Immunocytochemical methods for demonstrating canine distemper virus antigen in aldehyde-fixed paraffin-embedded tissue

Reduced neurogenesis in human hippocampus with Alzheimer's disease

Adult hippocampal neurogenesis (AHN), essential for the plasticity of hippocampal structure and function, may be disrupted in Alzheimer's disease (AD). However, the relationship between the changes in AHN and AD-related pathology in humans remains uncertain. By utilizing advanced immunostaining techniques, we could identify multiple biomarkers representing different stages of AHN in postmortem human hippocampal tissue that exhibited various AD-related neuropathological changes. In this study, we observed a significant presence of neurogenic cells in the hippocampus's dentate gyrus (DG) region in 30 individuals, including 14 individuals diagnosed with AD-related neuropathological changes and the remaining 16 individuals without any neurological diseases. Further investigation revealed that patients with AD exhibited pronounced astrogliosis and reduced neurogenesis. Specifically, the number of neuroblasts, immature and early mature granule cells decreased significantly as AD advanced. Although the number of neural stem cells (NSCs) remained unchanged in AD patients compared with mentally healthy individuals, they tended to be more quiescent state regulated by Notch and bone morphogenetic protein (BMP) signaling pathways. These abnormalities were strongly associated with the neuropathological alterations in AD patients. These research findings provide potential insights into the underlying mechanisms that underpin the pathogenesis of AD.

Unraveling human adult hippocampal neurogenesis

Adult neurogenesis occurs in a few selected regions of the mammalian brain. One such region is the hippocampus, the so-called gateway to memory, where adult hippocampal neurogenesis (AHN) occurs. Here, we provide a comprehensive description of the methods used in our laboratory to unambiguously detect a population of immature neurons in the human hippocampus until the 10th decade of life. The criteria used to refine and develop the current protocol include obtaining post-mortem human samples of remarkable quality and under tightly controlled conditions for immunohistochemistry (IHC) studies, optimizing tissue processing and histological procedures, establishing criteria to reliably validate antibody signal and performing unbiased stereological cell counts. Moreover, we provide a detailed description of the parameters that, in our view, should be reported in human AHN studies. The opposing results obtained by introducing slight variations in the methodological conditions should be considered by future studies that seek to increase our knowledge of this fascinating process. By applying simple and inexpensive tissue pre-treatments, this protocol, which can be completed in 7 days, might be applicable to a variety of IHC studies performed on other tissues of human (or animal) origin.

Immunohistochemical detection of canine distemper virus in haired skin, nasal mucosa, and footpad epithelium: a method for antemortem diagnosis of infection

A reliable antemortem diagnostic method is needed for determining infection with canine distemper virus (CDV). The utility of immunohistochemical detection of CDV antigen was examined was examined for samples of nasal and footpad epithelium and haired skin in dogs with and without detectable CDV antigen in the lung and/or brain. Tissues from 57 dogs at risk of CDV infection were tested. Viral antigen was found in the lung and/or brain of 28 dogs. Among these dogs, viral antigen was demonstrated in the epithelial cells of the nasal mucosa in 24 of 27 dogs, in the footpad epithelium in 24 of 26 dogs, and in the haired skin of the dorsal neck in 26 of 27 dogs. Among the 29 dogs without CDV antigen in either the lung or brain, 1 dog had positive staining for viral antigen in the skin and nasal mucosa. Biopsies of haired skin of the dorsal neck, which is relatively simple to sample, can be used for immunohistochemical testing for acute and subacute infection with CDV.

A comparison of in situ hybridization and immunohistochemistry for the detection of a new porcine circovirus in formalin-fixed tissues from pigs with post-weaning multisystemic wasting syndrome (PMWS)

Post-weaning multisystemic wasting syndrome (PMWS) is a recently identified condition affecting pigs in North America and Europe. Porcine circovirus antigen and nucleic acid have been demonstrated associated with lesions, and a new porcine circovirus designated PCV2 has been recovered from tissues of these animals. In this study, in situ hybridisation and immunohistochemical protocols were developed, optimized and compared for their relative sensitivity in detecting PCV2 antigens and nucleic acid in tissues from cases of PMWS that had been fixed for up to 6 months in formalin. For both immunohistochemistry and in situ hybridization, an increase in specific signal was observed following increased exposure to both protease XIV and proteinase K. Maximum signal and minimal loss of tissue morphology was seen after 40 min treatment with protease XIV (0.5 mg/ml). After optimisation, a comparison of these techniques on sequential sections demonstrated that both techniques successfully detected antigen or nucleic acid in all of the tissues examined. More positive cells, with increased signal intensity, were detected following immunohistochemistry.

Experimental old dog encephalitis (ODE) in a gnotobiotic dog

Experimental infection of a gnotobiotic Beagle dog with the neurovirulent R252 strain of canine distemper virus (R252-CDV) resulted in long-term central nervous system (CNS) infection; cerebral and brain stem lesions were consistent with old dog encephalitis (ODE). Eight clinical cycles of relapsing cortical and subcortical signs were documented over 33 months and were corroborated by the presence of both chronic and active inflammatory demyelinating lesions within the neuraxis. Immunocytochemistry revealed that CDV antigen was restricted to neurons. Attempts to use fresh brain tissue to directly transmit the infection to CDV-susceptible gnotobiotic dogs were unsuccessful. Reisolation of infectious virus from the infected dog required prolonged culture and coculture of brain explant cells with CDV-susceptible Vero cell monolayers. These findings demonstrate that ODE is a variant of virulent CDV-induced canine neurologic disease that can evolve de novo within the CNS of subclinically infected dogs in the absence of external sources of reinfection. The highly cell-associated nature of the virus, when first recovered from this dog, suggests that the virus was present within the CNS in a replication-defective form.

Manifestations of the local gastric immune response in gnotobiotic piglets infected with Helicobacter pylori

Helicobacter pylori, a human gastric bacterial pathogen, was inoculated into gnotobiotic piglets and manifestations of the resultant gastric inflammation was analyzed by in situ immunochemistry and flow cytometric analysis of isolated lamina propria leukocytes (LPL) and peripheral blood leukocytes (PBL) recovered from infected and control piglets. Gastric mucosa tissue sections from uninfected control piglets were essentially negative for cluster differentiation- (CD-) positive leukocytes. Failure to isolate significant numbers of LPL from the gastric lamina propria confirmed this observation. A local and systemic immune response occurs in piglets after infection with H. pylori. This is manifest by the appearance of cells associated with a local immune response in gastric mucosa. In gastric tissue sections from H. pylori-infected piglets, CD4-positive leukocytes were sparse and closely associated with developing lymphoid follicles whereas the CD8-positive cellular phenotype was abundant. The latter formed a continuous band in the lamina propria just above the muscularis mucosa. Perivascular accumulations of lymphocytes in the outer muscular tunic(s) were strongly positive for expression of CD8 antigen. Class II-positive cells were prominent in CD8 lymphocytic infiltrates, developing follicles and vascular endothelia but were uniformly absent from gastric epithelia even in sites overlying areas of immunocyte proliferation and infiltration. Leukocytes possessing the monocyte and granulocyte markers were rare. Plasma cells containing IgA were common in the periphery of developing lymphoid follicles or distributed as discrete foci around individual gastric pits. Fewer numbers of IgG- and IgM-positive plasma cells were identified. When the LPL flow cytometry data were compared with the flow cytometry data obtained from PBL in these same H. pylori-infected piglets, leukocytes bearing the CD8 marker predominated in LPL whereas leukocytes bearing the CD4-reactive and MHC class II markers predominated in PBL. Finally, local ELISA antibody responses were measured in mucosal explant culture supernatants and compared with in vivo antibody levels in sera, bile, and gastric juice. Antibody activity, specific for H. pylori, was detected in supermatants and serum in all three isotypes in actively infected piglets whereas gastric juice lacked antibodies. Gastric explants prepared from piglets in which infection had been successfully eradicated failed to produce local antibody into supermatant fluids. These data support the concept that the gastric inflammation observed is mediated by local immunological events.

Histologic and immunocytochemical characterization of canine distemper-associated metaphyseal bone lesions in young dogs following experimental infection

The proximal metaphyses of the humerus of weanling gnotobiotic dogs experimentally infected with canine distemper virus (CDV) were investigated histologically and immunocytochemically between 4 and 41 days after infection. Viral antigen was demonstrated in hematopoietic marrow and bone cells at postinfection day (PID) 5 and PID 7, respectively. Between PID 8 and 27, CDV antigen was abundantly present in marrow cells, osteoclasts, and osteoblasts and less frequently in osteocytes. Immunopositive cells in both osseous tissues and bone marrow declined between PID 29 and PID 36 and were absent by PID 41. Chondrocytes of the growth plate were negative for viral antigen throughout the observation period. In bone, viral antigen was more frequently observed in bone cells of the primary spongiosa than in the secondary spongiosa. There was a strong correlation between occurrence of CDV antigen and osseous changes. Associated metaphyseal bone lesions were mild and most prominent between PID 8 and PID 32. Lesions consisted of necrosis of osteoclasts, which was associated with subsequent persistence of the primary spongiosa (growth retardation lattice). Atrophy and necrosis of osteoblasts and marrow cells were also noted. Infection of metaphyseal bone cells appears to be common in young dogs with experimental systemic distemper. Bone cell infection is preceded by infection of marrow cells, and infected bone cells may experience degeneration and necrosis. This subtle viral effect may result in defects in bone modeling in CDV-infected dogs.

Intranuclear inclusions in paramyxovirus-induced encephalitis: evidence for altered nuclear body differentiation

Intranuclear inclusion bodies (INB) are frequently encountered in viral infections, where they are thought to be accumulations of viral particles. However, for RNA viruses replicating in the cytoplasm, this compartmentalization represents a paradox not consistent with the viral replication cycle. To define the basis for intranuclear paramyxoviral inclusion bodies in astrocytes, natural cases of canine distemper virus subacute encephalitis were examined by light and transmission electron microscopy, and by quantitative confocal immunofluorescence microscopy. Although INB were viral antigen positive, they were not composed of structurally recognizable paramyxoviral nucleocapsids. The structural basis for the INB was instead viral antigen-associated forms of nucleolar development known as nuclear bodies. Three variants of the light microscopic Cowdry type A INB were complex nuclear bodies, giant beaded nuclear bodies (sphaeridia), and nuclear body-associated granulofilamentous matrices. In the latter, the granulofilamentous matrix frequently filled the nucleus, resulting in a fourth morphological INB variant, and was associated with morphological evidence of nuclear degeneration. These findings suggest a novel mechanism of virus-induced cytopathology whereby intranuclear viral protein exerts deleterious effects upon nucleolar differentiation in infected cells and hence altered host cell RNA metabolism.

Detection of canine distemper virus in bone cells in the metaphyses of distemper-infected dogs

In the light of recent evidence implicating canine distemper virus (CDV) as a possible etiologic agent in Paget's disease of bone, we thought that it would be of interest to examine distemper-infected bone in the natural host. Samples from the long bones, spleen, and bladder of four distemper-infected and three uninfected dogs were examined for the presence of CDV nucleocapsid and phosphoprotein genes and the measles virus (MV) nucleocapsid gene using the technique of in situ hybridization with radioactively labeled riboprobes. Two of the four distemper-infected dogs showed strongly positive hybridization with both of the CDV probes. The signal was present in marrow cells, in osteoblasts, in osteocytes, and particularly in osteoclasts. No hybridization was seen over the cartilage cells of the growth plate, and there was a clear line of demarcation at the point of invasion of osteoclasts and vascularization. The spleen and bladder samples from infected dogs also showed positive hybridization. There was no hybridization with the MV probe in any of the distemper-infected tissue. Samples from the uninfected dogs showed no evidence of hybridization with either the CDV or MV probes. These results show that CDV can infect bone cells of the natural host and provide further support for the theory that CDV may play a role in human Paget's disease of bone.

Dogs, distemper and osteitis deformans: a further epidemiological study

There is extensive evidence linking paramyxoviruses, notably measles and respiratory syncytial virus, with Paget's disease of bone. The epidemiology of Paget's disease does not fit with that of known human paramyxovirus infections and it is possible that the disease is a zoonosis with domestic animals acting as host. Canine distemper, a paramyxovirus of the morbillovirus family (closely related to measles) is therefore a potential candidate. We have surveyed previous pet ownership in 150 Paget's patients each of whom was matched with two general practice controls; one from an inner city practice and the other from a suburban practice both in Greater Manchester. Recall of previous dog ownership was higher in Paget's patients with differences being more marked against inner city than suburban controls. 88% of the patients had lived in the same household as a dog at some stage compared with 79% of the inner city controls (P less than 0.05) and 83% of the suburban controls (n.s.). The differences were greater in the years 1930-60 during which the proportion of patients owning dogs was largest. For Paget's patients and controls alike, recalled exposure to dogs with canine distemper appeared to cluster in certain periods between 1930 and 1960. Unexpectedly, significantly more (7 out of 22, P less than 0.01) of the patients with a known first degree relative suffering from Paget's disease had no previous history of dog ownership when compared with the other patients (10 out of 128).

Use of immunocytochemistry and biotinylated in situ hybridisation for detecting measles virus in central nervous system tissue

Optimised immunocytochemical (ICC) and in situ hybridisation (ISH) protocols for long term, formalin fixed, central nervous system tissue infected with measles virus were developed. The effectiveness of 10 proteases for the enzymatic unmasking of formalin fixed antigen and nucleic acid was investigated. Protease VIII gave maximal signal generation with optimal tissue preservation and no background staining for both techniques. The use of a microwave oven as an additional pre-hybridisation step for RNA-RNA in situ hybridisation produced a significant increase in the number of cells labelled for genomic RNA. The ability to show the presence of antigen and nucleic acid in long term, formalin fixed tissue facilitates the use of stored necropsy material available in pathology departments for ICC and ISH investigations.

Histopathologic and immunocytochemical studies of distemper in seals

Thousands of harbor seals (Phoca vitulina) died in European seas during 1988. Respiratory distress and oculonasal discharge were common clinical signs. We necropsied 76 affected seals. The main necropsy finding was severe pneumonia. Microscopic lung changes were characterized by proliferation of type II pneumocytes, filling of alveolar lumina with serofibrinous exudate, leukocytes, and macrophages, and necrosis of bronchial and bronchiolar epithelium. Intracytoplasmic and intranuclear acidophilic inclusion bodies characteristic of morbillivirus infection were seen in bronchial and bronchiolar epithelial cells. Microscopic lesions of non-suppurative demyelinating encephalitis were seen in the brain. There was degeneration and necrosis of neurons, focal gliosis, perivascular cuffing, and patchy demyelination. Many neurons and astrocytes contained intracytoplasmic and intranuclear inclusions. Using an immunoperoxidase technique, we detected morbillivirus antigen in many tissues including lung, brain, spleen, and urinary bladder. The origin of the seal morbillivirus is unknown.

Canine distemper virus infectivity of various blood fractions for central nervous system vasculature

In order to determine the infectivity of various viremic blood fractions for central nervous system (CNS) endothelia, viremic plasma, platelets and mononuclear cells were prepared from canine distemper virus (CDV)-infected dogs and infused into the right carotid arteries of CDV-naive gnotobiotic dogs. All blood fractions were infectious for endothelia as determined by indirect immunofluorescence examination for viral antigen in recipients. Virus-positive platelets, even though possessing only trace amounts (1.0 x 10(1) TCID50/ml) of in vitro titratable virus, were the most effective fraction for infection of vascular endothelium. These data confirm the important role of vascular endothelia in establishing CNS infection in this disease and implicate virus-positive platelets and leukocytes in the initiation of this phenomenon.

Evaluation of different fixatives and treatments for immunohistochemical demonstration of Coxiella burnetti in paraffin-embedded tissues

Various fixatives and treatments such as acetone, methanol, Bouin fixative, modified Bouin fixative, 10% Formalin, modified methacarn, periodate-lysine-paraformaldehyde, acetone-methyl benzoate-xylene, and EDTA were evaluated for their effect on the immunoreactivity of Coxiella burnetii in paraffin-embedded tissues by using the avidin-biotin-peroxidase complex and the peroxidase-antiperoxidase procedure. C. burnetii antigen was shown to be present in liver, spleen, and uterus tissues of experimentally infected mice by all methods of fixation and treatment. A positive immunoreaction was seen in cytoplasmic vacuoles of macrophages, as extracellular rod-shaped organisms, and as residual particulate extra- and intracellular debris. Immunoreactivity and cellular preservation, however, varied substantially with the individual fixatives. Optimal immunostaining of C. burnetii was achieved by EDTA treatment and Bouin and acetone fixation. The avidin-biotin-peroxidase technique proved to be slightly more sensitive than the peroxidase-antiperoxidase procedure when primary antibody dilution was used as the criterion for sensitivity.

Establishment of central nervous system infection by canine distemper virus: breach of the blood-brain barrier and facilitation by antiviral antibody

Morphologic, immunologic and virologic data implicating antiviral antibody in promoting entry of canine distemper virus (CDV) into brain and reticuloendothelial tissues are reviewed. Infection of central nervous system (CNS) endothelium precedes invasion of virus-positive and -negative leukocytes into Virchow-Robin spaces and central nervous system (CNS) parenchyma by 1-3 days. Platelets are implicated in initiation of endothelial infection in that: CDV-infected dogs are thrombocytopenic; platelets from CDV-infected dogs contain IgG-virus complexes on their plasma membranes; platelet microthrombi were observed adjacent to foci of endothelial infection, and; CDV-susceptible ferrets rendered thrombocytopenic by antiplatelet antibody exhibit delayed viral entry into CNS tissues. Renal glomerular-bound IgG, IgM and occasionally CDV antigen were demonstrated in CDV-infected dogs by immunocytochemical techniques. Distemper-infected dogs with inherited C3 deficiency exhibited enhanced renal glomerular disease associated chiefly with deposition of IgM in mesengial regions vs. their homozygous normal CDV-infected littermates. Direct infusion of virus-positive leukocytes, plasma and platelets into the CNS capillary bed via the right carotid artery should establish the primacy of each in the initiation of CNS vascular endothelial infection by CDV.

Neuropathology and neurovirulence of canine distemper virus plaque isolates in the hamster

The relationship between neuropathological abnormalities, antibody response and neurovirulence of plaque isolates has been studied in an experimental model of canine distemper in the hamster. Genetic virus variance influenced neurovirulence and the experimental evidence supports the hypothesis that the mechanism of this effect may be through the modulating effect of circulating antibody. Large plaque virus (LPV) produced severe encephalitis with little early antibody response and a high degree of pathological abnormality. Small plaque virus (SPV) produced mild chronic encephalitis and early antibody response. Microscopically, histological abnormalities in this group were qualitatively similar to those seen with LPV but generally of lesser degree. Immunosuppression in SPV infected animals increased the severity of the encephalitis, reflected by the increase in inflammation and inclusion formation. Combined SPV and LPV infection produced high antibody levels and less severe disease than LPV infection alone with an intermediate pattern of histological abnormality.

Effects of induced thrombocytopenia on viral invasion of the central nervous system in canine distemper virus infection

Groups of canine distemper virus (CDV) susceptible ferrets were treated daily with 2.0 ml of normal goat serum (NGS) or goat anti-ferret platelet serum from 2 days before to 11 days after infection. Each group was subdivided into 2 and one subgroup of each was subsequently injected intraperitoneally with virulent R252-CDV. Ferrets were killed on days 2, 4, 6, 9 and 11 after infection and tissues from the central nervous system (CNS) were examined for histopathological lesions typical for CDV and also of CDV antigen by indirect immuno-fluorescence methods. In NGS-treated animals, a time course-dependent spread of CDV from CNS endothelium during days 2 to 4 after infection through choroid plexus epithelium was observed. In contrast, CDV-infected ferrets treated with anti-platelet antibody exhibited a delay in infection of CNS endothelium until 9 days after infection. The results of this study confirm vascular endothelium as the primary route of invasion of CNS tissues by CDV and implicate the circulating platelet in the initiation of this event.

Canine distemper virus: the early blood-brain barrier lesion

Experimental infection of gnotobiotic Beagle dogs with neurovirulent R252 canine distemper virus (CDV) resulted in hematogenous dissemination of virus to the central nervous system (CNS). Viral antigen was first detected within CNS capillary and venular endothelia and/or perivascular astrocytic foot processes and pericytes. The number of primary infection sites was evenly distributed throughout the neuraxis. Leukocytic infiltrations followed CNS endothelial cell infection by 1-2 days and were composed of both viral antigen-positive and -negative cells. These results indicate that CDV infection of the CNS is initiated by the interaction of circulating infectious virus with endothelial cells.