Poxvirus Vectored Cytomegalovirus Vaccine to Prevent Cytomegalovirus Viremia in Transplant Recipients: A Phase 2, Randomized Clinical Trial.

Background: Triplex vaccine was developed to enhance cytomegalovirus (CMV)-specific T cells and prevent CMV reactivation early after hematopoietic stem cell transplant (HCT). Objective: To determine the safety and efficacy of Triplex. Design: First-in-patient, phase 2 trial. (ClinicalTrials.gov: NCT02506933). Setting: 3 U.S. HCT centers. Participants: 102 CMV-seropositive HCT recipients at high risk for CMV reactivation. Intervention: Intramuscular injections of Triplex or placebo were given on days 28 and 56 after HCT. Triplex is a recombinant attenuated poxvirus (modified vaccinia Ankara) expressing immunodominant CMV antigens. Measurements: The primary outcomes were CMV events (CMV DNA level ≥1250 IU/mL, CMV viremia requiring antiviral treatment, or end-organ disease), nonrelapse mortality, and severe (grade 3 or 4) graft-versus-host disease (GVHD), all evaluated through 100 days after HCT, and grade 3 or 4 adverse events (AEs) within 2 weeks after vaccination that were probably or definitely attributable to injection. Results: A total of 102 patients (51 per group) received the first vaccination, and 91 (89.2%) received both vaccinations (46 Triplex and 45 placebo). Reactivation of CMV occurred in 5 Triplex (9.8%) and 10 placebo (19.6%) recipients (hazard ratio, 0.46 [95% CI, 0.16 to 1.4]; P = 0.075). No Triplex recipient died of nonrelapse causes during the first 100 days or had serious AEs, and no grade 3 or 4 AEs related to vaccination were observed within 2 weeks after vaccination. Incidence of severe acute GVHD after injection was similar between groups (hazard ratio, 1.1 [CI, 0.53 to 2.4]; P = 0.23). Levels of long-lasting, pp65-specific T cells with effector memory phenotype were significantly higher in Triplex than placebo recipients. Limitation: The lower-than-expected incidence of CMV events in the placebo group reduced the power of the trial. Conclusion: No vaccine-associated safety concerns were identified. Triplex elicited and amplified CMV-specific immune responses, and fewer Triplex-vaccinated patients had CMV viremia. Primary Funding Source: National Cancer Institute and Helocyte.

Rapid Acquisition of Cytomegalovirus-Specific T Cells with a Differentiated Phenotype, in Nonviremic Hematopoietic Stem Transplant Recipients Vaccinated with CMVPepVax.

Early cytomegalovirus (CMV) reactivation remains a significant cause of morbidity and mortality in allogeneic hematopoietic cell transplant (HCT) recipients. CMVPepVax is an investigational peptide vaccine designed to control CMV infection in HCT recipients seropositive for CMV by stimulating the expansion of T cell subsets that target the CMV tegument protein pp65. In a randomized Phase Ib pilot trial (ClinicalTrials.gov NCT01588015), two injections of CMVPepVax (at days 28 and 56 post-HCT) demonstrated safety, immunogenicity, increased relapse-free survival, and reduced CMV reactivation and use of antivirals. In the present study, we assessed the phenotypes and time courses of the pp65-specific CD8 T cell subsets that expanded in response to CMVPepVax vaccination. The functionality and antiviral role of CMV-specific T cells have been linked to immune reconstitution profiles characterized predominantly by differentiated effector memory T (TEM) subsets that have lost membrane expression of the costimulatory molecule CD28 and often reexpress the RA isoform of CD45 (TEMRA). Major histocompatibility complex class I pp65495-503 multimers, as well as CD28 and CD45 memory markers, were used to detect immune reconstitution in blood specimens from HCT recipients enrolled in the Phase Ib clinical trial. Specimens from the 10 (out of 18) vaccinated patients who had adequate (≥.2%) multimer binding to allow for memory analysis showed highly differentiated TEM and TEMRA phenotypes for pp65495-503-specific CD8 T cells during the first 100days post-transplantation. In particular, by day 70, during the period of highest risk for CMV reactivation, combined TEM and TEMRA phenotypes constituted a median of 90% of pp65495-503-specific CD8 T cells in these vaccinated patients. CMV viremia was not detectable in the patients who received CMVPepVax, although their pp65495-503-specific CD8 T cell profiles were strikingly similar to those observed in viremic patients who did not receive the vaccine. Collectively, our findings indicate that in the absence of clinically relevant viremia, CMVPepVax reconstituted significant levels of differentiated pp65495-503-specific CD8 TEMs early post-HCT. Our data indicate that the rapid reconstitution of CMV-specific T cells with marked levels of effector phenotypes may have been key to the favorable outcomes of the CMVPepVax clinical trial.

p53-Reactive T Cells Are Associated with Clinical Benefit in Patients with Platinum-Resistant Epithelial Ovarian Cancer After Treatment with a p53 Vaccine and Gemcitabine Chemotherapy.

Purpose: To conduct a phase I trial of a Modified Vaccinia Ankara vaccine delivering wild-type human p53 (p53MVA) in combination with gemcitabine chemotherapy in patients with platinum-resistant ovarian cancer.Experimental Design: Patients received gemcitabine on days 1 and 8 and p53MVA vaccine on day 15, during the first 3 cycles of chemotherapy. Toxicity was classified using the NCI Common Toxicity Criteria and clinical response assessed by CT scan. Peripheral blood samples were collected for immunophenotyping and monitoring of anti-p53 immune responses.Results: Eleven patients were evaluated for p53MVA/gemcitabine toxicity, clinical outcome, and immunologic response. TOXICITY: there were no DLTs, but 3 of 11 patients came off study early due to gemcitabine-attributed adverse events (AE). Minimal AEs were attributed to p53MVA vaccination. Immunologic and clinical response: enhanced in vitro recognition of p53 peptides was detectable after immunization in both the CD4+ and CD8+ T-cell compartments in 5 of 11 and 6 of 11 patients, respectively. Changes in peripheral T regulatory cells (Tregs) and myeloid-derived suppressor cells (MDSC) did not correlate significantly with vaccine response or progression-free survival (PFS). Patients with the greatest expansion of p53-reactive T cells had significantly longer PFS than patients with lower p53-reactivity after therapy. Tumor shrinkage or disease stabilization occurred in 4 patients.Conclusions: p53MVA was well tolerated, but gemcitabine without steroid pretreatment was intolerable in some patients. However, elevated p53-reactive CD4+ and CD8+ T-cell responses after therapy correlated with longer PFS. Therefore, if responses to p53MVA can be enhanced with alternative agents, superior clinical responses may be achievable. Clin Cancer Res; 24(6); 1315-25. ©2018 AACR.

Complete regression of cutaneous metastases with systemic immune response in a patient with triple negative breast cancer receiving p53MVA vaccine with pembrolizumab.

A heavily pretreated patient with triple negative breast cancer distinguished by cutaneous metastases received p53MVA vaccine in combination with pembrolizumab. Her cutaneous metastases regressed and after 2 cycles of therapy, a skin biopsy showed a complete pathological response. Systemic response was confirmed with restaging CT and bone scans. Activation of p53-specific T cell responses and elevation of multiple immune response genes in peripheral blood correlated with the rapid clinical response which lasted for 6 months after the initiation of combined therapy.

MVA vaccine encoding CMV antigens safely induces durable expansion of CMV-specific T cells in healthy adults.

Attenuated poxvirus modified vaccinia Ankara (MVA) is a useful viral-based vaccine for clinical investigation, because of its excellent safety profile and property of inducing potent immune responses against recombinant (r) antigens. We developed Triplex by constructing an rMVA encoding 3 immunodominant cytomegalovirus (CMV) antigens, which stimulates a host antiviral response: UL83 (pp65), UL123 (IE1-exon4), and UL122 (IE2-exon5). We completed the first clinical evaluation of the Triplex vaccine in 24 healthy adults, with or without immunity to CMV and vaccinia virus (previous DryVax smallpox vaccination). Three escalating dose levels (DL) were administered IM in 8 subjects/DL, with an identical booster injection 28 days later and 1-year follow-up. Vaccinations at all DL were safe with no dose-limiting toxicities. No vaccine-related serious adverse events were documented. Local and systemic reactogenicity was transient and self-limiting. Robust, functional, and durable Triplex-driven expansions of CMV-specific T cells were detected by measuring T-cell surface levels of 4-1BB (CD137), binding to CMV-specific HLA multimers, and interferon-γ production. Marked and durable CMV-specific T-cell responses were also detected in Triplex-vaccinated CMV-seronegatives, and in DryVax-vaccinated subjects. Long-lived memory effector phenotype, associated with viral control during CMV primary infection, was predominantly found on the membrane of CMV-specific and functional T cells, whereas off-target vaccine responses activating memory T cells from the related herpesvirus Epstein-Barr virus remained undetectable. Combined safety and immunogenicity results of MVA in allogeneic hematopoietic stem cell transplant (HCT) recipients and Triplex in healthy adults motivated the initiation of a placebo-controlled multicenter trial of Triplex in HCT patients. This trial was registered at www.clinicaltrials.gov as #NCT02506933.

New Approaches for Immune Directed Treatment for Ovarian Cancer.

OPINION STATEMENT: The immune system plays an active role in the pathogenesis of ovarian cancer (OC), as well as in the mechanisms of disease progression and overall survival (OS). Immunotherapy in gynecological cancers could help to revert immunosuppression and lymphocyte depletion due to prior treatments. Current immunotherapies for ovarian cancer, like all cancer immunotherapy, are based on either stimulating the immune system or reverting immune suppression. Several approaches have been used, including therapeutic vaccines, monoclonal antibodies; checkpoint inhibitors and adoptive T cell transfer. Most of these therapies are still in early-phase testing (phase I and II) for ovarian cancer, but the initial data in ovarian cancer and successful use in other types of cancers suggests some of these approaches may ultimately prove useful for ovarian cancer as well. Ovarian cancer vaccines have shown only a modest benefit in ovarian cancer when used as monotherapy, but these agents may be able to enhance antitumor activity when combined with chemotherapy, checkpoint inhibitors, or other immunotherapies. Monoclonal antibodies have been explored in ovarian cancer but despite encouraging phase II data, randomized studies failed to demonstrate significant clinical benefit. Check point inhibitors have promising activity in several solid tumors and have demonstrated a favorable toxicity profile. Data from early clinical trials utilizing PD1 and PD-L1 inhibitors showed encouraging results. Ongoing clinical trials are evaluating the role of check point inhibitors in combination with chemotherapy. Adoptive T cell transfer involves the infusion of ex vivo activated and expanded tumor specific T cells, using various sources and types of T cells. While this approach has been explored in several hematologic malignancies, it constitutes early research in ovarian cancer. Immunotherapy remains investigational in ovarian cancer and the benefit of this approach in improving progression-free survival (PFS) or OS is unknown. Previous clinical trials have not selected patients based on biomarkers and this may explain the negative results. We expect to discover that tumor response will relate to the patient's immune features and specific tumor characteristics. We are only beginning to realize the potential of immunotherapy for ovarian cancer patients, and one goal of future clinical trials will be to identify subsets of patient based on histologic, molecular, and immune characteristics.

Analogue peptides for the immunotherapy of human acute myeloid leukemia.

The use of peptide vaccines, enhanced by adjuvants, has shown some efficacy in clinical trials. However, responses are often short-lived and rarely induce notable memory responses. The reason is that self-antigens have already been presented to the immune system as the tumor develops, leading to tolerance or some degree of host tumor cell destruction. To try to break tolerance against self-antigens, one of the methods employed has been to modify peptides at the anchor residues to enhance their ability to bind major histocompatibility complex molecules, extending their exposure to the T-cell receptor. These modified or analogue peptides have been investigated as stimulators of the immune system in patients with different cancers with variable but sometimes notable success. In this review we describe the background and recent developments in the use of analogue peptides for the immunotherapy of acute myeloid leukemia describing knowledge useful for the application of analogue peptide treatments for other malignancies.

p53MVA therapy in patients with refractory gastrointestinal malignancies elevates p53-specific CD8+ T-cell responses.

PURPOSE: To conduct a phase I trial of a modified vaccinia Ankara (MVA) vaccine delivering wild-type human p53 (p53MVA) in patients with refractory gastrointestinal cancers. EXPERIMENTAL DESIGN: Three patients were vaccinated with 1.0×10(8) plaque-forming unit (pfu) p53MVA followed by nine patients at 5.6×10(8) pfu. Toxicity was classified using the NCI Common Toxicity Criteria and clinical responses were assessed by CT scan. Peripheral blood samples were collected pre- and post-immunization for immunophenotyping, monitoring of p53MVA-induced immune response, and examination of PD1 checkpoint inhibition in vitro. RESULTS: p53MVA immunization was well tolerated at both doses, with no adverse events above grade 2. CD4+ and CD8+ T cells showing enhanced recognition of a p53 overlapping peptide library were detectable after the first immunization, particularly in the CD8+ T-cell compartment (P=0.03). However, in most patients, this did not expand further with the second and third immunization. The frequency of PD1+ T cells detectable in patients' peripheral blood mononuclear cells (PBMC) was significantly higher than in healthy controls. Furthermore, the frequency of PD1+ CD8+ T cells showed an inverse correlation with the peak CD8+ p53 response (P=0.02) and antibody blockade of PD1 in vitro increased the p53 immune responses detected after the second or third immunizations. Induction of strong T-cell and antibody responses to the MVA backbone were also apparent. CONCLUSION: p53MVA was well tolerated and induced robust CD8+ T-cell responses. Combination of p53MVA with immune checkpoint inhibition could help sustain immune responses and lead to enhanced clinical benefit.

Overcoming immunosuppression to enhance a p53MVA vaccine.

A Phase I trial of a p53-targeting modified vaccinia Ankara (p53MVA) vaccine in patients afflicted with refractory gastrointestinal cancers demonstrated enhanced T-cell recognition of p53 following vaccination. However, this effect was transient suggesting that p53MVA requires combination with immunomodulatory agents to deliver clinical benefit. Here, we outline our rationale for combining p53MVA with immunomodulatory chemotherapy in a forthcoming trial.

An analogue peptide from the Cancer/Testis antigen PASD1 induces CD8+ T cell responses against naturally processed peptide.

We have previously identified the novel Cancer/Testis antigen PASD1 by immunoscreening a testis library with pooled acute myeloid leukemia (AML) patient sera. To develop a cytotoxic T lymphocyte (CTL)-inducing vaccine, we have now investigated the carboxy-terminal region, known to contain serological determinants, for MHC class I (HLA-A⋆0201)-binding peptides. Algorithm-selected natural peptides failed to show detectable HLA-A⋆0201 binding in T2 assays. However, anchor-modified analogue peptides showed enhanced binding, with decreased off-rates. Analogue peptide-loaded antigen-presenting cells (APCs) induced IFN-γ production by T cells from normal donors and patients. In addition, peptide-specific T cells could be expanded from cancer patients by stimulation with the PASD1 analogue peptide Pa14. For clinical application, a DNA fusion gene vaccine encoding Pa14 was designed and tested in "humanized" mice. Splenocytes from vaccinated mice showed in vitro cytotoxicity against tumour cells, either exogenously loaded with the corresponding wild-type peptide (Pw8) or expressing endogenously processed PASD1 protein. We show for the first time that a DNA vaccine encoding an altered PASD1 epitope can induce CTLs to target the natural peptide expressed by human tumour cells.

Pre-clinical assessment of autologous DC-based therapy in ovarian cancer patients with progressive disease.

Dendritic cell-based vaccines offer promise for therapy of ovarian cancer. Previous studies have demonstrated that oxidation of several antigens, including ovarian cancer cells, using hypochlorous acid strongly enhances their immunogenicity and their uptake and presentation by dendritic cells. The response of T cells and dendritic cells to autologous tumour from patients with active disease has not previously been investigated. Monocyte-derived dendritic cells were generated from patients with active disease and activated by co-culture with oxidised tumour cells and the TLR agonist poly I:C. The dendritic cells showed an activated phenotype, but secreted high levels of TGFß. Co-culture of the antigen-loaded dendritic cells with autologous T cells generated a population of effector T cells that showed a low level of specific lytic activity against autologous tumour, as compared to autologous mesothelium. The addition of neutralising antibody to TGFß in DC/T cell co-cultures increased the levels of subsequent tumour killing in three samples tested. Co-culture of monocytes from healthy volunteers with the ovarian cell line SKOV-3 prior to differentiation into dendritic cells reduced the ability of dendritic cells to stimulate cytotoxic effector cells. The study suggests that co-culture of dendritic cells with oxidised tumour cells can generate effector cells able to kill autologous tumour, but that the high tumour burden in patients with active disease may compromise dendritic cell and/or T cell function.

Epitope spreading contributes to effective immunotherapy in metastatic melanoma patients.

In recent years, there have been reports of immunotherapy inducing objective clinical responses in limited numbers of cancer patients. More frequently, however, clinical responses are not observed. Understanding the immunological mechanisms underlying successful immunotherapy are crucial if the field is to move forward. In the article under evaluation, Coulie et al. examine the T-cell receptor repertoire in a melanoma patient showing durable remission after MAGE-specific immunotherapy. The paper provides convincing evidence that the phenomenon of epitope spreading is critical to the development of effective antitumor immunity.

Clinical evaluation of cellular immunotherapy in acute myeloid leukaemia.

Immunotherapy is currently under active investigation as an adjuvant therapy to improve the overall survival of patients with acute myeloid leukaemia (AML) by eliminating residual leukaemic cells following standard therapy. The graft-versus-leukaemia effect observed following allogeneic haematopoietic stem cell transplantation has already demonstrated the significant role of immune cells in controlling AML, paving the way to further exploitation of this effect in optimized immunotherapy protocols. In this review, we discuss the current state of cellular immunotherapy as adjuvant therapy for AML, with a particular focus on new strategies and recently published results of preclinical and clinical studies. Therapeutic vaccines that are being tested in AML include whole tumour cells as an autologous source of multiple leukaemia-associated antigens (LAA) and autologous dendritic cells loaded with LAA as effective antigen-presenting cells. Furthermore, adoptive transfer of cytotoxic T cells or natural killer cells is under active investigation. Results from phase I and II trials are promising and support further investigation into the potential of cellular immunotherapeutic strategies to prevent or fight relapse in AML patients.

Lytic activity against primary AML cells is stimulated in vitro by an autologous whole cell vaccine expressing IL-2 and CD80.

Despite being of the myeloid lineage, acute myeloid leukaemia (AML) blasts are of low immunogenicity, probably because they lack the costimulatory molecule CD80 and secrete immunosuppressive factors. We have previously shown that in vitro stimulation of autologous peripheral blood mononuclear cells (PBMCs) with primary AML cells modified to express CD80 and IL-2 promotes proliferation, secretion of Th1 cytokines and expansion of activated CD8(+) T cells. In this study, we show that allogeneic effector cells (from a healthy donor or AML patients) when stimulated with IL-2/CD80 modified AML blasts were able to induce the lysis of unmodified AML blasts. Effector cells stimulated with IL-2/CD80AML blasts had higher lytic activity than cells stimulated with AML cells expressing CD80 or IL-2 alone. Similarly, AML patient PBMCs primed with autologous IL-2/CD80 AML cells had a higher frequency of IFN-gamma secreting cells and show cytotoxicity against autologous, unmodified blasts. Crucially, the response appears to be leukaemia specific, since stimulated patient PBMCs show higher frequencies of IFN-gamma secreting effector cells in response to AML blasts than to remission bone marrow cells from the same patients. Although studied in a small number of heterogeneous patient samples, the data are encouraging and support the continuing development of vaccination for poor prognosis AML patients with autologous cells genetically modified to express IL-2/CD80.

Human CD80/IL2 lentivirus-transduced acute myeloid leukaemia (AML) cells promote natural killer (NK) cell activation and cytolytic activity: implications for a phase I clinical study.

Immunotherapeutic strategies may promote T and/or natural killer (NK) cell cytotoxicity. NK cells have the potential to exert a powerful anti-leukaemia effect, as demonstrated by studies of allogeneic transplantation. We have previously shown that CD80/interleukin 2 (IL2) lentivirus (LV)-transduced AML cells stimulate in-vitro T cell activation. The present study demonstrated that allogeneic and autologous culture of peripheral blood mononuclear cells with CD80/IL2-expressing AML cells also promoted NK cell cytotoxicity. Expression of the activation receptors NKp30, NKp44, CD244, CD25, CD69 and HLA-DR significantly increased following allogeneic culture and a consistent increased expression of NKp30, NKp44, NKp46, NKG2D, NKG2C and CD69, and up-regulation of the cytolytic marker CD107a was detected following autologous culture with LV-CD80/IL2 AML cells. Furthermore, increased NK cell lysis of K562 and primary AML blasts was detected. The lytic activity increased by twofold against K562 (from 46.6% to 90.4%) and allogeneic AML cells (from 11.8% to 20.1%) following in-vitro stimulation by CD80/IL2-expressing AML cells. More importantly for potential therapeutic applications, lysis of primary AML cells by autologous NK cells increased by more than 40-fold (from 0.4% to 22.5%). These studies demonstrated that vaccination of patients with CD80/IL2-transduced AML cells could provide a powerful strategy for T/NK cell-mediated stimulation of anti-leukaemic immunological responses.

Human CD80/IL2 lentivirus transduced acute myeloid leukaemia cells enhance cytolytic activity in vitro in spite of an increase in regulatory CD4+ T cells in a subset of cultures.

Immunotherapeutic strategies are increasingly being explored as a method of enhancing anti-tumour immune responses in patients with acute myeloid leukaemia (AML). Regulatory CD4(+) T cells (Tregs) suppress effector T and natural killer (NK) cells and therefore pose a potential challenge to the efficacy of immunotherapy. AML cells transduced with a lentivirus expressing CD80 (B7.1) and IL2 (LV-CD80/IL2) are capable of stimulating T and NK cell cytotoxicity in vitro. This study examines the effect of CD80/IL2 modified AML cells on Treg number and function. We report a significant increase in the number of CD8(+) T cells (P = 0.046) CD3(-)CD56(+) NK cells (P = 0.028) and CD3(+)CD4(+)CD25(high)Foxp3(+) Tregs (P = 0.043) following stimulation for 7 days with allogeneic LV-CD80/IL2 AMLs. In contrast, autologous LV-CD80/IL2 AML cell cultures provide a weaker stimulation with a lower number of CD8(+) T cells (P = 0.011) and no change in NK cell or Treg numbers. However, an increase in cytotoxic CD8(+) T cells and NK cells are detected following both allogeneic and autologous LV-CD80/IL2 stimulation as demonstrated by an increase in IFN-gamma and CD107a expression. Despite the presence of increased numbers of Tregs with suppressive activity in a subset of cultures, increased lysis of unmodified AMLs was still achieved following allogeneic (day 0, 2.2%; day 7, 20.4%) and more importantly, autologous LV-CD80/IL2 culture in which AML patients had recently received intensive chemotherapy (day 0, 0%; day 7, 16%). Vaccination with LV-CD80/IL2 therefore provides a potential strategy to enhance anti-leukaemia immune responses without a concomitant stimulation of Treg-mediated inhibition of cytotoxic immunological responses.

Generation in vivo of peptide-specific cytotoxic T cells and presence of regulatory T cells during vaccination with hTERT (class I and II) peptide-pulsed DCs.

BACKGROUND: Optimal techniques for DC generation for immunotherapy in cancer are yet to be established. Study aims were to evaluate: (i) DC activation/maturation milieu (TNF-alpha +/- IFN-alpha) and its effects on CD8+ hTERT-specific T cell responses to class I epitopes (p540 or p865), (ii) CD8+ hTERT-specific T cell responses elicited by vaccination with class I alone or both class I and II epitope (p766 and p672)-pulsed DCs, prepared without IFN-alpha, (iii) association between circulating T regulatory cells (Tregs) and clinical responses. METHODS: Autologous DCs were generated from 10 patients (HLA-0201) with advanced cancer by culturing CD14+ blood monocytes in the presence of GM-CSF and IL-4 supplemented with TNF-alpha [DCT] or TNF-alpha and IFN-alpha [DCTI]. The capacity of the DCs to induce functional CD8+ T cell responses to hTERT HLA-0201 restricted nonapeptides was assessed by MHC tetramer binding and peptide-specific cytotoxicity. Each DC preparation (DCT or DCTI) was pulsed with only one type of hTERT peptide (p540 or p865) and both preparations were injected into separate lymph node draining regions every 2-3 weeks. This vaccination design enabled comparison of efficacy between DCT and DCTI in generating hTERT peptide specific CD8+ T cells and comparison of class I hTERT peptide (p540 or p865)-loaded DCT with or without class II cognate help (p766 and p672) in 6 patients. T regulatory cells were evaluated in 8 patients. RESULTS: (i) DCTIs and DCTs, pulsed with hTERT peptides, were comparable (p = 0.45, t-test) in inducing peptide-specific CD8+ T cell responses. (ii) Class II cognate help, significantly enhanced (p < 0.05, t-test) peptide-specific CD8+T cell responses, compared with class I pulsed DCs alone. (iii) Clinical responders had significantly lower (p < 0.05, Mann-Whitney U test) T regs, compared with non-responders. 4/16 patients experienced partial but transient clinical responses during vaccination. Vaccination was well tolerated with minimal toxicity. CONCLUSION: Addition of IFN-alpha to ex vivo monocyte-derived DCs, did not significantly enhance peptide-specific T cell responses in vivo, compared with TNF-alpha alone. Class II cognate help significantly augments peptide-specific T cell responses. Clinically favourable responses were seen in patients with low levels of circulating T regs.

An immune edited tumour versus a tumour edited immune system: Prospects for immune therapy of acute myeloid leukaemia.

Cell based therapies for acute myeloid leukaemia (AML) have made significant progress in the last decade benefiting the prognosis and survival of patients with this aggressive form of leukaemia. Due to advances in haematopoietic stem cell transplantation (HSCT) and particularly the advent of reduced intensity conditioning (RIC), the scope of transplantation has now extended to those patients previously ineligible due to age and health restrictions and has been associated with a decrease in transplant related mortality. The apparent graft versus leukaemia (GvL) effect observed following HSCT demonstrates the potential of the immune system to target and eradicate AML cells. Building on previously published pre-clinical studies by ourselves and others, we are now initiating a Phase I clinical study in which lentiviral vectors are used to genetically modify AML cells to express B7.1 (CD80) and IL-2. By combining allogeneic HSCT with immunisation, using the autologous AML cells expressing B7.1 and IL-2, we hope to stimulate immune eradication of residual AML cells in poor prognosis patients that have achieved donor chimerism. In this report we describe the background to cell therapy based approaches for AML, and discuss difficulties associated with the deployment of a chronically stimulated, hence exhausted/depleted immune system to eradicate tumour cells that have already escaped immune surveillance.

IL-2/B7.1 (CD80) fusagene transduction of AML blasts by a self-inactivating lentiviral vector stimulates T cell responses in vitro: a strategy to generate whole cell vaccines for AML.

Combined expression of costimulatory factors and proinflammatory cytokines stimulate effective immune-mediated tumor rejection in a variety of murine tumor models. Specifically, syngeneic tumor cells genetically modified to express B7.1 (CD80) have been shown to induce rejection of previously established murine solid tumors, and transduction with IL-2 can further increase survival. However, poor rates of gene transfer and inefficient expression of multiple transgenes encoded by single vectors have hampered the development of such autologous tumor cell vaccines for clinical trials in acute myeloid leukemia (AML) patients. Here we describe the development of a self-inactivating lentiviral vector encoding B7.1 and IL-2 as a single fusion protein postsynthetically cleaved to generate biologically active membrane-anchored B7.1 and secreted IL-2. This enables the efficient transduction of both established and primary AML blasts, resulting in expression of the transgenes in up to 98% of the cells following a single round of infection at an m.o.i. of 10. The combined expression of IL-2 and B7.1 in AML blasts enables increased stimulation of both allogeneic and autologous T cells. The stimulated lymphocytes secrete greater levels of Th1 cytokines and show evidence of specificity, as indicated by their increased proliferation in the presence of autologous AML compared to remission bone marrow cells.