Parvovirus B19 nonstructural (NS1) protein as a transactivator of interleukin-6 synthesis: common pathway in inflammatory sequelae of human parvovirus infections?

Cutavirus Infection in Large-Plaque Parapsoriasis, a Premalignant Condition of Mycosis Fungoides

BACKGROUND

Cutavirus (CuV) is associated with mycosis fungoides; however, the CuV status in parapsoriasis en plaques (PP), a premalignant inflammatory condition of mycosis fungoides, has not been fully delineated.

METHODS

Fifty-five Japanese patients with chronic inflammatory skin diseases, including 13 patients with PP, were studied.

RESULTS

CuV DNA was detected significantly more frequently in biopsies of the lesional skin from patients with PP (38%; 4 of 13) than in those from patients with other inflammatory skin diseases (2%; 1 of 42; P = .009). All CuV-positive PP cases were of the large-plaque parapsoriasis (LPP) subtype. The viral loads ranged from 83 450 to 2 164 170 copies/103 cells. We recovered near-full-length CuV sequences from the CuV-positive LPP biopsies, all of which were of the Japanese/Asian genotype. The CuV genome appeared to be present within lymphoid cells infiltrating the epidermis and dermis. CuV NS1 and VP1 gene transcripts were also detected in the affected tissues.

CONCLUSIONS

The detection of high levels of CuV DNA with the expression of viral mRNA suggests a potential role for CuV in the pathogenesis of LPP, making it necessary to study further the impact of CuV, especially regarding the viral genotype, on the outcomes of patients with CuV-positive LPP.

Involvement of cutavirus in a subset of patients with cutaneous T-cell lymphoma with an unfavorable outcome

BACKGROUND

European studies suggest an association between cutavirus (CuV) and cutaneous T-cell lymphoma (CTCL); however, the worldwide prevalence of CuV in patients with CTCL and its prognostic impact remain unknown.

METHODS

We investigated the prevalence and viral loads of CuV DNA using biopsy specimens from the lesional skins of 141 Japanese patients with cutaneous malignancies, including 55 patients with various types of CTCL.

RESULTS

CuV DNA was detected significantly more frequently in biopsies from patients with mycosis fungoides (MF) (38% [13/34]; the most common subtype of CTCL) than in those from patients with other cutaneous malignancies (6% [6/107]; P<0.001). The viral-load range in patients with CuV DNA-positive MF was 23-3922 copies/10³ cells and 8-65 copies/μg of DNA. A phylogenetic analysis using the partial sequences of the CuV viral capsid protein 1 (VP1)/VP2 genes revealed that the CuV sequences identified here were clustered in a Japanese-specific clade distinct from that comprising CuV sequences from European patients with MF. Kaplan-Meier curves and a log-rank test showed that CuV positivity was associated with a shorter disease-specific survival in patients with MF (P = 0.031), whereas no significant difference in overall survival was observed (P = 0.275). No significant correlation was observed between CuV DNA load and survival in patients with CuV-positive MF.

CONCLUSIONS

Our results suggest that CuV is associated with MF in a subset of Japanese patients. Large-scale prospective studies are warranted to clarify the role of CuV status, especially regarding the viral genotype, on adverse outcomes in patients with CuV-positive MF.

First report on severe septic shock associated with human Parvovirus B19 infection after cardiac surgery

Background

Human Parvovirus B19 (PB19) is a single-stranded DNA virus. Septic shock from viremia is rare with PB19; however, this infection can progress to life-threatening conditions. We report the first case of severe septic shock associated with a PB19 infection after cardiac surgery.

Case Presentation

A 50-year-old Chinese woman received elective double metal valve replacement, including the aortic valve and the mitral valve, under cardiopulmonary bypass (CPB) and suffered severe septic shock on postoperative day (PD) 30. Through the detection of PB19-specific nucleic acids in blister fluid and serum samples via metagenomic next-generation sequencing (mNGS), positive serum PB19 IgM and no other proven infection, acute PB19 infection was confirmed. After five days of combined treatment, no further fever or abdominal discomfort was noted, and the patient’s circulation gradually became stable without vasoactive medications.

Conclusion

PB19 may be an unrecognized cause of septic shock, rash, fever of unknown origin or multiple systemic signs and symptoms, especially in immunosuppressed and immunocompetent critically ill patients. Investigations for viral aetiology are needed.

[Parvovirus B19 infections in adults]

Acute Parvovirus B19 (PVB19) infection is responsible for erythema infectiosum in children and non-specific polyarthralgias in immunocompetent adults associated with skin lesions and rarer manifestations (hepatic, neurological, cardiac or nephrological). In immunocompromised patients, cytopenias are more frequent and in some cases, viremia persists and is responsible for PVB19 chronic infection. PVB19 is responsible for pure red cell aplasia during chronic hemolytic diseases. Acute PVB19 infection is a differential diagnosis of some autoimmune diseases and has been suspected to be a trigger for some autoimmune diseases because of its ability to promote the emergence of autoimmune markers. Mechanisms of molecular mimicry, induction of apoptosis and activation of enzymes have been demonstrated, explaining in part the production of autoantibodies during infection. However, the demonstration of a causal relationship in the triggering of autoimmune disease remains to be done. This review provides a synthesis of the PVB19 infection clinical data in adults with a particular focus on these links with autoimmunity.

Parvovirus B19 affects thrombopoietin and IL-11 gene expression in human bone marrow mesenchymal stem cells

Aim: Human bone marrow mesenchymal stem cells (hBMSCs) may be infected by parvovirus B19 (B19V). hBMSCs support bone marrow hematopoiesis by producing stromal cells, secretion of cytokines and growth factors, etc. Because of the lifetime persistent infection of the virus in healthy individual’s bone marrow, this study aims to evaluate B19V effects on hBMSCs gene expression of some crucial hematopoietic cytokines. Materials & methods: hBMSCs were transfected with pHI0 plasmid containing the B19V genome. The quantitative mRNA expression of target genes was evaluated 24 h after transfection. Results: Our findings demonstrated a significant increase in expression levels of IL-11 and TPO (p < 0.05). Conclusion: We concluded that alteration in the gene expressions in B19V-infected hBMSCs might have significant effects on the bone marrow microenvironment as well as hematopoiesis.

Viral Infections and Systemic Lupus Erythematosus: New Players in an Old Story

A causal link between viral infections and autoimmunity has been studied for a long time and the role of some viruses in the induction or exacerbation of systemic lupus erythematosus (SLE) in genetically predisposed patients has been proved. The strength of the association between different viral agents and SLE is variable. Epstein-Barr virus (EBV), parvovirus B19 (B19V), and human endogenous retroviruses (HERVs) are involved in SLE pathogenesis, whereas other viruses such as Cytomegalovirus (CMV) probably play a less prominent role. However, the mechanisms of viral-host interactions and the impact of viruses on disease course have yet to be elucidated. In addition to classical mechanisms of viral-triggered autoimmunity, such as molecular mimicry and epitope spreading, there has been a growing appreciation of the role of direct activation of innate response by viral nucleic acids and epigenetic modulation of interferon-related immune response. The latter is especially important for HERVs, which may represent the molecular link between environmental triggers and critical immune genes. Virus-specific proteins modulating interaction with the host immune system have been characterized especially for Epstein-Barr virus and explain immune evasion, persistent infection and self-reactive B-cell "immortalization". Knowledge has also been expanding on key viral proteins of B19-V and CMV and their possible association with specific phenotypes such as antiphospholipid syndrome. This progress may pave the way to new therapeutic perspectives, including the use of known or new antiviral drugs, postviral immune response modulation and innate immunity inhibition. We herein describe the state-of-the-art knowledge on the role of viral infections in SLE, with a focus on their mechanisms of action and potential therapeutic targets.

The role of Th17 cells in viral infections

The present review provides an overview of recent advances regarding the function of Th17 cells and their produced cytokines in the progression of viral diseases. Viral infections alone do not lead to virus-induced malignancies, as both genetic and host safety factors are also involved in the occurrence of malignancies. Acquired immune responses, through the differentiation of Th17 cells, form the novel components of the Th17 cell pathway when reacting with viral infections all the way from the beginning to its final stages. As a result, instead of inducing the right immune responses, these events lead to the suppression of the immune system. In fact, the responses from Th17 cells during persistent viral infections causes chronic inflammation through the production of IL-17 and other cytokines which provide a favorable environment for tumor growth and its development. Additionally, during the past decade, these cells have been understood to be involved in tumor progression and metastasis. However, further research is required to understand Th17 cells' immune mechanisms in the vast variety of viral diseases. This review aims to determine the roles and effects of the immune system, especially Th17 cells, in the progression of viral diseases; which can be highly beneficial for the diagnosis and treatment of these infections.

Parvovirus B19-induced hemophagocytic lymphohistiocytosis: Case report and review of the literature

HLH is a catastrophic and likely underdiagnosed pathology with multiple triggers including infection. PVB19 can cause persistent marrow infection leading to HLH despite negative acute serologic markers making timely diagnosis difficult. Increased awareness of PVB19-HLH is warranted given its potentially lethal nature and the careful interpretation required with serologic markers.

Parvovirus B19 Infection in Human Bone Marrow Mesenchymal Stem Cells Affects Gene Expression of IL-6 and TNF-α and also Affects Hematopoietic Stem Cells Differentiation

Parvovirus B19 (B19V) has been known to induce transient erythroid aplasia, cytopenia and aplastic anemia. This virus persists in bone marrow mesenchymal stem cells (HBMSCs) of some immunocompetent individuals several years after primary infection. In B19V infected erythroid progenitor cells, the virus induces transactivation of Interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) gene expression. Due the critical role of HBMSCs in bone marrow niche and inhibitory effect of inflammatory cytokines on hematopoiesis, the aim of this study was to investigate the effect of B19V on IL-6 and TNF-α gene expression intransfected cells. In addition we assessed the clonogenicity potential of cord blood CD34+ stem cells that were co-cultured with infected cells. After 24 h of transfection, quantitative mRNA expression of IL-6 and TNF-α was evaluated and human cord blood CD34+ HSC were cultured with the transfected cells. At the end of 7 days of culture, HSCs colony forming units (CFUs) assay was performed. Our findings demonstrated statistically significant (18.1 and 21.9 fold) increase of TNF-α and IL-6 gene expression respectively and decrease in burst forming unit-erythrocyte (BFU-E) and colony forming unit-erythrocyte (CFU-E) enumeration(p < 0.05). We concluded that, inducing inflammatory cytokines gene expression in B19V-infected HBMSCs might influence on bone marrow microenvironment and hematopoiesis.

Down-regulation of inwardly rectifying Kir2.1 K+ channels by human parvovirus B19 capsid protein VP1

Parvovirus B19 (B19V) has previously been shown to cause endothelial dysfunction. B19V capsid protein VP1 harbors a lysophosphatidylcholine producing phospholipase A2 (PLA2). Lysophosphatidylcholine inhibits Na(+)/K(+) ATPase, which in turn may impact on the activity of inwardly rectifying K(+) channels. The present study explored whether VP1 modifies the activity of Kir2.1 K(+) channels. cRNA encoding Kir2.1 was injected into Xenopus oocytes without or with cRNA encoding VP1 isolated from a patient suffering from fatal B19V-induced inflammatory cardiomyopathy or the VP1 mutant (H153A)VP1 lacking a functional PLA2 activity. K(+) channel activity was determined by dual electrode voltage clamp. In addition, Na(+)/K(+)-ATPase activity was estimated from K(+)-induced pump current (I(pump)) and ouabain-inhibited current (I(ouabain)). Injection of cRNA encoding Kir2.1 into Xenopus oocytes was followed by appearance of inwardly rectifying K(+) channel activity (I(K)), which was significantly decreased by additional injection of cRNA encoding VP1, but not by additional injection of cRNA encoding (H153A)VP1. The effect of VP1 on I K was mimicked by lysophosphatidylcholine (1 μg/ml) and by inhibition of Na(+)/K(+)-ATPase with 0.1 mM ouabain. In the presence of lysophosphatidylcholine, I K was not further decreased by additional treatment with ouabain. The B19V capsid protein VP1 thus inhibits Kir2.1 channels, an effect at least partially due to PLA2-dependent formation of lysophosphatidylcholine with subsequent inhibition of Na(+)/K(+)-ATPase activity.

Th17-related cytokines in systemic lupus erythematosus patients with dilated cardiomyopathies: a possible linkage to parvovirus B19 infection

Dilated cardiomyopathies (DCM) are a major cause of mortality in patients with systemic lupus erythematosus (SLE). Immune responses induced by human parvovirus B19 (B19) are considered an important pathogenic mechanism in myocarditis or DCM. However, little is known about Th17-related cytokines in SLE patients with DCM about the linkage with B19 infection. IgM and IgG against B19 viral protein, and serum levels of Th17-related cytokines were determined using ELISA in eight SLE patients with DCM and six patients with valvular heart disease (VHD). Humoral responses of anti-B19-VP1u and anti-B19-NS1 antibody were assessed using Western blot and B19 DNA was detected by nested Polymerase Chain Reaction (PCR). Levels of interleukin (IL)-17, IL-6, IL-1β, and tumor necrosis factor (TNF)-α were significantly higher in SLE patients with DCM (mean ± SEM, 390.99±125.48 pg/ml, 370.24±114.09 pg/ml, 36.01±16.90 pg/ml, and 183.84±82.94 pg/ml, respectively) compared to healthy controls (51.32±3.04 pg/ml, p<0.001; 36.88±6.64 pg/ml, p<0.001; 5.39±0.62 pg/ml, p<0.005; and 82.13±2.42 pg/ml, p<0.005, respectively). Levels of IL-17 and IL-6 were higher in SLE patients with DCM versus those with VHD (both p<0.01). Five (62.5%) of DCM patients had detectable anti-B19-NS1 IgG and four (50.0%) of them had anti-B19-VP1u IgG, whereas only one (16.7%) of VHD patients had detectable anti-B19-NS1 IgG and anti-B19-VP1u IgG. Serum levels of IL-17, IL-6 and IL-1β were markedly higher in SLE patients with anti-B19-VP1u IgG and anti-B19-NS1 IgG compared to those without anti-B19-VP1u IgG or anti-B19-NS1 IgG, respectively. These suggest a potential association of B19 with DCM and Th17-related cytokines implicated in the pathogenesis of DCM in SLE patients.

Parvovirus B19 at the culprit coronary stenosis predicts outcome after stenting

BACKGROUND

Parvovirus (PV) B19 DNA is detected in endothelial cells and may cause endothelial dysfunction, which is involved in in-stent restenosis. We aimed at performing an exploratory analysis that evaluated if PVB19 DNA at the culprit coronary stenosis would be associated with an increased rate of major adverse cardiac events (MACE) after coronary stenting.

MATERIALS AND METHODS

Consecutive patients undergoing stent implantation for stable or unstable coronary artery disease were enroled. Serology for PVB19 infection and presence of DNA for PVB19 on balloons used for predilatation were assessed in all patients. MACE rate, as a composite of cardiac death, myocardial infarction (MI) or clinically driven target lesion revascularization (TLR) was obtained at 24 month follow-up. Adjusted hazard ratio (HR) with 95% confidence interval (CI) was calculated for variables associated with MACE.

RESULTS

One hundred and nine patients [age 66 ± 10, male sex 89 (82%)] were enroled. At 24-month follow-up, 18 patients experienced a MACE. Two patients (2%) experienced MI, while 16 patients (15%) experienced clinically driven TLR. At multiple Cox regression analysis, the presence of PVB19 DNA on the balloon and the use of bare-metal stents were independent predictors of MACE [HR 3·30, 95% CI (1·12-10·08), P = 0·03 and HR 4·19, 95% CI (1·60-10·94), P = 0·003].

CONCLUSIONS

PVB19 DNA detected on the balloon used for dilatation of coronary stenosis before stent implantation is associated with MACE rate at follow-up, mainly due to clinically driven TLR. The results of this exploratory analysis should be confirmed in a larger population.

Exacerbating effects of human parvovirus B19 NS1 on liver fibrosis in NZB/W F1 mice

Systemic lupus erythematosus (SLE) is an autoimmune disorder with unknown etiology that impacts various organs including liver. Recently, human parvovirus B19 (B19) is recognized to exacerbate SLE. However, the effects of B19 on liver in SLE are still unclear. Herein we aimed to investigate the effects of B19 on liver in NZB/W F1 mice by injecting subcutaneously with PBS, recombinant B19 NS1, VP1u or VP2, respectively. Our experimental results revealed that B19 NS1 protein significantly enhanced the TGF-β/Smad fibrotic signaling by increasing the expressions of TGF-β, Smad2/3, phosphorylated Smad2/3, Smad4 and Sp1. The consequent fibrosis-related proteins, PAI-1 and α-SMA, were also significantly induced in livers of NZB/W F1 mice receiving B19 NS1 protein. Accordingly, markedly increased collagen deposition was also observed in livers of NZB/W F1 mice receiving B19 NS1 protein. However, no significant difference was observed in livers of NZB/W F1 mice receiving B19 VP1u or VP2 as compared to the controls. These findings indicate that B19 NS1 plays a crucial role in exacerbating liver fibrosis in NZB/W F1 mice through enhancing the TGF-â/Smad fibrotic signaling.

Human parvovirus B19 induced apoptotic bodies contain altered self-antigens that are phagocytosed by antigen presenting cells

Human parvovirus B19 (B19V) from the erythrovirus genus is known to be a pathogenic virus in humans. Prevalence of B19V infection has been reported worldwide in all seasons, with a high incidence in the spring. B19V is responsible for erythema infectiosum (fifth disease) commonly seen in children. Its other clinical presentations include arthralgia, arthritis, transient aplastic crisis, chronic anemia, congenital anemia, and hydrops fetalis. In addition, B19V infection has been reported to trigger autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. However, the mechanisms of B19V participation in autoimmunity are not fully understood. B19V induced chronic disease and persistent infection suggests B19V can serve as a model for viral host interactions and the role of viruses in the pathogenesis of autoimmune diseases. Here we investigate the involvement of B19V in the breakdown of immune tolerance. Previously, we demonstrated that the non-structural protein 1 (NS 1) of B19V induces apoptosis in non-permissive cells lines and that this protein can cleave host DNA as well as form NS1-DNA adducts. Here we provide evidence that through programmed cell death, apoptotic bodies (ApoBods) are generated by B19V NS1 expression in a non-permissive cell line. Characterization of purified ApoBods identified potential self-antigens within them. In particular, signature self-antigens such as Smith, ApoH, DNA, histone H4 and phosphatidylserine associated with autoimmunity were present in these ApoBods. In addition, when purified ApoBods were introduced to differentiated macrophages, recognition, engulfment and uptake occurred. This suggests that B19V can produce a source of self-antigens for immune cell processing. The results support our hypothesis that B19V NS1-DNA adducts, and nucleosomal and lysosomal antigens present in ApoBods created in non-permissive cell lines, are a source of self-antigens.

Extreme thrombocytosis in a young cat

A 7-month-old unvaccinated domestic shorthair cat was presented with a history of inappetence and hypersalivation. Clinical examination revealed fever, gingivitis and oral ulceration. An initial blood sample revealed a severe leukopenia and neutropenia and a feline panleukopenia virus (FPV) titre of 1:640; a second titre 10 days later was 1:2,560. A feline calicivirus (FCV) titre was 1:320 and the initial clinical signs and laboratory findings were attributed to a coinfection with FPV and FCV. The cat was treated with interferon omega. A blood sample taken 10 days later revealed a severe thrombocytosis of 3,448 × 10⁹/L (reference range 200–500 × 10⁹/L) confirmed by blood smear examination. The platelet count on day 35 was 4,990 × 10⁹/L. No bone marrow examination was carried out. Two differential diagnoses for an extreme thrombocytosis are a reactive thrombocytosis or essential thrombocythemia (ET). ET is a hemic neoplasia that causes a severe and persistent thrombocytosis, and is a diagnosis of exclusion. Reactive thrombocytosis is generally mild to moderate and of shorter duration than described here, but an excessive response could have been caused by infection. The influence of additional factors such as an initial thrombocytopenia, age and interferon treatment are not clear but can be speculated on. Although the exact pathophysiology in this case remains unclear, such high, persistent thrombocyte numbers have not been reported in cats in the absence of a neoplastic process.

Diagnosis, management and possibilities to prevent parvovirus B19 infection in pregnancy

Human parvovirus B19 (B19V) infection in pregnancy can cause severe fetal anemia and nonimmune hydrops fetalis, which may be associated with spontaneous abortion and fetal death. Approximately 30–40% of women of child-bearing age are not immune to B19V infection. The risk to fetal life is particularly high if maternal infection occurs during the first 20 weeks of gestation. In this article we intend to give an overview on the molecular biology, epidemiology and management of B19V infection during pregnancy. These data will be combined with an assessment of the clinical situation of the infected fetus and the possibilities for avoiding and/or preventing B19V infection in pregnant women. Currently B19V infection is the causative agent of one of the most frequently occurring infectious complications in pregnancy that endangers fetal life, and so the necessity to develop a preventive vaccine is discussed.

Infection and immunity for human parvovirus B19 in patients with febrile exanthema

The contribution of parvovirus B19 (B19V) as a causative agent of febrile exanthema (FE) in Cordoba, Argentina, was analysed by detection of viral DNA, and specific IgM and IgG. Serum from 141 patients with FE who were negative for measles and rubella, collected during 2005-2009, plus serum from 31 healthy individuals, were assayed. B19V was the aetiological agent in 14·9% of all FE cases, and in 39·1% in an epidemic year (2007). B19V DNA was detected in 47·6% of IgM-positive FE patients, 30·2% of IgM-negative/IgG-positive FE patients, and 9·7% of healthy controls, indicating B19V long-term infection in ~10% of immunocompetent individuals. Persistent B19V DNA was significantly more frequent in children than adults and in males than females. All patients with acute B19V infection had rash and fever, 85·7% had adenopathy, and only 14·3% had arthropathy. This is the first follow-up study of markers of infection and immunity for B19V infection in Argentina.

Advances in human B19 erythrovirus biology

Since its discovery, human parvovirus B19 (B19V), now termed erythrovirus, has been associated with many clinical situations (neurological and myocardium infections, persistent B19V DNAemia) in addition to the prototype clinical manifestations, i.e., erythema infectiosum and erythroblastopenia crisis. In 2002, the use of new molecular tools led to the characterization of three different genotypes of human B19 erythrovirus. Although the genomic organization is conserved, the geographic distribution of the different genotypes varies worldwide, and the nucleotidic divergences can impact the molecular diagnosis of B19 virus infection. The cell cycle of the virus remains partially unresolved; however, recent studies have shed light on the mechanism of cell entry and the interactions of B19V proteins with apoptosis pathways.

Human parvovirus B19 nonstructural protein NS1 enhanced the expression of cleavage of 70 kDa U1-snRNP autoantigen

Background

Human parvovirus B19 (B19) is known to induce apoptosis that has been associated with a variety of autoimmune disorders. Although we have previously reported that B19 non-structural protein (NS1) induces mitochondrial-dependent apoptosis in COS-7 cells, the precise mechanism of B19-NS1 in developing autoimmunity is still obscure.

Methods

To further examine the effect of B19-NS1 in presence of autoantigens, COS-7 cells were transfected with pEGFP, pEGFP-B19-NS1 and pEGFP-NS1K334E, a mutant form of B19-NS1, and detected the expressions of autoantigens by various autoantibodies against Sm, U1 small nuclear ribonucleoprotein (U1-snRNP), SSA/Ro, SSB/La, Scl-70, Jo-1, Ku, and centromere protein (CENP) A/B by using Immunoblotting.

Results

Significantly increased apoptosis was detected in COS-7 cells transfected with pEGFP-B19-NS1 compared to those transfected with pEGFP. Meanwhile, the apoptotic 70 kDa U1-snRNP protein in COS-7 cells transfected with pEGFP-B19-NS1 is cleaved by caspase-3 and converted into a specific 40 kDa product, which were recognized by anti-U1-snRNP autoantibody. In contrast, significantly decreased apoptosis and cleaved 40 kDa product were observed in COS-7 cells transfected with pEGFP-NS1K334E compared to those transfected with pEGFP-B19-NS1.

Conclusions

These findings suggested crucial association of B19-NS1 in development of autoimmunity by inducing apoptosis and specific cleavage of 70 kDa U1-snRNP.

Human parvovirus B19 NS1 protein modulates inflammatory signaling by activation of STAT3/PIAS3 in human endothelial cells

The pathogenic mechanism by which parvovirus B19 may induce inflammatory cardiomyopathy (iCMP) is complex but is known to involve inflammatory processes, possibly including activation of JAK/STAT signaling. The nonstructural B19 protein NS1 acts as a transactivator triggering signaling cascades that eventually lead to activation of interleukin 6 (IL-6). We examined the impact of NS1 on modulation of STAT signaling in human endothelial cells (HMEC-1). The NS1 sequences were identified from B19 DNA isolated from the myocardia of patients with fatal iCMP. B19 infection as well as NS1 overexpression in HMEC-1 cells produced a significant upregulation in the phosphorylation of both tyrosine(705) and serine(727) STAT3 (P < 0.05). The increased STAT3 phosphorylation was accompanied by dimerization, nuclear translocation, and DNA binding of pSTAT3. In contrast, NS1 expression did not result in increased STAT1 activation. Notably, the expression levels of the negative regulators of STAT activation, SOCS1 and SOCS3, were not altered by NS1. However, the level of PIAS3 was upregulated in NS1-expressing HMEC-1 cells. Analysis of the transcriptional activation of target genes revealed that NS1-induced STAT3 signaling was associated with upregulation of genes involved in immune response (e.g., the IFNAR1 and IL-2 genes) and downregulation of genes associated with viral defense (e.g., the OAS1 and TYK2 genes). Our results demonstrate that B19 NS1 modulates the STAT/PIAS pathway. The NS1-induced upregulation of STAT3/PIAS3 in the absence of STAT1 phosphorylation and the lack of SOCS1/SOCS3 activation may contribute to the mechanisms by which B19 evades the immune response and establishes persistent infection in human endothelial cells. Thus, NS1 may play a critical role in the mechanism of viral pathogenesis in B19-associated iCMP.

Human bocavirus--a novel parvovirus to infect humans

For almost three decades parvovirus B19 has been described as the only member of the Parvoviridae to infect and cause illness in humans. This statement was correct until 2005 when a group of Swedish scientists identified a previously uncharacterized virus in pools of human nasopharyngeal aspirates obtained from individuals suffering from diseases of the respiratory tract. Comprehensive sequence and phylogenetic analysis allowed the identification of the new virus as a member of the Parvoviridae. Based on its close relation to the minute virus of canines and the bovine parvovirus, it was named human bocavirus (HBoV). Since the identification of HBoV, viral genomes have been frequently detected worldwide in nasopharyngeal swabs, serum and fecal samples almost exclusively derived from young children with various symptoms of the respiratory or the gastrointestinal tract. The detection of HBoV genomes tends to be associated with elevated rates of coinfections with further respiratory viruses, e.g. respiratory syncytial virus or metapneumovirus. First studies on virus-specific immune responses have described the presence of ubiquitous humoral and cellular immune reactions against HBoV in adults and adolescents, indicating a high seroprevalence of this new virus in humans.

Detection of parvovirus B19 in synovial fluids of patients with osteoarthritis

We aimed to determine the possible role of parvovirus B19 (PVB19) in the etiology of osteoarthritis. PVB19 DNA, anti-VP1 IgM and IgG, and interleukin IL-6 levels were also assayed in synovial fluids of 42 patients with osteoarthritis and 10 controls. PVB19 DNA was detected in 28 of 42 (66.66%) in patients and in 3 of 10 (30%) in controls. IgG and IgM response were detected in 21 of 42 (50.00%) and in 2 of 42 (4.76%) patients, respectively. IL-6 were positive in 15 of 42 (36%) patients and in 3 of 10 (30%) controls. All IgG (+) samples had PVB19 DNA (100%, P < 0.001). Eleven of 15 IL-6 (+) samples had PVB19 DNA (+) (73.33%, P < 0.05). Moreover, all IL-6 (+) samples (n = 5) in stage IV had PVB19 DNA (+) (100%, P < 0.001). We have detected a significant association between the stages of osteoarthritis and PVB19 DNA (P < 0.05). These findings support the presence of PVB19 acting as a transactivator of IL-6 expression as reported earlier. Our results also suggest that the higher stages of osteoarthritis might be related to the increased inflammation and cell damage on joint cartilage due to PVB19.

An association between parvovirus B19 and Kikuchi-Fujimoto disease

Although Kikuchi-Fujimoto disease (KFD) has a higher prevalence among Asian countries, it is a well-defined entity throughout the world. However, its etiology and pathogenesis remain undetermined. To study whether B19 infection is associated with idiopathic KFD (iKFD), we examined the presence of the viral genome and proteins in paraffin-embedded tissues of lymph nodes retrospectively from 33 iKFD patients and 16 age- and sex-matched control subjects by nested PCR (nPCR), in situ hybridization (ISH), and immunohistochemistry (IHC). B19 was detected in 87.1, 69.7, and 57.6% of iKFD specimens by nPCR, ISH, and IHC, respectively, whereas the virus was positive in only 56.3, 31.3, and 25.0% of control tissues by the respective methods (nPCR: p = 0.029; ISH: p = 0.011; IHC: p = 0.032). The IHC-ISH double-staining assay demonstrated that B19-infected cells were mainly lymphocytes and a small number of histiocytes. These results showed for the first time a high frequency of localized persistence of B19 in lymph nodes from iKFD patients, suggesting that B19 might play an important role in the pathogenesis of iKFD.

Parvovirus B19 detected in Rosai-Dorfman disease in nodal and extranodal manifestations

Sinus histiocytosis with massive lymphadenopathy (SHML), also designated as Rosai-Dorfman disease (RDD), is a rare benign reactive lymphoproliferative disorder. It is defined by a characteristic histopathology with sinus histiocytosis and haemophagocytosis known as emperipolesis. In histiocytes S100 is strongly expressed, whereas CD1a staining typically is negative. The disease mainly manifests at a single lymph node; however, multilocular and extranodal affection can occur. Causative infectious agents, and virus infections in particular, have repeatedly been suspected, although until now the origin of the disease has been unclear. Four cases of RDD (two nodal sites and two extranodal upper respiratory tract sites) were analysed for parvovirus B19 (B19) infection by immunohistochemistry to detect B19 capsid proteins VP1/VP2. In all the four cases, huge numbers of B19-positive cells were partly detected. The positive cells were identified either as lymphocytes or, in one extranodal case, also as respiratory epithelial cells. This is the first report of B19 infection in RDD tissue, indicating that B19 may be associated with the pathogenesis of SHML.

Unscrambling the role of human parvovirus B19 signaling in systemic autoimmunity

Despite enormous progress in understanding how the immune system works, the pathogenesis of autoimmune diseases still remains unclear. Growing evidence indicates that infectious agents can be potent initial triggers, subverting and exploiting host cell signaling pathways. This role is exemplified by the association of parvovirus B19 (B19) with human autoimmune disease. Infection with this common virus exhibits striking similarities with systemic autoimmune diseases, and can be associated with elevated serum autoantibody titers. The B19 virus produces proline-rich, 11-kDa proteins that have been implicated in modulation of host signaling cascades involved in virulence and pathogenesis. Additionally, B19 produces a non-structural protein (NS1) that functions as a transcription regulator by directly binding the p6 promoter and the Sp1/Sp3 transcription factors. The protein is also involved in DNA replication, cell cycle arrest and initiation of apoptotic damage, particularly in erythroid cells. When transfected to non-permissive cells, NS1 recruits the mitochondria cell death pathway. It is even more remarkable that NS1 functions as a trans-acting transcription activator for the IL6 promoter, up-regulating IL6 expression in host cells. Hence, B19 infection may play a pivotal role in triggering inflammatory disorders. By promoting apoptotic damage and trans-activating pro-inflammatory cytokine promoters, B19 may break the delicate balance between cell survival and apoptosis, and may contribute to immune deregulation. Understanding the mechanisms used by B19 to alter the cell signaling machinery may provide further insight into the mechanism by which autoimmune diseases develop.

Clinical aspects of parvovirus B19 infection

Parvovirus B19 is a significant human pathogen that causes a wide spectrum of clinical complications ranging from mild, self-limiting erythema infectiosum in immunocompetent children to lethal cytopenias in immunocompromised patients and intrauterine foetal death in primary infected pregnant women. The infection may also be persistent and can mimic or trigger autoimmune inflammatory disorders. Another important clinical aspect to consider is the risk of infection through B19-contaminated blood products. Recent advances in diagnosis and pathogenesis, new insights in the cellular immune response and newly discovered genotypes of human parvoviruses form a platform for the development of modern therapeutic and prophylactic alternatives.

Phospholipase A2 activity-dependent stimulation of Ca2+ entry by human parvovirus B19 capsid protein VP1

Recent reports demonstrated an association of human parvovirus B19 with inflammatory cardiomyopathy (iCMP), which is accompanied by endothelial dysfunction. As intracellular Ca(2+) activity is a key regulator of cell function and participates in mechanisms leading to endothelial dysfunction, the present experiments explored the effects of the B19 capsid proteins VP1 and VP2. A secreted phospholipase A2 (PLA2)-like activity has been located in the VP1 unique region of the B19 minor capsid protein. As PLA2 has recently been shown to activate the store-operated or capacitative Ca(2+) channel I(CRAC), we analyzed the impact of the viral PLA2 motif on Ca(2+) entry. We cloned the VP1 and VP2 genes isolated from a patient suffering from fatal B19 iCMP into eukaryotic expression vectors. We also generated a B19 replication-competent plasmid to demonstrate PLA2 activity under the control of the complete B19 genome. After the transfection of human endothelial cells (HMEC-1), cytosolic Ca(2+) activity was determined by utilizing Fura-2 fluorescence. VP1 and VP2 expression did not significantly modify basal cytosolic Ca(2+) activity or the decline of cytosolic Ca(2+) activity following the removal of extracellular Ca(2+). However, expression of VP1 and of the full-length B19 clone, but not of VP2, significantly accelerated the increase of cytosolic Ca(2+) activity following the readdition of extracellular Ca(2+) in the presence of thapsigargin, indicating an activation of I(CRAC.) The effect of VP1 was mimicked by the PLA2 product lysophosphatidylcholine and abolished by an inactivating mutation of the PLA2-encoding region of the VP1 gene. Our observations point to the activation of Ca(2+) entry by VP1 PLA2 activity, an effect likely participating in the pathophysiology of B19 infection.

Parvovirus B19: a new emerging pathogenic agent of inflammatory cardiomyopathy

The human parvovirus B19 (PVB19), an erythrovirus causing diverse clinical manifestations ranging from asymptomatic or mild to more severe outcomes such as hydrops fetalis, is the only currently known human pathogenic parvovirus. Recently, PVB19 has been identified as a causative agent of pediatric and adult inflammatory cardiac diseases. The first hints for a possible etiopathogenetic role of the PVB19 infection and the development of cardiac dysfunction were demonstrated by molecular biology methods such as in situ hybridization (ISH) and polymerase chain reaction (PCR). In this regard, PVB19-associated inflammatory cardiomyopathy is characterized by infection of endothelial cells of small intracardiac arterioles and venules, which may be associated with endothelial dysfunction, impairment of myocardial microcirculation, and penetration of inflammatory cells in the myocardium.

A high prevalence of parvovirus B19 DNA in patients with psoriasis

Psoriasis is a common inflammatory skin disease. Infectious models are considered to be of pathophysiological importance in psoriasis. The immunological profile of stable psoriasis plaques suggests that viral antigens may be important. Human parvovirus B19 (PVB19) is a single-stranded DNA virus that causes various clinical symptoms. Several case reports have suggested associations between PVB19 infection and various chronic autoimmune and dermatologic diseases. There has so far been no information regarding the role of PVB19 in psoriasis, except psoriatic arthritis. In this report, to investigate the role of PVB19 in psoriasis, we analyzed PVB19 DNA of peripheral blood from psoriatic patients (n = 47) in comparison with blood donors (n = 20). We also determined the presence of anti-PVB19 IgG and IgM antibodies by using enzyme-linked immunosorbent assay (ELISA). We found that the presence of PVB19 DNA in patients with psoriasis (38%) was significantly higher than in controls (0%, P < 0.01). Anti-PVB19 IgG antibodies were detected in 79% of the cases while only 6% had anti-PVB19 IgM antibodies. PVB19 DNA presence was associated with seropositivity for anti-PVB19 IgG (P < 0.05) but not with IgM antibodies, indicating subclinical activation of latent infection. No correlation was found between the presence of PVB19 DNA and a patient's age, sex, type of psoriasis, or psoriasis area and severity index. The data demonstrated a statistically significant association between psoriasis and PVB19. Therefore, we suggest that PVB19 infection may be of pathophysiological importance in psoriasis.

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.

Detection of human parvovirus B19 nonstrutural protein DNA by nested-polymerase chain reaction in gravida serum and pregnant tissues

A new nested-polymerase chain reaction (nested-PCR) assay was developed to detect human parvovirus B19 DNA corresponding to the nonstructural protein in clinical specimens in a routine diagnostic laboratory. The sensitivity of this highly specific assay was up to 0.005 fg of B19 DNA. Parvovirus B19 was identified in sera of 20 pregnant women with abnormal pregnant outcome. Among these 20 cases, intrauterine parvovirus infection did exist in 7 pregnant women because parvovirus B19 DNA was detected in the pregnant tissues of them such as placenta tissues, chorionic villi, amniotic fluid, fetal spleen, liver and abdominal fluids.

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.

Human parvovirus B19: a new emerging pathogen of inflammatory cardiomyopathy

The human parvovirus B19 (PVB19), an erythrovirus causing diverse clinical manifestations ranging from asymptomatic or mild to more severe outcomes such as hydrops fetalis, is the only known human pathogenic parvovirus so far. Although enteroviruses have long been considered the most common cause of inflammatory cardiomyopathy, PVB19 is emerging as a important candidate. Recent studies have indicated an association of PVB19 with paediatric and adult inflammatory cardiac disease. However, whether or not PVB19 has an impact on inflammatory cardiomyopathy in adult patients is still unclear. The first hints for a possible aetiopathogenetic role of the PVB19-infection and the development of cardiac dysfunction were demonstrated by molecular biology utilizing in situ hybridization (ISH) and polymerase chain reaction (PCR). According to available evidence, PVB19-associated inflammatory cardiomyopathy is characterized by infection of endothelial cells of small intracardiac arterioles and venules, which may be associated with endothelial dysfunction, impairment of myocardial microcirculation, and penetration of inflammatory cells into the myocardium.

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.

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.

Avian reovirus sigmaC protein induces apoptosis in cultured cells

The avian reovirus (ARV) infection is associated with various disease conditions in poultry. However, the pathogenesis mechanisms are poorly characterized. In the present study, we clearly demonstrated that the sigmaC of ARV S1133 strain induced apoptosis in both BHK-21 and Vero cells. Five kinds of assays for apoptosis were used in analyzing ARV-infected BHK-21 and Vero cells: (1) assay for DNA ladders, (2) ELISA detection of cytoplasmic histone-associated DNA fragments, (3) nuclear staining with acridine orange, (4) Western blot, Northern blot, and immunofluorescent assay (IFA), and (5) flow cytometric analysis. The sigmaC protein of ARV could elicit apoptosis occurring in a dose- and time-dependent manner. The current results further our understanding of the function of sigmaC in cultured cells and suggest that sigmaC is a viral-encoded apoptin and possesses apoptosis-inducing ability. Furthermore, deletion analysis of the ARV sigmaC protein suggests that the carboxyl-terminus of sigmaC is important in mediating sigmaC-induced apoptosis because its deletion abolished the induction of apoptosis.

Cytokine profiles in adult mink infected with Aleutian mink disease parvovirus

The aim of this study was to examine the levels of gamma interferon (IFN-gamma)-, interleukin 4 (IL-4)-, and IL-8-producing cells in peripheral blood mononuclear cells from mink infected with the Aleutian mink disease parvovirus (ADV). As expected, ADV-infected mink developed high plasma gamma globulin values (hypergammaglobulinemia) and enhanced quantities of CD8-positive (CD8(+)) cells in the blood during the infection. We quantified the percentages of IFN-gamma- and IL-4-positive lymphocytes and IL-8-positive monocytes up to week 38 after virus challenge. The results clearly indicated marked increases in the percentages of IFN-gamma- and IL-4-producing lymphocytes during ADV infection. The total number of IL-8-producing monocytes in the blood of ADV-infected mink stayed fairly constant during the infection. In order to characterize the phenotype of the cytokine-producing cells, we performed double-labeling fluorescence-activated cell sorter (FACS) experiments with CD8 surface labeling in one channel and cytokine intracellular staining in the other. We found that most IFN-gamma and IL-4 in ADV-infected mink was produced by CD8(+) cells, while in the uninfected mink, these cytokines were primarily produced by a cell type that was not CD8 (possibly CD4-positive cells). We also observed that IL-8 was almost exclusively produced by monocytes. All of the above findings led us to conclude that both Th1- and Th2-driven immune functions are found in mink plasmacytosis.

Parvovirus B19 infection and autoimmune disease

Human parvovirus B19 infections may cause a widespread benign and self-limiting disease in children and adults, known as erythema infectiosum or fifth disease. A variety of further manifestations are associated with the infection such as arthralgias, arthritis, leukopenia and thrombocytopenia, anemia and vasculitis, spontaneous abortion and hydrops fetalis in pregnant women. Both in children and adults 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. In addition, autoimmune neutropenia, thrombocytopenia and hemolytic anemia are known as sequelae of B19 infection. The molecular basis of the autoimmune phenomena and resultant pathogenesis is unclear. The involvement of molecular mimicry between cellular and viral proteins, the induction of enhanced cytokine production via the viral transactivator protein NS1 and the phospholipase A2-like activity of the capsid protein VP1 may contribute to the induction of autoimmune reactions. All the known data and the potential mechanisms involved in the pathogenesis will be discussed in this review.