Absence of persistent infection with enteroviruses in muscles of patients with inflammatory myopathies

Autoimmune inflammatory myopathies

The autoimmune inflammatory myopathies constitute a heterogeneous group of acquired myopathies that have in common the presence of endomysial inflammation and moderate to severe muscle weakness. Based on currently evolved distinct clinical, histologic, immunopathologic, and autoantibody features, these disorders can be best classified as dermatomyositis, necrotizing autoimmune myositis, antisynthetase syndrome-overlap myositis, and inclusion body myositis. Although polymyositis is no longer considered a distinct subset but rather an extinct entity, it is herein described because its clinicopathologic information has provided over many years fundamental information on T-cell-mediated myocytotoxicity, especially in reference to inclusion body myositis. Each inflammatory myopathy subset has distinct immunopathogenesis, prognosis, and response to immunotherapies, necessitating the need to correctly diagnose each subtype from the outset and avoid disease mimics. The paper describes the main clinical characteristics that aid in the diagnosis of each myositis subtype, highlights the distinct features on muscle morphology and immunopathology, elaborates on the potential role of autoantibodies in pathogenesis or diagnosis , and clarifies common uncertainties in reference to putative triggering factors such as statins and viruses including the 2019-coronavirus-2 pandemic. It extensively describes the main autoimmune markers related to autoinvasive myocytotoxic T-cells, activated B-cells, complement, cytokines, and the possible role of innate immunity. The concomitant myodegenerative features seen in inclusion body myositis along with their interrelationship between inflammation and degeneration are specifically emphasized. Finally, practical guidelines on the best therapeutic approaches are summarized based on up-to-date knowledge and controlled studies, highlighting the prospects of future immunotherapies and ongoing controversies.

Guidelines on dermatomyositis--excerpt from the interdisciplinary S2k guidelines on myositis syndromes by the German Society of Neurology

The present guidelines on dermatomyositis (DM) represent an excerpt from the interdisciplinary S2k guidelines on myositis syndromes of the German Society of Neurology (available at www.awmf.org). The cardinal symptom of myositis in DM is symmetrical proximal muscle weakness. Elevated creatine kinase, CRP or ESR as well as electromyography and muscle biopsy also provide important diagnostic clues. Pharyngeal, respiratory, cardiac, and neck muscles may also be affected. Given that approximately 30% of patients also develop interstitial lung disease, pulmonary function tests should be part of the diagnostic workup. Although the cutaneous manifestations in DM are variable, taken together, they represent a characteristic and crucial diagnostic criterion for DM. Approximately 5-20% of individuals exhibit typical skin lesions without any clinically manifest muscle involvement (amyopathic DM). About 30% of adult DM cases are associated with a malignancy. This fact, however, should not delay the treatment of severe myositis. Corticosteroids are the therapy of choice in myositis (1-2 mg/kg). Additional immunosuppressive therapy is frequently required (azathioprine, for children methotrexate). In case of insufficient therapeutic response, the use of intravenous immunoglobulins is justified. The benefit of rituximab has not been conclusively ascertained yet. Acute therapeutic management is usually followed by low-dose maintenance therapy for one to three years. Skin lesions do not always respond sufficiently to myositis therapy. Effective treatment for such cases consists of topical corticosteroids and sometimes also calcineurin inhibitors. Systemic therapies shown to be effective include antimalarial agents (also in combination), methotrexate, and corticosteroids. Intravenous immunoglobulins or rituximab may also be helpful. UV protection is an important prophylactic measure.

Pathophysiology of inflammatory and autoimmune myopathies

The main subtypes of inflammatory myopathies include dermatomyositis (DM), polymyositis (PM), necrotizing autoimmune myositis (NAM) and sporadic inclusion-body myositis (sIBM). The review provides an update on the main clinical characteristics unique to each subset, including fundamental aspects on muscle pathology helpful to assure accurate diagnosis, underlying immunopathomechanisms and therapeutic strategies. DM is a complement-mediated microangiopathy leading to destruction of capillaries, distal hypoperfusion and inflammatory cell stress on the perifascicular regions. NAM is an increasingly recognized subacute myopathy triggered by statins, viral infections, cancer or autoimmunity with macrophages as the final effector cells mediating fiber injury. PM and IBM are characterized by cytotoxic CD8-positive T cells which clonally expand in situ and invade MHC-I-expressing muscle fibers. In IBM, in addition to autoimmunity, there is vacuolization and intrafiber accumulation of degenerative and stressor molecules. Pro-inflammatory mediators, such as gamma interferon and interleukin IL1-β, seem to enhance the accumulation of stressor and amyloid-related misfolded proteins. Current therapies using various immunosuppressive and immunomodulating drugs are discussed for PM, DM and NAM, and the principles for effective treatment strategies in IBM are outlined.

Interactions between multiple genetic determinants in the 5' UTR and VP1 capsid control pathogenesis of chronic post-viral myopathy caused by coxsackievirus B1

Mice infected with coxsackievirus B1 Tucson (CVB1(T)) develop chronic, post-viral myopathy (PVM) with clinical manifestations of hind limb muscle weakness and myositis. The objective of the current study was to establish the genetic basis of myopathogenicity in CVB1(T). Using a reverse genetics approach, full attenuation of PVM could only be achieved by simultaneously mutating four sites located at C706U in the 5' untranslated region (5' UTR) and at Y87F, V136A, and T276A in the VP1 capsid. Engineering these four myopathic determinants into an amyopathic CVB1(T) variant restored the ability to cause PVM. Moreover, these same four determinants controlled PVM expression in a second strain of mice, indicating that the underlying mechanism is operational in mice of different genetic backgrounds. Modeling studies predict that C706U alters both local and long range pairing in the 5' UTR, and that VP1 determinants are located on the capsid surface. However, these differences did not affect viral titers, temperature stability, pH stability, or the antibody response to virus. These studies demonstrate that PVM develops from a complex interplay between viral determinants in the 5' UTR and VP1 capsid and have uncovered intriguing similarities between genetic determinants that cause PVM and those involved in pathogenesis of other enteroviruses.

Advances in the immunobiology and treatment of inflammatory myopathies

The clinical spectrum and immunopathogenesis of inflammatory myopathies are summarized with an update on possible triggering factors, cell degeneration, and emerging new therapies.

Detection of enterovirus in human skeletal muscle from patients with chronic inflammatory muscle disease or fibromyalgia and healthy subjects

Enterovirus RNA has been found previously in specimens of muscle biopsy from patients with idiopathic dilated cardiomyopathy, chronic inflammatory muscle diseases, and fibromyalgia or chronic fatigue syndrome (fibromyalgia/chronic fatigue syndrome). These results suggest that skeletal muscle may host enteroviral persistent infection. To test this hypothesis, we investigated by reverse transcription-polymerase chain reaction (RT-PCR) assay the presence of enterovirus in skeletal muscle of patients with chronic inflammatory muscle diseases or fibromyalgia/chronic fatigue syndrome, and also of healthy subjects. Three of 15 (20%) patients with chronic inflammatory muscle diseases, 4 of 30 (13%) patients with fibromyalgia/chronic fatigue syndrome, and none of 29 healthy subjects was found positive. The presence of VP-1 enteroviral capsid protein was assessed by an immunostaining technique using the 5-D8/1 monoclonal antibody; no biopsy muscle from any patient or healthy subject was found positive. The presence of viral RNA in some muscle biopsies from patients exhibiting muscle disease, together with the absence of VP-1 protein, is in favor of a persistent infection involving defective viral replication.

Enterovirus related metabolic myopathy: a postviral fatigue syndrome

OBJECTIVE

To detect and characterise enterovirus RNA in skeletal muscle from patients with chronic fatigue syndrome (CFS) and to compare efficiency of muscle energy metabolism in enterovirus positive and negative CFS patients.

METHODS

Quadriceps muscle biopsy samples from 48 patients with CFS were processed to detect enterovirus RNA by two stage, reverse transcription, nested polymerase chain reaction (RT-NPCR), using enterovirus group specific primer sets. Direct nucleotide sequencing of PCR products was used to characterise the enterovirus. Controls were 29 subjects with normal muscles. On the day of biopsy, each CFS patient undertook a subanaerobic threshold exercise test (SATET). Venous plasma lactate was measured immediately before and after exercise, and 30 minutes after testing. An abnormal lactate response to exercise (SATET+) was defined as an exercise test in which plasma lactate exceeded the upper 99% confidence limits for normal sedentary controls at two or more time points.

RESULTS

Muscle biopsy samples from 20.8% of the CFS patients were positive for enterovirus sequences by RT-NPCR, while all the 29 control samples were negative; 58.3% of the CFS patients had a SATET+ response. Nine of the 10 enterovirus positive cases were among the 28 SATET+ patients (32.1%), compared with only one (5%) of the 20 SATET- patients. PCR products were most closely related to coxsackie B virus.

CONCLUSIONS

There is an association between abnormal lactate response to exercise, reflecting impaired muscle energy metabolism, and the presence of enterovirus sequences in muscle in a proportion of CFS patients.

Polymyositis and dermatomyositis

The inflammatory myopathies, commonly described as idiopathic, are the largest group of acquired and potentially treatable myopathies. On the basis of unique clinical, histopathological, immunological, and demographic features, they can be differentiated into three major and distinct subsets: dermatomyositis, polymyositis, and inclusion-body myositis. Use of new diagnostic criteria is essential to discriminate between them and to exclude other disorders. Dermatomyositis is a microangiopathy affecting skin and muscle; activation and deposition of complement causes lysis of endomysial capillaries and muscle ischaemia. In polymyositis and inclusion-body myositis, clonally expanded CD8-positive cytotoxic T cells invade muscle fibres that express MHC class I antigens, which leads to fibre necrosis via the perforin pathway. In inclusion-body myositis, vacuolar formation with amyloid deposits coexists with the immunological features. The causative autoantigen has not yet been identified. Upregulated vascular-cell adhesion molecule, intercellular adhesion molecule, chemokines, and their receptors promote T-cell transgression, and various cytokines increase the immunopathological process. Early initiation of therapy is essential, since both polymyositis and dermatomyositis respond to immunotherapeutic agents. New immunomodulatory agents currently being tested in controlled trials may prove promising for difficult cases.

Clonal tracking of autoaggressive T cells in polymyositis by combining laser microdissection, single-cell PCR, and CDR3-spectratype analysis

Clonal expansions of CD8+ T cells have been identified in muscle and blood of polymyositis patients by PCR techniques, including T cell receptor (TCR) complementarity-determining region (CDR)3 length analysis (spectratyping). To examine a possible pathogenic role of these clonally expanded T cells, we combined CDR3 spectratyping with laser microdissection and single-cell PCR of individual myocytotoxic T cells that contact, invade, and destroy a skeletal muscle fiber. First, we screened cDNA from muscle biopsy specimens by CDR3 spectratyping for expanded TCR beta chain variable region (BV) sequences. To pinpoint the corresponding T cells in tissue, we stained cryostat sections with appropriate anti-TCR BV mAbs, isolated single BV+ T cells that directly contacted or invaded a muscle fiber by laser-assisted microdissection, and amplified their TCR BV chain sequences from rearranged genomic DNA. In this way, we could relate the oligoclonal peaks identified by CDR3-spectratype screening to morphologically characterized microdissected T cells. In one patient, a large fraction of the microdissected T cells carried a common TCR-BV amino acid CDR3 motif and conservative nucleotide exchanges in the CDR3 region, suggesting an antigen-driven response. In several cases, we tracked these T cell clones for several years in CD8+ (but not CD4+) blood lymphocytes and in two patients also in consecutive muscle biopsy specimens. During immunosuppressive therapy, oligoclonal CDR3-spectratype patterns tended to revert to more polyclonal Gaussian distribution-like patterns. Our findings demonstrate that CDR3 spectratyping and single-cell analysis can be combined to identify and track autoaggressive T cell clones in blood and target tissue. This approach should be applicable to other inflammatory and autoimmune disorders.

Genetic and environmental risk factors for idiopathic inflammatory myopathies

Although the studies discussed are beginning to reveal a number of genetic and possible environmental risk factors for myositis, further investigations are needed to fully understand and classify these syndromes. The difficulties in this process include small numbers of subjects with varying disease phenotypes available for study, polygenic risk factors for which it remains unclear which are primary and which are secondary or linked genes, and the lack of validated environmental exposure assessment tools. New technologies and international collaborative approaches, however, may overcome some of these difficulties and allow us to identify genetic and environmental risk factors, as well as the critical gene-environment interactions in the IIM and its subgroups. Nonetheless, our understanding of these diseases is still in the early stages. Although we have learned a great deal about these disorders through detailed investigations over the last several decades, we have even further to go to understand the environmental triggers and genetic susceptibilities for the myositis syndromes.

Rimmed vacuoles with beta-amyloid and ubiquitinated filamentous deposits in the muscles of patients with long-standing denervation (postpoliomyelitis muscular atrophy): similarities with inclusion body myositis

In the chronically denervated muscles of patients with prior paralytic poliomyelitis, there are secondary myopathic features, including endomysial inflammation and rare vacuolated fibers. To assess the frequency and characteristics of the vacuoles and their similarities with those seen in inclusion body myositis (IBM), we examined 58 muscle biopsy specimens from patients with prior paralytic poliomyelitis for (1) the presence of rimmed vacuoles; (2) acid-phosphatase reactivity; (3) Congo-red-positive amyloid deposits; (4) electron microscopy, searching for tubulofilaments; and (5) immunoelectron microscopy, using antibodies against beta-amyloid and ubiquitin. We found vacuolated muscle fibers in 18 of 58 (31%) biopsies, with a mean frequency of 2.06 +/- 0.42 fibers per specimen. The vacuoles contained acid phosphatase-positive material in 6 of the 18 (33.30%) specimens and stained positive for Congo red in five (27.80%). By immunoelectron microscopy, the vacuoles contained 5.17 +/- 0.13 nm fibrils and 14.9 +/- 0.31 nm filaments that immunoreacted with antibodies to beta-amyloid and ubiquitin in a pattern identical to the one seen in IBM. We conclude that vacuolated muscle fibers containing filamentous inclusions positive for amyloid and ubiquitin are not unique to IBM and the other vacuolar myopathies but can also occur in a chronic neurogenic condition, such as postpoliomyelitis. The chronicity of the underlying disease, rather than the cause, may lead to vacuolar formation, amyloid deposition, and accumulation of ubiquitinated filaments.

T-cell heterogeneity in muscle lesions of inclusion body myositis

In the muscle lesions of inclusion body myositis (IBM), two populations of T cells can morphologically be distinguished, T cells that invade muscle fibers and T cells that remain in interstitial areas. Using combined immunohistochemistry and RT-PCR, we analysed the TCR expressed by these distinct T cell populations. In three of eight IBM muscle specimens, the autoinvasive T cells were stained with one of the available mAbs: anti-Vbeta5.3 in patient 1, anti-Vbeta5.2 in patient 2, and anti-Vbeta3 in patient 3. The corresponding TCR Vbeta mRNAs were amplified by RT-PCR and the PCR products were cloned and sequenced. In all three specimens, the TCRs expressed by the autoinvasive T cells were clonally restricted. Furthermore, in patient 1 two different mAbs labelled two distinct populations of T cells: an autoaggressive population of CD8 + Vbeta5.3 + cells that invaded muscle fibers and a noninvasive interstitial population of CD8 - Vbeta5.1 + cells. TCR sequence analysis revealed that the noninvasive Vbeta5.1 + T cells were clonally diverse, whereas the autoinvasive Vbeta5.3 + T cells were clonally restricted.

Theiler's murine encephalomyelitis virus-induced cardiac and skeletal muscle disease

The DA strain of Theiler's murine encephalomyelitis virus, a member of the cardiovirus genus of picornaviruses, induces a restricted and persistent infection associated with a demyelinating process following intracerebral inoculation of mice; both virus infection and the immune response are believed to contribute to the late white matter disease. We now report that intraperitoneal inoculation with DA produces an acute myositis that progresses to a chronic inflammatory muscle disease in CD-1 mice as well as several inbred mouse strains. Some mouse strains also develop central nervous system white matter disease and a focal myocarditis. Infectious virus in skeletal muscle falls to undetectable levels 3 weeks postinoculation (p.i.), although viral genome persists for at least 12 weeks p.i., the longest period of observation. Severe combined immunodeficient animals have evidence of muscle pathology as long as 5 weeks p.i., suggesting that DA virus is capable of inducing chronic muscle disease in the absence of an immune response. The presence in immunocompetent mice, however, of prominent muscle inflammation in the absence of infectious virus suggests that the immune system also contributes to the pathology. T lymphocytes are the predominant cell type infiltrating the skeletal muscle during the chronic disease. This murine model may further our understanding of virus-induced chronic myositis and help to clarify the pathogenesis of human inflammatory myopathies.

Genetic determinants of susceptibility to coxsackievirus B1-induced chronic inflammatory myopathy: effects of host background and major histocompatibility complex genes

Infection of outbred CD-1 mice with the Tucson strain of coxsackievirus B1 (CVB1T) leads to the development of chronic hind limb weakness and associated inflammatory muscle disease. Host factors that influence susceptibility have not been studied in this mouse model of chronic inflammatory myopathy (IM). Therefore, the pathogenesis was examined by using different inbred strains of mice. Initially, seven strains of mice with either the H-2d or H-2b major histocompatibility complex (MHC) haplotype were evaluated. All strains showed similar levels of acute mortality caused by viral infection, but chronic weakness or inflammation did not develop in two strains with the B6 background, regardless of their MHC haplotype. In susceptible mice, weakness was more likely to develop in the H-2d strains than in mice with the H-2b haplotype. Based on these results, H-2 congenic strains of the susceptible B10 background (C57BL/10 and B10.D2) and the resistant B6 background (C57BL/6 and B6.C-H2d) were examined in greater detail. During acute infection, the kinetics and degree of viral replication in hind limb muscle were similar among B6 and B10 strains. By 4 weeks after infection, more intense chronic muscle inflammation and pathology were observed in susceptible B10 mice of the H-2d haplotype than in those of the H-2b haplotype. Resistant B6 mice did not show signs of inflammation or calcification, but they did exhibit some myopathic features, including centralized nuclei and variations in myofiber size and shape. These changes were less common in resistant B6 mice than in B10 strains but were significant when compared with changes in uninfected controls. Viral RNA persistence and elevated titers of antiviral IgG were more prevalent in but not restricted to susceptible strains. These studies demonstrate that host background genes confer resistance to chronic IM but also that MHC genes influence disease severity. They also reveal that susceptibility to acute CVB1T infection is under different genetic control than that which mediates development of chronic post-viral IM.

Search for persistent infection with poliovirus or other enteroviruses in amyotrophic lateral sclerosis-motor neurone disease

A longstanding hypothesis proposes that amyotrophic lateral sclerosis-motor neurone disease (ALS-MND) is a late consequence of subclinical poliovirus (PV) infection. In this study, RNA extracts of CNS tissue from 28 patients with ALS-MND and 7 controls were assayed by nested polymerase chain reaction (PCR) using primers to the 5'-untranslated region (UTR) of the enterovirus (EV) genome which is highly conserved between EVs including PV, echovirus and coxsackie viruses. The integrity of RNA extracted from either archival paraffin-embedded or frozen CNS tissue was assessed by detection of constitutive Ableson tyrosine kinase (ABL) mRNA by PCR. Of 63 tissue samples assayed, 81% (51/63) were ABL-positive corresponding to 78% (22/28) of the ALS-MND cases and all controls. None of the 27 ALS-MND cases (i.e. 21 ABL+ and 6 ABL-) in which paraffin-embedded tissue was used nor any of the age and sex matched controls were positive for specific PV/EV RNA. Moreover, CNS tissue from 14 different locations obtained from one patient < 2 hrs after death and immediately frozen, showed no evidence of PV/EV at any site by PCR. Disease duration, degree of tissue autolysis and duration of tissue storage were all excluded as factors which may predispose to negative results. The sensitivity of the PV PCR was determined to be 40-400 copies (12.5 - 125 ag) of synthetic EV RNA transcripts in 1 microgram of cellular RNA and the assay was shown to detect all types of PV and and other EVs tested. Thus it seems unlikely that a persistent PV or related EV infection is implicated in ALS-MND unless there has been alteration in the 5'-UTR of the virus genome.

Pathogenetic mechanisms of post-polio syndrome: morphological, electrophysiological, virological, and immunological correlations

To understand the mechanism of post-poliomyelitis muscular atrophy (PPMA) and the post-polio syndrome (PPS) in general, we performed the following studies: (1) histopathology in spinal cord sections from patients who died 9 days to 44 years after acute paralytic poliomyelitis; (2) enzyme histochemistry, immunocytochemistry (for lymphocyte subsets, MHC antigens and N-CAM) and polymerase chain reaction (PCR) for poliovirus RNA in the muscle biopsies from symptomatic or asymptomatic muscles of post-polio patients; (3) determination of lymphocyte subsets and circulating IgG or IgM antibodies against GM1 and poliovirus; (4) virological studies in the spinal fluid for oligoclonal bands and search for poliovirus genome with PCR; (5) electrophysiological studies including single fiber EMG, fiber density and macro-EMG; and (6) [31P] exercise MRS spectroscopy on previously affected muscles to search for a metabolic correlate of fatigue. These studies concluded that in PPS a continuing dysfunction is present in the spinal cord motor neurons, resulting in ongoing muscle denervation and reinnervation first evident at the axonal branch points. Symptoms are related to attrition of the oversprouting motor neurons which after a period of time cannot support all their axonal sprouts, resulting in failure of re-reinnervation. In some patients with PPS there is also an ongoing immune activation and presence of defective viral particles in the spinal fluid. However, their role in the pathogenesis of PPS is presently unknown.

Immunopathogenesis of inflammatory myopathies

Immune-mediated mechanisms appear to play a primary role in the pathogenesis of polymyositis (PM) and dermatomyositis (DM). The serum of patients with active DM has high levels of circulating complement fragments C3b, C4b, and C5b-9 membranolytic attack complex (MAC) and demonstrates a very high C3 uptake in an vitro assay system. The MAC and the immune complex-specific C3bNEO fragment are deposited on the endomysial capillaries early in the disease and lead sequentially to loss of capillaries, muscle ischemia, muscle fiber necrosis, and perifascicular atrophy. In contrast, in PM the muscle fiber injury is initiated by sensitized CD8+ cytotoxic T cells that recognize heretofore unknown and probably endogenous muscle antigens in the context of major histocompatibility complex (MHC) class I expression. A restricted (oligoclonal) pattern of T-cell receptor with prominence of Va1, Vb6, and Vb15 genes is noted within the endomysial infiltrates suggesting that the T-cell response is antigen driven. In both PM and DM, intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 are upregulated in the endomysial endothelial cells and function as ligands for the leukocyte integrins leukocyte function-associated antigen (LFA)-1 and very late activating antigen (VLA)-4, allowing activated lymphocytes to adhere to the endothelial cells and migrate to the muscle fibers. Among viruses, only the retroviruses human immunodeficiency virus (HIV) and human T-cell lymphotropic virus (HTLV)-1 have been convincingly shown to trigger PM, which is mediated by nonviral-specific, cytotoxic CD8+ cells. The treatment of inflammatory myopathies remains empirical. Many patients respond to steroids to some degree and for some period of time. Azathioprine, methotrexate, cyclosporine, cyclophosphamide, and plasmapheresis can be of mild to moderate benefit. High-dose intravenous immunoglobulin (IVIg) is a promising therapeutic modality for some patients resistant to therapies. In a controlled study, IVIg was effective in DM not only in improving the clinical symptoms but also in reversing the underlying immunopathology. The role of IVIg in PM and IBM is under study in control trials.

Detection of enteroviruses and rhinoviruses in clinical specimens by PCR and liquid-phase hybridization

A sensitive method based on PCR followed by liquid-phase hybridization for detection of enterovirus and rhinovirus RNAs in clinical specimens and cell culture supernatants is described. RNA was extracted from stool samples, throat swabs, nasopharyngeal aspirates, cerebrospinal fluid, urine, and plasma with a commercial phenol-guanidinium-chloroform reagent and purified on a polysulfone membrane, on which the reverse transcriptase reaction was also done. Two sets of oligonucleotide primers from the 5' noncoding region of picornaviruses were selected for DNA amplification of 153-bp (enterovirus) and 120-bp (rhinovirus) regions. Double-stranded amplicons were digested into single strands with T7 gene 6 exonuclease and quantitated by an assay using a europium-labeled probe, streptavidin- and biotinylated probe-coated microtitration wells, and time-resolved fluorometry. The sensitivity of the assay was about one template molecule when purified coxsackievirus A9 RNA was used. All enterovirus prototype strains, except echoviruses 22 and 23, and clinical isolates grown in cell culture or suckling mice were strongly positive by the enterovirus PCR-hybridization, as were selected prototype strains and untyped isolates of rhinoviruses by the rhinovirus PCR-hybridization. In a series of 100 clinical specimens tested, the results for 92 agreed with virus culture results. The detection method described will be useful in etiopathogenic studies on enteroviruses and rhinoviruses.

Polymyositis in patients infected with human T-cell leukemia virus type I: the role of the virus in the cause of the disease

To investigate the mechanism of polymyositis in human T-cell leukemia virus type I (HTLV-I) infection, we studied 6 HTLV-I-positive patients, 3 with polymyositis and 3 with adult T-cell leukemia but without clinical signs of muscle disease, by (a) quantitative single or double immunocytochemistry on serial 4-microns-thick muscle biopsy sections using antibodies to lymphocyte subsets, major histocompatibility complex (MHC) antigens, and HTLV-I proteins; (b) polymerase chain reaction using HTLV-I primers in the RNA and DNA extracted from 50 micrograms of muscle tissue or from serial 5-microns-thick fresh-frozen tissue sections; and (c) cocultures of the patients' HTLV-I-positive peripheral blood lymphocytes with their homologous muscles searching for replication of HTLV-I within the myotubes. In the muscle of patients with HTLV-I-associated myopathy, the predominant endomysial cells surrounding healthy muscle fibers were CD8+ cells followed by CD4+ cells and macrophages. MHC-I antigens were ubiquitous in the muscles of all 6 patients, even in those without endomysial inflammation. HTLV-I sequences were amplified from the whole muscle biopsy specimens but the cells harboring viral antigens were rare endomysial macrophages and not muscle fibers. Although HTLV-I sequences were amplified from all the patients' peripheral blood lymphocytes, these cells did not exert myotoxicity or resulted in viral replication in cocultures with their homologous myotubes.(ABSTRACT TRUNCATED AT 250 WORDS)

Search for persistent enterovirus infection of muscle in inflammatory myopathies

To investigate the hypothesis that the inflammatory muscle diseases (IMD) polymyositis (PM) and dermatomyositis (DM) may be due to a chronic, persistent enterovirus (EV) infection we sought to determine the prevalence of these viruses in muscle tissue using both nested polymerase chain reaction (PCR) and dot-blot hybridization assays. Thirty-six frozen muscle biopsies from 32 adult cases of IMD and 42 biopsies from 36 control subjects with other neuromuscular disorders were studied. Primers for PCR were chosen to conserved regions of the 5'-untranslated region of the EV genome. Constitutive Ableson tyrosine kinase (ABL) mRNA was detected by PCR to confirm the integrity of muscle RNA extracts. The sensitivity of the EV PCR was determined to be 40-400 copies (12.5-125 ag) of synthetic EV RNA transcript against a background of 1 microgram of cellular RNA. The specificity was assessed using a range of enteroviral and unrelated viral isolates extracted from cell cultures. Of the 78 samples tested, ABL mRNA was successfully detected in all but four samples. The time the biopsies spent in ultracold storage (1-73 months) did not appear to influence the integrity of extracted RNA. When assayed for EV RNA by nested PCR, none of 29 IMD cases (i.e., 28 PM and 1 DM) nor sequential biopsies from 3 PM patients were found to be positive. All 42 control biopsies were also negative for EV RNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Absence of Coxsackie viruses in idiopathic inflammatory muscle disease by in situ hybridization

The role of coxsackie virus infection in the pathogenesis of idiopathic inflammatory muscle disease (IIMD) has been investigated by many workers with conflicting results. This study uses in situ hybridization, with digoxigenin-labelled oligonucleotide probes complementary to the coxsackie B virus genome, to investigate the presence of virus RNA in muscle biopsies from 26 patients with IIMD. In the five cases of inclusion body myositis studied, there was focal probe-binding to nuclei and cytoplasm, and in nine cases probe-binding to mast cells was seen. In both of these instances probe-binding was non-specific and not due to hybridization. None of the cases showed the presence of coxsackie virus RNA within muscle and it is concluded that lytic infection of myocytes by coxsackie virus does not occur in IIMD.

Polymyositis and dermatomyositis: no persistence of enterovirus or encephalomyocarditis virus RNA in muscle

OBJECTIVES

A persistent infection of enteroviruses and cardioviruses has been implicated in polymyositis and dermatomyositis, but conventional hybridisation studies of the presence of enterovirus RNA and encephalomyocarditis (EMC) virus RNA in affected muscle have yielded conflicting results. To investigate further the possibility of viral persistence, the presence of viral RNA in muscle from patients with adult onset polymyositis and dermatomyositis was investigated using a polymerase chain reaction (PCR) technique.

METHODS

Muscle tissue was obtained from 10 patients with polymyositis and five patients with dermatomyositis, all with adult onset active disease. A PCR was performed using primers with high specificity for enterovirus and EMC virus RNA, followed by Southern blot hybridisation with an oligonucleotide probe directed against the internal portion of the amplified product. A PCR directed against the Abelson tyrosine kinase mRNA served as an internal control for the presence and quality of RNA.

RESULTS

A specific amplification for enterovirus or for EMC virus could not be seen in any of the muscle biopsy samples, despite a sensitivity of about 30 plaque forming units for enterovirus and of 100 plaque forming units for EMC virus. Southern blot hybridisation confirmed these results in that positive controls hybridised with the oligonucleotide probe, but no signal was obtained with the muscle specimens.

CONCLUSION

A sensitive and specific PCR technique showed no evidence of the presence of enterovirus or EMC virus RNA in muscle samples from patients with polymyositis or dermatomyositis. These data do not support the proposal that viral RNA persistence plays a part in these idiopathic inflammatory myopathies.

Analysis of T cell receptor repertoire of muscle-infiltrating T lymphocytes in polymyositis. Restricted V alpha/beta rearrangements may indicate antigen-driven selection

Polymyositis is an inflammatory myopathy characterized by mononuclear cell infiltration of muscle tissue. Myocytotoxic T lymphocytes have been recognized in the infiltrates, but the muscle antigen, target of the immune attack, has not been identified. Molecular characterization of the variable regions of T cell receptors (TCRs) on the infiltrating lymphocytes can be expected to provide insights into the pathogenic process. The V alpha/beta TCR repertoire was investigated by RNA-PCR in muscle biopsies from 15 polymyositis patients and 16 controls (6 Duchenne muscular dystrophy and 10 with no inflammatory or dystrophic myopathy). A variety of rearranged variable TCR genes was found in polymyositis, V alpha 1, V alpha 5, V beta 1, and V beta 15 being the most common (present in 60-100% of patients). In Duchenne muscular dystrophy patients TCR V alpha or beta rearrangements were found although no restriction was observed; no rearrangements were found in muscles from the other controls. Sequence analysis revealed the presence of the J beta 2.1 region in 90% of the V beta 15 clones studied, no random N additions in the diversity region, and a common motif within the CDR3 region. These results suggest that selection of muscle-infiltrating T lymphocytes is antigen driven in polymyositis.