Primary Human T-cells Research Articles

567. Enhanced Efficiency of CRISPR-Mediated Gene Knock-Out in Primary Human T-Cells

RNA-guided endonuclease (RGEN) technology has great promise for enabling efficient editing of essentially any target genomic locus. Here, we have evaluated application of S. pyogenes Cas9 for gene editing in primary human T-cells using mRNA-mediated delivery of a first generation spCas9 and adeno-associated virus (AAV) to drive guide RNA expression. We find that spCas9-mediated editing using this approach can achieve targeted gene disruption rates at the TCRa locus of up to 30%. Furthermore, evaluation of the dose response of editing efficiency at different Cas9 mRNA doses and over a range of AAV MOI suggests that editing efficiency is limited primarily by AAV-driven guide RNA expression. Evaluation of several approaches to achieve higher editing efficiencies led to the development of a novel method capable of achieving up to 90% TCRa disruption at reduced AAV MOI in selected cell populations. These results suggest that a Cas9-mRNA/AAV-guide approach can be applied to effectively disrupt multiple individual genes in primary human T-cells, and highlight an innovate method through which CRISPR/Cas9 technology may be applied with enhanced efficiency.

The introduction of RNA-DNA differences underlies inter-individual variation in the human IL12RB1 mRNA repertoire (CCR3P.204)

Abstract IL12 and IL23 promote numerous aspects of human immunity, including autoimmunity and mycobacterial disease resistance. IL12RB1 encodes human IL12Rβ1, a surface receptor that signals in complex with IL12Rβ2/IL23R to relay the pro-inflammatory signals of IL12/IL23. Here, we present data demonstrating that in primary human T-lymphocytes, sequence diversity reminiscent of TCRA/TCRB diversity is introduced into IL12RB1 mRNAs via RNA DNA differences (RDDs). RDDs are ribonucleotides present in an mRNA that are not genome encoded; as such they are distinct from genomic single nucleotide polymorphisms. First observed in protozoa, RDD-introduction is now known to be a mechanism employed by many species to suppress protein function. In the case of IL12RB1, we show that in T-cells of healthy individuals the majority of IL12RB1 mRNAs expressed contain RDDs that concentrate in exons encoding IL12Rβ1’s cytokine binding region. IL12RB1 RDDs comprise multiple mutation types, are detectable by both Ion Torrent sequencing and classic Sanger sequencing, and decrease in frequency following T-cell activation. As a result of RDD-introduction, IL12Rβ1 proteins have an altered amino acid sequence that could not be predicted based on genome sequencing alone. While the underlying mechanisms of sequence diversification differ for TCRA/TCRB and IL12RB1, the consequence of this diversification is the same - the expression of proteins of variable amino acid sequence and variable immunological function.

Chemical Composition of Essential Oils from Piper Kadsura

Piper kadsura (Choisy) Ohwi belongs to the Piperaceae family and grows in Fujian and Hainan, with other sporadic distributions in southern China [1]. Its stem, known as a haifengteng, is used in traditional Chinese medicine to treat asthma, anemofrigid-damp arthralgia, and traumatic injury [2]. Piper kadsura shows cytotoxic and anti-neuroinflammatory [3, 4], and anti-inflammatory [5] activitiess it regulates cell proliferation, gene expression, production of cytokines, and cell cycle progression in primary human T-lymphocytes [6]. Phytochemical studies on plants of Piper kadsura have yielded various types of compounds such as lignans, neolignans, amides, terpenes, cyclohexanes, alkaloids, flavonoids, epoxides, sterols, and volatiles [7–14]. We report here the results of our studies on the composition of the essential oil from the dried stem of Piper kadsura. The fresh stems of Piper kadsura (Choisy) Ohwi were collected from Fu Xing Hou Medicinal Materials Company, Gansu Province, China. The plant stem sample was identified by Prof. Qi Huanyang, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences. A voucher specimen is deposited in the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences (No. 02010182). The essential oil was obtained by hydrodistillation using a Clevenger-type apparatus for 5 h, yielding 0.15% (v/w) oil. The essential oil was dried over anhydrous sodium sulfate and studied by GC-MS. The essential oil was subjected to gas chromatographic/mass spectral analysis using an Angilent HP6890 GC with an Agilent 5973I mass selective detector. The analytical conditions included an SE-54 (50 m 0.25 mm 0.50 m) quartz capillary chromatography column, carrier gas: helium with flow rate 1.2 mL/min; volume injected: 0.4 L; split ratio:30:1; initial column temperature 60 C for 2 min, and then programmed to 140 C at a rate of 15 C min–1, finally programmed to 260 C at a rate of 8 C min–1 and held for 10 min; injector temperature 250 C; electron ionization mass spectra were acquired over the mass rage of 40–400 amu; ionization voltage 70 eV; The ion source temperature was at 230 C. The transfer line was at 280 C. Constituents of the oil were identified by comparing the mass spectra of the products with data in the NIST02.L mass-spectra library. The relative percentage amounts of the separated compounds were calculated automatically from peak areas of the total ion chromatograms (TIC). The identified components and their percentages are given in Table 1, where the components are listed in the order of their elution on the column. Forty-three components were detected in the oil, representing 72.01% of the total oil. As can be seen, the major components of the oil are -eudesmol (12.9%) and laevojunenol (9.8%). The contents of espatulenol, -caryophyllene, cis-asarone, and valencene were 6.0%, 6.0%, 5.8%, and 5.4%, respectively.

685. Efficient Targeted Gene Modification in Primary Human Hematopoietic Cells Using Co-Delivery of Nuclease mRNA and AAV Donors

Current clinical HIV treatment strategies applying gene-editing technologies to disrupt the HIV co-receptor CCR5 via nuclease delivery are limited by inefficient bi-allelic disruption and the lack of a combinatorial approach to control HIV infection. The ability to target additional factors conferring HIV resistance to the CCR5 locus with efficient bi-allelic disruption has the potential to translate to improved clinical outcomes. Here we demonstrate a novel method in which RNA-based nuclease expression is paired with AAV-mediated delivery of a homologous gene-targeting donor template to achieve highly efficient targeted recombination in primary human T-cells. This method consistently achieves an average of 60% rates of homology directed recombination into the CCR5 locus in T-cells (>20 experiments with multiple donors); with up to 90% of the gene-modified population exhibiting bi-allelic modification. T-cells modified with this protocol maintain a diverse repertoire and engraft in immune deficient, NOD/SCID/gc-/- (NSG) mice as efficiently as unmodified control T-cells. Using this method, we have integrated chimeric antigen receptors (CARs) into the CCR5 locus; and show that the resulting “targeted CAR” or tCAR T-cells exhibit anti-tumor activities indistinguishable from those generated using lentiviral random integration. Alternatively, we introduced the C46 HIV fusion inhibitor by targeted recombination generating T cell populations with very high-rates of bi-allelic CCR5 disruption paired with protection from HIV with CXCR4 co-receptor tropism. Next, as proof of principle, we utilized the CCR5 site as a ‘safe harbor’ locus for targeted gene addition of the human Wiskott-Aldrich syndrome (WAS) gene. Finally, this novel protocol was also successfully applied to adult human mobilized CD34+ cells, resulting in 10-20% homologous gene targeting, the first such report in adult human CD34+ cells at the CCR5 locus. Our results demonstrate that high-efficiency targeted integration is feasible in primary human cells, and highlight the potential of gene editing technologies to engineer CAR T-cells or other T cell products with myriad novel functional properties.

116. MegaTAL Nucleases Outperform TALENs in Promoting Homology-Directed-Gene Modification in Primary Human T Cells

Advances in rare cleaving nuclease technologies have dramatically increased the potential for seamless manipulation of virtually any gene (i.e. gene editing). Among these platforms, TALENs and Cas9-based nucleases have become broadly applied owing to ease in customizing their DNA recognition properties. In contrast, LAGLIDADG homing endonucleases (LHE) are more challenging to engineer, yet exhibit superior physical attributes, DNA recognition and hydrolysis properties. Recent advances have overcome hurdles in LHE engineering leading to the ability to more rapidly customize LHEs as therapeutic nucleases. In addition, LHEs can be fused to TAL effector arrays to create chimeric proteins [referred to here as megaTALs (MTAL)] that exhibit further enhancements in activity. We previously developed a CCR5-specific MTAL as a potential HIV therapeutic. In parallel, we generated high-activity TALEN pairs targeting the identical region in CCR5. In the current study, we directly compared the ability of these nuclease platforms to induce homology directed repair (HDR) in primary human T-cells. We first verified that both reagents facilitated efficient disruption of the CCR5 locus. We directly compared activity in primary CD4 T cells using mRNA nuclease delivery. Indel frequency was estimated using both the T7 endonuclease assay and a re-cleavage assay (RCA; where genomic DNA surrounding the cleavage site is amplified and digested in vitro with the original LHE used to create the MTAL). NHEJ rates were 65-82% for the TALEN vs. 44-61% (6 experiments) for the MTAL using these respective assays. Next, we coupled mRNA-mediated nuclease expression with AAV delivery of a donor template. We co-delivered mRNA with a range of doses of an AAV-CCR5-GFP donor (containing 1.3kb CCR5 homology arms and an internal MND-GFP expression cassette). Cell viability was not significantly different; and control experiments using AAV BFP (lacking homology arms) demonstrated that infection and expression rates were equivalent. Strikingly, the proportion of cells with sustained GFP expression (at day 16) was up to 5-fold higher in MTAL treated cells (across a range of AAV doses; n=6, independent donors); with the greatest differences observed when access to donor template was limiting. Molecular analysis verified HDR in both test groups. While the mechanism for these differences remains incompletely defined, preliminary comparisons of HR:NHEJ ratios using single cell analysis suggest that alternative DNA repair pathways may be preferentially utilized by the 3’ vs 5’ overhangs generated by LHE vs Fok1 nucleases, respectively. Taken together, our findings suggest that the MTAL platform and the co-delivery method described here may provide significant clinical utility in future editing applications in human hematopoietic cells.

56. AAV Vector-Mediated CRISPR Attacks on Proviral HIV-1 DNA for Purging of Cellular Reservoirs

HIV, the human immunodeficiency virus, is highly successful as a viral pathogen due to its ability to persist in the infected host as an integrated proviral DNA within cellular reservoirs, particularly in resting CD4+ T cells and macrophages. Current antiretroviral combination therapy can control viral spread and viremia but cannot eradicate latent HIV genomes, raising an urgent need for alternative strategies for long-term remission or cure. We combined two powerful technologies, synthetic AAV vectors and CRISPR-mediated gene engineering, with the ultimate aim to eliminate integrated HIV from latently infected human cells. Therefore, we first screened a library of peptide display mutants based on 12 different AAV serotypes and identified novel capsids that mediate potent transduction of relevant HIV target cells, including primary human T-lymphocytes and macrophages. Our lead candidates – two peptide-modified variants of AAV9 or AAVrh.10 – were capable of transducing >65% of primary humanCD4+ T cells and were superior to all 12 wildtype AAV isolates. Concurrently, we created AAV vector genomes that express – alone or in combination – the two essential CRISPR components, i.e., the Cas9 protein and a g(uide)RNA directed against either the HIV-1 long terminal repeats (LTRs), or against viral structural genes. AAV/CRISPR vector efficiency and specificity were validated using a T7 endonuclease assay, showing successful Cas9-mediated induction of double-stranded DNA breaks at the specific HIV-1 target regions and subsequent error-prone repair in HeLaP4 cells with a stably integrated HIV-1 genome. To further potentiate the approach, we exploited a highly customizable self-complementary AAV vector backbone recently developed in our lab that permits multiplexing up to three gRNAs under control of the U6, H1 and 7SK promoters in a single vector particle. We engineered this template to co-express our best gRNAs against the two HIV-1 LTRs and the viral gag gene, and compared its potency with our different first-generation single gRNA vectors. In reporter cells carrying a GFP-encoding HIV-1 genome, simultaneous cleavage was indeed detected at three different sites (5’LTR, 3’LTR and gag), reaching an impressive 63.5% cutting efficiency (versus 36.6-50% for the single gRNA vectors) and demonstrating the power of these vectors to cleave HIV-1 proviral DNA. Finally, we will present results from our ongoing validation of proviral cleavage in human T-cell lines that are latently infected with HIV-1 as a physiologically relevant model of HIV-1 latency. The described experiments prove the possibility to target, cut and destroy integrated HIV-1 proviral DNA with AAV/CRISPR vectors in human cells, and therefore support the further development of our tools and approach into a novel clinical modality for purging of latent HIV-1 reservoirs.

585. Multiplexed Gene Transfer To Human T-Cells By Combining Sleeping Beauty Transposon System With Methotrexate Selection

Engineered human T-cells are a promising therapeutic modality for cancer immunotherapy. T-cells expressing chimeric antigen receptors combined with additional genes to enhance T-cell proliferation, survival, or tumor targeting may further improve efficacy but require multiple stable gene transfer events. Methods are therefore needed to increase production efficiency for multiplexed engineered cells. In this work, we demonstrate multiplexed, non-viral gene transfer to a human T-cell line with efficient selection (≈50%) of cells expressing up to three recombinant open reading frames. The efficient introduction of multiple genes to T-cells was achieved using the Sleeping Beauty transposon system delivered in minicircles by nucleofection. We demonstrate rapid selection for engineered cells using methotrexate (MTX) and a mutant human dihydrofolate reductase resistant to methotrexate-induced metabolic inhibition. Preferential amplification of cells expressing multiple transgenes was achieved by two successive rounds of increasing MTX concentration. We are currently applying this non-viral gene transfer method with MTX selection to engineer primary human T-cells with multiple genetic modifications.

CD47 Enhances In Vivo Functionality of Artificial Antigen-Presenting Cells.

Artificial antigen-presenting cells, aAPC, have successfully been used to stimulate antigen-specific T-cell responses in vitro as well as in vivo. Although aAPC compare favorably with autologous dendritic cells in vitro, their effect in vivo might be diminished through rapid clearance by macrophages. Therefore, to prevent uptake and minimize clearance of aAPC by macrophages, thereby increasing in vivo functionality, we investigated the efficiency of "don't eat me" three-signal aAPC compared with classical two-signal aAPC. To generate "don't eat me" aAPC, CD47 was additionally immobilized onto classical aAPC (aAPC(CD47+)). aAPC and aAPC(CD47+) were analyzed in in vitro human primary T-cell and macrophage cocultures. In vivo efficiency was compared in a NOD/SCID T-cell proliferation and a B16-SIY melanoma model. This study demonstrates that aAPC(CD47+) in coculture with human macrophages show a CD47 concentration-dependent inhibition of phagocytosis, whereas their ability to generate and expand antigen-specific T cells was not affected. Furthermore, aAPC(CD47+)-generated T cells displayed equivalent killing abilities and polyfunctionality when compared with aAPC-generated T cells. In addition, in vivo studies demonstrated an enhanced stimulatory capacity and tumor inhibition of aAPC(CD47+) over normal aAPC in conjunction with diverging biodistribution in different organs. Our data for the first time show that aAPC functionalized with CD47 maintain their stimulatory capacity in vitro and demonstrate enhanced in vivo efficiency. Thus, these next-generation aAPC(CD47+) have a unique potential to enhance the application of the aAPC technology for future immunotherapy approaches.

LymPHOS 2.0: an update of a phosphosite database of primary human T cells.

LymPHOS is a web-oriented database containing peptide and protein sequences and spectrometric information on the phosphoproteome of primary human T-Lymphocytes. Current release 2.0 contains 15 566 phosphorylation sites from 8273 unique phosphopeptides and 4937 proteins, which correspond to a 45-fold increase over the original database description. It now includes quantitative data on phosphorylation changes after time-dependent treatment with activators of the TCR-mediated signal transduction pathway. Sequence data quality has also been improved with the use of multiple search engines for database searching. LymPHOS can be publicly accessed at http://www.lymphos.org.Database URL: http://www.lymphos.org.

Identification of amino acid determinants in CYP4B1 for optimal catalytic processing of 4-ipomeanol.

Mammalian CYP4B1 enzymes are cytochrome P450 mono-oxygenases that are responsible for the bioactivation of several exogenous pro-toxins including 4-ipomeanol (4-IPO). In contrast with the orthologous rabbit enzyme, we show here that native human CYP4B1 with a serine residue at position 427 is unable to bioactivate 4-IPO and does not cause cytotoxicity in HepG2 cells and primary human T-cells that overexpress these enzymes. We also demonstrate that a proline residue in the meander region at position 427 in human CYP4B1 and 422 in rabbit CYP4B1 is important for protein stability and rescues the 4-IPO bioactivation of the human enzyme, but is not essential for the catalytic activity of the rabbit CYP4B1 protein. Systematic substitution of native and p.S427P human CYP4B1 with peptide regions from the highly active rabbit enzyme reveals that 18 amino acids in the wild-type rabbit CYP4B1 protein are key for conferring high 4-IPO metabolizing activity. Introduction of 12 of the 18 amino acids that are also present at corresponding positions in other human CYP4 family members into the p.S427P human CYP4B1 protein results in a mutant human enzyme (P+12) that is as stable and as active as the rabbit wild-type CYP4B1 protein. These 12 mutations cluster in the predicted B-C loop through F-helix regions and reveal new amino acid regions important to P450 enzyme stability. Finally, by minimally re-engineering the human CYP4B1 enzyme for efficient activation of 4-IPO, we have developed a novel human suicide gene system that is a candidate for adoptive cellular therapies in humans.

Allogenic T-Cells Targeting CD123 for Adoptive Immunotherapy of Acute Myeloid Leukemia (AML)

Adoptive immunotherapy using autologous T-cells endowed with chimeric antigen receptors (CARs) has emerged as a promising new approach to treating cancer. However, a limitation of this approach is that CAR T-cells must be generated on a bespoke basis. To overcome this limitation, we have developed an allogeneic based platform for large scale production of “off-the-shelf” CAR T-cells from unrelated 3rd party donors. This platform utilizes Transcription Activator-Like Effector Nuclease (TALENTM) gene editing technology to inactivate the TCRα constant (TRAC) gene, eliminating the potential for T-cells bearing alloreactive TCR’s to mediate Graft versus Host Disease (GvHD). We have previously demonstrated that editing of the TRAC gene can be achieved at high frequencies, obtaining up to 80% of TCRαβ negative cells. This allows us to efficiently produce TCR-deficient T-cells that have been shown to no longer mediate alloreactivity in a xeno-GvHD mouse model. Furthermore, the capacity to perform efficient multiplex genome editing using TALENTM offers the possibility of simultaneously rendering cells resistant to standard chemotherapy or to tumor evasion mechanisms.In this work we present the adaptation of this allogeneic platform to the production of T cells targeting CD123, the transmembrane alpha chain of the interleukin-3 receptor, which is expressed in tumor cells from the majority of patients with Acute Myeloid Leukemia (AML). In a first step, we have screened human primary T-cells harboring CARs with different antigen recognition domains in the context of multiple CAR architectures in order to identify candidates displaying specific activity against cell lines expressing variable levels of the CD123 antigen. To provide proof of concept for the general applicability of the allogeneic approach we have manufactured a TCR-deficient CD123 CAR T-cell (UCART123) and demonstrated that this product maintains a potent anti-tumoral activity in vitro. Experiments in an orthotopic AML mouse model using UCART123 cells are currently ongoing, in order to establish the absence of alloreactivity and the anti-tumoral activity in vivo. The ability to carry out large scale manufacturing of allogeneic, non alloreactive CD123 specific T Cells from a single healthy donor could thus offer the possibility of an off-the-shelf treatment that would be immediately available for administration to a large number of AML patients. DisclosuresGaletto:Cellectis SA: Employment. Lebuhotel:Cellectis SA: Employment. Gouble:Cellectis SA: Employment. Schiffer-Mannioui:Cellectis SA: Employment. Smith:Cellectis SA: Employment.

Targeted cancer immunotherapy via combination of designer bispecific antibody and novel gene-engineered T cells.

BackgroundRedirection of T lymphocytes against tumor antigens can induce dramatic regression of advanced stage malignancy. The use of bispecific antibodies (BsAbs) that bind both the T-cell receptor (TCR) and a target antigen is one promising approach to T-cell redirection. However, BsAbs indiscriminately bind all CD3+ T-cells and trigger TCR activation in the absence of parallel costimulatory signals required to overcome T-cell unresponsiveness or anergy.MethodsTo address these limitations, a combination platform was designed wherein a unique BsAb referred to as frBsAb exclusively engages T-cells engineered to express a novel chimeric receptor comprised of extracellular folate receptor fused to intracellular TCR and CD28 costimulatory signaling domains in tandem; a BsAb-binding immune receptor (BsAb-IR). As a surrogate TCR, the BsAb-IR allows for concomitant TCR and costimulatory signaling exclusively in transduced T-cells upon engagement with specific frBsAbs, and can therefore redirect T-cells on command to desired antigen. Human primary T-cells were transduced with lentiviral vector and expanded for 14–18 days. BsAb-IRs were harvested and armed with frBsAbs to test for redirected cytotoxicity against CD20 positive cancer cell lines.ResultsUsing frBsAbs specific for CD20 or HER2, the lytic activity of primary human T-cells expressing the BsAb-IR was specifically redirected against CD20+ leukemic cells or HER2+ epithelial cancer cells, respectively, while non-engineered T-cells were not activated. Notably, elimination of the CD28 costimulatory domain from the BsAb-IR construct significantly reduced frBsAb-redirected antitumor responses, confirming that frBsAbs are capable of delivering simultaneous TCR activation and costimulatory signals to BsAb-IR T-cells.ConclusionIn summary, our results establish the proof of concept that the combination of BsAbs with optimized gene-engineered T-cells provides the opportunity to specify and augment tumor antigen-specific T-cell activation and may improve upon the early success of conventional BsAbs in cancer immunotherapy.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-014-0347-2) contains supplementary material, which is available to authorized users.

Expression of the IL-7 receptor alpha-chain is down regulated on the surface of CD4 T-cells by the HIV-1 Tat protein.

HIV infection elicits defects in CD4 T-cell homeostasis in both a quantitative and qualitative manner. Interleukin-7 (IL-7) is essential to T-cell homeostasis and several groups have shown reduced levels of the IL-7 receptor alpha-chain (CD127) on both CD4 and CD8 T-cells in viremic HIV+ patients. We have shown previously that soluble HIV Tat protein specifically down regulates cell surface expression of CD127 on human CD8 T-cells in a paracrine fashion. The effects of Tat on CD127 expression in CD4 T-cells has yet to be described. To explore this effect, CD4 T-cells were isolated from healthy individuals and expression levels of CD127 were examined on cells incubated in media alone or treated with Tat protein. We show here that, similar to CD8 T-cells, the HIV-1 Tat protein specifically down regulates CD127 on primary human CD4 T-cells and directs the receptor to the proteasome for degradation. Down regulation of CD127 in response to Tat was seen on both memory and naive CD4 T-cell subsets and was blocked using either heparin or anti-Tat antibodies. Tat did not induce apoptosis in cultured primary CD4 T-cells over 72 hours as determined by Annexin V and PI staining. Pre-incubation of CD4 T-cells with HIV-1 Tat protein did however reduce the ability of IL-7 to up regulate Bcl-2 expression. Similar to exogenous Tat, endogenously expressed HIV Tat protein also suppressed CD127 expression on primary CD4 T-cells. In view of the important role IL-7 plays in lymphocyte proliferation, homeostasis and survival, down regulation of CD127 by Tat likely plays a central role in immune dysregulation and CD4 T-cell decline. Understanding this effect could lead to new approaches to mitigate the CD4 T-cell loss evident in HIV infection.

Abstract 669: Development of MGD007, a gpA33 x CD3 bi-specific DART for T-cell immunotherapy of metastatic colorectal cancer

Abstract Introduction: Encouraging clinical responses have been observed through various strategies designed to harness T-cells for their anti-tumor properties, including immune checkpoint inhibition, chimeric antigen receptor-expressing T-cells or bispecific molecules designed to co-engage T-cells and cancer cells. Furthermore, a positive correlation has been observed in colorectal cancer between the degree and type of T-cell infiltration and prognosis suggesting that T-cell recruitment strategies may be particularly advantageous in this type of cancer. We have developed MGD007, a Dual-Affinity Re-Targeting (DART®) protein designed to redirect T-cells to target gpA33 expressing colon cancer. MGD007 has enhanced pharmacokinetic properties via incorporation of a neonatal FcR-binding Fc domain. The gpA33 target was selected based on its ubiquitous expression in colorectal cancer including reactivity with putative cancer stem cell populations (Li 2013, AACR #3763). To enable preclinical toxicokinetics and dose optimization, MGD007 was designed to cross-react with non-human primates. Methods: MGD007 was stably expressed in CHO cells and purified to homogeneity via a standard antibody-purification platform; in vitro functional studies were performed with a range of colorectal cancer cell lines and primary human T-cells; tumor growth inhibition studies were performed in NOD-SCID mice co-implanted with Colo205 and human T-cells (1:1 E:T ratio) and treated IV with MGD007; pharmacokinetic analyses were performed in cynomolgus monkeys. Results: MGD007 displays the anticipated bispecific binding properties and mediates potent lysis of gpA33-positive - but not gpA33-negative cancer cell lines through recruitment of either human or cynomolgus monkey T-cells. Concomitant with CTL activity, both T-cell activation and expansion are observed in a gpA33-dependent manner. No cytokine activation was observed with human PBMC alone, consistent with the absence of gpA33 expression on peripheral blood cell populations. Both CD8 and CD4 T-cells mediated lysis of gpA33-expressing tumor cells, with activity accompanied by increases in granzyme levels. Xenograft studies showed tumor growth inhibition at doses as low as 4ug/kg. In cynomologus monkeys, 4 weekly doses of 200ug/kg were well tolerated, with prolonged PK consistent with that of an Fc-containing molecule. Conclusions: MGD007 displays potent activity against colorectal cancer cells consistent with a mechanism of action endowed in its design. Furthermore it displays favorable PK in cynomolgus monkeys supporting convenient dosing. Taken together, these data support further investigation of MGD007 as a potential novel therapeutic treatment for colorectal cancer. Citation Format: Paul A. Moore, Ralph Alderson, Kalpana Shah, Yinhua Yang, Steve Burke, Hua Li, Valentine Ciccarone, Ezio Bonvini, Syd Johnson. Development of MGD007, a gpA33 x CD3 bi-specific DART for T-cell immunotherapy of metastatic colorectal 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 669. doi:10.1158/1538-7445.AM2014-669

Detecting multiple cell-secreted cytokines from the same aptamer-functionalized electrode

Inflammatory cytokines are secreted by immune cells in response to infection or injury. Quantification of multiple cytokines in parallel may help with disease diagnosis by illuminating inflammatory pathways related to disease onset and progression. This paper describes development of an electrochemical aptasensor for simultaneous detection of two important inflammatory cytokines, interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α). To enable multiplexing, IFN-γ and TNF-α aptamers were labeled with anthraquinone (AQ) and methylene blue (MB) redox reporters respectively. Random immobilization of two aptamer on gold exhibited redox peaks at −0.37V (AQ) and −0.15V (MB) vs. Ag/AgCl reference. When challenged with either IFN-γ or TNF-α, redox signal of the appropriate reporter changed in concentration dependent manner. To demonstrate one possible application of this sensing approach, electrodes were integrated into microfluidic devices and used to dynamically monitor cytokine release from immune cells. Two cell types, primary human CD4 T-cells and U937 monocytic cells, were used to compare differences in cytokine secretions upon stimulation. These cells were infused into the microfluidic devices and stimulated to commence cytokine production. Release of IFN-γ and TNF-α was monitored concurrently from the same small group of cells over the course of 2h. The strategy of encoding specific aptamer types with unique redox reporters allows sensitive and specific detection of multiple protein biomarkers from the same electrode.

Protein tyrosine kinase 7 promotes PI3K/AKT signaling and survival in primary and neoplastic CD4+ T-lineage cells. (HEM4P.231)

Abstract Protein tyrosine kinase 7 (PTK7), a catalytically inactive receptor tyrosine kinase (RTK) that is highly expressed in intrathymic development, is a novel marker for human CD4+ recent thymic emigrants (RTEs), and is also highly expressed on some T-lineage thymomas, e.g., Jurkat cells. The function of PTK7 in normal human T-cell development and tumors remains unclear. Here, using RNAi-mediated gene silencing in T-lineage tumor cells, primary human peripheral T-cells and thymocytes, we found that targeting PTK7 consistently decreased cell survival by augmenting caspase-3 activation of apoptosis. The PTK7 knockdown also decreased AKT phosphorylation and PI3 kinase activity, suggesting an essential role for PTK7 in survival of RTEs and developing thymocytes involving the PI3K/AKT pathway. Using mass spectrometry of we identified insulin-like growth factor-1 (IGF-1) receptor as an active kinase partner of PTK7. Knockdown of PTK7 reduced IGF-1 receptor function in primary T-lineage cells, confirming the biologic importance of this physical association. This role for PTK7 in promoting cell survival via its effects on cell survival via the PI3K/AKT pathway may not only be relevant to normal T-cell development, including the RTE compartment, but also to the oncogenesis of T-lineage and epithelial cell tumors.

An NCR1-based chimeric receptor endows T-cells with multiple anti-tumor specificities.

The Ral (Ras-like) GTP-binding proteins (RalA and RalB), as effectors of the proto-oncogene Natural killer (NK) cells are an important component of the anti-tumor response. Tumor recognition by NK cells was found to be partly triggered by molecules termed natural cytotoxic receptors (NCRs). Adoptive transfer of genetically-engineered tumor-reactive T-lymphocytes can mediate remarkable tumor regressions mostly in melanoma and leukemia patients. Yet, the application of such treatments to other cancers is needed and dependent on the isolation of receptors that could facilitate efficient recognition of these malignancies. Herein, we aimed at combining NK tumor recognition capability with the genetic modification of T-cells to provide the latter with a means to recognize several tumors in a non-MHC restricted way. Consequently, we generated and evaluated several chimeric receptors based on the extracellular domain of NCR1 (NKp46) fused to multiple signaling moieties and assess their antitumor activity when retrovirally expressed in T-cells. Following co-culture with different tumors, primary human T-lymphocytes expressing a chimeric NCR1 molecule recognized target cells derived from lung, cervical carcinoma, leukemia and pancreatic cancer. In addition, this receptor mediated an upregulation of surface activation markers and significant antitumor cytotoxicity both in vitro and in vivo. These results have meaningful implications for the immunotherapeutic treatment of cancer using gene-modified T-cells.

Cooperation between the human T-cell leukemia virus type-1 p30(II) protein and host cellular factors during oncogenic transformation and retroviral carcinogenesis

The human T-cell leukemia virus type-1 (HTLV-1) pX-encoded accessory factors, p30II and Hbz, suppress proviral gene expression and help to maintain latency as a prerequisite for the development of adult T-cell leukemia/lymphoma (ATLL). Our laboratory is studying how these viral proteins influence host cellular gene expression and signaling which may contribute to hematological disease progression. There are five clinically-defined stages of HTLV-1-associated disease (pre-ATLL, smoldering T-cell leukemia, chronic T-cell leukemia, acute T-cell leukemia, and non-Hodgkin’s T-cell lymphoma) and the transitional molecular events which lead to acute/lymphoma-stage disease are not well understood. We have previously shown that p30II interacts with the c-MYC oncoprotein and enhances c-MYC-dependent transactivation and oncogenic potential by stabilizing recruitment of the TIP60 acetyltransferase to p30II/c-MYC/TIP60 transcription complexes. We now extend these findings by demonstrating that p30II induces acetylation of the c-MYC protein. Acetylation-defective Lys --> Arg substitution mutants of c-MYC (R5, K323R/K417R) are impaired for oncogenic foci-formation by p30II/c-MYC. Acute/lymphoma-stage ATLL clinical isolates frequently exhibit overexpression of c-MYC, due to 8q24 chromosomal translocations and/or c-myc gene amplification, and the HTLV-1-transformed T-cell-lines HuT-102 and MJG11 display significant acetylation of c-MYC. The p53 tumor suppressor is a downstream target of c-MYC and, coincidentally, most ATLL leukemic lymphocytes contain high intracellular levels of wildtype p53. Our recent studies demonstrate that p30II activates p53 and induces the expression of p53-dependent anti-apoptotic genes which could promote oncogene-activation and contribute to ATLL tumorigenesis. These findings as well as a novel role for p30II in the long-term proliferation of lentiviral-p30II-transduced primary human T-lymphocytes will be discussed.

Exosomes derived from HTLV-1 infected cells contain the viral protein Tax

Human T-lymphotropic virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia. The HTLV-1 transactivator protein Tax has been identified as a critical component in the proliferation and transformation of human primary T-cells. This 40 kDa phosphoprotein not only manipulates chromatin remodeling within the host, but also subverts host cell DNA damage response mechanisms, cell cycle progression, and apoptosis. Here we utilized a combination of filtration and ultracentrifugation methods to enrich for exosomes from culture supernatants of HTLV-1 infected cells. We then employed western blots, mass spectrometry, and cytokine arrays to proteomically characterize the host and viral components in these exosomes. Additionally, RT-PCR was used to determine the presence of viral transcripts in these exosomes. Our results demonstrate that exosomes derived from HTLV-1 infected cells contain traditional exosome proteins. Furthermore, our proteomics studies revealed that these exosomes contain viral components such as gp46 and Tax, as well as inflammatory mediators including IL-6 and IL-10. We also investigated the presence of HTLV-1 mRNA transcripts of Env, Tax, HBZ, and 5’LTR contained within exosomes. Moreover, we evaluated the functional impacts of treating naive recipient cells with exosomes secreted from HTLV-1 infected cells, and determined that the exosomes were able to induce a response in reactive oxygen species production. Our observation that the viral protein Tax is contained within exosomes and may be transmitted in an extracellular capacity raises important implications to pathogenesis associated with HTLV-1 infections.

Pre-TCRα supports CD3-dependent reactivation and expansion of TCRα-deficient primary human T-cells

Chimeric antigen receptor technology offers a highly effective means for increasing the anti-tumor effects of autologous adoptive T-cell immunotherapy, and could be made widely available if adapted to the use of allogeneic T-cells. Although gene-editing technology can be used to remove the alloreactive potential of third party T-cells through destruction of either the α or β T-cell receptor (TCR) subunit genes, this approach results in the associated loss of surface expression of the CD3 complex. This is nonetheless problematic as it results in the lack of an important trophic signal normally mediated by the CD3 complex at the cell surface, potentially compromising T-cell survival in vivo, and eliminating the potential to expand TCR-knockout cells using stimulatory anti-CD3 antibodies. Here, we show that pre-TCRα, a TCRα surrogate that pairs with TCRβ chains to signal proper TCRβ folding during T-cell development, can be expressed in TCRα knockout mature T-cells to support CD3 expression at the cell surface. Cells expressing pre-TCR/CD3 complexes can be activated and expanded using standard CD3/CD28 T-cell activation protocols. Thus, heterologous expression of pre-TCRα represents a promising technology for use in the manufacturing of TCR-deficient T-cells for adoptive immunotherapy applications.