Environmental Triggers for Vasculitis

Systemic vasculitides are autoimmune diseases characterized by vascular inflammation. Most types of vasculitis are thought to result from antigen exposure in genetically susceptible individuals, suggesting a likely role for environmental triggers in these conditions. Seasonal and geographic variations in incidence provide insight into the potential role of environmental exposures in these diseases. Many data support infectious triggers in some vasculitides, whereas other studies have identified noninfectious triggers, such as airborne pollutants, silica, smoking, and heavy metals. We review the known and suspected environmental triggers in giant cell arteritis, Takayasu arteritis, polyarteritis nodosa, Kawasaki disease, and antineutrophil cytoplasmic antibody-associated vasculitis.

New Insights into the Pathogenesis of Giant Cell Arteritis: Mechanisms Involved in Maintaining Vascular Inflammation

The giant cell arteritis (GCA) pathophysiology is complex and multifactorial, involving a predisposing genetic background, the role of immune aging and the activation of vascular dendritic cells by an unknown trigger. Once activated, dendritic cells recruit CD4 T cells and induce their activation, proliferation and polarization into Th1 and Th17, which produce interferon-gamma (IFN-γ) and interleukin-17 (IL-17), respectively. IFN-γ triggers the production of chemokines by vascular smooth muscle cells, which leads to the recruitment of additional CD4 and CD8 T cells and also monocytes that differentiate into macrophages. Recent data have shown that IL-17, IFN-γ and GM-CSF induce the differentiation of macrophage subpopulations, which play a role in the destruction of the arterial wall, in neoangiogenesis or intimal hyperplasia. Under the influence of different mediators, mainly endothelin-1 and PDGF, vascular smooth muscle cells migrate to the intima, proliferate and change their phenotype to become myofibroblasts that further proliferate and produce extracellular matrix proteins, increasing the vascular stenosis. In addition, several defects in the immune regulatory mechanisms probably contribute to chronic vascular inflammation in GCA: a defect in the PD-1/PD-L1 pathway, a quantitative and qualitative Treg deficiency, the implication of resident cells, the role of GM-CSF and IL-6, the implication of the NOTCH pathway and the role of mucosal‑associated invariant T cells and tissue‑resident memory T cells.

Novel aspects of regulatory T cell dysfunction as a therapeutic target in giant cell arteritis

OBJECTIVES

Giant cell arteritis (GCA) is the most common primary vasculitis, preferentially affecting the aorta and its large-calibre branches. An imbalance between proinflammatory CD4+ T helper cell subsets and regulatory T cells (Tregs) is thought to be involved in the pathogenesis of GCA and Treg dysfunction has been associated with active disease. Our work aims to explore the aetiology of Treg dysfunction and the way it is affected by remission-inducing immunomodulatory regimens.

METHODS

A total of 41 GCA patients were classified into active disease (n=14) and disease in remission (n=27). GCA patients' and healthy blood donors' (HD) Tregs were sorted and subjected to transcriptome and phenotypic analysis.

RESULTS

Transcriptome analysis revealed 27 genes, which were differentially regulated between GCA-derived and HD-derived Tregs. Among those, we identified transcription factors, glycolytic enzymes and IL-2 signalling mediators. We confirmed the downregulation of forkhead box P3 (FOXP3) and interferon regulatory factor 4 (IRF4) at protein level and identified the ineffective induction of glycoprotein A repetitions predominant (GARP) and CD25 as well as the reduced T cell receptor (TCR)-induced calcium influx as correlates of Treg dysfunction in GCA. Inhibition of glycolysis in HD-derived Tregs recapitulated most identified dysfunctions of GCA Tregs, suggesting the central pathogenic role of the downregulation of the glycolytic enzymes. Separate analysis of the subgroup of tocilizumab-treated patients identified the recovery of the TCR-induced calcium influx and the Treg suppressive function to associate with disease remission.

CONCLUSIONS

Our findings suggest that low glycolysis and calcium signalling account for Treg dysfunction and inflammation in GCA.

Association of Parvovirus B19 with Rheumatic Diseases

Human parvovirus B19 infections are well reported to be associated with different autoimmune disorders. They can either mimic or trigger autoimmune diseases, such as systemic lupus erythematous (SLE), rheumatoid arthritis (RA), and vasculitis. A lack of awareness about this infection can result in delays in diagnosis and poor care. In this review, the basic biology and clinical aspects of the parvovirus, human immune response, and the pathogenesis in the rheumatic diseases are discussed.

Increased Incidence of Giant Cell Arteritis After Introduction of a Live Varicella Zoster Virus Vaccine

BACKGROUND

Varicella zoster virus (VZV) has been associated with giant cell arteritis (GCA). The introduction of a live attenuated vaccine against this virus (ZVL) might have changed the incidence of GCA.

METHODS

The incidence of GCA was retrospectively measured using 2 matched cohorts seen in a regional health system located in the Midwestern United States: ZVL recipients from the years 2007 through 2015 following the introduction of the vaccine and nonrecipients from the years 2000 through 2015.

RESULTS

In the ZVL cohort, a significant increase of GCA was associated with clinical criteria alone for the diagnosis of GCA (hazard ratio [HR], 2.70; 95% CI, 1.48-4.45; P = .004). In addition, using only pathologically confirmed GCA, the same matched cohort comparison analysis also found that ZVL recipients were at significantly higher risk than those who did not receive ZVL (HR, 2.70; 95% CI, 1.48-4.95; P = .001).

CONCLUSION

Using a matched cohort, retrospective comparison, ZVL was associated with an increased incidence of GCA.

Is There an Association between Herpetic Infections and Giant Cell Arteritis? A Population-Based Study

Recent data suggests that herpes zoster (HZ) and herpes simplex virus (HSV) may be one of the underlying immunological triggers for giant cell arteritis (GCA). However, there is limited population-based data to support this. Our goal was to determine if herpetic infections increase the likelihood of GCA in the British Columbia (BC) population. The background prevalence of GCA was compared to the prevalence of GCA in subjects with HZ and HSV using diagnostic billing code data from an online BC database (BC Data Scout^TM). BC residents ≥30 years old at the time of diagnosis from January 2000 to January 2019 were included. The relevant International Classification of Disease codes was used to identify patients with GCA, HZ, and HSV. Comparisons were made using two-sample Z tests. There were 4315 GCA diagnoses, from a total population of 3,026,005 subjects. The prevalence of GCA was 143 per 100,000 people. In terms of herpetic infections, 850 GCA cases were identified in 249,900 subjects with HZ versus 310 diagnoses of GCA in 163,170 subjects with HSV. The prevalence of GCA in subjects with HZ (0.340%) was significantly higher than the prevalence of GCA (0.143%) in the general population (p < 0.00001). The prevalence of GCA in HSV subjects (0.190%) was also significantly higher (p < 0.00001) than the population prevalence but lower than (p < 0.00001) the GCA with HZ prevalence. The likelihood of GCA appears to increase with herpetic infections, more significantly with HZ.

The microbiome in autoimmune rheumatic disease

Microbial contributions to the immunopathogenesis of autoimmune rheumatic diseases have been studied since the advent of germ theory in the 19th century. With the exception of Group A Streptococcus in rheumatic fever, early studies failed to establish causal relationships between specific pathobionts and rheumatic disease. Today, systemic autoimmune diseases are thought to result from a complex interplay of environmental factors, individual genetic risk, and stochastic events. Interactions of microbiota and the immune system have been shown to promote and sustain chronic inflammation and autoimmunity. In mechanistic studies, microbe-immune cell interactions have been implicated in the initiation of autoimmune rheumatic diseases, e.g., through the posttranslational modification of autoantigens in rheumatoid arthritis or through neutrophil cell death and cross-reactivity with commensal orthologs in systemic lupus erythematosus. In parallel, modern molecular techniques have catalyzed the study of the microbiome in systemic autoimmune diseases. Here, I review current insights gained into the skin, oral, gut, lung, and vascular microbiome in connective tissue diseases and vasculitis. Mechanism relevant to the development and propagation of autoimmunity will be discussed whenever explored. While studies on autoimmune rheumatic disease have almost invariably shown abnormal microbiome structure (dysbiosis), substantial variability in microbial composition between studies makes generalization difficult. Moreover, an etiopathogenic role of specific pathobionts cannot be inferred by association alone. Integrating descriptive studies of microbial communities with hypothesis-driven research informed by immunopathogenesis will be important in elucidating targetable mechanisms in preclinical and established rheumatic disease.

[Physiopathology of giant cell arteritis: From inflammation to vascular remodeling]

Giant cell arteritis (GCA) is a large-vessel vasculitis involving the aorta and its main branches, especially supra aortic branches. Although much progress has been made, the pathophysiology remains incompletely understood. An initial trigger, suspected of infectious origin, lead to the maturation and recruitment of dendritic cells (DC). The lack of migration of these DC allows the local recruitment of T-lymphocytes (LT). These LT- CD4⁺ polarize in Type 1 helper (Th1), Th17 but also Th9. A qualitative and quantitative deficit in regulatory T cells (Treg) is observed under the influence of IL-21 overproduction. In addition, an imbalance in the Th17/Treg balance is favored by IL-6. The secretion of IFN-γ, IL-17, IL-6, IL-33 is responsible for a sustained local inflammatory reaction that is organized around tertiary lymphoid follicles. Locally recruited macrophages secrete reactive forms of oxygen together with VEGF and PDGF. These growth factors, together with neurotrophins and endothelin contribute to increase the proliferation of vascular smooth muscle cells (VSMCs). The imbalance between matrix metalloproteases (MMP)-2, MMP-9 and MMP-14 and tissue inhibitors of metalloproteases (TIMP)-1 and TIMP-2 also contribute to the remodeling process occurring in the vessel wall. Finally, arterial neovascularization contribute to the perpetuation of lymphocyte recruitment. This persistent remodeling is sometimes complicated by ischemic events responsible for the initial severity of the disease.

Varicella Zoster Virus in Giant Cell Arteritis: A Review of Current Medical Literature

In recent years, the search for the cause of giant cell arteritis (GCA) has led investigators to look to varicella zoster virus (VZV) as the answer. In some ways, the nature of VZV infection makes it an attractive explanation for the pathology observed in GCA. However, studies to date yield a level of inconsistency that still leaves uncertainty as to whether VZV directly causes GCA, and positive findings have not been successfully reproduced.

Pathogenesis of large vessel vasculitis: Implications for disease classification and future therapies

Despite being recognised over a century ago, the aetiology and pathogenesis of large vessel vasculitis (LVV) still remains elusive. Takayasu’s arteritis (TA) and giant cell arteritis (GCA) represent the two major categories of LVV, each with distinctive clinical features. Over the last 10 years an increased understanding of the immunopathogenesis of the inflammatory cascade within the aortic wall has revived the view that LVVs may represent subtypes of the same pathological process, with implications in the treatment of this disease. In this review, the histological, genetic and immunopathological features of TA and GCA will be discussed and the evidence for a common underlying disease mechanism examined. Novel markers of disease activity and therapies based on advances in our understanding of the immunopathogenesis of these conditions will also be discussed.

Giant cell arteritis: pathogenic mechanisms and new potential therapeutic targets

Giant cell arteritis (GCA) is the most common idiopathic systemic vasculitis in persons aged 50 years or greater. Treatment options for GCA, to-date, have been limited and have consisted primarily of glucocorticoids. Significant advances in the understanding of the genetic and cellular mechanisms in GCA are leading to identification of potential pathogenic targets. The recent success of interleukin-6 blockade in the treatment of GCA has opened the landscape to targeted biologic therapy. T cells, particularly T helper 1 and T helper 17 cell lineages have been identified as key inflammatory cells in both active and chronic vascular inflammatory lesions. Therapeutic agents, including abatacept and ustekinumab, which can impede both vasculitogenic cell lines are of particular interest. Inhibition of signalling pathways, including the janus kinase-signal tranducers and activation of transcription (JAK-STAT) and Notch pathways are evolving options. Tocilizumab has shown clear benefit in both newly diagnosed and relapsing patients with GCA and approval of this medication for treatment of GCA has led to rapid incorporation into treatment regimens. More information is required to understand the long-term outcomes of tocilizumab and other investigational targeted therapeutics in the treatment of GCA.

Varicella zoster virus and giant cell arteritis

PURPOSE OF REVIEW

Giant cell arteritis (GCA) is a serious disease and the most common cause of vasculitis in the elderly. Here, studies describing the recent discovery of varicella zoster virus (VZV) in the temporal arteries of patients with GCA are reviewed.

RECENT FINDINGS

GCA is characterized by severe headache/head pain and scalp tenderness. Many patients also have a history of vision loss, jaw claudication, polymyalgia rheumatica, fever, night sweats, weight loss, and fatigue. The erythrocyte sedimentation rate and C-reactive protein are usually elevated. Diagnosis is confirmed by temporal artery biopsy, which reveals vessel wall damage and inflammation, with multinucleated giant cells and/or epithelioid macrophages. Skip lesions are common. Importantly, temporal artery biopsies are pathologically negative in many clinically suspect cases. The present review highlights recent virological findings in temporal arteries from patients with pathologically verified GCA and in temporal arteries from patients who manifest clinical and laboratory features of GCA but whose temporal artery biopsies are pathologically negative for GCA. Virological analysis revealed that VZV is present in most GCA-positive and GCA-negative temporal artery biopsies, particularly in skip areas that correlate with adjacent GCA disease.

SUMMARY

The presence of VZV in GCA-positive and GCA-negative temporal arteries reflects the possible role of VZV in triggering the immunopathology of GCA and indicates that both groups of patients should be treated with antivirals in addition to corticosteroids. Whether oral antiviral agents and steroids are as effective as intravenous acyclovir and steroids, and the dosage and duration of treatment, remain to be determined.

Varicella zoster virus triggers the immunopathology of giant cell arteritis

PURPOSE OF REVIEW

Giant cell arteritis (GCA) is a severe form of vasculitis in the elderly. The recent discovery of varicella zoster virus (VZV) in the temporal arteries and adjacent skeletal muscle of patients with GCA, and the rationale and strategy for antiviral and corticosteroid treatment for GCA are reviewed.

RECENT FINDINGS

The clinical features of GCA include excruciating headache/head pain, often with scalp tenderness, a nodular temporal arteries and decreased temporal artery pulsations. Jaw claudication, night sweats, fever, malaise, and a history of polymyalgia rheumatica (aching and stiffness of large muscles primarily in the shoulder girdle, upper back, and pelvis without objective signs of weakness) are common. ESR and CRP are usually elevated. Diagnosis is confirmed by temporal artery biopsy which reveals vessel wall damage and inflammation, with multinucleated giant cells and/or epithelioid macrophages. Skip lesions are common. Importantly, temporal artery biopsies are pathologically negative in many clinically suspect cases. This review highlights recent virological findings in temporal arteries from patients with pathologically verified GCA and in temporal arteries from patients who manifest clinical and laboratory features of GCA, but whose temporal artery biopsies (Bx) are pathologically negative for GCA (Bx-negative GCA). Virological analysis revealed that VZV is present in most GCA-positive and GCA-negative temporal artery biopsies, mostly in skip areas that correlate with adjacent GCA pathology.

SUMMARY

The presence of VZV in Bx-positive and Bx-negative GCA temporal arteries indicates that VZV triggers the immunopathology of GCA. However, the presence of VZV in about 20% of temporal artery biopsies from non-GCA postmortem controls also suggests that VZV alone is not sufficient to produce disease. Treatment trials should be performed to determine if antiviral agents confer additional benefits to corticosteroids in both Bx-positive and Bx-negative GCA patients. These studies should also examine whether oral antiviral agents and corticosteroids are as effective as intravenous acyclovir and corticosteroids. Appropriate dosage and duration of treatment also remain to be determined.

No detection of varicella-zoster virus in temporal arteries of patients with giant cell arteritis

OBJECTIVE

Data on the presence of varicella-zoster virus (VZV) in temporal arteries of patients with giant cell arteritis (GCA) are controversial. We analyzed VZV infection in temporal arteries from Italian patients with temporal artery biopsy (TAB)-positive GCA, TAB-negative GCA, and controls.

METHODS

A total of 79 formalin-fixed, paraffin-embedded (FFPE) TABs performed between 2009 and 2012 at a single institution from 34 TAB-positive GCA patients, 15 TAB-negative GCA patients, and 30 controls were retrieved. Six 5-μm sections of all FFPE TABs were cut. The first section was analyzed by immunohistochemistry using mouse monoclonal anti-VZVgE IgG1 antibody. DNA was extracted from the remaining five sections and analyzed by real-time polymerase chain reaction (PCR) for the presence of VZV DNA. For 10 of the 34 TAB-positive GCA patients, an additional 2-mm piece of frozen TAB was available. DNA was extracted from the entire 2-mm length frozen specimen and analyzed by PCR for the presence of VZV DNA. Thirty additional 5-μm sections were cut from the FFPE TABs of these 10 patients and analyzed by immunohistochemistry for the presence of VZV antigen.

RESULTS

Immunohistochemical analysis detected VZV antigen in 1/34 (3%) TAB-positive GCA, 0/15 TAB-negative GCA, and 0/30 controls, and in none of the 300 sections cut from the 10 FFPE TABs positive for GCA for which the frozen specimens were available. DNA obtained from all TABs was amplifiable. VZV DNA was neither found in any of the FFPE TABs nor found in frozen TABs.

CONCLUSION

Our data do not support in Italian patients a possible role for VZV infection in the etiopathogenesis of GCA.

The role of toll like receptors in giant cell arteritis

GCA is a common primary systemic vasculitis that results in granulomatous inflammation of medium to large arteries. Both innate and adaptive immune mechanisms combine to drive intimal hyperplasia, luminal stenosis and ultimately occlusion. While the pathogenesis of GCA is incompletely understood, the activation of resident adventitial dendritic cells via toll like receptors (TLRs) appears to be a crucial inciting event. Here we explore the role of TLRs in the pathogenesis of GCA, including their effects on dendritic cell and T cell activation and recruitment, putative infectious triggers for GCA and the potential of TLR inhibition as a novel therapeutic strategy in GCA.

New developments in giant cell arteritis

Giant cell arteritis (GCA) is a medium-to-large vessel vasculitis with potentially sight- and life- threatening complications. Our understanding of the pathogenesis, diagnosis, and treatment of GCA has advanced rapidly in recent times. The validity of using the American College of Rheumatology guidelines for diagnosis of GCA in a clinical setting has been robustly challenged. Erythrocyte sedimentation rate, an important marker of inflammation, is lowered by the use of statins and nonsteroidal anti-inflammatory drugs. Conversely, it may be falsely elevated with a low hematocrit. Despite the emergence of new diagnostic modalities, temporal artery biopsy remains the gold standard. Evidence suggests that shorter biopsy lengths and biopsies done weeks to months after initiation of steroid therapy are still useful. New imaging techniques such as positron emission tomography have shown that vascular inflammation in GCA is more widespread than originally thought. GCA, Takayasu arteritis, and polymyalgia rheumatica are no longer thought to exist as distinct entities and are more likely parts of a spectrum of disease. A range of immunosuppressive drugs have been used in conjunction with corticosteroids to treat GCA. In particular, interleukin-6 inhibitors are showing promise as a therapy.

Infectious triggers for vasculitis

PURPOSE OF REVIEW

Infections have been suggested to contribute to disease induction and reactivation in many of the idiopathic vasculitides. This review describes and evaluates the evidence that microbes are involved in the etiopathogenesis of these diseases.

RECENT FINDINGS

Large-vessel vasculitis has recently been associated with two specific bacteria. Mycobacterium tuberculosis is thought to have an inducing role in Takayasu arteritis and a Burkholderia bacterium might be involved in giant cell arteritis. Hepatitis B and C viruses have been linked to polyarteritis nodosa. In antineutrophil cytoplasmic autoantibody-associated vasculitis, and more specifically granulomatosis with polyangiitis (GPA), Staphylococcus aureus has been the focus of many studies. Chronic nasal carriage of S. aureus is related to endonasal activity and disease relapses in GPA patients. Moreover, antibacterial treatment is known to reduce the risk for disease relapses. If and how pathogens trigger vasculitis is still unclear, but several potential mechanisms have been suggested and are briefly reviewed here.

SUMMARY

Although many observations suggest a link between infections and the development of vasculitis, no direct proof exists. Transcriptomic and proteomic studies of the pathogens involved could aid in identifying specific or common traits of pathogens that are relevant for the development and reactivation of vasculitis.

Vasculitis related to viral and other microbial agents

Vasculitis due to infection may occur as a consequence of the inflammation of vessel walls due to direct or contiguous infection, type II or immune complex-mediated reaction, cell-mediated hypersensitivity, or inflammation due to immune dysregulation triggered by bacterial toxin and/or superantigen production. As immunosuppressive therapy administered in the absence of antimicrobial therapy may increase morbidity and fail to effect the resolution of infection-associated vascular inflammation, it is important to consider infectious entities as potential inciting factors in vasculitis syndromes. The causality between infection and vasculitis has been established in hepatitis B-associated polyarteritis nodosa (HBV-PAN) and hepatitis C-associated (cryoglobulinemic) vasculitis (HCV-CV). The review summarizes the recent literature on the pathophysiological mechanisms and the approaches to the management of HBV-PAN and HCV-CV. Roles of other viral and microbial infections, which either manifest as vasculitic syndromes or are implicated in the pathogenesis of primary vasculitides, are also discussed.

Prevalence and distribution of VZV in temporal arteries of patients with giant cell arteritis

OBJECTIVE

Varicella-zoster virus (VZV) infection may trigger the inflammatory cascade that characterizes giant cell arteritis (GCA).

METHODS

Formalin-fixed, paraffin-embedded GCA-positive temporal artery (TA) biopsies (50 sections/TA) including adjacent skeletal muscle and normal TAs obtained postmortem from subjects >50 years of age were examined by immunohistochemistry for presence and distribution of VZV antigen and by ultrastructural examination for virions. Adjacent regions were examined by hematoxylin & eosin staining. VZV antigen-positive slides were analyzed by PCR for VZV DNA.

RESULTS

VZV antigen was found in 61/82 (74%) GCA-positive TAs compared with 1/13 (8%) normal TAs (p < 0.0001, relative risk 9.67, 95% confidence interval 1.46, 63.69). Most GCA-positive TAs contained viral antigen in skip areas. VZV antigen was present mostly in adventitia, followed by media and intima. VZV antigen was found in 12/32 (38%) skeletal muscles adjacent to VZV antigen-positive TAs. Despite formalin fixation, VZV DNA was detected in 18/45 (40%) GCA-positive VZV antigen-positive TAs, in 6/10 (60%) VZV antigen-positive skeletal muscles, and in one VZV antigen-positive normal TA. Varicella-zoster virions were found in a GCA-positive TA. In sections adjacent to those containing VZV, GCA pathology was seen in 89% of GCA-positive TAs but in none of 18 adjacent sections from normal TAs.

CONCLUSIONS

Most GCA-positive TAs contained VZV in skip areas that correlated with adjacent GCA pathology, supporting the hypothesis that VZV triggers GCA immunopathology. Antiviral treatment may confer additional benefit to patients with GCA treated with corticosteroids, although the optimal antiviral regimen remains to be determined.

Association between human papillomavirus DNA and temporal arteritis

Background

To examine the relationship between human papillomavirus (HPV) and giant cell arteritis (GCA) of the temporal artery.

Methods

The study group consisted of 22 cases of histologically positive/biopsy confirmed GCA. The control groups consisted of 21 histologically negative temporal artery biopsies and fifteen cases of vascular margins of nephrectomies. For detection of the presence of HPV, two methods were used: 1) polymerase chain reaction (PCR) with INNO-LiPA HPV Genotyping Extra, 2) Cervista™ HPV HR. All cases were from the files of the Barnes-Jewish Hospital and Washington University in St. Louis.

Results

HPV DNA was detected by PCR and genotyping in 16 of 22 (73%) histologically positive cases of GCA and in only five of 21 (24%) histologically negative temporal artery biopsies. Among the vascular margin controls, only three of 15 (20%) were positive for HPV DNA. The second, independent method (Cervista^TM) confirmed the aforesaid results with 100% concordance with the exception of three cases which had low genomic DNA for which it was not possible to perform the test. The differences in HPV positivity between the histologically positive and negative temporal artery biopsies and between the histologically positive temporal artery biopsies and controls were both statistically significant (p = 0.001 and 0.002, respectively).

Conclusions

The results of our study revealed a statistically significant association between HPV positivity and biopsy confirmed temporal giant cell arteritis GCA (p = 0.001). Further studies are necessary to elucidate the pathophysiology underlying this association.

Viral detection in hydrops fetalis, spontaneous abortion, and unexplained fetal death in utero

This study was undertaken to investigate the occurrence of viral infection in fetal death by examining tissues for the presence of DNA of several viral agents. Tissue specimens including heart, kidney, liver, lung, and placenta of 73 cases of fetal death were examined with 27 cases of elective termination of pregnancy as a control group. DNA extracted from these samples was tested for the presence of HSV, CMV, EBV, VZV, HHV-6, HHV-7, and PVB19. Viral DNA was found in one or more tissue samples from 25/73 cases (34%): CMV in 20, HSV in 5, parvovirus B19 in 5, HHV-7 in 3, and HHV-6 in 2. The presence of HHV-6 in fetal tissue has been reported rarely. No study so far has reported the detection of HHV-7 in fetal tissues with normal or adverse outcomes. Viral DNA was not found in any of the termination of pregnancy samples. Among the positive cases, eight had dual infection. One further case was positive for three viruses: HSV, CMV, and HHV-7. HHV-6 was the sole infectious agent in two cases, HHV-7 in one case, PVB19 in three, and CMV in ten cases. The finding of multiple viral DNA in 12% of the cases suggests the involvement of complex risk factors in cases of fetal loss. Although the cause of fetal death often includes other factors (e.g., chromosomal abnormalities) these data suggest the incidence of viral infective etiology may be higher than considered previously. However, larger studies are required to establish this link.

Pathogenesis of giant cell arteritis: More than just an inflammatory condition?

Giant cell arteritis (GCA) is characterized by intimal hyperplasia and luminal obstruction leading to ischemic manifestations involving extra-cranial branches of carotid arteries and aorta. Histopathological lesions involve all layers of the arterial wall and are associated with multinucleated giant cells, fragmented internal elastic lamina and polymorphic cellular infiltrates, including T lymphocytes and macrophages. The pathophysiology of GCA is still poorly understood. After dendritic cell activation, CD4(+) T lymphocytes, T helper 1 (Th1) cells, produce interferon gamma and modulate macrophage activation and functions, and Th17 cells produce interleukin 17 (IL-17), which can induce cytokine production by macrophages and fibroblasts. Macrophages in the adventitia produce pro-inflammatory cytokines such as IL-1, IL-6 and tumor necrosis factor alpha. These cytokines promote arterial wall and systemic inflammation. Questions remain regarding the nature of the antigen(s) triggering dendritic cell activation and the mechanisms underlying vascular remodeling. Here we review recent advances in the pathogenesis of GCA, with emphasis on the interactions between cells of the immune system and components of the vessel wall, including vascular smooth muscle cells and endothelial cells, leading to vascular remodeling. Finally, we propose new areas of investigation that could help understand the triggering factors and key pathogenic events in GCA.

Vasculitis and infections: contribution to the issue of autoimmunity reviews devoted to "autoimmunity and infection"

Infections are associated with secondary forms of vasculitis. However, there is increasing evidence that microbial agents play a role also in primary systemic vasculitides. For a long time it has been noted that Hepatitis B virus (HBV) is involved in polyarteritis nodosa (PAN) although the incidence of HBV-associated PAN seems to decline. Cryoglobulinemic vasculitis has been shown to be strongly associated with Hepatitis C Virus (HCV) infection, but this is most striking in Southern Europe and less in Northern Europe. Different microbial agents have been suggested to influence disease expression in other primary vasculitides but no specific association has been established. In Wegener’s Granulomatosis (WG) chronic carriage of Staphylococcus aureus (S. aureus) is associated with a strongly increased risk for relapsing disease. Various pathogenic pathways for this association have been suggested by clinical and experimental observations. Recent studies even suggest that S. aureus derived peptides, amongst others, may induce proteinase 3-ANCA via idiotypic–anti-idiotypic interactions. Treatment with co-trimoxazole in WG localized to the upper airways may result in (temporary) remission of the disease.