Pharmacodynamic assessment of ex-vivo canine T-lymphocyte proliferation: Responses to dexamethasone, cyclosporine, mycophenolic acid, and the active metabolite of leflunomide.

A lack of understanding of specific immune defects underlying canine immune-mediated diseases hampers optimal therapy. Failure to tailor treatment to an individual's immune abnormality can result in lack of efficacy, secondary complications, added expense, and drug-potentiated adverse effects. We adopted a small-volume whole-blood flow cytometric assay to determine the effect of immunosuppressant drugs on T-lymphocyte proliferation. Using healthy dogs in this proof-of-principle study, we hypothesized that there would be dose-dependent suppression of T-lymphocyte proliferation in response to dexamethasone, cyclosporine, mycophenolic acid, and the active metabolite of leflunomide (A77 1726). Whole blood was collected from 6 healthy pet dogs and incubated for 4 d with or without the mitogens concanavalin A and lipopolysaccharide and with increasing concentrations of immunosuppressant. Samples were subsequently stained with viability dye and with antibodies against the pan-T-lymphocyte marker CD5 and the cell proliferation marker Ki67. Percentages of proliferating T-lymphocytes were determined by flow cytometry, and the 50% inhibitory concentration (IC50) was calculated. Inhibition of T-lymphocyte proliferation by the panel of immunosuppressants was shown to be dose-dependent, with marked variability among the dogs. The mean IC50 was 394.8 ± 871 (standard deviation) µM for dexamethasone, 18.89 ± 36.2 ng/mL for cyclosporine, 106.3 ± 157.7 nM for mycophenolic acid, and 3.746 ± 6.8 µM for A77 1726. These results support the use of this assay for detecting the efficacy of individual immunosuppressants used to diminish T-lymphocyte proliferation. In future, the assay may be applied to pet dogs with spontaneous immune-mediated disease to help tailor individual treatment.

Un manque de compréhension des défauts immunitaires spécifiques sous-jacents aux maladies à médiation immunitaire canines nuit à une thérapie optimale. L'incapacité à concevoir un traitement approprié à l'anomalie immunitaire d'un individu peut résulter en une perte d'efficacité, des complications secondaires, une dépense supplémentaire, et des effets secondaires indésirables induits par les médicaments. Nous avons adopté un essai de cytométrie en flux sur un petit volume de sang entier afin de déterminer l'effet de médicaments immunosuppresseurs sur la prolifération de lymphocytes-T. En utilisant des chiens en santé dans cette étude de preuve de principe, nous avons émis l'hypothèse qu'il y aurait une suppression dose-dépendante de la prolifération des lymphocytes-T en réponse à la dexaméthasone, à la cyclosporine, à l'acide mycophénolique, et au métabolite actif du leflunomide (A77 1726). Du sang entier fut prélevé de six chiens en santé et incubé pendant 4 j avec et sans les agents mitogènes concanavaline A et lipopolysaccharide et avec des concentrations croissantes d'immunosuppresseurs. Les échantillons étaient par la suite colorés avec des colorants de viabilité et des anticorps contre le marqueur pan-lymphocyte-T CD5 et le marqueur de prolifération cellulaire Ki67. Les pourcentages de lymphocytes-T proliférant étaient déterminés par cytométrie en flux, et la concentration inhibitrice 50 % (IC50) fut calculée. L'inhibition de la prolifération de lymphocytes-T par la panoplie d'immunosuppresseurs a été démontrée comme étant dose-dépendante, avec une variabilité marquée parmi les chiens. L'IC50 moyenne était 394,8 ± 871 (écart-type) µM pour la dexaméthasone, 18,89 ± 36,2 ng/mL pour la cyclosporine, 106,3 ± 157,7 nm pour l'acide mycophénolique, et 3,746 ± 6,8 µM pour le A77 1726. Ces résultats appuient l'utilisation de cet essai pour détecter l'efficacité d'immunosuppresseurs individuels utilisés pour diminuer la prolifération de lymphocytes-T. Dans le futur, cet essai pourrait être utilisé chez des chiens de compagnie avec des maladies à médiation immunitaire spontanées afin d'aider à concevoir des traitements individuels.(Traduit par Docteur Serge Messier).

Dynamic changes of the respiratory microbiota and its relationship to fecal and blood microbiota in healthy young cats.

Advances in the field of metagenomics using culture-independent methods of microbial identification have allowed characterization of rich and diverse communities of bacteria in the lungs of healthy humans, mice, dogs, sheep and pigs. These data challenge the long held belief that the lungs are sterile and microbial colonization is synonymous with pathology. Studies in humans and animals demonstrate differences in the composition of airway microbiota in health versus disease suggesting respiratory dysbiosis occurs. Using 16S rRNA amplicon sequencing of DNA extracted from rectal and oropharyngeal (OP) swabs, bronchoalveolar lavage fluid (BALF), and blood, our objective was to characterize the fecal, OP, blood, and lower airway microbiota over time in healthy cats. This work in healthy cats, a species in which a respiratory microbiota has not yet been characterized, sets the stage for future studies in feline asthma in which cats serve as a comparative and translational model for humans. Fecal, OP and BALF samples were collected from six healthy research cats at day 0, week 2, and week 10; blood was collected at week 10. DNA was extracted, amplified via PCR, and sequenced using the Illumina MiSeq platform. Representative operational taxonomic units (OTUs) were identified and microbial richness and diversity were assessed. Principal component analysis (PCA) was used to visualize relatedness of samples and PERMANOVA was used to test for significant differences in microbial community composition. Fecal and OP swabs provided abundant DNA yielding a mean±SEM of 65,653±6,145 and 20,6323±4,360 sequences per sample, respectively while BALF and blood samples had lower coverage (1,489±430 and 269±18 sequences per sample, respectively). Oropharyngeal and fecal swabs were significantly richer than BALF (mean number OTUs 93, 88 and 36, respectively; p < 0.001) with no significant difference (p = 0.180) in richness between time points. PCA revealed site-specific microbial communities in the feces, and upper and lower airways. In comparison, blood had an apparent compositional similarity with BALF with regard to a few dominant taxa, but shared more OTUs with feces. Samples clustered more by time than by individual, with OP swabs having subjectively greater variation than other samples. In summary, healthy cats have a rich and distinct lower airway microbiome with dynamic bacterial populations. The microbiome is likely to be altered by factors such as age, environmental influences, and disease states. Further data are necessary to determine how the distinct feline microbiomes from the upper and lower airways, feces and blood are established and evolve. These data are relevant for comparisons between healthy cats and cats with respiratory disease.

Effects of positive end-expiratory pressure and 30% inspired oxygen on pulmonary mechanics and atelectasis in cats undergoing non-bronchoscopic bronchoalveolar lavage.

Objectives The objective of this study was to determine if modification of inspired oxygen concentration or positive end-expiratory pressure (PEEP) would alter bronchoalveolar lavage (BAL)-induced changes in pulmonary mechanics or atelectasis, as measured using ventilator-acquired pulmonary mechanics and thoracic CT. Methods Six experimentally asthmatic cats underwent anesthesia and non-bronchoscopic BAL, each under four randomized treatment conditions: 100% oxygen, zero PEEP; 30% oxygen, zero PEEP; 100% oxygen, PEEP 2 cmH2O; and 30% oxygen, PEEP 2 cmH2O. Pulse oximetry was used to estimate oxygen saturation (SpO2). Ventilator-acquired pulmonary mechanics and thoracic CT scans were collected prior to BAL and at 1, 5 and 15 mins post-BAL. Results While receiving 100% oxygen, no cat had SpO2 <91%. Some cats receiving 30% oxygen had decreased saturation immediately post-BAL (mean ± SD 70.8 ± 31%), but 6/8 of these had SpO2 >90% by 1 min later. There was a significant increase in airway resistance and a decrease in lung compliance following BAL, but there was no significant difference between treatment groups. Cats receiving no PEEP and 30% oxygen conserved better aeration of the lung parenchyma in BAL-sampled areas than those receiving no PEEP and 100% oxygen. Conclusions and relevance Alterations in pulmonary mechanics or atelectasis may not be reflected by SpO2 following BAL. The use of 30% inspired oxygen concentration failed to show any significant improvement in pulmonary mechanics but did diminish atelectasis. In some cats, it was also associated with desaturation of hemoglobin. The use of PEEP in this study did not show any effect on our outcome parameters. Further studies using higher PEEP (5-10 cmH2O) and intermediate inspired oxygen concentration (40-60%) are warranted to determine if they would confer clinical benefit in cats undergoing diagnostic BAL.