Abstract Although chimeric antigen receptor (CAR)-T cell therapy has transformed the treatment landscape of B-cell malignancies, many patients with relapsed/refractory diffuse large B-cell lymphoma (r/r DLBCL) experience disease relapse driven by poor CAR-T cell persistence and functional impairment within the immunosuppressive tumor microenvironment. Interleukin-2 (IL-2) has potential to enhance T-cell activity, but its clinical application is hindered by undesirable effects, particularly the stimulation of regulatory T cells (Tregs) and toxicities. To selectively enhance effector T-cell activation while limiting Treg expansion and toxicities, our team engineered a novel IL-2 variant (called IL2-mutein, or IL2m) incorporating four point mutations that disrupt its binding to the IL-2 receptor alpha chain (CD25), which is predominantly expressed on Tregs. The safety and efficacy of this IL2m is being investigated as a monotherapy for patients with solid tumor malignancies (clinical trial #RPCEC00000234). We evaluated whether IL2m can improve CAR-T cell efficacy by enhancing CAR-T cell persistence and decreasing dysfunction. We investigated the effects of IL2m on the function of CD19 CAR-T cells in an in vitro model of DLBCL using Eµ-ALL tumor cells. We showed that IL2m promoted antigen-driven expansion of CD19 CAR-T cells, enhancing CD8+CAR-T proliferation (80.3 vs 35.6 % CD8+ cells of lymphocytes) and increasing granzyme B (99.6 vs 47.8 % GzmB+of CD8+ lymphocytes) and TNFα secretion (31.2 vs 24.9 pg/mL, p < 0.0001) upon co-culture with tumor cells, as assessed by real-time imaging and flow cytometry. Moreover, IL2m-treated CAR-T cells exhibited reduced PD-1 expression (3.7 vs 20.2 % PD-1+cells of CD8+ lymphocytes), suggesting improved functional fitness. To evaluate the translational relevance of this compound, we evaluated IL2m in a syngeneic r/r DLBCL mouse model in which CD19 CAR-T cells alone show limited efficacy with a median overall survival of only 24 days post-CAR infusion (n = 16-18 mice per group). IL2m treatment significantly improved overall median survival in mice to 46 days and reduced tumor burden (total flux of 1.02e+09 vs 7.44e+09 p/s 17 days post-CAR infusion, p < 0.0001) compared to those injected with CAR-T cells alone, as measured by bioluminescent imaging. Notably, a substantial proportion of mice responded to the treatment (8/18 mice), with enhanced efficacy observed using a twice-daily low-dose regimen. Indeed, because of its short half-life, administering IL2m in two daily doses of 600 IU resulted in better responses than a single daily dose of 1200 IU. Mechanistically, IL2m enhanced the proliferation and activation of endogenous CD8+T cells (10.6 vs 5.3 % CD8+CD44+Ki67+ cells of lymphocytes, p = 0.0004), increased the frequency of circulating CAR-T cells (0.3 vs 0.1 cells per µL of blood, p = 0.0223), and boosted granzyme B+CD8+populations (2.9 vs 0.5 cells per µL of blood, p = 0.0099), without promoting immunosuppressive Treg expansion – resulting in improved tumor cell killing (12.5 vs 614.0 Eµ cells per µL of blood, p = 0.0191), as evaluated by flow cytometry analyses on the peripheral blood of the animals. Altogether, our findings support IL2m as a promising immunomodulatory adjunct to improve the efficacy and durability of CAR-T cell therapy, leading to the development of a phase I trial combining IL2m with CAR-T cell therapy in r/r DLBCL.

Macrophages represent the most abundant immune component of the tumor microenvironment and often exhibit protumorigenic (M2-like) phenotypes that contribute to disease progression. Despite their generally accepted protumorigenic role, macrophages can also display tumoricidal (or M1-like) behavior, revealing that macrophages can be functionally reprogrammed, depending on the cues received within the tumor microenvironment. Moreover, such plasticity may be achieved by pharmacologic or biologic interventions. To that end, we previously demonstrated that a novel immunomodulator termed the “very small size particle” (VSSP) facilitates maturation of dendritic cells and differentiation of myeloid-derived suppressor cells to APCs with reduced suppressive activity in cancer models. VSSP was further shown to act in the bone marrow to drive the differentiation of progenitors toward monocytes, macrophages, and dendritic cells during emergency myelopoiesis. However, the underlying mechanisms for VSSP-driven alterations in myeloid differentiation and function remained unclear. In this study, in mouse models, we focused on macrophages and tested the hypothesis that VSSP drives macrophages toward M1-like functional states via IRF8- and PU.1-dependent mechanisms. We further hypothesized that such VSSP-mediated actions would be accompanied by enhanced antitumor responses. Overall, we showed that (1) VSSP drives naive or M2-derived macrophages to M1-like states, (2) the M1-like state induced by VSSP occurs via IRF8- and PU.1-dependent mechanisms, and (3) single-agent VSSP induces an antitumor response that is accompanied by alterations in the intratumoral myeloid compartment. These results provide a deeper mechanistic underpinning of VSSP and strengthen its use to drive M1-like responses in host defense, including cancer.

9135 Background: CIMAvax-EGF (C-E) is a recombinant anti-human epidermal growth factor (EGF) depleting immunotherapy which has previously shown increased survival as maintenance after platinum-based chemotherapy in patients (pts) with advanced NSCLC. The primary objective of this single-arm phase II trial was to evaluate the 12-month overall survival (OS) in pts receiving C-E in combination with Nivolumab(N) as 2L therapy for advanced NSCLC. Methods: Pts with previously treated, immunotherapy-naive advanced NSCLC received 2.4 mg C-E IM every 2 weeks(w) for 4 doses (loading phase) in combination with N 240mg IV every 2 w, then continued monthly maintenance C-E combined with N 240mg IV every 2 w. Enrollment to this arm was terminated before estimated sample size was met due to poor accrual as immunotherapy became incorporated into 1 st line therapy. We present OS and progression-free survival (PFS) data [determined using a Kaplan-Meier test with 90% confidence intervals (CI)] of pts who were able to complete the loading phase per protocol (PP). Results: 21 out of 23 enrolled pts were included in the PP analysis. Among the 21 pts, 17 (81.0%) had non-squamous(nsq) histology, 12 (57.1%) were KRAS wildtype (9.5% unknown status), 13 (61.9%) had PD-L1 tumor proportion score 0%. 43% pts (n=3) with known KRAS mutation (n=7) had co-mutated STK11. Disease control rate was 47.6% (n=10) defined as pts who had stable disease or partial response as best response per RECIST v1.1. The 21 PP pts had a 29% 3-year(yr) OS rate (90% CI 14, 45; intention-to-treat [ITT] population in 23 pts with 26% 3-yr OS rate, 90% CI 13, 42). Median(m) OS for PP pts was 11.9 months, 90% CI 8.0 – 23.9 months (ITT mOS 10.4 months, 90% CI 6.8-13.6). Pts with squamous histology had a better 3-yr OS rate compared to those with nsq histology [50% (90% CI 10, 81) vs 24% (90% CI 9, 41), respectively]. Pts with PD-L1 expression ≥1% had higher 3-yr OS [38% (90% CI 12, 63)] and 3-year PFS [38% (90% CI 12, 63)] compared to pts with no PD-L1 expression (3-yr OS 23% [90% CI 8, 44] and 3-yr PFS 8% [90% CI 1, 25]). mOS, 1-yr and 3-yr OS for EGFR/ALK/KRAS wildtype pts was higher [31.7 months (90% CI 5.9, NR), 67% (90% CI 4, 84), 50% (90% CI 24,71), respectively) compared to KRAS mutated NSCLC [10.1 months (90% CI 6.5, 12.1), 29% (90% CI 6, 56), 0% (90% CI 1, 41), respectively]. Conclusions: NSCLC pts who were able to complete the PP combination of C-E plus N at the minimum had numerically better OS compared to historical study cohorts with N as 2L monotherapy. Among pts who completed PP treatment, pts with KRAS wildtype NSCLC had the longest mOS observed. C-E is currently being investigated in combination with pembrolizumab as maintenance therapy after completing 1L chemoimmunotherapy for NSCLC with PD-L1 < 50% and as 1L therapy in combination with pembrolizumab for EGFR/ALK wildtype NSCLC and PD-L1 ≥ 50%. Clinical trial information: NCT02955290 .

Androgen deprivation therapy (ADT) is a standard therapy for prostate cancer (PCa). Though disseminated disease is initially sensitive to ADT, an important fraction of the patients progresses to castration-resistant prostate cancer (CRPC). For this reason, the identification of novel effective therapies for treating CRPC is needed. Immunotherapeutic strategies focused on macrophages as antitumor effectors, directly enhancing their tumoricidal potential at the tumor microenvironment or their adoptive transfer after ex vivo activation, have arisen as promising therapies in several cancer types. Despite several approaches centered on the activation of tumor-associated macrophages (TAMs) in PCa are under investigation, to date there is no evidence of clinical benefit in patients. In addition, the evidence of the effectiveness of macrophage adoptive transfer on PCa is poor. Here we find that VSSP, an immunomodulator of the myeloid system, decreases TAMs and inhibits prostatic tumor growth when administered to castrated Pten-deficient prostate tumor-bearing mice. In mice bearing castration-resistant Ptenpc−/−; Trp53pc−/− tumors, VSSP administration showed no effect. Nevertheless, adoptive transfer of macrophages activated ex vivo with VSSP inhibited Ptenpc−/−; Trp53pc−/− tumor growth through reduction of angiogenesis and tumor cell proliferation and induction of senescence. Taken together, our results highlight the rationale of exploiting macrophage functional programming as a promising strategy for CRPC therapy, with particular emphasis on ex vivo-activated proinflammatory macrophage adoptive transfer.

Purpose The F3II cell line is a highly invasive variant of mammary carcinoma. Although it is frequently used as a model to evaluate the efficacy of immunotherapy, its impact on the immune system remains poorly understood. The main objectives of this study were to evaluate the effects of F3II tumors on the development of chronic inflammation and to characterize tumor-associated immunosuppression. Methods Following the experimental implantation of F3II tumors in BALB/c mice, alterations in the liver and spleen anatomy and the numbers of circulating leukocytes, myeloid-derived suppressor cells (MDSCs), and regulatory T cells were measured using hematological techniques, histopathological analysis, and flow cytometry. The capacity of the F3II tumor-bearing mice to reject MB16F10 allogeneic tumor transplantation was also evaluated. In addition, the restoration of immune parameters in tumor-bearing mice was evaluated after standard breast cancer chemotherapy and surgical tumor excision. Results F3II tumor implantation increased the levels of chronic inflammatory markers, such as the neutrophil-to-lymphocyte and platelet-to-lymphocyte ratios, and caused myeloid alterations, including extramedullary granulopoiesis and megakaryopoiesis, along with the recruitment of MDSCs to the spleen. Chemotherapy or surgical F3II tumor removal completely rescued the tumor-associated extramedullary granulopoiesis and megakaryopoiesis. Notably, the presence of F3II tumors reduced the capacity of BALB/c mice to reject MB16F10 allogeneic tumor transplantation. Conclusion These results support the occurrence of F3II tumor-mediated immune cell dysfunction, which mimics the immune alterations characterized by chronic systemic inflammation and immunosuppression observed in breast cancer in clinical settings. Thus, the F3II tumor model is relevant for evaluating novel breast cancer immunotherapies and combinations in preclinical studies. This model could also be useful for identifying appropriate therapeutic targets and developing proof-of-concept experiments in the future.

The ovarian tumor microenvironment (TME) is characterized by the accumulation of immunosuppressive tumor-associated macrophages (TAMs) and granulocytic cells. Very small size particles (VSSP), comprised of the ganglioside NAcGM3 and Neisseria meningitidis derived outer membrane vesicles, is being developed as a nanoparticulated modulator of innate immunity. Prior studies have shown that VSSP enhanced antigen-specific cytotoxic T cell responses and reduced the suppressive phenotype of splenic granulocytic cells in tumor-bearing mice. Here, we hypothesized that intraperitoneal VSSP would modify myeloid cell accumulation and phenotypes in the ovarian TME and abrogate suppressor function of TAMs and tumor-associated granulocytic cells. In the ID8 syngeneic model of epithelial ovarian cancer, VSSP reduced peritoneal TAMs and induced M1-like polarization in TAMs. In addition, VSSP stimulated peritoneal inflammation characterized by increased granulocytes and monocytes, including inflammatory monocytic cells. VSSP treatment resulted in peritoneal TAMs and granulocytic cells being less suppressive of ex vivo stimulated CD8(+) T cell responses. VSSP alone and combined with anti-PD-1 modestly but significantly prolonged survival in tumor-bearing mice. In addition, ex vivo treatment with VSSP induced M1-like polarization in TAMs from patients with metastatic ovarian cancer and variably abrogated their suppressor phenotype. VSSP treatment also partially abrogated the induction of suppressor function in healthy donor neutrophils exposed to ascites supernatants from patients with ovarian cancer. Together, these results point to VSSP reprogramming myeloid responses resulting in abrogation of suppressive pathways and raise the potential for administration of VSSP into the TME to enhance anti-tumor immunity.

BackgroundCIMAvax-EGF is an epidermal growth factor (EGF)-depleting immunotherapy which has shown survival benefit as a switch maintenance treatment after platinum-based chemotherapy in advanced non-small cell lung cancer (NSCLC). The primary objective of this trial is to establish the safety and recommended phase II dose (RP2D) of CIMAvax-EGF in combination with nivolumab as second-line therapy for NSCLC.MethodsPatients with immune checkpoint inhibitor-naive metastatic NSCLC were enrolled using a “3+3” dose-escalation design. Toxicities were graded according to CTCAE V4.03. Thirteen patients (one unevaluable), the majority with PD-L1 0%, were enrolled into two dose levels of CIMAvax-EGF.FindingsThe combination was determined to be safe and tolerable. The recommended phase 2 dose of CIMAvax-EGF was 2.4 mg. Humoral response to CIMAvax-EGF was achieved earlier and in a greater number of patients with the combination compared to historical control. Four out of 12 evaluable patients had an objective response.

Background Immune suppression is common in neoplasia and a major driver is tumor-induced myeloid dysfunction. Yet, overcoming such myeloid cell defects remains an untapped strategy to reverse suppression and improve host defense. Exposure of bone marrow progenitors to heightened levels of myeloid growth factors in cancer or following certain systemic treatments promote abnormal myelopoiesis characterized by the production of myeloid-derived suppressor cells (MDSCs) and a deficiency in antigen-presenting cell function. We previously showed that a novel immune modulator, termed ‘very small size particle’ (VSSP), attenuates MDSC function in tumor-bearing mice, which was accompanied by an increase in dendritic cells (DCs) suggesting that VSSP exhibits myeloid differentiating properties. Therefore, here, we addressed two unresolved aspects of the mechanism of action of this unique immunomodulatory agent: (1) does VSSP alter myelopoiesis in the bone marrow to redirect MDSC differentiation toward a monocyte/macrophage or DC fate? and (2) does VSSP mitigate the frequency and suppressive function of human tumor-induced MDSCs? Methods To address the first question, we first used a murine model of granulocyte-colony stimulating factor-driven emergency myelopoiesis following chemotherapy-induced myeloablation, which skews myeloid output toward MDSCs, especially the polymorphonuclear (PMN)-MDSC subset. Following VSSP treatment, progenitors and their myeloid progeny were analyzed by immunophenotyping and MDSC function was evaluated by suppression assays. To strengthen rigor, we validated our findings in tumor-bearing mouse models. To address the second question, we conducted a clinical trial in patients with metastatic renal cell carcinoma, wherein 15 patients were treated with VSSP. Endpoints in this study included safety and impact on PMN-MDSC frequency and function. Results We demonstrated that VSSP diminished PMN-MDSCs by shunting granulocyte-monocyte progenitor differentiation toward monocytes/macrophages and DCs with heightened expression of the myeloid-dependent transcription factors interferon regulatory factor-8 and PU.1. This skewing was at the expense of expansion of granulocytic progenitors and rendered the remaining MDSCs less suppressive. Importantly, these effects were also demonstrated in a clinical setting wherein VSSP monotherapy significantly reduced circulating PMN-MDSCs, and their suppressive function. Conclusions Altogether, these data revealed VSSP as a novel regulator of myeloid biology that mitigates MDSCs in cancer patients and reinstates a more normal myeloid phenotype that potentially favors immune activation over immune suppression.

Introduction: Vaccine strategies to enhance CTLs response are still a challenge since it is necessary to favor the exogenous antigens (Ag) cross-presentation by antigen presenting cells (APCs). For this purpose, liposomes encapsulating bacteria pore-forming proteins (PFPs) have been used. Objective. To explore the ability of liposomes co-encapsulating the Ag ovalbumin (OVA) and sticholysin II (StII), a PFP produced by Stichodactyla helianthus, to induce a CTL response, functional in a tumor model. Methods: Liposomes co-encapsulating OVA and StII were prepared by dehydration-rehydration (Lp/OVA/StII). The response of CTLs was evaluated, as well as the antitumor activity in a preventive setting. The ability of StII to stimulate maturation of dendritic cells (DCs) in vitro was also explored. Results: Lp/OVA/StII enhanced the OVA-specific CTL response and antitumor activity in mice challenged with the E.G7-OVA tumor. StII induced the maturation of DCs in vitro, which was dependent on the Toll-like receptor 4 (TLR4), with a contribution to the response of CTLs induced by the liposomal formulation in vivo. Lp/OVA/StII favored in vitro the cross-presentation of OVA and the activation of CD8+ T cells by macrophages, but not by DCs. These results are the first evidence that StII encapsulated into liposomes functions as a vaccine platform to induce a robust CTL response, with a contribution that goes beyond its ability to form pores in membranes.

Introducción: Las estrategias vacunales para potenciar respuestas de linfocitos T CD8+ citotóxicos (CTL) constituyen un reto debido a la necesidad de favorecer la presentación cruzada de antígenos (Ag) exógenos por las células presentadoras de antígenos (APC). Con este propósito se han empleado liposomas que encapsulan proteínas formadoras de poros (PFP) de origen bacteriano. Objetivo: explorar la habilidad de liposomas que co-encapsulan el Ag ovoalbúmina (OVA) y sticholysina II (StII), una PFP producida por Stichodactyla helianthus, de inducir una respuesta de CTL, funcional en un modelo tumoral. Métodos: Liposomas que co-encapsulaban OVA y StII se prepararon mediante deshidratación-rehidratación (Lp/OVA/StII). Se evaluó la respuesta de CTL, así como la actividad antitumoral en un escenario preventivo. La capacidad de StII de estimular la maduración de las células dendríticas (DC) in vitro fue también explorada. Resultados: Lp/OVA/StII potenció la respuesta de CTL específica a OVA y una actividad antitumoral en ratones retados con el tumor E.G7-OVA. StII indujo la maduración de las DC in vitro, lo que resultó dependiente del receptor tipo Toll 4 (TLR4), con una contribución en la respuesta de CTL inducida por la formulación liposomal in vivo. Lp/OVA/StII favoreció in vitro la presentación cruzada de OVA y la activación de células T CD8+ por macrófagos, pero no por DC. Estos resultados son la primera evidencia de que StII encapsulada en liposomas funciona como una plataforma vacunal para inducir una respuesta de CTL robusta, con una contribución que va más allá de su habilidad de formar poros en membranas.

Sticholysins (Sts) I and II (StI and StII) are pore-forming proteins (PFPs), purified from the Caribbean Sea anemone Stichodactyla helianthus. StII encapsulated into liposomes induces a robust antigen-specific cytotoxic CD8+ T lymphocytes (CTL) response and in its free form the maturation of bone marrow-derived dendritic cells (BM-DCs). It is probable that the latter is partially supporting in part the immunomodulatory effect on the CTL response induced by StII-containing liposomes. In the present work, we demonstrate that the StII's ability of inducing maturation of BM-DCs is also shared by StI, an isoform of StII. Using heat-denatured Sts we observed a significant reduction in the up-regulation of maturation markers indicating that both PFP's ability to promote maturation of BM-DCs is dependent on their conformational characteristics. StII-mediated DC maturation was abrogated in BM-DCs from toll-like receptor (TLR) 4 and myeloid differentiation primary response gene 88 (MyD88)-knockout mice but not in cells from TLR2-knockout mice. Furthermore, the antigen-specific CTL response induced by StII-containing liposomes was reduced in TLR4-knockout mice. These results indicate that StII, and probably by extension StI, has the ability to induce maturation of DCs through a TLR4/MyD88-dependent pathway, and that this activation contributes to the CTL response generated by StII-containing liposomes.

Abstract Introduction: While combined immunotherapeutic activation of B and T cells is predicted to synergistically enhance both humoral and cell-mediated immunity, this has not been previously tested in human cancer patients. To assess this, we conducted the FIH trial combining B cell-activating IO (CIMAvax-EGF (C)) with T cell-activating IO (PD-1 blockade with nivolumab (N)). C activates B cells to produce endogenous anti-epidermal growth factor (EGF) antibodies (Abs) that deplete EGF from circulation. As a single agent maintenance therapy in aNSCLC, C prolonged overall survival (OS) in a randomized phase III trial. We now present immune correlates of improved OS with this novel combination. Methods: We reported safety and preliminary efficacy data from 13 pts from the phase I study of C+N (AACR 2019). Serial blood samples were analyzed by Luminex for dynamic changes in circulating cytokines and proteins implicated in EGF signaling, and by flow cytometry for peripheral blood mononuclear cell immunophenotype. Cox regression analysis was used to analyze association with OS. Results: 71% of pts achieved anti-EGF Ab titers of >1:4000 after 3 doses of C, compared to historical controls of 39% with C alone. Baseline increase in CD8+ naive T cells, memory B cells, and decrease in MDSC and Th17 T cells all significantly correlated with better OS. Baseline increase of inflammatory cytokines/markers (IL7, IL15, IFNα, IL8, sCD40L and CRP) significantly correlated with worse OS. Despite enrichment for pts with tumor proportion score (TPS) PD-L1 0%, median OS (mOS) of the intent-to-treat population (pts who received at least 1 dose of C+N, n=13) was 13.7 months (mo) vs. 9.9 mo in Checkmate 057 aNSCLC pts with tumor proportion score (TPS) PD-L1 <10%. mOS of per-protocol pts (all 4 loading doses of C+N given over 8 weeks, n=11) was 18.5 mo. In contrast to Checkmate 057 results, where OS benefit of N favored aNSCLC with KRAS mutation (KRASm), C+N showed better mOS of 22.4 mo in EGFR/ALK/KRAS wildtype (wt) pts versus 12.3 mo in KRASm/STKwt pts. Conclusion: This study provides evidence for synergistic effects of combining B and T cell activating IO in aNSCLC pts. C+N generated higher anti-EGF titers in more pts at an earlier time point vs. C alone, which is the first demonstration in pts of enhancement of Ab responses by immune checkpoint blockade. Immune analysis identified new specific immune cell populations and inflammatory markers that significantly correlate with OS with C+N that have not been previously identified with C or N as single agents. C+N improved OS compared to historical controls of aNSCLC pts receiving N in phase III trials. Of particular note, C+N showed better OS in pts with EGFR/ALK/KRAS wt aNSCLC versus KRASm/STKwt pts. The Phase II portion of the study is ongoing. Citation Format: Tania Crombet, Jason Muhitch, Circe Mesa, Rachel Evans, Danay S. Hernandez, Patricia L. Luaces, Zaima Mazorra, Orestes Morales, Carlos Cedeno, Aileen Cinquino, Daniel T. Fisher, Kelvin Lee, Mary Reid, Grace Dy. Evidence for synergistic immune responses in the first-in-human (FIH) combination of B cell-activating immunotherapy (IO) with anti-PD1 immune checkpoint inhibitor nivolumab (N) as 2nd-line therapy in patients (pts) with advanced non-small cell lung cancer (aNSCLC) [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT130.

Anti-CD20 treatment represents a therapeutic benefit for patients with B-cell lymphomas, although more efficient therapies are needed for refractory or relapsing patients. Among them, the combination of anti-CD20 and IL-2 that induces T cell response has been hampered by the expansion of FoxP3+ Tregs that strongly express the high affinity IL-2 receptor (IL-2R αβγ). We explore here the anti-tumor effect of an anti-CD20 antibody combined with a mutated IL-2 (no-alpha mutein) which has a disrupted affinity for the IL-2R αβγ. We demonstrate that anti-CD20/no-alpha mutein combination significantly augments the survival rate of mice challenged with huCD20+ cells as compared to animals treated with anti-CD20 ± IL-2. Moreover, the combination with no-alpha mutein but not IL-2 provokes an increase of granzyme B and perforin in splenic NK and CD8+ T cells, a reduction of Tregs and an increase in activated macrophages. The former combination also induces a T helper profile different from that obtained with IL-2, with an earlier polarization to Th1 and no increase in Th17. The therapeutic effect of anti-CD20/no-alpha mutein was accompanied by an expansion of peripheral central (TCM) and effector (TEM) memory CD8+ T cell compartments. Last, as opposed to IL-2, no-alpha mutein administered at the beginning of anti-CD20 treatment did not dampen the long-term protection of surviving mice after tumor rechallenge. Thus, this study shows that the combination of anti-tumor antibodies and no-alpha mutein is a promising approach to improve the therapeutic effect of these antibodies by potentiating NK/macrophage-mediated innate immunity and the adaptive T-cell response.

The GM3(Neu5Gc) ganglioside represents a tumor-specific antigen that is considered a promising target for cancer immunotherapy. We previously demonstrated that the humanized antibody 14F7hT, specific for this ganglioside, exhibited significant antitumor effects in preclinical hematological tumor models. As this antibody recognizes human tumor tissues from several origins, we addressed its potential effect on different tumor types. The use of cell lines for testing GM3(Neu5Gc)-targeting strategies, in particular for human malignancies, is complicated by the absence in humans of functional cytidine monophospho-N-acetyl-neuraminic acid hydroxylase (CMAH), the enzyme required for Neu5Gc sialic acid biosynthesis. Quantitative flow cytometry revealed the absence of surface GM3(Neu5Gc) in several human but also mouse cell lines, in the last case due to low expression of the enzyme. Hypoxia-induced expression of this ganglioside on human SKOV3 cells was observed upon culture in Neu5Gc-containing medium without evidence for CMAH-independent biosynthesis. However, only transfection of the mouse Cmah gene into human SKOV3 and mouse 3LL cells induced a stable expression of GM3(Neu5Gc) on the cancer cell surface, resulting in effective models to evaluate the antitumor responses by 14F7hT in vitro and in vivo. This antibody exerted antibody-dependent cell-mediated cytotoxicity (ADCC) and in vivo antitumor effects on these Cmah-transfected non-hematological tumors from both mouse and human origin. These results contribute to validate GM3(Neu5Gc) as a relevant target for cancer immunotherapy and reinforces the value of 14F7hT as a novel anti-cancer drug.

Unlike other regulatory circuits, cancer-induced myeloid dysfunction involves more than an accumulation of impaired dendritic cells, protumoral macrophages, and myeloid derived suppressor cells in the tumor microenvironment. It is also characterized by "aberrant" myelopoiesis that results in the accumulation and expansion of immature myeloid precursors with a suppressive phenotype in the systemic circulation. The first part of this review briefly describes the evidence for and consequences of this systemic dysfunctional myelopoiesis and the possible reinforcement of this phenomenon by conventional treatments used in patients with cancer, in particular chemotherapy and granulocyte-colony stimulating factor. The second half of this review describes very small size particles, a novel immune-modulatory nanoparticle, and the evidence indicating a possible role of this agent in correcting or re-programming the dysfunctional myelopoiesis in different scenarios.

Vaccine strategies to enhance CD8+ CTL responses remain a current challenge because they should overcome the plasmatic and endosomal membranes for favoring exogenous Ag access to the cytosol of APCs. As a way to avoid this hurdle, sticholysin (St) II, a pore-forming protein from the Caribbean Sea anemone Stichodactyla helianthus, was encapsulated with OVA into liposomes (Lp/OVA/StII) to assess their efficacy to induce a CTL response. OVA-specific CD8+ T cells transferred to mice immunized with Lp/OVA/StII experienced a greater expansion than when the recipients were injected with the vesicles without St, mostly exhibiting a memory phenotype. Consequently, Lp/OVA/StII induced a more potent effector function, as shown by CTLs, in vivo assays. Furthermore, treatment of E.G7-OVA tumor-bearing mice with Lp/OVA/StII significantly reduced tumor growth being more noticeable in the preventive assay. The contribution of CD4+ and CD8+ T cells to CTL and antitumor activity, respectively, was elucidated. Interestingly, the irreversibly inactive variant of the StI mutant StI W111C, encapsulated with OVA into Lp, elicited a similar OVA-specific CTL response to that observed with Lp/OVA/StII or vesicles encapsulating recombinant StI or the reversibly inactive StI W111C dimer. These findings suggest the relative independence between StII pore-forming activity and its immunomodulatory properties. In addition, StII-induced in vitro maturation of dendritic cells might be supporting these properties. These results are the first evidence, to our knowledge, that StII, a pore-forming protein from a marine eukaryotic organism, encapsulated into Lp functions as an adjuvant to induce a robust specific CTL response.

Gangliosides are sialic acid-bearing glycosphingolipids expressed on all mammalian cell membranes, and participate in several cellular processes. During malignant transformation their expression changes, both at the quantitative and qualitative levels. Of particular interest is the overexpression by tumor cells of Neu5Gc-gangliosides, which are absent, or detected in trace amounts, in human normal cells. The GM3(Neu5Gc) ganglioside in particular has been detected in many human tumors, and it is considered one of the few tumor specific antigen. We previously demonstrated that a humanized antibody specific for this molecule, named 14F7hT, retained the binding and cytotoxic properties of the mouse antibody. In this work, we confirm that 14F7hT exerts a non-apoptotic cell death mechanism in vitro and shows its potent in vivo antitumor activity on a solid mouse myeloma model. Also, we demonstrate, in contrast to the murine counterpart, the capacity of this antibody to induce antibody-dependent cell-mediated cytotoxicity using human effector cells, which increases its potential for the treatment of GM3(Neu5Gc)-expressing human tumors.

Cytosolic delivery strategies of antigens to antigen-presenting cells in order to improve the antigen-specific cytotoxic T lymphocyte (CTL) response are currently crucial in the development of anti-tumor and anti-intracellular infections vaccines. Promising strategies have employed the co-encapsulation into liposomes (LP) of bacterial pore-forming toxins (b-PFT) with antigens. Sticholysins (Sts) I and II are pore-forming isotoxins produced by the sea anemone Stichodactyla helianthus . Due to the functional homology of Sts with b-PFT, we studied the antigen-specific CTL-mediated immune response induced by LP co-encapsulating Sts with ovalbumin (OVA) as model antigen. Liposomes encapsulating OVA in the presence (LP/OVA+St) or not (LP/OVA) of Sts were used. Immunization of C57BL/6 mice with LP/OVA+St induced a remarkable CD8+ T-cell expansion and it enhanced significantly an OVA-specific CTL activity, in comparison with LP/OVA treatment. The CTL functionality was assessed using an OVA-expressing murine tumor model and in this scenario LP/OVA+St conferred a higher protection than LP/OVA. Besides, the CTL activity induced by LP/OVA+St was independent of CD4+ T-cells, while anti-tumor response was affected with depletion of the CD8+ T-cells. Interestingly, the inclusion into LP of a StI mutant forming a reversible-inactive dimmer stabilized by a disulphide bond also induced a similar antigen-specific CTL response, indicating the effectiveness of this safer alternative. Our results suggest the potentialities of Sts encapsulated into LP as a novel and promising antigen-cytosolic delivery system for priming CTL-mediated immune responses, which are keys in the immunity against infections and tumors.

Aberrant glycosylation is a key feature of malignant transformation and reflects epigenetic and genetic anomalies among the multitude of molecules involved in glycan biosynthesis. Although glycan biosynthesis is not template bound, altered tumor glycosylation is not random, but associated with common glycosylation patterns. Evidence suggests that acquisition of distinct glycosylation patterns evolves from a 'microevolutionary' process conferring advantages in terms of tumor growth, tumor dissemination, and immune escape. Such glycosylation modifications also involve xeno- and hypersialylation. Xeno-autoantigens such as Neu5Gc-gangliosides provide potential targets for immunotherapy. Hypersialylation may display 'enhanced self' to escape immunosurveillance and involves several not mutually exclusive inhibitory pathways that all rely on protein-glycan interactions. A better understanding of tumor 'glycan codes' as deciphered by lectins, such as siglecs, selectins, C-type lectins and galectins, may lead to novel treatment strategies, not only in cancer, but also in autoimmune disease or transplantation.

Adjuvants are a critical but largely overlooked and poorly understood component included in vaccine formulations to stimulate and modulate the desired immune responses to an antigen. However, unlike in the protective infectious disease vaccines, adjuvants for cancer vaccines also need to overcome the effect of tumor-induced suppressive immune populations circulating in tumor-bearing individuals. Myeloid-derived suppressor cells (MDSC) are considered to be one of the key immunosuppressive populations that inhibit tumor-specific T cell responses in cancer patients. This review focuses on the different signals for the activation of the immune system induced by adjuvants, and the close relationship to the mechanisms of recruitment and activation of MDSC. This work explores the possibility that a cancer vaccine adjuvant may either strengthen or weaken the effect of tumor-induced MDSC, and the crucial need to address this in present and future cancer vaccines.