Nuria Alemañ

Induction and Inhibition of Apoptosis by Pseudorabies Virus in the Trigeminal Ganglion during Acute Infection of Swine

ABSTRACT We examined the ability of pseudorabies virus (PRV) to induce and suppress apoptosis in the trigeminal ganglion during acute infection of its natural host. Eight pigs were intranasally inoculated with a virulent field strain of PRV, and at various early times after inoculation, the trigeminal ganglia were assessed histologically. PRV-infected cells were detected by use of immunohistochemistry and in situ hybridization, and apoptosis was identified by in situ terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling. Light and electron microscopy was also used for morphological studies. Apoptosis was readily detected among infiltrating immune cells that were located surrounding PRV-infected neurons. The majority of PRV-infected neurons did not show morphological or histochemical evidence of apoptosis, even including those neurons that were surrounded by numerous inflammatory cells and exhibited profound pathological changes. However, neuronal virus-induced apoptosis also occurred but at a sporadic low level. These findings suggest that PRV is able to block apoptosis of infected trigeminal ganglionic neurons during acute infection of swine. Furthermore, our results also suggest that apoptosis of infiltrating inflammatory cells may represent an important viral mechanism of immune evasion.

Pseudorabies virus infection in mink: a host-specific pathogenesis.

Pseudorabies virus (PRV) is an alphaherpesvirus that causes a neurological disease in many wild and domestic animals. The neuropathology elicited by PRV is quite consistent regardless of the host with the only exception of mink, in which it is characterized by a vasculopathy rather than by an encephalitis. In this study, we aimed to investigate the underlying pathogenic mechanism(s) of PRV infection in mink by using immunohistochemistry and laser capture microdissection (LCM) on material from naturally and experimentally infected animals. The inflammatory reaction induced by PRV was minimal or absent not only in the nervous system, where we identified a low number of macrophages and a few T lymphocytes, but also in the primary replication site, the oropharyngeal mucosa; however, the number of PRV-infected cells detected by immunohistochemistry was extremely high both in the peripheral mucosa and in the nervous tissue. On the other hand, the vascular pathology included parenchymal hemorrhages of various degrees and, in specific cortical areas of the brain, fibrinoid degeneration of the capillary walls. Detection of viral antigens by immunohistochemistry revealed infection of endothelial cells of capillaries situated both in the oropharyngeal mucosa and in the brain stem; the presence of PRV DNA in vessels was further demonstrated by PCR performed on LCM samples of brain capillaries. These results can be interpreted as supporting the idea that the different pathology of the disease in mink may be the consequence of an increased endotheliotropism of PRV in this species. Infection of the vessel wall may then lead to vascular pathology and impairment in endothelial cell function, resulting in a weak immune response to infection.

L-Particle Production during Primary Replication of Pseudorabies Virus in the Nasal Mucosa of Swine

ABSTRACT Different tissue culture cell lines infected with a number of alphaherpesviruses produce, in addition to virions, light particles (L particles). L particles are composed of the envelope and tegument components of the virion but totally lack the proteins of the capsid and the virus genome; therefore, they are noninfectious. In this electron microscopy report, we show that L particles are produced during primary replication of the alphaherpesvirus pseudorabies virus (PRV) in the nasal mucosa of experimentally infected swine, its natural host. Although PRV infected different types of cells of the respiratory and olfactory mucosae, PRV L particles were found to be produced exclusively by epithelial cells and fibroblasts. We observed that formation of noninfectious particles occurred by budding of condensed tegument at the inner nuclear membrane and at membranes of cytoplasmic vesicles, resulting in intracisternal and intravesicular L particles, respectively. Both forms of capsidless particles were clearly distinguishable by the presence of prominent surface projections on the envelope and the higher electron density of the tegument, morphological features which were only observed in intravesicular L particles. Moreover, intravesicular but not intracisternal L particles were found to be released by exocytosis and were also identified extracellularly. Comparative analysis between PRV virion and L-particle morphogenesis indicates that both types of virus particles share a common intracellular pathway of assembly and egress but that they show different production patterns during the replication cycle of PRV.

Visceral leishmaniasis with cardiac involvement in a dog: a case report

A dog presented with cutaneous nodules, enlarged lymph nodes and oedema in limbs, face and abdomen. The diagnosis of visceral leishmaniasis was established by identification of Leishmania amastigotes within macrophages from skin and popliteal lymph node biopsies. At necropsy, lesions were found in different organs, but it was particularly striking to observe large areas of pallor in the myocardium. Histological examination revealed an intense chronic inflammatory reaction in many organs, and numerous macrophages were found to contain amastigote forms of Leishmania. The inflammatory reaction was especially severe in the heart, where large areas of the myocardium appeared infiltrated with huge numbers of mononuclear immune cells, causing cardiac muscle atrophy and degeneration. Despite the severe inflammation, the number of parasitized macrophages was low in the myocardium, as revealed by immunohistochemical staining of Leishmania amastigotes. Because cardiac involvement is not usually described in this condition, this dog represents a very rare case of canine visceral leishmaniasis with affection of the myocardium.

Anatomical, immnunohistochemical and physiological characteristics of the vomeronasal vessels in cows and their possible role in vomeronasal reception

The general morphology of the vomeronasal vessels in adult cows was studied following a classic protocol, including optical, confocal and ultrastructural approaches. This anatomical work was completed immunohistochemically. The vomeronasal organ in cows is well developed, and its vessels are considerable in size. This fact allowed some functional properties of the vomeronasal arteries to be evaluated and, for the first time, their isometric tension to be recorded.

Rosenthal Fiber Encephalopathy in a Dog Resembling Alexander Disease in Humans

A young male Bernese mountain dog presented with neurologic abnormalities consisting of nonambulatory tetraparesis, generalized tremors, and depressed mental status. At necropsy only a mild enlargement of the lateral ventricles was seen. The histologic examination revealed the presence of eosinophilic deposits consistent with Rosenthal fibers (RFs) throughout the white matter of the central nervous system. There was also a marked proliferation of abnormally large astrocytes and limited myelin changes. RFs were most prominent in perivascular, subpial, and subependymal areas, where they were perpendicularly located, producing a pallisaded arrangement. immunohistochemically, RFs were strongly positive for glial fibrillary acidic protein (GFAP), and when they were examined ultrastructurally they appeared as electron-dense amorphous masses located within the processes of astrocytes, most particularly in the perivascular feet. The histologic and immunohistochemical findings of this canine case were consistent with the published neuropathologic descriptions of Alexander disease in humans and in a few dogs, a rare condition that in humans has been shown to be caused by dominant mutations in the GFAP gene.

Brain Pathology in Adult Rats Treated With Domoic Acid.

Domoic acid (DA) is a neurotoxin reported to produce damage to the hippocampus, which plays an important role in memory. The authors inoculated rats intraperitoneally with an effective toxic dose of DA to study the distribution of the toxin in major internal organs by using immunohistochemistry, as well as to evaluate the induced pathology by means of histopathologic and immunohistochemical methods at different time points after toxin administration (6, 10, and 24 hours; 5 and 54 days). DA was detected by immunohistochemistry exclusively in pyramidal neurons of the hippocampus at 6 and 10 hours after dosing. Lesions induced by DA were prominent at 5 days following treatment in selected regions of the brain: hippocampus, amygdala, piriform and perirhinal cortices, olfactory tubercle, septal nuclei, and thalamus. The authors found 2 types of lesions: delayed death of selective neurons and large areas of necrosis, both accompanied by astrocytosis and microgliosis. At 54 days after DA exposure, the pathology was characterized by still-distinguishable dying neurons, calcified lesions in the thalamus, persistent astrocytosis, and pronounced microgliosis. The expression of nitric oxide synthases suggests a role for nitric oxide in the pathogenesis of neuronal degeneration and chronic inflammation induced by DA in the brain.

Morphogenesis and growth of the soft tissue and cartilage of the vomeronasal organ in pigs

The morphology of the soft tissue and supporting cartilage of the vomeronasal organ of the fetal pig was studied from early stages to term. Specimens obtained from an abattoir were aged by crown‐to‐rump distance. Series of transverse sections show that some time before birth all structures – cartilage, connective tissue, blood vessels, nerves, glands and epithelia – are well developed and very similar in appearance to those of the adult. Furthermore, in transmission electron microscopy photomicrographs obtained at this stage the vomeronasal glands exhibit secretory activity.

Hemangiomatosis Associated with Osteolysis of the Mandible in a Dog Resembling Gorham-Stout Disease in Humans

A 6-month-old female German Shepherd Dog died as a result of profuse oral bleeding. At postmortem examination, the oral cavity showed visible roots of the right mandibular fourth premolar and first molar teeth and, in addition, they were very mobile and compressible. Radiographs showed a generalized radiolucency in the body of the right mandible, with evidence of resorption of the affected alveolar bone. Histologically, the lesion of the right mandible was characterized by the lysis of bony structures and a non-malignant proliferation of blood-filled vascular spaces lined by a single layer of well-differentiated endothelial cells. The clinical, radiographic, and histologic presentation of this dog is consistent with that associated with Gorham-Stout disease, a rare bone disorder in humans.