Canine Leukocytes Research Articles

Assessment of Y chromosome copy number alterations in non-neoplastic and neoplastic leukocytes of male dogs

The loss of the Y chromosome (ChrY), also known as LOY, is a common genetic alteration observed in men. It occurs in non-neoplastic cells as an age-related change as well as in neoplastic cells of various cancer types. While well-documented in humans, LOY has not been extensively studied in non-human mammals. In this study, we developed simple digital PCR-based assays to assess the copy number of ChrY relative to the X chromosome (ChrX) and chromosome 8 (Chr8) to evaluate ChrY numerical alterations in male canine DNA specimens. Using these assays, we analyzed non-neoplastic leukocytes from 162 male dogs without hematopoietic neoplasia to investigate the occurrence of age-related LOY in non-neoplastic leukocytes. Additionally, we examined 101 tumor DNA specimens obtained from male dogs diagnosed with various types of lymphoma and leukemia to determine whether copy number alterations of the ChrY occur in canine hematopoietic cancers. Analysis of the 162 non-neoplastic leukocyte DNA specimens from male dogs of varying ages revealed a consistent ∼1:1 ChrY:ChrX ratio. This suggests that age-related LOY in non-neoplastic leukocytes is rare or absent in dogs. Conversely, a decreased or increased ChrY:ChrX ratio was detected in canine neoplastic leukocytes at varying frequencies across different canine hematopoietic malignancies (P = 0.01, Fisher's exact test). Notably, a higher incidence of LOY was observed in more aggressive cancer types. To determine if this relative LOY to ChrX was caused by changes in ChrY or ChrX, we further analyzed their relative copy numbers using Chr8 as a reference. Loss of ChrX relative to Chr8 was found in 21% (9/41) of B-cell lymphomas and 6% (1/18) of non-T-zone/high-grade T-cell lymphomas. In contrast, a subset (29%, 4/14) of T-cell chronic lymphocytic leukemia showed gain of ChrX relative to Chr8. Notably, no relative LOY to Chr8 was detected indolent hematopoietic cancers such as T-zone lymphoma (0/9) and chronic lymphocytic leukemia of B-cell (0/11) and T-cell origins (0/14). However, relative LOY to Chr8 was present in more aggressive canine hematopoietic cancers, with incidences of 24% (10/41) in B-cell lymphoma, 44% (8/18) in non-T-zone/high-grade T-cell lymphoma, and 75% (6/8) in acute leukemia. This study highlights both similarities and differences in LOY between human and canine non-neoplastic and neoplastic leukocytes. It underscores the need for further research into the role of ChrY in canine health and disease, as well as the significance of LOY across various species.

A single-cell RNA sequencing atlas of circulating leukocytes from healthy and osteosarcoma affected dogs.

Translationally relevant animal models are essential for the successful translation of basic science findings into clinical medicine. While rodent models are widely accessible, there are numerous limitations that prevent the extrapolation of findings to human medicine. One approach to overcome these limitations is to use animal models that are genetically diverse and naturally develop disease. For example, pet dogs spontaneously develop diseases that recapitulate the natural progression seen in humans and live in similar environments alongside humans. Thus, dogs represent a useful animal model for many areas of research. Despite the value of the canine model, species specific reagent limitations have hampered in depth characterization of canine immune cells, which constrains the conclusions that can be drawn from canine immunotherapy studies. To address this need, we used single-cell RNA sequencing to characterize the heterogeneity of circulating leukocytes in healthy dogs (n = 7) and osteosarcoma (OS) affected dogs (n = 10). We present a cellular atlas of leukocytes in healthy dogs, then employ the dataset to investigate the impact of primary OS tumors on the transcriptome of circulating leukocytes. We identified 36 unique cell populations amongst dog circulating leukocytes, with a remarkable amount of heterogeneity in CD4 T cell subtypes. In our comparison of healthy dogs and dogs with OS, we identified relative increases in the abundances of polymorphonuclear (PMN-) and monocytic (M-) myeloid-derived suppressor cells (MDSCs), as well as aberrations in gene expression within myeloid cells. Overall, this study provides a detailed atlas of canine leukocytes and investigates how the presence of osteosarcoma alters the transcriptional profiles of circulating immune cells.

In vitro protective effect of Heterothalamus alienus against the Philodryas patagoniensis venom

BackgroundTeas from aerial parts of Heterothalamus alienus are traditionally used in Southern Brazil for the treatment of snakebite. PurposeIn this study, we evaluated the protective effect of aqueous extract of H. alienus (ExHa) against Philodryas patagoniensis venom (PpV). Chemical composition, as well as antioxidant and toxicological potential of the ExHa were also evaluated. MethodsColorimetric assays characterized the profile and antioxidant potential of extract after decoction of its leaves and lyophilization. In addition, HPLC-DAD allowed to identify some compounds. We used the Artemia salina model and canine leukocytes to test the toxicological potential of ExHa. Finally, in vitro protective effect of ExHa against PpV was verified in mononuclear leukocytes. ResultsExHa presented high polyphenols levels, among these, rutin, quercetin, and ferulic acid. Moreover, the extract showed antioxidant activity (TAC, DPPH•, ABTS•+), including decreased ferrous-induced lipoperoxidation in brain and liver tissues. Contributing to these data, ExHa was nontoxic in A. salina (LD50 = 5,140 µg. ml−1) but increased cell death and generated genotoxicity from 100 µg. ml−1. Hence, we used 10 µg. ml−1 to evaluate antivenom activity, which protected the cells against cytotoxicity triggered by PpV. ConclusionWe conclude that ExHa presents antioxidant capacity, which can be related to protection against PpV. This fact opens new perspectives for the use of teas or similar in the treatment adjacent to antivenom against snakebite. However, its high concentrations can be toxic, and we must ensure its safe use.

Examination of IgG Fc Receptor CD16A and CD64 Expression by Canine Leukocytes and Their ADCC Activity in Engineered NK Cells.

Human natural killer (NK) cells can target tumor cells in an antigen-specific manner by the recognition of cell bound antibodies. This process induces antibody-dependent cell-mediated cytotoxicity (ADCC) and is exclusively mediated by the low affinity IgG Fc receptor CD16A (FcγRIIIA). Exploiting ADCC by NK cells is a major area of emphasis for advancing cancer immunotherapies. CD64 (FcγRI) is the only high affinity IgG FcR and it binds to the same IgG isotypes as CD16A, but it is not expressed by human NK cells. We have generated engineered human NK cells expressing recombinant CD64 with the goal of increasing their ADCC potency. Preclinical testing of this approach is essential for establishing efficacy and safety of the engineered NK cells. The dog provides particular advantages as a model, which includes spontaneous development of cancer in the setting of an intact and outbred immune system. To advance this immunotherapy model, we cloned canine CD16A and CD64 and generated specific mAbs. We report here for the first time the expression patterns of these FcγRs on dog peripheral blood leukocytes. CD64 was expressed by neutrophils and monocytes, but not lymphocytes, while canine CD16A was expressed at high levels by a subset of monocytes and lymphocytes. These expression patterns are similar to that of human leukocytes. Based on phenotypic characteristics, the CD16A+ lymphocytes consisted of T cells (CD3+ CD8+ CD5dim α/β TCR+) and NK cells (CD3− CD5− CD94+), but not B cells. Interestingly, the majority of canine CD16A+ lymphocytes were from the T cell population. Like human CD16A, canine CD16A was downregulated by a disintegrin and metalloproteinase 17 (ADAM17) upon leukocyte activation, revealing a conserved means of regulation. We also directly demonstrate that both canine CD16A and CD64 can induce ADCC when expressed in the NK cell line NK-92. These findings pave the way to engineering canine NK cells or T cells with high affinity recombinant canine CD64 to maximize ADCC and to test their safety and efficacy to benefit both humans and dogs.

Vitamins A and D and Zinc Affect the Leshmanicidal Activity of Canine Spleen Leukocytes.

Simple SummaryCanine leishmaniasis (CanL) is a zoonosis caused by the protozoan Leishmania infantum, with dogs being considered the main domestic reservoirs of the parasite and potential transmitters to humans through the phlebotomine vector. CanL is a chronic infectious disease that characteristically occurs in underdeveloped and developing countries, with a broad spectrum of clinical and immunopathological manifestations. Despite the efforts in the fight against the disease, many endemic sites of CanL persist, preceding human infection and representing a serious public health problem. The therapeutic arsenal for the treatment of leishmaniasis is limited by toxicity, high costs, and inefficacy, in some cases. Treatment failure implies the permanence of dogs as reservoirs of the parasite, with further aggravation of the public health problem, indicating that new therapies should be evaluated in order to increase the treatment efficacy. Recent studies have shown that nutrients can regulate the immune response in many clinical conditions, but no study has been conducted using spleen leukocytes in CanL. In this paper, we demonstrate for the first time that nutrients added to cultures of spleen leukocytes from dogs infected with CanL can modulate the immune response and parasite load compared to healthy dogs.Canine leishmaniasis (CanL) is a chronic disease caused by Leishmania infantum, and the limitations of the current treatments have encouraged new alternatives, such as the use of immunomodulatory nutrients. The objective of this study was to determine the serum levels of vitamin A (retinol), vitamin D (25(OH)VD3), and zinc (Zn) in dogs with CanL and the effect of in vitro supplementation with the respective active forms ATRA, 1,25(OH)2VD3, and SZn on spleen leukocyte cultures. Serum retinol, 25(OH)VD3, and Zn were determined by HPLC, ELISA, and ICP-MS, respectively. Spleen leukocyte cultures were used for the detection of NO and ROS by flow cytometry; the IFN-γ, TNF-α, and IL-10 levels were determined by ELISA; and the parasite load was determined by microscopy. We detected low serum levels of retinol and Zn and high levels of 25(OH)VD3 in the CanL group. The in vitro supplementation of CanL spleen leukocytes with ATRA, 1,25(OH)2VD3, and SZn, in addition to a soluble leishmania antigen (SLA) treatment, increased the NO and ROS levels, while the treatments with only ATRA and SZn increased the TNF-a levels. Increased IL-10 and IFN-g levels were observed with the addition of SLA to the medium, although the addition of the three nutrients led to a reduction of the IL-10 levels, and the addition of 1,25(OH)2VD3 and SZn led to a reduction of IFN-g. A supplementation with 1,25(OH)2VD3 and SZn reduced the parasite load but only in the absence of SLA. We suggest that the nutrients we tested are involved in the leishmanicidal mechanism, showing a potential for investigation in future studies.

Ectodomain shedding by ADAM17 (a disintegrin and metalloproteinase 17) in canine neutrophils

ADAM17 is a transmembrane protease expressed by most cells in humans and mice that cleaves cell surface substrates primarily in a cis manner, a process referred to as ectodomain shedding. ADAM17 has numerous substrates and plays a broad role in various physiological processes, including as a key regulator of inflammation. At this time, little is known about ADAM17 expression and function in dogs. A well-established ADAM17 substrate is the leukocyte adhesion protein CD62L (L-selectin). We show that a selective inhibitor of ADAM17, but not an inhibitor of its most closely related family member ADAM10, blocks CD62L shedding upon canine neutrophil activation. We also tested several anti-human ADAM17 monoclonal antibodies (mAbs) for staining canine neutrophils. Although most did not recognize canine neutrophils, the mAbs MEDI3622 and D1(A12) did. They also blocked the downregulation of CD62L upon neutrophil activation. MEDI3622 is a human IgG antibody and we found that a canine chimeric version of this mAb also blocked CD62L shedding by canine leukocytes. Taken together, our findings provide the first direct evidence of ADAM17 expression and sheddase activity in dogs, establishing a potential therapeutic target for various inflammatory disorders.

Performance of a Nageotte hemocytometer method and a flow cytometric assay for residual leukocyte quantification in leukoreduced canine packed red blood cells.

To evaluate the performances of a manual Nageotte hemocytometer method and commercial fluorescent bead-based flow cytometric assay for quantifying [rWBC] in leukoreduced canine packed red blood cell (pRBC) units. Prospective study. Five, commercially purchased, double leukoreduced canine pRBC units were spiked with canine leukocytes to create 6 pRBC standards with the following [rWBC]:<0.1, 0.375, 1.5, 3.0, 6.0, and 24.0 WBC/µL. [rWBC] of each pRBC standard was measured with the Nageotte hemocytometer and flow cytometric techniques. Limit of detection (LoD), linearity, and bias were determined for each method. For each standard, accuracy and precision were calculated; the cumulative accuracy and mean precision for measurements between the LoD and 24.0 WBC/µL were also determined. University veterinary blood bank and clinical pathology laboratory. The Nageotte hemocytometer method had an LoD=1.48 WBC/µL, inadequate linearity (R2 =0.92), and a significant negative proportional bias (slope best-fit line=0.52 ± 0.03). Between [rWBC] 1.5-24 WBC/µL, the technique demonstrated poor cumulative accuracy (6.7%) but acceptable mean precision (17.3%). Relative to a 2 rWBC/µL threshold, at 1.5 WBC/µL the method was inaccurate (6.7%) with acceptable precision (16.6%). The flow cytometric assay had an LoD=1.3 WBC/µL, acceptable linearity (R2 =0.99), and a mild positive proportional bias (slope best-fit line=1.11±0.01). The technique had acceptable cumulative accuracy (80%) and mean precision (10.7%) for measuring [rWBC] between 1.5 and 24 WBC/µL. At 1.5 WBC/µL, this method was acceptably accurate (86.7%) and precise (16.0%). The flow cytometric assay demonstrated acceptable performance for quantification of [rWBC] in leukoreduced canine pRBC units. The Nageotte hemocytometer method should be used cautiously due to poor accuracy and significant negative bias.

Naturally Occurring Level of Aflatoxin B1 Injures Human, Canine and Bovine Leukocytes Through ATP Depletion and Caspase Activation.

Aflatoxin (AF) B1 is a potent hepatotoxic, mutagenic, teratogenic mycotoxin and may cause immune suppression/dysregulation in humans and animals. Toxic effects of AFB1 on key mammalian immune cells (ie, leukocytes) needs to be mechanistically elucidated. In this study, along with the determination of AFB1's LC50 for certain leukocytes, we analyzed the effect of naturally occurring levels of AFB1 on apoptosis/necrosis of neutrophils, lymphocytes, and monocytes from healthy young humans (20- to 25-year-old male), dogs (1- to 2-year-old Persian/herd breed), and cattle (1- to 2-year-old cattle). Leukocytes were incubated for approximately 24 hours with naturally occurring levels of AFB1 (10 ng/mL). Intracellular adenosine triphosphate (ATP) depletion and caspase-3/7 activity were then determined by luciferase-dependent bioluminescence (BL). Furthermore, the necrotic leukocytes were measured using propidium iodide (PI)-related flow cytometry. A significant decrease (24%-45%, 33.2% ± 2.7%) in intracellular ATP content was observed in AFB1-treated neutrophils, lymphocytes, and monocytes in all studied mammals. Also, with such a low level (10 ng/mL) of AFB1, BL-based caspase-3/7 activity (BL intensity) in all 3 tested mammalian leukocyte lineages was noticeably increased (∼>2-fold). Flow cytometry-based PI staining (for viability assay) of the AFB1-treated leukocytes showed slightly/insignificantly more increase of necrotic (PI+) neutrophils, lymphocytes, and monocytes in human, dogs, and cattle. Even though in vitro LC50s for AFB1' (∼20,000-40,000 ng/mL) were approximately 2,000 to 4,000 times higher than background, these studies demonstrate leukocytes from human and farm/companion animals are sensitive to naturally occurring levels of AFB1. The observed in vitro ATP depletion and caspase activation in AFB1-exposed leukocytes can partially explain the underlying mechanisms of AFB1-induced immune disorders in mammals.

Induction of miR 21 impairs the anti-Leishmania response through inhibition of IL-12 in canine splenic leukocytes.

Visceral Leishmaniasis is a chronic zoonosis and, if left untreated, can be fatal. Infected dogs have decreased cellular immunity (Th1) and develop a potent humoral response (Th2), which is not effective for elimination of the protozoan. Immune response can be modulated by microRNAs (miRNAs), however, characterization of miRNAs and their possible regulatory role in the spleen of infected dogs have not been done. We evaluated miRNA expression in splenic leukocytes (SL) from dogs naturally infected with Leishmania infantum and developing leishmaniasis (CanL; n = 8) compared to healthy dogs (n = 4). Microarray analysis showed increased expression of miR 21, miR 148a, miR 7 and miR 615, and downregulation of miR 150, miR 125a and miR 125b. Real-time PCR validated the differential expression of miR 21, miR 148a and miR 615. Further, decrease of miR 21 in SL, by means of transfection with a miR 21 inhibitor, increased the IL-12 cytokine and the T-bet/GATA-3 ratio, and decreased parasite load on SL of dogs with CanL. Taken together, these findings suggest that L. infantum infection alters splenic expression of miRNAs and that miR 21 interferes in the cellular immune response of L. infantum-infected dogs, placing this miRNA as a possible therapeutic target in CanL.

Macrocyclic lactone anthelmintic-induced leukocyte binding to Dirofilaria immitis microfilariae: Influence of the drug resistance status of the parasite

The macrocyclic lactone anthelmintics are the only class of drug currently used to prevent heartworm disease. Their extremely high potency in vivo is not mirrored by their activity against Dirofilaria immitis larvae in vitro, leading to suggestions that they may require host immune functions to kill the parasites. We have previously shown that ivermectin stimulates the binding of canine peripheral blood mononuclear cells (PBMCs) and polymorphonuclear leukocytes (PMNs) to D. immitis microfilariae (Mf). We have now extended these studies to moxidectin and examined the ability of both drugs to stimulate canine PBMC and PMN attachment to Mf from multiple strains of D. immitis, including two that are proven to be resistant to ivermectin in vivo. Both ivermectin and moxidectin significantly increased the percentage of drug-susceptible parasites with cells attached at very low concentrations (<10 nM), but much higher concentrations of ivermectin (>100 nM) were required to increase the percentage of the two resistant strains, Yazoo-2013 and Metairie-2014, with cells attached. Moxidectin increased the percentage of the two resistant strains with cells attached at lower concentrations (<10 nM) than did ivermectin. The attachment of the PBMCs and PMNs did not result in any parasite killing in vitro. These data support the biological relevance of the drug-stimulated attachment of canine leukocytes to D. immitis Mf and suggest that this phenomenon is related to the drug resistance status of the parasites.

Effects of calcitriol on phagocytic function, toll-like receptor 4 expression, and cytokine production of canine leukocytes.

OBJECTIVE To determine the in vitro effects of calcitriol on indicators of immune system function in blood samples collected from healthy dogs. SAMPLE Blood samples from 8 healthy adult dogs. PROCEDURES Blood samples were incubated with calcitriol (10-7M) or control substance for 24 hours. Afterward, lipopolysaccharide (LPS)-, lipoteichoic acid (LTA)-, and N-acetylmuramyl-l-alanyl-d-isoglutamine hydrate (MDP)-stimulated leukocyte production of tumor necrosis factor (TNF) and interleukin-10 (IL10) were measured with a canine-specific multiplex assay. Phagocytosis of opsonized Escherichia coli and leukocyte expression of constitutive toll-like receptor 4 (TLR4) were evaluated via flow cytometry. Blood samples from 3 dogs were used to create a concentration-response curve to evaluate whether the observed cytokine modulation was concentration dependent. RESULTS Incubation of canine blood samples with calcitriol resulted in significant decreases in LPS-, LTA-, and MDP-stimulated leukocyte production of TNF but not IL10. Blunting of TNF production was concentration dependent. Leukocyte calcitriol exposure had no significant effect on phagocytosis and TLR4 expression. CONCLUSIONS AND CLINICAL RELEVANCE These data indicated that calcitriol induced an anti-inflammatory shift in canine leukocytes exposed to LPS, LTA, and MDP in vitro, without altering phagocytosis or TLR4 expression. Thus, calcitriol could represent a novel candidate immunomodulatory treatment for dogs.

Effects of calcitriol on apoptosis, toll-like receptor 4 expression, and cytokine production of endotoxin-primed canine leukocytes.

OBJECTIVE To determine the in vitro effect of calcitriol on indicators of immune system function in endotoxin-primed blood samples from healthy dogs. SAMPLE Blood samples from 6 healthy adult dogs. PROCEDURES Leukocytes were primed by incubation of blood samples with lipopolysaccharide (LPS; endotoxin) or PBS solution (unprimed control group) for 1 hour. Following priming, blood samples were incubated with calcitriol (2 × 10-7M) or ethanol (control substance) for 24 hours. After sample incubation, LPS-stimulated leukocyte production of tumor necrosis factor (TNF) and interleukin-10 (IL10) was measured with a canine-specific multiplex assay, and apoptosis and toll-like receptor 4 (TLR4) expression were evaluated via flow cytometry. RESULTS LPS stimulation of unprimed leukocytes but not endotoxin-primed leukocytes resulted in a significant increase in TNF and IL10 production, confirming the presence of endotoxin tolerance in dogs in vitro. Endotoxin priming significantly increased neutrophil viability with no effect on lymphocyte viability or TLR4 expression by neutrophils and monocytes. Calcitriol exposure significantly decreased LPS-stimulated production of TNF by unprimed and endotoxin-primed leukocytes. Conversely, calcitriol exposure had no effect on IL10 production by unprimed leukocytes but did significantly increase IL10 production by endotoxin-primed leukocytes. Calcitriol had no significant effect on the degree of neutrophil or lymphocyte apoptosis, nor was neutrophil and monocyte TLR4 expression affected in unprimed or endotoxin-primed leukocytes. CONCLUSIONS AND CLINICAL RELEVANCE These data indicated that calcitriol induced an anti-inflammatory shift in unprimed and endotoxin-primed canine leukocytes in vitro, without compromising neutrophil and monocyte TLR4 expression or altering the viability of neutrophils and lymphocytes in canine blood samples.

Characterization of a leukocidin identified in Staphylococcus pseudintermedius.

Bacterial infections from Staphylococcus pseudintermedius are the most common cause of skin infections (pyoderma) affecting dogs. Two component pore-forming leukocidins are a family of potent toxins secreted by staphylococci and consist of S (slow) and F (fast) components. They impair the innate immune system, the first line of defense against these pathogens. Seven different leukocidins have been characterized in Staphylococcus aureus, some of which are host and cell specific. Through genome sequencing and analysis of the S. pseudintermedius secretome using liquid chromatography mass spectrometry we identified two proteins, named “LukS-I” and “LukF-I”, encoded on a degenerate prophage contained in the genome of S. pseudintermedius isolates. Phylogenetic analysis of LukS-I components in comparison to the rest of the leukocidin family showed that LukS-I was most closely related to S. intermedius LukS-I, S. aureus LukE and LukP, whereas LukF-I was most similar to S. intermedius LukF-I S. aureus gamma hemolysin subunit B. The killing effect of recombinant S. pseudintermedius LukS-I and LukF-I on canine polymorphonuclear leukocytes was determined using a flow cytometry cell permeability assay. The cytotoxic effect occurred only when the two recombinant proteins were combined. Engineered mutant versions of the two-component pore-forming leukocidins, produced through amino acids substitutions at selected points, were not cytotoxic. Anti-Luk-I produced in dogs against attenuated proteins reduced the cytotoxic effect of native canine leukotoxin which highlights the importance of Luk-I as a promising component in a vaccine against canine S. pseudintermedius infections.

Analysis of DNA methylation of potential age-related methylation sites in canine peripheral blood leukocytes.

Reliable methodology for predicting the age of mature dogs is currently unavailable. In this study, amplicon sequencing of 50 blood samples obtained from diseased dogs was used to measure methylation in seven DNA regions. Significant correlations between methylation level and age were identified in four of the seven regions. These four regions were then tested in samples from 31 healthy toy poodles, and correlations were detected in two regions. The age of another 11 dogs was predicted using data from the diseased dogs and the healthy poodles. The mean difference between the actual and calculated ages was 34.3 and 23.1 months, respectively. Further research is needed to identify additional sites of age-related methylation and allow accurate age prediction in dogs.

Rhipicephalus turanicus, a new vector of Hepatozoon canis.

The distribution of Hepatozoon canis mainly encompasses areas where its main tick vector, Rhipicephalus sanguineus sensu lato, is present. However, the detection of this pathogen in dogs, foxes and golden jackals well outside the areas inhabited by this tick species reinforced the hypothesis that additional ixodids are involved in the life cycle and transmission of this protozoon. The present study provides, for the first time, data supporting the sporogonic development of H. canis in specimens of Rhipicephalus turanicus collected from a naturally infected fox from southern Italy. The epidemiological role of R. turanicus as a vector of H. canis is discussed, along with information on the potential use of cell cultures for the experimental infection with H. canis sporozoites. The in vitro infection of canine leucocytes by sporozoites from ticks is proposed as a potential tool for future in-depth studies on the biology of H. canis.

Canine Neutrophil Extracellular Traps Have Pro-Coagulant and Anti-Fibrinolytic Effects

Pet dogs experience similar environmental influences to their owners, and thus provide valuable spontaneous models for investigation of novel therapies for human disease. DNase and treatments targeting neutrophil extracellular trap (NET) proteins show promise in murine thrombosis models. Dogs at risk of thrombosis could provide evidence for the efficacy of these treatments in a second species, but the pro-thrombotic effects of NETs on canine plasma must be confirmed.We isolated neutrophils from healthy canine blood by density gradient and stimulated NET release using phorbol 12-myristate 13-acetate (PMA). To release NETs into suspension, culture media was replaced by the restriction enzyme Alu1. Supernatants were centrifuged to remove any intact cells. By gel electrophoresis, NET fragments were predominantly 600-1000 base pairs which is sufficient to simultaneously bind plasmin and fibrin (Arterioscler Thromb Vasc Biol., 2015, 35: 2544-53). To distinguish the effects of DNA and NET proteins, a subset of NET fragments were further digested with DNase. Supernatants were identically prepared from non-stimulated neutrophils. DNA concentration was 106ng/ml (sd 49, n=5 dogs) for non-stimulated supernatants; 401ng/ml (sd 94) for NET supernatants and reduced to 113ng/ml (sd 18) by DNase.The effect of NETs on clot formation and lysis were measured spectrophotometrically. To bring fibrinogen into the range typically found in dogs suffering from pro-thrombotic disease, 4.2mg/ml of plasminogen-depleted fibrinogen was mixed with pooled platelet poor plasma from healthy dogs. Plasma was incubated with non-stimulated supernatants; NETs +/- DNase or controls for effects of restriction enzymes, PMA and culture media. We added tissue factor, 5mM calcium chloride and 100µg/ml tissue plasminogen activator and measured absorption at 405nm q. 10 seconds for 25 minutes.NETs increased maximum formation velocity (MFV) (192mOD/min sd. 12, p=0.0011), measured by a line of best fit for the upswing of the curve, and delayed time to 50% clot lysis (448s sd. 43) compared with non-stimulated supernatants (165mOD/min sd. 12; 395s sd 38; n=5). Using a repeated measures ANOVA followed by paired t-tests with Tukey’s correction, the effect on MFV (p=0.0089) but not time to 50% clot lysis (p=0.08) remained significant after DNase digestion. NETs did not have detectable effects on area under the curve (AUC) or peak (pANOVA >0.2) (Fig. 1). Reagent controls had no detectable effects on any parameter (pANOVA≥0.717; 5-6 technical replicates).Reduction in fibrinolysis by DNA replicates its effect on human plasma (Arterioscler Thromb Vasc Biol., 2015, 35: 2544-53). The lack of effect of DNA on canine clot formation was surprising given the ability of DNA to increase human plasma thrombin generation (Arterioscler Thromb Vasc Biol. 2014, 34:1977-84). To determine if this was a species difference or a concentration dependent effect, DNA from canine leukocytes was added to plasma at a final concentration of 200ng/ml (approximately equal to the final concentration in our NET studies) or 1000ng/ml. At 1000ng/ml but not 200ng/ml, DNA increased MFV (p=0.038).To determine if NET proteins were increasing MFV by a direct effect on fibrinogen or thrombin, we next studied effects of NETs on thrombin induced clotting of plasminogen-depleted fibrinogen. NETs with or without DNase digestion had no detectable effects on peak, AUC, MFV or fibrin fiber diameter estimated by turbidity. This suggests NET proteins increase plasma clot formation rate through interactions with coagulation components other than thrombin or fibrinogen. Based on human and murine studies showing NET proteins inhibit endogenous anticoagulants, we selected histones and elastase as candidate proteins for further investigation. Purified histones from calf thymus added to plasma at approximately the concentration present in NET supernatants (150ng/ml) had no effect on MFV. Pre-incubation of elastase with canine plasma abolished elastase activity measured by N-Succinyl-Ala-Ala-Ala-p-nitroanilide. Therefore, it is unlikely that the ability of canine NET proteins to increase MFV is mediated by elastase or histones alone.In conclusion, NETs increase clot formation rate and delay lysis in canine platelet poor plasma. Since effects were mediated by both proteins and DNA, dogs are a promising model for trials of both DNase and therapies targeting NET proteins. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

378. Improved Transduction of Canine X-Linked Muscular Dystrophy with rAAV9-Microdystrophin by Introducing Immune Tolerance

Background: Duchenne muscular dystrophy (DMD) is a congenital disease causing progressive deterioration of skeletal and cardiac muscles because of mutations in the dystrophin gene. Supplementation of dystrophin using rAAV is effective to improve pathogenesis of animal models of DMD. However, we have previously reported that local injection of rAAV2 or rAAV8 to canine skeletal muscles without immunosuppression resulted in insufficient transgene expression with potent immune responses. Here we used DMD dog (CXMDJ) to investigate three strategies of inducing immune tolerance to the rAAV vector and transgene expression with rAAV9-microdystrophin (rAAV-µDys).Methods: For fetal transduction, we tried two methods to induce immune tolerance against rAAV and microdystrophin. First, direct injection of rAAV into amniotic fluid at embryonic day 35 (oral ingestion of rAAV). Second, pregnant CXMDJ heterozygote with embryonic day 30 fetuses was injected with rAAV by intravenous injection (trans-placental rAAV transduction). Furthermore, for postnatal transduction, we tried mesenchymal stem cells (MSCs) pretreatment with rAAV transduction. Bone-marrow derived MSCs and rAAV9-Luciferase or rAAV9-µDys were intramuscularly or intravenously injected into the normal or CXMDJ dog at 8 weeks old. Seven days after injection, MSCs were systemically injected again. At 8 days after 1st injection, rAAV9-Luciferase or rAAV9-µDys was intramuscularly or intravenously injected into the same dog. To examine the immune response against rAAV, purified canine peripheral leukocytes were exposed to rAAV9 for 4 hours, and then IFN-γ expression was analyzed using qRT-PCR. Skeletal muscles of the rAAV-Luc or rAAV-µDys injected animals were sampled by biopsy for expression analysis at 4 weeks after rAAV injection.Results: Following the fetal transduction, expression of IFN-γ in the purified peripheral blood leukocytes after the rAAV exposure were not induced in both of the rAAV oral ingestion and trans-placental transduced dogs, suggesting the successful induction of immune tolerance against rAAV. rAAV-derived microdystrophin expression were confirmed by immunohistochemistry in the transduced affected dogs from additional rAAV injection in both methods. In normal or CXMDJ puppy, administration of rAAV-Luc or rAAV-µDys following MSCs treatment resulted in higher expression of transgene, compared to the rAAV transduction alone. Expression of IFNγ in the purified peripheral blood leukocytes after the rAAV exposure were not enhanced in the rAAV with MSCs, suggesting the immune suppressive effects of the MSCs.Conclusion: Our results demonstrate that induction of immune tolerance against rAAV and/or transgene can be achieved both by fetal or postnatal rAAV injections. These strategies would be effective approach to analyze the expression and function of transgene in vivo. These findings also support the future feasibilities of rAAV-mediated protein supplementation strategies.

Immunophenotyping pattern characterization in canine blood: towards a clinical application

Immunophenotyping is a widely used method for a precise diagnosis and classification of haematopoietic neoplasia in human beings and also in dogs. The gold standard for cell preparation is density gradient centrifugation of mononuclear cells. Alternatively, another way to separate human leukocytes is carrying out whole blood lysis. The aim of this study was to validate whole blood lysis as an alternative method in clinical veterinary procedures using an immunophenotype panel of leukocytes designed by our group. Flow cytometry study of adult canine leukocytes subset groups, using whole blood lysis or mononuclear cells tested against an array of canine leukocyte antibodies were done. Besides differential white blood cell counts were done. Also immunophenotyping studies in whole blood samples stored at 4 °C for 48 h were performed. The Coefficient Variation values were less than 20%, for most of the comparison. Consistent results were observed in phenotyping canine peripheral blood leukocytes. Stability results indicated that whole blood samples might be stored for 48 h without a significant difference in the data compared to samples processed immediately after blood collection. This study shows that whole blood lysis represents an efficient and quick alternative for canine leukocyte preparation. In addition, samples can be analysed immediately or stored for 48 h without a significant difference between them. This is relevant for veterinary medicine considering the lack of facilities in many laboratories to process samples.

Effects of tramadol and o-desmethyltramadol on canine innate immune system function

ObjectiveTramadol is a commonly used opioid analgesic in dogs, particularly in dogs with a compromised immune system. An opioid may be selected for its immunomodulatory effects. Consequently, the objective of this study was to investigate the effects of tramadol on immune system function by evaluating the effect of tramadol and o-desmethyltramadol (M1) on the function of canine leukocytes in vitro. The hypothesis was that tramadol and M1 would not alter polymorphonuclear leukocyte (PMN) phagocytosis, PMN oxidative burst, or stimulated leukocyte cytokine production capacity of tumor necrosis factor (TNF)-a, interleukin (IL)-6, and IL-10. Study designIn vitro pharmacodynamic study. AnimalsSix healthy dogs. MethodsBlood from six dogs was obtained and incubated with various concentrations of tramadol and M1. Phagocytosis and oxidative burst were assessed using flow cytometry, and lipopolysaccharide (LPS), lipoteichoic acid (LTA) and peptidoglycan (PG)-stimulated leukocyte production of TNF, IL-6, and IL-10 were measured using a canine specific multiplex assay. ResultsNo differences were detected in phagocytosis or oxidative burst with any drug concentration. Tramadol did not alter leukocyte cytokine production, however, M1 significantly blunted IL-10 production. ConclusionsTramadol and its metabolite M1 were sparing to PMN phagocytosis and oxidative burst in dogs in vitro. Tramadol did not alter leukocyte cytokine production, however, M1 blunted IL-10 production at clinically achievable concentrations suggesting that M1 may promote a proinflammatory shift. Clinical relevanceThese data suggest that tramadol has minimal effect on phagocytosis and oxidative burst, and may promote a proinflammatory shift. Therefore, tramadol may be an ideal opioid analgesic in dogs at high risk of infection. Further investigation in vivo is warranted.

Identification of a candidate therapeutic antibody for treatment of canine B-cell lymphoma

B-cell lymphoma is one of the most frequently observed non-cutaneous neoplasms in dogs. For both human and canine BCL, the standard of care treatment typically involves a combination chemotherapy, e.g. “CHOP” therapy. Treatment for human lymphoma greatly benefited from the addition of anti-CD20 targeted biological therapeutics to these chemotherapy protocols; this type of therapeutic has not been available to the veterinary oncologist. Here, we describe the generation and characterization of a rituximab-like anti-CD20 antibody intended as a candidate treatment for canine B-cell lymphoma. A panel of anti-canine CD20 monoclonal antibodies was generated using a mouse hybridoma approach. Mouse monoclonal antibody 1E4 was selected for construction of a canine chimeric molecule based on its rank ordering in a flow cytometry-based affinity assay. 1E4 binds to approximately the same location in the extracellular domain of CD20 as rituximab, and 1E4-based chimeric antibodies co-stain canine B cells in flow cytometric analysis of canine leukocytes using an anti-canine CD21 antibody. We show that two of the four reported canine IgG subclasses (cIgGB and cIgGC) can bind to canine CD16a, a receptor involved in antibody-dependent cellular cytotoxicity (ADCC). Chimeric monoclonal antibodies were assembled using canine heavy chain constant regions that incorporated the appropriate effector function along with the mouse monoclonal 1E4 anti-canine CD20 variable regions, and expressed in CHO cells. We observed that 1E4-cIgGB and 1E4-cIgGC significantly deplete B-cell levels in healthy beagle dogs. The in vivo half-life of 1E4-cIgGB in a healthy dog was ∼14 days. The antibody 1E4-cIgGB has been selected for further testing and development as an agent for the treatment of canine B-cell lymphoma.