Murine allogeneic CAR T cells integrated before or early after posttransplant cyclophosphamide exert antitumor effects

Relapse limits the therapeutic efficacy both of chimeric antigen receptor (CAR) T cells and allogeneic hematopoietic cell transplantation (allo-HCT). Patients may undergo these therapies sequentially to prevent or treat relapsed malignancy. However, direct integration of the 2 therapies has been avoided over concerns for potential induction of graft-versus-host disease (GVHD) by allogeneic CAR T cells. We have shown in murine T-cell-replete MHC-haploidentical allo-HCT that suppressive mechanisms induced immediately after posttransplant cyclophosphamide (PTCy), given on days +3/+4, prevent GVHD induction by alloreactive T cells infused as early as day +5. Therefore, we hypothesized that allogeneic CAR T cells given in a similarly integrated manner in our murine MHC-haploidentical allo-HCT model may safely exert antitumor effects. Indeed, allogeneic anti-CD19 CAR T cells given early after (day +5) PTCy or even prior to (day 0) PTCy cleared leukemia without exacerbating the cytokine release syndrome occurring from the MHC-haploidentical allo-HCT or interfering with PTCy-mediated GVHD prevention. Meanwhile, CAR T-cell treatment on day +9 or day +14 was safe but less effective, suggesting a limited therapeutic window. CAR T cells infused before PTCy were not eliminated, but surviving CAR T cells continued to proliferate highly and expand despite PTCy. In comparison with infusion on day +5, CAR T-cell infusion on day 0 demonstrated superior clinical efficacy associated with earlier CAR T-cell expansion, higher phenotypic CAR T-cell activation, less CD4+CD25+Foxp3+ CAR T-cell recovery, and transcriptional changes suggesting increased activation of CD4+ CAR T cells and more cytotoxic CD8+ CAR T cells. This study provides mechanistic insight into PTCy's impact on graft-versus-tumor immunity and describes novel approaches to integrate CAR T cells and allo-HCT that may compensate for deficiencies of each individual approach.

CRISPR-Cas9-AAV versus lentivector transduction for genome modification of X-linked severe combined immunodeficiency hematopoietic stem cells

Introduction

Ex vivo gene therapy for treatment of Inborn errors of Immunity (IEIs) have demonstrated significant clinical benefit in multiple Phase I/II clinical trials. Current approaches rely on engineered retroviral vectors to randomly integrate copy(s) of gene-of-interest in autologous hematopoietic stem/progenitor cells (HSPCs) genome permanently to provide gene function in transduced HSPCs and their progenies. To circumvent concerns related to potential genotoxicities due to the random vector integrations in HSPCs, targeted correction with CRISPR-Cas9-based genome editing offers improved precision for functional correction of multiple IEIs.

Methods

We compare the two approaches for integration of IL2RG transgene for functional correction of HSPCs from patients with X-linked Severe Combined Immunodeficiency (SCID-X1 or XSCID); delivery via current clinical lentivector (LV)-IL2RG versus targeted insertion (TI) of IL2RG via homology-directed repair (HDR) when using an adeno-associated virus (AAV)-IL2RG donor following double-strand DNA break at the endogenous IL2RG locus.

Results and discussion

In vitro differentiation of LV- or TI-treated XSCID HSPCs similarly overcome differentiation block into Pre-T-I and Pre-T-II lymphocytes but we observed significantly superior development of NK cells when corrected by TI (40.7% versus 4.1%, p = 0.0099). Transplants into immunodeficient mice demonstrated robust engraftment (8.1% and 23.3% in bone marrow) for LV- and TI-IL2RG HSPCs with efficient T cell development following TI-IL2RG in all four patients' HSPCs. Extensive specificity analysis of CRISPR-Cas9 editing with rhAmpSeq covering 82 predicted off-target sites found no evidence of indels in edited cells before (in vitro) or following transplant, in stark contrast to LV's non-targeted vector integration sites. Together, the improved efficiency and safety of IL2RG correction via CRISPR-Cas9-based TI approach provides a strong rationale for a clinical trial for treatment of XSCID patients.

Reshaping the Ventricle From Within: MIRTH (Myocardial Intramural Remodeling by Transvenous Tether) Ventriculoplasty in Swine

MIRTH (Myocardial Intramural Remodeling by Transvenous Tether) is a transcatheter ventricular remodeling procedure. A transvenous tension element is placed within the walls of the beating left ventricle and shortened to narrow chamber dimensions. MIRTH uses 2 new techniques: controlled intramyocardial guidewire navigation and EDEN (Electrocardiographic Radial Depth Navigation). MIRTH caused a sustained reduction in chamber dimensions in healthy swine. Midventricular implants approximated papillary muscles. MIRTH shortening improved myocardial contractility in cardiomyopathy in a dose-dependent manner up to a threshold beyond which additional shortening reduced performance. MIRTH may help treat dilated cardiomyopathy. Clinical investigation is warranted.

BSL2-compliant lethal mouse model of SARS-CoV-2 and variants of concern to evaluate therapeutics targeting the Spike protein

Since first reported in 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is rapidly acquiring mutations, particularly in the spike protein, that can modulate pathogenicity, transmission and antibody evasion leading to successive waves of COVID19 infections despite an unprecedented mass vaccination necessitating continuous adaptation of therapeutics. Small animal models can facilitate understanding host-pathogen interactions, target selection for therapeutic drugs, and vaccine development, but availability and cost of studies in BSL3 facilities hinder progress. To generate a BSL2-compatible in vivo system that specifically recapitulates spike protein mediated disease we used replication competent, GFP tagged, recombinant Vesicular Stomatitis Virus where the VSV glycoprotein was replaced by the SARS-CoV-2 spike protein (rVSV-SARS2-S). We show that infection requires hACE2 and challenge of neonatal but not adult, K18-hACE2 transgenic mice (hACE2tg) leads to productive infection of the lungs and brains. Although disease progression was faster in SARS-CoV-2 infected mice, infection with both viruses resulted in neuronal infection and encephalitis with increased expression of Interferon-stimulated Irf7, Bst2, Ifi294, as well as CxCL10, CCL5, CLC2, and LILRB4, and both models were uniformly lethal. Further, prophylactic treatment targeting the Spike protein (Receptor Binding Domain) with antibodies resulted in similar levels of protection from lethal infection against rVSV-SARS2-S and SARS-CoV-2 viruses. Strikingly, challenge of neonatal hACE2tg mice with SARS-CoV-2 Variants of Concern (SARS-CoV-2-α, -β, ϒ, or Δ) or the corresponding rVSV-SARS2-S viruses (rVSV-SARS2-Spike-α, rVSV-SARS2-Spike-β, rVSV-SARS2-Spike-ϒ or rVSV-SARS2-Spike-Δ) resulted in increased lethality, suggesting that the Spike protein plays a key role in determining the virulence of each variant. Thus, we propose that rVSV-SARS2-S virus can be used to understand the effect of changes to SARS-CoV-2 spike protein on infection and to evaluate existing or experimental therapeutics targeting spike protein of current or future VOC of SARS-CoV-2 under BSL-2 conditions.

Transcatheter Myotomy to Relieve Left Ventricular Outflow Tract Obstruction: The Septal Scoring Along the Midline Endocardium Procedure in Animals

BACKGROUND

Left ventricular outflow tract obstruction complicates hypertrophic cardiomyopathy and transcatheter mitral valve replacement. Septal reduction therapies including surgical myectomy and alcohol septal ablation are limited by surgical morbidity or coronary anatomy and high pacemaker rates, respectively. We developed a novel transcatheter procedure, mimicking surgical myotomy, called Septal Scoring Along the Midline Endocardium (SESAME).

METHODS

SESAME was performed in 5 naive pigs and 5 pigs with percutaneous aortic banding-induced left ventricular hypertrophy. Fluoroscopy and intracardiac echocardiography guided the procedures. Coronary guiding catheters and guidewires were used to mechanically enter the basal interventricular septum. Imparting a tip bend to the guidewire enabled intramyocardial navigation with multiple df. The guidewire trajectory determined the geometry of SESAME myotomy. The myocardium was lacerated using transcatheter electrosurgery. Cardiac function and tissue characteristics were assessed by cardiac magnetic resonance at baseline, postprocedure, and at 7- or 30-day follow-up.

RESULTS

SESAME myotomy along the intended trajectory was achieved in all animals. The myocardium splayed after laceration, increasing left ventricular outflow tract area (753 to 854 mm², P=0.008). Two naive pigs developed ventricular septal defects due to excessively deep lacerations in thin baseline septa. No hypertrophy model pig, with increased septal thickness and left ventricular mass compared with naive pigs, developed ventricular septal defects. One animal developed left axis deviation on ECG but no higher conduction block was seen in any animal. Coronary artery branches were intact on angiography with no infarction on cardiac magnetic resonance late gadolinium imaging. Cardiac magnetic resonance chamber volumes, function, flow, and global strain were preserved. No myocardial edema was evident on cardiac magnetic resonance T1 mapping.

CONCLUSIONS

This preclinical study demonstrated feasibility of SESAME, a novel transcatheter myotomy to relieve left ventricular outflow tract obstruction. This percutaneous procedure using available devices, with a safe surgical precedent, is readily translatable into patients.

Post-Transplantation Cyclophosphamide Uniquely Restrains Alloreactive CD4+ T-Cell Proliferation and Differentiation After Murine MHC-Haploidentical Hematopoietic Cell Transplantation

Post-transplantation cyclophosphamide (PTCy) reduces the incidence and severity of graft-versus-host disease (GVHD), thereby improving the safety and accessibility of allogeneic hematopoietic cell transplantation (HCT). We have shown that PTCy works by inducing functional impairment and suppression of alloreactive T cells. We also have identified that reduced proliferation of alloreactive CD4⁺ T cells at day +7 and preferential recovery of CD4⁺CD25⁺Foxp3⁺ regulatory T cells (T_regs) at day +21 are potential biomarkers associated with optimal PTCy dosing and timing in our B6C3F1→B6D2F1 MHC-haploidentical murine HCT model. To understand whether the effects of PTCy are unique and also to understand better the biology of GVHD prevention by PTCy, here we tested the relative impact of cyclophosphamide compared with five other optimally dosed chemotherapeutics (methotrexate, bendamustine, paclitaxel, vincristine, and cytarabine) that vary in mechanisms of action and drug resistance. Only cyclophosphamide, methotrexate, and cytarabine were effective in preventing fatal GVHD, but cyclophosphamide was superior in ameliorating both clinical and histopathological GVHD. Flow cytometric analyses of blood and spleens revealed that these three chemotherapeutics were distinct in constraining conventional T-cell numerical recovery and facilitating preferential T_reg recovery at day +21. However, cyclophosphamide was unique in consistently reducing proliferation and expression of the activation marker CD25 by alloreactive CD4⁺Foxp3^- conventional T cells at day +7. Furthermore, cyclophosphamide restrained the differentiation of alloreactive CD4⁺Foxp3^- conventional T cells at both days +7 and +21, whereas methotrexate and cytarabine only restrained differentiation at day +7. No chemotherapeutic selectively eliminated alloreactive T cells. These data suggest that constrained alloreactive CD4⁺Foxp3^- conventional T-cell numerical recovery and associated preferential CD4⁺CD25⁺Foxp3⁺ T_reg reconstitution at day +21 may be potential biomarkers of effective GVHD prevention. Additionally, these results reveal that PTCy uniquely restrains alloreactive CD4⁺Foxp3^- conventional T-cell proliferation and differentiation, which may explain the superior effects of PTCy in preventing GVHD. Further study is needed to determine whether these findings also hold true in clinical HCT.

NK cells require immune checkpoint receptor LILRB4/gp49B to control neurotropic Zika virus infections in mice

Immune cells express an array of inhibitory checkpoint receptors that are upregulated upon activation and limit tissue damage associated with excessive response to pathogens or allergens. Mouse leukocyte immunoglobulin like receptor B4 (LILRB4), also known as glycoprotein 49B (gp49B), is an inhibitory checkpoint receptor constitutively expressed in myeloid cells and upregulated in B cells, T cells, and NK cells upon activation. Here, we report that expression of LILRB4, which binds Zika virus (ZIKV), was increased in microglia and myeloid cells infiltrating the brains of neonatal mice with ZIKV-associated meningoencephalitis. Importantly, while C57BL/6 mice developed transient neurological symptoms but survived infection, mice lacking LILRB4/gp49B (LILRB4 KO) exhibited more severe signs of neurological disease and succumbed to disease. Their brains showed increased cellular infiltration but reduced control of viral burden. The reduced viral clearance was associated with altered NK cell function in the absence of LILRB4/gp49B. In naive animals, this manifested as reduced granzyme B responses to stimulation, but in ZIKV-infected animals, NK cells showed phenotypic changes that suggested altered maturation, diminished glucose consumption, reduced IFN-γ and granzyme B production, and impaired cytotoxicity. Together, our data reveal LILRB4/gp49B as an important regulator of NK cell function during viral infections.

Genetic reduction of mTOR extends lifespan in a mouse model of Hutchinson-Gilford Progeria syndrome

Hutchinson-Gilford progeria syndrome (HGPS) is a rare accelerated aging disorder most notably characterized by cardiovascular disease and premature death from myocardial infarction or stroke. The majority of cases are caused by a de novo single nucleotide mutation in the LMNA gene that activates a cryptic splice donor site, resulting in production of a toxic form of lamin A with a 50 amino acid internal deletion, termed progerin. We previously reported the generation of a transgenic murine model of progeria carrying a human BAC harboring the common mutation, G608G, which in the single-copy state develops features of HGPS that are limited to the vascular system. Here, we report the phenotype of mice bred to carry two copies of the BAC, which more completely recapitulate the phenotypic features of HGPS in skin, adipose, skeletal, and vascular tissues. We further show that genetic reduction of the mechanistic target of rapamycin (mTOR) significantly extends lifespan in these mice, providing a rationale for pharmacologic inhibition of the mTOR pathway in the treatment of HGPS.

Perforin-deficient CAR T cells recapitulate late-onset inflammatory toxicities observed in patients

Late-onset inflammatory toxicities resembling hemophagocytic lymphohistiocytosis (HLH) or macrophage activation syndrome (MAS) occur after chimeric antigen receptor T cell (CAR T cell) infusion and represent a therapeutic challenge. Given the established link between perforin deficiency and primary HLH, we investigated the role of perforin in anti-CD19 CAR T cell efficacy and HLH-like toxicities in a syngeneic murine model. Perforin contributed to both CD8+ and CD4+ CAR T cell cytotoxicity but was not required for in vitro or in vivo leukemia clearance. Upon CAR-mediated in vitro activation, perforin-deficient CAR T cells produced higher amounts of proinflammatory cytokines compared with WT CAR T cells. Following in vivo clearance of leukemia, perforin-deficient CAR T cells reexpanded, resulting in splenomegaly with disruption of normal splenic architecture and the presence of hemophagocytes, which are findings reminiscent of HLH. Notably, a substantial fraction of patients who received anti-CD22 CAR T cells also experienced biphasic inflammation, with the second phase occurring after the resolution of cytokine release syndrome, resembling clinical manifestations of HLH. Elevated inflammatory cytokines such as IL-1β and IL-18 and concurrent late CAR T cell expansion characterized the HLH-like syndromes occurring in the murine model and in humans. Thus, a murine model of perforin-deficient CAR T cells recapitulated late-onset inflammatory toxicities occurring in human CAR T cell recipients, providing therapeutically relevant mechanistic insights.

Optimized Timing of Post-Transplantation Cyclophosphamide in MHC-Haploidentical Murine Hematopoietic Cell Transplantation

Post-transplantation cyclophosphamide (PTCy) reduces the risks of severe acute and chronic graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation (HCT). Yet, the standard clinical dose and timing of PTCy were partly extrapolated from MHC-matched skin allografting models and were partly empirical. Here we investigated the impact of differential dosing and timing of PTCy on its efficacy in preventing GVHD in a murine MHC-haploidentical HCT model. Administration of PTCy on days +3/+4 was superior to administration on days +1/+2, +5/+6, or +7/+8, whereas low-dose (10 mg/kg/day) PTCy on days +1/+2 actually led to accelerated death. Although the optimal timing of PTCy dosing was day +2 or +3 in the skin allografting models, in our MHC-haploidentical HCT model, PTCy on days +2/+3 was inferior to PTCy on days +3/+4 at lower doses. PTCy administered on days +3/+4, +4/+5, or +3/+5 were similarly efficacious. Single-day versus 2-day dosing schedules demonstrated that PTCy is maximally effective when given on day +4. Flow cytometric analysis showed that optimal PTCy dosing schedules both decreased alloreactive CD4⁺CD25^-Foxp3^- T cell proliferation at day +7 and allowed preferential CD4⁺CD25⁺Foxp3⁺ T cell reconstitution at day +21, suggesting that this combination may be a potential predictive biomarker of successful GVHD prevention by PTCy. These results show that the dose, timing, and cumulative exposure of PTCy all are critical for its efficacy in preventing GVHD. We are currently investigating the clinical relevance of these findings in a protocol seeking to optimize PTCy dose and timing and test these T cell endpoints as candidate biomarkers of successful GVHD prevention by PTCy.

Post-transplantation cyclophosphamide prevents graft-versus-host disease by inducing alloreactive T cell dysfunction and suppression

Post-transplantation cyclophosphamide (PTCy) recently has had a marked impact on human allogeneic hematopoietic cell transplantation (HCT). Yet, our understanding of how PTCy prevents graft-versus-host disease (GVHD) largely has been extrapolated from major histocompatibility complex (MHC)-matched murine skin allografting models that were highly contextual in their efficacy. Herein, we developed a T-cell-replete, MHC-haploidentical, murine HCT model (B6C3F1→B6D2F1) to test the putative underlying mechanisms: alloreactive T-cell elimination, alloreactive T-cell intrathymic clonal deletion, and suppressor T-cell induction. In this model and confirmed in four others, PTCy did not eliminate alloreactive T cells identified using either specific Vβs or the 2C or 4C T-cell receptors. Furthermore, the thymus was not necessary for PTCy's efficacy. Rather, PTCy induced alloreactive T-cell functional impairment which was supported by highly active suppressive mechanisms established within one day after PTCy that were sufficient to prevent new donor T cells from causing GVHD. These suppressive mechanisms included the rapid, preferential recovery of CD4+CD25+Foxp3+ regulatory T cells, including those that were alloantigen-specific, which served an increasingly critical function over time. Our results prompt a paradigm-shift in our mechanistic understanding of PTCy. These results have direct clinical implications for understanding tolerance induction and for rationally developing novel strategies to improve patient outcomes.

Targeting Epidermal Growth Factor Receptor (EGFR) and Human Epidermal Growth Factor Receptor 2 (HER2) Expressing Bladder Cancer Using Combination Photoimmunotherapy (PIT)

Bladder cancer (BC) is heterogeneous and expresses various cell surface targets. Photoimmunotherapy (PIT) involves monoclonal antibodies (MAbs) conjugated to a photoabsorber (PA), IR Dye 700Dx, and then activated by near infra-red light (NIR) to specifically target tumors. We have demonstrated that tumors expressing EGFR can be targeted with PIT. However, PIT may be less effective when a tumor lacks “overwhelming” expression of a single target such as EGFR. We present a combinatorial PIT approach for targeting BC expressing EGFR and HER2, using PA- labeled panitumumab (pan) and trastuzumab (tra), respectively. Human BC tissues and cell lines were analyzed for EGFR and HER2 expression. Efficacy of PA-labeled MAbs singly and in combination was analyzed. About 45% of BC tissues stain for both EGFR and HER2. In vitro, the combination of pan IR700 and tra IR700 with NIR was more efficacious than either agent alone. Tumor xenografts treated with combination PIT showed significant tumor growth retardation. Combination PIT is a promising approach for treating BC with low/moderate expression of surface receptors. In addition, given the molecular heterogeneity of bladder cancer, targeting more than one surface receptor may allow for more effective cell death across different bladder tumors.

PD-1 Inhibitory Receptor Downregulates Asparaginyl Endopeptidase and Maintains Foxp3 Transcription Factor Stability in Induced Regulatory T Cells

CD4⁺ T cell differentiation into multiple T helper (Th) cell lineages is critical for optimal adaptive immune responses. This report identifies an intrinsic mechanism by which programmed death-1 receptor (PD-1) signaling imparted regulatory phenotype to Foxp3⁺ Th1 cells (denoted as Tbet⁺iTreg_PDL1 cells) and inducible regulatory T (iTreg) cells. Tbet⁺iTreg_PDL1 cells prevented inflammation in murine models of experimental colitis and experimental graft versus host disease (GvHD). Programmed death ligand-1 (PDL-1) binding to PD-1 imparted regulatory function to Tbet⁺iTreg_PDL1 cells and iTreg cells by specifically downregulating endo-lysosomal protease asparaginyl endopeptidase (AEP). AEP regulated Foxp3 stability and blocking AEP imparted regulatory function in Tbet⁺iTreg cells. Also, Aep^-/- iTreg cells significantly inhibited GvHD and maintained Foxp3 expression. PD-1-mediated Foxp3 maintenance in Tbet⁺ Th1 cells occurred both in tumor infiltrating lymphocytes (TILs) and during chronic viral infection. Collectively, this report has identified an intrinsic function for PD-1 in maintaining Foxp3 through proteolytic pathway.

Translational repression of HIF2α expression in mice with Chuvash polycythemia reverses polycythemia

Chuvash polycythemia is an inherited disease caused by a homozygous germline VHLR200W mutation, which leads to impaired degradation of HIF2α, elevated levels of serum erythropoietin, and erythrocytosis/polycythemia. This phenotype is recapitulated by a mouse model bearing a homozygous VhlR200W mutation. We previously showed that iron-regulatory protein 1-knockout (Irp1-knockout) mice developed erythrocytosis/polycythemia through translational derepression of Hif2α, suggesting that IRP1 could be a therapeutic target to treat Chuvash polycythemia. Here, we fed VhlR200W mice supplemented with Tempol, a small, stable nitroxide molecule and observed that Tempol decreased erythropoietin production, corrected splenomegaly, normalized hematocrit levels, and increased the lifespans of these mice. We attribute the reversal of erythrocytosis/polycythemia to translational repression of Hif2α expression by Tempol-mediated increases in the IRE-binding activity of Irp1, as reversal of polycythemia was abrogated in VhlR200W mice in which Irp1 was genetically ablated. Thus, a new approach to the treatment of patients with Chuvash polycythemia may include dietary supplementation of Tempol, which decreased Hif2α expression and markedly reduced life-threatening erythrocytosis/polycythemia in the VhlR200W mice.

In vivo kinetics and nonradioactive imaging of rapidly proliferating cells in graft-versus-host disease

Hematopoietic stem cell transplantation (HSCT) offers a cure for cancers that are refractory to chemotherapy and radiation. Most HSCT recipients develop chronic graft-versus-host disease (cGVHD), a systemic alloimmune attack on host organs. Diagnosis is based on clinical signs and symptoms, as biopsies are risky. T cells are central to the biology of cGVHD. We found that a low Treg/CD4+ T effector memory (Tem) ratio in circulation, lymphoid, and target organs identified early and established mouse cGVHD. Using deuterated water labeling to measure multicompartment in vivo kinetics of these subsets, we show robust Tem and Treg proliferation in lymphoid and target organs, while Tregs undergo apoptosis in target organs. Since deuterium enrichment into DNA serves as a proxy for cell proliferation, we developed a whole-body clinically relevant deuterium MRI approach to nonradioactively detect cGVHD and potentially allow imaging of other diseases characterized by rapidly proliferating cells.

Tbet is a critical modulator of FoxP3 expression in autoimmune graft-versus-host disease

CD4⁺ T-helper subsets drive autoimmune chronic graft-versus-host disease, a major complication after allogeneic bone marrow transplantation. However, it remains unclear how specific T-helper subsets contribute to chronic graft-versus-host disease. T-helper type 1 cells are one of the major disease-mediating T-cell subsets and require interferon-γ signaling and Tbet expression for their function. Regulatory T cells on the other hand can inhibit T-helper type 1 cell-mediated responses. Using an established murine model that isolates the autoimmune component of graft-versus-host disease, we hypothesized that T-helper type 1 cells would restrict FoxP3-driven regulatory T cells. Upon transfer into immune-deficient syngeneic hosts, alloreactive Tbx21^−/−CD4⁺ T cells led to marked increases in FoxP3⁺ cells and reduced clinical evidence of autoimmunity. To evaluate whether peripheral induction contributed to regulatory T-cell predominance, we adoptively transferred Tbx21^−/− T cells that consisted of fate mapping for FoxP3: recipients of flow-purified effector cells that were Foxp3⁻ and Tbx21^−/− had enhanced T-regulatory-cell predominance during autoimmune graft-versus-host disease. These data directly demonstrated that peripheral T-regulatory-cell induction was inhibited by Tbet. Finally, Tbx21^−/− T-regulatory cells cross-regulated autoimmune wild-type T-effector-cell cytokine production in vivo. The Tbet pathway therefore directly impairs T-regulatory-cell reconstitution and is consequently a feasible target in efforts to prevent autoimmune graft-versus-host disease.

Transcatheter Myocardial Needle Chemoablation During Real-Time Magnetic Resonance Imaging: A New Approach to Ablation Therapy for Rhythm Disorders

BACKGROUND

Radiofrequency ablation for ventricular arrhythmias is limited by inability to visualize tissue destruction, by reversible conduction block resulting from edema surrounding lesions, and by insufficient lesion depth. We hypothesized that transcatheter needle injection of caustic agents doped with gadolinium contrast under real-time magnetic resonance imaging (MRI) could achieve deep, targeted, and irreversible myocardial ablation, which would be immediately visible.

METHODS AND RESULTS

Under real-time MRI guidance, ethanol or acetic acid was injected into the myocardium of 8 swine using MRI-conspicuous needle catheters. Chemoablation lesions had identical geometry by in vivo and ex vivo MRI and histopathology, both immediately and after 12 (7-17) days. Ethanol caused stellate lesions with patchy areas of normal myocardium, whereas acetic acid caused homogeneous circumscribed lesions of irreversible necrosis. Ischemic cardiomyopathy was created in 10 additional swine by subselective transcoronary ethanol administration into noncontiguous territories. After 12 (8-15) days, real-time MRI-guided chemoablation-with 2 to 5 injections to create a linear lesion-successfully eliminated the isthmus and local abnormal voltage activities.

CONCLUSIONS

Real-time MRI-guided chemoablation with acetic acid enabled the intended arrhythmic substrate, whether deep or superficial, to be visualized immediately and ablated irreversibly. In an animal model of ischemic cardiomyopathy, obliteration of a conductive isthmus both anatomically and functionally and abolition of local abnormal voltage activities in areas of heterogeneous scar were feasible. This represents the first report of MRI-guided myocardial chemoablation, an approach that could improve the efficacy of arrhythmic substrate ablation in the thick ventricular myocardium.

Bone marrow-derived mesenchymal stromal cells harness purinergenic signaling to tolerize human Th1 cells in vivo

The use of bone marrow-derived mesenchymal stromal cells (BMSC) in the treatment of alloimmune and autoimmune conditions has generated much interest, yet an understanding of the therapeutic mechanism remains elusive. We therefore explored immune modulation by a clinical-grade BMSC product in a model of human-into-mouse xenogeneic graft-versus-host disease (x-GVHD) mediated by human CD4(+) Th1 cells. BMSC reversed established, lethal x-GVHD through marked inhibition of Th1 cell effector function. Gene marking studies indicated BMSC engraftment was limited to the lung; furthermore, there was no increase in regulatory T cells, thereby suggesting a paracrine mechanism of BMSC action. BMSC recipients had increased serum CD73 expressing exosomes that promoted adenosine accumulation ex vivo. Importantly, immune modulation mediated by BMSC was fully abrogated by pharmacologic therapy with an adenosine A2A receptor antagonist. To investigate the potential clinical relevance of these mechanistic findings, patient serum samples collected pre- and post-BMSC treatment were studied for exosome content: CD73 expressing exosomes promoting adenosine accumulation were detected in post-BMSC samples. In conclusion, BMSC effectively modulate experimental GVHD through a paracrine mechanism that promotes adenosine-based immune suppression.

Fusion of lysosomes with secretory organelles leads to uncontrolled exocytosis in the lysosomal storage disease mucolipidosis type IV

Mutations in TRPML1 cause the lysosomal storage disease mucolipidosis type IV (MLIV). The role of TRPML1 in cell function and how the mutations cause the disease are not well understood. Most studies focus on the role of TRPML1 in constitutive membrane trafficking to and from the lysosomes. However, this cannot explain impaired neuromuscular and secretory cells' functions that mediate regulated exocytosis. Here, we analyzed several forms of regulated exocytosis in a mouse model of MLIV and, opposite to expectations, we found enhanced exocytosis in secretory glands due to enlargement of secretory granules in part due to fusion with lysosomes. Preliminary exploration of synaptic vesicle size, spontaneous mEPSCs, and glutamate secretion in neurons provided further evidence for enhanced exocytosis that was rescued by re-expression of TRPML1 in neurons. These features were not observed in Niemann-Pick type C1. These findings suggest that TRPML1 may guard against pathological fusion of lysosomes with secretory organelles and suggest a new approach toward developing treatment for MLIV.

Type I IFN Induction via Poly-ICLC Protects Mice against Cryptococcosis

Cryptococcus neoformans is the most common cause of fungal meningoencephalitis in AIDS patients. Depletion of CD4 cells, such as occurs during advanced AIDS, is known to be a critical risk factor for developing cryptococcosis. However, the role of HIV-induced innate inflammation in susceptibility to cryptococcosis has not been evaluated. Thus, we sought to determine the role of Type I IFN induction in host defense against cryptococci by treatment of C. neoformans (H99) infected mice with poly-ICLC (pICLC), a dsRNA virus mimic. Unexpectedly, pICLC treatment greatly extended survival of infected mice and reduced fungal burdens in the brain. Protection from cryptococcosis by pICLC-induced Type I IFN was mediated by MDA5 rather than TLR3. PICLC treatment induced a large, rapid and sustained influx of neutrophils and Ly6Chigh monocytes into the lung while suppressing the development of eosinophilia. The pICLC-mediated protection against H99 was CD4 T cell dependent and analysis of CD4 T cell polyfunctionality showed a reduction in IL-5 producing CD4 T cells, marginal increases in Th1 cells and dramatic increases in RORγt+ Th17 cells in pICLC treated mice. Moreover, the protective effect of pICLC against H99 was diminished in IFNγ KO mice and by IL-17A neutralization with blocking mAbs. Furthermore, pICLC treatment also significantly extended survival of C. gattii infected mice with reduced fungal loads in the lungs. These data demonstrate that induction of type I IFN dramatically improves host resistance against the etiologic agents of cryptococcosis by beneficial alterations in both innate and adaptive immune responses.

Passive transfer of modest titers of potent and broadly neutralizing anti-HIV monoclonal antibodies block SHIV infection in macaques

Five potent and broadly anti-HIV neutralizing monoclonal antibodies are able to block infection by two different SHIVs in monkeys. The authors show that antibodies targeting the outer glycan coat were the most effective and determined that titers of roughly 1:100 protected half the animals.

It is widely appreciated that effective human vaccines directed against viral pathogens elicit neutralizing antibodies (NAbs). The passive transfer of anti–HIV-1 NAbs conferring sterilizing immunity to macaques has been used to determine the plasma neutralization titers, which must be present at the time of exposure, to prevent acquisition of SIV/HIV chimeric virus (SHIV) infections. We administered five recently isolated potent and broadly acting anti-HIV neutralizing monoclonal antibodies (mAbs) to rhesus macaques and challenged them intrarectally 24 h later with either of two different R5-tropic SHIVs. By combining the results obtained from 60 challenged animals, we determined that the protective neutralization titer in plasma preventing virus infection in 50% of the exposed monkeys was relatively modest (∼1:100) and potentially achievable by vaccination.

Thymic medullary epithelium and thymocyte self-tolerance require cooperation between CD28-CD80/86 and CD40-CD40L costimulatory pathways

A critical process during thymic development of the T cell repertoire is the induction of self-tolerance. Tolerance in developing T cells is highly dependent on medullary thymic epithelial cells (mTEC), and mTEC development in turn requires signals from mature single-positive thymocytes, a bidirectional relationship termed thymus crosstalk. We show that CD28-CD80/86 and CD40-CD40L costimulatory interactions, which mediate negative selection and self-tolerance, upregulate expression of LTα, LTβ, and receptor activator for NF-κB in the thymus and are necessary for medullary development. Combined absence of CD28-CD80/86 and CD40-CD40L results in profound deficiency in mTEC development comparable to that observed in the absence of single-positive thymocytes. This requirement for costimulatory signaling is maintained even in a TCR transgenic model of high-affinity TCR-ligand interactions. CD4 thymocytes maturing in the altered thymic epithelial environment of CD40/CD80/86 knockout mice are highly autoreactive in vitro and are lethal in congenic adoptive transfer in vivo, demonstrating a critical role for these costimulatory pathways in self-tolerance as well as thymic epithelial development. These findings demonstrate that cooperativity between CD28-CD80/86 and CD40-CD40L pathways is required for normal medullary epithelium and for maintenance of self-tolerance in thymocyte development.

Transthoracic delivery of large devices into the left ventricle through the right ventricle and interventricular septum: preclinical feasibility

BACKGROUND

We aim to deliver large appliances into the left ventricle through the right ventricle and across the interventricular septum. This transthoracic access route exploits immediate recoil of the septum, and lower transmyocardial pressure gradient across the right versus left ventricular free wall. The route may enhance safety and allow subxiphoid rather than intercostal traversal.

METHODS

The entire procedure was performed under real-time CMR guidance. An "active" CMR needle crossed the chest, right ventricular free wall, and then the interventricular septum to deliver a guidewire then used to deliver an 18Fr introducer. Afterwards, the right ventricular free wall was closed with a nitinol occluder. Immediate closure and late healing of the unrepaired septum and free wall were assessed by oximetry, angiography, CMR, and necropsy up to four weeks afterwards.

RESULTS

The procedure was successful in 9 of 11 pigs. One failed because of refractory ventricular fibrillation upon needle entry, and the other because of inadequate guidewire support. In all ten attempts, the right ventricular free wall was closed without hemopericardium. There was neither immediate nor late shunt on oximetry, X-ray angiography, or CMR. The interventricular septal tract fibrosed completely. Transventricular trajectories planned on human CT scans suggest comparable intracavitary working space and less acute entry angles than a conventional atrial transseptal approach.

CONCLUSION

Large closed-chest access ports can be introduced across the right ventricular free wall and interventricular septum into the left ventricle. The septum recoils immediately and heals completely without repair. A nitinol occluder immediately seals the right ventricular wall. The entry angle is more favorable to introduce, for example, prosthetic mitral valves than a conventional atrial transseptal approach.

BCL2A1a over-expression in murine hematopoietic stem and progenitor cells decreases apoptosis and results in hematopoietic transformation

We previously reported the development of a lethal myeloid sarcoma in a non-human primate model utilizing retroviral vectors to genetically modify hematopoietic stem and progenitor cells. This leukemia was characterized by insertion of the vector provirus into the BCL2A1 gene, with resultant BCL2A1 over-expression. There is little information on the role of this anti-apoptotic member of the BCL2 family in hematopoiesis or leukemia induction. Therefore we studied the impact of Bcl2a1a lentiviral over-expression on murine hematopoietic stem and progenitor cells. We demonstrated the anti-apoptotic function of this protein in hematopoietic cells, but did not detect any impact of Bcl2a1a on in vitro cell growth or cell cycle kinetics. In vivo, we showed a higher propensity of HSCs over-expressing Bcl2a1a to engraft and contribute to hematopoiesis. Mice over-expressing Bcl2a1a in the hematologic compartment eventually developed an aggressive malignant disease characterized as a leukemia/lymphoma of B-cell origin. Secondary transplants carried out to investigate the primitive origin of the disease revealed the leukemia was transplantable. Thus, Bcl2a1 should be considered as a proto-oncogene with a potential role in both lymphoid and myeloid leukemogenesis, and a concerning site for insertional activation by integrating retroviral vectors utilized in hematopoietic stem cell gene therapy.

B-cell depletion extends the survival of GTKO.hCD46Tg pig heart xenografts in baboons for up to 8 months

Xenotransplantation of genetically modified pig organs offers great potential to address the shortage of human organs for allotransplantation. Rejection in Gal knockout (GTKO) pigs due to elicited non-Gal antibody response required further genetic modifications of donor pigs and better control of the B-cell response to xenoantigens. We report significant prolongation of heterotopic alpha Galactosyl transferase "knock-out" and human CD46 transgenic (GTKO.hCD46Tg) pig cardiac xenografts survival in specific pathogen free baboons. Peritransplant B-cell depletion using 4 weekly doses of anti-CD20 antibody in the context of an established ATG, anti-CD154 and MMF-based immunosuppressive regimen prolonged GTKO.hCD46Tg graft survival for up to 236 days (n = 9, median survival 71 days and mean survival 94 days). B-cell depletion persisted for over 2 months, and elicited anti-non-Gal antibody production remained suppressed for the duration of graft follow-up. This result identifies a critical role for B cells in the mechanisms of elicited anti-non-Gal antibody and delayed xenograft rejection. Model-related morbidity due to variety of causes was seen in these experiments, suggesting that further therapeutic interventions, including candidate genetic modifications of donor pigs, may be necessary to reduce late morbidity in this model to a clinically manageable level.

Surgical and nonsurgical complications of a pig to baboon heterotopic heart transplantation model

A modified immunosuppressive regimen, developed at the National Institutes of Health, has been employed in a large animal model of heterotopic cardiac xenotransplantation. Graft survival has been prolonged, but despite this, our recipients have succumbed to various surgical or nonsurgical complications. Herein, we have described different complications and management strategies. The most common complication was hypercoagulability (HC) after transplantation, causing thrombosis of both small and large vasculature, ultimately leading to graft loss. While managing this complication we discovered that there was a delicate balance between HC and consumptive coagulopathy (CC). CC encountered in some recipient baboons was not able to be reversed by stopping anticoagulation and administering multiple blood transfusions. Some complications had iatrogenic components. To monitor the animals, a solid state left ventricular telemetry probe was placed directly into the transplanted heart via the apex. Induction of hypocoagulable states by continuous heparin infusion led to uncontrollable intra-abdominal bleeding in 1 baboon from this apical site. This occurrence necessitated securing the probe more tightly with multiple purse strings and 4-quadrant pledgeted stay sutures. One instance of cardiac rupture originated from a lateral wall infarction site. Earlier studies have shown infections to be uniformly fatal in this transplant model. However, owing to the telemetry placement, infections were identified early by temperature spikes that were treated promptly with antibiotics. We had several cases of wound dehiscence due to recipients disrupting the suture line. These complications were promptly resolved by either re-approximating the wound or finding distractions for the baboon. A few of the most common problems we faced in our earlier experiments were related to the jacket, tether, and infusion pumps. It was difficult to keep the jackets on some baboons and the tether had to be modified several times before we assured long-term success. Infusion catheter replacement resulted in transplant heart venous obstruction and thrombosis from a right common femoral venous line. Homeostatic perturbations such as HC and CC and baboon-induced wound complications comprised most complications. Major bleeding and death due to telemetry implantation and infarct rupture occurred in 2 baboons. Despite the variety of complications, we achieved significant graft prolongation in this model.

Evaluation of a rapamycin-regulated serotype 2 adeno-associated viral vector in macaque parotid glands

OBJECTIVES

Salivary glands are useful target organs for local and systemic gene therapeutics. For such applications, the regulation of transgene expression is important. Previous studies by us in murine submandibular glands showed that a rapamycin transcriptional regulation system in a single serotype 2, adeno-associated viral (AAV2) vector was effective for this purpose. This study evaluated if such a vector was similarly useful in rhesus macaque parotid glands.

METHODS

A recombinant AAV2 vector (AAV-TF-RhEpo-2.3w), encoding rhesus erythropoietin (RhEpo) and a rapamycin-inducible promoter, was constructed. The vector was administered to macaques at either of two doses [1.5 x 10(11) (low dose) or 1.5 x 10(12) (high dose) vector genomes] via cannulation of Stensen's duct. Animals were followed up for 12-14 weeks and treated at intervals with rapamycin (0.1 or 0.5 mg kg(-1)) to induce gene expression. Serum chemistry, hematology, and RhEpo levels were measured at interval.

RESULTS

AAV-TF-RhEpo-2.3w administration led to low levels of rapamycin-inducible RhEpo expression in the serum of most macaques. In five animals, no significant changes were seen in serum chemistry and hematology values over the study. One macaque, however, developed pneumonia, became anemic and subsequently required euthanasia. After the onset of anemia, a single administration of rapamycin led to significant RhEpo production in this animal.

CONCLUSION

Administration of AAV-TF-RhEpo-2.3w to macaque parotid glands was generally safe, but led only to low levels of serum RhEpo in healthy animals following rapamycin treatment.

Amelanotic melanoma in a New Zealand White Rabbit (Oryctolagus cuniculus)

A 3.5-year-old intact male double-transgenic New Zealand white rabbit (Oryctolagus cuniculus), apoA-I and LCAT (apolipoprotein and lecithin:cholesterol acyltransferase), was presented with a discrete, raised facial mass (0.5 x 1.0 x 1.0 cm). The mass was surgically excised, with reoccurrence to the same site 88 days later. A second surgical excision was performed, and the rabbit died 3 weeks later from respiratory distress. At necropsy, multiple varying-sized masses were observed in the ventral mandibular region and throughout the lungs, pleura, and diaphragm. On histopathology, the masses were composed of moderately anisocytotic and anisokaryotic polygonal to spindloid cells with moderate finely granular, lightly eosinophilic cytoplasm, having round to oval nuclei with one to several nucleoli and finely stippled chromatin. Mitotic figures were frequent. Lymphatic and venous invasion were noted with neoplastic cells metastasized to the submandibular lymph nodes, lungs, liver, and adventitial surface of the aorta. Fontana-Masson stain was negative for melanin, thereby necessitating immunohistochemistry and transmission electron microscopy. Positive staining with MART-1 (a melanocyte protein marker) combined with transmission electron microscopy revealing type II melanosomes confirmed the diagnosis of an amelanotic melanoma.

Conditional overexpression of TGF-beta1 disrupts mouse salivary gland development and function

Transforming growth factor-beta (TGF-beta) signaling is known to affect salivary gland physiology by influencing branching morphogenesis, regulating ECM deposition, and controlling immune homeostasis. To study the role of TGF-beta1 in the salivary gland, we created a transgenic mouse (beta1(glo)) that conditionally overexpresses active TGF-beta1 upon genomic recombination by Cre recombinase. beta1(glo) mice were bred with an MMTV (mouse mammary tumor virus)-Cre (MC) transgenic line that expresses the Cre recombinase predominantly in the secretory cells of both the mammary and salivary glands. Although most of the double positive (beta1(glo)/MC) pups die either in utero or just after birth, clear defects in salivary gland morphogenesis such as reduced branching and increased mesenchyme could be seen. Those beta1(glo)/MC mice that survived into adulthood, however, had hyposalivation due to salivary gland fibrosis and acinar atrophy. Increased TGF-beta signaling was observed in the salivary gland with elevated phosphorylation of Smad2 and concomitant increase in ECM deposition. In particular, aberrant TGF-beta1 overexpression caused salivary gland hypofunction in this mouse model because of the replacement of normal glandular parenchyma with interstitial fibrous tissue. These results further implicate TGF-beta in pathological cases of salivary gland inflammation and fibrosis that occur with chronic infections in the glands or with the autoimmune disease, Sjögren's syndrome, or with radiation therapy given to head-and-neck cancer patients.

AAV5-mediated gene transfer to the parotid glands of non-human primates

Salivary glands are potentially useful target sites for multiple clinical applications of gene transfer. Previously, we have shown that serotype 2 adeno-associated viral (AAV2) vectors lead to stable gene transfer in the parotid glands of rhesus macaques. As AAV5 vectors result in considerably greater transgene expression in murine salivary glands than do AAV2 vectors, herein we have examined the use of AAV5 vectors in macaques at two different doses (n = 3 per group; 10(10) or 3 x 10(11) particles per gland). AAV5 vector delivery, as with AAV2 vectors, led to no untoward clinical, hematological or serum chemistry responses in macaques. The extent of AAV5-mediated expression of rhesus erythropoietin (RhEpo) was dose-dependent and similar to that seen with an AAV2 vector. However, unlike results with the AAV2 vector, AAV5 vector-mediated RhEpo expression was transient. Maximal expression peaked at day 56, was reduced by approximately 80% on day 84 and thereafter remained near background levels until day 182 (end of experiment). Quantitative PCR studies of high-dose vector biodistribution at this last time point showed much lower AAV5 copy numbers in the targeted parotid gland (approximately 1.7%) than found with the same AAV2 vector dose. Molecular analysis of the conformation of vector DNA indicated a markedly lower level of concatamerization for the AAV5 vector compared with that of a similar AAV2 vector. In addition, cellular immunological studies suggest that host response differences may occur with AAV2 and AAV5 vector delivery at this mucosal site. The aggregate data indicate that results with AAV5 vectors in murine salivary glands apparently do not extend to macaque glands.

Lymphocytes with aberrant expression of Fas or Fas ligand attenuate immune bone marrow failure in a mouse model

Bone marrow (BM) and lymphocyte samples from aplastic anemia patients show up-regulated Fas and Fas-ligand (FasL) expression, respectively, supporting a relationship between immune-mediated BM destruction and the Fas apoptotic pathway. Mice with spontaneous lymphoproliferation (lpr) and generalized lymphoproliferative disease (gld) mutations exhibit abnormal expression of Fas and FasL, serving as potential models to elucidate underlying mechanisms of BM failure. We examined cellular and functional characteristics of lpr and gld mutants on the C57BL/6 (B6) background. Lymph node (LN) cells from lpr and gld mice produced less apoptosis when coincubated with C.B10-H2(b)/LilMcd (C.B10) BM cells in vitro. This functional difference was confirmed by infusing lpr, gld, and B6 LN cells into sublethally irradiated CB10 mice. All donor LN cells showed significant T cell expansion and activation, but only B6 LN cells caused severe BM destruction. Mice infused with gld LN cells developed mild to moderate BM failure despite receiving FasL-deficient effectors, thus suggesting the existence of alternative pathways or incomplete penetrance of the mutation. Paradoxically, mice that received Fas-deficient lpr LN cells also had reduced BM failure, likely due to down-regulation of proapoptotic genes, an effect that can be overcome by higher doses of lpr LN cells. Our model demonstrates that abnormal Fas or FasL expression interferes with the development of pancytopenia and marrow hypoplasia, validating a major role for the Fas/FasL cytotoxic pathway in immune-mediated BM failure, although disruption of this pathway does not completely abolish marrow destruction.

Sustained improvement of spinal muscular atrophy mice treated with trichostatin a plus nutrition

Early treatment with the histone deacetylase inhibitor, trichostatin A, plus nutritional support extended median survival of spinal muscular atrophy mice by 170%. Treated mice continued to gain weight, maintained stable motor function, and retained intact neuromuscular junctions long after trichostatin A was discontinued. In many cases, ultimate decline of mice appeared to result from vascular necrosis, raising the possibility that vascular dysfunction is part of the clinical spectrum of severe spinal muscular atrophy. Early spinal muscular atrophy disease detection and treatment initiation combined with aggressive ancillary care may be integral to the optimization of histone deacetylase inhibitor treatment in human patients.

Enrichment of hematopoietic stem cells with SLAM and LSK markers for the detection of hematopoietic stem cell function in normal and Trp53 null mice

OBJECTIVE

To test function of hematopoietic stem cells (HSCs) in vivo in C57BL/6 (B6) and Trp53-deficient (Trp53 null) mice by using two HSC enrichment schemes.

MATERIALS AND METHODS

Bone marrow (BM) Lin-CD41-CD48-CD150+ (signaling lymphocyte activation molecules [SLAM]), Lin-CD41-CD48-CD150- (SLAM-) and Lin-Sca1+CD117+ (LSK) cells were defined by fluorescence-activated cell staining (FACS). Cellular reactive oxygen species (ROS) level was also analyzed by FACS. Sorted SLAM, SLAM-, and LSK cells were tested in vivo in the competitive repopulation (CR) and serial transplantation assays.

RESULTS

SLAM cell fraction was 0.0078%+/-0.0010% and 0.0135%+/-0.0010% of total BM cells in B6 and Trp53 null mice, and was highly correlated (R2=0.7116) with LSK cells. CD150+ BM cells also contained more ROSlow cells than did CD150- cells. B6 SLAM cells repopulated recipients much better than B6 SLAM- cells, showing high HSC enrichment. B6 SLAM cells also engrafted recipients better than Trp53 null SLAM cells in the CR and the follow-up serial transplantation assays. Similarly, LSK cells from B6 donors also had higher repopulating ability than those from Trp53 null donors. However, whole BM cells from the same B6 and Trp53 null donors showed the opposite functional trend in recipient engraftment.

CONCLUSION

Both SLAM and LSK marker sets can enrich HSCs from B6 and Trp53 mice. Deficiency of Trp53 upregulates HSC self-renewal but causes no gain of HSC function.

Peripheral edema with hypoalbuminemia in a nonhuman primate infected with simian-human immunodeficiency virus: a case report

A rhesus macaque (Macaca mulatta) infected with simian-human immunodeficiency virus (SHIV) while undergoing AIDS research, required a comprehensive physical examination when it presented with slight peripheral edema, hypoalbuminemia, and proteinuria. Many of the clinical findings were consistent with nephrotic syndrome, which is an indication of glomerular disease, but the possibility of concurrent disease needed to be considered because lentiviral induced immune deficiency disease manifests multiple clinical syndromes. The animal was euthanized when its condition deteriorated despite supportive care that included colloidal fluid therapy. Histopathology confirmed membranoproliferative glomerulonephritis, the result of immune complex deposition most likely due to chronic SHIV infection. Clinical symptoms associated with this histopathology in SHIV-infected macaques have not previously been described. Here we offer suggestions for the medical management of this condition, which entails inhibition of the renin-angiotensin-aldosterone system and diet modifications.

Minor antigen h60-mediated aplastic anemia is ameliorated by immunosuppression and the infusion of regulatory T cells

Human bone marrow (BM) failure mediated by the immune system can be modeled in mice. In the present study, infusion of lymph node (LN) cells from C57BL/6 mice into C.B10-H2(b)/LilMcd (C.B10) recipients that are mismatched at multiple minor histocompatibility Ags, including the immunodominant Ag H60, produced fatal aplastic anemia. Declining blood counts correlated with marked expansion and activation of CD8 T cells specific for the immunodominant minor histocompatibility Ag H60. Infusion of LN cells from H60-matched donors did not produce BM failure in C.B10 mice, whereas isolated H60-specific CTL were cytotoxic for normal C.B10 BM cells in vitro. Treatment with the immunosuppressive drug cyclosporine abolished H60-specific T cell expansion and rescued animals from fatal pancytopenia. The development of BM failure was associated with a significant increase in activated CD4+CD25+ T cells that did not express intracellular FoxP3, whereas inclusion of normal CD4+CD25+ regulatory T cells in combination with C57BL/6 LN cells aborted H60-specific T cell expansion and prevented BM destruction. Thus, a single minor histocompatibility Ag H60 mismatch can trigger an immune response leading to massive BM destruction. Immunosuppressive drug treatment or enhancement of regulatory T cell function abrogated this pathophysiology and protected animals from the development of BM failure.

Adeno-associated virus serotype 2-mediated gene transfer to the parotid glands of nonhuman primates

Salivary glands (SGs) are promising gene transfer targets with potential clinical applicability. Previous experiments in rodents using recombinant serotype 2 adeno-associated viral (rAAV2) vectors have demonstrated relatively stable transgene-encoded protein levels after SG gene transfer. In the present study, we examine direct SG administration of rAAV2 vectors encoding rhesus macaque erythropoietin (RhEPO) to the parotid glands of nonhuman primates using two different doses (n = 3 per group; 1 x 10(10) or 3 x 10(11) particles/gland, respectively). Gene transfer had no negative effects on general macaque physiology (e.g., weight, complete blood count, and serum chemistry). Macaques were euthanized 6 months after vector administration and complete necropsy and pathology assessments were performed, revealing no vector-related pathological lesions in any of the examined organs. In the high-dose group, RhEPO expression increased quickly (i.e., by week 1) and levels remained relatively stable both in serum and saliva until the end of the study. Serum-to-saliva ratios of RhEPO revealed secretion of the transgene product into the bloodstream, but not to the extent previously observed in mice. Furthermore, the kinetic results were not predicted by those observed in murine SGs. With respect to viral biodistribution, at necropsy vector was found overwhelmingly in the targeted parotid gland ( approximately 100 times more than levels in other tissues, most of which were similar to tissue levels in nontreated animals). We conclude that administration of modest doses of rAAV2 vectors to SGs for therapeutic purposes can be accomplished without significant or permanent injury to the targeted gland or to distant organs of nonhuman primates.

Resistance of Streptococcus gordonii to polymorphonuclear leukocyte killing is a potential virulence determinant of infective endocarditis

Significant differences in virulence among seven representative Streptococcus gordonii strains were observed by using the rat model of infective endocarditis. Five strains, including S. gordonii DL1, caused severe disease, while the other two strains, including S. gordonii SK12, caused minimal or no disease. The differences in virulence were evident from the visible presence of streptococci in the vegetations present on the aortic valves of catheterized rats that were challenged with individual strains and also from the much greater recovery of rifampin-resistant S. gordonii DLl than of streptomycin-resistant S. gordonii SK12 from the hearts of animals coinfected with both organisms. Each S. gordonii strain aggregated with human platelets and bound to polymorphonuclear leukocytes (PMNs), as shown by the stimulation of PMN superoxide anion production. These interactions were reduced or abolished by pretreatment of the platelets or PMNs with sialidase, indicating that there was bacterial recognition of host sialic acid-containing receptors. Adhesin-mediated binding of each S. gordonii strain to PMNs also triggered phagocytosis. However, the subsequent PMN-dependent killing differed significantly for the seven strains. The five virulent strains included three strains that were not killed and two strains whose numbers were reduced by approximately 50%. In contrast, the level of killing of each avirulent strain under the same conditions was significantly greater and approached 90% of the bacteria added. Parallel studies performed with rat PMNs revealed comparable differences in the resistance or susceptibility of representative virulent and avirulent strains. Thus, the ability of S. gordonii to survive in PMNs following adhesin-mediated phagocytosis may be an important virulence determinant of infective endocarditis.

Composite Tissue Allotransplantation: Development of a Preclinical Model in Nonhuman Primates

BACKGROUND

Composite tissue allotransplantation (CTA) has been recently introduced as a potential treatment for tissue loss secondary to burns, injuries, or resections. However, the optimal strategies to prevent CTA rejection remain undefined. Presently, no CTA model exists to evaluate human-specific immunosuppressants or the relative immunogenicity of all CTA tissues.

METHODS

We established a NHP CTA model utilizing a sensate osteomyocutaneous radial forearm flap that avoids functional impairment even in the case of graft loss. The model was evaluated in19 monkeys that underwent auto- or allotransplantation, with or without subtherapeutic immunosuppression to temporarily characterize rejection.

RESULTS

Autografts showed no evidence of rejection. Nonimmunosuppressed allografts were rapidly rejected showing a perivenular T-cell infiltrate. This was associated with subsequent alloantibody formation and led to graft thrombosis without prominent dermal infiltration. Subtherapeutically immunosuppressed animals also developed alloantibody and rejected in a delayed fashion exhibiting a marked dermal lymphocytic infiltrate similar in magnitude and distribution to previously reported human cases.

CONCLUSION

Our NHP model for CTA is well tolerated by NHPs, results in allosensitization, is responsive to immunosuppression, allows for the evaluation of CTA histology and can be used for the systematic preclinical evaluation of therapeutic maneuvers to improve allograft survival.

Optical-coherence tomography of a dense tissue: statistics of attenuation and backscattering

This paper addresses fundamental issues that underlie the interpretation of images acquired from turbid tissues by optical-coherence tomography (OCT). The attenuation and backscattering properties of freshly excised rat arteries and their dependence on the focusing and collection optics of the OCT system were measured at two wavelengths in the near infrared (830 nm and 1300 nm). Determined from the ratio of the magnitudes of the reflections from glass plates placed on both sides of the arteries, the mean attenuation coefficient of the arterial wall was found to be in the range 14 < microt < 22 mm(-1) at 830 nm and 11 < microt < 20 mm(-1) at 1300 nm. The measured values of microt were lowest for the longer source wavelength and for probe beams with the smallest average diameters. The observed dependence of microt on beam size indicates that relatively large-scale variations in the index of refraction of the tissue contributed to degradation of the tranverse spatial coherence of the beam. We introduce a framework for understanding and quantifying beam-size effects by way of the mutual-coherence function. The fact that spatial variations in backscattering and attenuation (which includes spatial-coherence losses) have similar effects on OCT signals makes the origin of the signals difficult to determine. Evidence is given that suggests that, in spite of this difficulty, certain features of microstructures embedded several hundred micrometres deep in a turbid tissue can still be detected and characterized.

Transforming growth factor-beta pathway serves as a primary tumor suppressor in CD8+ T cell tumorigenesis

Tumorigenesis in rodents, as well as in humans, has been shown to be a multistep process, with each step reflecting an altered gene product or gene regulatory process leading to autonomy of cell growth. Initial genetic mutations are often associated with dysfunctional growth regulation, as is demonstrated in several transgenic mouse models. These changes are often followed by alterations in tumor suppressor gene function, allowing unchecked cell cycle progression and, by genomic instability, additional genetic mutations responsible for tumor metastasis. Here we show that reduced transforming growth factor-beta signaling in T lymphocytes leads to a rapid expansion of a CD8+ memory T-cell population and a subsequent transformation to leukemia/lymphoma as shown by multiple criteria, including peripheral blood cell counts histology, T-cell receptor monoclonality, and host transferability. Furthermore, spectral karyotype analysis of the tumors shows that the tumors have various chromosomal aberrations. These results suggest that reduced transforming growth factor-beta signaling acts as a primary carcinogenic event, allowing uncontrolled proliferation with consequent accumulation of genetic defects and leukemic transformation.

CD3/CD28-costimulated T1 and T2 subsets: differential in vivo allosensitization generates distinct GVT and GVHD effects

Adoptive T-cell therapy using CD3/CD28 co-stimulation likely requires in vivo generation of antigen specificity. Because CD28 promotes TH1/TC1 (T1) or TH2/TC2 (T2) differentiation, costimulation may generate donor T1 or T2 cells capable of differentially mediating allogeneic graft-versus-tumor (GVT) effects and graft-versus-host disease (GVHD). Costimulation under T1 or T2 conditions indeed generated murine TH1/TC1 cells secreting interleukin-2/interferon-gamma (IL-2/IFN-gamma) or TH2/TC2 cells secreting IL-4/IL-5/IL-10. In vivo, allogeneic T1 cells expanded, maintained T1 secretion, and acquired allospecificity involving IFN-gamma and IL-5. In contrast, allogeneic T2 cells expanded less and maintained T2 secretion but did not develop significant allospecificity.Allogeneic, but not syngeneic, T1 cells mediated a GVT effect against host-type breast cancer cells, as median survival time (MST) increased from 25.6 +/- 2.6 (tumor controls) to 69.2 +/- 5.9 days (P < 1.2 x 10(-9)). This T1-associated GVT effect operated independently of fasL because T1 cells from gld mice mediated tumor-free survival. In contrast, allogeneic T2 cells mediated a modest, noncurative GVT effect (MST, 29 +/- 1.3 days; P <.0019). T1 recipients had moderate GVHD (histologic score, 4 of 12) that contributed to lethality after bone marrow transplantation; in contrast, T2 recipients had minimal GVHD (histologic score, 1 of 12). CD3/CD28 co-stimulation, therefore, generates T1 or T2 populations with differential in vivo capacity for expansion to alloantigen, resulting in differential GVT effects and GVHD.

Predisposition to arrhythmia and autonomic dysfunction in Nhlh1-deficient mice

Nhlh1 is a basic helix-loop-helix transcription factor whose expression is restricted to the nervous system and which may play a role in neuronal differentiation. To directly study Nhlh1 function, we generated null mice. Homozygous mutant mice were predisposed to premature, adult-onset, unexpected death. Electrocardiograms revealed decreased total heart rate variability, stress-induced arrhythmia, and impaired baroreceptor sensitivity. This predisposition to arrhythmia is a likely cause of the observed death in the mutant mice. Heterozygosity for the closely related transcription factor Nhlh2 increased the severity of the Nhlh1-null phenotype. No signs of primary cardiac structural or conduction abnormalities could be detected upon necropsy of the null mice. The pattern of altered heart rhythm observed in basal and experimental conditions (stress and pharmacologically induced) suggests that a deficient parasympathetic tone may contribute to the arrhythmia in the Nhlh1-null mouse. The expression of Nhlh1 in the developing brain stem and in the vagal nuclei in the wild-type mouse further supports this hypothesis. The Nhlh1 mutant mouse may thus provide a model to investigate the contribution of the autonomic nervous system to arrhythmogenesis.

Transforming growth factors-beta are not good biomarkers of chemopreventive efficacy in a preclinical breast cancer model system

Using a carcinogen-initiated rat model of mammary tumorigenesis, we tested the hypothesis that transforming growth factor (TGF)-betas are useful biomarkers of chemopreventive efficacy in the breast. The chemopreventive agents tested were tamoxifen and the retinoids 9-cis-retinoic acid (9cRA) and N-(4-hydroxyphenyl)retinamide (4-HPR), because both antiestrogens and retinoids have previously been shown to upregulate TGF-betas in vitro. Despite demonstrable chemopreventive efficacy in this model, none of these agents, alone or in combination, had any significant impact on the expression of TGF-betas in the mammary ductal epithelium or periductal stroma as determined by immunohistochemistry. These data suggest that TGF-betas are not likely to be useful biomarkers of chemopreventive efficacy in a clinical setting.

An immunoablative regimen of fludarabine and cyclophosphamide prevents fully MHC-mismatched murine marrow graft rejection independent of GVHD

The prevention of graft rejection in the setting of nonmyeloablative transplant approaches might be mediated by chemotherapy-induced host immunoablation and by the graft-promoting effects of graft-versus-host disease (GVHD). To evaluate whether host immunoablation alone might allow for alloengraftment, we developed an F1-into-parent murine marrow rejection model using host preparative regimens of lethal total body irradiation (TBI; 950 cGy), sublethal irradiation (600 cGy), or combinations of fludarabine (Flu) and cyclophosphamide (Cy). A preparative regimen selectivity index (SI) was calculated to determine whether host lymphocytes were preferentially depleted relative to myeloid cells (SI = number of host myeloid/number host T lymphoid cells remaining after preparative regimen administration). Saline-treated recipients were assigned an SI value of 1.0. Recipients of lethal TBI had reduced myeloid cells relative to T cells (SI = 0.6). In contrast, all Flu/Cy regimens preferentially depleted host T cells: recipients of Flu (100 mg/kg per day)/Cy (50 mg/kg per day) for 10 days (SI = 28.1); recipients of Flu (100 mg/kg per day)/Cy (100 mg/kg per day) for 10 days (SI = 64.1); and recipients of Flu (100 mg/kg per day)/Cy (50 mg/kg per day) for 19 or 27 days (SI = 74.6). The 10-day regimen of Flu/Cy (50 mg/kg per day) did not severely reduce host T cell numbers, nor did it prevent F1 marrow rejection (<1% chimerism, n = 14). In contrast, the 10-day regimen of Flu/Cy (100 mg/kg per day) reduced T-cell numbers below that of lethal TBI recipients and prevented F1 marrow rejection (11.4% chimerism, n = 15); donor chimerism was predominant in lymphoid cells and was stable through day 240 post-BMT. Additionally, the 19- or 27-day regimen of Flu/Cy, which most selectively depleted host T cells, also prevented F1 marrow rejection (6.3% chimerism, n = 15). These results therefore demonstrate that optimized Flu-containing, immunoablative preparative regimens can prevent fully MHC-disparate marrow rejection independent of GVHD.

Effects of energy-matched pulsed and continuous ultrasound on tumor growth in mice

BACKGROUND AND PURPOSE

A diagnosis of cancer is a contraindication for the use of therapeutic ultrasound (US). Continuous US applied to murine tumors has resulted in larger and heavier tumors compared with controls. We compared tumor growth using low-power continuous US and energy-matched pulsed US.

SUBJECTS

Female C57BL/6 mice (N = 174) were used.

METHODS

Animals received subcutaneous injections of methylcholanthrene tumor cells. The mice were randomly divided into three groups: 60 mice that received low-power continuous US for 5 minutes at 0.75 W/cm2 (LC US group), 63 mice that received pulsed US for 12.5 minutes at 1.5 W/cm2 (pulsed US group), and 51 mice that served as a control group. The LC and pulsed US groups received equal US energy. Both experimental groups received 10 treatments of 3-MHz US, which was applied directly over the tumor. The control group received identical handling but no US. After treatment, the tumors were excised, weighed, and measured. A one-way analysis of variance, followed by Newman-Keuls post hoc testing, was used to analyze the data.

RESULTS

Mean tumor weights (in grams) and volumes (in cubic millimeters) were 0.563 g and 564 mm3 for the LC US group, 0.560 g and 525 mm3 for the pulsed US group, and 0.516 g and 406 mm3 for the control group.

CONCLUSION AND DISCUSSION

Reducing total US energy will result in less growth of murine tumors. When infusing equal energy, continuous and pulsed US will produce similar effects on tumor growth.

Behavioral and Physical Concomitants of Congenital Hydrocephalus in a Rhesus Macaque (Macaca mulatta) Neonate

A colony-born male rhesus monkey neonate was assigned to an ongoing protocol assessing behavioral and physiologic development in nursery-reared infants. It was sacrificed at day 20 because of poor weight gain, inability to self-feed, and generalized weakness. An asymmetric internal hydrocephalus was the only notable gross finding at necropsy. A retrospective analysis was performed comparing physical and behavioral measures for it with values for age-matched nursery-reared peers. Weight gain and formula intake lagged behind others in its cohort. The affected macaque spent more time in sleep and awake/quiet states and less time in an awake active state than did its peers. Behaviors during a neonatal temperament/reflex examination were indicative of high levels of irritability, poor muscular tone, nonexistent voluntary motor activity, and slower overall responding. In addition, asymmetric responses for some motor items were observed. However, vestibular/ocular reflexes appeared normal. The occasional observation of hydrocephalus in infants, as well as its prevalence throughout the primate order, indicates that hydrocephalus should be considered in the differential diagnosis for infants with feeding difficulties and motor dysfunction.

Allospecific CD8+ Tc1 and Tc2 populations in graft-versus-leukemia effect and graft-versus-host disease

Allogeneic CD8+ T cells mediate both a graft-vs-leukemia (GVL) effect and graft-vs-host disease (GVHD). To evaluate whether CD8 cells of defined cytokine phenotype differentially mediate these processes, alloreactive donor CD8+ T cells preferentially secreting type I or type II cytokines were generated by alloantigenic priming in vitro in the presence of IL-12 or IL-4, respectively. Both cytokine-secreting subsets lysed allogeneic tumor targets in vitro ("Tc1" and "Tc2" subsets). A transplantation model was established (B6 into B6C3F1, 1050 cGy host irradiation) using the 32Dp210 myeloid line (bcr/abl transfected, H-2k; 1 x 10(4) tumor cells/recipient). Compared with leukemia controls (death at 12.9 days post-bone marrow transplantation), both Tc1 and Tc2 recipients were conferred a survival advantage. At cell doses of 2 to 2.5 x 10(7), the Tc1-mediated GVL effect (mean survival of 34.2 days) was more potent than the Tc2-mediated GVL effect (mean survival of 20.5 days; Tc1 > Tc2, p = 0.009). On day 15, histologic examination showed that Tc1 recipients had undetectable tumor burdens, whereas Tc2 recipients had extensive leukemic infiltrates. However, Tc2 recipients had essentially no histologic evidence of GVHD, whereas Tc1 recipients had mild to moderate GVHD (average GVHD scores of 1/40 and 9.3/40, respectively). In contrast, recipients of uncultured CD8+ donor T cells developed severe GVHD (average GVHD score of 26.7/40). Because in vitro-generated, alloreactive Tc1 and Tc2 populations mediated GVL with reduced GVHD, we conclude that both subsets may improve the therapeutic outcome of allogeneic T cell transfers in patients with leukemia.