Veterinary Pathology最新文献

Understanding the origin, distribution, and biology of different cell populations in chimeric mice is critical for interpreting the pathological changes developed in these models. To this aim, the methodological work presented here illustrates the validation and application of a collection of labeling techniques to differentiate between specific mouse and human tissue/cell components in formalin-fixed paraffin-embedded samples from chimeric mice, especially those bearing human tumor and immune cells. First, broad approaches to identify cells of human origin using ubiquitous immunohistochemical targets such as HLA-A, Ku80, and human mitochondrial 60 kDa protein (hMito) were established using specimens from humanized mice and a human tissue microarray including both normal and neoplastic samples. Due to its crisp membranous immunoreactivity, HLA-A was the most useful marker for visual human cell identification; however, Ku80 and hMito may be suitable options when HLA-A is not expressed in the cells of interest. Importantly, using one or more of these markers provides a broad range of coverage for the vast majority of human-derived cells in chimeric mice. Second, tailored immunohistochemical or in situ hybridization methodologies to distinguish specific human or mouse cell subsets are presented, focusing on immune/inflammatory cells and human chimeric antigen receptor (CAR) T-cells. These diverse approaches are accompanied by descriptions of case examples highlighting practical diagnostic and experimental applications in the context of various humanized mouse models. While not comprehensive, this work represents a valuable starting reference for pathologists and investigators working with humanized mouse models and seeking to add spatial resolution to the complex landscape of chimeric tissues.

Chimeric antigen receptor (CAR) T cells are revolutionary cancer therapies that are Food and Drug Administration-approved for hematologic malignancies and under investigation for solid tumors. The use of allogeneic over autologous CAR T cells offers advantages, including broader availability and reduced costs. However, allogeneic CAR T cells frequently trigger graft versus host disease (GvHD), a complication observed in patients and experimental models where human CAR T cells are delivered into immunocompromised mice. To understand the contribution of the mouse immune response to human CAR T cell-mediated xenogeneic GvHD, we analyzed GvHD lesions in a human xenograft tumor model in NOD.Cg-Prkdc^scid Il2rg^tm1Wjl/SzJ (NSG) mice. The animals were treated with second-generation CAR T cells targeting a human tumor-specific antigen without a murine homolog. Mice treated with CAR T cells had more severe GvHD lesions than control mice receiving nontransduced (NT) T cells. Also, tumor burden was negatively correlated with GvHD lesion severity. Immunohistochemical characterization of the GvHD lesions showed that approximately 45% of the immune cell infiltrate consisted of murine cells, most of which were IBA1+ histiocytes, with a small population of CD11c+ dendritic cells. The murine histiocytes expressed activation/antigen presentation markers, including high levels of the costimulatory molecule CD86. Analysis of macrophage polarization indicated an M2-like phenotype. These findings demonstrate a significant contribution of the mouse histiocytic compartment to lesions of human CAR T cell-mediated xenogeneic GvHD. Our results suggest that CD86+ murine antigen-presenting cells help trigger and sustain the xenoreactive CAR T cell response. Furthermore, xenogeneic GvHD exhibits a shift toward M2 polarization in murine macrophages.

Axolotls (Ambystoma mexicanum) are critically endangered paedomorphic salamanders with remarkable regenerative capacity. While nearly extinct in the wild, they are commonly maintained in captivity as companion animals, zoological display animals, and biomedical research colonies, where they serve as an animal model for genetics, developmental biology, and regenerative medicine. This report documents a case series of spontaneous myeloid leukemia in genetically related, co-housed adult axolotls in a zoological collection that resulted in 50% overall mortality over 38 months. Affected axolotls exhibited a range of signs, including generalized edema, hydrocoelom, long-term wasting, and sudden death. The most common gross lesions were splenomegaly (5/10) and hepatomegaly (4/10). Microscopically, widespread intravascular neoplasia, consisting of large round cells, was consistently observed (10/10). Neoplastic cells infiltrated and effaced the parenchyma of numerous visceral organs, particularly the spleen and liver. Cytochemical staining of neoplastic cells in blood smears showed strong positive cytoplasmic reactivity for α-naphthyl butyrate esterase and α-chloroacetate esterase and weak staining with periodic-acid Schiff. In tissues, neoplastic cells did not react with Sudan black B and did not express CD3 or ionized calcium-binding adaptor molecule 1 (IBA-1). The morphologic features of the cells and phenotyping tests supported acute myeloid leukemia. This report represents the first documentation of acute myeloid leukemia in caudates.

Yersinia pseudotuberculosis (Yptb) is a gram-negative bacterium that can cause sporadic fatal infections in humans, domestic animals, and wildlife. We describe an outbreak of Yptb in a captive collection of 222 Seba's short-tailed bats (Carollia perspicillata), 50 of which died of confirmed (39 of 222, 17.6%) or suspected (11 of 222; 5.0%) Yptb infection. Females were more likely to be infected than males (odds ratio: 3.4), and non-pregnant females were more likely to be infected than pregnant females (odds ratio: 13.6). The most common gross lesions were multifocal cream/white discolorations and/or nodules (30 of 39, 77%) in the liver, followed by splenomegaly (23 of 39, 59%) and mesenteric lymphadenomegaly (9 of 39, 23%); 5 of 39 (13%) animals had no gross lesions. Histology was performed on the livers of 33 confirmed Yptb-positive animals, with the most common findings being extramedullary hematopoiesis (27 of 33, 82%) and pyogranulomatous or suppurative hepatitis (20 of 33, 61%). Hemosiderosis was observed in 32 of 33 (97%) cases and in 27 of 27 (100%) control animals that were not infected with Yptb. Solution inductively coupled mass spectrometry showed that infected bats had an average of 1.7× more hepatic iron than uninfected bats (P = .0067); this was corroborated by image analysis of Perl's stained sections (P < .0001), but laser ablation on a subset of cases was not significant (P = .1051). We hypothesize that hemosiderosis favors the systemic spread of Yptb by limiting the efficacy of hepcidin-mediated iron depletion, and that limiting dietary iron may protect captive wildlife from bacterial infections.

Several pulmonary lesions have been described in Virginia opossums (Didelphis virginiana), but fungal pneumonia in this species is largely unrecognized. We retrospectively analyzed gross and histologic pulmonary findings in 28 opossums from Louisiana. Lung sections were evaluated for fungal organisms, associated histologic changes, and other concurrent pulmonary lesions. Seventy-five percent of opossums (21/28) had pulmonary fungal organisms, and gross lesions were characteristic, consisting of patchy to generalized, indistinct, pinpoint, light-yellow parenchymal foci. These areas corresponded to alveoli filled with foamy macrophages and multinucleated giant cells that contained distinctive intracytoplasmic budding cells, which were 3 to 5 × 2 µm, ovoid to elongate, and argyrophilic, as well as rare pleomorphic fungal hyphae. Purpureocillium lilacinum was identified based on pulmonary fungal isolation and/or fungal internal transcribed spacer 2 (ITS-2) polymerase chain reaction (PCR) and sequencing in a subset of cases. Other findings included verminous pneumonia (13/28, 46%), pulmonary neoplasms (7/28, 25%), bacterial pneumonia (5/28, 18%), and endogenous lipid pneumonia (2/28, 7%). The histologic severity of fungal infections was significantly positively correlated with gross lesion severity and abundance of alveolar macrophages (P-values both < .0001). Identification of fungal pneumonia was as likely as verminous pneumonia, and fungal pneumonia was significantly more severe in opossums with concurrent verminous pneumonia (P = .0011). Despite the pulmonary changes, respiratory signs were rarely noted, even in severely affected cases. This is the first report associating P. lilacinum with fungal pneumonia in opossums from Louisiana. The characteristic gross and histologic lesions should prompt diagnosticians to closely evaluate for fungal organisms and consider P. lilacinum as a differential diagnosis.

Asian small-clawed otters (Aonyx cinereus, ASCOs) and North American river otters (Lontra canadensis, NAROs) are commonly housed at zoos and aquaria in the United States. The few reports of diseases in these species have mainly focused on free-ranging populations and do not represent otters in managed care. Necropsy reports from 93 individuals, 71 ASCO and 22 NARO, that died or were euthanized between 2000 and 2020 from 10 separate institutions were evaluated, including 47 females, 45 males, and 1 unreported sex. All otters with known ages ranged between 2 months and 21 years of age (median = 14 years). Otters were further divided into age classes according to known lifespan. ASCO age classes were juvenile (4; 6%), adult (26; 37%), older adult (9; 13%), and geriatric (32; 45%). NARO age classes were juveniles (0; 0%), adult (5; 23%), older adult (5; 23%), and geriatric (12; 55%). Common causes of death or euthanasia in both species included malignant neoplasia (29), chronic renal disease and/or urolithiasis (27), degenerative joint disease (13), and cardiovascular disease (10). Severe gastrointestinal hemorrhage caused mortality in 9 (13%) ASCOs. Common morbidities or comorbidities included periodontal disease (30) and degenerative joint disease (21). Consistent health and disease surveillance of these otter species in managed care will further elucidate mechanisms of disease, aid in the development of preventative and therapeutic strategies, and continue optimizing standards of care.

Tracheal neoplasia is considered infrequent in domestic animals. A detailed summarized description of the demographic trends of the patients and frequent tumor types arising from this anatomical location is missing in the reference literature. To better describe clinical and pathological features, a multi-institutional retrospective analysis and literature review were conducted to collect all the tracheal neoplasms reported in dogs and cats. Forty-two cases from a multi-institutional data search and 123 documented cases from the veterinary literature between 1961 and August 2024 were collected for a total of 165 cases. Dogs represented 41.2% (68/165) of the cases retrieved, whereas the remaining 58.8% (97/165) were cats. The most common tracheal neoplasia in dogs in descending order were osteochondroma, plasma cell tumor, chondrosarcoma, malignant epithelial tumors (adenocarcinoma and carcinoma), and chondroma. In dogs, most of the affected animals were males (53%), with a mean age at the time of diagnosis of 6.7 years, and most of the tumors were located at the cervical trachea (43%). Labrador retrievers represented 10% of the cases. In cats, the most common tracheal neoplasms were lymphoma and malignant epithelial tumors (adenocarcinoma, carcinoma, and squamous cell carcinoma). In cats, most of the affected animals were males (52%) and domestic shorthairs (62%), with a mean age at the time of diagnosis of 10.7 years, and most of the tumors were located at the cervical trachea (38%). Diagnosticians must consider these differential diagnoses when dealing with tracheal samples that are suspicious of neoplasia in dogs and cats.

Equine penile tumors are common in horses and are often related to infection with equine papillomavirus type 2 (EcPV2). This study investigated the immune cell infiltrate (ICI) of these tumors in horses, focusing on the role of EcPV2. Using multiplex immunohistochemistry (mIHC) for CD3, CD20, and IBA-1 and immunohistochemistry (IHC) for FoxP3, 27 horses with papillomas (5/27), in situ carcinomas (CISs) (3/27), and squamous cell carcinomas (SCCs) (19/27) were evaluated. Eighteen cases tested positive for EcPV2 by either or both in situ hybridization (ISH) and polymerase chain reaction (PCR) (18/27 by PCR, of which 16 were ISH+). The ICIs were more abundant in EcPV2-positive tumors, although differences were not statistically significant. The number of FoxP3+ regulatory T-cells was significantly higher in EcPV2+ tumors, both in intraepithelial and stromal compartments. There were higher IBA-1+ macrophage densities in SCCs than in papillomas or CISs. p53 IHC was performed, and non-basal positivity was associated with malignancy. The TP53 mutational analysis with next-generation sequencing revealed that 13/21 cases had a wild-type TP53, while TP53 variants were detected in 4/21 cases. The ICIs did not vary according to TP53 status. Tumor proliferation was also assessed with Ki67, which indicated progressively higher proliferation from benign to malignant tumors. In conclusion, although the number and distribution of B-cells, T-cells, and macrophages did not vary according to EcPV2 status, FoxP3 regulatory T-cells were observed in significantly higher numbers in EcPV2+ neoplasms, indicating a different immune landscape compared to EcPV2-negative tumors.