Identification of novel polymorphisms and two distinct haplotype structures in dog leukocyte antigen class I genes: DLA-88, DLA-12 and DLA-64

A review of CD4+ T cell differentiation and diversity in dogs

CD4+ T cells are an integral component of the adaptive immune response, carrying out many functions to combat a diverse range of pathogenic challenges. These cells exhibit remarkable plasticity, differentiating into specialized subsets such as T helper type 1 (TH1), TH2, TH9, TH17, TH22, regulatory T cells (Tregs), and follicular T helper (TFH) cells. Each subset is capable of addressing a distinct immunological need ranging from pathogen eradication to regulation of immune homeostasis. As the immune response subsides, CD4+ T cells rest down into long-lived memory phenotypes-including central memory (TCM), effector memory (TEM), resident memory (TRM), and terminally differentiated effector memory cells (TEMRA) that are localized to facilitate a swift and potent response upon antigen re-encounter. This capacity for long-term immunological memory and rapid reactivation upon secondary exposure highlights the role CD4+ T cells play in sustaining both adaptive defense mechanisms and maintenance. Decades of mouse, human, and to a lesser extent, pig T cell research has provided the framework for understanding the role of CD4+ T cells in immune responses, but these model systems do not always mimic each other. Although our understanding of pig immunology is not as extensive as mouse or human research, we have gained valuable insight by studying this model. More akin to pigs, our understanding of CD4+ T cells in dogs is much less complete. This disparity exists in part because canine immunologists depend on paradigms from mouse and human studies to characterize CD4+ T cells in dogs, with a fraction of available lineage-defining antibody markers. Despite this, every major CD4+ T cell subset has been described to some extent in dogs. These subsets have been studied in various contexts, including in vitro stimulation, homeostatic conditions, and across a range of disease states. Canine CD4+ T cells have been categorized according to lineage-defining characteristics, trafficking patterns, and what cytokines they produce upon stimulation. This review addresses our current understanding of canine CD4+ T cells from a comparative perspective by highlighting both the similarities and differences from mouse, human, and pig CD4+ T cell biology. We also discuss knowledge gaps in our current understanding of CD4+ T cells in dogs that could provide direction for future studies in the field.

Dog leukocyte antigen genotyping across class I and class II genes in beagle dogs as laboratory animals

Dog leukocyte antigen (DLA) polymorphisms have been found to be associated with inter-individual variations in the risk, susceptibility, and severity of immune-related phenomena. While DLA class II genes have been extensively studied, less research has been performed on the polymorphisms of DLA class I genes, especially in beagle dogs commonly used as laboratory animals for safety evaluations in drug development. We genotyped four DLA class I genes and four DLA class II genes by locus-specific Sanger sequencing using 93 laboratory beagle dogs derived from two different strains: TOYO and Marshall. The results showed that, for DLA class I genes, 11, 4, 1, and 2 alleles, including a novel allele, were detected in DLA-88, DLA-12/88L, DLA-64, and DLA-79, while, for DLA class II genes, 1, 10, 6, and 7 alleles were detected in DLA-DRA, DLA-DRB1, DLA-DQA1, and DLA-DQB1, respectively. It was estimated that there were 14 DLA haplotypes, six of which had a frequency of ≥ 5%. Furthermore, when comparing the DLA diversity between TOYO and Marshall strains, the most common alleles and haplotypes differed between them. This is the first study to genotype all DLA loci and determine DLA haplotypes including all DLA class I and class II genes in dogs. Integrating information on the DLA diversity of laboratory beagle dogs should reinforce their benefit as an animal model for understanding various diseases associated with a specific DLA type.

Leading the pack: Best practices in comparative canine cancer genomics to inform human oncology

Pet dogs develop spontaneous cancers at a rate estimated to be five times higher than that of humans, providing a unique opportunity to study disease biology and evaluate novel therapeutic strategies in a model system that possesses an intact immune system and mirrors key aspects of human cancer biology. Despite decades of interest, effective utilization of pet dog cancers has been hindered by a limited repertoire of necessary cellular and molecular reagents for both in vitro and in vivo studies, as well as a dearth of information regarding the genomic landscape of these cancers. Recently, many of these critical gaps have been addressed through the generation of a highly annotated canine reference genome, the creation of several tools necessary for multi-omic analysis of canine tumours, and the development of a centralized repository for key genomic and associated clinical information from canine cancer patients, the Integrated Canine Data Commons. Together, these advances have catalysed multidisciplinary efforts designed to integrate the study of pet dog cancers more effectively into the translational continuum, with the ultimate goal of improving human outcomes. The current review summarizes this recent progress and provides a guide to resources and tools available for comparative study of pet dog cancers.

Crystal Structure of a Classical MHC Class I Molecule in Dogs; Comparison of DLA-88*0 and DLA-88*5 Category Molecules

DLA-88 is a classical major histocompatibility complex (MHC) class I gene in dogs, and allelic DLA-88 molecules have been divided into two categories named "DLA-88*0" and "DLA-88*5." The defining difference between the two categories concerns an LQW motif in the α2 domain helical region of the DLA-88*5 molecules that includes the insertion of an extra amino acid compared to MHC class I consensus length. We here show that this motif has been exchanged by recombination between different DLA-88 evolutionary lineages. Previously, with pDLA-88*508:01, the structure of a molecule of the DLA-88*5 category was elucidated. The present study is the first to elucidate a structure, using X-ray crystallography, of the DLA-88*0 category, namely DLA-88*001:04 complexed with β2m and a nonamer peptide derived from canine distemper virus (CDV). The LQW motif that distinguishes DLA-88*5 from DLA-88*0 causes a shallower peptide binding groove (PBG) and a leucine exposed at the top of the α2 domain helix expected to affect T cell selection. Peptide ligand amino acid substitution and pMHC-I complex formation and stability analyses revealed that P2 and P3 are the major anchor residue positions for binding to DLA-88*001:04. We speculate that the distribution pattern of the LQW motif among canine classical MHC class I alleles represents a strategy to enhance allogeneic rejection by T cells of transmissible cancers such as canine transmissible venereal tumor (CTVT).

Large-Scale Polymorphism Analysis of Dog Leukocyte Antigen Class I and Class II Genes (DLA-88, DLA-12/88L and DLA-DRB1) and Comparison of the Haplotype Diversity between Breeds in Japan

Polymorphisms of canine leukocyte antigen (DLA) class I (DLA-88 and DLA-12/88L) and class II (DLA-DRB1) genes are important for disease susceptibility studies, but information on the genetic diversity among dog breeds is still lacking. To better elucidate the polymorphism and genetic diversity between breeds, we genotyped DLA-88, DLA-12/88L, and DLA-DRB1 loci using 829 dogs of 59 breeds in Japan. Genotyping by Sanger sequencing identified 89, 43, and 61 alleles in DLA-88, DLA-12/88L, and DLA-DRB1 loci, respectively, and a total of 131 DLA-88-DLA-12/88L-DLA-DRB1 haplotypes (88-12/88L-DRB1) were detected more than once. Of the 829 dogs, 198 were homozygotes for one of the 52 different 88-12/88L-DRB1 haplotypes (homozygosity rate: 23.8%). Statistical modeling suggests that 90% of the DLA homozygotes or heterozygotes with one or other of the 52 different 88-12/88L-DRB1 haplotypes within somatic stem cell lines would benefit graft outcome after 88-12/88L-DRB1-matched transplantation. As previously reported for DLA class II haplotypes, the diversity of 88-12/88L-DRB1 haplotypes varied remarkably between breeds but was relatively conserved within most breeds. Therefore, the genetic characteristics of high DLA homozygosity rate and poor DLA diversity within a breed are useful for transplantation therapy, but they may affect biological fitness as homozygosity progresses.

A Kmer-based paired-end read de novo assembler and genotyper for canine MHC class I genotyping

The major histocompatibility complex class I (MHC-I) genes are highly polymorphic. MHC-I genotyping is required for determining the peptide epitopes available to an individual's T-cell repertoire. Current genotyping software tools do not work for the dog, due to very limited known canine alleles. To address this, we developed a Kmer-based paired-end read (KPR) de novo assembler and genotyper, which assemble paired-end RNA-seq reads from MHC-I regions into contigs, and then genotype each contig and estimate its expression level. KPR tools outperform other popular software examined in typing new alleles. We used KPR tools to successfully genotype152 dogs from a published dataset. The study discovers 33 putative new alleles, finds dominant alleles in 4 dog breeds, and builds allele diversity and expression landscapes among the 152 dogs. Our software meets a significant need in biomedical research.

Dog leukocyte antigen class II alleles and haplotypes associated with meningoencephalomyelitis of unknown origin in Chihuahuas

Idiopathic non-infectious meningoencephalomyelitis (NIME), which is thought to be an immune-mediated disease, is a common inflammatory disease in dogs. Meningoencephalomyelitis of unknown origin (MUO), a subgroup of NIME, consists of necrotizing meningoencephalitis (NME), necrotizing leukoencephalitis, and granulomatous meningoencephalomyelitis. Recent studies have shown associations between disease development and dog leukocyte antigen (DLA) class II genes in NME in Pugs and in NIME in Greyhounds. This study focused on Chihuahuas, which have a high incidence of MUO and are one of the most common dog breeds in Japan. Because the development of MUO seems to be associated with DLA class II genes, we aimed to evaluate the association between DLA class II genes and MUO development in Chihuahuas. Blood samples were obtained from 22 Chihuahuas with MUO (MUO group) and 46 without neurological diseases (control). The allele sequences of three DLA class II loci were determined, and haplotypes were estimated from these data. In total, 23 haplotypes were detected. The frequency of one haplotype (DLA-DRB1*015:01--DQA1*006:01--DQB1*023:01) was significantly higher in the MUO group than in the control group (odds ratio, 7.11; 95% confidence interval, 1.37-36.81; P=0.0141). The results suggest that the development of MUO in Chihuahuas may be associated with DLA class II genes. Because the identified risk haplotypes differed from those of other breeds, the pathogenesis of NIME-related diseases may differ among dog breeds.

Genotyping of canine MHC gene DLA-88 by next-generation sequencing reveals high frequencies of new allele discovery and gene duplication

Dogs have served as one of the most reliable preclinical models for a variety of diseases and treatments, including stem/progenitor cell transplantation. At the genetic epicenter of dog transplantation models, polymorphic major histocompatibility complex (MHC) genes are most impactful on transplantation success. Among the canine class I and class II genes, DLA-88 has been best studied in transplantation matching and outcomes, with 129 DLA-88 alleles identified. In this study we developed and tested a next generation (NGS) sequencing protocol for rapid identification of DLA-88 genotypes in dogs and compared the workflow and data generated with an established DLA-88 Sanger sequencing protocol that has been in common prior use for clinical studies. By testing the NGS protocol on a random population of 382 dogs, it was possible to demonstrate superior efficacy based on laboratory execution and overall cost. In addition, NGS proved far more effective at discovering new alleles and detecting multiple alleles associated with gene duplication. A total of 51 new DLA-88 alleles are reported here. This rate of new allele discovery indicates that a large pool of yet un-discovered DLA-88 alleles exists in the domestic dog population. In addition, more than 46% of dogs carried three or more copies of DLA-88, further emphasizing the need for more sensitive and cost-effective DLA typing methodology for the dog clinical model.

Haplotype structures and polymorphisms of dog leukocyte antigen (DLA) class I loci shaped by intralocus and interlocus recombination events

The dog leukocyte antigen (DLA) class I genomic region is located on chromosome 12, and the class I genomic region is composed of at least two distinct haplotypic gene structures, DLA-88-DLA-12 and DLA-88-DLA-88L. However, detailed information of the genomic differences among DLA-88, DLA-12, and DLA-88L are still lacking at the full-length gene level, and therefore, DLA allelic sequences classified for each of these loci are limited in number so far. In this study, we determined the DNA sequence of a 95-kb DLA class I genomic region including DLA-88, DLA-12/88L, and DLA-64 with three DLA homozygous dogs and of 37 full-length allelic gene sequences for DLA-88 and DLA-12/88L loci in 26 DLA class I homozygous dogs. Nucleotide diversity profiles of the 95-kb regions and sequence identity scores of the allelic sequences suggested that DLA-88L is a hybrid gene generated by interlocus and/or intralocus gene conversion between DLA-88 and DLA-12. The putative minimum conversion tract was estimated to be at least an 850-bp segment in length located from the 5´flanking untranslated region to the end of intron 2. In addition, at least one DLA-12 allele (DLA-12*004:01) was newly generated by interlocus gene conversion. In conclusion, the analysis for the occurrence of gene conversion within the dog DLA class I region revealed intralocus gene conversion tracts in 17 of 27 DLA-88 alleles and two of 10 DLA-12 alleles, suggesting that intralocus gene conversion has played an important role in expanding DLA allelic variations.

Epithelial cells remove precancerous cells by cell competition via MHC class I-LILRB3 interaction

Epithelial cells have an ability termed 'cell competition', which is an immune surveillance-like function that extrudes precancerous cells from the epithelial layer, leading to apoptosis and clearance. However, it remains unclear how epithelial cells recognize and extrude transformed cells. Here, we discovered that a PirB family protein, leukocyte immunoglobulin-like receptor B3 (LILRB3), which is expressed on non-transformed epithelial cells, recognizes major histocompatibility complex class I (MHC class I) that is highly expressed on transformed cells. MHC class I interaction with LILRB3 expressed on normal epithelial cells triggers an SHP2-ROCK2 pathway that generates a mechanical force to extrude transformed cells. Removal of transformed cells occurs independently of natural killer (NK) cell or CD8⁺ cytotoxic T cell-mediated activity. This is a new mechanism in that the immunological ligand-receptor system generates a mechanical force in non-immune epithelial cells to extrude precancerous cells in the same epithelial layer.

An evaluation of allogeneic freeze-dried concentrated growth factors biocompatibilityin vitroandin vivo

This study evaluated the biocompatibility of allogeneic freeze-dried concentrated growth factors (AFD-CGFs)in vitroandin vivo.For thein vitroexperiments, bone marrow stem cells (BMSCs) were cultured in 10% fresh allogeneic concentrated growth factors (CGFs). AFD-CGF solution was used as the experimental group, and Dulbecco's modified Eagle medium was used as control. Transmission electron microscopy (TEM) showed that the cell ultrastructure was unchanged, and membranes were intact. Scanning electron microscopy, cell counting kit-8, and quantitative polymerase chain reaction indicated that BMSCs and differentiation were unchanged between AFD-CGFs versus control groups (allp> 0.05). Alkaline phosphatase activity was higher in CGF groups (peaked at 14 d) than in the control group. Regarding thein vivoexperiments, four beagles were used for surgery and the rest as controls. Beagles were sacrificed at 2 weeks to observe acute response and membrane absorption; at 12 weeks for wound healing and chronic damage to the liver. According to general observations and histology, the CGFs of all groups were absorbed 2 weeks afterin vivoimplantation. No sign of intolerance was observed. Histology showed a slight increase in immune cells appearing in the implantation area after 2 weeks. However, no or very few inflammatory and immune cells were detected 3 months after the operation. Based on the hematoxylin and eosin staining and TEM results, the ultrastructure of the liver tissue was unchanged. In general, the results suggest that AFD-CGFs are biocompatible and may be a promising option for tissue healing.

Immunosuppression-enhancing effect of the administration of allogeneic canine adipose-derived mesenchymal stem cells (cA-MSCs) compared with autologous cA-MSCs in vitro

Background

Recently, mesenchymal stem cells therapy has been performed in dogs, although the outcome is not always favorable.

Objectives

To investigate the therapeutic efficacy of mesenchymal stem cells (MSCs) using dog leukocyte antigen (DLA) matching between the donor and recipient in vitro.

Methods

Canine adipose-derived MSCs (cA-MSCs) isolated from the subcutaneous tissue of Dog 1 underwent characterization. For major DLA genotyping (DQA1, DQB1, and DRB1), peripheral blood mononuclear cells (PBMCs) from two dogs (Dogs 1 and 2) were analyzed by direct sequencing of polymerase chain reaction (PCR) products. The cA-MSCs were co-cultured at a 1:10 ratio with activated PBMCs (DLA matching or mismatching) for 3 days and analyzed for immunosuppressive (IDO, PTGS2, and PTGES), inflammatory (IL6 and IL10), and apoptotic genes (CASP8, BAX, TP53, and BCL2) by quantitative real-time reverse transcriptase-PCR.

Results

cA-MSCs were expressed cell surface markers such as CD90⁺/44⁺/29⁺/45^- and differentiated into osteocytes, chondrocytes, and adipocytes in vitro. According to the Immuno Polymorphism Database, DLA genotyping comparisons of Dogs 1 and 2 revealed complete differences in genes DQA1, DQB1, and DRB1. In the co-culturing of cA-MSCs and PBMCs, DLA mismatch between the two cell types induced a significant increase in the expression of immunosuppressive (IDO/PTGS2) and apoptotic (CASP8/BAX) genes.

Conclusions

The administration of cA-MSCs matching the recipient DLA type can alleviate the need to regulate excessive immunosuppressive responses associated with genes, such as IDO and PTGES. Furthermore, easy and reliable DLA genotyping technology is required because of the high degree of genetic polymorphisms of DQA1, DQB1, and DRB1 and the low readability of DLA 88.

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.

Dog leukocyte antigen (DLA) class II genotypes associated with chronic enteropathy in French bulldogs and miniature dachshunds

Canine chronic enteropathy (CE) is a group of immunogenetic disorders of unclear etiology characterized by chronic or recurrent gastrointestinal signs and inflammation. Diagnosis of CE subtypes by treatment response is a lengthy and challenging process, particularly in refractory cases of the disease. Given known association of dog leukocyte antigen (DLA) class II genotype and various immunogenetic disorders between and across breeds, this study was designed to examine the potential of determining susceptibility to refractory CE through identification of risk and protective genotypes in French bulldogs and miniature dachshunds-two popular dog breeds in Japan. Sequence-based genotyping of three DLA class II genes in 29 French bulldogs and 30 miniature dachshunds with refractory CE revealed a protective haplotype DLA-DRB1*002:01-DQA1*009:01-DQB1*001:01 against CE in French bulldogs (OR 0.09, 95 % CI 0.01-0.71, p = 0.0084). No statistical difference was noted between miniature dachshund cases and controls. These findings, largely disparate from a previous study on German shepherd dogs in the UK, were taken as possible indication of etiological differences in the refractory CE noted between and within breeds, and by extension, the potential of identifying such disease heterogeneity by DLA typing. The DLA-DQA1/DQB1 haplotype, protective against CE in our French bulldogs, has been reported as protective in various immune-mediated disorders such as Doberman hepatitis (Dyggve et al., 2011). Likewise, the DLA-DRB1*006:01 risk allele for Doberman hepatitis was noted in more French bulldogs with CE compared to controls, in line with reports on genotypes associated with both risk and protection being shared across various autoimmune diseases and breeds. These findings support an immunogenetic basis to the French bulldog-CE in our analysis, calling for further DLA studies working with larger samples and different breeds towards phenotypic clarification that may aid in early diagnosis, treatment, and prophylaxis through epigenetic approaches and breeding.

Evolution of MHC class I genes in Japanese and Russian raccoon dogs, Nyctereutes procyonoides (Carnivora: Canidae)

Major histocompatibility complex (MHC) genes have been widely studied to assess the immunological fitness and evolutionary adaptation of animal populations. Among the Canidae, the raccoon dog's adventurous nature, omnivorous behavior, and high variability of intracellular pathogens make it ideal to study selection on MHC class I in a non-model canid species. Here, we examined allelic diversity and evolutionary patterns of MHC class I genes in the raccoon dog (Nyctereutes procyonoides). We identified 48 novel MHC class I alleles from 31 raccoon dogs from Japan and Russia. Some alleles were geographically restricted, whereas others were widely distributed across the species' range. The rate of non-synonymous substitutions was greater than that of synonymous substitutions for both exon 2 and exon 3 encoding α1 and α2 domains, respectively, in the α chain of the MHC class I protein. Positively selected sites at the amino acid level were evident in both the α1 and α2 domains, and a recombination breakpoint was found in exon 3. Bayesian phylogenetic trees showed no evidence of trans-species polymorphism (TSP) with alleles from carnivoran species in other families but did detect TSP between raccoon dogs and the domestic dog, Canis familiaris, indicative of long-term balancing selection in canids. Our results indicate that the extensive allelic diversity of MHC class I in Japanese and Russian raccoon dogs has been influenced and maintained by pathogen-driven positive selection, recombination, and long-term balancing selection.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13364-021-00561-y.

Identification of Novel Alleles and Structural Haplotypes of Major Histocompatibility Complex Class I and DRB Genes in Domestic Cat (Felis catus) by a Newly Developed NGS-Based Genotyping Method

The major histocompatibility complex (MHC) is a highly polymorphic and duplicated genomic region that encodes transplantation and immune regulatory molecules. Although it is well-known that particular MHC allelic polymorphisms and haplotypes are genetically relate to immune-mediated diseases detailed information of the cat MHC (Feline Leukocyte Antigen; FLA) genetic and haplotypic structure and diversity is limited in comparison to humans and many other species. In this study, to better understand the degree and types of allele and allelic haplotype diversity of FLA-class I (FLA-I) and FLA-DRB loci in domestic cats, we identified six expressible FLA-I loci in peripheral white blood cells by in silico estimation of the coding exons and NGS-based amplicon sequencing using five unrelated cats. We then used a newly developed NGS-based genotyping method to genotype and annotate 32 FLA-I and 16 FLA-DRB sequences in two families of 20 domestic cats. A total of 14 FLA-I and seven FLA-DRB were identified as novel polymorphic sequences. Phylogenetic analyses grouped the sequences into six FLA-I (FLA-E/H/K, FLA-A, FLA-J, FLA-L, FLA-O and a tentatively named FLA-E/H/K_Rec) and four FLA-DRB (FLA-DRB1, FLA-DRB3, FLA-DRB4, and FLA-DRB5) lineages. Pedigree analysis of two cat families revealed eight distinct FLA structural haplotypes (Class I - DRB) with five to eight FLA-I and two to three FLA-DRB transcribed loci per haplotype. It is evident that the eight FLA haplotypes were generated by gene duplications and deletions, and rearrangements by genetic recombination with the accumulation and/or inheritance of novel polymorphisms. These findings are useful for further genetic diversity analysis and disease association studies among cat breeds and in veterinary medicine.

The utility of DLA typing for transplantation medicine in canine models

Transplantation medicine is used for the treatment of severe canine diseases, and the dog leukocyte antigen (DLA) is considered to be important in graft rejection. However, the utility of direct sequencing of both DLA classes I and II has not been assessed thoroughly. Eight healthy beagles with identified DLA genes were divided into two sets of four dogs, each including one donor and three recipients for skin transplantation. The following recipients were selected: one dog with a complete match, one with a haploidentical match, and one with a complete mismatch of the DLA gene with the donor. Full-thickness skin segments were obtained from each donor and transplanted to the recipients. A mixed lymphocyte reaction (MLR) assay was performed and analyzed by flow cytometry. Skin grafts of DLA haploidentical and mismatched pairs were grossly rejected within 14 days, whereas in fully matched DLA pairs, survival was as long as 21 days. Histopathological evaluation also showed moderate to severe lymphocytic infiltration and necrosis in DLA mismatched pairs. As seen in the MLR assay, the stimulation index of DLA mismatched pairs was significantly higher than that of fully matched DLA pairs in both sets (P<0.001). The allogeneic transplantation results suggested that it is possible to prolong transplant engraftment by completely matching the DLA genotype between the donor and recipient. Additionally, the MLR assay may be used as a simplified in vitro method to select donors.

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.

Evaluation of alloreactive T cells based on the degree of MHC incompatibility using flow cytometric mixed lymphocyte reaction assay in dogs

It has become anticipated that regenerative medicine will extend into the field of veterinary medicine as new treatments for various disorders. Although the use of allogeneic stem cells for tissue regeneration is more attractive than that of autologous cells in emergencies, the therapeutic potential of allogeneic transplantation is often limited by allo-immune responses inducing graft rejection. Therefore, a methodology for quantifying and monitoring alloreactive T cells is necessary for evaluating allo-immune responses. The mixed lymphocyte reaction (MLR) is widely used to evaluate T cell alloreactivity. In human, flow cytometric MLR with carboxyfluorescein diacetate succinimidyl ester has been established and used as a more useful assay than conventional MLR with radioisotope labeling. However, the available information about alloreactivity based on the differences of dog major histocompatibility complex (MHC) (dog leukocyte antigen, DLA) is quite limited in dog. In this paper, we describe our established flow cytometric MLR method that can quantify the T cell alloreactivity while distinguishing cell phenotypes in dog, and T cell alloreactivity among DLA-type matched pairs was significantly lower than DLA-mismatched pairs, suggesting that our developed flow cytometric MLR method is useful for quantifying T cell alloreactivity. In addition, we demonstrated the advantage of DLA homozygous cells as a donor (stimulator) for allogeneic transplantation. We also elucidated that the frequency of alloreactive T cell precursors was almost the same as that of mouse and human (1-10%). To our knowledge, this is the first report to focus on the degree of allo-immune responses in dog based on the differences of DLA polymorphisms.

Translating Pharmacogenetics and Pharmacogenomics to the Clinic: Progress in Human and Veterinary Medicine

As targeted personalized therapy becomes more widely used in human medicine, clients will expect the veterinary clinician to be able to implement an evidence-based strategy regarding both the prescribing of medicines and also recognition of the potential for adverse drug reactions (ADR) for their pet, at breed and individual level. This review aims to provide an overview of current developments and challenges in pharmacogenetics in medicine for a veterinary audience and to map these to developments in veterinary pharmacogenetics. Pharmacogenetics has been in development over the past 100 years but has been revolutionized following the publication of the human, and then veterinary species genomes. Genetic biomarkers called pharmacogenes have been identified as specific genetic loci on chromosomes which are associated with either positive or adverse drug responses. Pharmacogene variation may be classified according to the associated drug response, such as a change in (1) the pharmacokinetics; (2) the pharmacodynamics; (3) genes in the downstream pathway of the drug or (4) the effect of “off-target” genes resulting in a response that is unrelated to the intended target. There are many barriers to translation of pharmacogenetic information to the clinic, however, in human medicine, international initiatives are promising real change in the delivery of personalized medicine by 2025. We argue that for effective translation into the veterinary clinic, clinicians, international experts, and stakeholders must collaborate to ensure quality assurance and genetic test validation so that animals may also benefit from this genomics revolution.