Antiphospholipid antibodies in pediatric and adult patients with rheumatic disease are associated with parvovirus B19 infection

Pediatric antiphospholipid syndrome

APS is rare in the pediatric age, but it represents an interesting phenomenon because most of the known "second hit" risk factors such as atherosclerosis, smoking, hypertension, contraceptive hormonal treatment, and pregnancy are not present in childhood. This could also be the reason for the prevalence of some clinical manifestations rather than others in PAPS. On the other hand, the increased frequency of infectious processes in the childhood age is likely responsible for the relatively high prevalence of non-pathogenic and transient aPL. Such points raise the problem of a different diagnosis or monitoring approach in pediatric APS. Of particular interest is the special entity of neonatal APS, which represents an in vivo model of acquired autoimmune disease, in which transplacentally acquired aPL cause thrombosis in the newborn. International registries for pediatric and neonatal APS are currently in place; epidemiologic, clinical, and laboratory re-search will help to shed light on all the still obscure aspects of this fascinating but rare disorder in the very young. Finally, treatment is less aggressive overall in pediatric APS, given the reluctance to anticoagulate children over the long term. Studies on the outcome of pediatric APS and the relative risks of prolonged anticoagulation in children are necessary to determine the type and duration of anticoagulation therapy.

Conformational changes in the VP1-unique region of native human parvovirus B19 lead to exposure of internal sequences that play a role in virus neutralization and infectivity

The unique region of the capsid protein VP1 (VP1u) of human parvovirus B19 (B19) elicits a dominant immune response and has a phospholipase A(2) (PLA(2)) activity, which is necessary for the infection. In contrast to the rest of the parvoviruses, the VP1u of B19 is thought to occupy an external position in the virion, making this region a promising candidate for vaccine development. By using a monoclonal antibody against the most-N-terminal portion of VP1u, we revealed that this region rich in neutralizing epitopes is not accessible in native capsids. However, exposure of capsids to increasing temperatures or low pH led to its progressive accessibility without particle disassembly. Although unable to bind free virus or to block virus attachment to the cell, the anti-VP1u antibody was neutralizing, suggesting that the exposure of the epitope and the subsequent virus neutralization occur only after receptor attachment. The measurement of the VP1u-associated PLA(2) activity of B19 capsids revealed that this region is also internal but becomes exposed in heat- and in low-pH-treated particles. In sharp contrast to native virions, the VP1u of baculovirus-derived B19 capsids was readily accessible in the absence of any treatment. These results indicate that stretches of VP1u of native B19 capsids harboring neutralizing epitopes and essential functional motifs are not external to the capsid. However, a conformational change renders these regions accessible and triggers the PLA(2) potential of the virus. The results also emphasize major differences in the VP1u conformation between natural and recombinant particles.

Increased expression and secretion of interleukin-6 in human parvovirus B19 non-structural protein (NS1) transfected COS-7 epithelial cells

Human parvovirus B19 (B19) has been associated with a variety of autoimmune diseases, including rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). We have demonstrated previously that B19 non-structural protein (NS1) induced apoptosis through the mitochondria cell death pathway in COS-7 epithelial cells and that B19 NS1 may play a role in the pathogenesis of autoimmune diseases. In order to examine the expression profiles of cytokines and chemokines in B19 NS1 transfected COS-7 cells, we constructed the NS1 gene in the pEGFP-C1 vector named enhanced green fluorescence protein gene (EGFP)-NS1. COS-7 cells were transfected with EGFP or EGFP-NS1 plasmid. The expression profiles of cytokines and chemokines, including interleukin (IL)-1beta, IL-5, IL-6, IL-8, IL-10, tumour necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta, granulocyte-macrophage colony-stimulating factor (GM-CSF), growth-related oncogene alpha (GROalpha), interferon gamma-inducible protein (IP)-10, stromal cell derived factor (SDF)-1, macrophage inflammatory protein (MIP)-1beta, monocyte chemoattractant protein (MCP)-1, regulated upon activation normal T cell expressed and secreted (RANTES), Fractalkine, CX3CR1, CCR2, CCR5 and CCR11 were examined in COS-7 cells, EGFP and EGFP-NS1 transfected cells using enzyme-linked immunosorbent assay (ELISA) or reverse transcription-polymerase chain reaction (RT-PCR). Increased expression and levels of IL-6 were found in EGFP-NS1 transfected cells using RT-PCR and ELISA. There were no significant increases in the expression of IL-1beta, IL-8, IP-10, SDF-1, RANTES, Fractalkine, CX3CR-1, CCR2, CCR5, CCR11, TNF-alpha, GM-CSF and TGF-beta using RT-PCR. There were no significantly increased levels of IL-5, IL-10, TNF-alpha, TGF-beta, GROalpha, MIP-1beta and MCP-1 found by ELISA in this study. Our results show that increased expression and secretion of IL-6 in B19 NS1 transfected epithelial cells may play a role in the pathogenesis of autoimmune diseases.

Parvovirus B19: the causative agent of dilated cardiomyopathy or a harmless passenger of the human myocard?

Parvovirus B19 infections may cause a widespread benign and self-limiting disease in children and adults known as erythema infectiosum (fifth disease). Several further manifestations are associated with B19 infections, such as arthralgias, arthritis, leucopenia and thrombocytopenia, anaemia and vasculitis and spontaneous abortion and hydrops fetalis in pregnant women. Persistent infections with continuous virus production may occur in immunocompetent as well as in immunosuppressed individuals. Parvovirus B19 infections have been frequently implicated as a cause or trigger of various forms of autoimmune diseases affecting joints, connective tissue and large and small vessels. Autoimmune neutropenia, thrombocytopenia and haemolytic anaemia are known as sequelae of B19 infections. The molecular basis of the autoimmune phenomena is unclear. Many patients with these long-lasting symptoms are not capable of eliminating the virus or controlling its propagation. Furthermore, latent viral genomes have been detected in cells of various organs and tissues by PCR. At present, it is not clear if these cells produce viral proteins and/or infectious B19 particles, if the virus genome can be reactivated to productive replication and if the presence of viral DNA indicates a causative role of parvovirus B19 with distinct diseases.

Pathogenesis of aleutian mink disease parvovirus and similarities to b19 infection

Aleutian mink disease parvovirus (ADV) is an unusual member of the autonomous parvoviruses in both its replication and pathogenesis. Infection of newborn mink kits results in an acute disease typified by virus replication in type II pneumocytes in the lung. This replication is permissive and cytopathic, characterized by the production of high levels of viral replicative intermediates and infectious progeny. However, infection of adult Aleutian mink leads to a chronic form of the disease termed Aleutian disease (AD). In this case, virus replication occurs predominantly in lymph node macrophages and is restricted, with viral DNA replication, RNA transcription, protein expression and production of infectious progeny occurring at low levels. B19 is the only autonomous parvovirus known to infect humans. The primary site of virus replication in both children and adults is in erythrocyte precursors in the blood and bone marrow, although viral genomes have been detected in various other tissues. B19 infection often causes a self-limiting disease although persistent infection of B19 can occur in both immuno-compromised and -competent people. Perhaps the most striking similarity between infection with ADV or with B19 is the important role the humoral immune response to infection has in pathogenesis. It can be both protective and pathogenic. Due to of the central role of antibody in the disease caused by either virus, understanding the specific roles of antibody production in protection, antibody-mediated enhancement of infection, the establishment of persistent infection and immune-mediated pathology will provide insight into the pathogenesis of these infections. A second similarity between the two viruses is the ability to establish persistent infection. Persistence of ADV is associated with restricted replication. Although many cellular factors may contribute to restricted virus replication, the interactions between the major non-structural protein, NS1, and the cells are likely to be critical. Parallels exist between the expression and post-translational modification of ADV and B19 NS1 proteins that may contribute to restriction of virus replication. Thus, a study of the regulation of NS1 expression and its interactions with cell signalling pathways may lead to increased understanding of the restricted replication of these two viruses, and perhaps of persistent infection.

Antiphospholipid antibodies in pediatric patients with prolonged activated partial thromboplastin time during infection

OBJECTIVE

To investigate the close association between different antiphospholipid antibodies (aPL) caused by infection and their appearance together with a prolonged activated partial thromboplastin time (aPTT).

METHODS

Sera from 122 children were evaluated in this study. Thirty-seven children with mild to medium prolonged aPTT (>37.2s) and elevated C-reactive protein (CRP) levels during various forms of infections (group 2), 18 children without infections (group 3) but with mild to medium prolonged aPTT and 13 children with infections (group 4) and with elevated CRP-level as well as a control group (group 1) of 54 patients without any infection and normal aPTT and negative CRP levels were investigated with commercially available ELISA tests (AESKU.Diagnostics, Wendelsheim, Germany) for the presence of antibodies directed against cardiolipin (CL), phosphatidylserine (PS) and beta2-glycoprotein I (beta 2GPI). The cutoff for positive results was defined with the healthy, aged matched control group (group 1) using the mean OD values plus 2 standard deviations. The lupus anticoagulant (dilute Russell's Viper Venom time, dRVVT) and coagulation Factor XII were determined with routine tests (Dade Behring).

RESULTS

Detection of at least one antibody to phospholipids was possible in 89.2% of group 2. It could be shown that IgM anti-beta 2GPI antibodies were found in 27 (59.5%) of group 2, but only in 1 (5.6%) of group 3 (p=0.024) and only in 4 (7.4%) of the controls (p=0.014). The presence of IgG-anti-beta 2GPI antibodies showed no significant difference in the different groups. Furthermore, children of groups 2, 3 and 4 had statistically significant higher levels of antibodies against PS IgG and PS IgM than controls. Also, antibodies to CL of the IgG-type were more frequently detected in children of group 2 than in controls (p=0.038). Detection of CL-IgM antibodies did not reach a significant level in the comparison of the different groups.

CONCLUSION

During commonly acquired infections elevation of aPL of nearly all types seems to be a common process. Mild prolongation of aPTT might reflect this presence of aPL in the course of the infectious disease. Our data suggest that there exists no differences in specificity in comparison to the "pathogenic" aPL but the presence over time might be the trigger for the autoimmune activity to begin.

Early arthritis and infection

PURPOSE OF REVIEW

To summarize the recent literature on the association of infection with early arthritis, and to discuss the possible role of such infections with respect to the development of chronic rheumatic complications.

RECENT FINDINGS

Viral infections are frequently associated with arthritis. Alphaviruses belong to mosquito-borne viruses, one form of which (Sindbis virus) can in Scandinavia and Karelia cause acute arthritis with typical rash. The role of this infection leading to chronic erosive arthritis needs further prospective studies. Patients infected with HIV can have various forms of arthritis. The role of HIV virus as an arthritogenic agent is still debated. On the basis of population studies, Campylobacter infections seem to be increasing as causative infections in reactive arthritis. There is no role for prolonged antibiotic therapy to shorten the duration of acute reactive arthritis, but the possibility that such a treatment might reduce the development of chronic sequelae needs to be examined in a larger study. The role of preceding infection initiating the process of rheumatoid arthritis is still an option, the association being observed in about 20% of patients studied in the early phase of arthritis.

SUMMARY

Viral and microbial infections play a role in acute arthritis. The role of these infections in the development of chronic arthritis needs further prospective controlled studies.

Pathogenesis of Parvovirus B19 Infection: Host Gene Variability, and Possible Means and Effects of Virus Persistence

Since conducting follow-up studies of patients with acute symptomatic parvovirus B19 infection which showed that a significant proportion of patients develop prolonged arthritis and chronic fatigue syndrome (CFS), we have become interested in the mechanisms of this phenomenon. We showed that these cases have high levels of pro-inflammatory cytokines in their circulation and that this correlates with the symptoms. However, the underlying mechanisms were not apparent, and we have used various approaches to begin studying this phenomenon. DNA polymorphisms were looked for and several were shown to be more common in these subjects compared with controls; these occur within genes of both the immune response [human leucocyte antigen (HLA)-DRB1, HLA-B, transforming growth factor (TGF)-beta1] and those involved in several other cellular functions (predominantly the cytoskeleton and cell adhesion). Interestingly, one particular single-nucleotide polymorphism (SNP) which is associated with symptomatic B19 infection occurs in the Ku80 gene which has recently been shown to be a B19 co-receptor. B19 persistence is probably the key to this phenomenon, and some new data are presented on short regions of sequence homology (17-26 bp) between human, mouse and rat parvoviruses and their respective hosts which occur in many host genes. This homology may provide a foothold for virus persistence and may also play a role in the genesis of disease through gene disruption. Finally, we used microarrays and TaqMan real-time polymerase chain reaction in 108 normal persons to study human gene expression in persons who are B19-seropositive versus B19-seronegative (age- and sex-matched) to examine the hypothesis that gene regulation may be altered in subjects harbouring the B19 virus DNA. Six genes were found to be differentially expressed with roles in the cytoskeleton (SKIP, MACF1, SPAG7, FLOT1), integrin signalling (FLOT1, RASSF5), HLA class III (c6orf48), and tumour suppression (RASSF5). These results have implications not only for B19 but also for other persistent viruses as well and confirmation is required. In conclusion, these disparate findings contribute to our understanding of the pathogenesis of B19 disease. We are using these studies as a starting point to study the phenomenon of chronic immune activation following B19 infection.

Lupus-like presentation of parvovirus B19 infection

OBJECTIVES

To describe 2 cases of parvovirus B19 (B19) infection mimicking systemic lupus erythematosus (SLE) and to identify all cases of SLE imitated by and/or associated with B19 in the medical literature.

METHODS

A computer-assisted (PubMed) search of the medical literature from 1975 to 2003 was performed using the following key words: parvovirus, B19, SLE, lupus, antibodies, auto-immunity.

RESULTS

Thirty-eight patients were identified: 35 women, 3 men; mean age = 28.8 years. Clinical manifestations were as follows: fever (24 patients); articular involvement (36 patients); cutaneous lesions (28 patients); lymphadenopathy (9 patients); hepato- and/or splenomegaly (6 patients); serositis (6 patients); renal involvement (4 patients); cerebral impairment (10 patients). Cytopenia was observed in 23 cases. Antinuclear antibodies were detected in 34 patients, anti-double-stranded DNA antibodies in 20 patients, anti-Sm antibodies in 4 patients, antinuclear ribonucleoprotein antibodies in 5 patients, anti-Ro-SSA antibodies in 4 patients, anti-La-SSB antibodies in 4 patients, and anticardiolipin and/or anti-beta2-glycoprotein I antibodies in 8 patients. Hypocomplementemia was found in 15 of 26 patients. In 19 cases, the B19 infection had a self-limiting course. In 6 cases, B19 infection occurred in a context of previously established SLE, simulating SLE exacerbation. In 6 observations, symptoms persisted several months after the viral infection. In 7 cases, the exact relationship between SLE and B19 could not be determined.

CONCLUSIONS

B19 infection may present a clinical and serological tableau making it difficult to distinguish between a viral infection and the first episode of SLE. Although B19 may modulate the clinical and biological features of rheumatic disease, studies in large series do not support a causative role for B19 in the pathogenesis of SLE.

Antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a systemic autoimmune disorder characterized by a combination of arterial or venous thrombosis and recurrent fetal loss, accompanied by elevated titers of antiphospholipid antibodies (aPL). APS has been recognized as the leading cause of vascular thrombosis in children. The diagnostic and therapeutic approach to APS in childhood may be different from that for adults and because of the rarity of aPL-related thrombosis in children, the natural history and optimal management of APS can be defined only through large, multicenter, controlled studies.

Antibodies and clinical features of the antiphospholipid syndrome as criteria for systemic lupus erythematosus

The antiphospholipid syndrome (APS) can occur as a primary diagnosis or as a prominent feature of other diseases, predominantly systemic lupus erythematosus (SLE). The 1982 revised criteria for SLE were published prior to many of the studies which have illuminated current understanding of the antiphospholipid syndrome and several current clinical criteria for SLE, when arising from thrombotic damage to different organ systems, could be attributed to APS, leading to some confusion about where the diagnoses of these two disorders should begin and end. Additionally, APS is a significant generalized risk factor for irreversible organ damage and overall mortality in SLE patients and genetic linkages to HLA in APS hold up whether the disorder is primary or linked to SLE. It is increasingly recognized that APS itself is a complex, heterogenous disorder, involving a spectrum of autoantibodies to phospholipid-binding proteins, many of which have known coagulation-regulating functions. Although the combination of more than one antiphospholipid-related antibody might indicate a more severe phenotype, it is not suggested here that additive criteria for the diagnosis of SLE be accumulated with more than one of these pathologically related autoantibodies. Patients with multiple criteria for APS should be considered to have severe APS but it would be recommended to restrict APS-attributed criteria for SLE to a maximal of two: one immunologic and one clinical. Thus people meeting the Sapporo criteria for APS could gain only a maximum of two criteria for SLE, regardless of how many autoantibodies were detected or how severe the clinical syndrome might be. This would allow manifestations of fullblown APS an appropriate impact towards the diagnosis of SLE without leading to a premature diagnosis of SLE for people who might better be considered to have moderate to severe primary APS.

Manifestations systémiques des infections à Parvovirus B19

PURPOSE

Parvovirus B19 (B19) causes many clinical disorders, of which the most common are erythema infectiosum, aplastic crisis complicating chronic hemolytic anemia, and hydrops fetalis. In young adults, the skin eruption caused by B19 is accompanied by polyarthritis and polyarthralgia in 60% of the cases. Rheumatoid factors and other antibodies including antinuclear antibodies, anti-ADN, and antiphospholipids can be produced in the wake of B19 infection.

CURRENT KNOWLEDGE AND KEY POINTS

These features may simulate systemic diseases as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) (lupus-like eruption over the cheeks, cytopenia, etc.) or vasculitis (purpura, renal involvement). In addition, there have been a few reports of SLE, vasculitis and other connective tissue diseases developing shortly after a B19 infection associated with virus clearance suggesting that B19 can act as a trigger of systemic disease. However, studies in large series indicate that in fact B19 is probably an extremely rare cause of RA, SLE or vasculitis.

FUTURE PROSPECTS AND PROJECTS

In fundamental studies B19 interacts with inflammatory cells by regulation of cytokines. More recently, two studies suggest that viral infection due to B19 may affect the course of SLE, leading to specific biological subsets. These preliminary findings require confirmation to elucidate the significance of the presence of B19 in systemic disease.

Advances in the biology, diagnosis and host-pathogen interactions of parvovirus B19

Increased recognition of parvovirus B19 (B19), an erythrovirus, as a significant human pathogen that causes fetal loss and severe disease in immunocompromised patients has resulted in intensive efforts to understand the pathogenesis of B19-related disease, to improve diagnostic strategy that is deployed to detect B19 infection and blood-product contamination and, finally, to elucidate the nature of the cellular immune response that is elicited by the virus in diverse patient cohorts. It is becoming clear that at least three related erythrovirus strains (B19, A6/K71 and V9) are circulating in the general population and that viral entry into target cells is mediated by an expanding range of cellular receptors, including P antigen and beta-integrins. Persistent infection by B19 is emerging as a contributory factor in autoimmune disease, a hypothesis that is constrained by the detection of B19 in the skin of apparently healthy individuals. B19 infection during pregnancy may account for thousands of incidences of fetal loss per annum in Europe, North America and beyond, yet there is currently only minimal screening of pregnant women to assess serological status, and thereby risk of infection, upon becoming pregnant. Whilst major advances in diagnosis of B19 infection have taken place, including standardization of serological and DNA-based detection methodologies, blood donations that are targeted at high-risk groups are only beginning to be screened for B19 IgG and DNA as a means of minimizing exposure of at-risk patients to the virus. It is now firmly established that a Th1-mediated cellular immune response is mounted in immunocompetent individuals, a finding that should contribute to the development of an effective vaccine to prevent B19 infection in selected high-risk groups, including sickle-cell anaemics.

Frontal lobe seizures and uveitis associated with acute human parvovirus B19 infection

We report a 5-year-old girl who developed repeated episodes of behavioral alterations shortly after human parvovirus B19 infection and uveitis. Video-electroencephalographic study demonstrated that these brief episodes were frontal lobe seizures. Seizures responded promptly to antiepilepsy medications. Further diagnostic testing did not reveal any rheumatologic disorders. Human parvovirus B19 infections in children are more commonly associated with febrile seizures and meningoencephalitis. Our case demonstrates that, rarely, it may be associated with the development of partial epilepsy.

Intravenous immunoglobulin treatment of four patients with juvenile polyarticular arthritis associated with persistent parvovirus B19 infection and antiphospholipid antibodies

Children with rheumatic oligoarthritis and polyarthritis frequently establish persistent parvovirus B19 infections that may be associated with the production of antiphospholipid antibodies (anti-PL IgG). In this study we analysed the influence of high-dose intravenous immunoglobulin (IVIG) therapy on virus load, on the level of anti-PL IgG and its potential capacity to improve the patients' clinical status. Four juvenile patients with long-lasting polyarticular rheumatic diseases and persistent parvovirus B19 infection, associated in three cases with the presence of antibodies against β₂-glycoprotein I (anti-β₂GPI IgG), were treated with two cycles of IVIG on five successive days (0.4 g/kg per day). Clinical parameters including scores of disease activity, virus load and anti-PL IgG levels were determined before, during and after treatment. Two patients showed a complete remission that has lasted 15 months. During that period they showed neither clinical nor laboratory signs of inflammation. Viral DNA was not detectable in serum, and a decrease in anti-β₂GPI IgG was observed. As assessed by the Childhood Health Assessment Questionnaire and the Health-related Quality of Life Questionnaire for Children, both patients were no longer restricted in their activities of daily living and no impact on the health-related quality of life was observed. In one patient the therapy failed: there was no improvement of symptoms and no decrease in virus load or inflammatory parameters. In the fourth patient, clinical and laboratory parameters did not improve despite a decrease in both viral load and anti-PL IgG. Our results show that the use of IVIG to treat parvovirus B19-triggered polyarticular rheumatic disease of childhood might offer an opportunity to improve this disabling condition.