Leukocyte adhesion deficiency in children and Irish setter dogs

Gene therapy for primary immune deficiencies: a Canadian perspective

The use of gene therapy (GT) for the treatment of primary immune deficiencies (PID) including severe combined immune deficiency (SCID) has progressed significantly in the recent years. In particular, long-term studies have shown that adenosine deaminase (ADA) gene delivery into ADA-deficient hematopoietic stem cells that are then transplanted into the patients corrects the abnormal function of the ADA enzyme, which leads to immune reconstitution. In contrast, the outcome was disappointing for patients with X-linked SCID, Wiskott-Aldrich syndrome and chronic granulomatous disease who received GT followed by autologous gene corrected transplantations, as many developed hematological malignancies. The malignancies were attributed to the predilection of the viruses used for gene delivery to integrated at oncogenic areas. The availability of safer and more efficient self-inactivating lentiviruses for gene delivery has reignited the interest in GT for many PID that are now in various stages of pre-clinical studies and clinical trials. Moreover, advances in early diagnosis of PID and gene editing technology coupled with enhanced abilities to generate and manipulate stem cells ex vivo are expected to further contribute to the benefit of GT for PID. Here we review the past, the present and the future of GT for PID, with particular emphasis on the Canadian perspective.

Clinical effects of bovine lactoferrin on two canine cases with familial neutrophil dysfunction

This study reported detailed clinical effects of bovine lactoferrin on 2 canine littermates (1 female and 1 male) with familial neutrophil dysfunction and an investigation of their genetic background. Clinical signs caused by severe upper respiratory bacterial infections were observed in these dogs. Oral administration of bovine lactoferrin for a long duration improved their clinical signs (severe uveitis in the female dog and coughing from pneumonia in the male dog). Their backcross dogs that have the same father didn't show clinical signs of bacterial infection. Neutrophil function tests revealed that the backcross dogs didn't have any disorders. It is likely that abnormal clinical signs are associated with neutrophil dysfunction in the colony, and the mother dog of these cases might be the genetic carrier of this dysfunction.

The function of dog models in developing gene therapy strategies for human health

The domestic dog is of great benefit to humankind, not only through companionship and working activities cultivated through domestication and selective breeding, but also as a model for biomedical research. Many single-gene traits have been well-characterized at the genomic level, and recent advances in whole-genome association studies will allow for better understanding of complex, multigenic hereditary diseases. Additionally, the dog serves as an invaluable large animal model for assessment of novel therapeutic agents. Thus, the dog has filled a crucial step in the translation of basic research to new treatment regimens for various human diseases. Four well-characterized diseases in canine models are discussed as they relate to other animal model availability, novel therapeutic approach, and extrapolation to human gene therapy trials.

Leukocyte count affects expression of reference genes in canine whole blood samples

Background

The dog is frequently used as a model for hematologic human diseases. In this study the suitability of nine potential reference genes for quantitative RT-PCR studies in canine whole blood was investigated.

Findings

The expression of these genes was measured in whole blood samples of 263 individual dogs, representing 73 different breeds and a group of 40 mixed breed dogs, categorized into healthy dogs and dogs with internal and hematological diseases, and dogs that underwent a surgical procedure. GeNorm analysis revealed that a combination of 5 to 6 of the most stably expressed genes constituted a stable normalizing factor. Evaluation of the expression revealed different ranking of reference genes in Normfinder and GeNorm. The disease category and the white blood cell count significantly affected reference gene expression.

Conclusions

The discrepancy between the ranking of reference genes in this study by Normfinder and Genorm can be explained by differences between the experimental groups such as "disease category" and "WBC count". This stresses the importance of assessing the expression stability of potential reference genes for gene experiments in canine whole blood anew for each specific experimental condition.

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.

Development and use of DNA archives at veterinary teaching hospitals to investigate the genetic basis of disease in dogs

The DNA archives developed at veterinary medical teaching hospitals will be important resources for mapping disease loci and identifying underlying genes. The most important feature of a DNA archive is accurate identification or exclusion of diseases in each animal. Such archives will be complimentary resources to tissue banks that are currently available.

Canine neutrophil dysfunction caused by downregulation of beta2-integrin expression without mutation

Canine leukocyte adhesion deficiency (CLAD) in Irish setters is caused by genetic defects of leukocyte integrin CD18 leading to recurrent bacterial infections. We report clinical features and analysis of neutrophil function from two mixed-breed canine littermates (one female and one male dog) similar to CLAD. The symptoms of pyogenic infection were first recognized at 3 months of age and since then the patients suffered from recurrent bacterial infections. These clinical findings were strongly suggestive of genetic phagocyte dysfunction. Neutrophil function tests revealed a marked reduction of serum-opsonized zymosan-mediated superoxide production in the two littermates. Neutrophils of the male dog revealed impaired integrin-mediated adherence and phagocytic activity, whereas ability of serum opsonization was normal. There was also a profound decrease of surface expression of CD11b/CD18 and beta2-integrin transcript level, detected by real-time RT-PCR without missense mutations unlike CLAD. Immunoblot analysis indicated that protein expression of cytochrome b(558) component gp91(phox), the cytosolic components p47(phox) and p67(phox) of NADPH oxidase components increased profoundly in the male. Our study suggests that decreased transcriptional levels of beta2-integrin without mutations, lead to downregulation of surface expression, resulting in multiple defects in adhesion-related neutrophil functions and consequently, recurrent bacterial infections from puppyhood.

Genetics, biology and clinical management of myeloid cell primary immune deficiencies: chronic granulomatous disease and leukocyte adhesion deficiency

PURPOSE OF REVIEW

Chronic granulomatous disease and leukocyte adhesion deficiency are the major primary immune deficiencies affecting phagocytic blood cells. Major advances in clinical diagnosis and development of novel treatments for these disorders merit review.

RECENT FINDINGS

Clinically beneficial gene therapy correction of X-linked chronic granulomatous disease in two adult patients was reported. Nonmyeloablative busulfan conditioning before administration of gene corrected autologous hematopoietic stem cells was likely an essential maneuver to achieve successful gene therapy. There is an increased association of autoimmune disorders with chronic granulomatous disease. Preimplantation genetic diagnosis of leukocyte adhesion deficiency-I led to the birth of a normal child. A canine model of leukocyte adhesion deficiency-I facilitated development of new nonmyeloablative hematopoietic stem cell transplant and gene therapy approaches to leukocyte adhesion deficiency. Nonmyeloablative transplantation may provide an effective, but less toxic approach for leukocyte adhesion deficiency in children. There have been advances in understanding the basis of leukocyte adhesion deficiency-II and III.

SUMMARY

The most important subjects reviewed in this chapter include new advances in development of gene therapy for chronic granulomatous disease and leukocyte adhesion deficiency-I; transplantation for leukocyte adhesion deficiency-I; prenatal diagnosis of leukocyte adhesion deficiency-I; and association of autoimmune diseases with chronic granulomatous disease.

Genetic medicines: treatment strategies for hereditary disorders

The treatment of the more than 1,800 known monogenic hereditary disorders will depend on the development of 'genetic medicines' - therapies that use the transfer of DNA and/or RNA to modify gene expression to correct or compensate for an abnormal phenotype. Strategies include the use of somatic stem cells, gene transfer, RNA modification and, in the future, embryonic stem cells. Despite the efficacy of these technologies in treating experimental models of hereditary disorders, applying them successfully in the clinic is a great challenge, which will only be overcome by expending considerable intellectual and economic resources, and by solving societal concerns about modifications of the human genetic repertoire.

Nonmyeloablative conditioning with busulfan before matched littermate bone marrow transplantation results in reversal of the disease phenotype in canine leukocyte adhesion deficiency

Leukocyte adhesion deficiency (LAD)-1, a primary immunodeficiency disease caused by molecular defects in the leukocyte integrin CD18 molecule, is characterized by recurrent, life-threatening bacterial infections. Myeloablative hematopoietic stem cell transplantation is the only curative treatment for LAD-1. Recently, canine LAD (CLAD) has been shown to be a valuable animal model for the preclinical testing of nonmyeloablative transplantation regimens for the treatment of children with LAD-1. To develop new allogeneic transplantation approaches for LAD-1, we assessed a nonmyeloablative conditioning regimen consisting of busulfan as a single agent before matched littermate allogeneic bone marrow transplantation in CLAD. Three CLAD dogs received busulfan 10 mg/kg intravenously before infusion of matched littermate bone marrow, and all dogs received posttransplantation immunosuppression with cyclosporin A and mycophenolate mofetil. Initially, all 3 dogs became mixed chimeras, and levels of donor chimerism sufficient to reverse the CLAD phenotype persisted in 2 animals. The third dog maintained donor microchimerism with an attenuated CLAD phenotype. These 3 dogs have all been followed up for at least 1 year after transplantation. These results indicate that a nonmyeloablative conditioning regimen with chemotherapy alone is capable of generating stable mixed chimerism and reversal of the disease phenotype in CLAD.

Phagocyte immunodeficiencies and their infections

Primary immunodeficiencies (PIDs) primarily affecting the phagocytes (neutrophils and macrophages) typically predispose patients to infections. However, one of the most clinically important features of these disorders is their relatively narrow spectrum of disease-specific infections. Invasive aspergillosis in the absence of immune suppression is essentially seen only in chronic granulomatous disease; disseminated nontuberculous mycobacterial infection in the absence of immune suppression is seen predominantly in patients with defects of the IFN-gamma/IL-12 axis. In contrast, infections that are relatively common in some of the PIDs affecting the lymphoid system (Pneumocystis jiroveci and Streptococcus pneumoniae) are extremely uncommon in PIDs affecting phagocytes. Therefore careful attention to the microbiology laboratory early in the course of evaluation of a patient with recurrent infections and suspected of having a PID will help steer the workup in the appropriate direction. Over the last few years, there have been major advances in the molecular and cellular understandings of PIDs affecting phagocytes. As the field of PIDs becomes broader and more clinical and molecular definition becomes available, it is increasingly important to be able to identify likely pathways for investigation early in the evaluation. Here we have updated some of the more rapidly evolving aspects of PIDs affecting phagocytes, with a special emphasis on the associated microbiology.