Vasculitis of small blood vessels - some riddles about IgA and about the complexity of transmigration

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.

Infection Rates Before and After Diagnosis of IgA Vasculitis in Childhood: A Population-wide Study Using Non-exposed Matched Controls

OBJECTIVE

Clinical data suggest that infections can trigger IgA vasculitis (IgAV), but longterm observations are lacking. We compared rates, types, and microorganisms for serious infection before and after diagnosis for children with IgAV and non-exposed controls.

METHODS

Using population-based administrative linked health datasets we estimated incidence rates (IR) for serious infection per 1000 person-months for patients with IgAV (n = 504, age 5 yrs, 59.1% males) and controls matched for age, sex, and year of presentation (n = 1281, age 6 yrs, 66% males). Time zero (T0) was the date of IgAV diagnosis or equivalent date in controls, lookback (median 38 mos) was the period prior to T0, and followup (median 239 mos) was the period after T0.

RESULTS

During lookback, prevalence of serious infection was similar in patients with IgAV and controls (11.5% vs 9.5%, respectively), but patients with IgAV had a higher rate of upper respiratory tract infections [incidence rate ratio (IRR) 1.79; 95% CI 1.39-2.31] with shorter time between first serious infection and T0 (27 vs 43 mos; p = 0.02). During followup, patients were at a constant increased risk for serious infections (IRR 1.46, 95% CI 1.35-1.58). These rates were higher during followup: sepsis (IRR 12.6), pneumonia (IRR 6.19), upper respiratory tract infections (IRR 2.36), and skin infections (IRR 1.85). There was little overlap between patients with serious infections in the lookback and followup periods.

CONCLUSION

In patients with childhood IgAV there is an increased longterm risk for a broader spectrum of infections, which is unrelated to serious infections prior to diagnosis or treatment. This suggests disease-specific factors may have a lasting effect on immune competence in childhood IgAV.

Dapsone as a potential treatment option for Henoch-Schönlein Purpura (HSP)

Henoch-Schönlein Purpura (HSP, IgA vasculitis) is an immunoglobulin A (IgA) mediated disorder characterized by systemic vasculitis with variable presentation, frequently affecting the skin, mucous membrane, joints, kidneys, and rarely lungs and the central nervous system. Interestingly, enhanced production of interleukin-8 (IL-8) levels are found during active disease and increased levels have been reported in supernatants from human umbilical venous endothelial cells after stimulation with sera from patients affected by HSP. While corticosteroid therapy is currently the recommended treatment for HSP, dapsone, an anti-leprosy agent, has also recently been suggested to have therapeutic efficacy due to its ability to suppress IL-8. Moreover, in addition to IL-8 suppression, dapsone has been reported to exert various anti-inflammatory effects by inhibiting the generation of toxic free radicals, myeloperoxidase mediated halogenation that converts H₂O₂ to HOCl, leukocyte chemotaxis, production of tumor necrosis factor, and other anti-inflammatory molecules. This review aims to provide a solid hypothesis for the pathogenesis of vasculitis in HSP. Moreover, we highlight potential mechanistic actions of dapsone in hopes that dapsone may be considered as an alternative viable treatment for patients affected by HSP.

Neutrophils Self-Regulate Immune Complex-Mediated Cutaneous Inflammation through CXCL2

Deposition of immune complexes (ICs) in tissues triggers acute inflammatory pathology characterized by massive neutrophil influx leading to edema and hemorrhage, and is especially associated with vasculitis of the skin, but the mechanisms that regulate this type III hypersensitivity process remain poorly understood. Here, using a combination of multiphoton intravital microscopy and genomic approaches, we re-examined the cutaneous reverse passive Arthus reaction and observed that IC-activated neutrophils underwent transmigration, triggered further IC formation, and transported these ICs into the interstitium, whereas neutrophil depletion drastically reduced IC formation and ameliorated vascular leakage in vivo. Thereafter, we show that these neutrophils expressed high levels of CXCL2, which further amplified neutrophil recruitment and activation in an autocrine and/or paracrine manner. Notably, CXCL1 expression was restricted to tissue-resident cell types, but IC-activated neutrophils may also indirectly, via soluble factors, modulate macrophage CXCL1 expression. Consistent with their distinct cellular origins and localization, only neutralization of CXCL2 but not CXCL1 in the interstitium effectively reduced neutrophil recruitment. In summary, our study establishes that neutrophils are able to self-regulate their own recruitment and responses during IC-mediated inflammation through a CXCL2-driven feed forward loop.

Detection of circulating immune complexes of human IgA and beta 2 glycoprotein I in patients with antiphospholipid syndrome symptomatology

BACKGROUND

Patients with antiphospholipid syndrome (APS) have a hypercoagulable condition associated with the presence of antiphospholipid autoantibodies (aPL). Consensus antibodies for diagnosis are lupus anticoagulant, anti-beta2 glycoprotein I (B2GPI) and anticardiolipin (IgG or IgM). Circulating immunocomplexes (CIC) of B2GPI associated with IgM or IgG were reported. Isolated IgA aB2GPI antibodies have achieved high diagnostic value although specific CIC of B2GPI bounded to IgA (B2A-CIC) has still not been described. CIC detection assays are mainly based on interaction with complement and are not appropriate to detect B2A-CIC because IgA does not fix complement using the classical pathway.

PATIENTS AND METHODS

Sera from healthy blood donors (N= 247) and from patients with thrombosis background and isolate positive for IgA aB2GPI (N = 68) were studied in a case-control study. Two methods were applied, these being a capture ELISA to quantify specific B2A-CIC and quantification of total IgA anti-B2GPI after dissociating CIC.

RESULTS

B2A-CIC values in APS-patients were 19.27 ± 2.6 AU vs 6.1 ± 0.4 AU in blood donors (p < 0.001). There were 36.4% B2A-CIC positive patients (cutoff 21 AU) versus 5.5% in blood donors (p < 0.001). Dissociated IgA aB2GPI levels (total IgA aB2GPI) were 146.8 ± 10.8 IU/mL in patients vs. 22.4 IU/mL in controls (p < 0.001). B2A-CIC was independent of B2GPI and autoantibodies IgA aB2GPI serum levels.

CONCLUSION

B2A-CIC can be identified and quantified in an easy and reproducible manner using two complement-independent methods. The use of these tests in prospective studies will allow better understanding of the prognosis and outcome of patients.

Serum cytokine profiles associated with specific adjuvants used in a DNA prime-protein boost vaccination strategy

In recent years, heterologous prime-boost vaccines have been demonstrated to be an effective strategy for generating protective immunity, consisting of both humoral and cell-mediated immune responses against a variety of pathogens including HIV-1. Previous reports of preclinical and clinical studies have shown the enhanced immunogenicity of viral vector or DNA vaccination followed by heterologous protein boost, compared to using either prime or boost components alone. With such approaches, the selection of an adjuvant for inclusion in the protein boost component is expected to impact the immunogenicity and safety of a vaccine. In this study, we examined in a mouse model the serum cytokine and chemokine profiles for several candidate adjuvants: QS-21, Al(OH)3, monophosphoryl lipid A (MPLA) and ISCOMATRIX™ adjuvant, in the context of a previously tested pentavalent HIV-1 Env DNA prime-protein boost formulation, DP6-001. Our data revealed that the candidate adjuvants in the context of the DP6-001 formulation are characterized by unique serum cytokine and chemokine profiles. Such information will provide valuable guidance in the selection of an adjuvant for future AIDS vaccine development, with the ultimate goal of enhancing immunogenicity while minimizing reactogenicity associated with the use of an adjuvant. More significantly, results reported here will add to the knowledge on how to include an adjuvant in the context of a heterologous prime-protein boost vaccination strategy in general.

[Skin manifestations of different forms of vasculitis]

The skin not only represents the organ which often reveals the first signs of systemic vasculitis, but also the organ which is most frequently involved in vasculitis. These diseases encompass systemic vasculitides and those which appear to involve the skin only. Among those vasculitides restricted to the skin, some are yet typically associated with other systemic diseases, such as nodular vasculitis, which often occurs during infections by M. tuberculosis, or erythema elevatum diutinum in patients with gammopathy. The type and localization of skin lesions give valuable indications as to the type of vasculitis. Subcutaneous nodules which ulcerate and are surrounded by livedo racemosa are suggestive of polyarteritis nodosa, a palpable purpura with predilection for the lower legs is almost pathognomonic for immune complex vasculitis (e.g. IgA vasculitis or cutaneous leukocytoclastic vasculitis), hemorrhagic papules and necrotic plaques which occur in acral areas after cooling indicate cryoglobulinemic vasculitis, hemorrhagic papules and macules which develop in patients who start to feel worse and develop fever should arouse suspicion of septic vasulitis, while the simultaneous presence of ulcerating nodules and hemorrhagic papules without predilection for the lower legs will suggest ANCA-associated vasculitis. The different morphology of the cutaneous signs of the various vasculitides depends to a large extent on the size of the vessels primarily involved. In this review the cutaneous signs of vasculitides will be presented with reference to the revised nomenclature of the Chapel Hill Consensus Conference from 2012.

α-1-Antitrypsin and IFN-γ reduce the severity of IC-mediated vasculitis by regulation of leukocyte recruitment in vivo

IC-mediated vasculitis (ICV) can be life threatening. The cellular and immune mechanisms controlling ICV are poorly understood. Therefore, we investigated the role of α-1-antitrypsin (α1AT) and IFN-γ in reducing the severity of ICV in a mouse model in vivo. To induce ICV, mice were challenged with the reverse passive Arthus reaction (RPA), the prototypic in vivo model for leukocytoclastic vasculitis (LcV), and the modulation of vascular permeability, edema formation, and leukocyte recruitment was studied. To further analyze the dynamics of RPA, we applied intravital microscopy in the dorsal skinfold chamber. α1AT continuously led to reduced leukocyte recruitment. α1AT interfered with neutrophil recruitment through a KC-dependent mechanism and reduced KC-elicited neutrophil activation. In contrast to α1AT, IFN-γ-reduced leukocyte recruitment during RPA was clearly independent of KC. We also revealed that the recruitment of neutrophils during RPA was a prerequisite for full KC expression. Thus, therapeutic administration of α1AT and IFN-γ might be beneficial for limiting the duration and severity of ICV.

[Cutaneous vasculitis]

Vasculitis is a term that refers to damage and inflammation of the walls of blood vessels of any size. The classification of types of cutaneous vasculitis continues to be a challenge, probably because of our lack of understanding of the etiology and pathogenesis of this condition. Changes in the vessel wall will be visible on microscopy and will enable the different clinical forms to be distinguished according to the caliber of affected vessels, the type of cell that predominates in the inflammatory infiltrate, or the presence of such key findings as extravascular granulomas. Skin manifestations (macules, papules, nodules, livedo reticularis, etc) correlate with the size of the vessel affected. The prognosis in cases of vasculitis with skin involvement will be determined by the presence or absence of extracutaneous disease. Systemic vasculitis shows a predilection for certain organs, such as the kidney or lung. The introduction of immunosuppressant drug treatments has led to evident improvement in survival rates for patients with vasculitis. This review covers practical aspects of the pathophysiology, histopathology, treatment, and differential diagnosis of the main clinical presentations of vasculitis with cutaneous involvement.