Serum amyloid P component levels are not decreased in patients with systemic lupus erythematosus and do not rise during an acute phase reaction

Successful Development of Nonclinical Anti-Drug Antibody Assays to Support Zinpentraxin Alfa Reproductive Toxicology Studies

Immunogenicity assessment is an essential part of biotherapeutic drug development. While the immune response in animals is not always representative of the human immune response, immunogenicity data obtained in animal models is still informative for the evaluation of drug exposure and safety. The most common assay format used for the detection of anti-drug antibodies (ADAs) in preclinical and clinical studies is the bridging format. The advantage of this method is that it can detect all antibody isotypes generated against the therapeutic. However, the method development can be time-consuming and labor-intensive, due to the need for labeling of the drug which is used both as capture and detection. Various generic ADA assays have been successfully implemented to overcome these disadvantages and to enable faster assay development timelines to support nonclinical toxicology studies. Here, we describe the challenges in the development of an assay to detect antibodies to zinpentraxin alfa, a recombinant human pentraxin-2, in rabbit and rat toxicology studies. Our initial efforts to develop a bridging assay failed, prompting us to develop a method adapted from generic assay formats to detect anti-zinpentraxin alfa antibodies in the serum of different species with minimal optimization. However, while the general assay format remained similar, assay reagents were adapted between the different species, resulting in the development of two distinct assays for the detection of ADAs in rat and rabbit. Here, we share the final development/validation data and the immunogenicity study results. Our work highlights the need for the evaluation of alternate assay formats when evaluating novel drug modalities.

Complementary Roles of Short and Long Pentraxins in the Complement-Mediated Immune Response to Aspergillus fumigatus Infections

The ubiquitous mold Aspergillus fumigatus is the major etiologic agent of invasive aspergillosis, a life-threatening infection amongst immune compromised individuals. An increasing body of evidence indicates that effective disposal of A. fumigatus requires the coordinate action of both cellular and humoral components of the innate immune system. Early recognition of the fungal pathogen, in particular, is mediated by a set of diverse soluble pattern recognition molecules (PRMs) that act as "ancestral antibodies" inasmuch as they are endowed with opsonic, pro-phagocytic and killing properties. Pivotal is, in this respect, the contribution of the complement system, which functionally cooperates with cell-borne pattern recognition receptors (PRRs) and other soluble PRMs, including pentraxins. Indeed, complement and pentraxins form an integrated system with crosstalk, synergism, and regulation, which stands as a paradigm of the interplay between PRMs in the mounting and orchestration of antifungal immunity. Following upon our past experience with the long pentraxin PTX3, a well-established immune effector in the host response to A. fumigatus, we recently reported that this fungal pathogen is targeted in vitro and in vivo by the short pentraxin Serum Amyloid P component (SAP) too. Similar to PTX3, SAP promotes phagocytosis and disposal of the fungal pathogen via complement-dependent pathways. However, the two proteins exploit different mechanisms of complement activation and receptor-mediated phagocytosis, which further extends complexity and integration of the complement-pentraxin crosstalk in the immune response to A. fumigatus. Here we revisit this crosstalk in light of the emerging roles of SAP as a novel PRM with antifungal activity.

Elevated Serum Amyloid a Levels Are not Specific for Sarcoidosis but Associate with a Fibrotic Pulmonary Phenotype

Elevated Serum Amyloid A (SAA) levels have been found in several inflammatory diseases, including sarcoidosis. SAA is suggested to be involved in sarcoidosis pathogenesis by involvement in granuloma formation and maintenance. We hypothesized that SAA serum levels would be higher in sarcoidosis compared to other non-infectious granulomatous and non-granulomatous diseases. SAA levels were measured in serum from sarcoidosis, Hypersensitivity pneumonitis (HP), and (eosinophilic) granulomatosis with polyangiitis ((E)GPA) patients. Idiopathic pulmonary fibrosis (IPF) patients were included as non-granulomatous disease group. SAA levels of patients with sarcoidosis (31.0 µg/mL), HP (23.4 µg/mL), (E)GPA (36.9 µg/mL), and IPF (22.1 µg/mL) were all higher than SAA levels of healthy controls (10.1 µg/mL). SAA levels did not differ between the diagnostic groups. When SAA serum levels were analyzed in sarcoidosis subgroups, fibrotic sarcoidosis patients showed higher SAA levels than sarcoidosis patients without fibrosis (47.8 µg/mL vs. 29.4 µg/mL, p = 0.005). To conclude, the observation that fibrotic sarcoidosis patients have higher SAA levels, together with our finding that SAA levels were also increased in IPF patients, suggests that SAA may next to granulomatous processes also reflect the process of fibrogenesis. Further studies should clarify the exact role of SAA in fibrosis and the underlying mechanisms involved.

Feasibility of a plasma bioassay to assess oxidative protection of low-density lipoproteins by high-density lipoproteins

BACKGROUND

Traditionally, the impact of lipoproteins on vascular disease has been evaluated in light of their quantity, that is, cholesterol content, in plasma. However, recent studies of high-density lipoproteins (HDLs) have focused on functionality with regard to atheroprotection. For example, bioassays have emerged to assess the ability of HDL, in its near native plasma environment, to promote cholesterol removal (efflux) from cells. As a result, attention has focused on developing plasma-based assays for other putative HDL protective functions including protecting low-density lipoproteins (LDLs) from oxidative damage.

OBJECTIVE

To determine the feasibility of such an assay in a complex sample such as plasma, we evaluated the contribution of HDL vs other plasma factors in preventing LDL oxidation.

METHODS

We separated normolipidemic human plasma by gel filtration chromatography and assessed each fraction for its ability to prevent LDL modification by water soluble radical and copper-initiated oxidation mechanisms.

RESULTS

Using proteomics and selective precipitation methods, we identified major antioxidative contributions for fibrinogen, immunoglobulin G, albumin, and small soluble molecules like uric acid and ascorbate, with albumin being especially dominant in copper-initiated mechanisms. HDL particles were minor contributors (∼1%-2%) to the antioxidant capacity of plasma, irrespective of oxidation mechanism.

CONCLUSIONS

Given the overwhelming background of antioxidant capacity inherent to highly abundant plasma proteins, specific bioassays of HDL antioxidative function will likely require its complete separation from plasma.

Amniotic fluid pentraxins: Potential early markers for identifying intra-amniotic inflammatory complications in preterm pre-labor rupture of membranes

In this study, pentraxin 3 (PTX3), C-reactive protein (CRP), and serum amyloid P component (SAP) concentrations in the amniotic fluid of women with preterm pre-labor rupture of membranes (PPROM) were evaluated based on evidence of microbial invasion of the amniotic cavity (MIAC), intra-amniotic inflammation (IAI), and microbial-associated IAI. A total of 149 women with PPROM were included in this study. Amniotic fluid samples were obtained by transabdominal amniocentesis. Amniotic fluid PTX3, SAP, and CRP concentrations were assessed using enzyme-linked immunosorbent assay. PTX3 and CRP concentrations were higher in women with MIAC, IAI, and microbial-associated IAI than in women without these conditions. SAP concentrations were only higher in the presence of IAI and microbial-associated IAI. Amniotic fluid PTX3 concentrations of 11 ng/mL were found to be the best value for identifying the presence of microbial-associated IAI and IAI in women with PPROM. To conclude, amniotic fluid pentraxins are involved in intra-amniotic inflammatory responses in pregnancies complicated by PPROM.

The pentraxins PTX3 and SAP in innate immunity, regulation of inflammation and tissue remodelling

Pentraxins are a superfamily of fluid phase pattern recognition molecules conserved in evolution and characterized by a cyclic multimeric structure. C-reactive protein (CRP) and serum amyloid P component (SAP) constitute the short pentraxin arm of the superfamily. CRP and SAP are produced in the liver in response to IL-6 and are acute phase reactants in humans and mice respectively. In addition SAP has been shown to affect tissue remodelling and fibrosis by stabilizing all types of amyloid fibrils and by regulating monocyte to fibrocyte differentiation. Pentraxin 3 (PTX3) is the prototype of the long pentraxin arm. Gene targeted mice and genetic and epigenetic studies in humans suggest that PTX3 plays essential non-redundant roles in innate immunity and inflammation as well as in tissue remodelling. Recent studies have revealed the role of PTX3 as extrinsic oncosuppressor, able to tune cancer-related inflammation. In addition, at acidic pH PTX3 can interact with provisional matrix components promoting inflammatory matrix remodelling. Thus acidification during tissue repair sets PTX3 in a tissue remodelling and repair mode, suggesting that matrix and microbial recognition are common, ancestral features of the humoral arm of innate immunity.

A new biomarker panel in bronchoalveolar lavage for an improved lung cancer diagnosis

INTRODUCTION

The enormous biological complexity and high mortality rate of lung cancer highlights the need for new global approaches for the discovery of reliable early diagnostic biomarkers. The study of bronchoalveolar lavage samples by proteomic techniques could identify new lung cancer biomarkers and may provide promising noninvasive diagnostic tools able to enhance the sensitivity of current methods.

METHODS

First, an observational prospective study was designed to assess protein expression differences in bronchoalveolar lavages from patients with (n = 139) and without (n = 49) lung cancer, using two-dimensional gel electrophoresis and subsequent protein identification by mass spectrometry. Second, validation of candidate biomarkers was performed by bead-based immunoassays with a different patient cohort (204 patients, 48 controls).

RESULTS

Thirty-two differentially expressed proteins were identified in bronchoalveolar lavages, 10 of which were confirmed by immunoassays. The expression levels of APOA1, CO4A, CRP, GSTP1, and SAMP led to a lung cancer diagnostic panel that reached 95% sensitivity and 81% specificity, and the quantification of STMN1 and GSTP1 proteins allowed the two main lung cancer subtypes to be discriminated with 90% sensitivity and 57% specificity.

CONCLUSIONS

Bronchoalveolar lavage represents a promising noninvasive source of lung cancer specific protein biomarkers with high diagnostic accuracy. Measurement of APOA1, CO4A, CRP, GSTP1, SAMP, and STMN1 in this fluid may be a useful tool for lung cancer diagnosis, although a further validation in a larger clinical set is required for early stages.

Contribution of bone marrow-derived fibrocytes to liver fibrosis

Since the discovery of fibrocytes in 1994 by Dr. Bucala and colleagues, these bone marrow (BM)-derived collagen Type I producing CD45(+) cells remain the most fascinating cells of the hematopoietic system. Despite recent reports on the emerging contribution of fibrocytes to fibrosis of parenchymal and non-parenchymal organs and tissues, fibrocytes remain the most understudied pro-fibrogenic cellular population. In the past years fibrocytes were implicated in the pathogenesis of liver, skin, lung, and kidney fibrosis by giving rise to collagen type I producing cells/myofibroblasts. Hence, the role of fibrocytes in fibrosis is not well defined since different studies often contain controversial results on the number of fibrocytes recruited to the site of injury versus the number of fibrocyte-derived myofibroblasts in the same fibrotic organ. Furthermore, many studies were based on the in vitro characterization of fibrocytes formed after outgrowth of BM and/or peripheral blood cultures. Therefore, the fibrocyte function(s) still remain(s) lack of understanding, mostly due to (I) the lack of mouse models that can provide complimentary in vivo real-time and cell fate mapping studies of the dynamic differentiation of fibrocytes and their progeny into collagen type I producing cells (and/or possibly, other cell types of the hematopoietic system); (II) the complexity of hematopoietic cell differentiation pathways in response to various stimuli; (III) the high plasticity of hematopoietic cells. Here we summarize the current understanding of the role of CD45(+) collagen type I(+) BM-derived cells in the pathogenesis of liver injury. Based on data obtained from various organs undergoing fibrogenesis or other type of chronic injury, here we also discuss the most recent evidence supporting the critical role of fibrocytes in the mediation of pro-fibrogenic and/or pro-inflammatory responses.

The long pentraxin PTX3 as a key component of humoral innate immunity and a candidate diagnostic for inflammatory diseases

The innate immune system is composed of a cellular arm and a humoral arm. Components of the humoral arm include members of the complement cascade and soluble pattern recognition molecules (PRMs). These PRMs recognize pathogen-associated molecular patterns and are functional ancestors of antibodies, playing a role in complement activation, opsonization and agglutination. Pentraxins consist of a set of multimeric soluble proteins and represent the prototypic components of humoral innate immunity. The prototypic long pentraxin PTX3 is highly conserved in evolution and produced by somatic and innate immune cells after proinflammatory stimuli. PTX3 interacts with a set of self, nonself and modified self ligands and exerts essential roles in innate immunity, inflammation control and matrix deposition. In addition, translational studies suggest that PTX3 may be a useful biomarker of human pathologies complementary to C-reactive protein. In this study, we will review the general functions of pentraxins in innate immunity and inflammation, focusing our attention on the prototypic long pentraxin PTX3.

PTX3 as a paradigm for the interaction of pentraxins with the complement system

Pentraxins are highly conserved components of the humoral arm of innate immunity. They include the short pentraxins C reactive protein (CRP) and serum amyloid P component (SAP), and the long pentraxin PTX3. These are soluble pattern-recognition molecules that are present in the blood and body fluids, and share the ability to recognize pathogens and promote their disposal. CRP and SAP are produced systemically in the liver while PTX3 is produced locally in a number of tissues, macrophages and neutrophils being major sources of this long pentraxin. Pentraxins interact with components of the classical and lectin pathways of Complement as well as with Complement regulators. In particular, PTX3 recognizes C1q, factor H, MBL and ficolins, where these interactions amplify the repertoire of microbial recognition and effector functions of the Complement system. The complex interaction of pentraxins with the Complement system at different levels has broad implications for host defence and regulation of inflammation.

Differential proteome profiling of pleural effusions from lung cancer and benign inflammatory disease patients

The pleural effusion proteome has been found containing information that directly reflects pathophysiological status and represents a potential diagnostic value for pulmonary diseases. However, the variability in protein composition between malignant and benign effusions is not well understood. Herein, we investigated the changes of proteins in pleural effusions from lung adenocarcinoma and benign inflammatory disease (pneumonia and tuberculosis) patients by two-dimensional difference gel electrophoresis (2D-DIGE). Twenty-eight protein spots displayed significantly different expression levels were positively identified by MALDI-TOF-MS representing 16 unique proteins. Five identified protein candidates were further validated and analyzed in effusions, sera or tissues. Among them, hemopexin, fibrinogen gamma and transthyretin (TTR) were up-regulated in cancer samples. The effusion concentration of serum amyloid P component (SAP) was significantly lower in lung cancer patients than in benign inflammatory patients, but no differences were found in sera samples. Moreover, a Jumonji C (JmjC)-domain-containing protein, JMJD5, was observed to be down-regulated in malignant effusions, lung cancer tissues and cancer cells. These results shed light on the altered pleural effusion proteins as a useful and important complement to plasma or other routine clinical tests for pulmonary disease diagnosis.

Discovery of candidate serum proteomic and metabolomic biomarkers in ankylosing spondylitis

Ankylosing Spondylitis (AS) is a common inflammatory rheumatic disease with a predilection for the axial skeleton, affecting 0.2% of the population. Current diagnostic criteria rely on a composite of clinical and radiological changes, with a mean time to diagnosis of 5 to 10 years. In this study we employed nano liquid-chromatography mass spectrometry analysis to detect and quantify proteins and small compounds including endogenous peptides and metabolites in serum from 18 AS patients and nine healthy individuals. We identified a total of 316 proteins in serum, of which 22 showed significant up- or down-regulation (p < 0.05) in AS patients. Receiver operating characteristic analysis of combined levels of serum amyloid P component and inter-α-trypsin inhibitor heavy chain 1 revealed high diagnostic value for Ankylosing Spondylitis (area under the curve = 0.98). We also depleted individual sera of proteins to analyze endogenous peptides and metabolic compounds. We detected more than 7000 molecular features in patients and healthy individuals. Quantitative MS analysis revealed compound profiles that correlate with the clinical assessment of disease activity. One molecular feature identified as a Vitamin D3 metabolite—(23S,25R)-25-hydroxyvitamin D3 26,23-peroxylactone—was down-regulated in AS. The ratio of this vitamin D metabolite versus vitamin D binding protein serum levels was also altered in AS as compared with controls. These changes may contribute to pathological skeletal changes in AS. Our study is the first example of an integration of proteomic and metabolomic techniques to find new biomarker candidates for the diagnosis of Ankylosing Spondylitis.

Pentraxins (CRP, SAP) in the process of complement activation and clearance of apoptotic bodies through Fcγ receptors

PURPOSE OF REVIEW

Ischemia/reperfusion injury and organ allograft rejection both entail excessive cell and tissue destruction. A number of innate immune proteins, including the pentraxins, participate in the removal of this potentially inflammatory and autoimmunogenic material. The classical pentraxins, C-reactive protein (CRP) and serum amyloid P component (SAP) are serum opsonins, which bind to damaged membranes and nuclear autoantigens. Understanding the role of pentraxins in inflammation has been advanced by the recent identification and structural analysis of their receptor interactions.

RECENT FINDINGS

The ligand-binding, complement-activating and opsonic properties of pentraxins have been known for some time. However, the establishment of Fcγ receptors as the primary receptors for pentraxins is a recent finding with important implications for CRP and SAP functions. The crystal structure of SAP in complex with FcγRIIa was recently solved, leading to new insights into function and new opportunities for pentraxin-based therapeutics. In addition, new approaches to inhibit CRP synthesis or binding are being developed based on clinical associations between CRP levels and cardiovascular disease.

SUMMARY

This review will summarize data on the function of pentraxins in clearance of injured tissue and cells and discuss the implications of this clearance pathway for autoimmunity and ischemia/reperfusion injury.

Utilizing spectral counting to quantitatively characterize tandem removal of abundant proteins (TRAP) in human plasma

Biomarker discovery efforts in serum and plasma are greatly hindered by the presence of high abundance proteins that prevent the detection and quantification of less abundant, yet biologically significant, proteins. The most common method for addressing this problem is to specifically remove the few abundant proteins through immunoaffinity depletion/subtraction. Herein, we improved upon this method by utilizing multiple depletion columns in series, so as to increase the efficiency of the abundant protein removal and augment the detection/identification of less abundant plasma proteins. Spectral counting was utilized to make quantitative comparisons between undepleted plasma, plasma depleted with a single depletion column, and plasma depleted using two or three depletion columns in tandem. In the undepleted plasma only 29 lower abundance protein groups were identified with the top-scoring protein from each group having a median spectral count of 3, while in the plasma processed using a single HSA depletion column 61 such protein groups were identified with a median spectral count of 8. In comparison, 76 lesser abundant protein groups were identified with a median spectral count of 11.5 in the two column setup (i.e., HSA followed by MARS Hu14). However, in the ultimate depleted plasma sample, which was created using three depletion columns in tandem, the number of less abundant protein groups identified increase to 81 and the median spectral count for the top-scoring proteins from each group increased to 15 counts per protein. Moreover, exogenous B-type natriuretic peptide-32, which was added to the plasma as a detection benchmark at 12 μg/mL, was only detected in the plasma sample depleted using three depletion columns in tandem. Collectively, these data demonstrate that this method, tandem removal of abundant proteins or TRAP, provides superior removal efficiency compared to traditional applications and improves the depth of proteome coverage in plasma.

Serum amyloid P inhibits fibrosis through Fc gamma R-dependent monocyte-macrophage regulation in vivo

New therapies that target chronic inflammation with fibrosis are urgently required. Increasing evidence points to innate activation of inflammatory cells in driving chronic organ fibrosis. Serum amyloid P is a naturally circulating soluble pattern recognition receptor, a member of the family of pentraxin proteins. It links danger-associated molecular pattern recognition to Fc gamma receptor-mediated phagocytosis. Here we show that fibrosis progression in the mouse kidney is significantly inhibited by therapeutic administration of human serum amyloid P, regulated by activating Fc gamma receptors, and dependent on inflammatory monocytes and macrophages, but not fibrocytes. Human serum amyloid P-mediated inhibition of mouse kidney fibrosis correlated with specific binding of human serum amyloid P to cell debris and with subsequent suppression of inflammatory monocytes and kidney macrophages in vitro and in vivo, and was dependent on regulated binding to activating Fc gamma receptors and interleukin-10 expression. These studies uncover previously unidentified roles for Fc gamma receptors in sterile inflammation and highlight serum amyloid P as a potential antifibrotic therapy through local generation of interleukin-10.

Serum markers may distinguish biliary atresia from other forms of neonatal cholestasis

BACKGROUND

Biliary atresia (BA) is the most serious liver disease in infants. Diagnosis currently depends on surgical exploration of the biliary tree. Noninvasive tests that distinguish BA from other types of neonatal liver disease are not available.

PATIENTS AND METHODS

To identify potential serum biomarkers that classify children with neonatal cholestasis, we performed 2-dimensional difference gel electrophoresis, statistical analysis, and tandem mass spectrometry using serum samples from 19 infants with BA and 19 infants with non-BA neonatal cholestasis.

RESULTS

Eleven potential serum biomarkers were found that could in combination classify children with neonatal cholestasis.

CONCLUSIONS

Although no single biomarker or imaging test adequately distinguishes BA from other types of neonatal cholestasis, combinations of biomarkers, imaging tests, and noninvasive clinical criteria should be further explored as potential tests for rapid and accurate diagnosis of BA.

A serum amyloid P-binding hydrogel speeds healing of partial thickness wounds in pigs

During wound healing, some circulating monocytes enter the wound, differentiate into fibroblast-like cells called fibrocytes, and appear to then further differentiate into myofibroblasts, cells that play a key role in collagen deposition, cytokine release, and wound contraction. The differentiation of monocytes into fibrocytes is inhibited by the serum protein serum amyloid P (SAP). Depleting SAP at a wound site thus might speed wound healing. SAP binds to some types of agarose in the presence of Ca(2+). We found that human SAP binds to an agarose with a K(D) of 7 x 10(-8) M and a B(max) of 2.1 microg SAP/mg wet weight agarose. Mixing this agarose 1 : 5 w/v with 30 microg/mL human SAP (the average SAP concentration in normal serum) in a buffer containing 2 mM Ca(2+) reduced the free SAP concentration to approximately 0.02 microg/mL, well below the concentration that inhibits fibrocyte differentiation. Compared with a hydrogel dressing and a foam dressing, dressings containing this agarose and Ca(2+) significantly increased the speed of wound healing in partial thickness wounds in pigs. This suggests that agarose/Ca(2+) dressings may be beneficial for wound healing in humans.

Inflammatory clearance of apoptotic cells after UVB challenge

In the human body, every day billions of apoptotic cells are produced. Removal of these cells is necessary, to prevent the release of intracellular toxic constituents, and occurs very effectively via phagocytosis by (semi)-professional phagocytes. This elimination process occurs rapidly and without inflammation. In systemic lupus erythematosus (SLE) a disturbed elimination of apoptotic cells has been implicated in the induction and reactivation of the disease. Accumulation of apoptotic cells may result in autoantibody formation. A delayed, pro-inflammatory clearance is also thought to play a crucial role in the development of inflammatory lesions once the disease has manifested. One of the hallmarks of patients with SLE is the development of cutaneous lesions upon exposure to sunlight. In this review, we will focus on apoptotic cells, their elimination, and the consequences of a disturbed elimination of apoptotic cells on the development of UVB induced inflammatory skin lesions.

Serum levels of ficolin-3 (Hakata antigen) in patients with systemic lupus erythematosus

OBJECTIVE

Ficolin-3 is a serum protein of putative importance in autoimmunity. Our objective was to investigate any differential expression of ficolin-3 in patients with systemic lupus erythematosus (SLE) or its clinical subsets.

METHODS

Serum levels of ficolin-3 (S-ficolin-3) were determined in 95 patients with SLE and 103 healthy controls using an ELISA.

RESULTS

Median S-ficolin-3 was 56.1 microg/ml (range 0 to >or=87.3) and 32.4 microg/ml (10 to >or=87.3) in patients and controls, respectively (p<0.001). Increased S-ficolin-3 was associated with hemolysis, positive Coombs test, and lymphopenia, but not with SLE Disease Activity Index scores or C-reactive protein. In one patient without detectable S-ficolin-3, the FCN3 gene appeared normal.

CONCLUSION

The elevation of S-ficolin-3 and its association with specific manifestations in SLE may indicate a pathogenetic role of ficolin-3 in SLE.

Systemic lupus erythematosus and familial Mediterranean fever: a possible negative association between the two disease entities – report of four cases and review of the literature

Serositis is a common clinical manifestation of systemic lupus erythematosus (SLE), as well as being the hallmark of familial Mediterranean fever (FMF), the most prevalent monogenic disease in the Jewish population. We have treated four patients who suffered from both SLE and FMF since 2001 in our clinic, which also serves as the national center for FMF. Our cases illustrate both similarities and dissimilarities between the clinical manifestations of these two diseases, an aspect which should be borne in mind, especially in the young female patients. In general, it seems that co-occurrence of FMF moderates the presentation of lupus.

Radiation leukemogenesis: a proteomic approach

OBJECTIVE

The objectives of this study were to identify protein biomarkers of radiation-induced acute myeloid leukemia (rAML) in CBA/CaJ mice, and to examine the similarities or differences in the patterns of protein-expression profiles among AMLs induced by low linear energy transfer (LET) radiation (e.g., gamma- or x-rays), and high LET radiation (i.e., neutrons).

MATERIALS AND METHODS

We used two-dimensional electrophoresis gel in combination with mass spectrometry (MS), i.e., matrix-assisted laser desorption ionization/time-of-flight MS and electrospray ionization-liquid chromatography/tandem mass spectrometry, to identify protein signatures in blood-plasma samples collected from control and rAML mice. There were nine cases of rAML (three cases induced by high LET radiation; six induced by low LET radiation) and eight control mice at similar ages.

RESULTS

The results showed differences in the patterns of protein profiles from blood-plasma samples collected from rAML vs control mice. Moreover, our data demonstrated, both qualitatively and quantitatively, differences between the plasma protein profiles obtained from mice with AML induced by low vs high LET radiation. Most of the proteins that were present at greater levels in normal samples than in rAML samples were associated with normal metabolism and growth. Several acute-phase proteins were upregulated in rAML samples.

CONCLUSION

The data present, for the first time, evidence for increased expression of clusterin and a loss of gelsolin expression in blood plasma as potential biomarkers of rAML in the CBA/CaJ mouse. Results also indicate that two-dimensional electrophoresis, in combination with MS, is a highly sensitive technique for identification of blood-based biomarkers of rAML.

Serum amyloid A in autoimmune thrombosis

The objectives of this study were (1) to determine how levels of serum amyloid A (SAA), high sensitivity C-reactive protein (CRP) and interleukin-6 (IL-6) correlate to autoimmune diseases in patients with or without thrombosis, and (2) to discuss the parameters that influence the relative SAA values. SAA, CRP and IL-6 concentrations were determined by enzyme linked immunosorbent assay (ELISA). 84 patients with secondary antiphospholipid syndrome (SAPS), primary antiphospholipid syndrome (PAPS), systemic lupus erythematosus with antiphospholipid antibodies (SLE+aPL), SLE, venous thrombosis (VT), arterial thrombosis (AT) were compared to healthy donors (n=60). The percentages of patients above cut-off were highest in the SAPS, SLE and SLE+aPL groups. Significant differences were observed between healthy donors and inflammatory groups of patients (SAPS and SLE+aPL) in all three measured parameters. SAA and CRP were shown to be correlated to a greater extent in SAPS patients than SLE+aPL patients. In summary, this cross-sectional, retrospective, small study and accompanying clinical considerations limit the ability to make definite conclusions. SAA would not serve as a useful marker for venous, arterial thrombosis or PAPS (pro-coagulant events). It could however, be a good predictor of progression from a non-inflammatory thrombotic condition to an inflammatory one.

[The role of long pentraxin 3, a new inflammatory mediator in inflammatory responses]

Pentraxin 3 (PTX3) is suggested to play important roles in the innate resistance against pathogens, regulation of inflammatory reactions, and clearance of apoptotic cells. PTX3 is the first long pentraxin identified. Long pentraxin shares a C-terminal pentraxin domain with the classical short pentraxin (C-reactive protein, serum amyloid P), but holds an unrelated N-terminal domain that is unique to the long pentraxin. While the short pentraxin is produced only in the liver, PTX3 is made by diverse types of cells, prominently endothelial cells and macrophage, in response to inflammatory signals. Unlike the short pentraxin, the expression of PTX3 in multiple types of tissue cells implies a mechanism for local amplification of innate resistance at the site of infection and inflammation. PTX3 plasma levels are very low in normal subjects but are rapidly increased by inflammatory conditions resulting from a wide range of diseased states, from infection to autoimmune and degenerative disorders. Critically ill patients show elevated circulating levels of PTX3 which are determined by the severity of the disease. Clinical evidence has demonstrated that the elevated PTX3 levels might be a useful early and sensitive marker for severely ill patients. Further studies will definitely be needed to deepen our understanding of PTX3.

Novel cardiovascular risk factors and cardiac event predictors in female inactive systemic lupus erythematosus patients

Systemic lupus erythematosus (SLE) is associated with severe and premature cardiovascular disease, which cannot be explained by traditional risk factors alone. This study aims to investigate novel cardiovascular risk factors and cardiac event predictors in inactive SLE female patients who do not have any major cardiovascular risk factors. Twenty-five inactive (SLE disease activity index score <4) SLE female patients and 22 healthy control women were studied. SLE patients with a history of diabetes mellitus, hypertension, hyperlipidemia, smoking, or coronary artery disease (CAD) were excluded. Venous blood samples were analyzed for lipid subfractions and novel cardiovascular risk factors such as lipoprotein (a), homocysteine, fibrinogen, high-sensitivity C-reactive protein (hs-CRP), and serum amyloid A (SAA) levels. Endothelial dysfunction was assessed by flow-mediated dilatation (FMD) from the brachial artery at baseline and during reactive hyperemia. SLE patients and controls were similar in terms of age (40+/-10 years vs 38+/-10 years, p = NS). No significant difference was found between the groups regarding family history of premature CAD, blood pressure, body mass index, lipoprotein (a), homocysteine, fibrinogen, SAA, apoprotein A-1 and B levels. Compared with the controls, SLE patients had higher levels of hs-CRP [median (range): 1.82 (0.02-0.98) vs 0.68 (0.02-0.35), p=0.04]. FMD was lower in SLE patients than controls (7.1+/-2.1 vs 11.4+/-1.2%, p<0.001). Increased levels of hs-CRP and decreased FMD were found in inactive SLE patients. Increased hs-CRP levels may reflect ongoing low-grade inflammation that could be a cause of impaired FMD in SLE patients. These findings suggest that SLE patients without traditional major cardiovascular risk factors may have increased risk of cardiovascular disease and future cardiac events.

Heterobifunctional multivalent inhibitor-adaptor mediates specific aggregation between Shiga toxin and a pentraxin

[reaction: see text] The first example of a multivalent heterofunctional inhibitor-adaptor, called "BAIT", is described. This multivalent inhibitor-adaptor is able to capture a "target" receptor (Shiga toxin) through its recognition of one ligand of a heterobivalent headgroup while the other ligand binds to an endogenous "trap" protein (serum amyloid P component, SAP). BAIT showed markedly enhanced inhibition of toxin activity. An efficient synthesis of this multivalent cluster containing heterobifunctional ligands was accomplished by chemical and chemoenzymatic approaches.

Nucleosome autoantibodies

The nucleosome is a large protein-nucleic acid complex involved in DNA packing and in controlling genetic information. Under circumstances described below, this component, normally sequestered in the cell nucleus, is released into the extracellular milieu and then is easily accessible to cells of the immune system. For still not completely understood reasons, nucleosomes become immunogenic under particular conditions. Thus, anti-nucleosome autoantibodies (autoAb) have been described in connective tissue diseases and especially in systemic lupus erythematosus (SLE). This review describes the mechanisms leading to nucleosome production and anti-nucleosome autoimmunity, as well as the pathogenesis associated with nucleosomes.

Depletion of multiple high-abundance proteins improves protein profiling capacities of human serum and plasma

Systematic detection of low-abundance proteins in human blood that may be putative disease biomarkers is complicated by an extremely wide range of protein abundances. Hence, depletion of major proteins is one potential strategy for enhancing detection sensitivity in serum or plasma. This study compared a recently commercialized HPLC column containing antibodies to six of the most abundant blood proteins ("Top-6 depletion") with either older Cibacron blue/Protein A or G depletion methods or no depletion. In addition, a prototype spin column version of the HPLC column and an alternative prototype two antibody spin column were evaluated. The HPLC polyclonal antibody column and its spin column version are very promising methods for substantially simplifying human serum or plasma samples. These columns show the lowest nonspecific binding of the depletion methods tested. In contrast other affinity methods, particularly dye-based resins, yielded many proteins in the bound fractions in addition to the targeted proteins. Depletion of six abundant proteins removed about 85% of the total protein from human serum or plasma, and this enabled 10- to 20-fold higher amounts of depleted serum or plasma samples to be applied to 2-D gels or alternative protein profiling methods such as protein array pixelation. However, the number of new spots detected on 2-D gels was modest, and most newly visualized spots were minor forms of relatively abundant proteins. The inability to detect low-abundance proteins near expected 2-D staining limits was probably due to both the highly heterogeneous nature of most plasma or serum proteins and masking of many low-abundance proteins by the next series of most abundant proteins. Hence, non2-D methods such as protein array pixelation are more promising strategies for detecting lower abundance proteins after depleting the six abundant proteins.

Levels of complement in sera from inactive SLE patients, although decreased, do not influence in vitro uptake of apoptotic cells

BACKGROUND

Accumulation of apoptotic cells is considered relevant in the pathogenesis of systemic lupus erythematosus (SLE). Complement factors facilitate the clearance of apoptotic cells and, when decreased, might result in an increased amount of apoptotic cells found in SLE patients.

OBJECTIVE

To determine the influence of complement profiles from inactive SLE patients on the in vitro phagocytosis of apoptotic cells.

METHODS

Consecutive SLE patients (n=98) with inactive disease (SLEDAI < or =4) and 20 healthy controls (HC) were included. Levels of CH50, C3, C4, C1q, and C1r were measured. Human peripheral blood monocytes were isolated from healthy controls and cultured for 7 days to obtain monocyte-derived macrophages (MDM). Jurkat cells were irradiated with UVB to induce apoptosis. Phagocytosis was tested by incubation of MDM with apoptotic cells in the presence of serum and quantified as phagocytosis index (number of Jurkat cells internalized by 100 macrophages). Serum from 20 patients with CH50<65%, 20 patients with CH50 > or =65%, and 20 HC were used in this assay.

RESULTS

All HC and 37% of patients had normal complement levels. CH50 level was decreased in 21% of patients, C3 in 52%, C4 in 29%, C1q in 2% and C1r in 44% of patients. Between patients and HC, differences in level of CH50, C3 and C4 were statistically significant. No difference in phagocytosis index between HC and patients, irrespective of their CH50 level, was detected. No correlation was found between the respective complement levels and phagocytosis index.

CONCLUSION

In most SLE patients with inactive disease, levels of one or more complement components are decreased. However, decreased levels of complement do not result in a significantly reduced in vitro uptake of apoptotic Jurkat cells by MDM.

Anti-serum amyloid component P antibodies in patients with systemic lupus erythematosus correlate with disease activity

OBJECTIVE

To determine the presence of raised titres of anti-serum amyloid P component (SAP) antibodies in patients with systemic lupus erythematosus (SLE) and to evaluate their correlation with clinical disease by the SLEDAI and clinical manifestations.

METHODS

452 samples were screened for raised anti-SAP antibody titres by an ELISA. Clinical measures and SLEDAI scores were independently reviewed from medical records. 21 serial samples from 7 patients with SLE were assessed for a change in anti-SAP antibody titres after treatment.

RESULTS

Raised anti-SAP antibody titres were detected in 145/328 (44%) SLE samples. In 112 randomly selected samples, 69/112 (62%) patients had raised anti-SAP antibodies and anti-dsDNA antibody titres, whereas only 32/112 (28%) had raised anti-dsDNA antibody titres without raised anti-SAP antibody titres. The mean titre of anti-SAP antibodies in patients with active disease was higher than in patients with inactive disease and controls. SLEDAI scores, assessed in 54 patients, were raised in 26/31 (84%) patients with raised anti-SAP antibody titres. A SLEDAI score >or=8 was found in 16/31 (52%) patients with raised anti-SAP antibody titres but in only 5/23 (22%) patients without raised titres. No specific pattern of disease was detected in patients with or without raised titres of anti-SAP antibodies. Serial sampling from patients with active SLE and raised anti-SAP antibody titres showed that anti-SAP antibody titres decreased after treatment and correlated with clinical improvement.

CONCLUSION

Raised anti-SAP antibody titres detected in patients with SLE correlate with disease activity and decrease with improvement of clinical disease, and thus may serve as an additional prognostic marker.