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MEL1 (MDS1/EVI1-like gene 1/PRDM16), a zinc finger protein, is located near the chromosomal breakpoint at 1p36 in human acute myeloid leukemia (AML) cells with the t (1; 3) (p36; q21) translocation. Mel1/Prdm16 is not only a causative gene of leukemia, but also has multiple regulatory functions, such as the regulation of fat metabolism. To investigate the function of Mel1/Prdm16, we generated Mel1/Prdm16-deficient mice, but homozygous deficiency (Mel1/Prdm16 -/- ) was embryonic lethal at E 11.5. Heterozygous mice showed abnormal cartilage and bone formation in the postnatal skull and long bones, suggesting that Mel1/Prdm16 expression plays an important role in bone development. In osteoblast and chondrocyte cell lines, Mel1/Prdm16 promotes the differentiation of chondrocytes and regulates the differentiation of osteoblasts. Transient repression of the master regulator Runx2 is required for chondrocyte differentiation at an early stage of differentiation. However, in Mel1/Prdm16-suppressed ATDC5 cells, the initial suppression of Runx2 was lacking and its expression was upregulated at the beginning of differentiation, suggesting that chondrogenic differentiation is suppressed in Mel1/Prdm16 +/- mesenchymal progenitor cells because Runx2 expression is upregulated during the early stage of differentiation. Thus, the Mel1/Prdm16 gene may be involved in the early repression of Runx2 expression during osteochondral differentiation and promote chondrogenic differentiation., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Mycoplasma bovis , the most important primary pathogen in the family Mycoplasmataceae , causes pneumonia, arthritis, otitis media, and mastitis in cattle. Histopathologic pulmonary changes associated with M. bovis infection have been characterized as suppurative-to-caseonecrotic bronchopneumonia; infection in other organs has been reported in only a few studies that examined caseonecrotic endocarditis and suppurative meningitis. Granulomatous lesions associated with M. bovis infection have been reported only rarely. We studied the granulomatous inflammation associated with M. bovis infection in several organs of 21 Japanese Black cattle. M. bovis was detected by isolation and loop-mediated isothermal amplification methods; other bacteria were detected using culture on 5% blood sheep agar and a MALDI-TOF MS Biotyper. Tissues were examined by histopathology and by immunohistochemistry (IHC) using anti- M. bovis , anti-Iba1, anti-iNOS, and anti-CD204 antibodies. All 21 cases, which included 2 cases of meningitis-meningoencephalitis, 8 cases of endocarditis, and 11 cases of bronchopneumonia, had caseonecrotic granulomatous inflammation associated with M. bovis infection. The IHC for macrophages revealed a predominance of iNOS-labeled (M1) macrophages in the inner layer of the caseonecrotic granulomas associated with meningitis-meningoencephalitis, endocarditis, and bronchopneumonia in Japanese Black cattle naturally infected with M. bovis .

Mycoplasma hyopneumoniae (Mhp) is the primary pathogen of porcine enzootic pneumonia (PEP). Consolidated lung tissue from the cranioventral lung lobes of 15 pigs with PEP was collected for quantitative polymerase chain reaction, histopathology and immunohistochemistry. Histopathology revealed the co-existence of bronchial-associated lymphoid tissue hyperplasia with intra-alveolar neutrophils and macrophage infiltration in lesions of suppurative bronchopneumonia. Immunolabelling of infiltrated macrophages with CD163/CD204 indicated the presence of M2-polarized macrophages. Mhp antigen was detected on respiratory epithelial cells and in phagocytosed neutrophils. The intensity of Mhp immunolabelling and number of CD163/CD204-positive macrophages were correlated with the Mhp load in lung tissue (r = 0.87, 0.56, P <0.05). IL-8 immunolabelling was mainly found in neutrophils and correlated with Mhp load, Mhp immunolabelling and histological lesion score (r = 0.70, 0.66, 0.64, P <0.05), respectively. Apoptosis was seen in intra-alveolar cells and was correlated with Mhp load (r = 0.62, P <0.05). It is postulated that IL-8 attracts neutrophils to the lesions, while M2-polarized macrophages are a major source of IL-10 and promote a Th2-type immune response., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

An eighteen-year-old female Eurasian otter became emaciated and died. Necropsy examination revealed nose and thoracic cutaneous masses, abdominal subcutaneous mass, and multiple nodules in the liver and lungs. Malignant melanoma was found in the nose cutaneous mass and to have metastasized to the liver, lungs, kidneys, adrenal glands, mammary glands and left mandibular lymph node. The neoplastic cells were labeled for vimentin, melanoma, and S100. The cutaneous mass in the thoracic area consisted of spindle shaped neoplastic epithelial cells and was diagnosed as trichoblastoma. Mammary gland adenoma was observed in the abdominal subcutaneous mass. This is the first report of primary three neoplasms of malignant melanoma, trichoblastoma and mammary gland adenoma in a Eurasian otter.

Investigation of the role of animals that have recovered and survived from African swine fever (ASF) in carrying the ASF virus is currently intense and ongoing. However, no clear definition of the carrier stage has been established. The aim of the present study was to establish criteria to elucidate a clear status of survival in naturally ASF-infected domestic pigs in Vietnam. Seroconversion from previous infection was confirmed by serological assay, and the absence of the viral genome in various organs was also assured by molecular analysis of a partial p72 gene. We recognized that histopathological evidence could benefit from further insights into the status and role of the surviving animals; therefore, we performed a histopathological study on four pigs from farms with a history of ASF outbreak. We found fibrotic changes in the reparative process as the main finding in all four pigs. Immunohistochemical detection of viral protein revealed an interesting result. Despite the negative result from viral genome detection, the p30 protein gave a positive signal in the tonsils, lung, and stomach. This raises the possibility of stress-induced viral reactivation in long-term survivors and the risk of further outbreaks from human handling of contaminated carcasses.

Following isolation of pseudorabies virus (PRV) from two hunting dogs in Oita prefecture, Japan, we investigated the PRV antigen distribution in the tissues of the infected animals. At necropsy, PRV-associated lesions included facial oedema, tonsillar and meningeal congestion, blotchy haemorrhages on the pericardium and mitral valves, and incomplete splenic contraction in one dog, with less prominent findings in the other dog. Multiple pulmonary nodules were seen in both cases, caused by the diploid form of Paragonimus westermani lung flukes, as confirmed by PCR-restriction fragment length polymorphism and gene sequencing analyses. Histological examination revealed that the PRV infection was associated with lesions of non-suppurative encephalitis in the brainstem. PRV antigen was detected in the cerebrum, cerebellum, brainstem, submucosal and myenteric plexuses, and mononuclear cells, mainly in the bone marrow, lymph nodes, tonsils and spleen tissues. There was evidence of PRV dissemination to the brain via the trigeminal or olfactory routes, in addition to possible spread to lymphoid organs via infected mononuclear cells., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Mycoplasma bovis (M. bovis) is a common inhabitant of the upper and lower respiratory tracts of cattle and is considered to be the main aetiological agent of otitis media in calves. The eustachian tube appears to be the most common portal for pathogens to enter the middle ear. We investigated the transmission route of M. bovis causing otitis media that progressed to meningitis or meningoencephalitis in Japanese Black cattle. M. bovis was detected in 10 cases by a loop-mediated isothermal amplification method or by immunohistochemistry. One case of caseonecrotic granulomatous meningoencephalitis, one case of caseonecrotic granulomatous meningitis, one case of suppurative meningoencephalitis, eight cases of eustachitis, nine cases of tonsillitis and six cases of suppurative bronchopneumonia were identified by histopathological examination. M. bovis antigen was detected in the eustachian tubes of eight cases. In nine cases, M. bovis was also detected in tonsillar epithelial crypts and lumina, in intraluminal inflammatory cells and in the epithelial cells of minor salivary glands located around the eustachian tubes and tonsils. The results suggest that M. bovis can infect and colonize the tonsils and enter the eustachian tubes, causing otitis media, which, in cases of chronic infection, can progress to meningitis., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Infectious bursal disease (IBD), caused by IBD virus (IBDV), is highly contagious, immunosuppressive and causes a negative economic impact on poultry industry. IBDV-vaccinated broiler farms at south Kyushu, Japan had a bursa-to-bodyweight ratio (BB ratio) reduction at 28 days (d) old, followed by high mortality 30 d later. We analysed the influence of the IBDV on atrophy of the bursa of fabricius (BF) and the subsequent mortality after 30 d. Ten broilers were sampled at each timepoint from the farm with high mortality at 21, 25, 28 and 35 d. A second flock from the same farm was sampled at 14, 21, 25, 28, 35 and 42 d. IBDV was detected in BF samples at 25, 28 and 35 d and at 21, 25, 28 and 35 d in the first and second flocks, respectively, using immunohistochemical staining and RT-PCR. IBDV isolates from both flocks were closely related to the China KM523643 strain. Histopathology and TUNEL assay indicated apoptosis, severe lymphoid depletion, vacuoles within follicles, lymphoid follicle atrophy and fibrosis in the BF. We observed 75% of the polyserositis and 10% of the airsacculitis at 30 D in dead broilers. The antigenic variant IBDV infection was appeared to be the main influencing factor on BF atrophy and BB ratio reduction in the broilers. High mortality in the broilers after 30 d could be due to secondary infection. The disease caused by IBDV had a negative economic impact in the farm. RESEARCH HIGHLIGHTS New variant IBDV caused bursa atrophy and reduced BB ratio in 28-day-old broilers. After vIBDV had infected broilers, at 21 days old they became immunosuppressed. High mortality at 30 days old in broilers was due to secondary infection. New vIBDV has a negative economic impact on broiler farms in Japan.

We previously reported the coinfection of novel porcine epidemic diarrhoea virus (PEDV) variants bearing large deletions in the S protein and PEDVs possessing an intact S protein (S-intact PEDV) in domestic pigs in Japan. The variants were frequently observed in pig farms with persistent or recurrent infection. To elucidate the role of the variants in persistent infections and their tropism properties, we genetically characterized and immunohistochemically detected PEDVs collected in primary and recurrent outbreaks in two persistently infected farms. Our results revealed coinfection of the PEDV variants bearing a 214-amino acid deletion in the S protein and S-intact PEDVs in the lungs of the naturally infected pigs. New tropisms of PEDV, including epithelial cells and submucosal glands of the airway tract, epithelial cells of the bile duct, and monocytes/macrophages were identified. The findings elucidate the mechanism of PEDV infection, epidemiology and pattern changes in the disease., (© 2020 Blackwell Verlag GmbH.)

Adult T-cell leukemia/lymphoma (ATLL) is a highly invasive and refractory T-cell malignancy, with poor prognosis. We previously identified that cell adhesion molecule 1 (CADM1) is overexpressed consistently in ATLL cells, and that CADM1 expression increases the adhesion capacity of ATLL cells to endothelial cells and promotes the organ invasion of ATLL cells in a xenograft mouse model. In this study, we first show that newly developed several anti-human CADM1 antibodies, which were complete human IgG antibodies generated by phage display method, specifically recognize CADM1 on ATLL cells. Although most of the CADM1 antibodies did not have a direct cytotoxic effect against CADM1-positive ATLL cells, clone 089-084 exhibited weak but significant antibody-dependent cell-mediated cytotoxic activity. Moreover, clone 103-189 effectively inhibits the interaction between endothelial cells and CADM1-positive ATLL cells. Furthermore, in mice bearing intra-splenic transplantation of EL4 mouse lymphoma cells expressing CADM1, the treatment of 103-189 significantly suppressed the organ invasion of CADM1-positive EL4 cells, resulting in improved survival time of mice. Therefore, since the anti-CADM1 antibody may be useful for the suppression of organ invasion in ATLL patients, combination use of the anti-CADM1 antibody with chemotherapy drugs could be beneficial for the efficient elimination of ATLL cells.