Value of biomarkers for predicting immunoglobulin A vasculitis nephritis outcome in an adult prospective cohort

A specific diagnostic metabolome signature in adult IgA vasculitis

INTRODUCTION

IgA vasculitis diagnosis relies primarily on clinical features and is confirmed by pathological findings. To date, there is no reliable noninvasive diagnostic biomarker.

OBJECTIVE

We aimed to explore the baseline serum metabolome of adult patients with IgA vasculitis to identify potential diagnostic biomarkers.

METHODS

We performed a study comparing the serum metabolome of patients with IgA vasculitis to that of patients with inflammatory condition, namely spondyloarthritis. Serum analyses were performed by high-performance liquid chromatography-mass spectrometry.

RESULTS

Fifty-five patients with IgA vasculitis and 77 controls with spondyloarthritis (age- and sex-matched) were included in this study. The median age of IgA vasculitis patients was 53 years. Two-thirds of patients were female (n = 32). At the time of vasculitis diagnosis, 100% of patients had skin involvement and 69% presented with glomerulonephritis (n = 38). Joint and digestive involvement were observed in 56% (n = 31) and 42% (n = 23) of patients. Four discriminative metabolites between the two groups were identified: 1-methyladenosine, L-glutamic acid, serotonin, and thymidine. The multivariate model built from the serum metabolomes of patients with IgA vasculitis and spondyloarthritis revealed an accuracy > 90%. As this model was significant according to the permutation test (p < 0.01), independent validation showed an excellent predictive value of the test set: sensitivity 98%; specificity 98%, positive predictive value 97% and negative predictive value 98%.

CONCLUSION

To our knowledge, this study is the first to use the metabolomic approach for diagnostic purposes in adult IgA vasculitis, highlighting a specific diagnostic metabolome signature.

Association of the Monocyte-to-High-Density Lipoprotein Cholesterol Ratio with Gastrointestinal Involvement of Immunoglobulin a Vasculitis

Objective

To illustrate the association of monocyte to high-density lipoprotein cholesterol ratio (MHR) and other serum indicators with the pathogenesis and prognosis of immunoglobulin A vasculitis (IgAV) patients in different subgroups.

Methods

A total of 158 adult patients and 113 healthy controls were enrolled, and the clinical presentation and laboratory indexes were comprehensively assessed.

Results

IgAV patients show significantly elevated levels of inflammatory parameters and lipid profiles compared to healthy controls (P < 0.05). Higher levels of the MHR and other normal inflammatory indicators were found in patients with Gastrointestinal (GI) involvement compared to other subgroups. And in group with GI involvement, significantly higher white blood cell (WBC), neutrophil, complement 4 (C4), NLR (neutrophil-to-lymphocyte ratio) and PLR (platelet-to-lymphocyte ratio) levels and lower levels of apolipoprotein-a (Apo-a) were observed. Their correlation analysis demonstrated positive results between MHR level and white blood cell (WBC) count (r = 0.416, P = 0.034), D-Dimer (r = 0.464, P = 0.026) and monocyte (r = 0.947, P < 0.001). And the time until first remission of skin purpura was shown positively correlated with their age (r = 0.456, P = 0.043), C-reactive protein (CRP) level (r = 0.641, P = 0.018), D-Dimer level (r = 0.502, P = 0.040) while negatively correlated with albumin (Alb) level (r=-0.626, P = 0.003) and low-density lipoprotein (LDL) level (r=-0.478, P = 0.033).

Conclusion

Our study suggests that those biomarkers represented for inflammatory responses, lipid profile and immunological functions have significant differences in the subgroups of adult IgAV patients. In addition, we also found that MHR level may serve as a potential biomarker for the pathogenesis and prognosis of IgAV patients with GI involvement.

Pathophysiology and clinical manifestations of immune complex vasculitides

Immune complex (IC) vasculitides present inflammations of vessel walls associated with perivascular deposition of immunoglobulins (Igs), mostly ICs. They encompass systemic and skin-limited variants of IgA vasculitis (IgAV), cryoglobulinemic vasculitis (CV), rheumatoid, lupus, and hypocomplementemic vasculitides, serum sickness cutaneous IgM/IgG (non-IgA) vasculitis, and recurrent macular (hypergammaglobulinemic or exertion-induced) vasculitis. Serum sickness and CV fulfill the criteria of a type III hypersensitivity immune reaction as large lattices of the IC precipitate at vessel walls and activate polymorphonuclear neutrophils (PMNs). Immunoglobulin-A vasculitis differs with regard to the causes of perivascular deposition of ICs since here many IgA1 molecules are hypoglycosylated (Gd-IgA1), which appears to facilitate their perivascular deposition in skin and mesangium (via e.g. CD71). The reasons for increased generation of immunoglobulins or formation of IC and their perivascular deposition in either skin or systemic organs are different and not fully explored. A common denominator of OC vasculitides is the activation of PMNs near the vessel wall via Fcy or Fcα receptors. Acute episodes of IgAV additionally require PMNs to become preactivated by IgA1 or by IC already in circulation. This intravascular priming results in increased adherence and subsequently vessel-destructive NETosis when they encounter IgA deposited at the vessel walls. Binding of IgA1 to PMNs in blood stream is associated with increased serum levels of hypogalactosidated IgA1. The characteristic clinical picture of IgAV (and also of so-called IgG/IgM vasculitis) comprises palpable or retiform purpura with a clear predilection for lower legs, probably due to stasis-related reduction in blood velocity, while in other IC vasculitides, additional factors influence the sites of vasculitides. Our knowledge of distinct forms and different pathophysiological pathways of IC vasculitides may lead to in efficacious or targeted therapies. Antibodies to complement components or intestinal budesonide for IgAV are promising agents (the latter suppresses the pathophysiologically related IgA nephropathy by reducing the generation of mucosal IgA.

Hemoperfusion and intravenous immunoglobulins for refractory gastrointestinal involvement in pediatric Henoch-Schönlein purpura: a single-center retrospective cohort study

BACKGROUND

Henoch-Schönlein purpura (HSP) with refractory gastrointestinal (GI) symptoms is always difficult to handle because of its resistance to supportive therapies and glucocorticoid. This study aimed to evaluate the efficacy of hemoperfusion (HP) and intravenous immunoglobulins (IVIG) therapies in this population.

METHODS

Sixty-four HSP patients with refractory GI involvement (R-GI group) and 64 cases with mild GI symptoms (control group) were retrospectively analyzed in our center from March 2016 to October 2019. In R-GI group, 42 cases (subgroup A) were treated with IVIG and steroid, 13 cases (subgroup B) used HP and steroid, 9 cases (subgroup C) executed a combination of IVIG, HP and steroid. Demographic characteristics, clinical features, laboratory indexes and treatment outcomes were recorded. t-test, One-way ANOVA, Mann-Whitney U test, and multivariate logistic regression were used in comparing differences among subgroups and predicting independent risk factors.

RESULTS

Compared with the control group, R-GI cases experienced higher risk of renal involvement (P = 0.000), more steroid exposure (P = 0.000), six times expenses (P = 0.000) and 2.3 times length of hospitalization (P = 0.000). The independent risk factors of R-GI group were elevated neutrophils (OR 1.250 [95% CI 1.130-1.383]) and the percentage of B lymphocytes (OR 1.100 [95% CI 1.026-1.179]) as well as decreased IgG (OR 0.847 [95% CI 0.732-0.98]). In R-GI group, increased age (OR 1.039 [95% CI 1.016-1.062]) and IgM (OR 5.994 [95% CI 1.403-27.611]) were verified to be risk factors of HSP nephritis. All three subgroups could alleviate the symptoms effectively. Compared with those in subgroup A, patients in subgroup B were elder (P = 0.004), had less relapse (P = 0.002), steroid exposure (P = 0.033) and expenses (P = 0.031), more significant decrease of WBC (P = 0.026) after treatment.

CONCLUSION

The HSP with refractory GI involvement had much higher risk of medical burden and renal involvement. Both IVIG and HP therapies could ameliorate refractory GI symptoms efficiently. HP therapy tended to reduce the relapse, costs and steroid exposure in its audiences who were cooperated and with stable hemodynamics, while IVIG had better use in younger children.

Increased Urinary IgA in Paediatric IgA Vasculitis Nephritis

IgA vasculitis (IgAV) is the most common form of paediatric vasculitis, with up to 50% of patients experiencing kidney inflammation. Much remains unknown about IgAV, but it is believed to arise due to galactose-deficient IgA1 promoting an auto-inflammatory response. This study assesses whether urinary IgA can be detected in children with IgAV to allow further evaluation of IgA1 and whether it has any relationship with nephritis. Urinary and serum IgA concentrations were measured using commercially available ELISA kits. Patients were grouped into IgAV nephritis (IgAVN) or IgAV without nephritis (IgAVwoN). Fifty-nine children were included: IgAVN n = 12, IgAVwoN n = 35, and healthy controls (HC) n = 12, with a mean age of 8.2 ± 4.1 years. Urinary IgA concentrations were statistically significantly higher in patients with IgAV (107.1 ± 136.3 μg/mmol) compared to HC (50.6 ± 26.3 μg/mmol; p = 0.027) and IgAVN (229.8 ± 226.3 μg/mmol) compared to both IgAVwoN (65.0 ± 37.8 μg/mmol; p = 0.002) and HC (p < 0.001). Urinary IgA concentrations were able to distinguish between renal status (AUC 0.838, 95%CI [0.704−0.973], p < 0.001) and did not correlate with proteinuria (r = 0.124; p = 0.407). Urinary IgA concentrations are increased in children with IgAVN, and it has the potential to act as a non-invasive biofluid to further evaluate nephritis in this disease.

IgA vasculitis update: Epidemiology, pathogenesis, and biomarkers

Immunoglobulin A vasculitis (IgAV), formerly known as Henoch-Schönlein purpura, is the most common systemic vasculitis in children, characterized by diverse clinical manifestations with a wide spectrum ranging from isolated cutaneous vasculitis to systemic involvement. The incidence of IgAV is geographically and ethnically variable, with a prevalence in autumn and winter, suggesting a driving role that genetic and environmental factors play in the disease. Although IgAV has a certain degree of natural remission, it varies widely among individuals. Some patients can suffer from severe renal involvement and even progress to end-stage renal disease. Its pathogenesis is complex and has not been fully elucidated. The formation of galactose-deficient IgA1 (Gd-IgA1) and related immune complexes plays a vital role in promoting the occurrence and development of IgAV nephritis. In addition, neutrophil activation is stimulated through the binding of IgA to the Fc alpha receptor I expressed on its surface, resulting in systemic vascular inflammation and tissue damage. Starting from the epidemiological characteristics, this article will review the role of immunological factors such as Gd-IgA1, autoantibodies, circulating immune complexes, complement system, cellular immunization, and the contributions of environmental and genetic factors in the pathogenesis of IgAV, and conclude with the major biomarkers for IgAV.

Individualized medication based on pharmacogenomics and treatment progress in children with IgAV nephritis

Immunoglobulin A vasculitis (IgAV) nephritis, also known as Henoch-Schönlein purpura nephritis (HSPN), is a condition in which small blood vessel inflammation and perivascular IgA deposition in the kidney caused by neutrophil activation, which more often leads to chronic kidney disease and accounts for 1%–2% of children with end-stage renal disease (ESRD). The treatment principles recommended by the current management guidelines include general drug treatment, support measures and prevention of sequelae, among which the therapeutic drugs include corticosteroids, immunosuppressive agents and angiotensin system inhibitors. However, the concentration range of immunosuppressive therapy is narrow and the individualized difference is large, and the use of corticosteroids does not seem to improve the persistent nephropathy and prognosis of children with IgAV. Therefore, individualized maintenance treatment of the disease and stable renal prognosis are still difficult problems. Genetic information helps to predict drug response in advance. It has been proved that most gene polymorphisms of cytochrome oxidase P450 and drug transporter can affect drug efficacy and adverse reactions (ADR). Drug therapy based on genetics and pharmacogenomics is beneficial to providing safer and more effective treatment for children. Based on the pathogenesis of IgAV, this paper summarizes the current therapeutic drugs, explores potential therapeutic drugs, and focuses on the therapeutic significance of corticosteroids and immunosuppressants in children with IgAV nephritis at the level of pharmacogenomics. In addition, the individualized application of corticosteroids and immunosuppressants in children with different genotypes was analyzed, in order to provide a more comprehensive reference for the individualized treatment of IgAV nephritis in children.

IgA vasculitis with nephritis: update of pathogenesis with clinical implications

IgA vasculitis with nephritis (IgAVN) shares many pathogenetic features with IgA nephropathy (IgAN). The purpose of this review is to describe our current understanding of the pathogenesis of pediatric IgAVN, particularly as it relates to the four-hit hypothesis for IgAN. These individual steps, i.e., hits, in the pathogenesis of IgAN are (1) elevated production of IgA1 glycoforms with some O-glycans deficient in galactose (galactose-deficient IgA1; Gd-IgA1), (2) generation of circulating IgG autoantibodies specific for Gd-IgA1, (3) formation of pathogenic circulating Gd-IgA1-containing immune complexes, and (4) kidney deposition of the Gd-IgA1-IgG immune complexes from the circulation and induction of glomerular injury. Evidence supporting the four-hit hypothesis in the pathogenesis of pediatric IgAVN is detailed. The genetics, pediatric outcomes, and kidney histopathologic features and the impact of these findings on future treatment and potential biomarkers are discussed. In summary, the evidence points to the critical roles of Gd-IgA1-IgG immune complexes and complement activation in the pathogenesis of IgAVN. Future studies are needed to characterize the features of the immune and autoimmune responses that enable progression of IgA vasculitis to IgAVN.

Involvement of Inflammasome Components in Kidney Disease

Inflammasomes are multiprotein complexes with an important role in the innate immune response. Canonical activation of inflammasomes results in caspase-1 activation and maturation of cytokines interleukin-1β and -18. These cytokines can elicit their effects through receptor activation, both locally within a certain tissue and systemically. Animal models of kidney diseases have shown inflammasome involvement in inflammation, pyroptosis and fibrosis. In particular, the inflammasome component nucleotide-binding domain-like receptor family pyrin domain containing 3 (NLRP3) and related canonical mechanisms have been investigated. However, it has become increasingly clear that other inflammasome components are also of importance in kidney disease. Moreover, it is becoming obvious that the range of molecular interaction partners of inflammasome components in kidney diseases is wide. This review provides insights into these current areas of research, with special emphasis on the interaction of inflammasome components and redox signalling, endoplasmic reticulum stress, and mitochondrial function. We present our findings separately for acute kidney injury and chronic kidney disease. As we strictly divided the results into preclinical and clinical data, this review enables comparison of results from those complementary research specialities. However, it also reveals that knowledge gaps exist, especially in clinical acute kidney injury inflammasome research. Furthermore, patient comorbidities and treatments seem important drivers of inflammasome component alterations in human kidney disease.

Pathogenesis of IgA Vasculitis: An Up-To-Date Review

Immunoglobin A (IgA) vasculitis (IgAV), formerly called the Henoch-Schönlein purpura (HSP), is a small vessel vasculitis, characterized by IgA1-dominant immune deposition at diseased vessel walls. IgAV is the most common form of vasculitis in children; typical symptoms include palpable purpura, arthritis or arthralgia, abdominal pain, and hematuria or proteinuria. Galactose-deficient IgA1 is detected in the tissues of the kidney and skin in patients with IgAV; it forms immune complexes leading to subsequent immune reactions and injuries. This report provides the recent advances in the understanding of environmental factors, genetics, abnormal innate and acquired immunity, and the role of galactose-deficient IgA1 immunocomplexes in the pathogenesis of IgAV.

Correlations of Serological Markers with Development of Systemic Involvement in Adult Immunoglobulin A Vasculitis: A Retrospective Study of 259 Patients in Central China

OBJECTIVE

Although relatively rare, adult immunoglobulin A vasculitis (IgAV) can lead to severe complications and longer hospitalization, and result in poor prognosis, when compared to childhood IgAV. Hence, early identification and prevention for patients prone to develop systemic involvement are essential. The purpose of this study was to explore the correlations of common serological markers with the development of systemic involvement in adult IgAV.

METHODS

A retrospective analysis was performed for adult IgAV patients, who were hospitalized in Wuhan Union Hospital between January 2016 and December 2019. A total of 259 patients were enrolled, and the pre-treatment serological markers were comprehensively assessed.

RESULTS

In the present study, 49.0% and 33.2% of patients developed renal and gastrointestinal (GI) involvement, respectively. Furthermore, the elevated levels of white blood cells count, D-Dimer (D-D), C-reactive protein (CRP) and neutrophil granulocyte ratio (NE%) >60% were significantly associated with GI involvement in the univariate analysis, while the decrease in high density lipoprotein level, and the elevated D-D and CRP levels were significantly associated with renal involvement (P<0.05). Moreover, a prediction model that combined multiple markers was established by performing a logistic regression analysis, and this presented a more favorable value of prediction than the individual serological markers.

CONCLUSION

The present study suggests that common serological markers have close correlations with systemic involvement in adult IgAV, and that the establishment of a prediction model for systemic involvement may be helpful in facilitating personalized therapeutic strategies and clinical management for IgAV patients.

IgA vasculitis nephritis in children and adults: one or different entities?

The clinical features of the kidney involvement in immunoglobulin A (IgA) vasculitis (IgAVN) differ in children and adults for both clinical presentation and progression. IgAVN in children has mostly a self-limiting course and favorable resolution, while in adults the kidney involvement is frequently severe with unfavorable outcome. However, a subset of children is at risk of progression within the pediatric age or decades later in adulthood, particularly when the diagnosis and a prompt intervention are delayed. Factors predicting progression and outcome in the whole spectrum of age have been investigated in recent research, as well as the relationship between IgAVN and primary IgAN, which share the same pathology features, in the light of peculiar clinical differences and progression tendencies, and hence need for selective treatments. The search for a personalized treatment in children with IgAV and in different ages of life should rely on the identification of different risks for progression. This review will focus on recent studies which contribute to improve our knowledge in this still largely unclear area.

IgA Vasculitis: Etiology, Treatment, Biomarkers and Epigenetic Changes

IgA, previously called Henoch-Schönlein vasculitis, is an essential immune component that drives the host immune response to the external environment. As IgA has the unique characteristic of a flexible response to broad types of microorganisms, it sometimes causes an autoreactive response in the host human body. IgA vasculitis and related organ dysfunction are representative IgA-mediated autoimmune diseases; bacterial and viral infections often trigger IgA vasculitis. Recent drug developments and the presence of COVID-19 have revealed that these agents can also trigger IgA vasculitis. These findings provide a novel understanding of the pathogenesis of IgA vasculitis. In this review, we focus on the characteristics of IgA and symptoms of IgA vasculitis and other organ dysfunction. We also mention the therapeutic approach, biomarkers, novel triggers for IgA vasculitis, and epigenetic modifications in patients with IgA vasculitis.

IgA vasculitis

IgA vasculitis (IgAV) is an inflammation of small vessels caused by perivascular deposition of IgA and activation of neutrophils. It may present as systemic vasculitis (IgAV - Henoch-Schönlein purpura) or as a variant restricted to the skin (skin-limited IgAV), while IgA nephropathy presents a variant restricted to the kidneys. Systemic IgAV affects children more frequently than adults (150 to 200 for 1; incidence 1 in 1 million/year). In the latter, disease more often leads to chronic renal disease. The dominant clinical features include round or oval and retiform palpable purpura predominantly on the lower legs, arthralgia or arthritis, gastrointestinal bleeding or pain and glomerulonephritis with mesangial IgA deposits (IgAVN). Pulmonary, cardiac, genital and neurological involvement occurs, but is rare. Immune complexes containing galactose-deficient IgA1 play a pivotal role in the pathophysiology of IgAV; via the Fc alpha receptor (CD89), they induce neutrophilic inflammation around cutaneous vessels and mesangial proliferation and inflammation in the glomerulus. In case of self-limited disease, only symptomatic treatment is recommended. Treatment of severe IgAV, nephritis or gastrointestinal manifestations, is not established, but some studies reported a benefit of corticosteroids, combined with immunosuppressive drugs. Short-term outcome depends on the severity of gastrointestinal manifestations, while long-term prognosis depends on the severity of nephritis.

IgA Vasculitis and IgA Nephropathy: Same Disease?

Many authors suggested that IgA Vasculitis (IgAV) and IgA Nephropathy (IgAN) would be two clinical manifestations of the same disease; in particular, that IgAV would be the systemic form of the IgAN. A limited number of studies have included sufficient children or adults with IgAN or IgAV (with or without nephropathy) and followed long enough to conclude on differences or similarities in terms of clinical, biological or histological presentation, physiopathology, genetics or prognosis. All therapeutic trials available on IgAN excluded patients with vasculitis. IgAV and IgAN could represent different extremities of a continuous spectrum of the same disease. Due to skin rash, patients with IgAV are diagnosed precociously. Conversely, because of the absence of any clinical signs, a renal biopsy is practiced for patients with an IgAN to confirm nephropathy at any time of the evolution of the disease, which could explain the frequent chronic lesions at diagnosis. Nevertheless, the question that remains unsolved is why do patients with IgAN not have skin lesions and some patients with IgAV not have nephropathy? Larger clinical studies are needed, including both diseases, with a common histological classification, and stratified on age and genetic background to assess renal prognosis and therapeutic strategies.

IgA and FcαRI: Versatile Players in Homeostasis, Infection, and Autoimmunity

Mucosal surfaces constitute the frontiers of the body and are the biggest barriers of our body for the outside world. Immunoglobulin A (IgA) is the most abundant antibody class present at these sites. It passively contributes to mucosal homeostasis via immune exclusion maintaining a tight balance between tolerating commensals and providing protection against pathogens. Once pathogens have succeeded in invading the epithelial barriers, IgA has an active role in host-pathogen defense by activating myeloid cells through divers receptors, including its Fc receptor, FcαRI (CD89). To evade elimination, several pathogens secrete proteins that interfere with either IgA neutralization or FcαRI-mediated immune responses, emphasizing the importance of IgA-FcαRI interactions in preventing infection. Depending on the IgA form, either anti- or pro-inflammatory responses can be induced. Moreover, the presence of excessive IgA immune complexes can result in continuous FcαRI-mediated activation of myeloid cells, potentially leading to severe tissue damage. On the one hand, enhancing pathogen-specific mucosal and systemic IgA by vaccination may increase protective immunity against infectious diseases. On the other hand, interfering with the IgA-FcαRI axis by monovalent targeting or blocking FcαRI may resolve IgA-induced inflammation and tissue damage. This review describes the multifaceted role of FcαRI as immune regulator between anti- and pro-inflammatory responses of IgA, and addresses potential novel therapeutic strategies that target FcαRI in disease.

Point your SmartPhone at the code above. If you have a QR code reader the video abstract will appear. Or use:

https://youtu.be/xlijXy5W0xA

Serum TNF-α Level Is Associated with Disease Severity in Adult Patients with Immunoglobulin A Vasculitis Nephritis

Background

Tumor necrosis factor-α (TNF-α) is a proinflammatory factor involved in the pathogenesis of immunoglobulin A vasculitis (IgAV). The association between serum TNF-α and disease severity in adult patients with IgAV nephritis (IgAV-N) has been inadequately evaluated.

Methods

Serum TNF-α was measured by chemiluminescence immunoassay in 53 renal biopsy-proved IgAV-N patients, 53 healthy controls, and 53 IgA nephropathy (IgAN) patients. The correlations of clinicopathologic parameters of IgAV-N patients with serum TNF-α were analyzed.

Results

In this cross-sectional study, the median age of IgAV-N patients was 29 (25-37) years, and 67.9% were female. Serum TNF-α was significantly higher in the IgAV-N group than in the healthy group [7.4 (5.7-9.4) pg/mL vs. 5.9 (5.0, 7.1) pg/mL, P = 0.001], but comparable with sex, age, and estimated glomerular filtration rate (eGFR) grade-matched IgAN patients. Serum creatinine (P = 0.006) and serum cystatin C (P = 0.001) were positively correlated with serum TNF-α level, while albumin (P = 0.014) and eGFR (P = 0.021) were negatively correlated with serum TNF-α level. Multivariate linear regression analysis revealed that eGFR (P = 0.007) was an independent clinical predictor of serum TNF-α. Patients with higher pathological classification grade also had higher serum TNF-α.

Conclusions

Serum TNF-α is associated with renal function and the pathological classification of adult patients with IgAV-N. TNF-α is a potential biomarker for the assessment of IgAV-N severity.

IgA Nephropathy Associated with Trifluridine/Tipiracil: A Case Report

Kidney diseases during chemotherapy treatment are variable, with different manifestations depending on the drugs used. Trifluridine/tipiracil is a treatment used in refractory metastatic digestive cancers. Its renal toxicity is poorly described. We report here the onset of a severe IgA nephropathy requiring hemodialysis which occurred several weeks after trifluridine/tipiracil treatment.

A cross-sectional analysis of clinicopathologic similarities and differences between Henoch-Schönlein purpura nephritis and IgA nephropathy

Introduction

Recent studies noted that Henoch-Schönlein purpura nephritis (HSPN) and IgA nephropathy (IgAN) share the feature of galactose-deficient IgA1 (Gd-IgA1)-oriented pathogenesis, although there are distinct clinical differences. We aimed to clarify the clinicopathologic differences between these 2 diseases.

Methods

We cross-sectionally analyzed adult patients with HSPN (n = 24) or IgAN (n = 56) who underwent renal biopsy (RB) between 2008 and 2018 at Showa University Hospital. Serum Gd-IgA1 (s-Gd-IgA1) levels at the time of RB were compared among study groups using enzyme-linked immunosorbent assay (ELISA) with anti-human Gd-IgA1-specific monoclonal antibody (KM55). We also immunohistochemically stained paraffin-embedded sections for glomerular Gd-IgA1 (g-Gd-IgA1)-deposition using KM55. Serum inflammatory cytokines were measured using ELISA.

Results

Glomerular endothelial injury with subendothelial IgA deposition was significant in patients with HSPN. Serum IL-8, MCP-1, TNF-α, and IL-6 levels were significantly higher in patients with HSPN than IgAN. Levels of s-Gd-IgA1 were comparable among patients with HSPN and IgAN, and a similar degree of g-Gd-IgA1-deposition was detected in both diseases. Furthermore, g-Gd-IgA1-deposition was evident in patients with histopathologically advanced HSPN or IgAN. In HSPN, significant positive correlations between s-Gd-IgA1 levels and crescent formation or IL-6 elevation were confirmed, and g-Gd-IgA1 intensity showed a significant positive correlation with MCP-1 and a tendency to positively correlate with IL-8. Meanwhile, patients with IgAN showed no correlation between inflammatory cytokines and both-Gd-IgA1. Moreover, most g-Gd-IgA1-positive areas were not double stained with CD31 in HSPN.

Conclusions

Although assessing both-Gd-IgA1 alone was insufficient to distinguish between HSPN and IgAN, patients with HSPN showed considerable glomerular capillaritis with subendothelial IgA deposition and significant elevation of serum inflammatory cytokines. Furthermore, such glomerular subendothelial IgA deposition might not contain Gd-IgA1, and factors associated with Gd-IgA1 were inconsistent among these 2 diseases. Thus, developmental mechanisms for IgAN might not apply to HSPN completely, and these 2 diseases still have different aspects.

Understanding Fc Receptor Involvement in Inflammatory Diseases: From Mechanisms to New Therapeutic Tools

Fc receptors (FcRs) belong to the ITAM-associated receptor family. FcRs control the humoral and innate immunity which are essential for appropriate responses to infections and prevention of chronic inflammation or auto-immune diseases. Following their crosslinking by immune complexes, FcRs play various roles such as modulation of the immune response by released cytokines or of phagocytosis. Here, we review FcR involvement in pathologies leading notably to altered intracellular signaling with functionally relevant consequences to the host, and targeting of Fc receptors as therapeutic approaches. Special emphasis will be given to some FcRs, such as the FcαRI, the FcγRIIA and the FcγRIIIA, which behave like the ancient god Janus depending on the ITAM motif to inhibit or activate immune responses depending on their targeting by monomeric/dimeric immunoglobulins or by immune complexes. This ITAM duality has been recently defined as inhibitory or activating ITAM (ITAMi or ITAMa) which are controlled by Src family kinases. Involvement of various ITAM-bearing FcRs observed during infectious or autoimmune diseases is associated with allelic variants, changes in ligand binding ability responsible for host defense perturbation. During auto-immune diseases such as rheumatoid arthritis, lupus or immune thrombocytopenia, the autoantibodies and immune complexes lead to inflammation through FcR aggregation. We will discuss the role of FcRs in autoimmune diseases, and focus on novel approaches to target FcRs for resolution of antibody-mediated autoimmunity. We will finally also discuss the down-regulation of FcR functionality as a therapeutic approach for autoimmune diseases.

IgA and FcαRI: Pathological Roles and Therapeutic Opportunities

Immunoglobulin A (IgA) is the most abundant antibody class present at mucosal surfaces. The production of IgA exceeds the production of all other antibodies combined, supporting its prominent role in host-pathogen defense. IgA closely interacts with the intestinal microbiota to enhance its diversity, and IgA has a passive protective role via immune exclusion. Additionally, inhibitory ITAMi signaling via the IgA Fc receptor (FcαRI; CD89) by monomeric IgA may play a role in maintaining homeostatic conditions. By contrast, IgA immune complexes (e.g., opsonized pathogens) potently activate immune cells via cross-linking FcαRI, thereby inducing pro-inflammatory responses resulting in elimination of pathogens. The importance of IgA in removal of pathogens is emphasized by the fact that several pathogens developed mechanisms to break down IgA or evade FcαRI-mediated activation of immune cells. Augmented or aberrant presence of IgA immune complexes can result in excessive neutrophil activation, potentially leading to severe tissue damage in multiple inflammatory, or autoimmune diseases. Influencing IgA or FcαRI-mediated functions therefore provides several therapeutic possibilities. On the one hand (passive) IgA vaccination strategies can be developed for protection against infections. Furthermore, IgA monoclonal antibodies that are directed against tumor antigens may be effective as cancer treatment. On the other hand, induction of ITAMi signaling via FcαRI may reduce allergy or inflammation, whereas blocking FcαRI with monoclonal antibodies, or peptides may resolve IgA-induced tissue damage. In this review both (patho)physiological roles as well as therapeutic possibilities of the IgA-FcαRI axis are addressed.

Recruitment of CXCR3+ T cells into injured tissues in adult IgA vasculitis patients correlates with disease activity

OBJECTIVES

Adult immunoglobulin A vasculitis (IgAV) is an immune complex small vessel vasculitis. So far, the involvement of T cells in this pathology has been poorly studied. The aim of this study was to analyze T-cell homeostasis as well as cytokine and chemokine concentrations in the blood and tissues of IgAV patients.

METHODS

T cells, cytokine and chemokine concentrations were analyzed in peripheral blood using flow cytometry and multiplex assays. T-cell infiltrates in the kidney and the skin were characterized by immunohistochemistry. This study prospectively included 44 adult patients with biopsy-proven IgAV and 24 age- and sex-matched healthy controls.

RESULTS

We observed reduced proportions of circulating CXCR5-and CXCR3-expressing memory CD4 T cells at diagnosis but normal values at remission. The plasma levels of Th1-related cytokines (IL-12, IL-27 and IFNγ) and of the TFH-related cytokine, IL-21, were paradoxically not reduced in patients. We observed increased plasma concentrations of the CXCR5 ligand, CXCL13, and of the CXCR3 ligands, CXCL10/11, suggesting a potential relocation of the corresponding T cells into inflamed tissues. We then confirmed the recruitment of CXCR3-expressing T cells into the skin and kidneys. In the skin, T-cell infiltrates mainly co-localized with damaged dermal small vessels. Finally, patients with the largest kidney T-cell infiltrates were also those with the highest proteinuria.

CONCLUSION

Altogether, our results strongly suggest that, in IgAV patients, CXCL10/11 orchestrate the recruitment of CXCR3-expressing T cells in injured tissues, contributing to tissue damage and disease activity.

Clinical significance of serum and mesangial galactose-deficient IgA1 in patients with IgA nephropathy

Introduction

Galactose-deficient IgA1 (Gd-IgA1) is a critical pathogenic factor for IgA nephropathy (IgAN), but its value as a disease-specific biomarker remains controversial. We aimed to clarify the clinical significance of Gd-IgA1 in patients with IgAN.

Methods

We retrospectively reviewed 111 patients who were diagnosed with IgAN based on the findings of renal biopsies (RB) at Showa University Hospital since 2007. Serum Gd-IgA1 (s-Gd-IgA1) at the time of RB was compared among 111 IgAN patients, 18 Henoch-Schönlein purpura nephritis (HSPN) patients, 29 lupus nephritis (LN) patients, 28 ANCA-associated vasculitis (AAV) patients, and 13 minimal change disease (MCD) patients using ELISA with an anti-human Gd-IgA1-specific monoclonal antibody (KM55). We also immunohistochemically stained paraffin-embedded sections for mesangial Gd-IgA1 (m-Gd-IgA1) deposition using KM55.

Results

Although levels of s-Gd-IgA1 were comparable among IgAN and HSPN, s-Gd-IgA1 levels were significantly elevated in patients with IgAN compared with LN, AAV and MCD (IgAN vs. HSPN, LN, AAV, and MCD: 16.2 ± 9.1 vs. 14.2 ± 10.8, p = 0.263; 12.7 ± 9.4, p = 0.008; 13.1 ± 7.3, p = 0.059; and 8.2 ± 4.8 μg/mL, p<0.001, respectively). Mesangial-Gd-IgA1 deposition was specifically detected in IgAN or HSPN. The increase in s-Gd-IgA1 significantly correlated with m-Gd-IgA1 positivity in patients with IgAN, and s-Gd-IgA1 elevation and m-Gd-IgA1 deposition were evident in patients with histopathologically advanced IgAN. Moreover, s-Gd-IgA1 levels were significantly higher in IgAN patients with glomerular sclerosis and tubulo-interstitial lesions. Mesangial-Gd-IgA1 intensity negatively correlated with eGFR in IgAN. Multivariate analysis selected s-Gd-IgA1 elevation as a significant risk factor for a 30%-reduction in eGFR in IgAN (HR, 1.37; 95% CI, 1.02–1.89; p = 0.038).

Conclusions

Although IgAN and HSPN remain difficult to differentiate, s-Gd-IgA1 elevation and m-Gd-IgA1 deposition are reliable diagnostic factors that reflect IgAN severity. Serum-Gd-IgA1 could serve as a predictor of renal outcomes in IgAN. Thus, Gd-IgA1 could be significant biomarker for patients with IgAN.

Vasculitis Pathogenesis: Can We Talk About Precision Medicine?

Precision medicine is designing the medical care by taking into account the individual variability for each person. We have tried to address whether the existing data may guide precision medicine in primary systemic vasculitides (PSV). We have reviewed genome-wide association studies (GWAS) data, lessons from monogenic mimics of these diseases, and biomarker studies in immunoglobulin A vasculitis/Henoch–Schönlein purpura, Kawasaki disease, anti-neutrophil cytoplasmic antibody-associated vasculitis, polyarteritis nodosa (PAN), Takayasu arteritis, and Behçet’s disease (BD). GWAS provide insights about the pathogenesis of PSV while whole exome sequencing studies lead to discovery of monogenic vasculitides, phenotype of which could mimic other types of vasculitis such as PAN and BD. Monogenic vasculitides form a subgroup of vasculitis which are caused by single gene alterations and discovery of these diseases has enabled more specific therapies in these patients. With increasing number of studies on biomarkers, new targets for treatment appear and better and structured follow-up of PSV patients will become possible. Proteomics and metabolomics studies are required to better categorize our patients with PSV so that we can manage them appropriately and offer more targeted therapy.

Insight into inflammatory cell and cytokine profiles in adult IgA vasculitis

Immunoglobulin A vasculitis (IgAV) is an immune complex, small vessel vasculitis with dominant IgA deposits in vessel walls, predominantly affecting the pediatric population. However, adults frequently have more severe gastrointestinal tract (GIT) and renal involvements as compared to children. Our aim was to study serological and cellular biomarkers to support clinicians in their diagnosis and the course of IgAV in adult patients. This cross-sectional study included 62 adult IgAV patients and 53 healthy blood donors (HBDs). Demographic and clinical data, as well as routine laboratory tests, were meticulously analyzed. Serum levels of IL-1β, IL-2, IL-6, IL-8, IL-9, IL-10, IL-17A, IL-23, TNF-α and serum amyloid A (SAA) were measured. Percentages of neutrophils, lymphocytes, and monocytes with neutrophil expression of L-selectin and integrin αM were determined by flow cytometry. SAA (12-fold), IL-6 (3-fold), IL-8 (2-fold), and TNF-α (2-fold) were significantly elevated in sera of adult IgAV patients compared to HBDs. There was a 16% elevation in neutrophils in IgAV patients, with IgAV neutrophils showing significantly higher CD62L surface expression. IgAV patients with GIT involvement exhibited elevated numbers of leukocytes, neutrophils, and neutrophil/lymphocyte (NLR), but lower neutrophil CD11b expression, as compared to IgAV patients without GIT. IgAV patients exhibit a low-medium grade inflammatory, neutrophil-driven response. Patients with GIT can be distinguished by their elevated NLR.

Vascularite à IgA (purpura rhumatoïde) de l’adulte

La vascularite à IgA (VIgA), anciennement purpura rhumatoïde (PR), est une vascularite systémique des petits vaisseaux à dépôts d’immunoglobulines A (IgA). Elle est beaucoup plus fréquente chez l’enfant que chez l’adulte (150 à 200 pour 1). La prévalence du PR chez l’adulte n’est pas connue et son incidence est estimée à 1/million. La maladie de l’adulte semble en effet différer de celle de l’enfant par l’incidence et la gravité des manifestations cliniques. La VIgA est caractérisée par l’association d’un purpura vasculaire cutané à des signes articulaires et gastro-intestinaux. Une atteinte rénale s’associe parfois à ces signes. Il s’agit alors d’une glomérulonéphrite à dépôts mésangiaux d’IgA. Plus rarement des localisations neurologiques, pulmonaires, cardiaques ou urogénitales peuvent s’observer. Sa physiopathologie demeure inconnue, mais les IgA joueraient un rôle central. Lorsque la symptomatologie est peu sévère, seul un traitement symptomatique est conseillé. À l’opposé, dans les formes digestive ou rénale sévères, des traitements plus agressifs associant, le plus souvent, des corticostéroïdes à du cyclophosphamide ont été proposés. Leur efficacité est en cours d’évaluation. Le pronostic à court terme de la maladie dépend de la sévérité de l’atteinte digestive, et à long terme de la sévérité de l’atteinte rénale. Les études ayant un suivi suffisamment prolongé montrent qu’un tiers des malades adultes évoluent vers l’insuffisance rénale terminale.

IgA Vasculitis: Genetics and Clinical and Therapeutic Management

PURPOSE OF REVIEW

The purpose of the study is to perform an update on the current knowledge on genetics, clinical manifestations, and therapy in immunoglobulin A vasculitis (IgAV) (Henoch-Schönlein purpura).

RECENT FINDINGS

A strong genetic predisposition in individuals with IgAV was confirmed. It was due to the association with the HLA class II region that in people of European background is mainly related to HLA-DRB1*01 allele. Recent reports support the claim that kidney disease is more common in adults than in children with IgAV. The clinical spectrum and outcome of adults with IgAV depends on the age of onset. Relapses are not uncommon in IgAV. The presence of renal impairment or proteinuria excretion exceeding 1 g/24 h at the time of disease diagnosis and the degree of renal damage on the kidney biopsy are the best predictors of end-stage renal failure in adults with IgAV. The levels of urinary IgA at the onset of the disease may predict a poor renal outcome. The use of prednisone does not seem to prevent persistent kidney disease in children with IgAV. No additional benefit of adding cyclophosphamide to glucocorticoids in adults with IgAV was found. Rituximab seems to be a promising therapy in the management of adults with IgAV. In this overview, we focus on the genetics, clinical manifestations, and therapy of IgA vasculitis, emphasizing the main differences in the clinical expression of the disease between children and adults.

Biomarkers of IgA vasculitis nephritis in children

Henoch–Schönlein purpura is a systemic vasculitis characterized by IgA deposits, which target the skin, joints, and kidneys, among other organs. In children, prognosis is often good but little is known about biomarkers of pediatric nephritis. We hypothesized that biological markers, including cytokines, immunoglobulins, IgA-immune complexes, IgA glycosylation and neutrophil gelatinase-associated lipocalin (NGAL), may discriminate IgA vasculitis (IgAV) pediatric patients with renal involvement from those without renal involvement. Fifty children at the time of IgAV rash between 2010 and 2015 were prospectively enrolled and compared to 21 controls. All patients were assessed for clinical and biological parameters at the time of diagnosis, including the levels of cytokines, immunoglobulins, immune complexes, IgA glycosylation and NGAL in serum and urine. Among IgAV patients, 33 patients exhibited nephritis (IgAV-N) and 17 children were without nephritis (IgAV-woN). The serum level of galactose-deficient (Gd)-IgA1 (p<0.01) and the urinary concentrations of IgA, IgG, IgM, IL-6, IL-8, IL-10, IgA-IgG complexes and IgA-sCD89 complexes (p<0.001 for all) were higher in the IgAV-N patients than in the IgAV-woN patients. Among those markers, urinary IgA and IgM had the highest AUC (0.86 and 0.87 respectively, p<0.0001). This prospective cohort study furthers our understanding of the pathophysiology of IgAV. We identified biomarkers that are able to distinguish patients initially with or without nephritis. To conclude, serum Gd-IgA1 and urinary IgA, IgG, IgM, IL-6, IL-8, IL-10, and IgA-IgG and IgA-sCD89 complexes could identify IgAV pediatric patients with renal involvement at the time of diagnosis.