A robust quality infrastructure is key to safe and effective delivery of immune effector cells: how FACT-finding can help

ABSTRACT

Immune effector cells (IECs) include a broad range of immune cells capable of modulating several disease states, including malignant and nonmalignant conditions. The growth in the use of IECs as both investigational and commercially available products requires medical institutions to develop workflows/processes to safely implement and deliver transformative therapy. Adding to the complexity of this therapy are the variety of targets, diseases, sources, and unique toxicities that a patient experiences following IEC therapy. For over 25 years, the Foundation for the Accreditation of Cellular Therapy (FACT) has established a standard for the use of cellular therapy, initially with hematopoietic cell transplantation (HCT), and more recently, with the development of standards to encompass IEC products such as chimeric antigen receptor (CAR)-T cells. To date, IEC therapy has challenged the bandwidth and infrastructure of the institutions offering this therapy. To address these challenges, FACT has established a programmatic framework to improve the delivery of IEC therapy. In this study, we outline the current state of IEC program development, accreditation, and solutions to the challenges that programs face as they expand their application to novel IEC therapy.

Abstract 5579: First-in-human study of ICAM-1-specific affinity tuned CAR T cells against advanced thyroid cancer

Background: The use of chimeric antigen receptor (CAR) T cells for solid tumors has a number of challenges, such as lack of tumor-specific targets, CAR T cell exhaustion, and the immunosuppressive tumor microenvironment. To address these challenges, AffyImmune has developed technologies to affinity tune and track CAR T cells in patients. The targeting moiety is affinity tuned to preferentially bind to tumor cells overexpressing the target while leaving normal cells with low basal levels untouched, thereby increasing the therapeutic window and allowing for more physiological T cell killing. The CAR T cells are engineered to co-express somatostatin receptor 2 (SSTR2), which allows for the tracking of CAR T cells in vivo via PET/CT scan using FDA-approved DOTATATE.

Methods: AIC100 was generated by affinity tuning the I-domain of LFA-1, the physiological ligand to ICAM-1. Various mutants with 106-fold difference in affinity were evaluated for structure activity relationships using targets with varying antigen densities. The AIC100 with micromolar affinity was clearly the most effective in non-clinical animal models. AIC100 is currently being evaluated to assess safety, CAR T expansion, tumor localization, and preliminary activity in patients with advanced thyroid cancer (ATC) in a phase I study (NCT04420754). Our study uses a modified toxicity probability interval design with three dosage groups of 10 × 106, 100 × 106, and 500 × 106 cells.

Results: Preclinical studies demonstrated greater in vivo anti-tumor activity and safety with micromolar affinity CAR T cells. A single dose of AIC100 resulted in tumor elimination and significantly improved survival of animals bearing ATC xenografts. AIC100 activity was confirmed in other high ICAM-1 tumor models including breast cancer, gastric cancer, and multiple myeloma. In a Phase I patient given 10 × 106 CAR T cells, near synchronous imaging of FDG and DOTATATE revealed preliminary evidence of transient CAR T expansion and tumor reduction at multiple tumor lesions, with the peak of CAR T cell density coinciding with the spike in CAR T cell numbers in blood.

Conclusion: We have developed affinity tuned CAR T cells designed to selectively target ICAM-1 overexpressing tumor cells and to spatiotemporally image CAR T cells. Near-synchronous FDG and DOTATATE scans will enhance patient safety by early detection of off-tumor CAR T activity and validation of tumor response. We anticipate that our “tune and track” technology will be widely applicable to developing potent yet safe CAR T cells against hard-to-treat solid cancers.

Citation Format: Jingmei Hsu, Yen-Michael Hsu, Koen van Besien, Thomas J. Fahey, Jana Ivanidze, Janusz Puc, Karrie Du, Yanping Yang, Yogindra Vedvyas, Irene M. Min, Eric von Hofe, Moonsoo M. Jin. First-in-human study of ICAM-1-specific affinity tuned CAR T cells against advanced thyroid cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5579.

Abstract 558: Focused IL-12 cytokine delivery enhances function of affinity-tuned and real-time tracked ICAM-1-specific CAR T cells in solid tumors

Engineering CAR T cells to target solid tumors presents numerous challenges. Lack of tumor-specific antigens, high probability of CAR T cell exhaustion, and an often-immunosuppressive tumor microenvironment limit CAR T cell efficacy and outcomes in the clinic. To address these challenges, AffyImmune has developed “Tune & Track” technologies to reduce CAR affinity for antigens with disproportionally high density on tumor cells. Our CAR T cells are selective for tumor cells while leaving normal cells untouched, thereby increasing the therapeutic window and allowing for more physiological T cell killing. CAR T cells are also designed to express Somatostatin Receptor 2 (SSTR2), which allows for tracking in vivo via PET/CT scan using FDA-approved DOTATATE. Our primary CAR design called AIC100 expresses an affinity-tuned variant of LFA-1, which is the natural ligand for Intracellular Adhesion Molecule (ICAM)-1, a molecule that is highly expressed on some cancers. A single dose of AIC100 CAR T cells results in elimination of tumors in mice and significantly improves survival. We have tested the safety and anti-tumor activity of AIC100 in high ICAM-1-expressing animal tumor models including triple-negative breast cancer and gastric cancer. AffyImmune is currently conducting a Phase I study (NCT04420754) to evaluate the clinical efficacy of AIC100 in treating advanced thyroid cancer. After receiving 10 million AIC100 CAR T cells, FDG and DOTATATE imaging revealed preliminary evidence of CAR T expansion in the patient and tumor reduction at multiple lesions. To further optimize affinity-tuned CAR T cell activity within tumors, we are currently developing CAR designs that have the capability to deliver effector cytokines to the tumor microenvironment via a nuclear factor of activated T cells (NFAT)-inducible promoter. Because our CAR T cells are affinity-tuned, off-tumor cytokine secretion is minimized. Our ICAM-1-specific CAR design called AIC1010 releases interleukin (IL)-12 cytokine upon engagement with target antigen within tumors, which induces production of interferon (IFN)-γ from immune cells and surrounding tissues, enhancing not only CAR T cell effector function but also the immune response focused within the tumor microenvironment. AIC1010 CAR T cells demonstrate superior cancer elimination compared to AIC100 CAR T cells in subcutaneous and IP tumor models in mice. We anticipate that cytokine delivery, paired with our “Tune & Track” technology will be widely adaptable to develop potent and safe affinity-tuned CAR T cells against hard-to-treat solid cancers.

Citation Format: Jingmei Hsu, Michael P. Gallagher, Yanping Yang, Eric von Hofe, Yen-Michael Hsu, Koen Van Besien, Thomas Fahey, Jana Ivanidze, Janusz Puc, Karrie Du, Moonsoo Jin. Focused IL-12 cytokine delivery enhances function of affinity-tuned and real-time tracked ICAM-1-specific CAR T cells in solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 558.

Phase I study of AIC100 in relapsed and/or refractory advanced thyroid cancer and anaplastic thyroid cancer

6093

Background: ICAM-1 is a cell surface glycoprotein that is typically expressed on endothelial cells and immune cells and a ligand for LFA-1 integrin. It is also overexpressed in several malignancies, in particular anaplastic and advanced thyroid cancer. We designed an affinity tuned ICAM-1-directed CAR T cell (micromolar affinity) that preferentially binds overexpressed ICAM-1 on tumor cells and spares normal cells. The CAR T cells also express somatostatin receptor 2 (SSTR2), which allows tracking of CAR T cells in vivo via DOTATATE PET/CT scan. Murine studies showed excellent responses in ICAM-1 expressing thyroid cancer without significant toxicities. We are conducting a first-in-human phase 1 clinical trial to evaluate the feasibility, safety and preliminary efficacy of ICAM-1 in patients with relapsed/refractory thyroid cancer or anaplastic thyroid cancer who are BRAF wild-type, or BRAF mutated after failure of BRAF specific therapy (NCT04420754). Methods: This is a dose-escalation study with modified toxicity probability interval design and cohorts of 3 Patients. Patients receive a single dose of 1x 107 (Cohort 1), 1 x 108 (Cohort 2) or 5 x 108 (Cohort 3) ICAM-1 CAR T cells after FLU/CY lymphodepleting (LD) chemotherapy. Additional CAR T infusion is allowed if patients achieve partial response or stable disease. Whole-body Fluorodeoxyglucose (FDG) and DOTATATE PET/CT is used to stage tumor and track CAR T cells in vivo, respectively. Results: All ICAM-1 CAR T infusion products met target transduction efficiency. Two patients with progressive anaplastic thyroid cancer received ICAM-1 CAR T therapy at dose-level I. Evaluation of CAR T cellular kinetics demonstrated transient peripheral blood CAR T cell expansion. One patient developed grade 1 cytokine release syndrome (CRS) with fever. Several tumor lesions from this patient showed DOTATATE avidity, indicating CAR T homing to the tumor, concomitant with decrease in FDG avidity, suggesting biological activity at ̃2 weeks post CAR T infusion. DOTATATE avidity at 2 weeks post CAR T infusion also appeared to match that of CAR T abundance in the blood. Updated results on additional patients and cohorts will be presented. Conclusions: Adoptive cellular therapy with ICAM-1 directed CAR T is safe and feasible at dose level 1 in patients with anaplastic thyroid cancer. DOTATATE PET allows visualization of expansion and homing of SSTR2 expressing CAR T cells, while concomitant FDG PET permits correlation with biological activity. Clinical trial information: NCT04420754.

Outcomes of Allogeneic Stem Cell Transplant for Elderly Patients with Hematologic Malignancies

Reduced-intensity conditioning (RIC) regimens, improved HLA matching, and better supportive care allow allogeneic stem cell transplant (alloSCT) to be offered to older patients. Only a small percentage of eligible patients between ages 65 and 74 years actually undergo alloSCT, and comprehensive outcome data from the aging population are still lacking. We examined the outcome of older patients who underwent alloSCT using melphalan-based RIC for hematologic malignancies at our institution. We identified 125 patients older than 65 years (median, 69; range, 66 to 77) who underwent matched related donor, matched unrelated donor, or combined haploidentical/umbilical cord alloSCT between 2012 through November, 2017. Among them, 52 (41.6%) and 70 (56%) had, respectively, intermediate and high/very high Center for International Blood and Marrow Transplant Research (CIBMTR) disease risk index (DRI). One hundred six patients (85%) received fludarabine/melphalan-based RIC regimen with either antithymocyte globulin (ATG) or alemtuzumab. The median time to neutrophil engraftment was 13 days (range, 8 to 37) and platelet engraftment 17 days (range, 9 to 169). The cumulative incidence of nonrelapse mortality was 11.5% at 100 days and 30.1% and 34.8% at 1 and 2 years, respectively. The cumulative incidence of relapse was 35% and 40% at 1 and 2 years. The cumulative incidence of grades II to IV acute graft-versus-host disease (GVHD) at day 100 and 6 months was 29.5% and 34.5%, and chronic GVHD at 6, 12, and 24 months was 2.5%, 5.2%, and 6.3%, respectively. With a median follow-up of 32 months, the 1-, 2-, and 3-year progression-free survival (PFS) was 34.6%, 24.4%, and 16.5%, respectively. The graft GVHD-free survival was 24.6%, 16.1%, and 9.3%, respectively. The 1-, 2-, and 3-year overall survival (OS) was 44.5%, 30.7%, and 26.5%, respectively. In multivariable analysis, low albumin was predictive of poor PFS and OS and high hematopoietic cell transplantation-specific comorbidity index, and CIBMTR DRI was predictive of worse graft GVHD-free survival. Among long-term survivors the median Karnofsky performance status was 80. Older patients, even when referred with advanced disease, can benefit from melphalan-based alloSCT with HLA-matched or alternative donor sources without discernible impact of donor source on outcome. Using alemtuzumab- or ATG-based in vivo T cell depletion, the incidence of chronic GVHD is extremely low. Performance status in survivors is excellent. Better predictors for outcome in this patient population need to be identified.

Cord blood chimerism and relapse after haplo-cord transplantation

Haplo-cord stem cell transplantation combines the infusion of CD34 selected hematopoietic progenitors from a haplo-identical donor with an umbilical cord blood (UCB) graft from an unrelated donor and allows faster count recovery, with low rates of disease recurrence and chronic graft-versus-host disease (GVHD). But the contribution of the umbilical cord blood graft to long-term transplant outcome remains unclear. We analyzed 39 recipients of haplo-cord transplants with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS), engrafted and in remission at 2 months. Median age was 66 (18-72) and all had intermediate, high, or very-high risk disease. Less than 20% UCB chimerism in the CD33 lineage was associated with an increased rate of disease recurrence (54% versus 11% p < 0.0001) and decrease in one year progression-free (20% versus 55%, p = 0.004) and overall survival (30% versus 62%, p = 0.02). Less than 100% UCB chimerism in the CD3 lineage was associated with increase rate of disease recurrence (46% versus 12%, p = 0.007). Persistent haplo-chimerism in the CD3 lineage was associated with an increased rate of disease recurrence (40% versus 15%, p = 0.009) Chimerism did not predict for treatment related mortality. The cumulative incidence of acute GVHD by day 100 was 43%. The cumulative incidence of moderate/severe chronic GVHD was only 5%. Engraftment of the umbilical cord blood grafts provides powerful graft-versus-leukemia (GVL) effects which protect against disease recurrence and is associated with low risk of chronic GVHD. Engraftment of CD34 selected haplo-identical cells can lead to rapid development of circulating T-cells, but when these cells dominate, GVL-effects are limited and rates of disease recurrence are high.

Tumour necrosis factor-alpha enhances bradykinin-induced signal transduction via activation of Ras/Raf/MEK/MAPK in canine tracheal smooth muscle cells

Inhalation of tumour necrosis factor-alpha (TNF-alpha) induced a bronchial hyperreactivity to contractile agonists. However, the mechanisms of TNF-alpha involved in the pathogenesis of bronchial hyperreactivity were not completely understood. Therefore, we investigated the effect of TNF-alpha on bradykinin (BK)-induced inositol phosphate (IP) accumulation and Ca(2+) mobilization, and up-regulation of BK receptor density in canine cultured tracheal smooth muscle cells (TSMCs). Pretreatment of TSMCs with TNF-alpha potentiated BK-induced IP accumulation and Ca(2+) mobilization. However, there was no effect on the IP response induced by endothelin-1 (ET-1), 5-hydroxytryptamine (5-HT), and carbachol. Pretreatment with PDGF B-chain homodimer (PDGF-BB) also enhanced BK-induced IP response. These enhancements induced by TNF-alpha and PDGF-BB might be due to an increase in BK B(2) receptor density (B(max)), since [3H]BK binding to TSMCs was inhibited by the B(2) selective agonist and antagonist, BK and Hoe 140, but not by the B(1) selective reagents. The enhancing effects of TNF-alpha and PDGF-BB were attenuated by PD98059 (an inhibitor of activation of MAPK kinase, MEK) and cycloheximide (an inhibitor of protein synthesis), suggesting that TNF-alpha may share a common signalling pathway with PDGF-BB via protein(s) synthesis in TSMCs. Furthermore, overexpression of dominant negative mutants, H-Ras-15A and Raf-N4, significantly suppressed p42/p44 mitogen-activated protein kinase (MAPK) activation induced by TNF-alpha and PDGF-BB and attenuated the effect of TNF-alpha on BK-induced IP response, indicating that Ras and Raf may be required for activation of these kinases. These results suggest that the augmentation of BK-induced responses produced by TNF-alpha might be, at least in part, mediated through activation of Ras/Raf/MEK/MAPK pathway in TSMCs.

Structure of CD40 ligand in complex with the Fab fragment of a neutralizing humanized antibody

BACKGROUND

CD40 ligand (CD40L or CD154), a member of the tumor necrosis factor (TNF) family, plays a critical role in both humoral and cellular immune responses and has been implicated in biological pathways involving epithelial cells, fibroblasts, and platelets. Such a pathway is T cell-mediated B cell activation, a process that occurs through the interaction of CD40L with CD40 receptor expressed on B cells. It results in various B cell responses, including immunoglobulin isotype switching and B cell differentiation and proliferation. These responses can be inhibited by the monoclonal antibody 5c8, which binds with high affinity to CD40L.

RESULTS

To understand the structural basis of the inhibition, we determined the crystal structure of the complex of the extracellular domain of CD40L and the Fab fragment of humanized 5c8 antibody. The structure shows that the complex has the shape of a three-bladed propeller with three Fab fragments bound symmetrically to a CD40L homotrimer. To further study the nature of the antibody-antigen interface, we assessed the ability of 23 site-directed mutants of CD40L to bind to 5c8 and CD40 and analyzed the results in the context of the crystal structure. Finally, we observed via confocal microscopy that 5c8 binding to CD40L on the cell surface results in the formation of patches of clustered complexes.

CONCLUSIONS

The structure reveals that 5c8 neutralizes CD40L function by sterically blocking CD40 binding. The antigenic epitope is localized in a region of the surface that is likely to be structurally perturbed as a result of genetic mutations that cause hyper-IgM syndrome. The symmetric trimeric arrangement of the Fab fragments in the complex results in a geometry that facilitates the formation of large clusters of complexes on the cell surface.

Interleukin-1beta enhances bradykinin-induced phosphoinositide hydrolysis and Ca2+ mobilization in canine tracheal smooth-muscle cells: involvement of the Ras/Raf/mitogen-activated protein kinase (MAPK) kinase (MEK)/MAPK pathway

Elevated levels of several cytokines including interleukin-1beta (IL-1beta) have been detected in airway fluid of asthmatic patients. Inhalation of IL-1beta induced a bronchial hyper-reactivity to contractile agonists. However, the implication of IL-1beta in the pathogenesis of bronchial hyper-reactivity is not completely understood. Therefore, we investigated the effect of IL-1beta on bradykinin (BK)-induced inositol phosphate [Ins(X)P] accumulation and Ca2+ mobilization, and up-regulation of BK receptor density in canine cultured tracheal smooth-muscle cells (TSMCs). Treatment of TSMCs with IL-1beta potentiated BK-induced Ins(X)P accumulation and Ca2+ mobilization. However, there was no effect on the Ins(X)P response induced by endothelin-1, 5-hydroxytryptamine or carbachol. Treatment with platelet-derived growth factor B-chain homodimer (PDGF-BB) also enhanced the BK-induced Ins(X)P response. These enhancements by IL-1beta and PDGF-BB might be due to an up-regulation of BK B(2) receptor density (B(max)), since [(3)H]BK binding to TSMCs was inhibited by the B(2)-selective agonist and antagonist, BK and Hoe 140, but not by B(1)-selective reagents. The enhancing effects of IL-1beta and PDGF-BB on Ins(X)P accumulation, Ca2+ mobilization and B(max) were attenuated by PD98059 [an inhibitor of activation of mitogen-activated protein kinase (MAPK) kinase, MEK] and cycloheximide (an inhibitor of protein synthesis), suggesting that IL-1beta may share a common signalling pathway with PDGF-BB via protein synthesis. Furthermore, overexpression of dominant negative mutants, H-Ras-15A and Raf-N4, significantly suppressed the up-regulation of BK receptors induced by IL-1beta, indicating that Ras and Raf may be required for activation of these kinases. These results suggest that the augmentation of BK-induced responses produced by IL-1beta might be, at least in part, mediated through activation of the Ras/Raf/MEK/MAPK pathway in TSMCs.

CD154 variant lacking tumor necrosis factor homologous domain inhibits cell surface expression of wild-type protein

X-linked hyper-IgM (XHIM) syndrome is an immunological disorder resulting from mutations in the CD154 gene. Some mutations occur in splicing sites and result in transcripts encoding wild-type and mutant proteins. These mutants lack the tumor necrosis factor homologous (TNFH) domain and consequently fail to trimerize. Given that the TNFH domain is responsible for trimerization, one may predict that the TNFH mutant can not participate in the assembly of wild-type CD154. Thus, it was puzzling why these patients exhibit XHIM phenotype, presumably resulting from a lack of functional CD154. One possibility is that the TNFH mutant exhibits a dominant negative effect over the wild-type protein. To investigate this, we coexpressed the wild-type protein and a TNFH mutant and examined the biochemical and functional properties of the resulting CD154 products. We demonstrate that despite the lack of the TNFH domain, the TNFH mutant can associate with the wild-type protein. Furthermore, such an association compromises the ability of the wild-type protein to mature onto the cell surface. These results provide a mechanism for the defect of CD154 in XHIM patients producing both wild-type and TNFH variants and suggest that besides the TNFH domain, the stalk region participates in the assembly of CD154 trimers.

CD154 variants associated with hyper-IgM syndrome can form oligomers and trigger CD40-mediated signals

X-linked hyper-IgM syndrome is a rare immunodeficiency disorder resulting from mutations in the gene encoding the CD40 ligand (CD154) molecule. These mutations are very heterogeneous, ranging from a single point mutation to a large deletion in the open reading frame. To investigate the molecular mechanisms that are responsible for the functional defect of these mutants, we examined the biochemical properties of 14 hyper-IgM-related CD154 mutant proteins produced by transient expression in COS7 cells. We show that deletion mutants lacking a significant portion of the tumor necrosis factor homologous domain cannot be stably produced. In contrast, point mutants can be detected as oligomers. Surprisingly, gene products of two point mutants, Thr-211 --> Asp and Met-36 --> Arg, can bind to the receptor, CD40. For Thr-211 --> Asp variant, it is comparable to the wild-type protein in its surface expression level, biochemical structure, and functional activities. Thus, it appears that this mutation is a polymorphism of CD154 gene. For Met-36 --> Arg variant, although it is interactive with CD40, it has a much lower surface expression level than wild-type protein. We propose that Met-36 --> Arg mutant represents a prototype of a defective CD154 family whose low cell surface expression of intrinsically active protein is simply insufficient to trigger productive signals through CD40.

Lung cancer mimicking acute myocardial infarction on electrocardiogram

Myocardial involvement by malignant neoplasm is rare and often not clinically manifested. The diagnosis is usually made only at autopsy. A 71-year-old man with squamous cell lung cancer presented with chest discomfort. His electrocardiogram was diagnostic of acute myocardial infarction. However, because of the lack of classic symptoms and signs of acute myocardial infarction and normal serum levels of cardiac enzymes, an echocardiography was performed before initiation of thrombolytic therapy. The echocardiography showed a huge hyperechoic mass located in the posterolateral aspect of the left ventricle with myocardium invasion. Thrombolytic therapy was withheld. In patients with lung cancer, an electrocardiogram representative of acute myocardial infarction can rarely be induced by myocardial involvement with lung cancer.

Leukocyte transfusion-associated granulocyte responses in a patient with X-linked hyper-IgM syndrome

X-linked hyper-IgM syndrome (XHIM) is a severe congenital immunodeficiency caused by mutations in CD154 (CD40 ligand, gp39), the T cell ligand for CD40 on B cells. Chronic or cyclic neutropenia is a frequent complicating feature that heightens susceptibility to severe infections. We describe a patient with a variant of XHIM who produced elevated levels of serum IgA as well as IgM and suffered from chronic severe neutropenia. Eight of ten leukocyte transfusions with cells from a maternal aunt, performed because of mucosal infections, resulted in similar episodes of endogenous granulocyte production. Transfection studies with the mutant CD154 protein indicate that the protein is expressed at the cell surface and forms an aberrant trimer that does not interact with CD40. The data suggest that allogeneic cells from the patient's aunt, probably activated T cells bearing functional CD154, may interact with CD40+ recipient cells to produce maturation of myeloid precursors in the bone marrow.

Effect of forskolin on endothelin-induced phosphoinositide hydrolysis and calcium mobilization in cultured canine tracheal smooth muscle cells

1. The effects of increase in intracellular adenosine 3':5'-cyclic monophosphate (cAMP) on endothelin-1 (ET-1)-induced generation of inositol phosphates (IPs) and increase in intracellular Ca2+ ([Ca2+]i) were investigated in canine cultured tracheal smooth muscle cells (TSMCs). 2. Pretreatment of TSMCs with either cholera toxin (CTX; 10 microg ml(-1), 4 h), forskolin (10 microM, 30 min), or dibutyryl cAMP (1 mM, 30 min) inhibited ET-1-stimulated Ca2+ mobilization (by 23 +/- 5%, n = 8) and IPs accumulation (by 32 +/- 6%, n = 4). While after treatment with forskolin for 24 h, the cells retained the ability to respond to ET-1-induced Ca2+ mobilization to the same extent as the control group. 3. Forskolin (1-100 microM) inhibited the ET-1-induced increase in [Ca2+]i, but the lower concentrations had little effect on this response. The inhibitory effects of these agents produced both depression of the maximal response and a shift to the right of the concentration-response curve of ET-1 without changing the -logEC50 values. 4. The water-soluble forskolin analogue L-858051, 7-deacetyl-7beta-(gamma-N-methylpiperazino)-butyryl forskolin, significantly inhibited ET-1-stimulated IPs accumulation. In contrast, the addition of 1,9-dideoxy forskolin, an inactive analogue of forskolin, had little effect on stimulated responses. Moreover, SQ-22536, 9-(tetrahydro-2-furanyl)-9H-purin-6-amine, an inhibitor of adenylate cyclase, and both H-89, N-(2-aminoethyl)-5-isoquinolinesulfonamide, and HA-1004, N-(2-guanidinoethyl)-5-isoquinolinesulfonamide, inhibitors of cAMP-dependent protein kinase (PKA), attenuated the ability of forskolin to inhibit ET-1-induced IPs accumulation. These results suggest that activation of cAMP/PKA was involved in these inhibitory effects of forskolin. 5. The locus of this inhibition of forskolin treatment on AlF4(-)-stimulated IPs accumulation was investigated in canine TSMCs. The AlF4(-)-induced IPs accumulation was inhibited by forskolin, supporting that G protein(s) are directly activated by AlF4- and uncoupled to phospholipase C by forskolin treatment. 6. We conclude that cAMP elevating agents inhibit ET-1-stimulated generation of IPs and Ca2+ mobilization in canine cultured TSMCs. Since generation of IPs and increases in [Ca2+]i are very early events in the activation of ET-1 receptors, attenuation of these events by cAMP elevating agents might well contribute to the inhibitory effect of cAMP on tracheal smooth muscle function.

The role of polar interactions in the molecular recognition of CD40L with its receptor CD40

CD40 Ligand (CD40L) is transiently expressed on the surface of T-cells and binds to CD40, which is expressed on the surface of B-cells. This binding event leads to the differentiation, proliferation, and isotype switching of the B-cells. The physiological importance of CD40L has been demonstrated by the fact that expression of defective CD40L protein causes an immunodeficiency state characterized by high IgM and low IgG serum levels, indicating faulty T-cell dependent B-cell activation. To understand the structural basis for CD40L/CD40 association, we have used a combination of molecular modeling, mutagenesis, and X-ray crystallography. The structure of the extracellular region of CD40L was determined by protein crystallography, while the CD40 receptor was built using homology modeling based upon a novel alignment of the TNF receptor superfamily, and using the X-ray structure of the TNF receptor as a template. The model shows that the interface of the complex is composed of charged residues, with CD40L presenting basic side chains (K143, R203, R207), and CD40 presenting acidic side chains (D84, E114, E117). These residues were studied experimentally through site-directed mutagenesis, and also theoretically using electrostatic calculations with the program Delphi. The mutagenesis data explored the role of the charged residues in both CD40L and CD40 by switching to Ala (K143A, R203A, R207A of CD40L, and E74A, D84A, E114A, E117A of CD40), charge reversal (K143E, R203E, R207E of CD40L, and D84R, E114R, E117R of CD40), mutation to a polar residue (K143N, R207N, R207Q of CD40L, and D84N, E117N of CD40), and for the basic side chains in CD40L, isosteric substitution to a hydrophobic side chain (R203M, R207M). All the charge-reversal mutants and the majority of the Met and Ala substitutions led to loss of binding, suggesting that charged interactions stabilize the complex. This was supported by the Delphi calculations which confirmed that the CD40/CD40L residue pairs E74-R203, D84-R207, and E117-R207 had a net stabilizing effect on the complex. However, the substitution of hydrophilic side chains at several of the positions was tolerated, which suggests that although charged interactions stabilize the complex, charge per se is not crucial at all positions. Finally, we compared the electrostatic surface of TNF/TNFR with CD40L/CD40 and have identified a set of polar interactions surrounded by a wall of hydrophobic residues that appear to be similar but inverted between the two complexes.

TWEAK, a new secreted ligand in the tumor necrosis factor family that weakly induces apoptosis

The members of the tumor necrosis factor (TNF) family play pivotal roles in the regulation of the immune system. Here we describe a new ligand in this family, designated TWEAK. The mouse and human versions of this protein are unusually conserved with 93% amino acid identity in the receptor binding domain. The protein was efficiently secreted from cells indicating that, like TNF, TWEAK may have the long range effects of a secreted cytokine. TWEAK transcripts were abundant and found in many tissues, suggesting that TWEAK and TRAIL belong to a new group of widely expressed ligands. Like many members of the TNF family, TWEAK was able to induce interleukin-8 synthesis in a number of cell lines. The human adenocarcinoma cell line, HT29, underwent apoptosis in the presence of both TWEAK and interferon-gamma. Thus, TWEAK resembles many other TNF ligands in the capacity to induce cell death; however, the fact that TWEAK-sensitive cells are relatively rare suggests that TWEAK along with lymphotoxins alpha/beta and possibly CD30L trigger death via a weaker, nondeath domain-dependent mechanism.

A humanized form of a CD4-specific monoclonal antibody exhibits decreased antigenicity and prolonged plasma half-life in rhesus monkeys while retaining its unique biological and antiviral properties

Certain monoclonal antibodies (MAbs) directed against CD4 can efficiently block HIV-1 replication in vitro. To explore CD4-directed passive immunotherapy for prevention or treatment of AIDS virus infection, we previously examined the biological activity of a nondepleting CD4-specific murine MAb, mu5A8. This MAb, specific for domain 2 of CD4, blocks HIV-1 replication at a post-gp120-CD4 binding step. When administered to normal rhesus monkeys, all CD4+ target cells were coated with antibody, yet no cell clearance or measurable immunosuppression occurred. However, strong anti-mouse Ig responses rapidly developed in all monkeys. In the present study, we report a successfully humanized form of mu5A8 (hu5A8) that retains binding to both human and monkey CD4 and anti-AIDS virus activity. When administered intravenously to normal rhesus monkeys, hu5A8 bound to all target CD4+ cells without depletion and showed a significantly longer plasma half-life than mu5A8. Nevertheless, an anti-hu5A8 response directed predominantly against V region determinants did eventually appear within 2 to 4 weeks in most animals. However, when hu5A8 was administered to rhesus monkeys chronically infected with the simian immunodeficiency virus of macaques, anti-hu5A8 antibodies were not detected. Repeated administration of hu5A8 in these animals resulted in sustained plasma levels and CD4+ cell coating with humanized antibody for 6 weeks. These studies demonstrate the feasibility of chronic administration of CD4-specific MAb as a potential means of treating or preventing HIV-1 infection.

Exaggerated luminal loss a few minutes after successful percutaneous transluminal coronary angioplasty in patients with recent myocardial infarction compared with stable angina: an intracoronary ultrasound study

This study investigates the mechanisms of exaggerated acute luminal loss after successful coronary angioplasty in patients with recent myocardial infarction compared with stable angina by angiography and intracoronary ultrasound (ICUS). We studied 15 consecutive patients (group 1) who, after a successful thrombolysis for myocardial infarction, underwent delayed (8 +/- 2 days after the myocardial infarction) successful balloon coronary angioplasty. Group 1 patients were individually matched with 15 stable angina patients (group 2). The percentage of stenosis and acute luminal loss were measured by quantitative coronary analysis. The ultrasound characteristics of lumen pathology were described as soft, hard, calcified, eccentric, concentric, thrombotic, and dissection lesions. Matching by stenosis location, reference diameter, sex, and age resulted in 2 comparable groups of 15 lesions with identical baseline characteristics. Immediately after percutaneous transluminal coronary angioplasty (PTCA), the minimal luminal diameter increased from 0.5 +/- 0.3 mm to 2.4 +/- 0.3 mm and from 0.5 +/- 0.2 mm to 2.4 +/- 0.3 mm in groups 1 and 2, respectively. Similar balloon sizes were used in both groups. The acute luminal loss (the difference between the maximal dilated balloon diameter and the minimal luminal diameter) immediately after PTCA was 0.4 +/- 0.2 mm and 0.3 +/- 0.3 mm (14 +/- 8% and 10 +/- 11% of balloon size) (P = not significant [NS]) in groups 1 and 2, respectively. After ICUS (mean 24 min after the last balloon deflation), the acute luminal loss was 0.9 +/- 0.3 mm and 0.5 +/- 0.4 mm (29 +/- 11% and 17 +/- 8% of balloon size) (P = 0.01) in groups 1 and 2, respectively. There was a significantly higher prevalence of intracoronary thrombus formation as detected by ICUS in group 1 compared with group 2 (80% vs. 20%; P < 0.001). In matched groups of successfully treated coronary angioplasty, patients with recent myocardial infarction had a similar magnitude of acute gained luminal loss immediately after the procedure. However, an exaggerated luminal loss a few minutes after the last balloon deflation in patients with recent myocardial infarction was noted because of mural thrombus formation compared with patients with stable angina.

Heteromultimeric complexes of CD40 ligand are present on the cell surface of human T lymphocytes

CD40 ligand (CD40L), a 33-kDa type II membrane glycoprotein expressed primarily on activated CD4+ T lymphocytes, is responsible for the helper function of T cells on resting B cells in a non-antigen-dependent, non-major histocompatability complex-restricted fashion. Interaction of CD40L with its receptor CD40 induces proliferation of and isotype switching in B lymphocytes. Recently we solved the x-ray structure of recombinant soluble CD40L and showed that, similar to other members of the tumor necrosis factor family, CD40L indeed exists as a trimer. We now report that, under normal physiological conditions, CD40L molecules exist as heteromultimeric complexes. These CD40L complexes, made of the full length and smaller fragments of CD40L, are present on the cell surface of T lymphocytes and are capable of interacting with CD40 molecule. A prominent fragment with a mass of 31 kDa accounts for as much as half of the CD40L on the surface of Jurkat cells. N-terminal sequence data revealed that this fragment lacks the cytoplasmic tail. A minor 18-kDa fragment of CD40L was also characterized which lacks the cytoplasmic tail, transmembrane region, and stalk region of the extracellular domain. The presence of CD40L heteromultimeric variants implies an additional regulation of the functional activity of this ligand complex.

2 A crystal structure of an extracellular fragment of human CD40 ligand

BACKGROUND

The CD40 ligand (CD40L) is a member of the tumor necrosis factor (TNF) family of proteins and is transiently expressed on the surface of activated T cells. The binding of CD40L to CD40, which is expressed on the surface of B cells, provides a critical and unique pathway of cellular activation resulting in antibody isotype switching, regulation of apoptosis, and B cell proliferation and differentiation. Naturally occurring mutations of CD40L result in the clinical hyper-IgM syndrome, characterized by an inability to produce immunoglobulins of the IgG, IgA and IgE isotypes.

RESULTS

We have determined the crystal structure of a soluble extracellular fragment of human CD40L to 2 A resolution and with an R factor of 21.8%. Although the molecule forms a trimer similar to that found for other members of the TNF family, such as TNF alpha and lymphotoxin-alpha, and exhibits a similar overall fold, there are considerable differences in several loops including those predicted to be involved in CD40 binding.

CONCLUSIONS

The structure suggests that most of the hyper-IgM syndrome mutations affect the folding and stability of the molecule rather than the CD40-binding site directly. Despite the fact that the hyper-IgM syndrome mutations are dispersed in the primary sequence, a large fraction of them are clustered in space in the vicinity of a surface loop, close to the predicted CD40-binding site.

Leukocyte accumulation promoting fibrin deposition is mediated in vivo by P-selectin on adherent platelets

The glycoprotein P-selectin is a cell adhesion molecule of stimulated platelets and endothelial cells, which mediates the interaction of these cells with neutrophils and monocytes. It is a membrane component of cell storage granules, and is a member of the selectin family which includes E-selectin and L-selectin. P-selectin recognizes both lineage-specific carbohydrate ligands on monocytes and neutrophils, including the Lewis x antigen, sialic acid, and a protein component. In inflammation and thrombosis, P-selectin may mediate the interaction of leukocytes with platelets bound in the region of tissue injury and with stimulated endothelium. To evaluate the role of P-selectin in platelet-leukocyte adhesion in vivo, the accumulation of leukocytes within an experimental thrombus was explored in an arteriovenous shunt model in baboons. A Dacron graft implanted within an arteriovenous shunt is thrombogenic, accumulating platelets and fibrin within its lumen. These bound platelets express P-selectin. Here we show that antibody inhibition of leukocyte binding to P-selectin expressed on platelets immobilized on the graft blocks leukocyte accumulation and inhibits the deposition of fibrin within the thrombus. These results indicate that P-selectin is an important adhesion molecule on platelets, mediating platelet-leukocyte binding in vivo, that the presence of leukocytes in thrombi is mediated by P-selectin, and that these leukocytes promote fibrin deposition.

Effects of hypokalemia on the properties and expression of the (Na+,K+)-ATPase of rat skeletal muscle

Rats maintained on a low potassium diet develop hypokalemia, which is associated with an approximately 80% decrease in the number of (Na+,K+)-ATPase molecules in skeletal muscle sarcolemma (Norgaard, A., Kjeldsen, K., and Clausen, T. (1981) Nature 293, 739-741); the skeletal muscles of the hypokalemic rats become paralyzed after exposure to insulin in low [K+] media (Otsuka, M., and Ohtsuki, I. (1970) Am. J. Physiol. 219, 1178-1182). We have been interested in the interactions between the insulin receptor and the alpha 2 isoform of the (Na+,K+)-ATPase as a mechanism for the insulin activation of (Na+,K+)-pumping and decided to use the hypokalemic rats to obtain additional information on this question. We show here that the amount of the alpha 2 isoform in the skeletal muscles of hypokalemic rats is greatly decreased as determined by immunoblotting and (Na+,K+)-ATPase activity; the effect of hypokalemia on the amount of the alpha 1 isoform is small. The mechanism of the decrease in the alpha 2 isoform is not known, but it is not due to transcriptional regulation of the alpha 2 gene because the amounts of the transcripts for this polypeptide are increased in the rats on the low potassium diet. The (Na+,K+)-pump that remains in the skeletal muscles of rats on a low potassium diet for a period of 2 weeks is still activated by insulin; under these conditions, however, insulin does not bring about a decrease in the intracellular [Na+] in contrast to the situation with normal muscle.

Rat brain has the alpha 3 form of the (Na+,K+)ATPase

Multiple forms of the catalytic subunit of the (Na+,K+)ATPase have been identified in rat brain. While two of them (alpha 1 and alpha 2) have been well characterized, the third form (alpha 3) of these catalytic subunits only recently has been described by cDNA cloning; the corresponding polypeptide has not been isolated. In this paper it is shown that rat brain contains the alpha 3 chain. The catalytic subunits of the (Na+, K+)ATPase from rat brain axolemma were purified by SDS-PAGE and subjected to formic acid cleavage. Amino acid sequence analysis of the resulting fragments revealed that axolemma has the alpha 3 form of the catalytic subunit. In addition, alpha 3-specific antiserum was raised in rabbits immunized with a synthetic peptide. Immunoblotting with this antiserum revealed that the alpha 3 form of the (Na+,K+)ATPase is present also in whole brain microsomes. In SDS-PAGE, the mobilities of the three catalytic subunits of brain (Na+, K+)ATPase follow the order alpha 1 greater than alpha 2 greater than alpha 3. Determination of the ouabain-inhibitable ATPase activity indicates that if the alpha 3 form of the (Na+,K+)ATPase is able to hydrolyze ATP, it is present in a form of the enzyme with a high affinity for this cardiac glycoside and is similar to the alpha 2 form in this respect.

Growth control in cultured 3T3 fibroblasts. V. Purification of an Mr 13,000 polypeptide responsible for growth inhibitory activity

A growth regulatory factor, which reversibly inhibits DNA synthesis and proliferation of fibroblasts, has been isolated from medium conditioned by exposure to density-inhibited mouse 3T3 cells. This factor, termed FGR-s (13K), yielded a single polypeptide (Mr 13,000) when analyzed by SDS PAGE under both reducing and nonreducing conditions. The dose-response curve of growth inhibition by FGR-s (13K) showed that 50% inhibition of 3T3 cell proliferation was achieved at a concentration of approximately 3 ng/ml, corresponding to approximately 0.23 nM. The activity of FGR-s (13K) was depleted by passing the material over an affinity column containing the monoclonal antibody 2A4; this monoclonal antibody had been previously characterized to bind to the Mr 13,000 polypeptide. These results indicate that we have purified a growth regulatory factor that acts to inhibit the proliferation of cells in an autocrine pathway.

Growth control in cultured 3T3 fibroblasts: neutralization and identification of a growth-inhibitory factor by a monoclonal antibody

A fibroblast growth regulator, which inhibits the growth and division of proliferating fibroblasts, has been isolated from medium conditioned by exposure to density-inhibited mouse 3T3 cells. This partially purified preparation of the growth-inhibitory activity, termed FGR-s, contained two major polypeptides (Mrs, 10,000 and 13,000). Using FGR-s as the immunogen, we have carried out in vitro immunization of rat splenocytes and have generated hybridoma lines, each secreting an antibody directed against components of the FGR-s preparation. One such monoclonal antibody, designated 2A4, specifically bound the Mr 13,000 polypeptide of FGR-s. Antibody 2A4 also neutralized the growth-inhibitory effect of FGR-s in a concentration-dependent fashion. These results strongly suggest that the Mr 13,000 polypeptide carries growth-inhibitory activity.

Thiocardenolides II: synthesis and pharmacological evaluation of 3beta-thioacetyl-14beta-hydroxy-5beta-card-20(22)-enolide

The synthesis of a 3beta-thioacetylcardenolide is described. The thioacetate exhibited effects similar to those seen with digitoxigenin acetate on the isolated frog and guinea pig hearts at 1 X 10(-7) dilution. In the intact rat heart, the lethal dose was 5 mg/kg for the thioacetate and 2.5 mg/kg for digitoxigenin acetate. The thioacetate inhibited sodium- and potassium-activated adenosine triphosphatase to the same extent as digitoxigenin, but it was somewhat less inhibitory than digitoxigenin acetate.