A novel anti-B7-H3 chimeric antigen receptor from a single-chain antibody library for immunotherapy of solid cancers

B7-H3 (CD276) has emerged as a target for cancer immunotherapy by virtue of consistent expression in many malignancies, relative absence from healthy tissues, and an emerging role as a driver of tumor immune inhibition. Recent studies have reported B7-H3 to be a suitable target for chimeric antigen receptor-modified T cell (CAR-T) therapy using CARs constructed from established anti-B7-H3 antibodies converted into single-chain Fv format (scFv). We constructed and screened binders in an scFv library to generate a new anti-B7-H3 CAR-T with favorable properties. This allowed access to numerous specificities ready formatted for CAR evaluation. Selected anti-human B7-H3 scFvs were readily cloned into CAR-T and evaluated for anti-tumor reactivity in cytotoxicity, cytokine, and proliferation assays. Two binders with divergent complementarity determining regions were found to show optimal antigen-specific cytotoxicity and cytokine secretion. One binder in second-generation CD28-CD3ζ CAR format induced sustained in vitro proliferation on repeat antigen challenge. The lead candidate CAR-T also demonstrated in vivo activity in a resistant neuroblastoma model. An empirical approach to B7-H3 CAR-T discovery through screening of novel scFv sequences in CAR-T format has led to the identification of a new construct with sustained proliferative capacity warranting further evaluation.

Licensing of γδT cells for professional antigen presentation: A new role for antibodies in regulation of antitumor immune responses

Following activation, γδ T cells display many properties of lymphocytes from the innate immune system, yet how they mediate antigen presentation remains an open conundrum. In humans, circulating γδ T cells that express the Vγ9Vδ2 T-cell receptor become reversibly licensed for professional antigen presentation only upon interaction with a target cell opsonized with IgGs.

An Optimized GD2-Targeting Retroviral Cassette for More Potent and Safer Cellular Therapy of Neuroblastoma and Other Cancers

Neuroblastoma is the commonest extra cranial solid cancer of childhood. Despite escalation of treatment regimens, a significant minority of patients die of their disease. Disialoganglioside (GD2) is consistently expressed at high-levels in neuroblastoma tumors, which have been targeted with some success using therapeutic monoclonal antibodies. GD2 is also expressed in a range of other cancer but with the exception of some peripheral nerves is largely absent from non-transformed tissues. Chimeric Antigen Receptors (CARs) are artificial type I proteins which graft the specificity of a monoclonal antibody onto a T-cell. Clinical data with early CAR designs directed against GD2 have shown some promise in Neuroblastoma. Here, we describe a GD2-targeting CAR retroviral cassette, which has been optimized for CAR T-cell persistence, efficacy and safety.

Outcomes following gene therapy in patients with severe Wiskott-Aldrich syndrome

IMPORTANCE

Wiskott-Aldrich syndrome is a rare primary immunodeficiency associated with severe microthrombocytopenia. Partially HLA antigen-matched allogeneic hematopoietic stem cell (HSC) transplantation is often curative but is associated with significant comorbidity.

OBJECTIVE

To assess the outcomes and safety of autologous HSC gene therapy in Wiskott-Aldrich syndrome.

DESIGN, SETTING, AND PARTICIPANTS

Gene-corrected autologous HSCs were infused in 7 consecutive patients with severe Wiskott-Aldrich syndrome lacking HLA antigen-matched related or unrelated HSC donors (age range, 0.8-15.5 years; mean, 7 years) following myeloablative conditioning. Patients were enrolled in France and England and treated between December 2010 and January 2014. Follow-up of patients in this intermediate analysis ranged from 9 to 42 months.

INTERVENTION

A single infusion of gene-modified CD34+ cells with an advanced lentiviral vector.

MAIN OUTCOMES AND MEASURES

Primary outcomes were improvement at 24 months in eczema, frequency and severity of infections, bleeding tendency, and autoimmunity and reduction in disease-related days of hospitalization. Secondary outcomes were improvement in immunological and hematological characteristics and evidence of safety through vector integration analysis.

RESULTS

Six of the 7 patients were alive at the time of last follow-up (mean and median follow-up, 28 months and 27 months, respectively) and showed sustained clinical benefit. One patient died 7 months after treatment of preexisting drug-resistant herpes virus infection. Eczema and susceptibility to infections resolved in all 6 patients. Autoimmunity improved in 5 of 5 patients. No severe bleeding episodes were recorded after treatment, and at last follow-up, all 6 surviving patients were free of blood product support and thrombopoietic agonists. Hospitalization days were reduced from a median of 25 days during the 2 years before treatment to a median of 0 days during the 2 years after treatment. All 6 surviving patients exhibited high-level, stable engraftment of functionally corrected lymphoid cells. The degree of myeloid cell engraftment and of platelet reconstitution correlated with the dose of gene-corrected cells administered. No evidence of vector-related toxicity was observed clinically or by molecular analysis.

CONCLUSIONS AND RELEVANCE

This study demonstrated the feasibility of the use of gene therapy in patients with Wiskott-Aldrich syndrome. Controlled trials with larger numbers of patients are necessary to assess long-term outcomes and safety.

Polyphenon [corrected] E enhances the antitumor immune response in neuroblastoma by inactivating myeloid suppressor cells

PURPOSE

Neuroblastoma is a rare childhood cancer whose high risk, metastatic form has a dismal outcome in spite of aggressive therapeutic interventions. The toxicity of drug treatments is a major problem in this pediatric setting. In this study, we investigated whether Polyphenon E, a clinical grade mixture of green tea catechins under evaluation in multiple clinical cancer trials run by the National Cancer Institute (Bethesda, MD), has anticancer activity in mouse models of neuroblastoma.

EXPERIMENTAL DESIGN

We used three neuroblastoma models: (i) transgenic TH-MYCN mouse developing spontaneous neuroblastomas; (ii) nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice xenotransplanted with human SHSY5Y cells; and (iii) A/J mice transplanted with syngeneic Neuro 2A cells. Mice were randomized in control and Polyphenon E-drinking groups. Blood from patients with neuroblastoma and normal controls was used to assess the phenotype and function of myeloid cells.

RESULTS

Polyphenon E reduced the number of tumor-infiltrating myeloid cells, and inhibited the development of spontaneous neuroblastomas in TH-MYCN transgenic mice. In therapeutic models of neuroblastoma in A/J, but not in immunodeficient NOD/SCID mice, Polyphenon E inhibited tumor growth by acting on myeloid-derived suppressor cells (MDSC) and CD8 T cells. In vitro, Polyphenon E impaired the development and motility of MDSCs and promoted differentiation to more neutrophilic forms through the 67 kDa laminin receptor signaling and induction of granulocyte colony-stimulating factor. The proliferation of T cells infiltrating a patient metastasis was reactivated by Polyphenon E.

CONCLUSIONS

These findings suggest that the neuroblastoma-promoting activity of MDSCs can be manipulated pharmacologically in vivo and that green tea catechins operate, at least in part, through this mechanism.

Lack of T-cell responses following autologous tumour lysate pulsed dendritic cell vaccination, in patients with relapsed osteosarcoma

BACKGROUND

Immunotherapy using autologous dendritic cell (DC) vaccination has not been systematically evaluated in osteosarcoma. We therefore conducted a phase I trial to assess feasibility, safety and tumour-specific immune responses in patients with relapsed disease.

PATIENTS AND METHODS

Of 13 recruited patients with relapsed osteosarcoma, 12 received 3 weekly vaccines of autologous DCs matured with autologous tumour lysate and keyhole limpet haemocyanin (KLH), to a maximum of 6 vaccinations. An additional 3 paediatric patients afflicted with other tumour types and with relapsed disease received vaccines generated with identical methodology. Immune responses were assessed using an ELISpot assay for the detection of interferon gamma, whilst interleukin-2 and granzyme B were additionally assessed in cases where interferon-γ responses were induced.

RESULTS

In total 61 vaccines, of homogeneous maturation phenotype and viability, were administered with no significant toxicity. Only in 2 out of 12 treated osteosarcoma cases was there an induction of specific T-cell immune response to the tumour, whilst a strong but non-specific immune response was induced in 1 further osteosarcoma patient. Immune response against KLH was induced in only 3 out of 12 osteosarcoma patients. In contrast, three additional non-osteosarcoma patients showed significant T-cell responses to vaccine.

CONCLUSION

We have shown the strategy of DC vaccination in relapsed osteosarcoma is safe and feasible. However, significant anti-tumour responses were induced in only 2 out of 12 vaccinated patients with no evidence of clinical benefit. Comparison of results with identically treated control patients suggests that osteosarcoma patients might be relatively insensitive to DC-based vaccine treatments.

Licensing of killer dendritic cells in mouse and humans: functional similarities between IKDC and human blood γδ T-lymphocytes

Dendritic cells are characterized by the ability to induce primary antigen-specific immune responses in both major histocompatibility complex (MHC) Class I-restricted CD8 cells and MHC Class II-restricted CD4 cells. This professional antigen presentation function is associated with the up-regulation of co-stimulatory molecules and Class II MHC. While it has been recognized that several types of innate lymphocytes in mouse and humans can express co-stimulatory molecules and present antigen, the property of antigen presentation to elicit responses in naïve cells has been considered the exclusive domain of the dendritic cell. This concept has been challenged through the description of innate lymphocytes, capable of killing using NK receptors, but also up-regulating co-stimulatory molecules and driving the antigen-specific proliferation of naïve lymphocytes to the same extent as dendritic cells. Interferon (IFN)-γ secreting killer dendritic cells (IKDC) have been described in mice and share immunophenotypic properties of both dendritic cells and natural killer cells. Human blood γδ T-lymphocytes have innate tumor cell killing properties by both antibody-dependent and natural killer receptor-dependent mechanisms. This article reviews data from the authors' own laboratory showing a particular feature in common between the mouse IKDC and human blood γδ T-lymphocytes; namely their requirement for interaction with a target cell for specific licensing for professional antigen presentation.

Human γδ T lymphocytes are licensed for professional antigen presentation by interaction with opsonized target cells

Activated human blood γδ T cells have also been previously demonstrated to behave as professional APCs, although the processes that control APC function have not been characterized. n this study, we show that the acquisition of potent APC function by human blood γδ T cells is achieved after physical interaction with an Ab-coated target cell, a process that we refer to as licensing. In cancer models, licensing of γδ T cells by tumor-reactive mAbs promotes the uptake of tumor Ags and professional presentation to tumor-reactive αβ T cells. We propose that licensing by Ab is a mechanism whereby the adaptive properties of γδ T cells are induced by their innate functions in a spatially and temporally controlled manner.

Increased PRAME antigen-specific killing of malignant cell lines by low avidity CTL clones, following treatment with 5-Aza-2'-Deoxycytidine

The cancer testis antigen Preferentially Expressed Antigen of Melanoma (PRAME) is overexpressed in many solid tumours and haematological malignancies whilst showing minimal expression in normal tissues and is therefore a promising target for immunotherapy. HLA-A0201-restricted peptide epitopes from PRAME have previously been identified as potential immunogens to drive antigen-specific autologous CTL responses, capable of lysing PRAME expressing tumour cells. CTL lines, from 13 normal donors and 10 melanoma patients, all of whom were HLA-A0201 positive, were generated against the PRAME peptide epitope PRA(100-108). Specific killing activity against PRA(100-108) peptide-pulsed targets was weak compared with CTL lines directed against known immunodominant peptides. Moreover, limiting dilution cloning from selected PRAME-specific CTL lines resulted in the generation of a clone of only low to intermediate avidity. Addition of the demethylating agent 5-aza-2'-Deoxycytidine (DAC) increased PRAME expression in 7 out of 11 malignant cell lines including several B lineage leukaemia lines and also increased class I expression. Pre-treatment of target cells was associated with increased sensitivity to antigen-specific killing by the low avidity CTL. When CTL, as well as of the target cells, were treated, the antigen-specific killing was further augmented. Interestingly, one HLA-A0201-negative DAC-treated line (RAJI) showed increased sensitivity to killing by clones despite a failure of expression of PRAME or HLA-A0201. Together these data point to a general increased augmentation of cancer immunogenocity by DAC involving both antigen-specific and non-specific mechanisms.

Clusterin, a haploinsufficient tumor suppressor gene in neuroblastomas

BACKGROUND

Clusterin expression in various types of human cancers may be higher or lower than in normal tissue, and clusterin may promote or inhibit apoptosis, cell motility, and inflammation. We investigated the role of clusterin in tumor development in mouse models of neuroblastoma.

METHODS

We assessed expression of microRNAs in the miR-17-92 cluster by real-time reverse transcription-polymerase chain reaction in MYCN-transfected SH-SY5Y and SH-EP cells and inhibited expression by transfection with microRNA antisense oligonucleotides. Tumor development was studied in mice (n = 66) that were heterozygous or homozygous for the MYCN transgene and/or for the clusterin gene; these mice were from a cross between MYCN-transgenic mice, which develop neuroblastoma, and clusterin-knockout mice. Tumor growth and metastasis were studied in immunodeficient mice that were injected with human neuroblastoma cells that had enhanced (by clusterin transfection, four mice per group) or reduced (by clusterin short hairpin RNA [shRNA] transfection, eight mice per group) clusterin expression. All statistical tests were two-sided.

RESULTS

Clusterin expression increased when expression of MYCN-induced miR-17-92 microRNA cluster in SH-SY5Y neuroblastoma cells was inhibited by transfection with antisense oligonucleotides compared with scrambled oligonucleotides. Statistically significantly more neuroblastoma-bearing MYCN-transgenic mice were found in groups with zero or one clusterin allele than in those with two clusterin alleles (eg, 12 tumor-bearing mice in the zero-allele group vs three in the two-allele group, n = 22 mice per group; relative risk for neuroblastoma development = 4.85, 95% confidence interval [CI] = 1.69 to 14.00; P = .005). Five weeks after injection, fewer clusterin-overexpressing LA-N-5 human neuroblastoma cells than control cells were found in mouse liver or bone marrow, but statistically significantly more clusterin shRNA-transfected HTLA230 cells (3.27%, with decreased clusterin expression) than control-transfected cells (1.53%) were found in the bone marrow (difference = 1.74%, 95% CI = 0.24% to 3.24%, P = .026).

CONCLUSIONS

We report, to our knowledge, the first genetic evidence that clusterin is a tumor and metastasis suppressor gene.

Development of cellular immune responses against PAX5, a novel target for cancer immunotherapy

PAX5 is a member of the PAX family of developmental transcription factors with an important role in B-cell development. Its expression in normal adult tissue is limited to the hemopoietic system, but it is aberrantly expressed in a number of solid cancers and leukemias where it functions as an oncogene. We therefore hypothesized that anti-PAX5 immune responses could be used to target a number of malignancies without significant toxicity. We screened PAX5 peptides for the ability to bind HLA-A2 and identified a novel sequence, TLPGYPPHV (referred to as TLP). CTL lines against TLP were generated from peripheral blood of five normal HLA-A2-positive blood donors and showed specific HLA-A2-restricted killing against PAX5-expressing target cells. We generated high-avidity CTL clones from these lines capable of killing cells pulsed with <1 nmol/L of TLP and killing a range of PAX5-expressing malignant cell lines. I.v. injection of an anti-PAX5 CTL clone into immunodeficient mice bearing s.c. human tumors resulted in specific growth inhibition of PAX5-expressing tumors. This knowledge can be used for the therapeutic generation of CTL lines or the cloning of high-avidity T-cell receptor genes for use in adoptive immunotherapy.

MYCN as a target for cancer immunotherapy

MYCN is a potential target for cancer immunotherapy by virtue of its overexpression in numerous human malignancies and its functional role in tumour progression. Here we show limited expression of MYCN in normal human tissues indicating that anti-MYCN immune responses are unlikely to cross react with self tissues. An HLA-A2 restricted ten amino acid peptide epitope from MYCN, VILKKATEYV, was used to stimulate cytotoxic T cell lines from the peripheral blood of normal blood donors, and from a patient with MYCN amplified neuroblastoma. Strong and specific activity was seen against each MYCN overexpressing cell line and against autologous tumour cells. We generated two CTL clones capable of killing cells pulsed with as low as 0.5 nM of VIL peptide. Therefore strong and specific immune responses against MYCN expressing tumours are possible in patients with the most common HLA class 1 type in the Caucasian population.

Development of anti-PAX3 immune responses; a target for cancer immunotherapy

PAX3 is overexpressed in several human cancers and is absent from normal adult human tissues. It is known to have an oncogenic function in human malignancy, and is therefore a promising target for cancer immunotherapy. We screened the murine and human PAX3 amino acid sequences for peptides that bind common MHC class I types, and identified murine GVFINGRPL and human KLTEARVQV sequences. Mice immunised with either a selected PAX3 peptide, or with a PAX3 expressing DNA vector, developed specific anti-PAX3 immune responses that inhibited tumour growth. The intensity of the immune response was significantly enhanced by pulsing of the peptide onto dendritic cells. Anti-PAX3 T cell lines were established from splenocytes of immunised mice. Intravenous administration of anti-PAX3 T cells caused regression of established tumours indicating a promising clinical application for anti-PAX3 immunotherapy. The human peptide stimulated growth of similar T cell lines from peripheral blood of three out of three normal human blood donors. These showed specific cytotoxicity against a range of human PAX3+ and HLA-A2+ cancer cell lines. Moreover, an anti-PAX3 response was detected as a component of the anti-tumour immune response in a patient treated with lysate pulsed dendritic cell vaccination. The ability to generate strong and specific anti PAX3 immune responses from the T cell repertoire in both mice and humans, provides evidence for PAX3 as a promising target for immunotherapy of cancer.

Vaccine-induced early control of hepatitis C virus infection in chimpanzees fails to impact on hepatic PD-1 and chronicity

Broad T cell and B cell responses to multiple HCV antigens are observed early in individuals who control or clear HCV infection. The prevailing hypothesis has been that similar immune responses induced by prophylactic immunization would reduce acute virus replication and protect exposed individuals from chronic infection. Here, we demonstrate that immunization of naïve chimpanzees with a multicomponent HCV vaccine induced robust HCV-specific immune responses, and that all vaccinees exposed to heterologous chimpanzee-adapted HCV 1b J4 significantly reduced viral RNA in serum by 84%, and in liver by 99% as compared to controls (P=0.024 and 0.028, respectively). However, despite control of HCV in plasma and liver in the acute period, in the chronic phase, 3 of 4 vaccinated animals developed persistent infection. Analysis of expression levels of proinflammatory cytokines in serial hepatic biopsies failed to reveal an association with vaccine outcome. However, expression of IDO, CTLA-4 [corrected] and PD-1 levels in liver correlated with clearance or chronicity.

CONCLUSION

Despite early control of virus load, a virus-associated tolerogenic-like state can develop in certain individuals independent of vaccination history.

Coordinated oncogenic transformation and inhibition of host immune responses by the PAX3-FKHR fusion oncoprotein

Tumors have evolved elaborate mechanisms for evading immune detection, such as production of immunoinhibitory cytokines and down-regulation of major histocompatibility complex (MHC) expression. We have studied PAX3-FKHR as an example of an oncogenic fusion protein associated with an aggressive metastatic cancer. We show that PAX3-FKHR alters expression of genes that are normally regulated by Janus kinase/signal transducer and activator of transcription (STAT) signaling pathways. This occurs as a result of a specific interaction between PAX3-FKHR and the STAT3 transcription factor, which results in a dramatic reduction in tumor MHC expression, and an alteration in local cytokine concentrations to inhibit surrounding inflammatory cells and immune detection. Collectively, these data show that an oncogenic transcription factor can promote tumor growth and tissue invasion while inhibiting local inflammatory and immune responses. This is the first time that an immunomodulatory role has been described for an oncogenic fusion protein.

Modulation of Vaccine‐Induced Immune Responses to Hepatitis C Virus in Rhesus Macaques by Altering Priming before Adenovirus Boosting

BACKGROUND

Preventive and therapeutic vaccine strategies aimed at controlling hepatitis C virus (HCV) infection should mimic the immune responses observed in patients who control or clear HCV, specifically T helper (Th) type 1 and CD8+ cell responses to multiple antigens, including nonstructural protein (NS) 3. Given the experience with human immunodeficiency virus, the best candidates for this are based on DNA prime, pox, or adenovirus boost regimens.

METHODS

In rhesus macaques, we compared NS3-expressing DNA prime and adenovirus boost strategy with 2 alternative priming approaches aimed at modifying Th1 and CD8+ responses: DNA adjuvanted with interleukin (IL)-2- and -12-encoding plasmids or Semliki Forest virus (SFV).

RESULTS

All prime-boost regimens elicited NS3-specific B and T cell responses in rhesus macaques, including CD8+ responses. SFV priming induced higher lymphoproliferation and longer Th1 memory responses. The use of IL-2- and IL-12-expressing vectors resulted in reduced Th2 and antibody responses, which led to increased Th1 skewing but not to an increase in the magnitude of the IFN- gamma and CD8+ responses.

CONCLUSIONS

All strategies induced Th1 cellular responses to HCV NS3, with fine modulations depending on the different priming approaches. When they are developed for more HCV antigens, these strategies could be beneficial in therapeutic vaccine approaches.

Comparative immunogenicity analysis of modified vaccinia Ankara vectors expressing native or modified forms of hepatitis C virus E1 and E2 glycoproteins

We have evaluated in C57/Bl6 and HLA-A2.1 transgenic mice the immunogenicity of three MVA vectors expressing either native HCV E1E2 polyprotein, truncated and secreted E1 (E'1(311)) and E2 (E'2(661)) proteins, or a chimeric E1E2 heterodimer presented at the plasma membrane. Immunization induced mainly a Th1 response in HLA-A2.1 transgenic mice while a Th2-type response was detected in C57/Bl6 mice. Comparison of the three vectors shows an increase in the humoral response when antigens are secreted or membrane bound, and slightly in the cellular response when antigens are exposed on the cell surface.

Comparative vaccine studies in HLA-A2.1-transgenic mice reveal a clustered organization of epitopes presented in hepatitis C virus natural infection

A polyepitopic CD8(+)-T-cell response is thought to be critical for control of hepatitis C virus (HCV) infection. Using transgenic mice, we analyzed the immunogenicity and dominance of most known HLA-A2.1 epitopes presented during infection by using vaccines that carry the potential to enter clinical trials: peptides, DNA, and recombinant adenoviruses. The vaccines capacity to induce specific cytotoxic T lymphocytes and interferon gamma-producing cells revealed that immunogenic epitopes are clustered in specific antigens. For two key antigens, flanking regions were shown to greatly enhance the scope of epitope recognition, whereas a DNA-adenovirus prime-boost vaccination strategy augmented epitope immunogenicity, even that of subdominant ones. The present study reveals a clustered organization of HCV immunogenic HLA.A2.1 epitopes and strategies to modulate their dominance.

Mycobacterium smegmatis phosphoinositols-glyceroarabinomannans. Structure and localization of alkali-labile and alkali-stable phosphoinositides

Lipoarabinomannans from fast growing Mycobacterium sp., namely AraLAMs, stimulate the early events of macrophage activation. The immunological activities of all of these AraLAMs drastically decrease with the loss of the mild alkali groups, which were believed to be restricted to the fatty acid residues from the phosphatidyl-myo-inositol anchor. This report reveals the presence and the structure of mild alkali-labile phosphoinositide units linked via the phosphate to the C-5 of the beta-D-Araf in the AraLAMs of Mycobacterium smegmatis, a fast growing mycobacterial species. Their structure was unambiguously established with a strategy based on both one-dimensional 31P and two-dimensional 1H-31P heteronuclear multiple quantum correlation spectroscopy (HMQC) and HMQC-homonuclear Hartmann-Hahn spectroscopy NMR experiments applied to native AraLAMs and to AraLAMs treated in mild alkali conditions. Next to these alkali-labile phosphoinositides estimated at three per molecule, two other mild alkali-stable phosphoinositide units were identified: the expected (myo-inositol-1)-phosphate-(3-glycerol) unit typifying the well known glycosylphosphatidylinositol anchor of the mannan core and, more surprisingly, one (myo-inositol-1)-phosphate-(5-beta-D-Araf) unit having the same structure as the alkali-labile ones. Moreover, these four phosphoinositide units were found capping the arabinan side chains. Thus, their different behavior toward mild alkaline hydrolysis was explained according to their accessibility to the alkali reagent. This novel class of LAMs, namely phosphoinositols-glyceroarabinomannans (PI-GAMs), are characterized by their phosphoinositide units but also by the absence of fatty acid residues. These PI-GAMs were found to elicit the secretion of tumor necrosis factor-alpha, suggesting that phosphoinositides are the major PI-GAM epitope involved in this process.