Targeting T-cell malignancies using allogeneic double-negative CD4-CAR-T cells

BACKGROUND

Patients with relapsed/refractory T-cell malignancies have limited treatment options. The use of chimeric antigen receptor (CAR)-T cell therapy for T-cell malignancies is challenging due to possible blast contamination of autologous T-cell products and fratricide of CAR-T cells targeting T-lineage antigens. Recently, allogeneic double-negative T cells (DNTs) have been shown to be safe as an off-the-shelf adoptive cell therapy and to be amendable for CAR transduction. Here, we explore the antitumor activity of allogeneic DNTs against T-cell malignancies and the potential of using anti-CD4-CAR (CAR4)-DNTs as adoptive cell therapy for T-cell malignancies.

METHODS

Healthy donor-derived allogeneic DNTs were ex vivo expanded with or without CAR4 transduction. The antitumor activity of DNTs and CAR4-DNTs against T-cell acute lymphoblastic leukemia (T-ALL) and peripheral T-cell lymphoma (PTCL) were examined using flow cytometry-based cytotoxicity assays and xenograft models. Mechanisms of action were investigated using transwell assays and blocking assays.

RESULTS

Allogeneic DNTs induced endogenous antitumor cytotoxicity against T-ALL and PTCL in vitro, but high doses of DNTs were required to attain therapeutic effects in vivo. The potency of DNTs against T-cell malignancies was significantly enhanced by transducing DNTs with a third-generation CAR4. CAR4-DNTs were manufactured without fratricide and showed superior cytotoxicity against CD4+ T-ALL and PTCL in vitro and in vivo relative to empty-vector transduced-DNTs. CAR4-DNTs eliminated T-ALL and PTCL cell lines and primary T-ALL blasts in vitro. CAR4-DNTs effectively infiltrated tumors, delayed tumor progression, and prolonged the survival of T-ALL and PTCL xenografts. Further, pretreatment of CAR4-DNTs with PI3Kδ inhibitor idelalisib promoted memory phenotype of CAR4-DNTs and enhanced their persistence and antileukemic efficacy in vivo. Mechanistically, LFA-1, NKG2D, and perforin/granzyme B degranulation pathways were involved in the DNT-mediated and CAR4-DNT-mediated killing of T-ALL and PTCL.

CONCLUSIONS

These results demonstrate that CAR4-DNTs can effectively target T-ALL and PTCL and support allogeneic CAR4-DNTs as adoptive cell therapy for T-cell malignancies.

Allogeneic double-negative CAR-T cells inhibit tumor growth without off-tumor toxicities

The development of autologous chimeric antigen receptor T (CAR-T) cell therapies has revolutionized cancer treatment. Nevertheless, the delivery of CAR-T cell therapy faces challenges, including high costs, lengthy production times, and manufacturing failures. To overcome this, attempts have been made to develop allogeneic CAR-T cells using donor-derived conventional CD4⁺ or CD8⁺ T cells (T_convs), but severe graft-versus-host disease (GvHD) and host immune rejection have made this challenging. CD3⁺CD4^-CD8^- double-negative T cells (DNTs) are a rare subset of mature T cells shown to fulfill the requirements of an off-the-shelf cellular therapy, including scalability, cryopreservability, donor-independent anticancer function, resistance to rejection, and no observed off-tumor toxicity including GvHD. To overcome the challenges faced with CAR-T_convs, we evaluated the feasibility, safety, and efficacy of using healthy donor-derived allogeneic DNTs as a CAR-T cell therapy platform. We successfully transduced DNTs with a second-generation anti-CD19-CAR (CAR19) without hampering their endogenous characteristics or off-the-shelf properties. CAR19-DNTs induced antigen-specific cytotoxicity against B cell acute lymphoblastic leukemia (B-ALL). In addition, CAR19-DNTs showed effective infiltration and tumor control against lung cancer genetically modified to express CD19 in xenograft models. CAR19-DNT efficacy was comparable with that of CAR19-T_convs. However, unlike CAR19-T_convs, CAR19-DNTs did not cause alloreactivity or xenogeneic GvHD-related mortality in xenograft models. These studies demonstrate the potential of using allogeneic DNTs as a platform for CAR technology to provide a safe, effective, and patient-accessible CAR-T cell treatment option.

Enhancing Therapeutic Efficacy of Double Negative T Cells against Acute Myeloid Leukemia Using Idelalisib

Simple Summary

Persistence of infused cells is an important factor that dictates the outcome of adoptive cellular therapy (ACT). DNT therapy is a novel form of ACT with promising result in treating relapsed or refractory AML in preclinical and early clinical studies. However, in vivo kinetics of human DNTs in cancer-bearing host have not been previously investigated. This study was the first to investigate the persistence of DNTs and ways to improve it in patient-derived xenograft models. DNTs persistence was observed up to 50 days in various organs of leukemia-bearing hosts. However, the detected DNT level was low while significant level of persisting AMLs was observed. To improve the in vivo persistence and therapeutic efficacy of DNTs, we expanded DNTs in the presence of an PI3Kδ inhibitor, idelalisib (Ide). Ide treatment of healthy donor-derived DNTs promoted early memory subsets and improved overall fitness, reducing exhaustion while improving viability. These Ide-induced attributes led to prolonged persistence of DNTs, resulting in superior anti-leukemic activity in vivo. Further, Ide-treated DNTs improved the durability of the treatment response. Collectively, our study highlights the importance of DNT persistence and Ide-mediated improvements in the overall fitness of DNTs, which promote longer persistence in vivo and better treatment outcome.

Abstract

The double negative T cell (DNT) is a unique subset of T cells with potent anti-leukemic potential. Previously, DNT therapy has been shown to effectively target AML cells in patient-derived xenograft (PDX) models. Further, a recently completed phase I/IIa clinical study demonstrated the safety, feasibility, and potential efficacy in AML patients that relapsed after allogeneic hematopoietic stem cell transplantation. However, the persistence and durability of DNT-mediated anti-leukemic response is less well understood. In this study, we characterized the in vivo persistence of DNTs in PDX models. Further, we improved the efficacy and durability of DNT-mediated activity with phosphoinositide 3-kinase delta (PI3Kδ) inhibition. Mechanistically, DNTs treated with the PI3Kδ inhibitor, Idelalisib (Ide), exhibited early memory phenotype with superior viability and proliferative capacity but less cell exhaustion. Collectively, the findings from this study support the use of Ide-treated DNTs to improve its therapeutic outcome.

An autologous tumor vaccine for CLL

Chronic Lymphocytic Leukemia B cells (CLL) are malignant cells which retain at least some functions of normal B cells. Paramount amongst the latter is that when such cells are appropriately stimulated, they are able to present antigens, including any potential tumor antigens, making them excellent choices as a candidate tumor vaccine. We show that following stimulation of CLL cells with Phorbol myristic acetate, IL-2, the TLR7 agonist imiquimod (P2I) and ionomycin (P2Iio), markedly increased expression of CD54 and CD83 was seen, indicative of B cell activation and a transition to antigen-presenting cells. However, this occurred in the context of augmented expression of the known immunoregulatory molecule, CD200. Accordingly we explored the effect of stimulation of CLL cells with P2Iio, followed by coating of cells with a non-depleting anti-CD200mAb, on the ability of those cells to immunize PBL in vitro to become cytotoxic to CLL cells, or to protect NOD-SCIDγc^null (NSG) mice from subsequent CLL tumor challenge. Our data indicate that this protocol is effective in inducing CD8⁺ CTL able to lyse CLL cells in vitro, and decrease tumor burden in vivo in spleen and marrow of mice injected with CLL cells. Pre-treatment of mice with a CD8 depleting antibody before vaccination with P2Iio/anti-CD200 coated cells abolished any protection seen. These data suggest a potential role for blockade of CD200 expression on CLL cells as a component of a tumor vaccination strategy.

Regulation of fetal hemoglobin expression during hematopoietic stem cell development and its importance in bone metabolism and osteoporosis

We have shown that an altered tissue redox environment in mice lacking either murine beta Hemoglobin major (Hgbβ_maKO) or minor (Hgbβ_miKO) regulates inflammation. The REDOX environment in marrow stem cell niches also control differentiation pathways. We investigated osteoclastogenesis (OC)/osteoblastogenesis (OB), in bone cultures derived from untreated or FSLE-treated WT, Hgbβ_maKO or Hgbβ_miKO mice. Marrow mesenchymal cells from 10d pre-cultures were incubated on an osteogenic matrix for 21d prior to analysis of inflammatory cytokine release into culture supernatants, and relative OC:OB using (TRAP:BSP, RANKL:OPG) mRNA expression ratios and TRAP or Von Kossa staining. Cells from WT and Hgbβ_maKO mice show decreased IL-1β,TNFα and IL-6 production and enhanced osteoblastogenesis with altered mRNA expression ratios and increased bone nodules (Von Kossa staining) in vitro after in vivo stimulation of mRNA expression of fetal Hgb genes (Hgbε and Hgbβ_mi) by a fetal liver extract (FSLE). Marrow from Hgbβ_miKO showed enhanced cytokine release and preferential enhanced osteoclastogenesis relative to similar cells from WT or Hgbβ_maKO mice, with no increased osteoblastogenesis after mouse treatment with FSLE. Pre-treatment of WT or Hgbβ_maKO, but not Hgbβ_miKO mice, with other molecules (rapamycin; hydroxyurea) which increase expression of fetal Hgb genes also augmented osteoblastogenesis and decreased cytokine production in cells differentiating in vitro. Infusion of rabbit anti- Hgbε or anti- Hgbβ_mi, but not anti-Hgbα or anti- Hgbβ_ma into WT mice from day 13 gestation for 3 weeks led to attenuated osteoblastogenesis in cultured cells. We conclude that increased fetal hemoglobin expression, or use of agents which improve fetal hemoglobin expression, increases osteoblast bone differentiation in association with decreased inflammatory cytokine release.

Importance of B cells to development of regulatory T cells and prolongation of tissue allograft survival in recipients receiving autologous bone marrow transplantation

We previously showed that congenic bone marrow transplantation (BMTx) post myeloablation augmented tissue allograft survival in association with increased regulatory T (Treg) cells of both host and bone marrow donor origin. Regulatory B (Breg) cells can also modulate T-cell immunity and B cells may be implicated in the development of Treg cells. Accordingly, we explored the effect of B-cell depletion in vivo on augmented graft survival post BMTx. C57BL/6 mice received BALB/c skin allografts followed 7 days later by myeloablation using cyclophosphamide and busulphan. Mice then received T-cell-depleted bone marrow from CD45.1 congenic donors, and ongoing immunosuppression with rapamycin (to day 28 after BMTx). Control mice received cyclophosphamide and busulphan followed by rapamycin, but not congenic bone marrow. At different times post BMTx, mice received B-cell-depleting antibody treatment, and the effect on both skin graft survival, and induction of Treg cells was assessed. BMTx resulted in significantly prolonged skin graft survival versus control mice, in association with attenuated donor-specific alloreactivity relative to controls, increased splenic Treg cells and significantly diminished anti-donor IgG. In mice receiving infusion of B-depleting antibodies for 12 days from day 15 post BMTx, both graft survival and Treg cell activity were diminished, particularly for functional Treg cells of donor origin. Adoptive transfer of Breg cells from mice harvested at 15 days post BMTx prolonged survival in naive transplanted mice and increased Treg cell levels. Thus, autologous BMTx augmentation of graft survival is dependent in part upon a population of Breg cells that can modulate the function of donor-derived Treg cells.

A cross species CD200R1 immune checkpoint agonist with potent anti-inflammatory properties

Functional aptamers displaying agonistic or antagonistic properties are showing great promise in terms of modulating immune responses. Our group has recently developed pegylated DNA aptamers that can either block inflammatory responses (CD200R1agonist) or restore tumor-directed immune responses (PD-1 antagonist) in vivo. Here, we report the derivation and design of a cross species mouse/human CD200R1 DNA aptamer agonist that blocks inflammatory responses in mouse models of skin graft rejection and asthma. This DNA aptamer was discovered by performing NGS and comparing the resulting aptamer motifs derived from independently screening mouse and human CD200R1 as targets. Importantly, this m/hCD200R1 agonistic aptamer does not suppress cytotoxic T-lymphocyte (CTL) induction in 5 day allo-mixed lymphocyte cultures (MLCs) derived from CD200R1 knockout mice, indicating that its mode of action is directly linked to CD200R1 activation. This study suggests that one can derive agonistic DNA aptamers that can be verified as immunomodulators in mouse models with outcomes translatable to the treatment of human conditions.

Importance of CD200 expression by tumor or host cells to regulation of immunotherapy in a mouse breast cancer model

Cell-surface CD200 expression by mouse EMT6 breast tumor cells increased primary tumor growth and metastasis to the draining lymph nodes (DLN) in normal (WT) BALB/c female recipients, while lack of CD200R1 expression in a CD200R1^-/- host negated this effect. Silencing CD200 expression in EMT6^siCD200 tumor cells also reduced their ability to grow and metastasize in WT animals. The cellular mechanisms responsible for these effects have not been studied in detail. We report characterization of tumor infiltrating (TILs) and draining lymph node (DLN) cells in WT and CD200^-/- BALB/c mice, receiving WT tumor cells, or EMT6 lacking CD200 expression (EMT6^siCD200 cells). Our data show an important correlation with augmented CD8⁺ cytotoxic T cells and resistance to tumor growth in mice lacking exposure (on either host cells or tumor) to the immunoregulatory molecule CD200. Confirmation of the importance of such CD8⁺ cells came from monitoring tumor growth and characterization of the TILs and DLN cells in WT mice challenged with EMT6 and EMT6^siCD200 tumors and treated with CD8 and CD4 depleting antibodies. Finally, we have assessed the mechanisms(s) whereby addition of metformin as an augmenting chemotherapeutic agent in CD200^-/- animals given EMT6 tumors and treated with a previously established immunotherapy regime can increase host resistance. Our data support the hypothesis that increased autophagy in the presence of metformin increases CD8⁺ responses and tumor resistance, an effect attenuated by the autophagy inhibitor verteporfin.

Effect of infusion of monoclonal antibodies to tumour necrosis factor-receptor super family 25 on graft rejection in allo-immune mice receiving autologous marrow transplantation

Significant barriers to transplantation exist for individuals who are pre-sensitized to donor antigen and have high titres of donor-reactive antibody. We report the effect of autologous bone marrow transplantation (BMTx) after myeloablation in pre-sensitized mice along with the use of monoclonal antibodies (mAbs) to tumour necrosis factor-receptor super family 25 (TNFRSF25), expressed on regulatory T (Treg) cells. C57BL/6 mice, which had been sensitized earlier with BALB/c skin allografts, received secondary BALB/c grafts after the primary grafts had been rejected. Subsequently, recipient mice underwent myeloablation with cyclophosphamide and busulphan and were injected with T-cell-depleted bone marrow from CD45.1 congenic donors (BMTx). Recipient mice underwent immunosuppressive treatment with rapamycin. A subgroup of mice was also treated with mAbs to TNFRSF25. Control mice were pre-sensitized mice that received cyclophosphamide and busulphan followed by rapamycin. BMTx-treated mice had significantly prolonged skin graft survival versus control mice. These mice also showed attenuated donor-specific mixed lymphocyte co-culture responses relative to controls, increased splenic Treg cells and markedly diminished serum anti-donor IgG. Infusion of anti-TNFRSF25 mAbs further augmented graft survival and increased graft-infiltrating Treg cells. These mAbs also expanded murine and human Treg cells in vitro with the capacity to attenuate mixed lymphocyte co-cultures using fresh peripheral blood mononuclear cells. Overall, this study delineates the roles of autologous BMTx and anti-TNFRSF25 mAbs in expanding Treg cells and attenuating alloimmune responses in pre-sensitized mice.

Immunization of CD200R1KO mice post surgical resection of EMT6 breast cancer leads to long-term (>1year) cure of metastatic tumor growth (TUM2P.1022)

Attenuated expression of CD200 decreases local tumor growth and metastasis in immunocompetent animals. We explored the ability to cure BALB/c CD200KO or CD200R1KO mice of tumors ≤1cm3 in size by surgical resection of localized tumor, followed by immunization with irradiated EMT6 cells using Monophosphoryl Lipid A (MPLA:25υg/mouse) as adjuvant. Controls developed pulmonary and liver metastases within 30 days of surgery. Protection was seen in both CD200KO or CD200R1KO mice, with no macroscopic lung/liver metastases observed in CD200R1KO mice at day 300. After resection and immunization, draining lymph nodes from controls contained tumor cells cloned at limiting dilution in vitro before pulmonary and hepatic metastasis was seen. Within the limits of detection of the assay used (sensitivity ~1 in 107 cells) no tumor cells were detected in CD200R1KO mice, and reductions were seen in CD200KO mice. Infusion of anti-CD8 mAb into surgically treated and immunized CD200R1KO mice attenuated protection from both macroscopic (liver/lung) and microscopic (assayed by limiting dilution of DLN) metastasis. Adoptive transfer of lymphocytes from treated CD200R1KO mice to surgically-treated control mice, particularly after Treg depletion attenuated metastatic growth of tumor, an effect abolished by pretreatment with anti-CD8 mAb. We suggest CD200:CD200R attenuates a potentially tumor-protective CD8 host response to breast cancer following immunotherapy using MPLA as adjuvant.

Comparison of immunity in mice cured of primary/metastatic growth of EMT6 or 4THM breast cancer by chemotherapy or immunotherapy

PURPOSE

We have compared cure from local/metastatic tumor growth in BALB/c mice receiving EMT6 or the poorly immunogenic, highly metastatic 4THM, breast cancer cells following manipulation of immunosuppressive CD200:CD200R interactions or conventional chemotherapy.

METHODS

We reported previously that EMT6 tumors are cured in CD200R1KO mice following surgical resection and immunization with irradiated EMT6 cells and CpG oligodeoxynucleotide (CpG), while wild-type (WT) animals developed pulmonary and liver metastases within 30 days of surgery. We report growth and metastasis of both EMT6 and a highly metastatic 4THM tumor in WT mice receiving iv infusions of Fab anti-CD200R1 along with CpG/tumor cell immunization. Metastasis was followed both macroscopically (lung/liver nodules) and microscopically by cloning tumor cells at limiting dilution in vitro from draining lymph nodes (DLN) harvested at surgery. We compared these results with local/metastatic tumor growth in mice receiving 4 courses of combination treatment with anti-VEGF and paclitaxel.

RESULTS

In WT mice receiving Fab anti-CD200R, no tumor cells are detectable following immunotherapy, and CD4+ cells produced increased TNFα/IL-2/IFNγ on stimulation with EMT6 in vitro. No long-term cure was seen following surgery/immunotherapy of 4THM, with both microscopic (tumors in DLN at limiting dilution) and macroscopic metastases present within 14 d of surgery. Chemotherapy attenuated growth/metastases in 4THM tumor-bearers and produced a decline in lung/liver metastases, with no detectable DLN metastases in EMT6 tumor-bearing mice-these latter mice nevertheless showed no significantly increased cytokine production after restimulation with EMT6 in vitro. EMT6 mice receiving immunotherapy were resistant to subsequent re-challenge with EMT6 tumor cells, but not those receiving curative chemotherapy. Anti-CD4 treatment caused tumor recurrence after immunotherapy, but produced no apparent effect in either EMT6 or 4THM tumor bearers after chemotherapy treatment.

CONCLUSION

Immunotherapy, but not chemotherapy, enhances CD4+ immunity and affords long-term control of breast cancer growth and resistance to new tumor foci.

Bidirectional effect of CD200 on breast cancer development and metastasis, with ultimate outcome determined by tumor aggressiveness and a cancer-induced inflammatory response

CD200 acts through its receptor (CD200R) to inhibit excessive inflammation. The role of CD200-CD200R1 interaction in tumor immunity is poorly understood. In this study, we examined the role of CD200-CD200R1 interaction in the progression and metastasis of highly aggressive 4THM murine-breast carcinoma using CD200 transgenic (CD200(tg)) and CD200R1 knock-out (CD200R1(-)(/-)) BALB/c mice. 4THM cells induce extensive visceral metastasis and neutrophil infiltration in affected tissues. CD200 overexpression in the host was associated with decreased primary tumor growth and metastasis, whereas lack of CD200R1 expression by host cells was associated with enhanced visceral metastasis. Absence of CD200R1 expression led to decreased tumor-infiltrating-cytotoxic T cells and increased the release of inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin (IL)-6. In contrast, CD200 overexpression led to increased tumor-induced interferon-γ and IL-10 response and decreased TNF-α and IL-6 release. Neutrophil infiltration of tissues was markedly decreased in CD200(tg) animals and increased in CD200R1(-/-) mice. These findings are contradictory to what has been reported in the EMT6 mouse breast-cancer model. Other distinguishing features of tumor elicited by EMT6 and 4THM cell injections were also examined. Visceral tissues from mice bearing EMT6 tumors showed a lack of neutrophil infiltration and decreased IL-6 release in CD200R1(-/-) mice. EMT6 and 4THM cells also differed in vimentin expression and in vitro migration rate, which was markedly lower in EMT6 tumors. These results support the hypothesis that CD200 expression can alter immune responses, and can inhibit metastatic growth of tumor cells that induce systemic and local inflammatory response. Increasing CD200 activity/signaling might be an important therapeutic strategy for treatment of aggressive breast carcinomas.

Immunization of CD200R1KO mice post surgical resection of EMT6 breast cancer leads to long-term (>1year) cure of metastatic tumor growth (TUM7P.921)

Attenuated expression of CD200 decreases local tumor growth and metastasis in immunocompetent animals. We explored the ability to cure BALB/c CD200KO or CD200R1KO mice of tumors ≤1cm3 in size by surgical resection of localized tumor, followed by immunization with irradiated EMT6 cells along with CpG as adjuvant. Control animals developed pulmonary and liver metastases within 30 days of surgery. Protection was seen in both CD200KO or CD200R1KO mice, with no macroscopic lung/liver metastases observed in CD200R1KO mice on sacrifice at day 300. After resection and immunization, draining lymph nodes from controls contained tumor cells cloned at limiting dilution in vitro even before pulmonary and hepatic metastasis was seen. Within the limits of detection of the assay used (sensitivity ~1 in 107 cells) no tumor cells were detected at limiting dilution in similarly treated CD200R1KO mice, and significant reductions were seen in CD200KO mice. Infusion of anti-CD4, but less so anti-CD8, mAb into surgically treated and immunized CD200R1KO mice attenuated protection from both macroscopic (liver/lung) and microscopic (assayed by limiting dilution of DLN) metastasis. Adoptive transfer of lymphocytes from treated CD200R1KO mice to surgically-treated control mice also attenuated metastatic growth of tumor, which was abolished by pretreatment of transferred cells with anti-CD4 mAb. Our data suggest CD200:CD200R attenuates a potentially tumor-protective CD4 host response to breast cancer.

Increased lung/liver metastasis of human breast cancer cells in NOD.SCIDIL2rγ-/- mice after treatment with soluble CD200Fc (TUM7P.922)

CD200 overexpression increases metastasis of tumor cells to draining lymph nodes. Increased levels of a soluble form of CD200, sCD200, occur in serum of ~50% breast cancer patients, and an immunoadhesin, linking CD200 to an immunoglobulin Fc region (CD200Fc) increases metastasis in experimental models. We investigated whether CD200 levels were increased in human breast cancer cells in mice, and if overexpression of CD200 increased metastasis. NOD.SCIDIL2rγ-/- mice received 5x105 cells of different human breast cancer cell lines (MCF7; HTB19; MDA-MB-231) injected into the mammary fat pad. Groups of mice received ongoing infusion of human CD200Fc (20μg/mouse at 72hr intervals for 4 weeks). Tumors were resected at ~0.7cm3, and snap frozen for PCR analysis. Mice were monitored post resection, and sacrificed 2-3 months later. Lung and liver metastatic nodules were enumerated, and tissue snap frozen for PCR analysis. All tumors growing in NOD.SCIDIL2rγ-/- mice expressed CD200, though parent (in vitro) cell lines were uniformly negative. CD200Fc increased lung and liver metastasis of all breast cancer lines tested. Tumor metastasis was associated with changes in gene expression in tumor tissue, with significant alterations in genes encoding matrix metalloproteinases, and transcription factors modulating inflammation. Further changes in gene expression were attributed to the effect of CD200Fc infusion. Our data suggests increased soluble CD200 promotes human breast cancer metastasis.

Graft-infiltrating cells expressing a CD200 transgene prolong allogeneic skin graft survival in association with local increases in Foxp3(+)Treg and mast cells

Expression of the molecule CD200 has been reported to increase allograft survival by suppression of inflammation and acquired immunity. In previous studies we have shown that increased skin and cardiac allograft survival in transgenic mice over-expressing CD200 (CD200(tg)) occurs in association with increased intra-graft expression of mRNAs for genes associated with altered T cell subset differentiation. We investigated changes in graft-infiltrating cells, Treg and mast cells in skin grafts post transplantation into control or CD200(tg) mice, using focused gene array and real-time PCR to assess altered gene expression, and FACS, immunohistology and MLC to determine numbers/function of those cells. Graft-infiltrating cells isolated from CD200(tg) recipients suppressed induction of CTL from control lymph node cells in vitro, and contained increased numbers of infiltrating, non-degranulating, mast cells and Foxp3(+)Treg. Mast cells were also evident in graft tissue of control animals, but there these cells showed evidence for degranulation, and fewer Foxp3(+)Treg were present than was the case of CD200(tg) mice. The infusion of a competitive inhibitor of CD200:CD200R interactions, CD200(tr), at high concentrations (50μg/mouse iv) caused rapid rejection of grafts in CD200(tg) mice, mast cell degranulation within graft tissue, and a decrease in Treg infiltrates. These effects were attenuated by simultaneous infusion of the mast cell stabilizer, sodium cromoglycate. We conclude that CD200 expression contributes to graft prolongation through local suppression of mast cell degranulation, attraction/expansion of Treg, and attenuation of T cell effector activation.

CD200+ graft-infiltrating APCs are sufficient for induction of tolerance to skin allografts (169.8)

CD200, a molecule of the immunoglobulin supergene family, increases graft survival and suppresses inflammation/acquired immunity after binding to its receptors (CD200Rs). Skin and cardiac allograft survival is increased in transgenic mice over-expressing CD200 under control of a doxycycline-inducible promoter, (CD200tg), along with increased intra-graft expression of mRNAs for genes which alter T cell subset differentiation. We found a decreased ability of CD11c+ or CD11b+ APCs from CD200tg recipients at days 7/14 to induce CTL from control lymph node cells in vitro, and increased induction of Foxp3+Treg by the same APCs. Focused gene array and real-time PCR measurements confirmed that with increased graft survival in CD200tg mice altered chemokines/cytokines expression occurred, in particular of IL-9, a mast cell growth factor. Mast cells infiltrated grafts of control animals also, but in these mice evidence of degranulation was apparent, and fewer Foxp3+Treg were present than in the case of CD200tg mice, where no degranulation was observed. Infusion of a competitive inhibitor of CD200:CD200R interactions, CD200tr, at high concentrations (50μg/mouse iv) caused rapid rejection of grafts in CD200tg mice, with evidence of mast cell degranulation within graft tissue. We conclude that allergic-type responses can break peripheral tolerance with induction of episodes of acute T-cell-mediated inflammation.

The role of CD200 in immunity to B cell lymphoma

CD200 is a transmembrane protein broadly expressed on a variety of cell types, which delivers immunoregulatory signals through binding to receptors (CD200Rs) expressed on monocytes/myeloid cells and T lymphocytes. Signals delivered through the CD200:CD200R axis have been shown to play an important role in the regulation of anti-tumor immunity, and overexpression of CD200 has been reported in a number of malignancies, including CLL, as well as on cancer stem cells. We investigated the effect of CD200 blockade in vitro on a generation of CTL responses against a poorly immunogenic CD200+ lymphoma cell line and fresh cells obtained from CLL patients using anti-CD200 mAb and CD200-specific siRNAs. Suppression of functional expression of CD200 augmented killing of the CD200+ cells, as well as production of the inflammatory cytokines IFN-gamma and TNF-alpha by effector PBMCs. Killing was mediated by CD8+ cytotoxic T cells, and CD4+ T cells play an important role in CD200-mediated suppression of CTL responses. Our data suggest that CD200 blockade may represent a novel approach to clinical treatment of CLL.

CD200Fc(Gly)6TGFβ suppresses transplant rejection and MLCs in vitro (49.15)

CD200 suppresses graft rejection after engagement of receptors (CD200R), via induction of Treg and production of TGFβ. We asked if a hybrid molecule linking a soluble form of CD200, CD200Fc, to murine TGFβ through a (Gly)6 linker would produce superior suppression to either CD200FC or TGFβ alone, or in combination. MLC cultures used BL/6 responder cells and irradiated BALB/c DCs, in the presence/absence of varying doses of CD200Fc or TGFβ, alone or in combination, or CD200Fc(Gly)6TGFβ. CD200Fc(Gly)6TGFβ produced suppression at 20-100-fold lower concentrations than all other reagents tested alone or together. When used in vivo to suppress rejection of BALB/c skin grafts in C57BL/6 mice, CD200Fc(Gly)6TGFβ also produced immunosuppression at 100-fold lower concentrations. Further studies suggest the mechanism(s) by which this novel molecule produces suppression involves increased numbers of (inducible) Foxp3+ Treg which cause antigen-specific suppression in MLCs in vitro. Using cells with targeted deletion of the main receptor for CD200 (CD200R1), and/or treated with lentiviral particles encoding shRNAs specific for TGFβRII, we showed that suppression depended on responder T cells with a functional TGFβRII, and DCs expressing CD200R1. Augmented inhibition of suppression by CD200Fc(Gly)6TGFβ using anti-CD200R2 in cultures from CD200R1 knockout mice confirmed a role for CD200R2 in suppression. We conclude that CD200Fc(Gly)6TGFβ may have clinical utility in vivo, or ex vivo.

Expression of a CD200 transgene is necessary for induction but not maintenance of tolerance to cardiac and skin allografts

CD200, a type 2 transmembrane molecule of the Ig supergene family, can induce immunosuppression in a number of biological systems, as well as promote increased graft acceptance, following binding to its receptors (CD200Rs). Skin and cardiac allograft acceptance are readily induced in transgenic mice overexpressing CD200 under control of a doxycycline-inducible promoter, both of which are associated with increased intragraft expression of mRNAs for a number of genes associated with altered T cell subset differentiation, including GATA-3, type 2 cytokines (IL-4, IL-13), GITR, and Foxp3. Interestingly, some 12-15 days after grafting, induction of transgenic CD200 expression can be stopped (by doxycycline withdrawal), without obvious significant effect on graft survival. However, neutralization of all CD200 expression (including endogenous CD200 expression) by anti-CD200 mAb caused graft loss, as did introduction of an acute inflammatory stimulus (LPS, 10 microg/mouse, delivered by i.p. injection). We conclude that even with apparently stably accepted tissue allografts, disruption of the immunoregulatory balance by an intense inflammatory stimulus can cause graft loss.

Induction of tolerogenic vs immunogenic dendritic cells (DCs) in the presence of GM-CSF is regulated by the strength of signaling from monophosphoryl lipid A (MPLA) in association with glutathione and fetal hemoglobin gamma-chain

Previous studies showed a fetal sheep liver extract (FSLE), in association with monophosphoryl lipid A, MPLA (a bioactive component of lipid A of LPS), could interact to induce the development of dendritic cells (DCs) which regulated production of Foxp3+ Treg. This interaction was associated with an altered gene expression both of distinct subsets of TLRs and of CD200Rs. Prior studies had suggested that major interacting components within FSLE were gamma-chain of fetal hemoglobin (Hgbgamma) and glutathione (GSH). We investigated whether differentiation/maturation of DCs in vitro in the presence of either GM-CSF or Flt3L to produce preferentially either immunogenic or tolerogenic DCs was itself controlled by an interaction between MPLA, GSH and Hgbgamma. At low (approximately 10 microg/ml) Hgbgamma concentrations, DCs developing in culture with GSH and MPLA produced optimal stimulation of allogeneic CTL cell responses in vitro (and enhanced skin graft rejection in vivo). At higher concentrations (>40 microg/ml Hgbgamma) and equivalent concentrations of MPLA and GSH, the DCs induce populations of Treg which can suppress the induction of allogeneic CTL and graft rejection in vivo. These different populations of DCs express different patterns of mRNAs for the CD200R family. Addition of anti-TLR or anti-MD-1 mAbs to DCs developing in this mixture (Hgbgamma+GSH+MPLA), suggests that one effect of (GSH+Hgbgamma) on MPLA stimulation may involve altered signaling through TLR4.

An alteration in the levels of populations of CD4+ Treg is in part responsible for altered cytokine production by cells of aged mice which follows injection with a fetal liver extract

We have shown previously that a fetal sheep liver extract (FSLE) containing significant quantities of fetal ovine gamma globin chain (Hbgamma) and LPS injected into aged (>20 months) mice could reverse the altered polarization (increased IL-4 and IL-10 with decreased IL-2 and IFNgamma) in cytokine production seen from ConA stimulated lymphoid cells of those mice. The mechanism(s) behind this change in cytokine production were not previously investigated. We report below that aged mice show a >60% decline in numbers and suppressive function of both CD4(+)CD25(+)Foxp3(+) Treg and so-called Tr3 (CD4(+)TGFbeta(+)), and that their number/function is restored to levels seen in control (8-week-old) mice by FSLE. In addition, on a per cell basis, CD4(+)CD25(-)Treg from aged mice were >4-fold more effective in suppression of proliferation and IL-2 production from ConA-activated lymphoid cells of a pool of CD4(+)CD25(-)T cells from 8-week-old mice than similar cells from young animals, and this suppression by CD25(-)T cells was also ameliorated following FSLE treatment. Infusion of anti-TGFbeta and anti-IL-10 antibodies in vivo altered Treg development following FSLE treatment, and attenuated FSLE-induced alterations in cytokine production profiles.

Role of MIF and glutathione, in association with fetal ovine globin chain (Hbγ) and LPS, in induction of TNFα from cells of young and aged mice, and PBL from healthy human populations

Previous reports from our group have established that the fetal ovine gamma globin chain (Hbgamma) and LPS can synergize in the induction of pro-inflammatory cytokines, especially TNFalpha, from mouse and human leukocytes. A fetal sheep liver extract (FSLE) which was observed to have marked immunoregulatory properties in vivo and in vitro had independently been observed to contain significant amounts of each of these molecules. However, the biological activity of this extract (hereafter FSLE) was not explained solely by its content of Hbgamma and LPS, and independent analysis confirmed also the presence of migration inhibitory factor, MIF, and glutathione in FSLE. We have investigated whether MIF and the cellular anti-oxidant glutathione can further synergize with Hbgamma and LPS in TNFalpha induction from human cells in vitro, and mouse cells activated in vivo/in vitro. Our data show that indeed there is evidence for such a synergy. Treatment or mouse cells with FSLE produced an enhanced TNFalpha production which could be inhibited independently both by anti-Hbgamma and by anti-MIF, and optimally by a combination of these reagents.

Analysis of interaction of cloned human and/or sheep fetal hemoglobin γ-chain and LPS in augmenting induction of inflammatory cytokine production in vivo and in vitro

We have reported earlier that purified preparations of sheep fetal hemoglobin, but not adult hemoglobin, in concert with non-stimulatory doses of lipopolysaccharide (LPS) (lipid A), act cooperatively to regulate in vitro production of a number of cytokines, including TNFalpha, TGFbeta and IL-6 from murine and human leukocytes. Following in vivo treatment of mice with the same combination of hemoglobin and LPS, harvested spleen or peritoneal cells showed a similar augmented capacity to release these cytokines into culture supernatants. We report below that genetically cloned gamma-chain of human or sheep fetal hemoglobin, but not cloned alpha- or beta-chains, can produce this cooperative effect, as indeed can HPLC purified, heme-free, gamma-chains derived from cord blood fetal hemoglobin, and that purified haptoglobin completely abolishes the cooperative interaction.

Human intestinal mucin-like protein (MLP) is homologous with rat MLP in the C-terminal region, and is encoded by a gene on chromosome 11 p 15.5

A cDNA specific for a human intestinal mucin (MLP) was amplified by PCR from cDNA of cultured human colonic adenocarcinoma cells, LS174T. The human cDNA shared high sequence homology with a corresponding rat intestinal mucin (MLP) cDNA in the 3' terminal region, and hybridized to the same mRNA (approximately 9.0 Kb) that was recognized by a probe for the MUC-2 human intestinal mucin gene. The gene encoding our human mucin peptide also mapped to chromosome 11 p 15.5, the known locus of MUC-2. Our findings suggest that human MLP and MUC-2 are encoded by the same gene and that rat and human intestinal mucin share a common C-terminal amino acid structure.

Treatment of hypertension in the elderly. III. Response of isolated systolic hypertension to various doses of hydrochlorothiazide: results of a Department of Veterans Affairs cooperative study. Department of Veterans Affairs Cooperative Study Group on Antihypertensive Agents

In a double-blind randomized study, we evaluated the effects of 25 mg vs 50 mg of hydrochlorothiazide in 51 elderly patients (aged 68.9 +/- 7.0 years) with isolated systolic hypertension (blood pressure, 160 to 239 mm Hg systolic and less than 90 mm Hg diastolic). Dose levels could be increased to twice daily to control blood pressure. The reductions in blood pressure (25.4/6.8 mm Hg and 28.9/7.4 mm Hg) and proportion of patients in whom blood pressure was controlled (78% and 89%) were similar in the lower- and higher-dose groups during the titration phase. However, serum potassium level was reduced more in the higher-dosage (0.57 mmol/L) than the lower-dosage (0.17 mmol/L) group. There were no significant changes in blood pressure during a 24-week maintenance phase. No patient required withdrawal from the study because of adverse effects, and cognitive-behavioral function was well preserved. We conclude that hydrochlorothiazide is effective and well tolerated in older patients with isolated systolic hypertension, many of whom may be effectively treated with 25 mg of hydrochlorothiazide once daily.

Mucin depletion in the intestine of malnourished rats

The effects of malnutrition on mucosal goblet cell mucin levels were studied in rats deprived of 50% of their daily intake, as judged by pair-fed, age-matched control animals, for 5 wk. Average daily weight gain was 0.7 g/day compared with 5.8 g in age-matched (AM) rats; final weight was 246 +/- 9 g compared with 406 +/- 4 g. Immunoassayable mucin, sucrase, protein, and DNA were assayed in mucosal scrapings from the proximal, middle, and distal segments of the small intestine in malnourished rats, AM rats, and a third group of low-weight, less mature (LM) rats. Total protein, total DNA, and protein-to-DNA ratios in malnourished rats were unchanged compared with AM control rats and often higher than levels in LM control rats. In malnourished animals, mucin concentration per milligram protein was significantly decreased below AM control animals in the upper two segments and below LM control animals in all segments. Mucin concentration per milligram DNA was significantly lower in malnourished rats than in all segments of both control groups. In contrast, sucrase activity per milligram protein or DNA was either unchanged or increased in the malnourished rats, indicating that the reduction in mucin concentration was selective and did not reflect all surface glycoproteins. Isolated mucins from malnourished and AM control rats were chemically similar, and the affinity and number of antigenic determinants were the same. Malnutrition therefore leads to an absolute decrease in intestinal mucin rather than reduced molecular antigenicity. Impaired capacity to maintain mucosal mucin content may be a factor in reducing intestinal resistance to enteric infection in malnutrition.

Effect of therapy on left ventricular function in hypertension

1. Twelve untreated hypertensive patients whose blood pressure was 171.8 +/- 5.5 mmHg systolic and 119.7 +/- 3.4 mmHg diastolic (mean +/- SEM) were treated aggressively with diuretics plus other antihypertensive agents. Echocardiograms were performed before, and 2 weeks, 3 months and 6 months after therapy. Blood pressures were lowered to an average of 142/98 mmHg over the 6 month period. 2. Mean velocity of circumferential fibre shortening rose from 1.1 +/- 0.09 to 1.3 +/- 0.06 diameters/s at 2 weeks and remained elevated at the end of 3 months (1.3 +/- 0.03 diameters/s) (P < 0.025), but returned to the control level in 6 months. Similarly, ejection fraction increased significantly during the same period from a control value of 65.1 +/- 4.4 to 73.4 +/- 1.8% (P < 0.025) and persisted in this range at 3 months. At 6 months the ejection fraction had returned to pretreatment levels. There were significant reductions in left ventricular end-systolic and end-diastolic dimensions. Left ventricular mass index decreased from 182.3 +/- 18.3 to 163.8 +/- 12.4 g/m2 after 6 months of therapy. 3. These results indicate that in the early stages of blood pressure reduction there is a temporary increase in ejection phase indices, probably related to afterload reduction. The reduction in the left ventricular mass index suggests that increased cardiac muscle mass due to elevated blood pressure may be partially reversible after long-term reduction in blood pressure.