Immunohistological demonstration of respiratory syncytial virus antigens in Paget disease of bone

Rare Diseases of the Middle Ear and Lateral Skull Base

Otalgia, otorrhea and hearing loss are the most common ear-related symptoms that lead to the consultation of an otolaryngologist. Furthermore, balance disorders and affections of the cranial nerve function may play a role in the consultation. In large academic centres, but also in primary care, the identification of rare diseases of the middle ear and the lateral skull base is essential, as these diseases often require interdisciplinary approaches to establish the correct diagnosis and to initiate safe and adequate treatments. This review provides an overview of rare bone, neoplastic, haematological, autoimmunological and infectious disorders as well as malformations that may manifest in the middle ear and the lateral skull base. Knowledge of rare disorders is an essential factor ensuring the quality of patient care, in particular surgical procedures. Notably, in untypical, complicated, and prolonged disease courses, rare differential diagnoses need to be considered.

Human Respiratory Syncytial Virus Infection in a Human T Cell Line Is Hampered at Multiple Steps

Human respiratory syncytial virus (HRSV) is the most frequent cause of severe respiratory disease in children. The main targets of HRSV infection are epithelial cells of the respiratory tract, and the great majority of the studies regarding HRSV infection are done in respiratory cells. Recently, the interest on respiratory virus infection of lymphoid cells has been growing, but details of the interaction of HRSV with lymphoid cells remain unknown. Therefore, this study was done to assess the relationship of HRSV with A3.01 cells, a human CD4⁺ T cell line. Using flow cytometry and fluorescent focus assay, we found that A3.01 cells are susceptible but virtually not permissive to HRSV infection. Dequenching experiments revealed that the fusion process of HRSV in A3.01 cells was nearly abolished in comparison to HEp-2 cells, an epithelial cell lineage. Quantification of viral RNA by RT-qPCR showed that the replication of HRSV in A3.01 cells was considerably reduced. Western blot and quantitative flow cytometry analyses demonstrated that the production of HRSV proteins in A3.01 was significantly lower than in HEp-2 cells. Additionally, using fluorescence in situ hybridization, we found that the inclusion body-associated granules (IBAGs) were almost absent in HRSV inclusion bodies in A3.01 cells. We also assessed the intracellular trafficking of HRSV proteins and found that HRSV proteins colocalized partially with the secretory pathway in A3.01 cells, but these HRSV proteins and viral filaments were present only scarcely at the plasma membrane. HRSV infection of A3.01 CD4⁺ T cells is virtually unproductive as compared to HEp-2 cells, as a result of defects at several steps of the viral cycle: Fusion, genome replication, formation of inclusion bodies, recruitment of cellular proteins, virus assembly, and budding.

Antibody Response to Paramyxoviruses in Paget's Disease of Bone

Paget's disease of bone (PDB) is a common skeletal disorder characterised by focal abnormalities of increased and disorganised bone turnover. Genetic factors play a central role in the pathogenesis of PDB but environmental factors also contribute. Measles virus (MV), respiratory syncytial virus (RSV) and canine distemper virus (CDV) have all been implicated as potential disease triggers but the data are conflicting. Since chronic paramyxovirus infection with measles is known to be accompanied by increased production of antiviral antibodies, we have analysed circulating concentrations of antibodies to MV, CDV, and RSV as well as mumps, rubella and varicella zoster virus (VZV) in 463 patients with PDB and 220 aged and gender-matched controls. We also studied the relation between viral antibody concentrations and various markers of disease severity and extent in 460 PDB patients. A high proportion of cases and controls tested positive for antiviral antibodies but there was no significant difference in circulating antibody concentrations between PDB cases and controls for MV, CDV, RSV, rubella or VZV. However, mumps virus antibody levels were significantly higher in the PDB cases (mean ± SD = 3.1 ± 0.84 vs. 2.62 ± 0.86. p < 0.001). There was no association between disease severity and circulating antibody concentrations to any of the viruses. In conclusion, we found no evidence to suggest that PDB is associated with abnormalities of immune response to measles or other paramyxoviruses, although there was evidence of a greater antibody response to mumps. The results do not support that hypothesis that PDB is associated with a persistent infection with measles or other paramyxoviruses.

Management of Paget's Disease of the Calcaneum

The calcaneum is not the most common site for Paget's disease of bone, with only a few reports of monostotic involvement. We present 2 cases of Paget's disease of bone affecting the calcaneus, present an overview of the published data, and describe our management of these interesting cases.

Paget's disease of bone-genetic and environmental factors

Paget's disease of bone is generally diagnosed in individuals aged >50 years, usually manifests in one or several bones and is initiated by osteoclast-induced osteolytic lesions. Subsequently, over a period of many years, osteoblastic activity can result in sclerosis and deformation of bone. The prevalence of Paget's disease is highest in the UK and in countries where a large number of residents have ancestors from the UK. Currently, in many countries, the prevalence of the disorder has decreased. A considerable number of affected patients have a family history of Paget's disease and the disorder has an autosomal dominant pattern of inheritance but with incomplete penetrance. A large number of mutations in SQSTM1 (which encodes sequestosome-1; also known as ubiquitin-binding protein p62) seem to account for the susceptibility to develop Paget's disease in some families; the involvement of other genes is currently under investigation. In addition to a genetic cause, environmental factors have been proposed to have a role in the pathogenesis of Paget's disease. Although most evidence has been presented for measles virus as an aetiologic factor, some studies have not confirmed its involvement. The decreasing incidence of Paget's disease, which could be attributed to measles vaccination along with the measles virus nucleocapsid protein induction of Paget's disease lesions in transgenic mice, supports an aetiologic role of the virus.

Unbiased stereologic estimation of the spatial distribution of Paget's disease in the human temporal bone

BACKGROUND

It has been suggested that Paget's disease of bone and otosclerosis may share a myxoviral etiology. However, the association between virus infection and pathologic bone remodeling is still controversial. The aim of this study was to estimate the spatial distribution of pagetic bone remodeling around the inner ear space and to compare it with that of otosclerosis in a contemporary context of temporal bone dynamics.

MATERIALS AND METHODS

From the temporal bone collection of Massachusetts Eye and Ear Infirmary, 15 of 29 temporal bones with Paget's disease were selected to obtain an independent sample. All volume distributions were obtained along the normal axis of capsular bone remodeling activity by the use of vector-based stereology.

RESULTS

Pagetic bone remodeling was distributed centrifugally around the inner ear space at the individual and the general level. This pattern is similar to the normal distribution of perilabyrinthine bone remodeling but entirely different from the spatial location of otosclerosis, which are focal and centripetally distributed around the inner ear space.

CONCLUSION

In Paget's disease, the antiresorptive barrier around the inner ear space becomes gradually overruled as pagetic bone resorption invades the otic capsule from the outside. However, in otosclerosis, this barrier has somehow failed locally inside the otic capsule. Although virus infections potentially may trigger osteoclastic activity additional pathogenetic factors are needed to explain the organ-specific nature and spatial properties of otosclerosis.

Respiratory syncytial virus persistence in macrophages alters the profile of cellular gene expression

Viruses can persistently infect differentiated cells through regulation of expression of both their own genes and those of the host cell, thereby evading detection by the host’s immune system and achieving residence in a non-lytic state. Models in vitro with cell lines are useful tools in understanding the mechanisms associated with the establishment of viral persistence. In particular, a model to study respiratory syncytial virus (RSV) persistence in a murine macrophage-like cell line has been established. Compared to non-infected macrophages, macrophages persistently infected with RSV show altered expression both of genes coding for cytokines and trans-membrane proteins associated with antigen uptake and of genes related to cell survival. The biological changes associated with altered gene expression in macrophages as a consequence of persistent RSV infection are summarized.

Pathogenesis of Paget disease of bone

Paget disease of bone (PDB) is a common disease characterized by focal areas of increased and disorganized bone turnover. Some patients are asymptomatic, whereas others develop complications such as pain, osteoarthritis, fracture, deformity, deafness, and nerve compression syndromes. PDB is primarily caused by dysregulation of osteoclast differentiation and function, and there is increasing evidence that this is due, in part, to genetic factors. One of the most important predisposing genes is SQSTM1, which harbors mutations that cause osteoclast activation in 5-20 % of PDB patients. Seven additional susceptibility loci for PDB have been identified by genomewide association studies on chromosomes 1p13, 7q33, 8q22, 10p13, 14q32, 15q24, and 18q21. Although the causal variants remain to be discovered, three of these loci contain CSF1, TNFRSF11A, and TM7SF4, genes that are known to play a critical role in osteoclast differentiation and function. Environmental factors are also important in the pathogenesis of PDB, as reflected by the fact that in many countries the disease has become less common and less severe over recent years. The most widely studied environmental trigger is paramyxovirus infection, but attempts to detect viral transcripts in tissues from patients with PDB have yielded mixed results. Although our understanding of the pathophysiology of PDB has advanced tremendously over the past 10 years, many questions remain unanswered, such as the mechanisms responsible for the focal nature of the disease and the recent changes in prevalence and severity.

The etiology of Paget's disease of bone: viral and genetic interactions

Studies of the etiology of Paget's disease have focused separately on the viral and genetic components of the disease. In this issue of Cell Metabolism, Kurihara et al. (2011) join these components, reporting that sequestosome 1 mutation in patients and mice activates osteoclasts, while measles virus induces the phenotype of Paget's disease.

Cultures of HEp-2 cells persistently infected by human respiratory syncytial virus differ in chemokine expression and resistance to apoptosis as compared to lytic infections of the same cell type

HEp-2 cells that survived a lytic infection with Human Respiratory Syncytial Virus (HRSV) were grown to obtain a persistently infected culture that produced relatively high amounts of virus (10(6)-10(7) pfu/ml) for more than twenty passages. The cells in this culture were heterogeneous with regard to the expression of viral antigens, ranging from high to undetectable levels. However, all cell clones derived from the persistent culture did not produce infectious virus or viral antigens and grew more slowly than the original uninfected HEp-2 cells. When these "cured" cell clones were infected with wild-type HRSV, delayed virus production and reduction in the number and size of syncytia were observed compared to lytically infected HEp-2 cells. Most significantly, differences in gene expression between persistently and lytically infected cultures were also observed, including genes that encode for cytokines, chemokines and other gene products that either promote cell survival or inhibit apoptosis. These results highlight the significantly different responses of the same cell type to HRSV infection depending on the outcome of such infection, i.e., lytic versus persistent.

Pathogenesis of Paget's disease of bone

Paget's disease of bone is a common condition characterised by increased and disorganised bone turnover which can affect one or several bones throughout the skeleton. These abnormalities disrupt normal bone architecture and lead to various complications such as bone pain osteoarthritis, pathological fracture, bone deformity, deafness, and nerve compression syndromes. Genetic factors play an important role in PDB and mutations or polymorphisms have been identified in four genes that cause classical Paget's disease and related syndromes. These include TNFRSF11A, which encodes RANK, TNFRSF11B which encodes osteoprotegerin, VCP which encodes p97, and SQSTM1 which encodes p62. All of these genes play a role in the RANK-NFkappaB signalling pathway and it is likely that the mutations predispose to PDB by disrupting normal signalling, leading to osteoclast activation. Although Paget's has traditionally be considered a disease of the osteoclast there is evidence that stromal cell function and osteoblast function are also abnormal, which might account for the fact that the disease is associated with increased bone formation as well as resorption. Environmental factors also contribute to Paget's disease. Most research has focused on paramyxovirus infection as a possible environmental trigger but evidence in favour of the involvement of viruses in the disease remains conflicting. Other factors which have been implicated as possible disease triggers include mechanical loading, dietary calcium and environmental toxins. Further work will be required to identify additional genetic variants that predispose to Paget's disease and to determine how the causal mutations and predisposing polymorphisms interact with environmental factors to influence bone cell function and cause the focal bone lesions that are characteristic of the disease.

Failure to detect measles virus ribonucleic acid in bone cells from patients with Paget's disease

BACKGROUND

Paget's disease is a condition of focal accelerated bone turnover. Electron-microscopy investigations of osteoclasts from pagetic lesions have identified nuclear inclusion bodies that have a similar appearance to viral nucleocapsid particles. Subsequently, RNA from several paramyxoviruses has been detected in pagetic tissue, and it was suggested that these viruses, in particular measles, might play a role in the etiology of Paget's disease. We have tested for measles virus sequences in osteoblasts and bone marrow cells collected from pagetic lesions and healthy bone.

METHODS

Bone and bone marrow samples were taken from Paget's patients and control subjects, and cells were cultured from each of these tissues. RNA was extracted from 13 osteoblast cultures and 13 cultures of bone marrow cells derived from pagetic lesions, and from 26 and 23 control osteoblast and bone marrow cultures, respectively. These samples were sourced from 22 patients with Paget's disease and 31 controls. RT-PCR-nested PCR amplification was used for the detection of the genes for the measles nucleocapsid and matrix proteins.

RESULTS

Measles virus sequences were not detected in any of the pagetic or control samples. However, measles virus sequences were identified in samples of a measles virus culture isolate included as a positive control, and in a brain sample from a patient with subacute sclerosing panencephalitis, a condition associated with chronic measles infection.

CONCLUSION

The results of the study do not support the hypothesis that measles virus plays a role in the pathogenesis of Paget's disease.

Role of RANKL in physiological and pathological bone resorption and therapeutics targeting the RANKL-RANK signaling system

Osteoclasts are primary cells for physiological and pathological bone resorption, and receptor activator of nuclear factor-kappaB ligand (RANKL) is critically involved in the differentiation, activation, and survival of these cells. Recently, therapeutics for pathological bone destruction targeting RANKL pathways has attracted a great deal of attention. Herein, we review the recent advances in the research on osteoclast biology and discuss the advantages and disadvantages of anti-RANKL therapies.

Interleukin-8 mRNA synthesis and protein secretion are continuously up-regulated by respiratory syncytial virus persistently infected cells

The aim of this study was to investigate whether respiratory syncytial virus persistence regulates interleukin 8 (IL-8) mRNA synthesis and protein secretion in a human lung epithelial cell line (A549). Therefore, we established RSV persistence in these cells (A549per) and determined the levels of interleukin-8 mRNA by RT-PCR and of protein through ELISA. Interleukin-8 mRNA synthesis and protein secretion were continuously up-regulated in A549per cells during passages and in A549 cells that had been incubated with supernatants (cA549per) obtained from A549per passages. These results suggested that the enhancement of interleukin-8 was stimulated either by the presence of the RSV genome in the cell or by soluble mediator(s) induced by RSV, which, in turn, increased interleukin-8 mRNA synthesis and protein secretion. Soluble RSV F and G proteins were identified as mediators. Moreover, interleukin-8 enhancement was observed after 1-min incubation with the soluble mediators, thus suggesting that interleukin-8 up-regulation was triggered by receptor-ligand interaction.

A comparison of in situ hybridisation, reverse transcriptase-polymerase chain reaction (RT-PCR) and in situ-RT-PCR for the detection of canine distemper virus RNA in Paget's disease

Previous evidence implicating Paramyxoviruses in the aetiopathology of Paget's disease of bone has proved controversial. Whilst several groups have demonstrated Paramyxoviruses using techniques such as in situ hybridisation (ISH), reverse transcriptase-polymerase chain reaction (RT-PCR), and in situ-RT-PCR (IS-RT-PCR), others have found no evidence of viruses using only RT-PCR. To investigate this latter finding, we have now compared detection of canine distemper virus by ISH, RT-PCR (three different methods) and IS-RT-PCR, in 10 patients with Paget's disease, and samples of non-diseased bone from four patients. Canine distemper virus was detectable in six of the samples by ISH, but only in five of the samples by RT-PCR, using one of the methods. Neither of the other RT-PCR methods detected canine distemper virus. IS-RT-PCR demonstrated canine distemper virus in all 10 samples. There was no evidence of virus in the control samples. We have shown that the ability to detect canine distemper virus in bone is dependent on the technique used. IS-RT-PCR clearly showed that canine distemper virus was present in 100% of Pagetic samples, whereas canine distemper virus was only found in 60% by ISH and in 50% using one particular RT-PCR method. These results provide conclusive evidence that canine distemper virus is present within Pagetic bone, and provide a possible explanation for the failure of some groups to detect Paramyxovirus sequences. These findings also have wider implications for other studies investigating viral expression.

Sequence analysis of measles virus nucleocapsid transcripts in patients with Paget's disease

It has been debated for almost 30 years whether Paget's disease of bone results from paramyxoviral infection of osteoclasts (OCs). Paramyxoviral-like nuclear inclusions are found in OCs from patients with Paget's disease, and measles virus (MV) or canine distemper virus (CDV) messenger RNA (mRNA) transcripts have been detected by in situ hybridization in bone cells from pagetic lesions. Furthermore, immunocytochemical studies have shown the presence of several paramyxoviral species in OCs from patients with Paget's disease. However, others have been unable to detect paramyxoviral transcripts in bone samples from patients with Paget's disease or marrow cultures from involved sites of patients with Paget's disease. Furthermore, no one has been able to isolate an infectious virus from pagetic bone samples or marrow cells from patients with Paget's disease, and a full-length viral gene has not been sequenced from pagetic samples. In this study, we have obtained the full-length sequence for the MV nucleocapsid (MVNP) gene in bone marrow from an involved site from a patient with Paget's disease and more than 700 base pairs (bps) of MVNP sequence in 3 other patients with Paget's disease. These sequences were undetectable in four normal marrow samples studied simultaneously. The sequences from the patients contained multiple mutations that differed from the Edmonston strain MVNP gene. These findings are consistent with the presence of a chronic MV infection in affected sites from these patients with Paget's disease.

Osteoclasts expressing the measles virus nucleocapsid gene display a pagetic phenotype

Osteoclasts (OCLs) in Paget's disease are markedly increased in number and size, have increased numbers of nuclei per multinucleated cell, and demonstrate increased resorption capacity and increased sensitivity to 1,25-(OH)(2)D(3), the active form of vitamin D. These cells also contain nuclear inclusions, reminiscent of those seen in paramyxovirus-infected cells, which cross-react with antibodies to measles virus nucleocapsid (MVNP) antigen. To elucidate the role of MV in the abnormal OCL phenotype of Paget's disease, we transduced normal OCL precursors with retroviral vectors expressing MVNP and the MV matrix (MVM) genes. The transduced cells were then cultured with 1,25-(OH)(2)D(3) for14 or 21 days to induce formation of OCL-like multinucleated cells. The MVNP-transduced cells formed increased numbers of multinucleated cells, which contained many more nuclei and had increased resorption capacity compared with multinucleated cells derived from empty vector-transduced (EV-transduced) and MVM-transduced or normal bone marrow cells. Furthermore, MVNP-transduced cells showed increased sensitivity to 1, 25-(OH)(2)D(3), and formed OCLs at concentrations of 1, 25-(OH)(2)D(3) that were 1 log lower than that required for normal, EV-transduced, or MVM-transduced cells. These results demonstrate that expression of the MVNP gene in normal OCL precursors stimulates OCL formation and induces OCLs that express a phenotype similar to that of pagetic OCLs. These results support a potential pathophysiologic role for MV infection in the abnormal OCL activity and morphology that are characteristic of pagetic OCLs.

Measles virus nucleocapsid transcript expression is not restricted to the osteoclast lineage in patients with Paget's disease of bone

Abundant evidence supports a viral etiology for Paget's disease of bone (PD), however, an infectious virus has not been isolated from PD patients. Thus, it is unclear how the virus is maintained for the many years that the disease persists in patients. We considered if a primitive multipotential hematopoietic stem cell (HSC), which is self-renewing, passes the virus to its differentiated progeny and serves as a reservoir for the pathogen. If a primitive stem cell harbored measles virus (MV), then other hematopoietic lineages derived from this stem cell in PD patients should also express MV transcripts. Therefore, because the human hematopoietic stem cell has not been clearly identified or isolated in large numbers, we isolated RNA from highly purified erythroid and multipotential hematopoietic progenitors that are the precursors for erythroid, granulocyte, megakaryocyte and macrophages (CFU-GEMM), and used RT-PCR to determine if MV nucleocapsid transcripts were present. MV transcripts were detected in PD patients in early erythroid (BFU-E) and more primitive multipotential myeloid progenitors (CFU-GEMM). Nonhematopoietic stromal cells from PD patients did not express MV transcripts. The expression of MV transcripts in erythroid progenitors was further confirmed by in situ hybridization using antisense riboprobes to MV nucleocapsid transcripts. Thus, our findings suggest that the pluripotent HSCs may be a potential reservoir for the virus. We propose that when HSCs, which contain MV, divide they produce a second HSC that serves as a reservoir for the virus and also transmit the virus to their more differentiated progeny in the erythroid and myeloid lineages. This mechanism would permit a defective virus to persist in HSCs of PD patients for many years, since HSCs are usually in G0 phase, and then be transmitted to more differentiated cells. This model further suggests that a mature complete virus that affects cell function could only act pathogenetically in the osteoclast lineage, which offers a permissive milieu.

Detection of canine distemper virus in 100% of Paget's disease samples by in situ-reverse transcriptase-polymerase chain reaction

Previous evidence implicating paramyxoviruses in the aetiopathology of Paget's disease of bone has been controversial. While several groups have demonstrated the presence of paramyxoviruses using electron microscopy, immunohistochemistry, and molecular biological techniques, others have found no evidence of viruses using reverse transcriptase-polymerase chain reaction (RT-PCR). We have previously provided evidence that canine distemper virus (CDV) is present in approximately 65% of samples of pagetic bone, using in situ hybridization and RT-PCR; however, these results have been criticized. To further investigate the possible Role of CDV, we have now developed the technique of in situ-RT-PCR (IS-RT-PCR) to examine for the presence of CDV-nucleocapsid (CDV-N) ribonucleic acid (RNA) in pagetic bone. Control samples consisted of uninvolved sites from patients with the disease, normal bone, and several active remodeling states. IS-RT-PCR was optimized to detect CDV-N using distemper-infected vero cells. The specificity of the technique was confirmed using vero cells infected with CDV, which showed amplified signal following IS-RT-PCR, and cells infected with measles virus (MV), in which no positive signal for CDV was detected by IS-RT-PCR. Following conventional in situ hybridization, CDV-N was detectable in 10 of 15 pagetic bone samples. However, after five, and particularly 10, cycles of IS-RT-PCR, CDV-N was found in all 15 samples. There was no evidence of CDV in four samples from uninvolved sites from pagetic patients, or in any of the other control samples. In this study, using the novel technique of IS-RT-PCR, CDV was found to be present in 100% of pagetic samples examined. There was no evidence of the virus in any of the control samples, including samples of bone from uninvolved sites from patients with Paget's disease. These results provide additional proof that CDV is present within pagetic bone and further support the hypothesis that paramyxoviruses are involved in the etiopathology of Paget's disease.

Respiratory syncytial virus RNA in cells from the peripheral blood during acute infection

It is not known whether respiratory syncytial virus spreads beyond the respiratory tract. With the use of reverse transcriptase polymerase chain reaction, we found viral and transcribed RNA in cells from the arterial blood of four children with bronchiolitis but none in serum or cerebrospinal fluid. Respiratory syncytial virus might therefore spread outside the respiratory tract.

Paget's disease of bone: indications for treatment and goals of therapy

Paget's disease of bone is a common disorder of unknown etiology characterized by increased bone remodeling and abnormal bone architecture. The pathologic process is initiated by an increase in osteoclast-mediated bone resorption, accompanied by a compensatory increase in bone formation. The increased bone remodeling results in a disorganized mosaic of woven and lamellar bone. This bone is highly vascular and gradually becomes enlarged and structurally weakened. Paget's disease is generally diagnosed in patients older than 40 years of age, usually as an incidental finding. The disease may be monostotic or polyostotic. The pelvis, femur, spine, tibia, skull, and humerus are most commonly involved. Most patients with Paget's disease are asymptomatic. Pain is the most common presenting symptom. Complications of the disease include bowing deformity of the long bones, fracture, and a variety of nerve compression syndromes. Malignant degeneration of Paget's disease is a rare complication. As safer, more effective therapies have become available, the indications for treatment and goals of therapy have changed. The difficult issue that clinicians are currently facing is whether to treat patients with asymptomatic disease. The progressive nature of the disease, the severity of its complications, its potential negative impact on quality of life, and the availability of therapy capable of controlling its activity have led many experts in the field to recommend treatment of asymptomatic patients who have active disease at sites where complications are likely to develop. There are, however, no data to prove that complications can be prevented by decreasing the rate of bone remodeling in Paget's disease, nor any data to define who is at risk for complications. Until more information is available, the management of patients with Paget's disease will continue to be based on clinical observation and theoretical considerations. This review examines the present understanding of Paget's disease, the rationale for the proposed indications for treatment and the goals of therapy.

Paget bone disease involving young adults in 3 generations of a Korean family

Although the etiology of Paget bone disease (PBD) is unknown, increasing evidence implicates a "slow virus" infection of the skeleton, perhaps in genetically predisposed individuals. PBD is rare in Asia. We describe a Korean family with PBD. The propositus noticed bowed limbs at approximately 25 years of age. Radiologic studies made when he was 55 years old revealed essentially panostotic PBD. Serum alkaline phosphatase (ALP) activity and osteocalcin (OC) levels were markedly elevated. An iliac crest specimen showed classic histopathologic changes of PBD. Additionally, palpable swellings were first observed at age 45 years at his occiput, pubic ramus, ileum, and facial bones. They contained numerous multinucleated cells and were originally diagnosed as giant cell tumors. However, we found that, like osteoclasts, these cells expressed considerable tartrate-resistant acid phosphatase activity. These "extraskeletal osteoclastomas" resolved rapidly with dexamethasone treatment. Two daughters, 20- and 24-years-of-age, were discovered by study of his 5 children to have elevated serum ALP activity and OC levels and widespread PBD. Both women, however, are without palpable masses and are asymptomatic. The propositus' father, who died at age 55 years, had similar skeletal deformities beginning at age 20 years, but was not examined. Leukocytopenia was found in the 3 living family members with PBD. There was no evidence for linkage of the PBD to HLA loci. The condition appears to be transmitted as an autosomal dominant trait and is manifest in young adult life. Multicentric extraskeletal osteoclastomas with remarkable sensitivity to dexamethasone treatment appear to be another unusual feature of this family's disorder. In this family, the stimulus for PBD is so great that the PBD is apparent at an early age, affects essentially the entire skeleton, and leads to the formation or extension of osteoclast-like cells into nonosseous tissues (extraskeletal osteoclastomas). This 3-generation kindred in Korea, where PBD is rare, shows a strong clustering of PBD compatible with autosomal dominant inheritance. Leukocytopenia appears to distinguish affected family members, but any role for this abnormality in the pathogenesis of PBD is unclear. Our findings support a heritable diathesis for PBD, perhaps mediated by an immune deficiency.

Detection of measles virus nucleocapsid transcripts in circulating blood cells from patients with Paget disease

Paget disease of bone is characterized by abnormalities in all phases of bone remodeling, but the fundamental cellular abnormality resides in the osteoclast (OCL). Osteoclasts in bone involved by Paget disease contain viral-like nuclear and cytoplasmic inclusions that react with antibodies directed against paramyxovirus nucleocapsid proteins, such as measles virus, respiratory syncytial virus, or canine distemper virus. However, the identity of the virus or the mechanisms responsible for its persistence or pathologic role in Paget disease is unclear. Furthermore, although Paget disease persists for many years, it remains a highly localized process with new lesions rarely if ever developing in previously unaffected bones. Since osteoclasts are formed by fusion of mononuclear precursors derived from colony forming unit-granulocyte macrophage (CFU-GM), the granulocyte-macrophage progenitor, we used reverse transcriptase polymerase chain reaction (RT-PCR) analysis to determine if CFU-GM, more differentiated osteoclast precursors, and peripheral blood cells derived from CFU-GM express measles virus nucleocapsid (MV-N) transcripts. We found that osteoclast precursors, as well as peripheral blood mononuclear cells, express MV transcripts in 9 of 13 patients. Sequence analysis of the PCR amplified products confirmed nucleotide identity of MV-N transcripts expressed in peripheral blood and bone marrow-derived cells from the same patient. In contrast, MV-N transcripts were not detected in OCL precursors or the peripheral blood from 10 normal subjects. In situ hybridization studies using 35S-labeled antisense riboprobes to MV-N transcripts further confirmed the expression of MV transcripts in these cells. Sequence analysis of the PCR amplified product from one of these patients also identified a novel mutation that converted lysine441 to glutamic acid441 in the MV-N transcript. These data demonstrate that OCL precursors and circulating peripheral blood cells also express MV transcripts in patients with Paget disease and suggest that the pagetic marrow microenvironment plays a critical role in maintaining the highly localized nature of the lesions in Paget disease.

The effect on chick osteoclasts of infection with paramyxoviruses

The detection of virus in osteoclasts from Pagetic patients is now well known, but it has yet to be shown convincingly that the presence of virus in Pagetic osteoclasts influences their behaviour. In this study, osteoclasts from embryonic chick tibiae were infected with canine distemper virus or measles virus and compared with mock-infected controls. Infection was confirmed using virus-specific fluorescent antibodies. It was found that virus infection did not alter osteoclast morphology or tartrate-resistant acid phosphatase (TRAP) activity. Both infected and mock-infected osteoclasts produced resorption pits on bovine bone slices; these could be divided into two distinct size classes with a computer-based measuring system. Virus infection significantly increased the proportion of the larger size class of resorption pit. These results suggest that virus infection can increase bone resorption by osteoclasts, lending further support to the hypothesis that viruses play a role in Paget's disease of bone.

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.

Viral behavior of paracrystalline inclusions in osteoclasts of Paget's disease of bone

Fresh tissues from six patients with Paget's disease of bone were examined ultrastructurally to investigate whether the characteristic paracrystalline inclusions in pagetic osteoclasts revealed viral behavior. These inclusions appeared as microfilamentous aggregates in both nuclei and cytoplasm of the osteoclasts in all six cases. The filamentous elements of the inclusions with a diameter of 11-15 nm showed tubular structures with a central electron-lucent zone measuring 5-7 nm in diameter. Viral budding-like structures containing these inclusions were found at the peripheral cytoplasm or cell processes in the ruffled border of some pagetic osteoclasts in two cases. The inclusions in the budding-like structures were often arrayed in a parallel fashion on the cytoplasmic side of the cell membranes of extruded cytoplasm or cell processes. Virion-like particles were also found in the extracellular spaces of the ruffled border. Marked nuclear degeneration was often seen in pagetic osteoclasts of three cases, although other nuclei in the same osteoclasts appeared normal. The degenerated nuclei showed nuclear ring formation where destroyed nuclear membranes were seen and disappearance of nuclear matrices was noted. Since the modifications were always associated with the accumulation of abundant inclusions, they were probably caused by the inclusions. These findings suggested that the inclusions showed viral behavior in pagetic osteoclasts, and that the nuclear modifications were caused by virus infection.

Upregulation of c-fos protooncogene expression in pagetic osteoclasts

Using in situ hybridization we show that expression of the c-fos oncogene, a gene normally associated with osteosarcomas, is greatly elevated in osteoclasts of patients with Paget's disease. Immunohistochemical staining with c-fos antibodies also shows increased protein in pagetic osteoclasts. In light of transgenic mouse experiments showing a key role for c-fos in bone resorption, we propose that elevated c-fos gene expression in pagetic osteoclasts is an important component in producing the pagetic phenotype. Levels of c-fos gene and protein expression in pagetic osteoblasts are lower than those detected in osteoclasts but still higher than in nonpagetic osteoblasts. This may provide an explanation for the increased incidence of osteosarcomas in patients with Paget's disease because overexpression of c-fos in osteoblasts of transgenic mice induces osteosarcoma formation.

Interleukin-6, IL-6 receptor, and IL-6 nuclear factor gene expression in Paget's disease

The cytokine interleukin-6 (IL-6) is considered an important regulator of bone cell function and may play a central role in bone disease states characterized by increased bone remodeling, such as Paget's disease. Indeed, recent in vitro data suggest that IL-6 may be an autocrine/paracrine factor for pagetic osteoclasts. However, its expression and role in vivo are not known. Using in situ hybridization we investigated the spatial localization of expression of IL-6, IL-6 receptor (IL-6R), and the transcription factor (NF-IL-6) in pagetic bone. Our results show that osteoblasts in the normal remodeling bone of osteoarthritis (controls) and in Paget's disease express IL-6, IL-6R, and NF-IL-6 genes with higher levels of IL-6 and IL-6R mRNA in pagetic bone. Osteoclasts in both osteoarthritic and pagetic bone express IL-6R mRNA and NF-IL-6, but only pagetic osteoclasts expressed IL-6, suggesting that in Paget's disease IL-6 can act as an autocrine factor on osteoclasts. These results provide evidence for a major role of the IL-6 regulatory pathway in the phenotype of the pagetic osteoclasts and lead us to suggest a model linking possible paramyxovirus infection and IL-6 regulation in the pagetic osteoclast.

Electron microscopic evidence of a viral nature for osteoclast inclusions in Paget's disease of bone

Circumstantial evidence from electron microscopic and immunological studies support the view that Paget's disease of bone represents a slow virus infection. However, there is only limited information available regarding its electron microscopic, enzyme and immunocytochemical characteristics. Two cases were studied using electron microscopy with particular emphasis on the inclusions in osteoclasts. Detailed ultrastructural and cytochemical studies including immuno-electron microscopy were performed. Some osteoclasts demonstrated specific virus-like structures composed of aggregations of microtubules in the nucleus and cytoplasm. The structures were easily digested by trypsin or protease, and were sensitive to RNase, which provided substantial evidence of a proteinaceous nature and inclusion of ribonucleic acid. Immunocytochemical examination identified binding of anti-respiratory syncytial virus and anti-measles virus antibodies in the tissue obtained from one of the two cases examined. The presence of viral antigens in structures in the cytoplasm of Pagetic osteoclasts supports the theory of paramyxovirus involvement in this disease.

Case report 806: Monostotic Paget's disease of the hand (fifth metacarpal)

Monostotic Paget's disease of bone is an uncommon disease, reported in the hand in only a few instances. We have described an additional case involving a metacarpal bone in a 43-year-old man. We believe this disease should be considered in the radiological differential diagnosis of lytic expansile, subchondral lesions of the hand.

Dogs, distemper and Paget's disease

The cause of Paget's disease is still unknown, despite many years of intensive study. During this time, evidence has sporadically emerged to suggest that the disease may result from a slow viral infection by one or more of the Paramyxoviruses. More recently, epidemiologic and molecular studies have suggested that the canine paramyxovirus, canine distemper virus, is the virus responsible for the disease. If true, then along with rabies, this would be a further example of a canine virus causing human disease. Studies in the natural host have now supported these findings. Further investigations have proposed that the bony abnormalities seen in Paget's disease are due to the effects of the virus on osteoclastic interleukin-6 and c-FOS production, possibly via the transcription factor NF-kappa B.

PCR detection of cytokines in normal human and pagetic osteoblast-like cells

We investigated the expression of cytokine transcripts in osteoblast-like cells derived from explants of pagetic and normal bone. A reverse transcription-linked PCR was used that allowed the simultaneous analysis of a range of cytokines. Normal osteoblast-like cells were found to contain the transcripts for IL-1 beta, IL-6, and TGF-beta 1. For the first time we detected in bone cells the two other mammalian isoforms of TGF-beta, beta 2, and beta 3. Furthermore, we have also identified mRNA for IL-3 and the novel chemotactic factor, IL-8. Using this sensitive technique it was not possible to detect mRNA for IL-1 alpha, IL-2, IL-4, IL-5, IL-7, TNF-alpha, or interferon-gamma. The human osteosarcoma cell line Saos-2 also showed a similar pattern of expression of these cytokines to primary osteoblast-like cells, with the exception that TNF-alpha was also identified. Cells isolated from pagetic bone showed essentially the same profile of cytokine expression as normal bone except that TNF-alpha was also detected in two of four samples. The cytokine profile of successive populations of cells harvested from one explant culture at 9, 22, and 57 days showed a consistent pattern of cytokine expression, demonstrating the phenotypic stability of the osteoblast-like cells in long-term cultures.

Prevalence of canine distemper antibodies in the pagetic population

Recent molecular evidence has implicated canine distemper virus (CDV) as a possible aetiologic agent in Paget's disease. However, previous serological studies have shown no differences in levels of anti-CDV antibodies between Paget's patients and controls. In this study, the technique of enzyme linked immunosorbent assay was used to measure anti-CDV antibodies in a group of Paget's patients from the North West of England. Some patients were undergoing treatment with 3-amino-hydroxypropylidene (APD), and the pre-treatment levels of antibody were compared with those following treatment. With several patients, it was also possible to compare the antibody levels with results from in situ hybridisation studies. No significant difference was found between the levels of anti-CDV antibodies in patients and controls. However, several patients and some of the controls did have markedly elevated levels of anti-CDV antibody. Antibody levels remained fairly constant following treatment with APD, except for two patients who showed marked changes. The patients positive for CDV by in situ hybridisation had significantly lower levels of anti-CDV antibodies when compared with those that were negative by in situ hybridisation. These results suggest that if CDV does cause Paget's disease, anti-CDV antibodies play little or no part in the disease pathogenesis. High levels of anti-CDV antibodies in both Paget's patients and controls suggest that a canine virus can infect humans. The fact that those patients that had CDV transcripts detectable in their bone cells had low levels of anti-CDV antibodies might suggest failure to clear the virus during an initial infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Paramyxoviruses and Paget's disease

Using the technique of in situ hybridisation, we extended our initial studies of the occurrence of canine distemper and measles virus in Paget's disease. Bone samples from untreated patients and patients treated with 3-amino-hydroxypropylidene 1,1 bisphosphonate pamidronate (APD) were examined for canine distemper nucleocapsid (CDV-N), measles nucleocapsid (MV-N), respiratory syncytial virus fusion (RSV-F), and simian virus 5 haemoglutinin-neuraminidase (SV5-HN) sequences using 35S-labelled sense and antisense riboprobes. Only CDV-N mRNA was detected in osteoclasts, osteoblasts, and mononuclear cells. In untreated Paget's patients, 63.5% were found to have CDV sequences residing in bone cells, and 48.2% of those undergoing APD treatment were still found to have the viral sequences. RSV-F mRNA was only found in one patient. None of the other paramyxoviruses tested were detected. This study shows that CDV can infect a human host and may be an aetiological agent of Paget's disease of bone.

Paramyxovirus-like nuclear inclusions identical to those of Paget's disease of bone detected in giant cells of primary oxalosis

Nuclear inclusions, identical to those characteristic of Paget's disease of bone, were observed in giant cells in four of eight cases of primary oxalosis. The giant cells containing nuclear inclusions were directly involved in phagocytosis of large oxalate crystals in the context of typical foreign body granulomas in the bone marrow. Cytochemically, all of them exhibited strong tartrate-resistant acid phosphatase activity, and a proportion of them also tartrate-resistant acid ATPase. The inclusions consisted of typical arrays of filamentous material as described in Paget's disease, admixed with variable proportions of electron-dense material closely reminiscent of nucleolar pars fibrillaris and fibrillary centres. These data indicate: (a) the occurrence of Paget-like inclusions in a bone disease unrelated to Paget's disease, not causally related to viral infection, and resulting from an inborn metabolic derangement; and (b) the occurrence of Paget-like inclusions in foreign body giant cells as opposed to osteoclasts. We suggest that the occurrence of paramyxovirus-like nuclear inclusions in either osteoclasts or giant cells may represent an epiphenomenon of cell fusion and giant cell formation whenever appropriate stimuli act on latently infected precursor cells. Furthermore, our data suggest that nucleoli may represent the specific site of virus-like inclusion formation.

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.

Failure to detect paramyxovirus sequences in Paget's disease of bone using the polymerase chain reaction

It is widely believed that Paget's disease of bone is due to a "slow virus" infection of osteoclasts with one of the paramyxovirus group. Controversy continues to surround the identity of the virus involved, however, since at different times evidence has been presented implicating measles virus (MV), respiratory syncytial virus (RSV), and canine distemper virus (CDV) as putative infective agents. In this study we used the technique of reverse transcription and polymerase chain reaction (PCR) to screen for paramyxovirus sequences in ribonucleic acid (RNA) extracted from pagetic bone. We were able to detect viral amplification products of the appropriate size in RNA extracted from as few as 50 cells experimentally infected with a wide range of paramyxoviruses, including measles, canine distemper, parainfluenza 3, and respiratory syncytial virus, but we found no evidence of viral products in RNA extracts of affected bone from 10 consecutive patients with Paget's disease. This study fails to support the hypothesis that active infection with one of these or a related paramyxovirus is involved in the pathogenesis of Paget's disease.

Sarcomatous degeneration in Paget's bone disease

The authors report 12 cases (8 men and 4 women) of sarcomatous degeneration in Paget's bone disease, with an average age of 72.3 years. Sarcomatous degeneration occurred often in polyostotic Paget's disease, and osteitis deformans was seen in 4 cases. Femur and pelvis were the most affected bones. Pain was a constant feature, whereas tumefaction and fracture were less common. Osteolytic lesions were more frequent than condensed or mixed lesions and radiological signs of malignancy were usually found. Seven cases were histologically classified as osteogenic sarcoma and 3 cases as fibrosarcoma. Electron microscopy was performed on 2 osteogenic sarcomas and in 1 case revealed microcylindrical inclusions in Pagetic osteoclasts and in multinucleated giant tumor cells, but none in mononucleated tumor cells. The average survival time for the patients in this study was only 4.5 months.

Local and systemic antibody response to bovine respiratory syncytial virus infection and reinfection in calves with and without maternal antibodies

Enzyme-linked immunosorbent assays for the detection of immunoglobulin M (IgM), IgA, IgG1, and IgG2 antibodies against bovine respiratory syncytial virus (BRSV) were used to measure antibody responses of calves after experimental or natural infection with BRSV. Serially collected sera, lung lavage samples, nasal and eye secretions, and feces were tested for the presence of these antibodies. Lung lavage fluids and nasal secretions were further examined for the presence of virus. After experimental infection of 3- to 4-week-old, colostrum-deprived (seronegative) calves, the virus was detected from days 3 to 8 post-initial inoculation day (PID). An immune response was first detected 8 to 10 days PID, when BRSV-specific IgM and IgA appeared nearly simultaneously in serum, secretions, and feces. BRSV-specific IgG1 appeared only in serum on days 13 to 17 PID, and IgG2 was first detected in sera from 1 to 3 months PID. Specific IgM and IgA were detectable in the different samples for various periods. In the respiratory and eye secretions, IgA usually remained detectable for long periods, that is, for up to 3.5 months or longer. In lung lavage samples, BRSV-specific IgG1 was only incidentally demonstrated and appeared to be blood derived. The immune response of a 5-month-old calf strongly resembled that of the 3- to 4-week-old calves (feces excepted), indicating that an age effect on the immune response to BRSV is unlikely. After experimental infection of colostrum-fed, seropositive calves, both local and systemic antibody responses were largely or totally suppressed. The degree of suppression seemed to be related to the level of preinoculation virus-specific serum IgG1. Of all isotypes, IgM was least affected. Colostrum-fed animals shed virus in about equal amounts and for the same length of time as colostrum-deprived calves. Clinical signs were mild in both groups. After reinfection, no virus shedding was detected in either colostrum-deprived or colostrum-fed calves. In both groups, a secondary immune response developed, characterized by strong and rapid (from about day 6 PID) mucosal and systemic IgA responses, but reaching higher titers in colostrum-deprived calves. Also, strong mucosal, but not serum, IgM responses were observed, which, however, did not develop faster than those observed after primary infection. Naturally infected calves, showing severe signs of respiratory disease, had various levels of, most likely, maternally derived antibodies on the first day of illness. Mucosal and systemic antibody responses of various heights and durations were observed, but in general these responses were stronger than those observed after experimental infection. The results point to an important role for local IgA, rather for serum IgG1, in the protection against BRSV infection. The capacity to mount a local memory IgA response seems especially important. Priming for such a mucosal memory response is possible even when the primary immune response is severely suppressed because of the presence of material antibodies.

A survey of respiratory syncytial virus and parainfluenza virus type 3 neutralising and immunoprecipitating antibodies in relation to Paget disease

The aetiology of Paget disease of bone has not been established but certain features have suggested involvement of a parainfluenzalike virus. To seek further evidence of the possible role of paramyxoviruses in Paget disease we have surveyed the presence of neutralising and immunoprecipitating antibodies to both respiratory syncytial virus and parainfluenza virus type 3 in the sera of patients attending a bone disease clinic. These two viruses were implicated by the sporadic observation of viral antigen in individual nuclei of osteoclasts in Paget disease bone lesions. A total of 315 samples were obtained from 177 patients attending the clinic during 1 year. Thirty-six of the patients had confirmed Paget disease and the remainder other conditions. All sera possessed neutralising activity to both viruses. The mean titres for each virus were similar in patients with Paget disease and those with other conditions whether matched or not. In the case of respiratory syncytial virus the neutralising titres were distributed closer to the mean in the Paget group and showed little variation in repeat samples taken over periods of up to 1 year in contrast to the greater variability of the control group. The antigenic specificity of 20 age- and sex-matched sera from each group was examined by immunoprecipitation. No significant differences were observed between Paget and non-Paget patients. These results do not provide confirmation of involvement of either virus in Paget disease, but the serological data suggest that persistent infection with respiratory syncytial virus can occur.

A family study of Paget's disease of bone

Familial aggregation of Paget's disease of bone occurs occasionally and an exclusively genetic aetiology has been proposed in the past. On the other hand, epidemiological surveys point to an important environmental contribution, and evidence is accumulating to suggest that the disease may be caused by a slow virus infection. Analysis of 407 family history questionnaires completed by patients with Paget's disease confirmed the familial nature of the disease. Overall, the findings were consistent with the hypothesis that Paget's disease is caused by infection with a common and widespread virus superimposed on genetic variation for susceptibility and perhaps severity of the disease.