Vaccines to prevent Trypanosoma cruzi infection in humans or animals are not available, and in many settings, dogs are an important source of domestic infection for the insect vector. Identification of infected canines is crucial for evaluating peridomestic transmission dynamics and parasite control strategies. As immune control of T. cruzi infection is dependent on humoral and cell-mediated immune responses, we aimed to define a serodiagnostic assay and T cell phenotypic markers for identifying infected dogs and studying the canine T. cruzi-specific immune response. Plasma samples and peripheral blood mononuclear cells (PBMCs) were obtained from forty-two dogs living in a T. cruzi-endemic region. Twenty dogs were known to be seropositive and nine seronegative by conventional serologic tests two years prior to our study. To determine canine seroreactivity, we tested sera or plasma samples in a multiplex bead array against eleven recombinant T. cruzi proteins. Ninety-four percent (17/18) of dogs positive by multiplex serology were initially positive by conventional serology. The frequency of IFNγ-producing cells in PBMCs responding to T. cruzi correlated to serological status, identifying 95% of multiplex seropositive dogs. Intracellular staining identified CD4+ and CD8+ T cell populations as the sources of T. cruzi lysate-induced IFNγ. Low expression of CCR7 and CD62L on CD4+ and CD8+ T cells suggested a predominance of effector/effector memory T cells in seropositive canines. These results are the first, to our knowledge, to correlate T. cruzi-specific antibody responses with T cell responses in naturally infected dogs and validate these methods for identifying dogs exposed to T. cruzi.

Canines suffer from and serve as strong translational animals models for many immunological disorders and infectious diseases. Routine vaccination has been a mainstay of protecting dogs through the stimulation of robust antibody responses and expansion of memory T cell populations. Commercially available reagents and described techniques are limited for identifying and characterizing canine T cell subsets and evaluating T cell-specific effector function. To define reagents for delineating naïve versus activated T cells and identify antigen-specific T cells, we tested anti-human and anti-bovine T-cell specific cell surface marker reagents for cross-reactivity with canine peripheral blood mononuclear cells (PBMCs. Both CD4+ and CD8+ T cells from healthy canine donors showed reactivity to CCL19-Ig, a CCR7 ligand, and coexpression with CD62L. An in vitro stimulation with concanavalin A validated downregulation of CCR7 and CD62L expression on stimulated healthy control PBMCs, consistent with an activated T cell phenotype. Anti-IFNγ antibodies identified antigen-specific IFNγ-producing CD4+ and CD8+ T cells upon in vitro vaccine antigen PBMC stimulation. PBMC isolation within 24 hours of sample collection allowed for efficient cell recovery and accurate T cell effector function characterization. These data provide a reagent and techniques platform via flow cytometry for identifying canine T cell subsets and characterizing circulating antigen-specific canine T cells for potential use in diagnostic and field settings.

Background: Atovaquone and azithromycin (A&A) with supportive care improve survival rates in cats with cytauxzoonosis. Resistance to atovaquone via parasite cytochrome b gene (cytb) mutations occurs in other Apicomplexan protozoans but is not described in Cytauxzoon felis. Objective: To serially characterize the C. felis cytb sequences from a cat that remained persistently infected after A&A treatment. Animal: A cat with naturally occurring C. felis infection. Methods: Case report of the anemic cat persistently infected with C. felis before, during and after A&A treatment. Cytauxzoon felis cytb genes were amplified and sequenced before, during and after A&A treatment. Results: Cytauxzoon felis was detected before, during and after A&A treatment including samples collected 570 days after treatment. After A&A treatment, the cat's anemia improved slightly. Cytb sequencing revealed only wild-type cytb methionine (M128) in samples collected before treatment. In samples collected after treatment, the cytb coded for isoleucine (M128I) and valine (M128I) at 2-and 4-months after treatment. These M128I and M128V mutations persisted even after a repeat treatment course with a higher dose atovaquone combined with the standard dose of azithromycin. Conclusions and Clinical Importance: This report documents C. felis atovaquone resistance associated with M128 cytb mutations. This study suggests parasites with mutations of cytb M128 can be selected and impart resistance to A&A treatment even with higher atovaquone dosing.

To date studies have not investigated the culture-independent microbiome of bile from dogs, a species where aseptic collection of bile under ultrasound guidance is somewhat routine. Despite frequent collection of bile for culture-based diagnosis of bacterial cholecystitis, it is unknown whether bile from healthy dogs harbors uncultivable bacteria or a core microbiota. The answer to this question is critical to understanding the pathogenesis of biliary infection and as a baseline to exploration of other biliary diseases in dogs where uncultivable bacteria could play a pathogenic role. A pressing example of such a disease would be gallbladder mucocele formation in dogs. This prevalent and deadly condition is characterized by excessive secretion of abnormal mucus by the gallbladder epithelium that can eventually lead to rupture of the gallbladder or obstruction of bile flow. The cause of mucocele formation is unknown as is whether uncultivable, and therefore unrecognized, bacteria play any systematic role in pathogenesis. In this study we applied next-generation 16S rRNA gene sequencing to identify the culture-negative bacterial community of gallbladder bile from healthy dogs and gallbladder mucus from dogs with mucocele formation. Integral to our study was the use of 2 separate DNA isolations on each sample using different extraction methods and sequencing of negative control samples enabling recognition and curation of contaminating sequences. Microbiota findings were validated by simultaneous culture-based identification, cytological examination of bile, and fluorescence in-situ hybridization (FISH) performed on gallbladder mucosa. Using culture-dependent, cytological, FISH, and 16S rRNA sequencing approaches, results of our study do not support existence of a core microbiome in the bile of healthy dogs or gallbladder mucus from dogs with mucocele formation. Our findings further document how contaminating sequences can significantly contribute to the results of sequencing analysis when performed on samples with low bacterial biomass.

| CASE PRESENTATIONAn 8-year-old spayed female Nova Scotia Duck Tolling Retriever was presented to NC State Veterinary Hospital with a severalmonth history of polyuria/polydipsia, hyporexia, elevated liver values, hypercalcemia, hyperglobulinemia, and multifocal pyogranulomatous inflammation of unknown etiology. Physical examination revealed the patient to be dull with moderate dental calculus, mild muscle wasting, and few petechial hemorrhages on the medial aspect of the left fundus. The CBC revealed mild thrombocytopenia (177 × 10 3 /μL, RI 190-468), a mild left shift (0.174 × 10 3 /μL), and some rouleaux formation. Abnormal biochemistry findings included hypercalcemia (12.8 mg/dL, RI 9.4-11.4), hypoalbuminemia (2.4 g/dL, RI 3.0-3.9), hyperglobulinemia (5.5 g/dL, RI 1.7-3.8), hyperbilirubinemia (1.0 mg/dL, RI 0-0.2), elevated alkaline phosphatase (3665 IU/L, RI 16-140), increased alanine transferase (442 IU/L, RI 12-54), and increased creatine kinase (779 IU/L, RI 43-234). Urinalysis revealed a specific gravity of 1.024, 2+ bilirubin, and 2+ protein. Ionized hypercalcemia (1.43 mmol/L, RI 0.90-1.32) and hyperammonemia (47 μmol/L, RI 10-30) were also