Applications and Limitations of Equilibrium Density Gradient Analytical Ultracentrifugation for the Quantitative Characterization of Adeno-Associated Virus Vectors

Adeno-associated virus (AAV) vectors are produced as a mixture of the desired particle (full particle, FP), which is filled with the designed DNA, product-related impurities such as particle without DNA (empty particle, EP), and aggregates. Cesium chloride or iodixanol equilibrium density gradient ultracentrifugation (DGE-UC) has been used for the purification of AAV vectors. DGE-UC can separate FP from impurities based on the difference in their buoyant densities. Here, we report the applications and limitations of equilibrium density gradient analytical ultracentrifugation (DGE-AUC) using a modern AUC instrument that employs DGE-UC principles for the characterization and quantitation of AAV vectors. We evaluated the quantitative ability of DGE-AUC in comparison with sedimentation velocity AUC (SV-AUC) or band sedimentation AUC (BS-AUC) using AAVs with different DNA lengths and different serotypes. DGE-AUC enabled the accurate quantification of the ratio of FP to EP when the AAV vector primarily contains these particles. Furthermore, we developed a new workflow to identify the components of separated peaks in addition to FP and EP. Ultraviolet absorption spectra obtained by multiwavelength detection can also support peak assignment following component identification. DGE-AUC experiments for AAV vectors have limitations with regard to minor components with low absorption at the detected wavelength or those with a density similar to that of major components of AAV vectors. DGE-AUC is the only analytical method that can evaluate particle density heterogeneity; therefore, SV-AUC or BS-AUC and DGE-AUC are complementary methods for reliable assessment of the purity of AAV vectors.

Exhaustion, rather than lack of infiltration and persistence, of CAR-T cells hampers the efficacy of CAR-T therapy in an orthotopic PDAC xenograft model

Chimeric antigen receptor T-cell (CAR-T) therapy has demonstrated impressive success in the treatment of patients with hematologic tumors yet achieved very limited efficacy for solid tumors due to hurdles unique to solid tumors. It is also noted that the tumor microenvironment composition varies between tumor type, which again imposes unique set of hurdles in each solid tumor. Therefore, elucidation of individual hurdles is key to achieving successful CAR-T therapy for solid tumors. In the present study, we employed an orthotopic human PDAC xenograft model, in which quantitative, spatial and functional dynamics of CAR-T cells in tumor tissues were analyzed to obtain insights into ways of overcoming PDAC related hurdles. Contrary to previous studies that demonstrated a limited persistency and infiltration of CAR-T cells in many solid tumors, they persist and accumulated in PDAC tumor tissues. Ex vivo analysis revealed that CAR-T cells that had been recovered at different time points from mice bearing an orthotopic PDAC tumor exhibited a gradual loss of tumor reactivity. This loss of tumor reactivity of CAR-T cells was associated with the increased expression of AMP-activated protein kinase and Mitofusin 1/ Dynamin-related protein 1 ratio.

T cell receptor gene-modified allogeneic T cells with siRNA for endogenous T cell receptor induce efficient tumor regression without graft-versus-host disease

Adoptive immunotherapy using genetically engineered patient-derived lymphocytes to express tumor-reactive receptors is a promising treatment for malignancy. However, utilization of autologous T cells in this therapy limits the quality of gene-engineered T cells, thereby inhibiting the timely infusion of the cells into patients. In this study, we evaluated the anti-tumor efficacy and the potential to induce graft-versus-host disease (GVHD) in T cell receptor (TCR) gene-engineered allogeneic T cells that downregulate the endogenous TCR and HLA class I molecules with the aim of developing an "off-the-shelf" cell product with expanded application of genetically engineered T cells. We transduced human lymphocytes with a high-affinity TCR specific to the cancer/testis antigen NY-ESO-1 using a novel retrovirus vector with siRNAs specific to the endogenous TCR (siTCR vector). These T cells showed reduced expression of endogenous TCR and minimized reactivity to allogeneic cells in vitro. In non-obese diabetic/SCID/γcnull mice, TCR gene-transduced T cells induced tumor regression without development of GVHD. A lentivirus-based CRISPR/Cas9 system targeting β-2 microglobulin in TCR gene-modified T cells silenced the HLA class I expression and prevented allogeneic CD8+ T cell stimulation without disrupting their anti-tumor capacity. This report is the first demonstration that siTCR technology is effective in preventing GVHD. Adoptive cell therapy with allogeneic T cells engineered with siTCR vector may be useful in developing an "off-the-shelf" therapy for patients with malignancy.

Intradermal administration of DNA vaccine targeting Omicron SARS-CoV-2 via pyro-drive jet injector provides the prolonged neutralizing antibody production via germinal center reaction

Emerging SARS-CoV-2 Omicron variants are highly contagious with enhanced immune escape mechanisms against the initially approved COVID-19 vaccines. Therefore, we require stable alternative-platform vaccines that confer protection against newer variants of SARS-CoV-2. We designed an Omicron B.1.1.529 specific DNA vaccine using our DNA vaccine platform and evaluated the humoral and cellular immune responses. SD rats intradermally administered with Omicron-specific DNA vaccine via pyro-drive jet injector (PJI) thrice at 2-week intervals elicited high antibody titers against the Omicron subvariants as well as the ancestral strain. Indeed, the Omicron B.1.1.529-specific antibody titer and neutralizing antibody were higher than that of other strains. Longitudinal monitoring indicated that anti-spike (ancestral and Omicron) antibody titers decreased toward 30 weeks after the first vaccination dose. However, neutralization activity remained unaltered. Germinal center formation was histologically detected in lymph nodes in rats immunized with Omicron DNA vaccine. Ancestral spike-specific immune cell response was slightly weaker than Omicron spike-specific response in splenocytes with Omicron-adapted DNA vaccine, evaluated by ELISpot assay. Collectively, our findings suggest that Omicron targeting DNA vaccines via PJI can elicit robust durable antibody production mediated by germinal center reaction against this new variant as well as partially against the spike protein of other SARS-CoV-2 variants.

CAR-Modified Vγ9Vδ2 T Cells Propagated Using a Novel Bisphosphonate Prodrug for Allogeneic Adoptive Immunotherapy

The benefits of CAR-T therapy could be expanded to the treatment of solid tumors through the use of derived autologous αβ T cell, but clinical trials of CAR-T therapy for patients with solid tumors have so far been disappointing. CAR-T therapy also faces hurdles due to the time and cost intensive preparation of CAR-T cell products derived from patients as such CAR-T cells are often poor in quality and low in quantity. These inadequacies may be mitigated through the use of third-party donor derived CAR-T cell products which have a potent anti-tumor function but a constrained GVHD property. Vγ9Vδ2 TCR have been shown to exhibit potent antitumor activity but not alloreactivity. Therefore, in this study, CAR-T cells were prepared from Vγ9Vδ2 T (CAR-γδ T) cells which were expanded by using a novel prodrug PTA. CAR-γδ T cells suppressed tumor growth in an antigen specific manner but only during a limited time window. Provision of GITR co-stimulation enhanced anti-tumor function of CAR-γδ T cells. Our present results indicate that, while further optimization of CAR-γδ T cells is necessary, the present results demonstrate that Vγ9Vδ2 T cells are potential source of 'off-the-shelf' CAR-T cell products for successful allogeneic adoptive immunotherapy.

Adeno-associated virus vector system controlling capsid expression improves viral quantity and quality

Adeno-associated virus (AAV) vectors are promising tools for gene therapy. The current AAV vector system produces an abundance of empty capsids that are eliminated before clinical use, leading to increased costs for gene therapy. In the present study, we established an AAV production system that regulates the timing of capsid expression using a tetracycline-dependent promoter. Tetracycline-regulating capsid expression increased viral yield and reduced empty capsids in various serotypes without altering AAV vector infectivity in vitro and in vivo. The replicase expression pattern change observed in the developed AAV vector system improved viral quantity and quality, whereas timing control of capsid expression reduced empty capsids. These findings provide a new perspective on the development of AAV vector production systems in gene therapy.

Tumor Growth Suppression of Pancreatic Cancer Orthotopic Xenograft Model by CEA-Targeting CAR-T Cells

Chimeric antigen receptor engineered T cell (CAR-T) therapy has high therapeutic efficacy against blood cancers, but it has not shown satisfactory results in solid tumors. Therefore, we examined the therapeutic effect of CAR-T therapy targeting carcinoembryonic antigen (CEA) in pancreatic adenocarcinoma (PDAC). CEA expression levels on the cell membranes of various PDAC cell lines were evaluated using flow cytometry and the cells were divided into high, medium, and low expression groups. The relationship between CEA expression level and the antitumor effect of anti-CEA-CAR-T was evaluated using a functional assay for various PDAC cell lines; a significant correlation was observed between CEA expression level and the antitumor effect. We created orthotopic PDAC xenograft mouse models and injected with anti-CEA-CAR-T; only the cell line with high CEA expression exhibited a significant therapeutic effect. Thus, the therapeutic effect of CAR-T therapy was related to the target antigen expression level, and the further retrospective analysis of pathological findings from PDAC patients showed a correlation between the intensity of CEA immunostaining and tumor heterogeneity. Therefore, CEA expression levels in biopsies or surgical specimens can be clinically used as biomarkers to select PDAC patients for anti-CAR-T therapy.

Modified DNA vaccine confers improved humoral immune response and effective virus protection against SARS-CoV-2 delta variant

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has led to a global pandemic. New technologies have been utilized to develop several types of vaccines to prevent the spread of SARS-CoV-2 infection, including mRNA vaccines. Our group previously developed an effective DNA-based vaccine. However, emerging SARS-CoV-2 variants of concern (VOCs), such as the delta variant, have escaped mutations against vaccine-induced neutralizing antibodies. This suggests that modified vaccines accommodating VOCs need to be developed promptly. Here, we first modified the current DNA vaccine to enhance antigenicity. Compared with the parental DNA vaccine, the modified version (GP∆-DNA vaccine) induced rapid antibody production. Next, we updated the GP∆-DNA vaccine to spike glycoprotein of the delta variant (GP∆-delta DNA vaccine) and compared the efficacy of different injection routes, namely intramuscular injection using a needle and syringe and intradermal injection using a pyro-drive jet injector (PJI). We found that the levels of neutralizing antibodies induced by the intradermal PJI injection were higher than intramuscular injection. Furthermore, the PJI-injected GP∆-delta DNA vaccine effectively protected human angiotensin-converting enzyme 2 (hACE2) knock-in mice from delta-variant infection. These results indicate that the improved DNA vaccine was effective against emerging VOCs and was a potential DNA vaccine platform for future VOCs or global pandemics.

Immune response induced in rodents by anti-CoVid19 plasmid DNA vaccine via pyro-drive jet injector inoculation

There is an urgent need to stop the coronavirus disease 2019 (COVID-19) pandemic through the development of efficient and safe vaccination methods. Over the short term, plasmid DNA vaccines can be developed as they are molecularly stable, thus facilitating easy transport and storage. pVAX1-SARS-CoV2-co was designed for the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) S protein. The antibodies produced led to immunoreactions against the S protein, an anti-receptor-binding-domain, and a neutralizing action of the pVAX1-SARS-CoV2-co, as previously confirmed. To promote the efficacy of the pVAX1-SARS-CoV2-co vaccine a pyro-drive jet injector (PJI) was used. An intradermally adjusted PJI demonstrated that the pVAX1-SARS-CoV2-co vaccine injection caused a high production of anti-S protein antibodies, triggered immunoreactions, and neutralized the actions against SARS-CoV-2. A high-dose pVAX1-SARS-CoV2-co intradermal injection using PJI did not cause any serious disorders in the rat model. A viral challenge confirmed that intradermally immunized mice were potently protected from COVID-19. A pVAX1-SARS-CoV2-co intradermal injection using PJI is a safe and promising vaccination method for overcoming the COVID-19 pandemic.

NY-ESO-1-specific redirected T cells with endogenous TCR knockdown mediate tumor response and cytokine release syndrome

Background

Because of the shortage of ideal cell surface antigens, the development of T-cell receptor (TCR)-engineered T cells (TCR-T) that target intracellular antigens such as NY-ESO-1 is a promising approach for treating patients with solid tumors. However, endogenous TCRs in vector-transduced T cells have been suggested to impair cell-surface expression of transduced TCR while generating mispaired TCRs that can become self-reactive.

Methods

We conducted a first-in-human phase I clinical trial with the TCR-transduced T-cell product (TBI-1301) in patients with NY-ESO-1-expressing solid tumors. In manufacturing TCR-T cells, we used a novel affinity-enhanced NY-ESO-1-specific TCR that was transduced by a retroviral vector that enables siRNA (small interfering RNA)-mediated silencing of endogenous TCR. The patients were divided into two cohorts. Cohort 1 was given a dose of 5×10⁸ cells (whole cells including TCR-T cells) preconditioned with 1500 mg/m² cyclophosphamide. Cohort 2 was given 5× 10⁹ cells preconditioned with 1500 mg/m² cyclophosphamide.

Results

In vitro study showed that both the CD8⁺ and CD4⁺ T fractions of TCR-T cells exhibited cytotoxic effects against NY-ESO-1-expressing tumor cells. Three patients and six patients were allocated to cohort 1 and cohort 2, respectively. Three of the six patients who received 5×10⁹ cells showed tumor response, while three patients developed early-onset cytokine release syndrome (CRS). One of the patients developed a grade 3 lung injury associated with the infiltration of the TCR-T cells. No siRNA-related adverse events other than CRS were observed. Cytokines including interleukin 6 I and monocyte chemotactic protein-1/chemokine (C-C motif) ligand (CCL2)

increased in the sera of patients with CRS. In vitro analysis showed these cytokines were not secreted from the T cells infused. A significant fraction of the manufactured T cells in patients with CRS was found to express either CD244, CD39, or both at high levels.

Conclusions

The trial showed that endogenous TCR-silenced and affinity-enhanced NY-ESO-1 TCR-T cells were safely administered except for grade 3 lung injury. The TCR-T cell infusion exhibited significant tumor response and early-onset CRS in patients with tumors that express NY-ESO-1 at high levels. The differentiation properties of the manufactured T cells may be prognostic for TCR-T-related CRS.

Trial registration number

NCT02366546.

103 Quality improvement of anti-CD38-JAK/STAT CAR-T cells by suppressing CD38 expression and inhibition of tyrosine kinase

Background

CAR-T cell therapy has shown highly effective clinical results in several diseases, but further improvement is necessary to target a wider range of antigens and tumors. In particular, excessive activation of CAR-T cells leads to cell exhaustion and reduction of naive/memory T cells’ population, which are important for long-term immune response. Therefore, suppressing non-antigen-specific activity is necessary for CAR-T cell production. However, when targeting tumor-related antigens that are also expressed on T cells, CAR-T cells recognize the antigens on the T cells, resulting in fratricide, poor cell growth, differentiation, and exhaustion during cell production process.In this study, we investigated a method for producing CAR-T cells targeting CD38 antigen that is common to T cells and tumor cells. CD38 is a suitable target antigen for CAR-T cell therapy because it is highly expressed in lymphocyte malignant tumors including B-cell non-Hodgkin’s lymphoma and multiple myeloma. However, as it is also intermediately expressed in normal blood cells, unwanted activation of CAR-T cells may be caused.

Methods

We tried to suppress the expression of CD38 in CAR-T cells by co-expressing CD38 siRNAs, and prevent activation during cell production by modifying the signal domain of anti-CD38-CAR to the newly developed JAK/STAT-CAR. JAK/STAT-CAR contains the intracellular domain of the IL-2 receptor β chain and the STAT3 binding motif, which have been shown to improve the proliferation of CAR-T cells and suppresses differentiation compared to conventional second-generation CAR-T cells.For further improvement, CAR-T cells were prepared in the presence of the tyrosine kinase inhibitor Dasatinib to suppress activation during the cell manufacturing process.

Results

CD38 siRNA co-expressing CAR-T cells showed decreased expression of CD38 and exhaustion markers, and the further reduction of exhaustion marker expression was observed in JAK/STAT CAR-T cells. However, compared to CAR-T cells targeting other antigens, CD38-CAR-T cells tended to be more exhausted and differentiated. As Dasatinib treatment maintained a high proportion of naive/memory T cells and was able to suppress exhaustion, combination of these approaches (CD38 siRNA-expressing CD38-JAK/STAT CAR-T cells with Dasatinib treatment) showed long-term persistence of antitumor activity in in vitro re-challenge assay.

Conclusions

CD38 siRNA co-expressing CD38-JAK/STAT CAR-T cells produced in the presence of a tyrosine kinase inhibitor are expected to be suppressed excessive activation and maintain long-term antigen-specific activity. This approach is also expected to be applied to other CAR-T cell therapies targeting tumor-related antigens expressed on T cells.

64 A cloning and expression system of the neoantigen-specific TCRs from tumor-infiltrating lymphocytes by single-cell sequencing of paired TCRα and TCRβ chains

Background

T-cells that target tumor neoantigens arising from cancer mutations are the primary mediators of cancer immunotherapies. Identifying neoantigens and T-cells that recognize them is essential for T-cell-based immunotherapy. However, neoantigen-reactive Tumor-infiltrating lymphocytes (TILs) are highly differentiated or exhausted with a limited proliferative capacity; it is challenging to expand them for a sufficient number to probe their specificity. Therefore, we developed a novel cloning and expression system to examine TCRs discovered by single-cell sequencing of TILs for their neoantigen-specificity.

Methods

TILs of lung cancer and sarcoma were analyzed. Surgically removed tumors were divided into several pieces. They were enzymatically digested to prepare fresh tumor digest (FTD) and cryopreserved. They were used to generate TIL cultures and perform WES and RNA-Seq to identify tumor-specific mutations. MHCflurry was used to predict the binding affinity of potential epitopes arising from these mutations to HLA class I. Peptides that were predicted to bind to patients‘ own MHC class I molecules strongly were then synthesized. Single TILs isolated with the ICELL8® cx system (Takara Bio) were dispensed into a nanowell TCR chip containing preprinted barcodes. Barcoded cDNAs were PCR-amplified in-chip, pooled off-chip, and used as a template in the TCR-specific PCR or for the whole transcriptome library generation of 5’ ends of all transcripts. Based on single-cell transcriptome data and TCR profiles of TILs, we predict and prioritize neoantigen-specific TCRs and cloned them into siTCR® retrovirus vectors. These TCRs were transduced into SUP-T1-based reporter cells in which ZsGreen fluorescent protein expression is controlled by AP-1 and NFAT binding sites. TCR-expressing reporter cells were cocultured with patient autologous APCs pulsed with a pool of candidate neoantigen peptides. ZsGreen expression indicates that TCRs match their cognate neoantigens.

Results

In a lung cancer patient, we set up 18 TIL cultures and obtained 12 TILs. TILs were cocultured with FTD; IFN-γ production was measured by ELISA to evaluate their reactivity to the autologous tumor. NGS identified 197 somatic mutations, 4 fusion genes, and 8 highly expressed cancer-testis antigens. Among them, 339 candidate peptides were synthesized and screened. In addition, we cloned 3 pairs of TCRαβ chains from most expanded TIL cultures and 4 TCRs from ex vivo TILs with exhausted phenotype. Two reporter cells that express TCRs from exhausted TILs responded to the same neoantigen peptide.

Conclusions

Generating TCR expressing cell lines facilitated the identifying neoantigens and their cognate TCR sequences from patients.

Ethics Approval

G3545

Integrative immunogenomic analysis of gastric cancer dictates novel immunological classification and the functional status of tumor-infiltrating cells

Objectives

A better understanding of antitumor immunity will help predict the prognosis of gastric cancer patients and tailor the appropriate therapies in each patient. Therefore, we propose a novel immunological classification of gastric cancer.

Methods

We performed whole‐exome sequencing (WES), RNA‐Seq and flow cytometry in 29 gastric cancer patients who received surgery. The TCGA data set of 323 gastric cancer patients and RNA‐Seq data of 45 patients who received pembrolizumab (Kim et al. Nat Med 2018; 24: 1449–1458) were also analysed.

Results

Immunogram analysis of cancer–immunity interaction of gastric cancer revealed immune signatures of four main types, designated Hot1, Hot2, Intermediate and Cold. Immunologically hot tumors displayed a dysfunctional T‐cell signature, while cold tumors had an exclusion signature. Ex vivo tumor‐infiltrating lymphocyte analysis documented T‐cell dysfunction with the expression of checkpoint molecules and impaired cytokine production. The T‐cell function was more profoundly damaged in Hot1 than Hot2 tumors. Patients in Hot2 subtypes had better survival in our cohort and TCGA cohort. Although these immunological subtypes overlapped to some degree with the molecular subtypes in the TCGA, intratumoral immune responses cannot be predicted solely based on histological or molecular subtyping of gastric cancer. Molecular and immunological classifications complement each other to predict the responses to anti‐PD‐1 therapy and have the potential to be a biomarker for the treatment of gastric cancer.

Conclusion

The immunological classification of gastric cancer resulted in four subtypes. Hot tumors were further divided into two subtypes, between which the functional status of T cells was different.

Induction of E. coli-derived endonuclease MazF suppresses HIV-1 production and causes apoptosis in latently infected cells

The current antiretroviral therapy cannot cure the patients infected with human immunodeficiency virus type 1 (HIV-1) due to the existence of latently infected cells capable of virus production from harboring proviral DNA. MazF is an ACA nucleotide sequence-specific endoribonuclease derived from Escherichia coli. The conditional expression of MazF by binding of HIV-1 Tat to the promoter region of a MazF-expression vector has previously been shown to selectively inhibit HIV-1 replication in acutely infected cells. The expression of MazF significantly suppressed tumor necrosis factor (TNF)-α-induced HIV-1 production and viral RNA expression in the HIV-1 latently infected cell line OM-10.1 transduced with the MazF-expression vector (OM-10.1/MFR). Moreover, the viability of OM-10.1/MFR cells decreased with increasing concentrations of TNF-α, whereas such decrease was not observed for HL-60 cells transduced with the MazF-expression vector (HL-60/MFR), the uninfected parental cell line of OM-10.1. TNF-α increased the expression of cleaved caspase-3 and cleaved poly (ADP-ribose) polymerase in OM-10.1/MFR cells, indicating that the cell death was caused by the induction of apoptosis. TNF-α-induced expression of MazF mRNA was detected in OM-10.1/MFR but not HL-60/MFR cells, suggesting that TNF-α-induced apoptosis of latently infected cells was due to the expression of MazF. Thus, the anti-HIV-1 gene therapy using the MazF-expression vector may have potential for the cure of HIV-1 infection in combination with suitable latency reversing agents through reducing the size of latently infected cells without viral reactivation.

Development of a Unique T Cell Receptor Gene-Transferred Tax-Redirected T Cell Immunotherapy for Adult T Cell Leukemia

Adult T cell leukemia/lymphoma (ATL) is an aggressive peripheral T cell neoplasm caused by infection with human T cell lymphotropic virus type-1 (HTLV-1). Its prognosis remains extremely poor. Tax, the most important regulatory protein for HTLV-1, is associated with the aggressive proliferation of host cells and is also a major target antigen for CD8⁺ cytotoxic T cells (CTLs). Based on our previous findings that Tax-specific CTLs with a T cell receptor (TCR) containing a unique amino-acid sequence motif exhibit strong HLA-A*24:02-restricted, Tax_301-309-specific activity against HTLV-1, we aimed to develop a Tax-redirected T cell immunotherapy for ATL. TCR-ɑ/β genes were cloned from a previously established CTL clone and transduced into peripheral blood mononuclear cells (PBMCs) of healthy volunteers using a retroviral siTCR vector. Then the cytotoxic efficacy against HTLV-1-infected T cells or primary ATL cells was assessed both in vitro and in vivo. The redirected CTLs (Tax-siCTLs) produced a large amount of cytokines and showed strong killing activity against ATL/HTLV-1-infected T cells in vitro, although they did not have universal activity against ATL cells. Next, in a xenograft mouse model using an HTLV-1-infected T cell line (MT-2), in all mice treated with Tax-siCTLs, the tumor rapidly diminished and finally disappeared without normal tissue damage, although all mice that were untreated or treated with non-gene-modified PBMCs died because of tumor progression. Our findings confirm that Tax-siCTLs can exert strong anti-ATL/HTLV-1 effects without a significant reaction against normal cells and have the potential to be a novel immunotherapy for ATL patients.

Tumor responses and early onset cytokine release syndrome in synovial sarcoma patients treated with a novel affinity-enhanced NY-ESO-1-targeting TCR-redirected T cell transfer

2530

Background: Adoptive transfer of TCR-redirected T cells has been reported to exhibit efficacy in some of melanoma and sarcoma patients. However, there have not been well known about cytokine release syndrome (CRS) or its relations to tumor responses. This study evaluates clinical responses in association with the cell kinetics and CRSs after transfer of high-affinity NY-ESO-1 TCR-gene transduced T cells in NY-ESO-1-expressiong cancer patients (NCT02366546). Methods: We developed a novel-type affinity-enhanced NY-ESO-1-specific TCR and an originally-developed retrovirus vector that encodes siRNA to silence endogenous TCR creation. The NY-ESO-1/TCR sequence is mutated for high affinity with replacements of G50A and A51E in CDR2 region. This is a first-in-man clinical trial of the novel NY-ESO-1-specfic TCR-T cell transfer to evaluate the safety, in vivo cell kinetics and clinical responses. It was designed as a cell-dose escalation from 5 x108 to 5 x109 cells. NY-ESO-1-expressing refractory cancer patients were enrolled, with 3+3 cohort design. Cyclophosphamide (1,500mg/m2) were administered prior to the TCR-T cell transfer as pre-conditioning. Results: 9 patients were treated with the NY-ESO-1/TCR-T cell transfer. The TCR-T cells expanded in peripheral blood with a dose-dependent manner, associated with rapid proliferation within 5 days after the cell transfer. 3 patients receiving 5x109 cells developed early-onset CRSs, with elevations of serum IL-6, IFN-γ. The CRSs developed on day1 or 2 after the cell transfer. They were well managed with tocilizumab treatment. 3 synovial sarcoma patients exhibited tumor shrinkages of partial responses, and they all had high-expression of NY-ESO-1 in the tumor samples, namely, 75% or more. Exploratory analysis revealed that multiple chemotactic cytokines including CCL2 and CCL7, and IL-3 increased in the serum from the patients with CRS. The proportions of effector-memory phenotype T cells in the infused cell-product were significantly associated with CRS development. Conclusions: The affinity-enhanced NY-ESO-1/TCR-T cell transfer exhibited early-onset CRS in association with in vivo cell proliferation and sequential tumor responses in the patients with high-NY-ESO-1-expressing synovial sarcoma. Clinical trial information: NCT02366546.

Highly efficient genome editing for single-base substitutions using optimized ssODNs with Cas9-RNPs

Target-specific genome editing using engineered nucleases has become widespread in various fields. Long gene knock-in and single-base substitutions can be performed by homologous recombination (HR), but the efficiency is usually very low. To improve the efficiency of knock-in with single-stranded oligo DNA nucleotides (ssODNs), we have investigated optimal design of ssODNs in terms of the blocking mutation, orientation, size, and length of homology arms to explore the optimal parameters of ssODN design using reporter systems for the detection of single-base substitutions. We have also investigated the difference in knock-in efficiency among the delivery forms and methods of Cas9 and sgRNA. The knock-in efficiencies for optimized ssODNs were much higher than those for ssODNs with no blocking mutation. We have also demonstrated that Cas9 protein/sgRNA ribonucleoprotein complexes (Cas9-RNPs) can dramatically reduce the re-cutting of the edited sites.

Functional Analysis of an Inducible Promoter Driven by Activation Signals from a Chimeric Antigen Receptor

Adoptive transfer of T cells expressing a chimeric antigen receptor (CAR) is a promising cell-based anticancer therapy. Although clinical studies of this approach show therapeutic efficacy, additional genetic modification is necessary to enhance the efficacy and safety of CAR-T cells. For example, production of an antitumor cytokine from CAR-T cells can potentially enhance their tumor-killing activity, but there are concerns that constitutive expression of anticancer molecules will cause systemic side effects. Therefore, it is important that exogenous gene expression is confined to the tumor locality. Here, we aimed to develop an inducible promoter driven by activation signals from a CAR. Transgene expression in T cells transduced with the CD19-targeted CAR and an inducible promoter, including inducible reporter genes (CAR-T/iReporter), was only induced strongly by co-culture with CD19-positive target cells. CAR-T/iReporter cells also showed redirected cytolysis toward CD19-positive, but not CD19-negative, tumor cells. Overall, our study indicated that the inducible promoter was selectively driven by activation signals from the CAR, and transduction with the inducible promoter did not affect original effector activities including interleukin-2 and interferon-γ production and the antitumor activity of CAR-redirected cytotoxic T lymphocytes. Moreover, this inducible promoter permits visualization and quantification of the activation status in CAR-T cells.

Highly Efficient Ultracentrifugation-free Chromatographic Purification of Recombinant AAV Serotype 9

Recombinant adeno-associated virus serotype 9 (rAAV9) can specifically transduce muscle and neuronal tissues; thus, rAAV9 can potentially be used in gene therapy. However, rAAV9 is the most challenging rAAV serotype to purify. Traditionally, rAAV9 has been purified by ultracentrifugation, which is not scalable. We recently described a chromatographic purification protocol for rAAV1; this protocol can achieve scalable purifications. In this study, we attempted to optimize this protocol for purifying rAAV9 preparations, and we developed a novel, effective method for high-yield purification of rAAV9 using quaternary ammonium anion exchangers and size-exclusion chromatography. The final purified rAAV9 contained mainly three capsid proteins, as observed by SDS-PAGE. Furthermore, negative-stain electron microscopy demonstrated that 96.1% ± 1.1% of rAAV9 particles carried the viral genome containing the EGFP transgene, indicating that impurities and empty capsids can be eliminated with our purification protocol. The final rAAV9 titer obtained by our protocol totaled 2.5 ± 0.4 × 10¹⁵ viral genomes produced from ∼3.2 × 10⁹ HEK293EB cells. We confirmed that our protocol can also be applied to purify other varied AAV genome constructs. Our protocol can scale up production of pure rAAV9, in compliance with current good manufacturing practice, for clinical applications in human gene therapy.

Abstract CT147: Safety and efficacy of high purity and activity NK cells therapy in combination with IgG1 antibody in patients with gastric or colorectal cancer: A phase I clinical trial

Background; Natural killer (NK) cells exhibit strong cytotoxic activity against tumor cells, and produce numerous cytokines resulting in the activation of the adoptive immune systems. Thus, NK cell is considered ideal cell for adoptive cancer immunotherapy. But the difficulty of obtaining large numbers of NK cells that are safe to administer deters its clinical use. We successfully generated large numbers of activated NK cells from small quantities of blood and also determined that the expanded cells were safe to administer in a monotherapy (J Transl Med (2015) 13:277). Since NK cells play a key role in antibody-dependent cellular cytotoxicity (ADCC), administration of NK cells would be expected to enhance the efficacy of IgG1 monoclonal antibodies by augmenting ADCC. This phase I clinical trial evaluated the safety, toxicity, and immunological response of the adoptive NK therapy in combination with IgG1 antibodies.

Patients and Methods; Patients with unresectable advanced gastric or colorectal cancer who have administered or have planned to administer IgG1 antibody (i.e. trastuzumab for HER2 positive gastric cancer or cetuximab for RAS-wild colorectal cancer). NK cells were expanded from PBMCs with the same method in previous clinical trial, briefly ex vivo by stimulating PBMCs with OK432, IL-2, and modified FN-CH296-induced T cells. Expanded NK cells were intravenously injected 3 days after IgG1 antibody administration in a dose-escalating manner (dose 0.5 × 109, 1.0 × 109, 2.0 × 109 cells/injection, three patients/one cohort), every 3 weeks for 3 cycles. We evaluated the safety and efficacy of the combination therapy. To assess the immunological response, immunomonitoring was performed.

Results; Nine eligible patients were enrolled. NK cell populations expanded with our system were confirmed as being enriched in NK cells (median 92.9%) with high expression of NKG2D(97.6%) and CD16(69.6%). This combination therapy was well tolerated with no severe adverse events. Among six evaluable patients, 4 presented SD, 2 presented PD. Of the four SD patients, 3 showed an overall decrease in tumor size after combination therapy. In immunomonitoring analysis, whole blood IFN-gamma production level was increased and the proportion of Treg (Treg/CD4) in peripheral blood was decreased after the combination therapy.

Conclusions; This is the first clinical trial of the combination of adoptive NK cell therapy and IgG1 monoclonal antibodies. Our data provide evidence of good tolerability and preliminary anti-tumor activity for this combination therapy. Moreover, immunological monitoring revealed that the combination therapy induced Th1-type immune response and reduced peripheral Tregs. However, given the limited activity observed in this clinical trial, additional studies are necessary to develop these combination approaches.

Citation Format: Takeshi Ishikawa, Tetsuya Okayama, Naoyuki Sakamoto, Mitsuko Ideno, Kaname Oka, Tatsuji Enoki, Junichi Mineno, Hideyuki Konishi, Satoshi Kokura, Yuji Naito, Yoshito Itoh. Safety and efficacy of high purity and activity NK cells therapy in combination with IgG1 antibody in patients with gastric or colorectal cancer: A phase I clinical trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT147.

Phase I clinical trial of adoptive transfer of expanded natural killer cells in combination with IgG1 antibody in patients with gastric or colorectal cancer

Natural killer (NK) cells exhibit strong cytotoxic activity against tumor cells without prior sensitization, and have the potential to exert antibody-dependent cellular cytotoxicity (ADCC). In this clinical trial, we examined the safety and efficacy of the use of NK cells, generated using a novel expansion system, in combination with IgG1 antibodies for the treatment of advanced gastric or colorectal cancers. Treatment consisted of trastuzumab- or cetuximab-based chemotherapy, plus adoptive NK cell therapy. For administration of expanded NK cells, dose escalation with a sequential 3 + 3 design was performed in three steps, at doses of 0.5 × 109 , 1.0 × 109 , and 2.0 × 109 cells/injection (N = 9). After 3 days of IgG1 antibody administration, patients were infused with expanded NK cells three times at triweekly intervals. NK cell populations expanded with our system were confirmed as being enriched in NK cells (median 92.9%) with high expression of NKG2D (97.6%) and CD16 (69.6%). The combination therapy was very well tolerated with no severe adverse events. Among six evaluable patients, four presented stable disease (SD) and two presented progressive disease. Of the four SD patients, three showed an overall decrease in tumor size after combination therapy. Immune monitoring suggested that combination therapy enhanced whole blood IFN-γ production and reduced peripheral regulatory T cells (Tregs). In conclusion, this phase I trial provides evidence of good tolerability, induction of Th1 immune responses, and preliminary anti-tumor activity for this combination therapy, in patients with advanced gastric and colorectal cancer that have received previous therapy.

Phase I clinical trial of adoptive transfer of expanded natural killer cells in combination with IgG1 antibody in patients with gastric or colorectal cancer

Natural killer (NK) cells exhibit strong cytotoxic activity against tumor cells without prior sensitization, and have the potential to exert antibody-dependent cellular cytotoxicity (ADCC). In this clinical trial, we examined the safety and efficacy of the use of NK cells, generated using a novel expansion system, in combination with IgG1 antibodies for the treatment of advanced gastric or colorectal cancers. Treatment consisted of trastuzumab- or cetuximab-based chemotherapy, plus adoptive NK cell therapy. For administration of expanded NK cells, dose escalation with a sequential 3 + 3 design was performed in three steps, at doses of 0.5 × 109 , 1.0 × 109 , and 2.0 × 109 cells/injection (N = 9). After 3 days of IgG1 antibody administration, patients were infused with expanded NK cells three times at triweekly intervals. NK cell populations expanded with our system were confirmed as being enriched in NK cells (median 92.9%) with high expression of NKG2D (97.6%) and CD16 (69.6%). The combination therapy was very well tolerated with no severe adverse events. Among six evaluable patients, four presented stable disease (SD) and two presented progressive disease. Of the four SD patients, three showed an overall decrease in tumor size after combination therapy. Immune monitoring suggested that combination therapy enhanced whole blood IFN-γ production and reduced peripheral regulatory T cells (Tregs). In conclusion, this phase I trial provides evidence of good tolerability, induction of Th1 immune responses, and preliminary anti-tumor activity for this combination therapy, in patients with advanced gastric and colorectal cancer that have received previous therapy.

Phase I clinical trial of adoptive transfer of expanded natural killer cells in combination with IgG1 antibody in patients with gastric or colorectal cancer

Natural killer (NK) cells exhibit strong cytotoxic activity against tumor cells without prior sensitization, and have the potential to exert antibody-dependent cellular cytotoxicity (ADCC). In this clinical trial, we examined the safety and efficacy of the use of NK cells, generated using a novel expansion system, in combination with IgG1 antibodies for the treatment of advanced gastric or colorectal cancers. Treatment consisted of trastuzumab- or cetuximab-based chemotherapy, plus adoptive NK cell therapy. For administration of expanded NK cells, dose escalation with a sequential 3 + 3 design was performed in three steps, at doses of 0.5 × 109 , 1.0 × 109 , and 2.0 × 109 cells/injection (N = 9). After 3 days of IgG1 antibody administration, patients were infused with expanded NK cells three times at triweekly intervals. NK cell populations expanded with our system were confirmed as being enriched in NK cells (median 92.9%) with high expression of NKG2D (97.6%) and CD16 (69.6%). The combination therapy was very well tolerated with no severe adverse events. Among six evaluable patients, four presented stable disease (SD) and two presented progressive disease. Of the four SD patients, three showed an overall decrease in tumor size after combination therapy. Immune monitoring suggested that combination therapy enhanced whole blood IFN-γ production and reduced peripheral regulatory T cells (Tregs). In conclusion, this phase I trial provides evidence of good tolerability, induction of Th1 immune responses, and preliminary anti-tumor activity for this combination therapy, in patients with advanced gastric and colorectal cancer that have received previous therapy.

Phase I clinical trial of adoptive transfer of expanded natural killer cells in combination with IgG1 antibody in patients with gastric or colorectal cancer

Natural killer (NK) cells exhibit strong cytotoxic activity against tumor cells without prior sensitization, and have the potential to exert antibody-dependent cellular cytotoxicity (ADCC). In this clinical trial, we examined the safety and efficacy of the use of NK cells, generated using a novel expansion system, in combination with IgG1 antibodies for the treatment of advanced gastric or colorectal cancers. Treatment consisted of trastuzumab- or cetuximab-based chemotherapy, plus adoptive NK cell therapy. For administration of expanded NK cells, dose escalation with a sequential 3 + 3 design was performed in three steps, at doses of 0.5 × 109 , 1.0 × 109 , and 2.0 × 109 cells/injection (N = 9). After 3 days of IgG1 antibody administration, patients were infused with expanded NK cells three times at triweekly intervals. NK cell populations expanded with our system were confirmed as being enriched in NK cells (median 92.9%) with high expression of NKG2D (97.6%) and CD16 (69.6%). The combination therapy was very well tolerated with no severe adverse events. Among six evaluable patients, four presented stable disease (SD) and two presented progressive disease. Of the four SD patients, three showed an overall decrease in tumor size after combination therapy. Immune monitoring suggested that combination therapy enhanced whole blood IFN-γ production and reduced peripheral regulatory T cells (Tregs). In conclusion, this phase I trial provides evidence of good tolerability, induction of Th1 immune responses, and preliminary anti-tumor activity for this combination therapy, in patients with advanced gastric and colorectal cancer that have received previous therapy.

Phase I clinical trial of adoptive transfer of expanded natural killer cells in combination with IgG1 antibody in patients with gastric or colorectal cancer

Natural killer (NK) cells exhibit strong cytotoxic activity against tumor cells without prior sensitization, and have the potential to exert antibody-dependent cellular cytotoxicity (ADCC). In this clinical trial, we examined the safety and efficacy of the use of NK cells, generated using a novel expansion system, in combination with IgG1 antibodies for the treatment of advanced gastric or colorectal cancers. Treatment consisted of trastuzumab- or cetuximab-based chemotherapy, plus adoptive NK cell therapy. For administration of expanded NK cells, dose escalation with a sequential 3 + 3 design was performed in three steps, at doses of 0.5 × 109 , 1.0 × 109 , and 2.0 × 109 cells/injection (N = 9). After 3 days of IgG1 antibody administration, patients were infused with expanded NK cells three times at triweekly intervals. NK cell populations expanded with our system were confirmed as being enriched in NK cells (median 92.9%) with high expression of NKG2D (97.6%) and CD16 (69.6%). The combination therapy was very well tolerated with no severe adverse events. Among six evaluable patients, four presented stable disease (SD) and two presented progressive disease. Of the four SD patients, three showed an overall decrease in tumor size after combination therapy. Immune monitoring suggested that combination therapy enhanced whole blood IFN-γ production and reduced peripheral regulatory T cells (Tregs). In conclusion, this phase I trial provides evidence of good tolerability, induction of Th1 immune responses, and preliminary anti-tumor activity for this combination therapy, in patients with advanced gastric and colorectal cancer that have received previous therapy.

Phase I clinical trial of adoptive transfer of expanded natural killer cells in combination with IgG1 antibody in patients with gastric or colorectal cancer

Natural killer (NK) cells exhibit strong cytotoxic activity against tumor cells without prior sensitization, and have the potential to exert antibody-dependent cellular cytotoxicity (ADCC). In this clinical trial, we examined the safety and efficacy of the use of NK cells, generated using a novel expansion system, in combination with IgG1 antibodies for the treatment of advanced gastric or colorectal cancers. Treatment consisted of trastuzumab- or cetuximab-based chemotherapy, plus adoptive NK cell therapy. For administration of expanded NK cells, dose escalation with a sequential 3 + 3 design was performed in three steps, at doses of 0.5 × 109 , 1.0 × 109 , and 2.0 × 109 cells/injection (N = 9). After 3 days of IgG1 antibody administration, patients were infused with expanded NK cells three times at triweekly intervals. NK cell populations expanded with our system were confirmed as being enriched in NK cells (median 92.9%) with high expression of NKG2D (97.6%) and CD16 (69.6%). The combination therapy was very well tolerated with no severe adverse events. Among six evaluable patients, four presented stable disease (SD) and two presented progressive disease. Of the four SD patients, three showed an overall decrease in tumor size after combination therapy. Immune monitoring suggested that combination therapy enhanced whole blood IFN-γ production and reduced peripheral regulatory T cells (Tregs). In conclusion, this phase I trial provides evidence of good tolerability, induction of Th1 immune responses, and preliminary anti-tumor activity for this combination therapy, in patients with advanced gastric and colorectal cancer that have received previous therapy.

Phase I clinical trial of adoptive transfer of expanded natural killer cells in combination with IgG1 antibody in patients with gastric or colorectal cancer

Natural killer (NK) cells exhibit strong cytotoxic activity against tumor cells without prior sensitization, and have the potential to exert antibody-dependent cellular cytotoxicity (ADCC). In this clinical trial, we examined the safety and efficacy of the use of NK cells, generated using a novel expansion system, in combination with IgG1 antibodies for the treatment of advanced gastric or colorectal cancers. Treatment consisted of trastuzumab- or cetuximab-based chemotherapy, plus adoptive NK cell therapy. For administration of expanded NK cells, dose escalation with a sequential 3 + 3 design was performed in three steps, at doses of 0.5 × 109 , 1.0 × 109 , and 2.0 × 109 cells/injection (N = 9). After 3 days of IgG1 antibody administration, patients were infused with expanded NK cells three times at triweekly intervals. NK cell populations expanded with our system were confirmed as being enriched in NK cells (median 92.9%) with high expression of NKG2D (97.6%) and CD16 (69.6%). The combination therapy was very well tolerated with no severe adverse events. Among six evaluable patients, four presented stable disease (SD) and two presented progressive disease. Of the four SD patients, three showed an overall decrease in tumor size after combination therapy. Immune monitoring suggested that combination therapy enhanced whole blood IFN-γ production and reduced peripheral regulatory T cells (Tregs). In conclusion, this phase I trial provides evidence of good tolerability, induction of Th1 immune responses, and preliminary anti-tumor activity for this combination therapy, in patients with advanced gastric and colorectal cancer that have received previous therapy.

Phase I clinical trial of adoptive transfer of expanded natural killer cells in combination with IgG1 antibody in patients with gastric or colorectal cancer

Natural killer (NK) cells exhibit strong cytotoxic activity against tumor cells without prior sensitization, and have the potential to exert antibody-dependent cellular cytotoxicity (ADCC). In this clinical trial, we examined the safety and efficacy of the use of NK cells, generated using a novel expansion system, in combination with IgG1 antibodies for the treatment of advanced gastric or colorectal cancers. Treatment consisted of trastuzumab- or cetuximab-based chemotherapy, plus adoptive NK cell therapy. For administration of expanded NK cells, dose escalation with a sequential 3 + 3 design was performed in three steps, at doses of 0.5 × 10⁹ , 1.0 × 10⁹ , and 2.0 × 10⁹ cells/injection (N = 9). After 3 days of IgG1 antibody administration, patients were infused with expanded NK cells three times at triweekly intervals. NK cell populations expanded with our system were confirmed as being enriched in NK cells (median 92.9%) with high expression of NKG2D (97.6%) and CD16 (69.6%). The combination therapy was very well tolerated with no severe adverse events. Among six evaluable patients, four presented stable disease (SD) and two presented progressive disease. Of the four SD patients, three showed an overall decrease in tumor size after combination therapy. Immune monitoring suggested that combination therapy enhanced whole blood IFN-γ production and reduced peripheral regulatory T cells (Tregs). In conclusion, this phase I trial provides evidence of good tolerability, induction of Th1 immune responses, and preliminary anti-tumor activity for this combination therapy, in patients with advanced gastric and colorectal cancer that have received previous therapy.

Efficient tumor regression by adoptively transferred CEA-specific CAR-T cells associated with symptoms of mild cytokine release syndrome

Carcinoembryonic antigen (CEA) is a cell surface antigen highly expressed in various cancer cell types and in healthy tissues. It has the potential to be a target for chimeric antigen receptor (CAR)-modified T-cell therapy; however, the safety of this approach in terms of on-target/off-tumor effects needs to be determined. To address this issue in a clinically relevant model, we used a mouse model in which the T cells expressing CEA-specific CAR were transferred into tumor-bearing CEA-transgenic (Tg) mice that physiologically expressed CEA as a self-antigen. The adoptive transfer in conjunction with lymphodepleting and myeloablative preconditioning mediated significant tumor regression but caused weight loss in CEA-Tg, but not in wild-type mice. The weight loss was not associated with overt inflammation in the CEA-expressing gastrointestinal tract but was associated with malnutrition, reflected in elevated systemic levels of cytokines linked to anorexia, which could be controlled by the administration of an anti-IL-6 receptor monoclonal antibody without compromising efficacy. The apparent relationship between lymphodepleting and myeloablative preconditioning, efficacy, and off-tumor toxicity of CAR-T cells would necessitate the development of CEA-specific CAR-T cells with improved signaling domains that require less stringent preconditioning for their efficacy. Taken together, these results suggest that CEA-specific CAR-based adoptive T-cell therapy may be effective for patients with CEA⁺ solid tumors. Distinguishing the fine line between therapeutic efficacy and off-tumor toxicity would involve further modifications of CAR-T cells and preconditioning regimens.

A Functionally Superior Second-Generation Vector Expressing an Aurora Kinase-A-Specific T-Cell Receptor for Anti-Leukaemia Adoptive Immunotherapy

Aurora Kinase A is a cancer-associated protein normally involved in the regulation of mitosis. Being over-expressed in a range of cancers, it is a suitable target for cell-based immunotherapy. Gene transfer of T-cell receptor sequences cognisant of HLA-A*0201-restricted Aurora Kinase A antigen has previously been shown to transfer specific immunoreactivity against the target peptide in a Human Lymphocyte Antigen-restricted manner. While T cell receptor gene-transfer has great potential in overcoming the difficulties of isolating and expanding tumour-reactive lymphocytes from a patient’s own cells, one hurdle is potential mispairing and competition between exogenous and endogenous T cell receptor chains. We have used a retroviral vector design bearing a short-interfering RNA that downregulates endogenous T cell receptor chains, without affecting expression of the transgenic T cell receptor sequences. The T cell receptor expression cassette also includes a 2A self-cleaving peptide, resulting in equimolar expression of the T cell receptor alpha and beta chains, further enhancing formation of the desired T cell receptor. Via a simple, modular cloning method, we have cloned the alpha and beta chains of the anti-Aurora Kinase A-reactive T cell receptor into this ‘siTCR’ vector. We then compared the activity of this vector against the original, ‘conventional’ vector across a panel of assays. T cell receptors expressed from the siTCR-vector retained the cytotoxic functionality of the original vector, with evidence of reduced off-target reactivity. The rate of expression of correctly-formed T cell receptors was superior using the siTCR design, and this was achieved at lower vector copy numbers. Maintaining T cell receptor efficacy with a reduced vector copy number reduces the risk of genotoxicity. The siTCR design also reduces the risk of mispairing and cross-reactivity, while increasing the functional titre. Such improvements in the safety of T cell receptor gene-transfer will be crucial for clinical applications of this technology.

Development of Engineered T Cells Expressing a Chimeric CD16-CD3ζ Receptor to Improve the Clinical Efficacy of Mogamulizumab Therapy Against Adult T-Cell Leukemia

PURPOSE

Mogamulizumab (Mog), a humanized anti-CC chemokine receptor 4 (CCR4) mAb that mediates antibody-dependent cellular cytotoxicity (ADCC) using FcγR IIIa (CD16)-expressing effector cells, has recently been approved for treatment of CCR4-positive adult T-cell leukemia (ATL) in Japan. However, Mog failure has sometimes been observed in patients who have accompanying chemotherapy-associated lymphocytopenia. In this study, we examined whether adoptive transfer of artificial ADCC effector cells combined with Mog would overcome this drawback.

EXPERIMENTAL DESIGN

We lentivirally gene-modified peripheral blood T cells from healthy volunteers and ATL patients expressing the affinity-increased chimeric CD16-CD3ζ receptor (cCD16ζ-T cells). Subsequently, we examined the ADCC effect mediated by those cCD16ζ-T cells in the presence of Mog against ATL tumor cells both in vitro and in vivo

RESULTS

cCD16ζ-T cells derived from healthy donors killed in vitro Mog-opsonized ATL cell line cells (n = 7) and primary ATL cells (n = 4) depending on both the number of effector cells and the dose of the antibody. cCD16ζ-T cells generated from ATL patients (n = 3) also exerted cytocidal activity in vitro against Mog-opsonized autologous ATL cells. Using both intravenously disseminated model (n = 5) and subcutaneously inoculated model (n = 4), coadministration of Mog and human cCD16ζ-T cells successfully suppressed tumor growth in xenografted immunodeficient mice, and significantly prolonged their survival (P < 0.01 and P = 0.02, respectively).

CONCLUSIONS

These data strongly suggest clinical feasibility of the novel combined adoptive immunotherapy using cCD16ζ-T cells and Mog for treatment of aggressive ATL, particularly in patients who are ineligible for allogeneic hematopoietic stem cell transplantation. Clin Cancer Res; 22(17); 4405-16. ©2016 AACR.

Donor lymphocytes expressing the herpes simplex virus thymidine kinase suicide gene: detailed immunological function following add-back after haplo-identical transplantation

BACKGROUND AIMS

Haplo-identical hematopoietic stem cell transplantation (HSCT) with add-back of donor lymphocytes expressing the herpes simplex virus thymidine kinase suicide gene (TK cells) is one of the most widely applied promising new gene therapy approaches. However, the immunological status of added-back TK cells after HSCT has yet to be well characterized.

METHODS

We investigated TK cells through the use of flow cytometry, T-cell receptor (TCR) Vβ repertoire spectratyping and linear amplification-mediated polymerase chain reaction followed by insertion site analysis in a patient enrolled in our clinical trial.

RESULTS

A comparison of onset with remission of acute graft-versus-host disease confirmed that TK cells were predominantly eliminated and that proliferative CD8(+) non-TK cells were also depleted in response to ganciclovir administration. The TCR Vβ-chain repertoire of both TK cells and non-TK cells markedly changed after administration of ganciclovir, and, whereas the TCR repertoire of non-TK cells returned to a normal spectratype long after transplantation, that of TK cells remained skewed. With the long-term prophylactic administration of acyclovir, TK cells oligoclonally expanded and the frequency of spliced variants of TK cells increased. Known cancer-associated genes were not evident near the oligoclonally expanded herpes simplex virus (HSV)-TK insertion sites.

CONCLUSIONS

We demonstrate obvious differences in immunological status between TK cells and non-TK cells. In addition, we speculate that long-term prophylactic administration of acyclovir increases the risk of oligoclonal expansion of spliced forms of TK cells.

Phase I clinical trial of autologous NK cell therapy using novel expansion method in patients with advanced digestive cancer

Background

NK cells can destroy tumor cells without prior sensitization or immunization. Tumors often lose expression of MHC molecules and/or antigens. However, NK cells can lyse tumor cells in a non-MHC-restricted manner and independent of the expression of tumor-associated antigens. NK cells are therefore considered ideal for adoptive cancer immunotherapy; however the difficulty of obtaining large numbers of fully functional NK cells that are safe to administer deters its clinical use. This phase I clinical trial seeks to address this obstacle by first developing a novel system that expands large numbers of highly activated clinical grade NK cells, and second, determining if these cells are safe in a mono-treatment so they can be combined with other reagents in the next round of clinical trials.

Methods

Patients with unresectable, locally advanced and/or metastatic digestive cancer who did not succeed with standard therapy were enrolled. NK cells were expanded ex vivo by stimulating PBMCs with OK432, IL-2, and modified FN-CH296 induced T cells. Patients were administered autologous natural killer cell three times weekly via intravenous infusions in a dose-escalating manner (dose 0.5 × 10⁹, 1.0 × 10⁹, 2.0 × 10⁹ cells/injection, three patients/one cohort).

Results

Total cell population had a median expansion of 586-fold (range 95–1102), with a significantly pure (90.96 %) NK cell population. Consequently, NK cells were expanded to approximately 4720-fold (range 1372–14,116) with cells being highly lytic in vitro and strongly expressing functional markers such as NKG2D and CD16. This NK cell therapy was very well tolerated with no severe adverse events. Although no clinical responses were observed, cytotoxicity of peripheral blood was elevated approximately twofolds up to 4 weeks post the last transfer.

Conclusion

We successfully generated large numbers of activated NK cells from small quantities of blood without prior purification of the cells. We also determined that the expanded cells were safe to administer in a monotherapy and are suitable for the next round of clinical trials where their efficacy will be tested combined with other reagents.

Trial Registration: UMIN UMIN000007527

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0632-8) contains supplementary material, which is available to authorized users.

Abstract 3137: A novel expansion method for functional natural killer cells and its clinical application

Background: Natural killer (NK) cell-based adoptive immunotherapy is a promising approach for the treatment of cancer. But, it is difficult to generate the sufficient scale and purity of NK cells, and reliable methods to produce large number of functional NK cells have not been established yet. We have developed novel clinical-grade NK cells expansion method to produce the high purity, large scale and functional NK cells using a combination of recombinant human fibronectin fragment (RetroNectin®) -induced T-cells (RN-T cells), OK-432 and IL-2. We subsequently conducted a Phase 1 clinical study to evaluate the safety and efficacy of this NK cell therapy. In this paper, we address the characteristics of the NK cells elicited by this method and the results of immune monitoring in the clinical trial.

Methods: To confirm the significance of RN-T cells as stimulator, we compared the stimulation effects on NK cells between RN-T cells and aCD3-T cells, which stimulated by anti-CD3 mAb only. Next, we analyzed expanded NK cells from PBMCs obtained from 31 cancer patients to verify the efficacy of this method. In the Phase 1 trial, patients with unresectable digestive cancer were enrolled. They received weekly intravenous administration of autologous NK cells elicited by the novel method three times to assess the safety of the number of adoptive cells at 0.5 × 109(cohort1), 1 × 109(cohort 2) and 2 × 109 cells (cohort 3) per dose. The phenotype and cytotoxicity of expanded NK cells were analyzed. For immune monitoring, cytotoxicity of PBMCs and whole blood cytokine levels were examined following NK cell infusion.

Results: The stimulation by RN-T cells could induce preferable NK cell proliferation rather than the one by aCD3-T. As results of 31 cancer patients, 688±76-fold expansion was achieved in this system with PBMCs, and the NK cell populations were highly purified (84.7±3.6%) and highly expressed functional markers such as NKG2D (97.3±0.6%) and CD16 (96.8±0.7%). In the Phase 1 clinical trial, no NK cell infusion related severe or unexpected toxicities were observed. The response rate and the disease control rate in 10 per protocol patients were 0% and 50.0%, respectively. Although no clinical responses were observed, the cytotoxicity of PBMCs against K-562 targets increased in most patients (80%). The average of cytotoxic activity of PBMCs increased more than two times after the NK cell infusion.

Conclusion:

Although no patients receiving the NK cell therapy alone experienced a clinical response, adoptive immunotherapy of the NK cells elicited by the novel method is expected to exert considerable ADCC activity in vivo because of their high expression of CD16. Now, we are conducting clinical trial in which we explore the combination of this novel NK therapy with IgG1 antibodies such as trastuzumab and cetuximab. We also address the ongoing clinical trial in this paper.

Citation Format: Takeshi Ishikawa, Naoyuki Sakamoto, Tetsuya Okayama, Kaname Oka, Satoshi Kokura, Mitsuko Ideno, Akiko Kato, Tatsuji Enoki, Masanari Kitagawa, Junichi Mineno, Tomoyo Yasuda, Toshifumi Doi, Yuji Naito, Yoshito Itoh, Toshikazu Yoshikawa. A novel expansion method for functional natural killer cells and its clinical application. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3137. doi:10.1158/1538-7445.AM2015-3137

Antileukemia multifunctionality of CD4(+) T cells genetically engineered by HLA class I-restricted and WT1-specific T-cell receptor gene transfer

To develop gene-modified T-cell-based antileukemia adoptive immunotherapy, concomitant administration of CD4(+) and CD8(+) T cells that have been gene modified using identical HLA class I-restricted leukemia antigen-specific T-cell receptor (TCR) gene transfer has not yet been fully investigated. Here, using CD4(+) and CD8(+) T cells that had been gene modified with a retroviral vector expressing HLA-A*24:02-restricted and Wilms' tumor 1 (WT1)-specific TCR-α/β genes and siRNAs for endogenous TCRs (WT1-siTCR/CD4(+) T cells and WT1-siTCR/CD8(+) T cells), we examined the utility of this strategy. WT1-siTCR/CD4(+) T cells sufficiently recognized leukemia cells in an HLA class I-restricted manner and provided target-specific Th1 help for WT1-siTCR/CD8(+) T cells. By using a xenografted mouse model, we found that WT1-siTCR/CD4(+) T cells migrated to leukemia sites and subsequently attracted WT1-siTCR/CD8(+) T cells via chemotaxis. Therapy-oriented experiments revealed effective enhancement of leukemia suppression mediated by concomitant administration of WT1-siTCR/CD4(+) T cells and WT1-siTCR/CD8(+) T cells. Importantly, this augmented efficacy in the presence of WT1-siTCR/CD4(+) T cells was correlated with longer survival and enhanced formation of memory T cells by WT1-siTCR/CD8(+) T cells. Collectively, our experimental findings strongly suggest that this strategy would be clinically advantageous for the treatment of human leukemia.

Outcomes in two Japanese adenosine deaminase-deficiency patients treated by stem cell gene therapy with no cytoreductive conditioning

OBJECTIVE

We here describe treatment outcomes in two adenosine deaminase (ADA)-deficiency patients (pt) who received stem cell gene therapy (SCGT) with no cytoreductive conditioning. As this protocol has features distinct from those of other clinical trials, its results provide insights into SCGT for ADA deficiency.

PATIENTS AND METHODS

Pt 1 was treated at age 4.7 years, whereas pt 2, who had previously received T-cell gene therapy, was treated at age 13 years. Bone marrow CD34(+) cells were harvested after enzyme replacement therapy (ERT) was withdrawn; following transduction of ADA cDNA by the γ-retroviral vector GCsapM-ADA, they were administered intravenously. No cytoreductive conditioning, at present considered critical for therapeutic benefit, was given before cell infusion. Hematological/immunological reconstitution kinetics, levels of systemic detoxification, gene-marking levels, and proviral insertion sites in hematopoietic cells were assessed.

RESULTS

Treatment was well tolerated, and no serious adverse events were observed. Engraftment of gene-modified repopulating cells was evidenced by the appearance and maintenance of peripheral lymphocytes expressing functional ADA. Systemic detoxification was moderately achieved, allowing temporary discontinuation of ERT for 6 and 10 years in pt 1 and pt 2, respectively. Recovery of immunity remained partial, with lymphocyte counts in pts 1 and 2, peaked at 408/mm(3) and 1248/mm(3), approximately 2 and 5 years after SCGT. Vector integration site analyses confirmed that hematopoiesis was reconstituted with a limited number of clones, some of which were shown to have myelo-lymphoid potential.

CONCLUSIONS

Outcomes in SCGT for ADA-SCID are described in the context of a unique protocol, which used neither ERT nor cytoreductive conditioning. Although proven safe, immune reconstitution was partial and temporary. Our results reiterate the importance of cytoreductive conditioning to ensure greater benefits from SCGT.

Adoptive Transfer of MAGE-A4 T-cell Receptor Gene-Transduced Lymphocytes in Patients with Recurrent Esophageal Cancer

PURPOSE

Preparative lymphodepletion, the temporal ablation of the immune system, has been reported to promote persistence of transferred cells along with increased rates of tumor regression in patients treated with adoptive T-cell therapy. However, it remains unclear whether lymphodepletion is indispensable for immunotherapy with T-cell receptor (TCR) gene-engineered T cells.

EXPERIMENTAL DESIGN

We conducted a first-in-man clinical trial of TCR gene-transduced T-cell transfer in patients with recurrent MAGE-A4-expressing esophageal cancer. The patients were given sequential MAGE-A4 peptide vaccinations. The regimen included neither lymphocyte-depleting conditioning nor administration of IL2. Ten patients, divided into 3 dose cohorts, received T-cell transfer.

RESULTS

TCR-transduced cells were detected in the peripheral blood for 1 month at levels proportional to the dose administered, and in 5 patients they persisted for more than 5 months. The persisting cells maintained ex vivo antigen-specific tumor reactivity. Despite the long persistence of the transferred T cells, 7 patients exhibited tumor progression within 2 months after the treatment. Three patients who had minimal tumor lesions at baseline survived for more than 27 months.

CONCLUSIONS

These results suggest that TCR-engineered T cells created by relatively short-duration in vitro culture of polyclonal lymphocytes in peripheral blood retained the capacity to survive in a host. The discordance between T-cell survival and tumor regression suggests that multiple mechanisms underlie the benefits of preparative lymphodepletion in adoptive T-cell therapy.

Abstract 2791: Advantages and clinical application of fibronectin CH296-stimulated T cells in cancer immunotherapy

Background: In adoptive T-cell therapy (ACT), the differentiation state of transferred T cells is considered to be crucial to the success of ACT-based approaches. It has been reported that less-differentiated T cells, which have a higher proliferative potential and less prone to apoptosis than more differentiated cells, are ideal for ACT transfer therapy. In this study, we compared the co-stimulation effects of fibronectin CH296 (FN-CH296, RetroNectin®) with that of anti-28Ab or anti-4-1 BB Ab on T-cell expansion and its phenotype. Furthermore, we examined persistence of T cells expanded by these methods in NOG® mice. In addition, we conducted phase 1 clinical study to evaluate the safety and efficacy of FN-CH296 stimulated T cell therapy in patients with advanced cancer.

Methods: PBMCs were activated by various stimulation methods and cultured in gas-permeable culture bag CultiLifeTM 215 and CultiLifeTM Eva for 10-14 days. After that, each expanded cells were analyzed for its phenotypes, in vivo persistence and the ability of accumulation in lymph node. In clinical study, patients underwent FN-CH296 stimulated T cell therapy up to six times every two weeks and safety and antitumor activity of the ACT were assessed. In order to determine immune function, whole blood cytokine levels were analyzed prior to ACT and during the follow up.

Results: Co-stimulation by FN-CH296 with anti-CD3Ab led to higher T-cell expansion and proportion of CCR7+CD45RA+ T cells than that by the others (anti-28Ab/anti-4-1BB Ab). In the experiment for engraftment of expanded T cells in NOG mice, human CD3+ cells were detected in all groups, but the proportion of CCR7+CD45RA+ and CD8+ T cells was significantly higher specifically in the FN-CH296 co-stimulation condition. In addition, higher accumulation of human CD3+ cells in lymph node of NOG® mice was observed when stimulated by the FN-CH296 co-stimulation condition. In phase 1 clinical trial, nine patients were enrolled and infused 1, 3, or 9×109 of T cells to each cohort group (3 patients in each group). As a result, there was no ACT-related serious adverse event in all doses and one patient achieved CR, one achieved PR, four had SD, and three had PD. The number of less-differentiated cells that was infused showed a strong positive correlation with the change in whole blood IFN-γ level after ACT treatment.

Conclusion: These results indicated that FN-CH296 stimulated T cells therapy was very well tolerated with a level of efficacy that is promising and the FN-CH296 stimulation method for ex vivo T-cell expansion is useful as basic technology for adoptive T-cell therapy, as it can be expanded preferentially less-differentiated T cells.

Citation Format: Takeshi Ishikawa, Satoshi Kokura, Tetsuya Okayama, Naoyuki Sakamoto, Mitsuko Ideno, Nobuko Muraki, Akiko Kato, Tatsuji Enoki, Junichi Mineno, Yuji Naito, Yoshito Itoh, Toshikazu Yoshikawa. Advantages and clinical application of fibronectin CH296-stimulated T cells in cancer immunotherapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2791. doi:10.1158/1538-7445.AM2014-2791

Abstract CT214: High purity and activity NK cells therapy in patients with advanced gastrointestinal cancer: Phase I study

PURPOSE:

Our group exploited the novel technique of cultivating high purity and activity NK cells compared with traditional technique from peripheral blood of cancer patients. This phase I study investigated the safety and maximum-tolerated dose of the infusion NK cell number in patients with untreatable advanced gastrointestinal cancer.

PATIENTS AND METHODS:

Patients with gastrointestinal cancer who previously failed standard chemotherapy regimens were treated with three doses of NK cells infusion. We set three dose levels of NK cells infusion. The numbers of infusion NK cells were 5 X 108 cells as cohort 1, 1 X 109 cells as cohort 2, 2 X 109 cells as cohort 3 and each patient was infused NK cells three times per 1 or 2 weeks. The culture method of NK cells described as below; firstly CH296 (FN-CH296, RetroNctin®) induced T cells (RN-T) were prepared in advance by previously reported method, and processed to use as stimulator cells. NK cells were expanded from peripheral blood mononuclear cells by stimulating with modified RN-T, OK-432 and IL-2, then cultured for 21-22 days. We also established large-scale culture system using gas-permeable culture bag for clinical application.

RESULTS:

14 patients were totally enrolled in this study. Of 14 patients, 7 patients were enrolled in cohort 1 study. Of 7 patients, 4 patients couldn't complete NK cells infusion because of some reasons such as bad NK cell proliferation, less purity of active NK cells and worsening of primary cancer. 3 patients could complete in cohort 1. 4 patients were enrolled in cohort 2 study. Of 4 patients, 1 patient couldn't complete the NK cell infusion because of worsening of primary cancer. 3 patients could complete and 1 patient experienced grade 2 pleural effusion accumulation. In cohort 3 study, 3 patients were enrolled. All of 3 patients could complete NK cells infusion, and only 1 patient experienced grade 1 low grade fever. As clinical response, 1 partial response (PR) at cohort 2 and 6 stable diseases (SD) at 4 patients in cohort 1, 1 patient in cohort2 and 1 patient in cohort 3 were observed. In addition, we checked the immune monitoring in detail for all patients.

CONCLUSIONS:

High purity and activity NK cells therapy was safety and maximum-tolerated dose was 2 X 109 cells. The evaluation is needed to further refine the efficacy and the toxicity of the combination therapy, chemotherapy, IgG1 molecular target drugs and this therapy for using this therapy in clinical in the future.

Citation Format: Tetsuya Okayama, Satoshi Kokura, Takeshi ishikawa, Naoyuki Sakamoto, Mitsuko Ideno, Fumiyo Sakai, Akiko Kato, Tatsuji Enoki, Junichi Mineno, Hideyuki Konishi, Yuji Naito, Yoshito Itoh, Toshikazu Yoshikawa. High purity and activity NK cells therapy in patients with advanced gastrointestinal cancer: Phase I study. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr CT214. doi:10.1158/1538-7445.AM2014-CT214

Abstract CT212: Adoptive transfer of wild-type TCR gene transduced T lymphocytes targeting MAGE-A4 antigen to patients with refractory esophageal cancer

Introduction:

Engineering an antigen receptor gene in patients' lymphocytes is one promising strategy to create antigen-specific lymphocytes without senescent phenotypes. The strategy provides an opportunity to extend the application of adoptive T cell therapy for cancer patients. However, this concept has not been tested in epithelial cancer patients.

Material and methods:

MAGE-A4-specific TCR α and β chains were isolated from a human T cell clone that recognizes MAGE-A4 143-151 peptide in an HLA-A*24:02 restricted manner. This T cell clone did not show any cross reactivity to the peptides with a homology to the MAGE-A4 epitope. A retroviral vector that encodes these TCR chains without any artificial modification was constructed; the lymphocytes transduced with the retroviral vector killed the MAGE-A4 expressing tumor in vitro and inhibited the tumor growth in the NOG immmunodeficient mice.

Patients were eligible if they had previously-treated recurrent MAGE-A4-expressing esophageal cancer, and were positive for HLA-A*24;02. Lymphocytes harvested from the patients were infected with the retroviral vector. The TCR-gene transduced T lymphocytes were once transferred to the patients without lymphocyte-depleting treatment, and MAGE-A4 peptide was given 2 and 4 weeks after. The cell doses were divided into 3 cohorts of 2x108 1x109 and 5x109, with a dose-escalating design, by evaluating the safety.

Results:

10 patients received the TCR-gene transduced T lymphocytes. No adverse events related to the cell transfer were observed. The TCR-gene transduced lymphocytes were detected in their peripheral blood in all 10 patients, which showed a dose-dependent appearance during the first 14 days, reaching peak and plateau levels from 3 to 7 days, and declined within 14 days. The cells persisted at 0.5% to 1% level in the peripheral mononuclear cells from day 14 to 63 after the cell transfer. In 6 patients whose blood samples had been collected for over 6 months, 3 patients maintained stable levels as long as 16 months, maintaining the immune reactivity to MAGE-A4-expressing tumor cells. In one patient, whose esophageal tumor was biopsied after the transfer, the TCR-gene transduced cells were detected in the tumor site.

7 patients developed tumor progressions within 2 months after the transfer. Their overall survivals were ranged from 3 to 18+ months, with a median of 10. 3 patients who had minimal tumor lesions at baseline have been free from disease-progression for 12, 15, and 19 months, respectively.

Conclusion:

Wild-type TCR-gene transduced lymphocytes targeting MAGE-A4 antigen were safely given to refractory esophageal cancer patients. The cells persisted in their peripheral blood in a dose-dependent manner in the early phase, and they have been stably persisting over 6 months. Three patients are free from disease progression more than a year. These results encourage us to proceed to further phase trials.

Citation Format: Shinichi Kageyama, Hiroaki Ikeda, Naoko Imai, Mikiya Ishihara, Yoshihiro Miyahara, Shugo Ueda, Takeshi Ishikawa, Hiroaki Naota, Kohshi Ohishi, Taizo Shiraishi, Naoki Inoue, Masashige Tanabe, Tomohide Kidokoro, Hirofumi Yoshioka, Daisuke Tomura, Ikuei Nukaya, Junichi Mineno, Kazutoh Takesako, Naoyuki Katayama, Hiroshi Shiku. Adoptive transfer of wild-type TCR gene transduced T lymphocytes targeting MAGE-A4 antigen to patients with refractory esophageal cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr CT212. doi:10.1158/1538-7445.AM2014-CT212

Systemic CD8+ T cell-mediated tumoricidal effects by intratumoral treatment of oncolytic herpes simplex virus with the agonistic monoclonal antibody for murine glucocorticoid-induced tumor necrosis factor receptor

Oncolytic virotherapy combined with immunomodulators is a novel noninvasive strategy for cancer treatment. In this study, we examined the tumoricidal effects of oncolytic HF10, a naturally occurring mutant of herpes simplex virus type-1, combined with an agonistic DTA-1 monoclonal antibody specific for the glucocorticoid-induced tumor necrosis factor receptor. Two murine tumor models were used to evaluate the therapeutic efficacies of HF10 virotherapy combined with DTA-1. The kinetics and immunological mechanisms of DTA-1 in HF10 infection were examined using flow cytometry and immunohistochemistry. Intratumoral administration of HF10 in combination with DTA-1 at a low dose resulted in a more vigorous attenuation of growth of the untreated contralateral as well as the treated tumors than treatment with either HF10 or DTA-1 alone. An accumulation of CD8⁺ T cells, including tumor- and herpes simplex virus type-1-specific populations, and a decrease in the number of CD4⁺ Foxp3⁺ T regulatory cells were seen in both HF10- and DTA-1-treated tumors. Studies using Fc-digested DTA-1 and Fcγ receptor knockout mice demonstrated the direct participation of DTA-1 in regulatory T cell depletion by antibody-dependent cellular cytotoxicity primarily via macrophages. These results indicated the potential therapeutic efficacy of a glucocorticoid-induced tumor necrosis factor receptor-specific monoclonal antibody in oncolytic virotherapy at local tumor sites.

CD4(+) T Cells Modified by the Endoribonuclease MazF Are Safe and Can Persist in SHIV-infected Rhesus Macaques

MazF, an endoribonuclease encoded by Escherichia coli, specifically cleaves the ACA (adenine–cytosine–adenine) sequence of single-stranded RNAs. Conditional expression of MazF under the control of the HIV-1 LTR promoter rendered CD4⁺ T cells resistant to HIV-1 replication without affecting cell growth. To investigate the safety, persistence and efficacy of MazF-modified CD4⁺ T cells in a nonhuman primate model in vivo, rhesus macaques were infected with a pathogenic simian/human immunodeficiency virus (SHIV) and transplanted with autologous MazF-modified CD4⁺ T cells. MazF-modified CD4⁺ T cells were clearly detected throughout the experimental period of more than 6 months. The CD4⁺ T cell count values increased in all four rhesus macaques. Moreover, the transplantation of the MazF-modified CD4⁺ T cells was not immunogenic, and did not elicit cellular or humoral immune responses. These data suggest that the autologous transplantation of MazF-modified CD4⁺ T cells in the presence of SHIV is effective, safe and not immunogenic, indicating that this is an attractive strategy for HIV-1 gene therapy.

Stimulation through very late antigen-4 and -5 improves the multifunctionality and memory formation of CD8⁺ T cells

T cells express multiple integrin molecules. The significance of signaling through these molecules on acquisition of T-cell effector functions and memory formation capacity remains largely unknown. Moreover, the impact of stimulation through these signals on the generation of T cells for adoptive immunotherapy has not been elucidated. In this study, using a recombinant fragment of fibronectin, CH-296, we demonstrated that stimulation via very late Ag (VLA)-4 and VLA-5 in human and BALB/c mouse CD8(+) T cells, in combination with TCR stimulation, enhances effector multifunctionality and in vivo memory formation. Using TCR-transgenic mouse-derived CD8(+) T cells expressing TCR specific for the syngeneic CMS5 fibrosarcoma-derived tumor Ag, we showed that stimulation by CH-296 improved the ability of tumor-specific CD8(+) T cells to inhibit CMS5 tumor growth when adoptively transferred into hosts with progressing tumors. Improved antitumor effects were associated with decreased infiltration of Foxp3(+) CD4(+) Treg cells in tumors. These results suggest that stimulation via VLA-4 and VLA-5 modulates the qualities of effector T cells and could potentially increase the efficacy of adoptive therapy against cancer.