TLC immunostaining for detection of "antiphospholipid" antibodies

Determination of Thrombogenicity Levels of Various Antiphospholipid Antibodies by a Modified Thrombin Generation Assay in Patients with Suspected Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is a hypercoagulable state accompanied by the presence of heterogeneous antiphospholipid antibodies (aPL), which nonspecifically affect hemostasis by the presence of lupus anticoagulans (LA), anticardiolipin antibodies (aCL), antibodies against β2-glycoprotein-I (anti-β2GPI), but also non-criteria antibodies such as antibodies against β2-glycoprotein-I domain I (anti-DI), anti-phosphatidylserine/prothrombin (anti-PS/PT), anti-annexin V, and many others. The main target of the antibodies is the activated protein C (APC) system, the elimination of which can manifest itself as a thrombotic complication. The aim of this study was to determine the thrombogenicity of antibodies using a modified protein C-activated thrombin generation assay (TGA) on a group of 175 samples suspected of APS. TGA was measured with/without APC and the ratio of both measurements was evaluated (as for APC resistance), where a cut-off was calculated ≤4.5 (90th percentile) using 21 patients with heterozygous factor V Leiden mutation (FV Leiden heterozygous). Our study demonstrates the well-known fact that multiple positivity of different aPLs is a more severe risk for thrombosis than single positivity. Of the single antibody positivity, LA antibodies are the most serious (p value < 0.01), followed by aCL and their subgroup anti-DI (p value < 0.05). Non-criteria antibodies anti-annexin V and anti-PT/PS has a similar frequency occurrence of thrombogenicity as LA antibodies but without statistical significance or anti-β2GPI1 positivity. The modified TGA test can help us identify patients in all groups who are also at risk for recurrent thrombotic and pregnancy complications; thus, long-term prophylactic treatment is appropriate. For this reason, it is proving increasingly beneficial to include the determination antibodies in combination with modified TGA test.

"Non-criteria antiphospholipid antibodies": bridging the gap between seropositive and seronegative Antiphospholipid Syndrome

OBJECTIVE

We aimed to analyze the prevalence of non-criteria anti-phospholipid (aPL) antibodies and their role in the diagnosis, treatment and prognosis in a cohort of patients with clinical features consistent with a diagnosis of antiphospholipid syndrome (APS), but persistently negative for criteria aPL-anti-cardiolipin antibodies (aCL), anti-β2-glycoprotein I antibodies (aβ2-GPI), and lupus anticoagulant (LA) - named seronegative APS (SN-APS).

METHODS

Sera from SN-APS patients were tested for aCL by TLC-immunostaining, anti-vimentin/cardiolipin (aVim/CL) and anti-phosphatidylserine/prothrombin (anti-PS/PT) by ELISA. Control groups of our study were APS patients and healthy controls.

RESULTS

We enrolled 114 consecutive SN-APS patients, 69 (60.5%) resulted positive for at least one non-criteria test in two occasions 12 weeks apart. Among the persistently positive patients to these tests, 97% resulted positive for aCL by TLC-immunostaining, 52.3% for aVim/CL and 17.4% for aPS/PT. SN-APS patients with double positivity (aCL by TLC-immunostaining and aVim/CL) showed a likelihood positive ratio of 8 to present mixed thrombotic and obstetrical features. Among SN-APS patients tested positive, after the therapeutic changes, 3 cases of recurrent thrombosis were observed [median follow-up 41 months (IQR 39.5)]. Twenty pregnancies were recorded in 17 SN-APS patients after the detection of unconventional aPL and 12 of them (60%) experienced a good outcome under conventional treatment for APS.

CONCLUSIONS

This is the largest monocentric study demonstrating that aCL tested by TLC-immunostaining and aVim/CL can detect aPL positivity in SN-APS. It may encourage clinicians to monitoring and providing adequate targeted therapy, which improve SN-APS prognosis.

Current Promising Biomarkers and Methods in the Diagnostics of Antiphospholipid Syndrome: A Review

Antiphospholipid syndrome (APS) is a hypercoagulation condition associated with the incidence of heterogenic antiphospholipid antibodies (aPLs), which non-specifically affect hemostasis processes. APS is clinically manifested by recurrent arterial and venous thromboses and reproduction losses. The aPL antibodies, which may induce clinical manifestations of APS, include criteria antibodies anti-cardiolipin, anti-β2-glycoprotein-I, and lupus anticoagulant, but also non-criteria antibodies, for example anti-β2-glycoprotein-I domain I, anti-phosphatidylserine/prothrombin, anti-annexin V, and many others. APS occurs mostly in patients of younger and middle age, most frequently in females. Laboratory diagnostics of APS are quite difficult, as they include a wide spectrum of examining methods, which are based on various principles of detection and are performed using various laboratory techniques. The objective of the review is to describe the current state of potentially examined biomarkers and methods in APS diagnostics. The aforementioned biomarkers are lupus anticoagulant, anti-β2-glycoprotein-I, anti-cardiolipin, anti-β2-glycoprotein-I domain I, anti-phosphatidylserine/prothrombin, anti-β2-glycoprotein-I IgA, anti-cardiolipin IgA, anti-annexin V and II, anti-prothrombin, anti-cardiolipin/vimentin, anti-protein S/protein C, and antibodies against phospholipid antigens for whose diagnostics we may use some of the methods established for a long time and some of the modern methods—the coagulation method for the determination of lupus anticoagulant (LA), enzyme-linked imunosorbent assay (ELISA), chemiluminescence analysis (CLIA), multiplex fluorescence flow immunoassay (MFFIA), fluorescence enzyme immunoassay (EliA), line immunoassay (LIA), multiline dot assay (MLDA), and thin-layer chromatography (TLC). Conclusion: Antibodies against phosphatidylethanolamine, phosphatidic acid, phosphatidylserine, phosphatidylinositol, cardiolipin/vimentin complex, and annexin V are currently the most studied new markers. However, these assays have not been standardized until now, both from the laboratory and clinical point of view. In this review we summarize the evidence of the most studied aPL markers and their potential clinical significance in seronegative APS (SN-APS).

The Role of Cardiolipin as a Scaffold Mitochondrial Phospholipid in Autophagosome Formation: In Vitro Evidence

Cardiolipin (CL) is a hallmark phospholipid localized within the inner mitochondrial membrane. Upon several mitochondrial stress conditions, CL is translocated to specialized platforms, where it may play a role in signaling events to promote mitophagy and apoptosis. Recent studies characterized the molecular composition of MAM-associated lipid microdomains and their implications in regulating the autophagic process. In this study we analyzed the presence of CL within MAMs following autophagic stimulus and the possible implication of raft-like microdomains enriched in CL as a signaling platform in autophagosome formation. Human 2FTGH fibroblasts and SKNB-E-2 cells were stimulated under nutrient deprivation with HBSS. MAM fraction was obtained by an ultracentrifugation procedure and analyzed by HPTLC immunostaining. CL interactions with mitofusin2 (MFN2), calnexin (CANX) and AMBRA1 were analyzed by scanning confocal microscopy and coimmunoprecipitation. The analysis revealed that CL accumulates in MAMs fractions following autophagic stimulus, where it interacts with MFN2 and CANX. It associates with AMBRA1, which in turn interacts with BECN1 and WIPI1. This study demonstrates that CL is present in MAM fractions following autophagy triggering and interacts with the multimolecular complex (AMBRA1/BECN1/WIPI1) involved in autophagosome formation. It may have both structural and functional implications in the pathophysiology of neurodegenerative disease(s).

Molecular Mechanisms of "Antiphospholipid Antibodies" and Their Paradoxical Role in the Pathogenesis of "Seronegative APS"

Antiphospholipid Syndrome (APS) is an autoimmune disease characterized by arterial and/or venous thrombosis and/or pregnancy morbidity, associated with circulating antiphospholipid antibodies (aPL). In some cases, patients with a clinical profile indicative of APS (thrombosis, recurrent miscarriages or fetal loss), who are persistently negative for conventional laboratory diagnostic criteria, are classified as "seronegative" APS patients (SN-APS). Several findings suggest that aPL, which target phospholipids and/or phospholipid binding proteins, mainly β-glycoprotein I (β-GPI), may contribute to thrombotic diathesis by interfering with hemostasis. Despite the strong association between aPL and thrombosis, the exact pathogenic mechanisms underlying thrombotic events and pregnancy morbidity in APS have not yet been fully elucidated and multiple mechanisms may be involved. Furthermore, in many SN-APS patients, it is possible to demonstrate the presence of unconventional aPL ("non-criteria" aPL) or to detect aPL with alternative laboratory methods. These findings allowed the scientists to study the pathogenic mechanism of SN-APS. This review is focused on the evidence showing that these antibodies may play a functional role in the signal transduction pathway(s) leading to thrombosis and pregnancy morbidity in SN-APS. A better comprehension of the molecular mechanisms triggered by aPL may drive development of potential therapeutic strategies in APS patients.

[Seronegative antiphospholipid syndrome: Myth or reality?]

The antiphospholipid syndrome (APS) is a systemic autoimmune disease characterized by thrombosis and/or obstetrical manifestations and the persistent presence, at least 12 weeks apart, of antiphospholipid antibodies (aPL) such as lupus anticoagulant (LA) and/or anticardiolipin antibodies (ACL) and/or anti-β2 glycoprotein I antibodies (aβ2GPI). The finding of patients with clinical profile highly suggestive of APS but who are negative for conventional biological criteria has led to the concept of seronegative APS. In the last few years, new antigen targets and methodological approaches have been employed to more clearly identify this syndrome in patients with thrombosis or obstetrical complications without conventional aPL. Although seronegative APS is still controversial, there is increasing recognition of the existence of this subgroup. However, clinical relevance of non conventional aPL need to be confirmed by efforts toward standardizing new biological tools and longitudinal studies involving large cohort of patients.

"Non-criteria" antiphospholipid antibodies add value to antiphospholipid syndrome diagnoses in a large Chinese cohort

BACKGROUND

Despite expansion in the 2006 Sydney antiphospholipid syndrome (APS) classification criteria to include IgG/IgM anti-β2-glycoprotein (aβ2GPI) antibodies in addition to IgG/IgM anti-cardiolipin antibodies (aCL) and lupus anticoagulant (LAC), some individuals with clinical features of APS remain seronegative (seronegative APS or SNAPS) and are at risk of recurrent thrombosis and pregnancy morbidities. Our aim was to assess the value of "non-criteria" aPL antibodies to detect these SNAPS patients.

METHODS

One hundred ninety-two APS patients, 90 SNAPS patients, 193 autoimmune disease controls, and 120 healthy controls were evaluated. Ten antiphospholipid antibodies (aPLs) were tested using commercial kits, including 5 non-criteria aPLs: anti-phosphatidylserine/prothrombin antibodies (aPS/PT) IgG/IgM, aCL IgA, aβ2GPI IgA, and anti-β2GPI Domain 1 (aβ2GPI-D1) IgG.

RESULTS

Up to 60.9% of the SNAPS and 93.5% of APS patients were detected by at least one non-criteria aPL. aPS/PT IgG had the highest Youden index in classifying APS and SNAPS from controls. aPS/PT IgG and aβ2GPI Domain 1 IgG seem to be the most significant risk factors for thrombotic events and pregnancy morbidity, respectively. aPS/PT IgG/IgM and aβ2GPI-D1 IgG were detected in some SNAPS patients, while IgA isotypes of aCL/aβ2GPI tended to appear together with other biomarkers. The combined analysis showed enhanced diagnostic performance with the inclusion of non-criteria aPLs.

CONCLUSIONS

Recognition of SNAPS patients is critical for clinical management and prevention of potential thrombotic and obstetric adverse events. The non-criteria antiphospholipid antibodies help to identify a considerable portion (60.9%) of these patients who otherwise may remain untreated and at clinical risk.

Does seronegative obstetric APS exist? "pro" and "cons"

Antiphospholipid Syndrome (APS) is the commonest treatable cause of recurrent miscarriage and pharmacological treatment of pregnant patients with antiphospholipid antibodies (aPL) should aim at preventing obstetric complications and maternal thrombotic events. Conventional treatment for patients with an established diagnosis of obstetric APS (OAPS), generally resulting in over 70-80% successful pregnancies. Since seropositive (SP)-APS and seronegative (SN)-APS patients had shown similar clinical profiles, patients with SN- OAPS, as well as SP-OAPS, should receive combined treatment in order to improve the pregnancy prognosis; indeed, current standard of care increased good pregnancy outcome in SN-APS, with similar effect to confirmed APS. The above data suggest that there are patients with the clinical manifestations of OAPS but persistently negative to conventional aPL that need to be identified to ensure adequate therapy and therefore a better prognosis. The clinical utility of non-criteria aPL in the diagnosis of SN-APS is still a matter of debate. In the last decade more and more studies have reported the presence of patients suffering from SN-APS in which non-conventional ("non-criteria") aPL might be present or antibodies may be detected using methodological approaches different from the traditional assays. To improve test standardization large prospective, multicenter, and multinational studies are needed. Therefore, when assessing a patient with clinical manifestations consistent with OAPS but aPL negative using the conventional available assays, the clinician should consider the possibility that the patient is affected with SN-APS.

Autoantibodies as Diagnostic Tools

Autoimmune diseases are very diverse and include many common diseases of unknown etiology.Diagnosis can be challenging but can be facilitated by the identification of characteristic autoantibodies (AuAbs), which are present in varying frequencies. Identification of such AuAbs requires a range of different techniques, depending on the autoantigens in question. Each individual AuAb assay is characterized by analytical sensitivity and specificity, which in turn determines clinical sensitivity and specificity in relation to diseases. Clinical sensitivities and specificities vary much, but many AuAb analyses can be of significant help in establishing correct diagnoses. It remains unsettled whether AuAbs are generally pathogenic, but it is generally agreed that autoimmune diseases are caused by a combination of genetic and environmental factors, and that early and correct diagnosis facilitates treatment.

A Monocentric Cohort of Obstetric Seronegative Anti-Phospholipid Syndrome

The present study was conducted to diagnose obstetric anti-phospholipid syndrome (OAPS) in patients with clinical signs suggestive of anti-phospholipid syndrome (APS), but persistently negative for conventional anti-phospholipid antibodies (aPL). Sera from 61 obstetrical seronegative APS (SN-APS) patients were analyzed for anti-cardiolipin antibodies (aCL) using thin-layer chromatography (TLC)-immunostaining, for anti-cardiolipin/vimentin antibodies (aCL/Vim), anti-phosphatidylserine/prothrombin antibodies, IgA anti-β₂glycoprotein I antibodies (aβ₂GPI), and IgA aCL antibodies by enzyme-linked immunosorbent assay. Taken together, our findings show that in 50 out of 61 SN-APS (81.9%) at least one aPL/cofactor antibody was detected using the assays under test. Results revealed that 76% of SN-APS patients resulted positive for aCL by TLC-immunostaining, 54% for aCL/Vim, 12% for aPS/PT, 4% for IgA aβ₂GPI, and 2% for IgA aCL. Thirty-five out of 61 patients were followed up and the tests were repeated on two occasions, at least 12 weeks apart. Twenty-six out of 35 SN-APS (74.3%) were positive at least one non-conventional test; only 2 patients (5.7%) did not confirm the positivity to the second test. These findings suggest that non-conventional tests, mainly aCL/Vim and aCL detected by TLC-immunostaining, seem to be the most sensitive approaches for finding out aPL in patients with obstetric SN-APS. The use of these tests can be useful for accurate and timely diagnosis of patients with obstetrical APS who are negative for conventional laboratory criteria markers.

Diagnosing antiphospholipid syndrome: 'extra-criteria' manifestations and technical advances

First described in the early 1980s, antiphospholipid syndrome (APS) is a unique form of acquired autoimmune thrombophilia in which patients present with clinical features of recurrent thrombosis and pregnancy morbidity and persistently test positive for the presence of antiphospholipid antibodies (aPL). At least one clinical (vascular thrombosis or pregnancy morbidity) and one lab-based (positive test result for lupus anticoagulant, anticardiolipin antibodies and/or anti-β2-glycoprotein 1 antibodies) criterion have to be met for a patient to be classified as having APS. However, the clinical spectrum of APS encompasses additional manifestations that can affect many organs and cannot be explained exclusively by patients being in a prothrombotic state; clinical manifestations not listed in the classification criteria (known as extra-criteria manifestations) include neurologic manifestations (chorea, myelitis and migraine), haematologic manifestations (thrombocytopenia and haemolytic anaemia), livedo reticularis, nephropathy and valvular heart disease. Increasingly, research interest has focused on the development of novel assays that might be more specific for APS than the current aPL tests. This Review focuses on the current classification criteria for APS, presenting the role of extra-criteria manifestations and lab-based tests. Diagnostic approaches to difficult cases, including so-called seronegative APS, are also discussed.

Coupling of In Vitro Bioassays with Planar Chromatography in Effect-Directed Analysis

Modern analytical test methods increasingly detect anthropogenic organic substances and their transformation products in water samples and in the environment. The presence of these compounds might pose a risk to the aquatic environment. To determine a possible (eco)toxicological risk, aquatic samples are tested using various bioassays, including sub-organismic assays such as the luminescent bacteria inhibition test, the acetylcholinesterase inhibition test, and the umu-test. The effect-directed analysis (EDA) combines physicochemical separation methods with biological (in vitro) tests. High-performance thin-layer chromatography (HPTLC) has proved to be particularly well suited for the separation of organic compounds and the subsequent analysis of effects by the application of the biotests directly on the surface of the HPTLC plate. The advantage of using HPTLC in comparison to high-performance liquid chromatography (HPLC) for EDA is that the solvent which is used as a mobile phase during chromatography is completely evaporated after the separation and therefore can no longer influence the applied bioassays.A prioritization during the complex identification process can be achieved when observed effects are associated with the separated zones in HPTLC. This increases the probability of identifying the substance responsible for an adverse effect from the multitude of organic trace substances in environmental samples. Furthermore, by comparing the pattern of biological effects of a separated sample, it is possible to track and assess changes in biological activity over time, over space, or in the course of a process, even without identifying the substance. HPTLC has already been coupled with various bioassays.Because HPTLC is a very flexible system, various detection techniques can be used and combined. In addition to the UV/Vis absorption and fluorescence measurements, TLC can also be coupled with a mass spectrometer (MS) for compound identification. In addition, detection of functional groups by means of derivatization reagents can support this identification. It is also possible to combine derivatization and HPLC-MS.Two case studies are used to illustrate the significance of HPTLC-EDA in investigating water quality: Study on a wastewater treatment plant Possible influence of an artificial turf surface on ground water.

"New" antigenic targets and methodological approaches for refining laboratory diagnosis of antiphospholipid syndrome

Antiphospholipid antibodies (aPLs) are a heterogeneous group of antibodies directed against phospholipids or protein/phospholipid complexes. Currently, aPLs are assessed using either "solid-phase" assays that identify anticardiolipin antibodies and anti-β2-glycoprotein I antibodies or "liquid-phase" assay that identifies lupus anticoagulant. However, in the last few years, "new" antigenic targets and methodological approaches have been employed for refining laboratory diagnosis of antiphospholipid syndrome (APS). In this review the potential diagnostic value of antibodies to domains of β2-GPI, prothrombin/phosphatidylserine, vimentin/cardiolipin, protein S, protein C, annexin A2, annexin A5, and phospholipid antigens is discussed. Moreover, new technical approaches, including chemiluminescence, multiline dot assay, and thin layer chromatography (TLC) immunostaining, which utilize different supports for detection of aPL, have been developed. A special focus has been dedicated on "seronegative" APS, that is, those patients with a clinical profile suggestive of APS (thromboses, recurrent miscarriages, or foetal loss), who are persistently negative for the routinely used aPL. Recent findings suggest that, in sera from patients with SN-APS, antibodies may be detected using "new" antigenic targets (mainly vimentin/cardiolipin) or methodological approaches different from traditional techniques (TLC immunostaining). Thus, APS represents a mosaic, in which antibodies against different antigenic targets may be detected thanks to the continuously evolving new technologies.