Prevention of graft-versus-host disease. Studies in a canine model

Induction of Tolerance Towards Solid Organ Allografts Using Hematopoietic Cell Transplantation in Large Animal Models

Background

The application of hematopoietic cell transplantation for induction of immune tolerance has been limited by toxicities associated with conditioning regimens and to graft-versus-host disease (GVHD). Decades of animal studies have culminated into sufficient control of these two problems, making immune tolerance a viable alternative to life-long application of immunosuppressive drugs to prevent allograft rejection.

Methods

Studies in mice have paved the way for the application of HCT with limited toxicity in large animal models. Resultant studies in the pig, dog, and ultimately the nonhuman primate have led to appropriate methods for achieving nonmyeloablative irradiation protocols, dose, and timing of post-grafting immunosuppressive drugs, monoclonal antibody therapy, and biologicals for costimulatory molecule blockade. The genetics field has been extensively evaluated in appreciation of the ultimate need to obtain organs from MHC-mismatched unrelated donors.

Results

Nonmyeloablative conditioning regimens have been shown to be successful in inducing immune tolerance across all three animal models. Postgrafting immunosuppression is also important in assuring sustained donor hematopoiesis for tolerance. Donor chimerism need not be permanent to establish stable engraftment of donor organs, thereby essentially eliminating the risk of GVHD. Using nonmyeloablative HCT with monoclonal antibody immunosuppression, the kidney has been successfully transplanted in MHC-mismatched nonhuman primates.

Conclusions

Nonmyeloablative HCT for the establishment of temporary mixed chimerism has led to the establishment of stable tolerance against solid organ allografts in large animal models. The kidney, considered a tolerogenic organ, has been successfully transplanted in the clinic. Other organs such as heart, lung, and vascularized composite allografts (face and hands), remain distant possibilities. Further study in large animal models will be required to improve tolerance against these organs before success can be attained in the clinic.

Fetal stem cell and gene therapy

Advances in our understanding of stem cells, gene editing, prenatal imaging and fetal interventions have opened up new opportunities for the treatment of congenital diseases either through in-utero stem cell transplantation or in-utero gene therapy. Improvements in ultrasound-guided access to the fetal vasculature have also enhanced the safety and efficacy of cell delivery. The fetal environment offers accessible stem cell niches, localized cell populations with large proliferative potential, and an immune system that is able to acquire donor-specific tolerance. In-utero therapy seeks to take advantage of these factors and has the potential to cure diseases prior to the onset of symptoms, a strategy that offers substantial social and economic benefits. In this article, we examine previous studies in animal models as well as clinical attempts at in-utero therapy. We also discuss the barriers to successful in-utero therapy and future strategies for overcoming these obstacles.

In utero stem cell transplantation and gene therapy: Recent progress and the potential for clinical application

Advances in prenatal diagnosis have led to the prenatal management and treatment of a variety of congenital diseases. Although surgical treatment has been successfully applied to specific anatomic defects that place the fetus at a risk of death or life-long disability, the indications for fetal surgical intervention have remained relatively limited. By contrast, prenatal stem cell and gene therapy await clinical application, but they have tremendous potential to treat a broad range of genetic disorders. If there are biological advantages unique to fetal development that favor fetal stem cell or gene therapy over postnatal treatment, prenatal therapy may become the preferred approach to the treatment of any disease that can be prenatally diagnosed and cured by stem cell or gene therapy. Here, we review the field including recent progress toward clinical application and imminent clinical trials for cellular and gene therapy.

Stable long-term mixed chimerism achieved in a canine model of allogeneic in utero hematopoietic cell transplantation

Optimization of IUHCT in a preclinical canine model yields stable long-term donor engraftment. Clinically significant levels of chimerism can be achieved without conditioning, immunosuppression, or graft-versus-host disease.

Stem cell and genetic therapies for the fetus

The prenatal diagnosis and management of congenital disease has made significant progress over the previous decade. Currently, fetal therapy (including open surgery and fetoscopic intervention) provides therapeutic options for a range of congenital anomalies; however, it is restricted to the treatment of fetal pathophysiology. Improvements in prenatal screening and the early diagnosis of genetic disease allow for preemptive treatment of anticipated postnatal disease by stem cell or genetic therapy. While currently awaiting clinical application, in utero stem cell therapy has made significant advances in overcoming the engraftment and immunologic barriers in both murine and pre-clinical large animal models. Likewise, proof in principle for fetal gene therapy has been demonstrated in rodent and large animal systems as a method to prevent the onset of inherited genetic disease; however, safety and ethical risks still need to be addressed prior to human application. In this review, we examine the current status and future direction of stem cell and genetic therapy for the fetus.

Stem cell and genetic therapies for the fetus

Advances in prenatal diagnosis have led to the prenatal management of a variety of congenital diseases. Although prenatal stem cell and gene therapy await clinical application, they offer tremendous potential for the treatment of many genetic disorders. Normal developmental events in the fetus offer unique biologic advantages for the engraftment of hematopoietic stem cells and efficient gene transfer that are not present after birth. Although barriers to hematopoietic stem cell engraftment exist, progress has been made and preclinical studies are now underway for strategies based on prenatal tolerance induction to facilitate postnatal cellular transplantation. Similarly, in-utero gene therapy shows experimental promise for a host of diseases and proof-in-principle has been demonstrated in murine models, but ethical and safety issues still need to be addressed. Here we review the current status and future potential of prenatal cellular and genetic therapy.

Five decades of progress in haematopoietic cell transplantation based on the preclinical canine model

The preclinical canine model has proved valuable for the development of principles and techniques of haematopoietic cell transplantation (HCT) applicable to human patients. Studies in random-bred dogs concerning the impact of histocompatibility barriers on engraftment and graft-versus-host disease, the kinetics of immunological reconstitution, the efficacy of various pretransplant conditioning regimens, post-transplantation immunosuppression protocols, treatment of malignant diseases, and graft-versus-tumour effects have advanced HCT from an investigational therapy with uncertain clinical benefit half a century ago to an important treatment choice for thousands of patients treated annually in transplantation centres worldwide. More recent preclinical canine studies have resulted in the clinical translation of non-myeloablative, minimally invasive transplantation protocols that have extended allogeneic HCT to include older human patients with malignant and non-malignant, acquired or inherited haematological disorders, and those with comorbid conditions. Here, we review the contributions of the canine model to modern HCT and describe the usefulness of HCT for the treatment of canine haematological disorders.

Haploidentical in utero hematopoietic cell transplantation improves phenotype and can induce tolerance for postnatal same-donor transplants in the canine leukocyte adhesion deficiency model

In the murine model, in utero hematopoietic cell transplantation (IUHCT) has been shown to achieve low levels of allogeneic chimerism and associated donor-specific tolerance permitting minimal conditioning postnatal hematopoietic stem cell transplantation (HSCT). In this pilot study, we investigated IUHCT in the canine leukocyte adhesion deficiency (CLAD) model. Haploidentical IUHCT resulted in stable low-level donor cell chimerism in all dogs that could be analyzed by sensitive detection methodology (4 of 10) through 18 months of follow-up. In the 2 CLAD recipients, low-level chimerism resulted in amelioration and complete reversal of the CLAD phenotype, respectively. Six recipients of IUHCT (5 carriers and 1 CLAD) subsequently received postnatal HSCT from the same haploidentical prenatal donor after minimal conditioning with busulfan 10 mg/kg. Chimerism in 2 of 5 CLAD carriers that underwent HSCT increased from < 1% pre-HSCT to sustained levels of 35% to 45%. Control animals undergoing postnatal haploidentical HSCT without IUHCT had no detectable donor chimerism. These results demonstrate that haploidentical IUHCT in the CLAD model can result in low-level donor chimerism that can prevent the lethal phenotype in CLAD dogs, and can result in donor-specific tolerance that can facilitate postnatal minimal conditioning HSCT.

Prenatal stem cell transplantation and gene therapy

At the present time, the most likely and eminent application of stem cell therapy to the fetus is in utero hematopoietic stem cell transplantation (IUHCT), and this stem cell type will be discussed as a paradigm for all prenatal stem cell therapy. The authors feel that the most likely initial application of IUHCT will use adult HSC derived from bone marrow (BM) or peripheral blood (PB), and will focus this article on this specific approach. The article also reviews the experimental data that support the capacity of IUHCT to induce donor-specific tolerance.

Denileukin diftitox as prophylaxis against graft-versus-host disease in the canine hematopoietic cell transplantation model

Denileukin diftitox (Ontak) was evaluated in combination with methotrexate (MTX) for preventing acute graft-versus-host disease (GVHD) in dogs given 9.2 Gy of total body irradiation and DLA-nonidentical hematopoietic cell grafts. Six dogs were given denileukin diftitox 9 ,microg/kg/day intravenously (IV) on days 2, 4, 5, 7, 8, and 10, in combination with MTX 0.4 mg/kg/day IV on days 1, 3, 6, and 11 after transplantation. Median survival of the dogs given MTX in combination with denileukin diftitox was 16 days (range, 13-18 days), similar to that of 35 historical controls given MTX alone (median survival, 20 days). Five of the 6 denileukin diftitox-treated dogs had clinical and pathological evidence of 3-system GVHD; 1 dog died of canine herpes virus infection without evidence of GVHD. In conclusion, denileukin diftitox did not prevent, mitigate, or delay acute GVHD in this stringent and predictive (with respect to outcomes in human patients) hematopoietic cell transplantation model.

Correction of the disease phenotype in canine leukocyte adhesion deficiency using ex vivo hematopoietic stem cell gene therapy

Canine leukocyte adhesion deficiency (CLAD) represents the canine counter-part of the human disease leukocyte adhesion deficiency (LAD). Defects in the leukocyte integrin CD18 adhesion molecule in both CLAD and LAD lead to recurrent, life-threatening bacterial infections. We evaluated ex vivo retroviral-mediated gene therapy in CLAD using 2 nonmyeloablative conditioning regimens--200 cGy total body irradiation (TBI) or 10 mg/kg busulfan--with or without posttransplantation immunosuppression. In 6 of 11 treated CLAD dogs, therapeutic levels of CD18(+) leukocytes were achieved. Conditioning with either TBI or busulfan allowed long-term engraftment, and immunosuppression was not required for efficacy. The percentage of CD18(+) leukocytes in the peripheral blood progressively increased over 6 to 8 months after infusion to levels ranging from 1.26% to 8.37% at 1-year follow-up in the 6 dogs. These levels resulted in reversal or moderation of the severe CLAD phenotype. Linear amplification-mediated polymerase chain reaction assays indicated polyclonality of insertion sites. These results describe ex vivo hematopoietic stem cell gene transfer in a disease-specific, large animal model using 2 clinically applicable conditioning regimens, and they provide support for the use of nonmyeloablative conditioning regimens in preclinical protocols of retroviral-mediated gene transfer for nonmalignant hematopoietic diseases such as LAD.

RDP58 does not prevent graft-versus-host disease after dog leukocyte antigen-nonidentical canine hematopoietic cell transplantation

Graft-versus-host disease (GVHD) remains a cause of substantial morbidity for patients undergoing allogeneic hematopoietic cell transplantation (HCT). The present study was undertaken to investigate the effectiveness of RDP58, a peptide derived from the human leukocyte antigen class I heavy chain, in preventing GVHD in the established dog leukocyte antigen (DLA)-nonidentical canine model. Dogs underwent HCT from unrelated DLA-nonidentical donors after conditioning with 920 cGy total body irradiation. Engraftment and achievement of full donor chimerism was seen in five of six dogs, whereas one dog showed rejection and died of marrow aplasia. All five dogs with engraftment developed acute GVHD and were euthanized at an average of 20.6 days after HCT. Compared with historical controls, the Suse of RDP58 neither prevented acute GVHD nor significantly prolonged survival of DLA-nonidentical HCT recipients.

Frequency and distribution of alleles of canine MHC-II DLA-DQB1, DLA-DQA1 and DLA-DRB1 in 25 representative American Kennel Club breeds

The frequency and distribution of dog leucocyte antigens (DLA) class II -DQA1, -DQB1 and -DRB1 alleles were determined for 25 American Kennel Club (AKC) registered dog breeds, representing 360 dogs from each of the seven major performance categories. Six to twenty-eight (average n=11) dogs were studied per group, with the exception of the Akita dog (n=94). All dogs were unrelated with no common grandparents based on AKC pedigree records (F-value <0.125). DLA class II allelic diversity was broad across breeds; 31/61 published DLA-DRB1 alleles, 11/18 published DLA-DQA1 alleles and 31/47 published DLA-DQB1 alleles were found among the 25 breeds. However, allelic diversity was severely limited within a breed. Seventeen of the DLA-DRB1 alleles were each found in only a single breed, and only seven alleles were shared by seven or more breeds. DLA-DRB1*00101 and DLA-DRB1*01501 were shared by 16 and 19 breeds, respectively. DLA-DQA1*00101 and DLA-DQA1*00601 alleles were shared by many breeds. The Rough Collie (DLA-DQA1*00901), English Setter (DLA-DQA1*00101) and Scottish Terrier (DLA-DQA1*00101) were monoallelic for DLA-DQA1. Eleven DLA-DQB1 alleles were each found only in a single breed and only seven alleles were shared by six or more breeds. DLA-DQB1*00201 and DLA-DQB1*02301 were shared by 17 and 18 breeds, respectively. Forty per cent of dogs typed were homozygous at DLA-DRB1, 52% at DLA-DQA1 and 44% at DLA-DQB1. Nine new DLA class II alleles were identified; three for DRB1 and six for DQB1. Comparison of our study of North American purebred dogs to previous European DLA surveys showed a similar use of common alleles consistent with known founder effects. However, more alleles were detected in European breeds, compared to their North American descendents, indicating that additional DLA class II diversity was lost when European breeds were established in North America.

Leukocyte adhesion deficiency in children and Irish setter dogs

Children with the genetic immunodeficiency disease leukocyte adhesion deficiency, or LAD, develop life-threatening bacterial infections as a result of the inability of their leukocytes to adhere to the vessel wall and migrate to the sites of infection. Recently, the canine counterpart to LAD, known as canine leukocyte adhesion deficiency, or CLAD, has been described in Irish setter dogs. This review describes how the clinical phenotype of dogs with CLAD closely parallels that of children with the severe deficiency phenotype of LAD, thus enabling the CLAD dog to provide a disease-specific, large-animal model for testing novel hematopoietic stem cell and gene therapy strategies before their translation to children with LAD.

FTY720 does not abrogate acute graft-versus-host disease in the dog leukocyte antigennonidentical unrelated canine model1

BACKGROUND

Acute graft-versus-host disease (GVHD) remains a significant impediment to successful hematopoietic stem-cell transplantation (HSCT). Here, we examined the effectiveness of 2-amino-2-(2-[4-octylphenyl]ethyl)-1,3-propanediol hydrochloride (FTY720), an immunosuppressant that retraffics activated lymphocytes to secondary lymphoid organs, for the treatment of acute GVHD in an established dog leukocyte antigen-nonidentical unrelated canine HSCT model.

METHODS

Dogs were given HSCT after conditioning with 920 cGy total body irradiation. The dogs received methotrexate 0.4 mg/kg/day on days 1, 3, 6, and 11 and FTY720 (5 mg/kg/day orally) after developing GVHD.

RESULTS

Five of six dogs achieved engraftment, developed acute GVHD, and were treated with FTY720. FTY720 resulted in a profound decrease in lymphocytes and a temporary mitigation of clinical GVHD; however, GVHD recurred in all dogs. Four of five dogs were euthanized because of severe GVHD and the fifth because of severe inanition associated with moderate GVHD.

CONCLUSIONS

Compared with controls, treatment of GVHD with FTY720 did not control this complication or significantly increase survival.

Postgrafting immunosuppression with sirolimus and cyclosporine facilitates stable mixed hematopoietic chimerism in dogs given sublethal total body irradiation before marrow transplantation from DLA-identical littermates

We studied the value of postgrafting immunosuppression with sirolimus (SRL) and cyclosporine (CSP) in enhancing engraftment of dog leukocyte antigen-identical littermate marrow after nonmyeloablative conditioning in a canine model. Dogs received either 2 Gy (n=7) or 1 Gy (n=5) total body irradiation (TBI), followed by postgrafting immunosuppression with SRL and CSP. In the first cohort, all 7 dogs showed rapid initial engraftment. One engrafted dog died on day 21 due to hemorrhagic pneumonitis. Durable engraftment was seen in 5 of 6 remaining dogs, with a median follow-up of >48 (range, >32 to >56) weeks. The sixth dog rejected the marrow graft (as assessed by variable number of tandem repeats) at 11 weeks; however, a subsequent skin graft from the same marrow donor did not undergo acute cellular rejection, suggesting donor-specific tolerance. In the second cohort, all 5 dogs rejected the marrow graft at a median of 9 weeks (range, 3-11 weeks). We conclude that SRL/CSP is as effective as a previously studied combination of mycophenolate mofetil and CSP at establishing durable marrow engraftment after sublethal conditioning.

Sirolimus (rapamycin) for the treatment of steroid-refractory acute graft-versus-host disease

BACKGROUND

In a pilot trial we evaluated the toxicity and efficacy of sirolimus (rapamycin) as second-line therapy for the treatment of acute graft-versus-host disease (GVHD) in 21 patients (1-46 years of age) after allogeneic hematopoietic stem cell transplantation (HSCT).

METHODS

All patients were treated with methylprednisolone at 2 mg/kg/day, but failed to respond satisfactorily. Sirolimus was started 19-78 (median 37) days after HSCT when 10 patients had grade III and 11 had grade IV GVHD. The first four patients received a loading dose (15 mg/m2) of oral sirolimus on day 1 followed by 5 mg/m2/day for 13 days. The next 17 patients received either 5 (n=7) or 4 (n=10) mg/m2/day for 14 days without a loading dose. Eleven patients completed the 14-day sirolimus course. Five patients were treated for 9-13 days, two for 6 days, and three for 1-3 days.

RESULTS

Sirolimus was discontinued early in 10 patients because of lack of improvement in GVHD (n=5), myelosuppression (n=2), seizure (n=2), and attending physician preference (n=1). The most common and significant adverse events were thrombocytopenia (n=7) and neutropenia (n=4). Other side effects included increased blood triglycerides (n=8) and cholesterol (n=3). Five patients had evidence of a hemolytic uremic syndrome concurrently with or after sirolimus treatment. Eighteen of the 21 patients received 6 or more doses of sirolimus and 12 responded, 5 with complete and 7 with partial responses. Six of the 12 responders (28% of all patients enrolled) and 1 nonresponder are currently alive at 400-907 days after HSCT, 3 with chronic GVHD. Fourteen of the 21 patients (66%) died 40-263 days after transplant.

CONCLUSION

These data suggest that sirolimus has activity in the treatment of steroid-refractory acute GVHD. However, there was considerable toxicity and further dose optimization studies seem warranted.