Successful Extension of Vascularized Composite Allograft Perfusion Cold Storage to 24 h in a Rat Hindlimb Transplant Model

Background

Vascularized composite allograft transplantation is a treatment option for complex tissue injuries; however, ischemia reperfusion injury and high acute rejection rates remain a challenge. Hypothermic machine perfusion using acellular storage perfusate is a potential solution. This study evaluated the University of Wisconsin Kidney Preservation Solution-1 (KPS-1) compared with normal saline (NS) for preservation of donor rat hindlimbs subjected to 24 h of ex vivo perfusion cold storage.

Methods

Hindlimbs were subjected to 24-h perfusion cold storage with heparinized KPS-1 (n = 6) or heparinized NS (n = 6). Flow, resistance, and pH were measured continuously. At the end of the 24-h period, tissue was collected for histological analysis of edema and apoptosis.

Results

KPS-1 perfused limbs showed significantly less edema than the NS group, as evidenced by lower limb weight gain (P < 0.001) and less interfascicular space (P < 0.001). KPS-perfused muscle had significantly less cell death than NS-perfused muscle based on terminal deoxynucleotidyl transferase dUTP nick-end labeling (P < 0.001) and cleaved caspase-3 staining (P = 0.045). During hypothermic machine perfusion, a significant decrease in pH over time was detected in both groups, with a significantly greater decline in pH in the KPS-1 group than in the NS group. There were no significant differences overall and over time in flow rate or vascular resistance between the KPS and NS groups.

Conclusions

Perfusion with KPS-1 can successfully extend vascularized composite allograft perfusion cold storage for 24 h in a rat hindlimb model without significant edema or cell death.

Galectin-3 in biliary atresia and other pediatric cholestatic liver diseases

AIMS

Biliary atresia (BA) is characterized by intrahepatic inflammation and rapid progression of liver fibrosis. Galectin-3, a beta-galactoside binding protein, is a key regulator of inflammation and fibrosis. The aim of this study was to characterize circulating and hepatic Galectin-3 levels in children with BA.

METHODS

Plasma and liver samples were obtained from children with early BA at time of Kasai hepatoportoenterostomy, late BA at time of transplant, early and late other cholestatic liver diseases (CLD), and controls. Plasma Galectin-3 was measured using standard enzyme-linked immunoassay. Liver tissue was analyzed with multiplex immunohistochemistry and quantified using whole slide analysis. Statistical comparisons were made using nonparametric testing.

RESULTS

Plasma Galectin-3 in late BA was significantly higher than in early BA (20.82 [12.45-30.46] vs. 11.30 [8.74-16.83] ng/mL, p = 0.0096). Galectin-3 levels correlated with markers of disease severity and interleukin-6. There were significantly more Galectin-3+ M2 macrophages in late BA in comparison to late other CLD (162 [157-233] vs. 49 [33-59] cells/mm2, p = 0.03). The number of Galectin-3+ M2 macrophages correlated with the number of activated hepatic stellate cells and bile duct proliferation.

CONCLUSIONS

Plasma Galectin-3 is higher in late BA at time of transplant in comparison to early BA at time of Kasai. The number of Galectin-3 expressing M2 macrophages in late BA is elevated relative to late other CLD and was associated with other prognostic histological findings. Galectin-3 targeted therapy may be beneficial in slowing disease progression to cirrhosis in children with BA.

Development and in-vivo validation of a portable phosphorescence lifetime-based fiber-optic oxygen sensor

Oxygenation is a crucial indicator of tissue viability and function. Oxygen tension ([Formula: see text]), i.e. the amount of molecular oxygen present in the tissue is a direct result of supply (perfusion) and consumption. Thus, measurement of [Formula: see text] is an effective method to monitor tissue viability. However, tissue oximetry sensors commonly used in clinical practice instead rely on measuring oxygen saturation ([Formula: see text]), largely due to the lack of reliable, affordable [Formula: see text] sensing solutions. To address this issue we present a proof-of-concept design and validation of a low-cost, lifetime-based oxygen sensing fiber. The sensor consists of readily-available off-the shelf components such as a microcontroller, a light-emitting diode (LED), an avalanche photodiode (APD), a temperature sensor, as well as a bright in-house developed porphyrin molecule. The device was calibrated using a benchtop setup and evaluated in three in vivo animal models. Our findings show that the new device design in combination with the bright porphyrin has the potential to be a useful and accurate tool for measuring [Formula: see text] in tissue, while also highlighting some of the limitations and challenges of oxygen measurements in this context.

CD3e-immunotoxin spares CD62Llo Tregs and reshapes organ-specific T-cell composition by preferentially depleting CD3ehi T cells

CD3-epsilon(CD3e) immunotoxins (IT), a promising precision reagent for various clinical conditions requiring effective depletion of T cells, often shows limited treatment efficacy for largely unknown reasons. Tissue-resident T cells that persist in peripheral tissues have been shown to play pivotal roles in local and systemic immunity, as well as transplant rejection, autoimmunity and cancers. The impact of CD3e-IT treatment on these local cells, however, remains poorly understood. Here, using a new murine testing model, we demonstrate a substantial enrichment of tissue-resident Foxp3+ Tregs following CD3e-IT treatment. Differential surface expression of CD3e among T-cell subsets appears to be a main driver of Treg enrichment in CD3e-IT treatment. The surviving Tregs in CD3e-IT-treated mice were mostly the CD3e^dimCD62L^lo effector phenotype, but the levels of this phenotype markedly varied among different lymphoid and nonlymphoid organs. We also found notable variations in surface CD3e levels among tissue-resident T cells of different organs, and these variations drive CD3e-IT to uniquely reshape T-cell compositions in local organs. The functions of organs and anatomic locations (lymph nodes) also affected the efficacy of CD3e-IT. The multi-organ pharmacodynamics of CD3e-IT and potential treatment resistance mechanisms identified in this study may generate new opportunities to further improve this promising treatment.

Galectin-3 is overexpressed in advanced cirrhosis and predicts post-liver transplant infectious complications

BACKGROUND & AIMS

Patients with advanced cirrhosis often have immune dysfunction and are more susceptible to infections. Galectin-3 is a β-galactoside-binding lectin implicated in inflammation, immune regulation and liver fibrosis. We aim to investigate galectin-3 expression in advanced cirrhosis and its ability to predict post-transplant infectious complications.

METHODS

We collected sera and liver samples from 129 cirrhotic patients at the time of liver transplantation and from an external cohort of 37 patients with alcoholic liver disease including alcoholic hepatitis (AH) at the time of diagnosis. Galectin-3 was assessed by ELISA, real-time PCR, immunohistochemistry and RNA-seq. Receiver operating characteristic curves and Cox proportional-hazards regression analysis were performed to assess the predictive power of galectin-3 for disease severity and post-transplant infections.

RESULTS

Increased galectin-3 levels were found in advanced cirrhosis. Galectin-3 significantly correlated with disease severity parameters and inflammatory markers. Galectin-3 had significant discriminating power for compensated and advanced cirrhosis (AUC = 0.78/0.84, circulating/liver galectin-3; p < .01), and was even higher to discriminate severe AH (AUC = 0.95, p < .0001). Cox Proportional-hazard model showed that galectin-3, MELD-Na and the presence of SIRS predict the development of post-transplant infectious complications. Patients with circulating galectin-3 (>16.58 ng/ml) were at 2.19-fold 95% CI (1.12-4.29) increased risk, but when combined with MELD-Na > 20.0 and SIRS, the risk to develop post-transplant infectious complications, increased to 4.60, 95% CI (2.38-8.90).

CONCLUSION

Galectin-3 is a novel biological marker of active inflammation and disease severity that could be clinically useful alone or in combination with other scores to discriminate advanced cirrhosis and predict post-transplant infectious complications.

Comparison of CD3e Antibody and CD3e-sZAP Immunotoxin Treatment in Mice Identifies sZAP as the Main Driver of Vascular Leakage

Anti-CD3-epsilon (CD3e) monoclonal antibodies (mAbs) and CD3e immunotoxins (ITs) are promising targeted therapy options for various T-cell disorders. Despite significant advances in mAb and IT engineering, vascular leakage syndrome (VLS) remains a major dose-limiting toxicity for ITs and has been poorly characterized for recent "engineered" mAbs. This study undertakes a direct comparison of non-mitogenic CD3e-mAb (145-2C11 with Fc-silentTM murine IgG1: S-CD3e-mAb) and a new murine-version CD3e-IT (saporin-streptavidin (sZAP) conjugated with S-CD3e-mAb: S-CD3e-IT) and identifies their distinct toxicity profiles in mice. As expected, the two agents showed different modes of action on T cells, with S-CD3e-mAb inducing nearly complete modulation of CD3e on the cell surface, while S-CD3e-IT depleted the cells. S-CD3e-IT significantly increased the infiltration of polymorphonuclear leukocytes (PMNs) into the tissue parenchyma of the spleen and lungs, a sign of increased vascular permeability. By contrast, S-CD3e-mAbs-treated mice showed no notable signs of vascular leakage. Treatment with control ITs (sZAP conjugated with Fc-silent isotype antibodies) induced significant vascular leakage without causing T-cell deaths. These results demonstrate that the toxin portion of S-CD3e-IT, not the CD3e-binding portion (S-CD3e-mAb), is the main driver of vascular leakage, thus clarifying the molecular target for improving safety profiles in CD3e-IT therapy.

Galectin-3 as a potential prognostic biomarker of severe COVID-19 in SARS-CoV-2 infected patients

Severe COVID-19 is associated with a systemic hyperinflammatory response leading to acute respiratory distress syndrome (ARDS), multi-organ failure, and death. Galectin-3 is a ß-galactoside binding lectin known to drive neutrophil infiltration and the release of pro-inflammatory cytokines contributing to airway inflammation. Thus, we aimed to investigate the potential of galectin-3 as a biomarker of severe COVID-19 outcomes. We prospectively included 156 patients with RT-PCR confirmed COVID-19. A severe outcome was defined as the requirement of invasive mechanical ventilation (IMV) and/or in-hospital death. A non-severe outcome was defined as discharge without IMV requirement. We used receiver operating characteristic (ROC) and multivariable logistic regression analysis to determine the prognostic ability of serum galectin-3 for a severe outcome. Galectin-3 levels discriminated well between severe and non-severe outcomes and correlated with markers of COVID-19 severity, (CRP, NLR, D-dimer, and neutrophil count). Using a forward-stepwise logistic regression analysis we identified galectin-3 [odds ratio (OR) 3.68 (95% CI 1.47-9.20), p < 0.01] to be an independent predictor of severe outcome. Furthermore, galectin-3 in combination with CRP, albumin and CT pulmonary affection > 50%, had significantly improved ability to predict severe outcomes [AUC 0.85 (95% CI 0.79-0.91, p < 0.0001)]. Based on the evidence presented here, we recommend clinicians measure galectin-3 levels upon admission to facilitate allocation of appropriate resources in a timely manner to COVID-19 patients at highest risk of severe outcome.

Epstein-Barr Virus-Encoded BILF1 Orthologues From Porcine Lymphotropic Herpesviruses Display Common Molecular Functionality

Infection of immunosuppressed transplant patients with the human γ-herpesvirus Epstein-Barr virus (EBV) is associated with post-transplant lymphoproliferative disease (PTLD), an often fatal complication. Immunosuppressed miniature pigs infected with γ-herpesvirus porcine lymphotropic herpesvirus 1 (PLHV1) develop a similar disease, identifying pigs as a potential preclinical model for PTLD in humans. BILF1 is a G protein-coupled receptor (GPCR) encoded by EBV with constitutive activity linked to tumorigenesis and immunoevasive function downregulating MHC-I. In the present study, we compared BILF1-orthologues encoded by the three known PLHVs (PLHV1-3) with EBV-BILF1 to determine pharmacological suitability of BILF1 orthologues as model system to study EBV-BILF1 druggability. Cell surface localization, constitutive internalization, and MHC-I downregulation as well as membrane proximal constitutive Gα_i signaling patterns were conserved across all BILFs. Only subtle differences between the individual BILFs were observed in downstream transcription factor activation. Using Illumina sequencing, PLHV1 was observed in lymphatic tissue from PTLD-diseased, but not non-diseased pigs. Importantly, these tissues showed enhanced expression of PLHV1-BILF1 supporting its involvement in PTLD infection.

A systematic review of in vivo stretching regimens on inflammation and its relevance to translational yoga research

OBJECTIVE

To conduct a systematic review evaluating the impact of stretching on inflammation and its resolution using in vivo rodent models. Findings are evaluated for their potential to inform the design of clinical yoga studies to assess the impact of yogic stretching on inflammation and health.

METHODS

Studies were identified using four databases. Eligible publications included English original peer-reviewed articles between 1900-May 2020. Studies included those investigating the effect of different stretching techniques administered to a whole rodent model and evaluating at least one inflammatory outcome. Studies stretching the musculoskeletal and integumentary systems were considered. Two reviewers removed duplicates, screened abstracts, conducted full-text reviews, and assessed methodological quality.

RESULTS

Of 766 studies identified, 25 were included for synthesis. Seven (28%) studies had a high risk of bias in 3 out of 10 criteria. Experimental stretching protocols resulted in a continuum of inflammatory responses with therapeutic and injurious effects, which varied with a combination of three stretching parameters--duration, frequency, and intensity. Relative to injurious stretching, therapeutic stretching featured longer-term stretching protocols. Evidence of pro- and mixed-inflammatory effects of stretching was found in 16 muscle studies. Evidence of pro-, anti-, and mixed-inflammatory effects was found in nine longer-term stretching studies of the integumentary system.

CONCLUSION

Despite the overall high quality of these summarized studies, evaluation of stretching protocols paralleling yogic stretching is limited. Both injurious and therapeutic stretching induce aspects of inflammatory responses that varied among the different stretching protocols. Inflammatory markers, such as cytokines, are potential outcomes to consider in clinical yoga studies. Future translational research evaluating therapeutic benefits should consider in vitro studies, active vs. passive stretching, shorter-term vs. longer-term interventions, systemic vs. local effects of stretching, animal models resembling human anatomy, control and estimation of non-specific stresses, development of in vivo self-stretching paradigms targeting myofascial tissues, and in vivo models accounting for gross musculoskeletal posture.

Innate immune profiling discriminates between liver regeneration and liver failure following partial hepatectomy

Post-hepatectomy liver failure is a major complication following liver resection and while the basic mechanisms are not well understood, limited regeneration of the remnant tissue contributes to its development. Using an established murine model of 70% partial hepatectomy, we studied the innate immunological profile associated with liver regeneration and liver failure. Following partial hepatectomy, there is a significant increase in circulating CD11b+ myeloid derived cells from (52±10 to 70±12 p&gt;0.01). Further characterization of the CD11b+ cells revealed three different subpopulations: Gr-1hiF4/80, Gr-1hiF4/80+, and Gr-1loF4/80+. Liver failure was accompanying with markedly prolonged and increased mobilization and liver infiltration of activated CD11b+ cells (6±2% on day 0 to 55±12% on day 1 p&gt;0.001). Specifically, the CD11b+Gr-1hiF4/80− cells identified as neutrophils were predominantly increased in these mice from (25±5% to 80±10% p&gt;0.001) on day 1. And persistently remained high until day 7. We also found high IL-6 serum levels in these mice (300±150pg/mL) on day 1. The other CD11b+ cell populations, including Gr-1hiF4/80+ and Gr-1loF4/80+ cells, were markedly reduced in peripheral blood of mice with impaired liver regeneration. In contrast, all CD11b+ populations rapidly recovered to normal levels within 2 days in mice showing normal liver regeneration. In conclusion, following partial hepatectomy, significantly prolonged infiltration of CD11b+ neutrophils and marked reduction of other CD11b+ populations are a hallmark of liver failure. Thus, controlling neutrophil infiltration/activation may help ease recovery from the surgical procedure and improve liver regeneration after partial liver resection.

The effects of UW Solutions in preventing ischemia induced apoptosis of retinal ganglion cells after whole eye transplantation

Background

Retinal ganglion cell (RGC) death from ischemia reperfusion injury and optic nerve transection are challenges to successful restoration of vision by whole eye transplantation (WET). We examined whether University of Wisconsin Solution (UW) or a modified version which includes valproic acid and BaCl2 (mUW) can preserve RGCs in a WET model.

Methods

24 hemifacial rat flaps prepared for WET were flushed with heparinized saline, UW, or mUW. After 85 minutes of ischemia, donor eyes were injected with the same solutions and prepared for immunohistochemistry (IHC) analysis before (n=6/group) or POD7 after (n=3/group) syngeneic WET. Donor and untreated non-ischemic naïve (n=4) retinas were stained for Brn3a and p-cJun (PNJ) to assess RGC viability and apoptosis respectively.

Results

After 85 minutes of ischemia, all donor eyes across treatments (saline, UW, or mUW), had equal levels of Brn3a+ and PNJ+ expression (P&gt;0.05). Naïve eyes averaged ~100k Brn3a+ and ~18k PNJ+ RGCs. At POD7, saline and UW donor eyes each had ~20% loss in Brn3a+ RGCs as compared to control naïve eyes (P&lt;0.05). At POD7, apoptotic signaling increased in both UW and saline donor eye, doubling in PNJ+ signal compared to non-ischemic naïve eyes (P&lt;0.05).

Conclusions

Using a novel system to asses RGC degradation and apoptosis in an experimental rodent WET model, we found that UW and mUW solutions as formulated did not preserve RGCs after WET, despite reports of their anti-ischemic properties in other studies.

Scoping Review of Therapeutic Strategies for Keloids and Hypertrophic Scars

Background:

Keloids are an abnormal proliferation of scars that can involve large areas of tissue beyond the original injury site. Hypertrophic scars are similar clinically, but do not exceed the original scar limits. These scarring abnormalities can cause noxious symptoms such as pain, tenderness, itching, and ulcerations. The aim of this review is to discuss current therapies for both types of abnormal scarring, and to determine if guidelines can be provided for excisional treatment with adjuvant therapies versus non-excisional methods.

Methods:

A systematic literature search was performed through the Web of Science database. The search revolved around keywords such as “keloid,” “hypertrophic scars,” and “treatment.” Articles were reviewed and screened for inclusion and exclusion criteria. The review focuses on an analysis and summarization of randomized control trials regarding keloid or hypertrophic scar treatments.

Results:

The original searches produced 1161 and 1275 articles for keloid and hypertrophic scars, respectively. In total, 316 duplicates were found. After accounting for 2014–2019 publication time, 655 keloid and 893 hypertrophic scar articles were reviewed. This resulted in 15 articles that pertained to treatment and randomized control trials.

Conclusions:

Keloids and hypertrophic scars present a clinical challenge. Based on qualitative review of recurrence, neither excision plus adjuvant therapy or nonsurgical treatments can be recommended preferentially at this time. More research is needed to determine if recurrence rate bias exists between the treatment regimens, as excisional treatment plus adjuvant therapy is reserved for refractory scars.

Absence of porcine endogenous retrovirus (PERV) production from pig lymphoma cell lines

Porcine endogenous retroviruses (PERVs) -A and -B are integrated in the genome of all pigs, whereas PERV-C is found in many, but not all pigs. Some immortalized pig cell lines, among them lymphoma cells, but also mitogen activated primary lymphocytes have been shown to release virus particles, which were able to infect human cells and some of them were recombinant PERV-A/C. Since retroviruses can induce lymphomas, two newly established pig lymphoma cell lines and an older one (L23) were analysed for PERV expression. All three lines harboured PERV-A, PERV-B and PERV-C proviruses, but PERV-A/C recombinants were found only in the genome of L23 cells. The expression at the RNA level was very low and no protein expression and particle release was observed, suggesting that PERVs were not involved in the pathogenesis of these lymphomas. However, all three cell lines were infected with the porcine lymphotropic herpesvirus-3 (PLHV-3), which may have been involved in lymphoma development.

Direct or Collateral Liver Damage in SARS-CoV-2-Infected Patients

Liver injury can result from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection with more than one-third of COVID-19 patients exhibiting elevated liver enzymes. Microvesicular steatosis, inflammation, vascular congestion, and thrombosis in the liver have been described in autopsy samples from COVID-19 patients. Several factors, including direct cytopathic effect of the virus, immune-mediated collateral damage, or an exacerbation of preexisting liver disease may contribute to liver pathology in COVID-19. Due to its immunological functions, the liver is an organ likely to participate in the viral response against SARS-CoV-2 and this may predispose it to injury. A better understanding of the mechanism contributing to liver injury is needed to develop and implement early measures to prevent serious liver damage in patients suffering from COVID-19. This review summarizes current reports of SARS-CoV-2 with an emphasis on how direct infection and subsequent severe inflammatory response may contribute to liver injury in patients with and without preexisting liver disease.

Characterization of immune cells found in keloid versus normal skin tissue

Keloids are abnormal scar formation that extends beyond the confines of the original injury. Immune cell infiltration is associated with keloid pathogenesis, but the exact mechanisms remain unknown. We aim to characterize the immune profile of keloid skin compared to normal skin in order to further understand the role of specific immune subsets in keloid formation. One abdominal normal skin sample and five keloid samples (four ear and one shoulder) were obtained from the Plastic Surgery clinics and the University of Colorado Biorepository Core Facility. Paraffin-embedded samples were stained with CD19+, CD20+, CD3+, CD8+ and FoxP3+ by the Human Immunology and Immunotherapy Initiative. The multiplex immunohistochemistry slides were scanned using Vectra 3 (PerkinElmer, MA, US) and captured images were analyzed with InForm Tissue Finder, phenotpr, and phenoptrReports (Akoya Biosciences, CA, US). CD20+ and CD19+ B cells were significantly increased in keloid tissue compared to normal skin (14.50% and 14.20% vs 6.47% and 7.56%), respectively. In contrast, no significant difference was observed in the percentage of CD3+ and CD8+ cell subsets in keloids compared to normal skin (12.92% and 4.98% vs 8.19% and 4.04%), respectively. Moreover, there was a significant increase in FoxP3+ positive cells found in keloid scars (9.68%) compared to normal skin (2.89%). Further studies examining the role of B cells and FoxP3+ cells in keloid pathogenesis are warranted.

Bispecific human IL2-CCR4 immunotoxin targets human cutaneous T-cell lymphoma

The majority of clinically diagnosed cutaneous T-cell lymphomas (CTCL) highly express the cell-surface markers CC chemokine receptor 4 (CCR4) and/or CD25. Recently, we have developed diphtheria toxin-based recombinant Ontak®-like human IL2 fusion toxin (IL2 fusion toxin) and anti-human CCR4 immunotoxin (CCR4 IT). In this study, we first compared the efficacy of the CCR4 IT vs IL2 fusion toxin for targeting human CD25⁺ CCR4⁺ CTCL. We demonstrated that CCR4 IT was more effective than IL2 fusion toxin. We further constructed an IL2-CCR4 bispecific IT. The bispecific IT was significantly more effective than either IL2 fusion toxin or CCR4 IT alone. The bispecific IT is a promising novel targeted therapeutic drug candidate for the treatment of refractory and recurrent human CD25⁺ and/or CCR4⁺ CTCL.

Elevated Galectin-3 Plasma Concentrations in Recipients of Allogeneic Hematopoietic Cell Transplantation

Galectin-3 is a beta-galactoside-binding lectin with an established association to inflammatory and fibrotic conditions. We investigated galectin-3 levels in 68 recipients of allogeneic hematopoietic cell transplantation (HCT) to look for associations with chronic graft-versus-host disease (cGVHD). Plasma galectin-3 concentrations were measured at 1 year post-HCT and correlated with clinical data collected from individual medical records. The median serum galectin-3 level at that time point was 14.9 ng/mL (range, 5.5–61.6), which was significantly higher than that among healthy controls (14.9 versus 6.2, p < 0.001). Furthermore, patients with active cGVHD at the time of sample collection had higher median levels as compared to those without cGVHD (16.9 versus 13, p = 0.03). In a multivariable logistic model, there was no significant association between the presence of cGVHD at the date of sample collection and elevated galectin-3 levels (>14.9 ng/mL) (odds ratio [OR]: 2.03 (0.60, 6.88), p = 0.26). However, among patients with cGVHD at the date of sample collection, active systemic corticosteroid therapy was associated with elevated galectin-3 levels (OR: 20.32 (1.66, 249.39), p = 0.02). Furthermore, in a competing risk regression model, elevated galectin-3 levels at 1 year post-HCT were not associated with future development of moderate or severe cGVHD (OR: 1.24 (0.21, 7.45), p = 0.81). In conclusion, plasma galectin-3 concentrations are elevated in recipients of allo-HCT, especially among patients with cGVHD. Further investigation will be required to determine whether galectin-3 has a pathophysiologic role in cGVHD or serves as a marker of ongoing inflammation following allogeneic HCT.

Cellular Therapies for the Treatment of Hematological Malignancies; Swine Are an Ideal Preclinical Model

The absence of clinically relevant large animal tumor models has historically forced experimental cellular therapies for hematological malignancies to translate directly from murine models to clinical trials. However, recent advances highlight swine as an ideal large animal model to demonstrate the safety of murine proof of concept studies prior to their implementation clinically. The availability of the MHC defined MGH miniature swine herd has been key for the development of novel approaches for hematopoietic cell and solid organ transplantation. New spontaneously arising hematological malignancies in these swine, specifically myeloid leukemias and B cell lymphomas, resemble human malignancies, which has allowed for development of immortalized tumor cell lines and has implications for the development of a large animal transplantable tumor model. The novel development of a SCID swine model has further advanced the field of large animal cancer models, allowing for engraftment of human tumor cells in a large animal model. Here, we will highlight the advantages of the swine pre-clinical model for the study of hematological malignancies. Further, we will discuss our experience utilizing spontaneously arising tumors in MGH swine to create a transplantable tumor model, describe the potential of the immunodeficient swine model, and highlight several novel cellular and biological therapies for the treatment of hematological malignancies in swine as a large animal pre-clinical bridge.

Development of a Transplantable GFP+ B-Cell Lymphoma Tumor Cell Line From MHC-Defined Miniature Swine: Potential for a Large Animal Tumor Model

The lack of a reliable and reproducible large animal tumor model for the study of hemolymphatic malignancies limits the ability to explore the underlying pathophysiology and testing of novel therapies. The goal of this study was to develop an aggressive, trackable swine tumor cell line in mice for adoptive transfer into MHC matched swine. Two tumor cell lines, post-transplant lymphoproliferative disease (PTLD) 13271 and chronic myelogenous leukemia (CML) 14736, were previously established from the Massachusetts General Hospital (MGH) miniature swine herd. PTLD 13271 is a swine B-cell lymphoma line originating from an animal that developed PTLD following hematopoietic cell transplantation (HCT), while CML 14736 was generated from a swine that spontaneously developed CML. In order to select for aggressive tumor variants, both lines were passage into NOD/SCID IL-2 receptor γ^−/− (NSG) mice. Tumor induced mortality in mice injected with CML14736 was 68% while 100% of mice injected with PTLD 13271 succumbed to PTLD by day 70. Based on aggressiveness, PTLD 13271 was selected for further development and re-passage into NSG mice resulting in increased tumor burden and metastasis. Transduction of the PTLD 13271 cell line with a green fluorescent protein (GFP)-expressing lentivirus facilitated tumor tracking when re-passaged in mice. Utilizing a tolerance induction strategy, GFP+ tumors were injected into an MHC matched miniature swine and successfully followed via flow cytometry for 48 h in circulation, although tumor engraftment was not observed. In summary, we report the development of an aggressive GFP+B-cell lymphoma cell line which has the potential for facilitating development of a large animal tumor model.

Dosing optimization of CCR4 immunotoxin for improved depletion of CCR4+ Treg in nonhuman primates

Recently, we have developed a diphtheria toxin‐based recombinant anti‐human CCR4 immunotoxin for targeting CCR4⁺ tumors and Tregs. In this study, we further optimized the dosing schedule for improved CCR4⁺ Treg depletion. We have demonstrated that up to a 90% depletion was achieved and the depletion extended to approximately 2 weeks in the peripheral blood and more than 48 days in the lymph node at 25 μg·kg⁻¹, BID for 8 consecutive days in cynomolgus monkeys. Expansion was observed including monocytes and NK cells. Antibody against the CCR4 immunotoxin was detected after approximately 2 weeks, affecting further depletion efficacy for multiple course treatment.

The effects of galectin-3 depletion apheresis on induced skin inflammation in a porcine model

Galectin-3 (Gal-3), a β-galactoside-binding lectin that is expressed in mammalian cells, is known to modulate several biological functions such as cell-cell adhesion, macrophage activation, angiogenesis, metastasis, and fibrosis. The goal of this study was to evaluate the ability of Gal-3 depletion apheresis using an adsorption column with immobilized anti-Gal-3-antibody to reduce inflammation induced by Complete Freund's Adjuvant injection in a skin inflammation porcine model. Here, we report that plasma perfusion by apheresis through a Gal-3 binding immuno-affinity column reduces plasma Gal-3 levels to below limits of quantitative detection, and results in significant decrease in skin inflammation, including degree and duration of inflammatory lesions. Human plasma was tested ex vivo and found to be efficiently depleted using the anti-Gal-3 affinity column. This study demonstrates the potential of Gal-3 depletion apheresis as a therapeutic method for inflammation-mediated disease, supporting continued research in this area for clinical application.

Non-invasive monitoring of skin inflammation using an oxygen-sensing paint-on bandage

Inflammation involves a cascade of cellular and molecular mediators that ultimately lead to the infiltration of immune cells into the affected area. This inflammatory process in skin is common to many diseases including acne, infection, and psoriasis, with the presence or absence of immune cells a potential diagnostic marker. Here we show that skin inflammation can be non-invasively measured and mapped using a paint-on oxygen sensing bandage in an in vivo porcine inflammation model. After injection of a known inflammatory agent, the bandage could track the increase, plateau, and decrease in oxygen consumption at the injury site over 7 weeks, as well as discern inflammation resultant from injection at various depths beneath the surface of the skin. Both the initial rate of pO₂ change and the change in bandage pO₂ at equilibration (CBP₂₀) were found to be directly related to the metabolic oxygen consumption rate of the tissue in contact. Healthy skin demonstrated an initial pO₂ decrease rate of 6.5 [Formula: see text], and CBP₂₀ of 84 [Formula: see text]. Inflamed skin had a significantly higher initial consumption rate of 55 [Formula: see text], and a larger CBP₂₀ of 140 [Formula: see text]. The change in the bandage pO₂ before and after equilibration with tissue was found to correlate well with histological evidence of skin inflammation in the animals.

Ontak-like human IL-2 fusion toxin

Ontak® is a FDA-approved diphtheria toxin-based recombinant fusion toxin for treatment of human CD25⁺ cutaneous T cell lymphoma (CTCL). However, it has been discontinued clinically due to the production issue related to the bacterial expression system with difficult purification. Recently we have developed monovalent and bivalent human IL-2 fusion toxins targeting human CD25⁺ cells using advanced unique diphtheria toxin resistant yeast Pichia Pastoris expression system. In vitro efficacy characterization using human CD25⁺ HUT102/6TG cells demonstrated that both monovalent and bivalent isoforms are potent and the bivalent isoform is approximately two logs more potent than the monovalent isoform. In this study, we further assessed the in vivo efficacy of the human IL-2 fusion toxins using human CD25⁺ HUT102/6TG tumor-bearing NSG mouse model. The data demonstrated that both monovalent and bivalent human IL-2 fusion toxins significantly prolonged the survival of the human CD25⁺ tumor-bearing NSG mice in a dose-dependent manner. Then we further assessed the residual tumor cells from the HUT102/6TG tumor-bearing NSG mice using the residual tumor cell bearing NSG mouse model. The results demonstrated that the residual tumor cells were still sensitive to the continual treatment with the human IL-2 fusion toxin. This yeast-expressed human IL-2 fusion toxin will be a promising candidate to replace the clinically discontinued Ontak®.

Diphtheria toxin-based anti-human CD19 immunotoxin for targeting human CD19+ tumors

CD19 is expressed on normal and neoplastic B cells and is a promising target for immunotherapy. However, there is still an unmet need to further develop novel therapeutic drugs for the treatment of the refractory/relapsing human CD19⁺ tumors. We have developed a diphtheria toxin‐based anti‐human CD19 immunotoxin for targeting human CD19⁺ tumors. We have constructed three isoforms of the CD19 immunotoxin: monovalent, bivalent, and foldback diabody. In vitro binding affinity and efficacy analysis demonstrated that the bivalent isoform had the highest binding affinity and in vitro efficacy. The in vivo efficacy of the CD19 immunotoxins was assessed using human CD19⁺ JeKo‐1 tumor‐bearing NOD/SCID IL‐2 receptor γ^−/− (NSG) mouse model. In these animals, CD19 immunotoxins significantly prolonged the median survival from 31 days in controls to 34, 36, and 40 days in animals receiving the monovalent isoform, foldback diabody isoform, and bivalent isoform, respectively. The bivalent CD19 immunotoxin is a promising therapeutic drug candidate for targeting relapsing/refractory human CD19⁺ tumors.

Methods for the detection and serum depletion of porcine galectin-3

BACKGROUND

Circulating galectin-3 (Gal-3) is elevated in systemic inflammatory disorders, fibrotic diseases, and in cancers. Gal-3 is a promising cancer target where it promotes tumorigenesis and metastasis, as well as in renal, pulmonary, hepatic, and cardiovascular diseases, because of its role as a driver of fibrotic remodeling. This reports goal was to establish methods for the detection and removal of porcine Gal-3 that will enable further studies of the therapeutic potential of Gal-3 depletion by apheresis in porcine disease models. The long-term aim is to develop a safe, effective method of removing Gal-3 via apheresis as a standalone therapeutic tool and as an adjuvant to other therapies.

METHODS

Purified recombinant porcine Gal-3 was prepared and used as the standard for development of a porcine Gal-3 enzyme-linked immunosorbent assay (ELISA). Different affinity column matrices that incorporated either a rat IgG2a anti-Gal-3 monoclonal antibody or carbohydrate ligand were assessed for depletion of Gal-3 from porcine serum.

RESULTS

A porcine Gal-3 ELISA with a linear range from 0.3 to 20 ng/mL was able to detect native porcine Gal-3 in both fetal (∼150-200 ng/mL) and juvenile (∼5-15 ng/mL) porcine serum samples. Use of an anti-Gal-3 monoclonal antibody affinity column depleted Gal-3 from porcine serum to at least 313 pg/mL, the limit of ELISA detection.

CONCLUSIONS

Methods have been developed for the detection and depletion of porcine Gal-3. These methods will be used to study the specific effects of Gal-3 depletion via apheresis in porcine models of disease.

Tolerance of Vascularized Islet-Kidney Transplants in Rhesus Monkeys

We previously reported that transplantation (Tx) of prevascularized donor islets as composite islet-kidneys (IK) reversed diabetic hyperglycemia in both miniature swine and baboons. In order to enhance this strategy's potential clinical applicability, we have now combined this approach with hematopoietic stem cell (HSC) Tx in an attempt to induce tolerance in nonhuman primates. IKs were prepared by isolating islets from 70% partial pancreatectomies and injecting them beneath the autologous renal capsule of five rhesus monkey donors at least 3 months before allogeneic IK Tx. HSC Tx was performed after mobilization and leukapheresis of the donors and conditioning of the recipients with total body irradiation, T cell depletion, and cyclosporine. One IK was harvested for histologic analysis and four were transplanted into diabetic recipients. IK Tx was performed either 20-22 (n = 3) or 208 (n = 1) days after HSC Tx. All animals accepted IKs without rejection. All recipients required >20 U/day insulin before IK Tx to maintain <200 mg/dL, whereas after IK Tx, three animals required minimal doses of insulin (1-3 U/day) and one animal was insulin free. These results constitute a proof-of-principle that this IK tolerance strategy may provide a cure for both end-stage renal disease and diabetes without the need for immunosuppression.

Porcine Treg depletion with a novel diphtheria toxin-based anti-human CCR4 immunotoxin

Regulatory T cells (Tregs) are known to play an important role in immunoregulation and have been shown to facilitate induction of transplantation tolerance. Chemokine (C-C motif) receptor 4 (CCR4) is expressed on the surface of effector Tregs involved in controlling alloimmune and autoimmune responses. Recently we have developed a novel diphtheria-toxin based anti-human CCR4 immunotoxin for depleting CCR4⁺ cells in vivo. In this study, we have demonstrated that the anti-human CCR4 immunotoxin bound to porcine lymphocytes including CD4⁺FoxP3⁺ Tregs. Anti-human CCR4 immunotoxin effectively depleted CCR4⁺ Foxp3⁺ porcine Tregs in vivo. We observed depletion of up to 70-85% of the CCR4⁺Foxp3⁺ porcine Tregs in the peripheral blood and 85-91% in the lymph nodes following the anti-human CCR4 immunotoxin treatment in Massachusetts General Hospital (MGH) miniature swine. The depletion lasted for about one week with no significant reduction observed within CCR4^- cell populations including CD8α⁺ T cells, CCR4^-CD4⁺ T cells and B cells. In summary, anti-human CCR4 immunotoxin effectively depleted CCR4⁺Foxp3⁺ porcine Tregs in both peripheral blood and lymph nodes.

Donor Lymphocyte Infusion-Mediated Graft-versus-Host Responses in a Preclinical Swine Model of Haploidentical Hematopoietic Cell Transplantation

We previously described successful hematopoietic stem cell engraftment across MHC barriers in miniature swine without graft-versus-host disease (GVHD) using novel reduced-intensity conditioning regimens consisting of partial transient recipient T cell-depletion, thymic or low-dose total body irradiation, and a short course of cyclosporine A. Here we report that stable chimeric animals generated with these protocols are strongly resistant to donor leukocyte infusion (DLI)-mediated GVH effects. Of 33 total DLIs in tolerant chimeras at clinical doses, 21 failed to induce conversion to full donor hematopoietic chimerism or cause GVHD. We attempted to overcome this resistance to conversion through several mechanisms, including using sensitized donor lymphocytes, increasing the DLI dose, removing chimeric host peripheral blood cells through extensive recipient leukapheresis before DLI, and using fully mismatched lymphocytes. Despite our attempts, the resistance to conversion in our model was robust, and when conversion was achieved, it was associated with GVHD in most animals. Our studies suggest that delivery of unmodified hematopoietic stem cell doses under reduced-intensity conditioning can induce a potent, GVHD-free, immune tolerant state that is strongly resistant to DLI.

Myeloid Leukemias and Virally Induced Lymphomas in Miniature Inbred Swine: Development of a Large Animal Tumor Model

The lack of a large animal transplantable tumor model has limited the study of novel therapeutic strategies for the treatment of liquid cancers. Swine as a species provide a natural option based on their similarities with humans and their already extensive use in biomedical research. Specifically, the Massachusetts General Hospital miniature swine herd retains unique genetic characteristics that facilitate the study of hematopoietic cell and solid organ transplantation. Spontaneously arising liquid cancers in these swine, specifically myeloid leukemias and B cell lymphomas, closely resemble human malignancies. The ability to establish aggressive tumor cell lines in vitro from these naturally occurring malignancies makes a transplantable tumor model a close reality. Here, we discuss our experience with myeloid and lymphoid tumors in major histocompatibility characterized miniature swine and future approaches regarding the development of a large animal transplantable tumor model.

Treg depletion in non-human primates using a novel diphtheria toxin-based anti-human CCR4 immunotoxin

Regulatory T cells (Treg) play an important role in modulating the immune response and has attracted increasing attention in diverse fields such as cancer treatment, transplantation and autoimmune diseases. CC chemokine receptor 4 (CCR4) is expressed on the majority of Tregs, especially on effector Tregs. Recently we have developed a diphtheria-toxin based anti-human CCR4 immunotoxin for depleting CCR4(+) cells in vivo. In this study, we demonstrated that the anti-human CCR4 immunotoxin bound and depleted monkey CCR4(+) cells in vitro. We also demonstrated that the immunotoxin bound to the CCR4(+)Foxp3(+) monkey Tregs in vitro. In vivo studies performed in two naive cynomolgus monkeys revealed 78-89% CCR4(+)Foxp3(+) Treg depletion in peripheral blood lasting approximately 10 days. In lymph nodes, 89-96% CCR4(+)Foxp3(+) Tregs were depleted. No effect was observed in other cell populations including CD8(+) T cells, other CD4(+) T cells, B cells and NK cells. To our knowledge, this is the first agent that effectively depleted non-human primate (NHP) Tregs. This immunotoxin has potential to deplete effector Tregs for combined cancer treatment.

Miniature Swine as a Clinically Relevant Model of Graft-Versus-Host Disease

Miniature swine provide a preclinical model of hematopoietic cell transplantation (HCT) for studies of graft-versus-host disease. HCT between MHC-matched or -mismatched pigs can be performed to mimic clinical scenarios with outcomes that closely resemble those observed in human HCT recipients. With myeloablative conditioning, HCT across MHC barriers is typically fatal, with pigs developing severe (grade III or IV) GVHD involving the gastrointestinal tract, liver, and skin. Unlike rodent models, miniature swine provide an opportunity to perform extended longitudinal studies on individual animals, because multiple tissue biopsies can be harvested without the need for euthanasia. In addition, we have developed a swine GVHD scoring system that parallels that used in the human clinical setting. Given the similarities of GVHD in pigs and humans, we hope that the use of this scoring system facilitates clinical and scientific discourse between the laboratory and the clinic. We anticipate that results of swine studies will support the development of new strategies to improve the identification and treatment of GVHD in clinical HCT scenarios.

Postnatal xenogeneic B-cell tolerance in swine following in utero intraportal antigen exposure

BACKGROUND

The objective of this study was to investigate the humoral immune response to xenogeneic antigens administered during the fetal state utilizing a baboon-to-pig model.

METHODS

Nine fetuses from an alpha-1,3-galactosyltransferase gene knockout (GalT-KO) MGH-miniature swine sow underwent transuterine ultrasound-guided intraportal injection of T-cell depleted baboon bone marrow (B-BM) at mid-gestation. Two juvenile GalT-KO swine undergoing direct B-BM intraportal injection were used as controls.

RESULTS

Postnatal humoral tolerance was induced in the long-term surviving piglets as demonstrated by the absence of any antibody response to baboon donor cells. In addition, a second intraportal B-BM administration at 2.5 months post-birth led to no antibody formation despite re-exposure to xenogeneic antigens. This B-cell unresponsiveness was abrogated only when the animal was exposed subcutaneously to third-party xenogeneic and allogeneic antigens, suggesting that the previously achieved humoral non-responsiveness was donor specific. In comparison, the two juvenile GalT-KO control swine demonstrated increasing anti-baboon IgM and IgG levels following intraportal injection.

CONCLUSIONS

In summary, xenogeneic B-cell tolerance was induced through in utero intraportal exposure to donor cells and this tolerance persisted following postnatal rechallenge with donor B-BM, but was lost on exposure to third-party antigen, possibly as a result of cross-reactive antibody formation.

Diphtheria toxin-based recombinant murine IL-2 fusion toxin for depleting murine regulatory T cells in vivo

Regulatory T cells (Tregs) are a subpopulation of CD4(+) T cells which suppress immune responses of effector cells and are known to play a very important role in protection against autoimmune disease development, induction of transplantation tolerance and suppression of effective immune response against tumor cells. An effective in vivo Treg depletion agent would facilitate Treg-associated studies across many research areas. In this study, we have developed diphtheria toxin-based monovalent and bivalent murine IL-2 fusion toxins for depleting murine IL-2 receptor positive cells including CD25(+) Treg in vivo. Their potencies were assessed by in vitro protein synthesis inhibition and cell proliferation inhibition assays using a murine CD25(+) CTLL-2 cell line. Surprisingly, in contrast to our previously developed recombinant fusion toxins, the monovalent isoform (DT390-mIL-2) was approximately 4-fold more potent than its bivalent counterpart (DT390-bi-mIL-2). Binding analysis by flow cytometry demonstrated that the monovalent isoform bound stronger than the bivalent version. In vivo Treg depletion with the monovalent murine IL-2 fusion toxin was performed using C57BL/6J (B6) mice. Spleen Treg were significantly depleted with a maximum reduction of ∼70% and detectable as early as 12 h after the last injection. The spleen Treg numbers were reduced until Day 3 and returned to control levels by Day 7. We believe that this monovalent murine IL-2 fusion toxin will be an effective in vivo murine Treg depleter.

Diphtheria-toxin based anti-human CCR4 immunotoxin for targeting human CCR4(+) cells in vivo

CC chemokine receptor 4 (CCR4) has attracted much attention as a promising therapeutic drug target for CCR4(+) tumor cells and Tregs. CCR4 is expressed on some tumor cells such as T-cell acute lymphoblastic leukemia (ALL), adult T-cell leukemia/lymphoma (ATLL), adult peripheral T cell lymphoma (PTCL) and cutaneous T cell lymphoma (CTCL). CCR4 is also expressed on majority of Tregs, mainly effector Tregs. In this study we have successfully developed three versions of diphtheria-toxin based anti-human CCR4 immunotoxins (monovalent, bivalent and single-chain fold-back diabody). Binding analysis by flow cytometry showed that all three versions of the anti-human CCR4 immunotoxins bound to the human CCR4(+) tumor cell line as well as CCR4(+) human PBMC. The bivalent isoform bound stronger than its monovalent counterpart and the single-chain foldback diabody isoform was the strongest among the three versions. In vitro efficacy analysis demonstrated that the bivalent isoform was 20 fold more potent in inhibiting cellular proliferation and protein synthesis in human CCR4(+) tumor cells compared to the monovalent anti-human CCR4 immunotoxin. The single-chain fold-back diabody isoform was 10 fold more potent than its bivalent counterpart and 200 fold more potent than its monovalent counterpart. The in vivo efficacy was assessed using a human CCR4(+) tumor-bearing mouse model. The immunotoxin significantly prolonged the survival of tumor-bearing NOD/SCID IL-2 receptor γ(-/-) (NSG) mice injected with human CCR4(+) acute lymphoblastic leukemia cells compared with the control group. This novel anti-human CCR4 immunotoxin is a promising drug candidate for targeting human CCR4(+) tumor cells and Tregs in vivo.

Developing cellular therapies for retinal degenerative diseases

Biomedical advances in vision research have been greatly facilitated by the clinical accessibility of the visual system, its ease of experimental manipulation, and its ability to be functionally monitored in real time with noninvasive imaging techniques at the level of single cells and with quantitative end-point measures. A recent example is the development of stem cell-based therapies for degenerative eye diseases including AMD. Two phase I clinical trials using embryonic stem cell-derived RPE are already underway and several others using both pluripotent and multipotent adult stem cells are in earlier stages of development. These clinical trials will use a variety of cell types, including embryonic or induced pluripotent stem cell-derived RPE, bone marrow- or umbilical cord-derived mesenchymal stem cells, fetal neural or retinal progenitor cells, and adult RPE stem cells-derived RPE. Although quite distinct, these approaches, share common principles, concerns and issues across the clinical development pipeline. These considerations were a central part of the discussions at a recent National Eye Institute meeting on the development of cellular therapies for retinal degenerative disease. At this meeting, emphasis was placed on the general value of identifying and sharing information in the so-called "precompetitive space." The utility of this behavior was described in terms of how it could allow us to remove road blocks in the clinical development pipeline, and more efficiently and economically move stem cell-based therapies for retinal degenerative diseases toward the clinic. Many of the ocular stem cell approaches we discuss are also being used more broadly, for nonocular conditions and therefore the model we develop here, using the precompetitive space, should benefit the entire scientific community.

Diphtheria toxin-based bivalent human IL-2 fusion toxin with improved efficacy for targeting human CD25(+) cells

Regulatory T cells (Treg) constitute a major inhibitory cell population which suppresses immune responses. Thus, Treg have proven to be key players in the induction of transplantation tolerance, protection from autoimmune disease and prevention of the development of effective anti-tumor immune reactions. Treg express high levels of the high affinity interleukin-2 receptor (IL-2R) consisting of IL-2Rα (CD25) together with IL-2Rβ (CD122) and the common γ-chain (CD132). An effective reagent capable of depleting Treg in vivo would facilitate better cancer treatment and allow mechanistic studies of the role of Treg in transplantation tolerance and the development of autoimmune disease. In this study, we have developed a novel bivalent human IL-2 fusion toxin along with an Ontak®-like monovalent human IL-2 fusion toxin and compared the functional ability of these reagents in vitro. Here we show that genetically linking two human IL-2 domains in tandem, thereby generating a bivalent fusion toxin, results in significantly improved capacity in targeting human CD25(+) cells in vitro. Binding analysis by flow cytometry showed that the bivalent human IL-2 fusion toxin has notably increased affinity for human CD25(+) cells. In vitro functional analysis demonstrated that the bivalent isoform has an increased potency of approximately 2 logs in inhibiting cellular proliferation and protein synthesis in human CD25(+) cells compared to the monovalent human IL-2 fusion toxin. Additionally, we performed two inhibition assays in order to verify that the fusion toxins target the cells specifically through binding of the human IL-2 domain of the fusion toxin to the human IL-2 receptor on the cell surface. These results demonstrated that 1) both monovalent and bivalent human IL-2 fusion toxins are capable of blocking the binding of biotinylated human IL-2 to human CD25 by flow cytometry; and 2) human IL-2 blocked the fusion toxins from inhibiting protein synthesis and cellular proliferation in vitro, thus confirming that the human IL-2 fusion toxins target the cells specifically through binding to the human IL-2 receptor. We believe that the bivalent human IL-2 fusion toxin will be a more potent, and therefore, more optimal agent than the current clinically-used monovalent fusion toxin (denileukin diftitox, Ontak®) for in vivo depletion of Treg.

Increased levels of anti-non-Gal IgG following pig-to-baboon bone marrow transplantation correlate with failure of engraftment

BACKGROUND

The development of genetically modified pigs, which lack the expression of alpha 1-3 galactosyl transferase, (GalT-KO pigs) has facilitated the xenogeneic transplantation of porcine organs and tissues into primates by avoiding hyperacute rejection due to pre-existing antibodies against the Gal epitope. However, antibodies against other antigens (anti-non-Gal antibodies), are found at varying levels in the pre-transplant sera of most primates. We have previously found that baboons with high levels of pre-transplant anti-non-Gal IgG, conditioned with a non-myeloablative conditioning regimen, failed to engraft following pig-to-baboon bone marrow transplantation (Xenotransplantation, 17, 2010 and 300). Two baboons with low levels of pre-transplant anti-non-Gal IgG, conditioned with the same regimen, showed porcine bone marrow progenitors at 28 days following transplantation, suggesting engraftment. These baboons also showed evidence of donor-specific hyporesponsiveness. This observation led us to investigate the hypothesis that selecting for baboon recipients with low pre-transplant anti-non-Gal IgG levels might improve engraftment levels following GalT-KO pig-to-baboon bone marrow transplantation.

METHODS

Five baboons, with low pre-transplant anti-non-Gal IgG levels, received transplantation of bone marrow cells (1-5 × 10(9) /kg of recipient weight) from GalT-KO pigs. They received a non-myeloablative conditioning regimen consisting of low-dose total body irradiation (TBI) (150 cGy), thymic irradiation (700 cGy), anti-thymocyte globulin (ATG), and tacrolimus. In addition, two baboons received Rituximab and Bortezomib (Velcade) treatment as well as extra-corporeal immunoadsorption using GalT-KO pig livers. Bone marrow engraftment was assessed by porcine-specific PCR on colony forming units (CFU) of day 28 bone marrow aspirates. Anti-non-Gal antibody levels were assessed by serum binding toward GalT-KO PBMC using flow cytometry (FACS). Peripheral macro-chimerism was measured by FACS using pig and baboon-specific antibodies and baboon anti-pig cellular responses were assessed by mixed lymphocyte reactions (MLR).

RESULTS

As previously reported, two of five baboons demonstrated detectable bone marrow engraftment at 4 weeks after transplantation. Engraftment was associated with lack of an increase in anti-non-Gal IgG levels as well as cellular hyporesponsiveness toward pig. Three subsequent baboons with similarly low levels of pre-existing anti-non-Gal IgG showed no engraftment and an increase in anti-non-Gal IgG antibody levels following transplantation. Peripheral macrochimerism was only seen for a few days following transplantation regardless of antibody development.

CONCLUSIONS

Selecting for baboon recipients with low levels of pre-transplant anti-non-Gal IgG did not ensure bone marrow engraftment. Failure to engraft was associated with an increase in anti-non-Gal IgG levels following transplantation. These results suggest that anti-non-Gal-IgG is likely involved in early bone marrow rejection and that successful strategies for combating anti-non-Gal IgG development may allow better engraftment. Since engraftment was only low and transient regardless of antibody development, innate immune, or species compatibility mechanisms will likely also need to be addressed to achieve long term engraftment.

Development of a diphtheria toxin-based recombinant porcine IL-2 fusion toxin for depleting porcine CD25+ cells

Regulatory T cells (Tregs) have been widely recognized as crucial players in controlling immune responses. Because their major role is to ensure that the immune system is not over reactive, Tregs have been the focus of multiple research studies including those investigating transplantation tolerance, autoimmunity and cancer treatment. On their surface Tregs constitutively express CD25, a high affinity receptor for the cytokine interleukin-2 (IL-2). The reagents constructed in this study were generated by genetically linking porcine IL-2 to the truncated diphtheria toxin (DT390). This reagent functions by first binding to the cell surface via the porcine IL-2/porcine CD25 interaction then the DT390 domain facilitates internalization followed by inhibition of protein synthesis resulting in cell death. Four versions of the porcine IL-2 fusion toxin were designed in an interest to find the most effective isoform: 1) monovalent glycosylated porcine IL-2 fusion toxin (Gly); 2) monovalent non-N-glycosylated porcine IL-2 fusion toxin (NonGly); 3) bivalent glycosylated porcine IL-2 fusion toxin (Bi-Gly); 4) bivalent non-N-glycosylated porcine IL-2 fusion toxin (Bi-NonGly). Using a porcine CD25(+) B cell lymphoma cell line (LCL13271) in vitro analysis of the fusion toxins' ability to inhibit protein synthesis demonstrated that the Bi-NonGly fusion toxin is the most efficient reagent. These in vitro results are consistent with binding affinity as the Bi-NonGly fusion toxin binds strongest to CD25 on the same LCL13271 cells. The Bi-Gly fusion toxin significantly prolonged the survival (p=0.028) of tumor-bearing NOD/SCID IL-2 receptor γ(-/-) (NSG) mice injected with LCL13271 cells compared with untreated controls. This recombinant protein has great potential to function as a useful tool for in vivo depletion of porcine CD25(+) cells for studying immune regulation.

Molecular basis of cross-species reactivities of human versus porcine CTLA-4

The binding motif of human CTLA-4 is well known to be MYPPPY and for porcine CTLA-4 the binding motif is LYPPPY. Is this single amino acid difference of methionine (M) versus leucine (L) critical for the CTLA-4 binding? Recently, we have reported that the recombinant soluble porcine CTLA-4 was incapable of binding to human CD80. In this study we mutated L to M in the binding motif of the soluble porcine CTLA-4 and mutated M to L in the binding motif of the soluble human CTLA-4. We then analyzed how these mutations affected the binding affinity of the mutants to both porcine and human CD80(+) cells. The soluble porcine CTLA-4-L97M mutant partially lost its binding affinity to porcine CD80 compared to the wild-type and conferred very weak binding ability to human CD80. These results indicate that the L in the binding motif of porcine CTLA-4 is important for determining its binding ability to porcine CD80. Wild-type soluble human CTLA-4 binds to both human and porcine CD80 with comparable affinity, however, the soluble human CTLA-4-M97L mutant almost lost its binding ability to human CD80 and increased its binding ability to porcine CD80. These results indicate that M in the human CTLA-4 binding motif is extremely critical for its binding to human CD80. Those data suggest that the human CTLA-4 based recombinant protein drugs such as human CTLA-4-Ig can be used and/or tested in a porcine model. Conversely, the use of porcine CTLA-4 based recombinant protein drugs such as porcine CTLA-4-Ig is restricted to swine models. The difference in binding specificity of CTLA-4 observed in this study may be useful for studies such as pig to nonhuman primate xeno-transplantation. Porcine CTLA-4- and human CTLA-4-M97L mutant-based recombinant protein drugs can be used to specifically block the direct presentation by donor antigen presenting cells in pig to nonhuman primate xeno-transplantation. Human CTLA-4-M97L mutant-based recombinant protein drugs will be more ideal as it is without immunogenicity to human being.

A truncated diphtheria toxin based recombinant porcine CTLA-4 fusion toxin

Targeted cell therapies are possible through the generation of recombinant fusion proteins that combine a toxin, such as diphtheria toxin (DT), with an antibody or other molecule that confers specificity. Upon binding of the fusion protein to the cell of interest, the diphtheria toxin is internalized which results in protein synthesis inhibition and subsequent cell death. We have recently expressed and purified the recombinant soluble porcine CTLA-4 both with and without N-glycosylation in yeast Pichia pastoris for in vivo use in our preclinical swine model. The glycosylated and non-N-glycosylated versions of this recombinant protein each bind to a porcine CD80 expressing B-cell lymphoma line (LCL13271) with equal affinity (K(D)=13 nM). In this study we have linked each of the glycosylated and non-N-glycosylated soluble porcine CTLA-4 proteins to the truncated diphtheria toxin DT390 through genetic engineering yielding three versions of the porcine CTLA-4 fusion toxins: 1) monovalent glycosylated soluble porcine CTLA-4 fusion toxin; 2) monovalent non-N-glycosylated soluble porcine CTLA-4 fusion toxin and 3) bivalent non-N-glycosylated soluble porcine CTLA-4 fusion toxin. Protein synthesis inhibition analysis demonstrated that while all three fusion toxins are capable of inhibiting protein synthesis in vitro, the non-N-glycosylated porcine CTLA-4 isoforms function most efficiently. Binding analysis using flow cytometry of the porcine CTLA-4 fusion toxins to LCL13271 cells also demonstrated that the non-N-glycosylated porcine CTLA-4 isoforms bind to these cells with higher affinity compared to the glycosylated fusion toxin. The monovalent non-N-glycosylated porcine CTLA-4 fusion toxin was tested in vivo. NSG (NOD/SCID IL-2 receptor γ(-)/(-)) mice were injected with porcine CD80(+) LCL13271 tumor cells. All animals succumbed to tumors and those treated with the monovalent non-N-glycosylated porcine CTLA-4 fusion toxin survived longer based on a symptomatic scoring system compared to the untreated controls. This recombinant protein may therefore provide a novel approach for in vivo depletion of porcine antigen presenting cells (APCs) for studies investigating the induction of transplantation tolerance, autoimmune disease and cancer treatment.

Leukapheresis protocol for nonhuman primates weighing less than 10 kg

Leukapheresis is a common procedure for hematopoietic cell transplantation in adults. The main challenge in applying this procedure to human infants and small monkeys is the large extracorporeal blood volume (165 mL on average) necessary for priming the apheresis machine. This volume represents greater than 50% of the total circulating blood volume of a human neonate or small monkey. In this report, we document a safe leukapheresis protocol developed for rhesus macaques (3.9 to 8.7 kg). To avoid sensitizing donor animals undergoing leukapheresis to third-party blood products, autologous blood collected during the weeks prior to leukapheresis was used to volume-expand the same donor while priming the machine with saline on the day of leukapheresis. During the procedures, blood pressure was controlled by monitoring the inlet volume, and critical-care support was provided by the anesthesia team. Electrolytes and hemogram parameters were monitored intermittently. Overall, our research subjects underwent effective 4- to 6-h leukapheresis. A total of 9 leukapheresis procedures were performed, which yielded 1 × 10(9) to 6 × 10(9) peripheral blood mononuclear cells containing 1.1 to 5.1 × 10(6) CD34(+) cells (assessed in 4 of 9 macaques) in a volume of 30 to 85 mL. All macaques showed decreases in Hct and platelet counts. In summary, we report a successful modified leukapheresis procedure that can be performed safely in small animals without modification of the leukapheresis machine or associated cell-collection kits.

Effects of mobilization regimens in donors on outcomes of hematopoietic cell transplantation in miniature Swine

Toxicities and complications associated with hematopoietic cell transplantation currently limit this potentially curative therapy for malignant and nonmalignant blood disorders. Miniature swine provide a clinically relevant model for studies to improve posttransplantation outcomes. Miniature swine recipients of high-dose haploidentical hepatopoietic cell transplantation after reduced-intensity conditioning consisting of low-dose (100 cGy) total-body irradiation, partial T-cell depletion by using a CD3 immunotoxin, and a 45-d course of cyclosporine A typically successfully engraft without graft-versus-host disease. We recently observed broad variability in engraftment outcomes that correlates with the occurrence of adverse reactions in donors after cytokine treatment to mobilize hematopoietic progenitor cells from the bone marrow to the peripheral blood for collection. Haploidentical recipients (n = 16) of cells from donors remaining healthy during cytokine treatment engrafted with multilineage chimerism, did not develop graft-versus-host disease, and did not require any blood products. In comparison, identically conditioned recipients of cells from donors that had severe reactions during cytokine treatment had adverse outcomes, including the development of clinically significant thrombocytopenia requiring blood product support in 8 of 11 swine. Furthermore, all 11 recipients lost peripheral blood myeloid chimerism (indicating lack of engraftment of donor stem cells). These data suggest that posttransplantation complications in swine are influenced by the health status of the donor before and during the collection of hematopoietic cells by leukapheresis.

Abstract 114: Allogeneic Cardiosphere-Derived Cells Are Safe and Effective in a Pig Model of Myocardial Infarction

Allogeneic cardiosphere-derived cells (CDCs) have proven safe and effective in a small animal model of myocardial infarction (MI), and have been shown to act primarily via paracrine mechanisms to stimulate endogenous regeneration. The present translational study tested allogeneic CDCs in a large animal model (mini-pigs).

To establish a robust allogeneic model, all pigs were swine leukocyte antigen (SLA) typed by PCR. A male donor and female recipients with full SLA I, II mismatch were used. Pigs underwent balloon occlusion of the LAD for 2.5 hours, followed by reperfusion. Two weeks later, 12.5 million CDCs (n=8) or vehicle (n=6) were infused. Animals were sacrificed 2 weeks or 2 months post-infusion to assess the cellular (histology using a clinical rejection scale) and humoral (donor-specific antibodies, complement-dependent cytotoxicity) immune responses, as well as cardiac function (left ventriculography, hemodynamics, morphometry). Numerous in-life assessments for safety were performed and CDC engraftment was assessed by FISH for Y chromosome.

All immunological assays indicated an undetectable response to CDCs. Cardiac enzymes and systemic inflammation showed no differences between groups. There were no systemic histological findings related to CDCs. CDCs did not permanently engraft, with <0.1% persisting 2 weeks post-infusion and none evident 2 months post. Despite evanescent engraftment, functional benefits were seen following infusion of CDCs. Ejection fraction (EF) and infarct size (IS) were significantly improved in CDC-treated animals compared to vehicle-treated 2 weeks post-infusion (EF: 48.6±2.1% vs 38.2±2.6%, p<0.05; IS: 9±2 vs 14±2%, p<0.05). At 2 months, EF still trended higher in CDC-treated animals (42±5 vs 32±10%, p=0.09), and IS still trended lower (14±4 vs 16±7%, p=0.60). Pressure-volume relationships revealed a trend for enhanced contractility in CDC-treated animals (Emax: 3.2±2.2 vs 1.0±1.1 mmHg/mL, p=0.26). The magnitude of the functional benefits was similar to that seen in a prior pig study using autologous CDCs.

Overall, results of the present study demonstrate that allogeneic CDCs are largely equivalent to autologous in terms of efficacy, and elicit no detectable immunological response or safety concern.

Edema and tetraparesis in a miniature pig after allogeneic hematopoietic cell transplantation

A 3-mo-old, 12-kg, intact, miniature pig presented with severe neurologic signs on day 8 after hematopoietic cell transplantation. This pig had received an immunosuppressive regimen before transplantation that included an antiCD3 immunotoxin for T-cell depletion, 100 cGy of total-body irradiation, and cyclosporine for 45 d. The pig began exhibiting erythematous lesions on posttransplantation day 7. He also demonstrated increased conscious proprioceptive deficits and recumbency but normal mentation. Neurologic signs worsened over several days; the pig became lethargic but remained afebrile. Conjunctival swelling developed on posttransplantation day 9, which subsequently spread to the animal's head, ears and hocks by day 10. Analgesics were given for pain, and cyclosporine levels were decreased. Despite the measures taken, neurologic signs progressed. Given the worsening subcutaneous edema and neurologic status, Escherichia coli infection was suspected, and treatment with a third-generation cephalosporin was instituted. The clinical signs resolved within 12 h after the start of antibiotics. 'Shiga-like' toxin from E. coli can cause peracute toxemia and induce ataxia, paralysis, and recumbency. Other common and pathognomonic findings include periocular edema and variable edema in other subcutaneous regions. A fecal sample demonstrated an overgrowth of gram-negative, lactose-fermenting colonies. On the basis of the clinical presentation, exclusion of other potential conditions compatible with edema and neurologic diseases, physical exam findings, microbiology and the resolution of signs after therapy, the pig was diagnosed with edema disease.

Effect of pre-existing anti-diphtheria toxin antibodies on T cell depletion levels following diphtheria toxin-based recombinant anti-monkey CD3 immunotoxin treatment

Diphtheria toxin (DT)-based anti-CD3 immunotoxins have clinical relevance in numerous applications including autoimmune disease therapies and organ transplantation tolerance protocols. Pre-existing anti-DT antibodies acquired either by vaccination against diphtheria toxin or infections with C. diphtheriae may interfere or inhibit the function of these anti-CD3 immunotoxins. Previously, a full-length anti-rhesus monkey CD3 immunotoxin, FN18-CRM9, was shown to be less effective at depleting circulating T cells in animals with pre-existing anti-DT antibody titers than in animals without antibodies, and subsequent doses were ineffective. In this study, the T cell depletion function of a truncated DT based recombinant anti-monkey CD3 immunotoxin, A-dmDT390-scfbDb (C207), as part of a reduced intensity conditioning regimen prior to hematopoietic cell transplantation, was compared between two groups of monkeys: those with and without pre-existing anti-diphtheria titers. T cell depletion was comparable in both groups of monkeys, and therefore appeared to be unaffected by the presence of moderate levels of pre-existing anti-diphtheria antibodies.

Expression and characterization of recombinant soluble porcine CD3 ectodomain molecules: mapping the epitope of an anti-porcine CD3 monoclonal antibody 898H2-6-15

The porcine CD3 specific monoclonal antibody 898H2-6-15 has been used in allo- and xeno-transplantation studies as a porcine CD3 marker and as an effective T cell depletion reagent when conjugated to the diphtheria toxin mutant, CRM9. A recombinant anti-porcine CD3 immuntoxin was recently developed using single-chain variable fragments (scFv) derived from 898H2-6-15. In this study, using published sequence data, we have expressed the porcine CD3 ectodomain molecules in E. coli through inclusion body isolation and in vitro refolding approach. The expressed and refolded porcine CD3 ectodomain molecules include CD3ε, CD3γ, CD3δ, CD3εγ heterodimer, CD3εδ heterodimer, CD3εγ single-chain fusion protein and CD3εδ single-chain fusion protein. These refolded porcine CD3 ectodomain molecules were purified with a strong anion exchange resin Poros 50HQ. ELISA analysis demonstrated that only the porcine CD3εγ ectodomain single-chain fusion protein can bind to the porcine CD3 specific monoclonal antibody 898H2-6-15. The availability of this porcine CD3εγ ectodomain single-chain fusion protein will allow screening for affinity matured variants of scFv derived from 898H2-6-15 to improve the recombinant anti-porcine CD3 immunotoxin. Porcine CD3εγ ectodomain single-chain fusion protein will also be a very useful reagent to study the soluble phase interaction between porcine CD3εγ and porcine CD3 antibodies such as 898H2-6-15.