platform optimization can be translated into clinical practice to improve outcomes for children with cancer.

Autoimmune diseases, transplantation, allergies and other inflammatory diseases impact a large number of individuals. These diseases are driven by dysfunctional immune responses (i.e., autoimmune disease, allergies), or normal immune responses that occur in unwanted contexts (i.e., transplant rejection, anti-drug antibodies). While tremendous progress has been made in creating treatment options for patients, most of these focus on disease management, rather than curative therapies. Additionally, the existing treatments lack specificity, a challenge that causes side effects or leaves patients susceptible to infection. Newer therapeutic classes, such as monoclonal antibodies, have helped improve selectivity, but generally do not distinguish between healthy and dysfunctional cells expressing the target of the antibody. Greater understanding of immune regulation and improved materials science engineering are now converging to yield promising approaches that aim to increase selectivity and effectiveness of therapies through induction of antigen-specific tolerance. Here we review the preclinical and clinical research to date using biomaterials to study and combat these conditions, as well as suggest areas for future research.

International audience; Personalized cancer vaccines targeting patient-specific neoantigens are a promising cancer treatment modality; however, neoantigen physicochemical variability can present challenges to manufacturing personalized cancer vaccines in an optimal format for inducing anticancer T cells. Here, we developed a vaccine platform (SNP-7/8a) based on charge-modified peptide-TLR-7/8a conjugates that are chemically programmed to self-assemble into nanoparticles of uniform size (~20 nm) irrespective of the peptide antigen composition. This approach provided precise loading of diverse peptide neoantigens linked to TLR-7/8a (adjuvant) in nanoparticles, which increased uptake by and activation of antigen-presenting cells that promote T-cell immunity. Vaccination of mice with SNP-7/8a using predicted neoantigens (n = 179) from three tumor models induced CD8 T cells against ~50% of neoantigens with high predicted MHC-I binding affinity and led to enhanced tumor clearance. SNP-7/8a delivering in silico-designed mock neoantigens also induced CD8 T cells in nonhuman primates. Altogether, SNP-7/8a is a generalizable approach for codelivering peptide antigens and adjuvants in nanoparticles for inducing anticancer T-cell immunity.

In 2015 and in 2016, there were an estimated 429,000–730,500 deaths caused by malaria.1–3 Plasmodium falciparum (Pf) is the cause of > 98% of malaria deaths and > 80% of malaria cases in sub-Saharan Africa. Our goal is to field a vaccine that will prevent infection with Pf and thereby prevent all manifestations of Pf malaria and parasite transmission from humans to mosquitoes.4 Plasmodium falciparum sporozoites (SPZ) are the only immunogens that have ever prevented Pf infection in > 90% of subjects.5–7 Sanaria® PfSPZ Vaccine (Sanaria Inc., Rockville, MD) is composed of radiation-attenuated, aseptic, purified, cryopreserved PfSPZ.8,9 When administered by rapid intravenous injection, PfSPZ Vaccine protected 100% (6/6) of malaria-naive subjects in the United States against mosquito bite–controlled human malaria infection (CHMI) with Pf parasites similar to those in the vaccine (homologous) 3 weeks after the last immunization,10 and 65% at 24 weeks.11 Protection was durable against homologous mosquito bite CHMI for at least 59 weeks12 and heterologous (parasites different than in vaccine) mosquito bite CHMI for at least 33 weeks.13 PfSPZ Vaccine also prevented naturally transmitted heterogeneous Pf in adults in Mali for at least 24 weeks (vaccine efficacy [VE] 52% by time to event and 29% by proportional analysis).14 We used the same dosage regimen as in the United States and Mali to evaluate the tolerability, safety, immunogenicity, and VE of PfSPZ Vaccine in young adult male Tanzanians. Previously, we had conducted the first modern CHMI in Africa and showed that injection of aseptic, purified, cryopreserved PfSPZ, Sanaria® PfSPZ Challenge, consistently infected Tanzanian volunteers and subsequently repeated in multiple other countries.15–21 In this study, we took advantage of this capability to assess VE of PfSPZ Vaccine by CHMI with PfSPZ Challenge (NF54). The same PfSPZ Vaccine dosage regimen was less immunogenic and protective in Tanzanians than in Americans,11 and VE against homologous CHMI in Tanzania was lower (or similar) to VE against intense field exposure to heterogeneous Pf parasites in Mali.14

A live-attenuated malaria vaccine, Plasmodium falciparum sporozoite vaccine (PfSPZ Vaccine), confers sterile protection against controlled human malaria infection (CHMI) with Plasmodium falciparum (Pf) parasites homologous to the vaccine strain up to 14 mo after final vaccination. No injectable malaria vaccine has demonstrated long-term protection against CHMI using Pf parasites heterologous to the vaccine strain. Here, we conducted an open-label trial with PfSPZ Vaccine at a dose of 9.0 × 105 PfSPZ administered i.v. three times at 8-wk intervals to 15 malaria-naive adults. After CHMI with homologous Pf parasites 19 wk after final immunization, nine (64%) of 14 (95% CI, 35-87%) vaccinated volunteers remained without parasitemia compared with none of six nonvaccinated controls (P = 0.012). Of the nine nonparasitemic subjects, six underwent repeat CHMI with heterologous Pf7G8 parasites 33 wk after final immunization. Five (83%) of six (95% CI, 36-99%) remained without parasitemia compared with none of six nonvaccinated controls. PfSPZ-specific T-cell and antibody responses were detected in all vaccine recipients. Cytokine production by T cells from vaccinated subjects after in vitro stimulation with homologous (NF54) or heterologous (7G8) PfSPZ were highly correlated. Interestingly, PfSPZ-specific T-cell responses in the blood peaked after the first immunization and were not enhanced by subsequent immunizations. Collectively, these data suggest durable protection against homologous and heterologous Pf parasites can be achieved with PfSPZ Vaccine. Ongoing studies will determine whether protective efficacy can be enhanced by additional alterations in the vaccine dose and number of immunizations.

Induction of memory CD8(+) T cells is important for controlling infections such as malaria and HIV/AIDS and for cancer immunotherapy. Accurate assessment of antigen-specific (Ag-specific) CD8(+) T cells is critical for vaccine optimization and for defining correlates of protection. However, conditions for determining Ag-specific CD8(+) T cell responses ex vivo using intracellular cytokine staining (ICS) may be variable, especially in humans with complex antigens. Here, we used an attenuated whole parasite malaria vaccine model in humans and various experimental infections in mice to show that the duration of antigenic stimulation and timing of brefeldin A (BFA) addition influence the magnitude of Ag-specific and bystander T cell responses. Indeed, after immunization with an attenuated whole sporozoite malaria vaccine in humans, significantly higher numbers of IFN-γ–producing memory CD8(+) T cells comprising Ag-specific and bystander responses were detected when the duration of Ag stimulation prior to addition of BFA was increased. Mechanistic analyses of virus-specific CD8(+) T cells in mice revealed that the increase in IFN-γ–producing CD8(+) T cells was due to bystander activation of Ag-experienced memory CD8(+) T cells, and correlated with the proportion of Ag-experienced CD8(+) T cells in the stimulated populations. Incubation with anti-cytokine antibodies (e.g., IL-12) improved accuracy in detecting bona fide memory CD8(+) T cell responses, suggesting this as the mechanism for the bystander activation. These data have important implications for accurate assessment of immune responses generated by vaccines intended to elicit protective memory CD8(+) T cells.

Small molecule Toll-like receptor-7 and -8 agonists (TLR-7/8a) can be used as vaccine adjuvants to induce CD8 T cell immunity but require formulations that prevent systemic toxicity and focus adjuvant activity in lymphoid tissues. Here, we covalently attached TLR-7/8a to polymers of varying composition, chain architecture and hydrodynamic behavior (∼300 nm submicrometer particles, ∼10 nm micelles and ∼4 nm flexible random coils) and evaluated how these parameters of polymer-TLR-7/8a conjugates impact adjuvant activity in vivo. Attachment of TLR-7/8a to any of the polymer compositions resulted in a nearly 10-fold reduction in systemic cytokines (toxicity). Moreover, both lymph node cytokine production and the magnitude of CD8 T cells induced against protein antigen increased with increasing polymer-TLR-7/8a hydrodynamic radius, with the submicrometer particle inducing the highest magnitude responses. Notably, CD8 T cell responses induced by polymer-TLR-7/8a were dependent on CCR2+ monocytes and IL-12, whereas responses by a small molecule TLR-7/8a that unexpectedly persisted in vaccine-site draining lymph nodes (T1/2 = 15 h) had less dependence on monocytes and IL-12 but required Type I IFNs. This study shows how modular properties of synthetic adjuvants can be chemically programmed to alter immunity in vivo through distinct immunological mechanisms.

A malaria vaccine that prevents infection will be an important new tool in continued efforts of malaria elimination, and such vaccines are under intense development for the major human malaria parasite Plasmodium falciparum (Pf). Antibodies elicited by vaccines can block the initial phases of parasite infection when sporozoites are deposited into the skin by mosquito bite and then target the liver for further development. However, there are currently no standardized in vivo preclinical models that can measure the inhibitory activity of antibody specificities against Pf sporozoite infection via mosquito bite. Here, we use human liver-chimeric mice as a challenge model to assess prevention of natural Pf sporozoite infection by antibodies. We demonstrate that these mice are consistently infected with Pf by mosquito bite and that this challenge can be combined with passive transfer of either monoclonal antibodies or polyclonal human IgG from immune serum to measure antibody-mediated blocking of parasite infection using bioluminescent imaging. This methodology is useful to down-select functional antibodies and to investigate mechanisms or immune correlates of protection in clinical trials, thereby informing rational vaccine optimization., Malaria: ‘Humanized’ mice offer a new preclinical research tool Mice containing human liver cells can model early-stage malaria infection and test antibody efficacy. A major obstacle in malaria vaccine development is the lack of relevant preclinical models to study how to prevent malaria infection. Stefan Kappe, of the United States’ Center for Infectious Disease Research and the University of Washington, led a collaboration of American and Dutch scientists to overcome this using mice in which the mouse liver cells have been largely replaced with human liver cells. The group demonstrated that their model mirrors infection with the malaria-causing parasite Plasmodium falciparum from mosquito bite through the week-long liver development, and harnessed this to discern the efficacy of different antibodies against the parasite. This research could hugely benefit our understanding of malaria infection and reduce the high failure rate of human vaccine clinical trials.

Mutation-derived tumor antigens (MTA)—alternatively known as “neoantigens”—are a class of tumor antigens generated by tumor cell-intrinsic somatic DNA alterations. MTA are thought to be the predominant target of spontaneous and treatment-induced anti-tumor immunity. Direct targeting of MTA with therapeutic vaccination or other approaches is thus an active area of clinical research. However, pre-clinical studies of MTA-specific immunity have been limited in part due to a lack of reproducible targets. Furthermore, properties distinguishing effective MTA-specific immune responses, from less effective responses targeting other types of non-mutated tumor antigens have not been identified. To address this deficit, we previously reported the development of a system wherein MTA-specific CD8+ T-cell-mediated immunity could be systematically characterized. Briefly, we performed exome (WES) and RNASeq on the B16F1 and B16F10 melanoma cell lines, as well as matched normal tissue. We identified somatic single-nucleotide substitutions, insertion and deletion (INDEL), as well as larger INDEL and gene translocation events. The sequence identity and expression of somatic variants was validated by RNASeq. Standard in silico protocols were used to predict MHC-I binding affinity, which we subsequently validated via cell-free fluorescent peptide:MHC-I stability assay. Using a nanoparticle-based vaccination protocol, we identified and characterized multiple MHC-I restricted MTA in the B16F10 model system. We report an initial characterization of the vaccine-induced MTA-specific CD8+ T-cell response and demonstrate activity of vaccine monotherapy following subcutaneous tumor challenge. We extend prior observations were expanded upon in the following manner: First, the sensitivity and specificity of MTA-specific CD8+ T-cells was determined by in vitro stimulation with target MTA peptide and matched wildtype-sequence peptide followed by intracellular flow cytometry. Vaccine-induced CD8+ T-cells exhibit selectivity to MTA peptide targets ranging perfect specificity to moderate selectivity. A cell-based MHC-I binding assay was used to measure the relative affinity of MTA and matched wildtype peptides. The selectivity of vaccine-induced CD8+ T-cells to MTA peptides was observed to depend both on peptide:MHC-I as well as TCR:pMHC interactions. With respect to sensitivity of CD8+ T-cells towards target antigen, CD8+ T-cells targeting MTA were found to be more sensitive than those targeting nonmutated tumor antigens. We assessed direct recognition of target antigen endogenously presented by autologous tumor cells and describe tumor cell-intrinsic, as antigen-specific features affecting lymphocyte recognition and effector function. Second, we longitudinally profiled the surface receptor phenotype, and transcription factor usage of MTA-specific CD8+ T-cells by single-cell mass cytometry (CyTOF). We describe the phenotype of peripheral, as well as tumor-infiltrating MTA-specific CD8+ T-cells. Using a genetically-encoded fluorescent reporter we identify MTA-specific CD8+ T-cells actively engaged with antigen in situ and describe the molecular and cellular characterization of these tumor-reactive MTA-specific CD8+ T-cells. In summary, we report the identification and detailed characterization of multiple previously-undescribed MHC-I restricted MTA relevant to the widely-utilized B16F10 model. We characterize the phenotype and function of MTA-specific CD8+ T-cells. Finally, we describe phenotypic and functional properties of MTA-specific CD8+ T-cells associated with therapeutic activity in vivo. Citation Format: John P. Finnigan, Andrew S. Ishizuka, Geoffrey M. Lynn, Alex Rubinsteyn, Robert A Seder, Nina Bhardwaj. Molecular and cellular properties of neoantigen-specific CD8+ T-cells on interaction with B16F10 melanoma in situ [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B108.

T cells recognizing tumor-specific neoantigens can mediate effective anti-tumor immunity and provide the rationale for personalized cancer vaccines (PCVs). Current approaches for PCVs include synthetic long peptides given with adjuvants or RNA vaccines. Such approaches induce de novo CD8 T cell responses in ~10% or less of predicted neoantigens. Here, we focused on how peptide based neoantigen vaccines could be altered to enhance the magnitude and breadth of CD8 T cells. A key finding was that particulate peptide antigens, unlike soluble peptide antigens, are more efficiently taken up by dendritic cells in draining lymphoid tissue for increasing CD8 T cell expansion. However, due to the broad range of neoantigen physicochemical properties, ensuring consistent particle vaccine formulations with neoantigen peptides is a major challenge. Therefore, we developed a new PCV platform based on charge-modified peptide-TLR-7/8 agonist conjugates that are chemically programmed for self-assembling into nanoparticles (“SNP-7/8a”) of a defined size (20–50 nm) irrespective of the underlying neoantigen peptide composition. Bioinformatics analysis of 72 million human genome-derived neoantigens shows that SNP-7/8a ensures consistent nanoparticle formation with neoantigens at extremes of charge and hydropathy. Vaccination of mice with SNP-7/8a using predicted neoantigens (n = 179) from three tumor models induced CD8 T cells in ~50% of those with high predicted MHC-I binding affinity (IEDB consensus score < 0.5). Moreover, therapeutic vaccination with SNP-7/8a enhanced tumor clearance in tumor models using neoantigens, self-antigens or viral antigens. Overall, the SNP-7/8a PCV is a universal approach for co-delivering peptide antigens and immune adjuvants in nanoparticles to enhance anticancer T cell immunity. Citation Format: Geoffrey M. Lynn, Faezzah Baharom, Yaling Zhu, Vincent Coble, Andrei Ramirez-Valdez, Hide Yamane, Kennedy Tobin, Brennan Decker, Andrew Ishizuka, Robert Seder. Peptide-TLR-7/8 agonist conjugate vaccines chemically programmed for nanoparticle self-assembly to enhance the magnitude and breadth of anticancer neoantigen CD8 T cell immunity [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr IA29.

Immunization with Plasmodium falciparum sporozoites under chemoprophylaxis can protect against controlled human malaria infection with the same strain for at least 10 weeks, and protection correlates with polyfunctional T-cell memory. The best candidates for a malaria vaccine so far have been radiation-attenuated Plasmodium falciparum sporozoites (PfSPZ) inoculated by mosquitos, intravenous injection of radiation-attenuated, cryopreserved PfSPZ, and infectious PfSPZ inoculated by mosquitos in people taking chloroquine or mefloquine. Here Stephen Hoffman, Peter Kremsner and colleagues report that inoculation of volunteers taking chloroquine with direct intravenous injection of aseptic, cryopreserved, non-irradiated PfSPZ can induce protection against infection with the same strain for at least ten weeks. The authors show that protection correlates with polyfunctional T-cell memory. A highly protective malaria vaccine would greatly facilitate the prevention and elimination of malaria and containment of drug-resistant parasites1. A high level (more than 90%) of protection against malaria in humans has previously been achieved only by immunization with radiation-attenuated Plasmodium falciparum (Pf) sporozoites (PfSPZ) inoculated by mosquitoes2,3,4; by intravenous injection of aseptic, purified, radiation-attenuated, cryopreserved PfSPZ (‘PfSPZ Vaccine’)5,6; or by infectious PfSPZ inoculated by mosquitoes to volunteers taking chloroquine7,8,9,10 or mefloquine11 (chemoprophylaxis with sporozoites). We assessed immunization by direct venous inoculation of aseptic, purified, cryopreserved, non-irradiated PfSPZ (‘PfSPZ Challenge’12,13) to malaria-naive, healthy adult volunteers taking chloroquine for antimalarial chemoprophylaxis (vaccine approach denoted as PfSPZ-CVac)14. Three doses of 5.12 × 104 PfSPZ of PfSPZ Challenge12,13 at 28-day intervals were well tolerated and safe, and prevented infection in 9 out of 9 (100%) volunteers who underwent controlled human malaria infection ten weeks after the last dose (group III). Protective efficacy was dependent on dose and regimen. Immunization with 3.2 × 103 (group I) or 1.28 × 104 (group II) PfSPZ protected 3 out of 9 (33%) or 6 out of 9 (67%) volunteers, respectively. Three doses of 5.12 × 104 PfSPZ at five-day intervals protected 5 out of 8 (63%) volunteers. The frequency of Pf-specific polyfunctional CD4 memory T cells was associated with protection. On a 7,455 peptide Pf proteome array, immune sera from at least 5 out of 9 group III vaccinees recognized each of 22 proteins. PfSPZ-CVac is a highly efficacious vaccine candidate; when we are able to optimize the immunization regimen (dose, interval between doses, and drug partner), this vaccine could be used for combination mass drug administration and a mass vaccination program approach to eliminate malaria from geographically defined areas.

An attenuated Plasmodium falciparum (Pf) sporozoite (SPZ) vaccine, PfSPZ Vaccine, is highly protective against controlled human malaria infection (CHMI) 3 weeks after immunization, but the durability of protection is unknown. We assessed how vaccine dosage, regimen, and route of administration affected durable protection in malaria-naive adults. After four intravenous immunizations with 2.7 × 10(5) PfSPZ, 6/11 (55%) vaccinated subjects remained without parasitemia following CHMI 21 weeks after immunization. Five non-parasitemic subjects from this dosage group underwent repeat CHMI at 59 weeks, and none developed parasitemia. Although Pf-specific serum antibody levels correlated with protection up to 21-25 weeks after immunization, antibody levels waned substantially by 59 weeks. Pf-specific T cell responses also declined in blood by 59 weeks. To determine whether T cell responses in blood reflected responses in liver, we vaccinated nonhuman primates with PfSPZ Vaccine. Pf-specific interferon-γ-producing CD8 T cells were present at ∼100-fold higher frequencies in liver than in blood. Our findings suggest that PfSPZ Vaccine conferred durable protection to malaria through long-lived tissue-resident T cells and that administration of higher doses may further enhance protection.

Malaria vaccine development has been hampered by the limited availability of antigens identified through conventional discovery approaches, and improvements are needed to enhance the efficacy of the leading vaccine candidate RTS,S that targets the circumsporozoite protein (CSP) of the infective sporozoite. Here we report a transcriptome-based approach to identify novel pre-erythrocytic vaccine antigens that could potentially be used in combination with CSP. We hypothesized that stage-specific upregulated genes would enrich for protective vaccine targets, and used tiling microarray to identify P. falciparum genes transcribed at higher levels during liver stage versus sporozoite or blood stages of development. We prepared DNA vaccines for 21 genes using the predicted orthologues in P. yoelii and P. berghei and tested their efficacy using different delivery methods against pre-erythrocytic malaria in rodent models. In our primary screen using P. yoelii in BALB/c mice, we found that 16 antigens significantly reduced liver stage parasite burden. In our confirmatory screen using P. berghei in C57Bl/6 mice, we confirmed 6 antigens that were protective in both models. Two antigens, when combined with CSP, provided significantly greater protection than CSP alone in both models. Based on the observations reported here, transcriptional patterns of Plasmodium genes can be useful in identifying novel pre-erythrocytic antigens that induce protective immunity alone or in combination with CSP.

Induction of T cell immunity against neoantigens of cancers is a promising personalized vaccine approach against tumors. We developed a novel vaccine platform to enhance the breadth and magnitude of neoantigen-specific CD8 T cell responses by coupling neoantigen peptides to a polymer containing a Toll-Like Receptor-7/8 agonist that self-assembles into nanoparticles (termed SPP-7/8a). As the SPP-7/8 vaccine platform can be formulated to immunize against multiple neoantigen peptides, a critical issue is how the delivery influences the magnitude and breadth of CD8 T cell responses. Thus, C57BL/6 mice were injected subcutaneously against a single neoantigen at either a single site, or divided across four sites. CD8 T cell responses were ~3% in the mice immunized at multiple sites compared to ~1% at a single injection site. To assess breadth, mice were immunized with four antigens, with either a single antigen at each of four injection sites or a combination of all four antigens across four injection sites. In mice that received all four antigens in each site, CD8 T cell responses against two of the antigens were undetectable. By contrast, in animals that received 1 antigen per site, responses were detected against all four antigens, and the total magnitude was higher than animals receiving 4 antigens per site. Collectively, these data suggest that despite increasing the CD8 T cell response of a single antigen via multi-site injection, vaccination even with as few as 4 antigens can interfere with the induction of neoantigen-specific CD8 T cells. Current work is focused on altering the delivery of the SPP-7/8a immunization approach to optimize both magnitude and breadth of CD8 T cell immunity that will be critical for tumor treatment and protection.

Targeting tumor specific neoantigens through personalized therapeutic vaccination is a promising approach to induce T cell immunity against a variety of tumors. Current vaccine formulations induce CD8 T cell responses against a limited subset of pre-selected neoantigens. We developed a novel vaccine platform to enhance the breadth and magnitude of CD8 T cell responses by chemically coupling synthetic neoantigen peptides to a synthetic polymer containing a toll-like receptor-7/8 agonist that self-assembles into nanoparticles (termed SPP-7/8a). To test the efficiency of the SPP-7/8a platform for inducing antigenic breadth, 173 transcribed non-synonymous single nucleotide variants were identified in a mouse melanoma tumor line (SB-3123). Mice were vaccinated twice with a random set of 96 SB-3123 neoantigens with SPP-7/8a. The binding affinity was predicted for each neoantigen using the Immune Epitope Database and Analysis Resource (IEDB.org) Consensus algorithm, which ranged from the 0.15 to 3.05 percentile. Overall, CD8 T cell responses were detectable at frequencies ranging from 0.1% to 16% of total CD8 T cells against 10 of the 96 neoantigens (~10%). However, by stratifying the 96 neoantigens according to high affinity binders (Consensus < 0.5), 7/14 (50%) induced CD8 T cell responses. These data show that the SPP-7/8a platform efficiently induces CD8 T cell using peptides that have high binding affinity. Ongoing studies will determine whether the increased breadth of CD8 responses following SPP-7/8a vaccination confers protection against established tumors.