A Retrospective Analysis: Autologous Peripheral Blood Hematopoietic Stem Cell Transplant Combined With Adoptive T-Cell Therapy for the Treatment of High-Grade B-Cell Lymphoma in Ten Dogs

In humans, a type of cellular immunotherapy, called adoptive T cell transfer (ACT), can elicit curative responses against hematological malignancies and melanoma. ACT using ex vivo expanded peripheral blood T-cells after multiagent chemotherapy enhances tumor-free survival of dogs with B-cell lymphoma (LSA). Since 2008, our group has been performing autologous peripheral blood hematopoietic stem cell transplants (autoPBHSCT) for the treatment of canine high-grade B-cell LSA, although relapse of residual disease is a common cause of reduced survival in ~70% of treated dogs. We reasoned that a more aggressive treatment protocol combining CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone) chemotherapy, autoPBHSCT, and ACT to treat 10 dogs with B-cell LSA could lead to better outcomes when compared to dogs treated with CHOP chemotherapy and autoPBHSCT alone. Using this protocol, once dogs achieved complete hematologic reconstitution post-autoPBHSCT, CD3+ CD8+ and CD3+CD4+ T-cells were expanded from the peripheral blood at a commercial laboratory. Two to four ACT infusions were given to each dog, with a total of 23 infusions given. Infusions were administered with no complications or adverse events. The median cell dose for all infusions was 5.62 x 10⁶ cells/kg (range: 2.59 x 10⁶-8.55 x 10⁶ cells/kg). 4/10 (40%) of dogs were cured of their disease (defined as disease-free for ≥2 years post-autoPBHSCT). Our results confirm that the autoPBHSCT protocol did not hinder the in vitro expansion of autologous peripheral blood T-cells and that the final product could be administered safely, with no adverse events recorded. Finally, since only ten dogs were treated, our results can only suggest that the administration of ACT to dogs after multiagent chemotherapy and autoPHSCT did not lead to a statistically significant increase in median disease-free interval and overall survival when compared to dogs who received CHOP chemotherapy and autoPHSCT alone.

Evolution of haematopoietic cell transplantation for canine blood disorders and a platform for solid organ transplantation

Pre-clinical haematopoietic cell transplantation (HCT) studies in canines have proven to be invaluable for establishing HCT as a highly successful clinical option for the treatment of malignant and non-malignant haematological diseases in humans. Additionally, studies in canines have shown that immune tolerance, established following HCT, enabled transplantation of solid organs without the need of lifelong immunosuppression. This progress has been possible due to multiple biological similarities between dog and mankind. In this review, the hurdles that were overcome and the methods that were developed in the dog HCT model which made HCT clinically possible are examined. The results of these studies justify the question whether HCT can be used in the veterinary clinical practice for more wide-spread successful treatment of canine haematologic and non-haematologic disorders and whether it is prudent to do so.

Safety and efficacy of a nonmyeloablative pretransplant conditioning regimen using total lymphoid irradiation with volumetric modulated arc therapy in healthy dogs: A pilot study

Allogeneic hematopoietic cell transplantation (HCT) has been an effective treatment for human patients with haematological malignancies (Baron & Storb, 2006; Bair et al., 2020; Copelan et al., 2019). However, the optimal pretransplant conditioning treatment is unclear in canine allogeneic HCT. This pilot study aimed to evaluate the safety and efficacy of total lymphoid irradiation (TLI) with volumetric modulated arc therapy (VMAT) for a nonmyeloablative HCT conditioning. Six healthy dogs were treated with 8 or 12 Gy TLI using VMAT. Haematological and physical changes were recorded over 8 weeks. To assess the effect of peripheral lymphocyte condition, lymphocyte subset and proliferative ability were examined. At the end of the experiment, necropsy was performed. All dogs showed mild‐to‐moderate neutropenia and thrombocytopenia, and these haematological changes resolved spontaneously. One dog treated with 8 Gy TLI developed transient cutaneous infection. No major complication was seen in the other seven dogs. Myelocytes and erythroblast cytopenia of bone marrow were detected in two dogs treated with 12 Gy TLI. This study is the first report of TLI using VMAT in dogs, and results suggest that this regimen is a feasible nonmyeloablative treatment.

Challenges of stem cell therapies in companion animal practice

Regenerative medicine using stem cells from various sources are emerging treatment modality in several refractory diseases in veterinary medicine. It is well-known that stem cells can differentiate into specific cell types, self-renew, and regenerate. In addition, the unique immunomodulatory effects of stem cells have made stem cell transplantation a promising option for treating a wide range of disease and injuries. Recently, the medical demands for companion animals have been rapidly increasing, and certain disease conditions require alternative treatment options. In this review, we focused on stem cell application research in companion animals including experimental models, case reports and clinical trials in dogs and cats. The clinical studies and therapeutic protocols were categorized, evaluated and summarized according to the organ systems involved. The results indicate that evidence for the effectiveness of cell-based treatment in specific diseases or organ systems is not yet conclusive. Nonetheless, stem cell therapy may be a realistic treatment option in the near future, therefore, considerable efforts are needed to find optimized cell sources, cell numbers and delivery methods in order to standardize treatment methods and evaluation processes.

Acquired factor V inhibitors after allogeneic hematopoietic stem cell transplantation in a dog

Objective

Describe the clinical course and management of a dog that underwent hematopoietic stem cell transplantation (HSCT) for treatment of B‐cell lymphoma and developed acquired circulating factor V (FV) inhibitors.

Case Summary

An 8‐year‐old male castrated Briard dog diagnosed with lymphoma (IVb, B‐cell) presented for allogeneic HSCT. Despite multiple platelet, fresh frozen plasma, and red blood cell transfusions prolonged recovery and clinical bleeding occurred. Circulating acquired FV inhibitors were identified and hemorrhage subsequently was managed by immunosuppression. The dog was discharged when clinical resolution of bleeding was achieved.

New or Unique Information Provided

This case report describes a dog undergoing curative intent treatment for lymphoma, and subsequently acquiring factor inhibition, and was successfully managed. Specific coagulation screening to assess for coagulation factor deficiencies or inhibitors is essential in the diagnosis and treatment of patients with refractory bleeding or only transient response to blood transfusion.

Developments and translational relevance for the canine haematopoietic cell transplantation preclinical model

The development of safe and reliable haematopoietic cell transplantation (HCT) protocols to treat human patients with malignant and non-malignant blood disorders was highly influenced by preclinical studies obtained in random-bred canines. The surmounted barriers included recognizing the crucial importance of histocompatibility matching, establishing long-term donor haematopoietic cell engraftment, preventing graft-vs-host disease and advancing effective conditioning and post-grafting immunosuppression protocols, all of which were evaluated in canines. Recent studies have applied the tolerance inducing potential of HCT to solid organ and vascularized composite tissue transplantation. Several advances in HCT and tolerance induction that were first developed in the canine preclinical model and subsequently applied to human patients are now being recruited into veterinary practice for the treatment of malignant and non-malignant disorders in companion dogs. Here, we review recent HCT advancements attained in the canine model during the past 15 years.

Implementation of total body photon irradiation as part of an institutional bone marrow transplant program for the treatment of canine lymphoma and leukemias

A total body irradiation (TBI) protocol was developed to support a bone marrow transplant (BMT) program for the treatment of canine hematologic malignancies. The purpose of this prospective study is to describe implementation of the protocol and resultant dosimetry. Nongraphic manual treatment planning using 6 MV photons, isocentric delivery, 40 × 40 cm field size, wall-mounted lasers to verify positioning, a lucite beam spoiler (without use of bolus material), a dose rate of 8.75 cGy/min at patient isocenter, and a source-to-axis distance of 338 cm were used for TBI. A monitor unit calculation formula was derived using ion chamber measurements and a solid water phantom. Five thermoluminescent dosimeters (TLDs) were used at various anatomic locations in each of four cadaver dogs, to verify fidelity of the monitor unit formula prior to clinical implementation. In vivo dosimetric data were then collected with five TLDs at various anatomic locations in six patients treated with TBI. A total dose of 10 Gy divided into two 5 Gy fractions was delivered approximately 16 h apart, immediately followed by autologous stem cell transplant. The mean difference between prescribed and delivered doses ranged from 99% to 109% for various sites in cadavers, and from 83% to 121% in clinical patients. The mean total body dose in cadavers and clinical patients when whole body dose was estimated by averaging doses measured by variably placed TLDs ranged from 98% to 108% and 93% to 102% of the prescribed dose, respectively, which was considered acceptable. This protocol could be used for institutional implementation of TBI.