Induction of primary antiphospholipid syndrome in mice by immunization with a human monoclonal anticardiolipin antibody (H-3)

Lipid-binding antiphospholipid antibodies: significance for pathophysiology and diagnosis of the antiphospholipid syndrome

The antiphospholipid syndrome (APS) is an autoimmune disease characterized by the presence of pathogenic antiphospholipid antibodies (aPL). Since approximately 30 years ago, lipid-binding aPL, which do not require a protein cofactor, have been regarded as irrelevant for APS pathogenesis even though anticardiolipin are a diagnostic criterion of APS. In this review, we will summarize the available evidence from in vitro studies, animal models, and epidemiologic studies, which suggest that this concept is no longer tenable. Accordingly, we will only briefly touch on the role of other aPL in APS. This topic has been amply reviewed in detail elsewhere. We will discuss the consequences for laboratory diagnostics and future research required to resolve open questions related to the pathogenic role of different aPL specificities.

A Comparative Analysis of Anticardiolipin, Anti-Β2-Glycoprotein-1, and Lupus Anticoagulants in Saudi Women with Recurrent Spontaneous Abortions

Association and pathogenesis of antiphospholipid antibodies (APAs) in patients with Antiphospholipid syndrome (APS) as well as systemic lupus erythematosus (SLE) suffering from unexplained spontaneous abortions is controversial. Moreover, the majority of the published evidence is based on the patient histories rather than the study groups. The main objective of the present study is to do a comparative analysis of the high levels of antiphospholipid antibodies (APAs) including anticardiolipin (ACA), anti-β2-glycoprotein-1 (β2 GP1), and Lupus anticoagulants (LA) and their association with the gestational age of abortion and duration past abortion in Saudi women. In this study, 100 women living in Makkah city, located in the Western region of Saudi Arabia, with a mean age of 30.5 ± 12.60 years (mean ± standard deviation), having a previous history of recurrent spontaneous abortions were enrolled as case group and 100 healthy pregnant women previously having one or more successful pregnancies were selected as control group. Based on the gestational age of the patient’s miscarriages, our results revealed consistently and significantly high levels of ACA, β2 GP1, and LA, being greatest at more than 15 weeks when compared with 10 weeks and 11−15 weeks, respectively. Based on duration of past miscarriages, a slightly increased level was observed at ≤4 years after their first miscarriage. In addition, less or more equal levels of these antibodies were observed at 5−12 and more than 12 years in all the cases of miscarriages. We concluded an elevated pattern of APAs in these patients with an increase in the age of abortion. A comparison between the levels of ACA, β2 GP1, and LA further indicated a highly significant level of LA in all the cases of abortions (p < 0.0005).

Understanding main pregnancy complications through animal models

Since human pregnancy is an inefficient process, achieving desired and pleasant outcome of pregnancy - the birth of a healthy and fit baby - is the main goal in any pregnancy. Spontaneous pregnancy failure is actually the most common complication of pregnancy and Most of these pregnancy losses are not known. Animal models have been utilized widely to investigate the system of natural biological adaptation to pregnancy along with increasing our comprehension of the most important hereditary and non-hereditary factors that contribute to pregnancy disorders. We use model organisms because their complexity better reproduces the human condition. A useful animal model for the disease should be pathologically similar to the disease conditions in humans. Animal models deserve a place in research because of the ethical limitations that apply to pregnant women's experiments. The present review provides insights into the overall risk factors involved in recurrent miscarriage, recurrent implant failure and preeclampsia and animal models developed to help researchers identify the source of miscarriage and the best research and treatment strategy for women with Repeated miscarriage and implant failure.

Lipid presentation by the protein C receptor links coagulation with autoimmunity

Antiphospholipid antibodies (aPLs) cause severe autoimmune disease characterized by vascular pathologies and pregnancy complications. Here, we identify endosomal lysobisphosphatidic acid (LBPA) presented by the CD1d-like endothelial protein C receptor (EPCR) as a pathogenic cell surface antigen recognized by aPLs for induction of thrombosis and endosomal inflammatory signaling. The engagement of aPLs with EPCR-LBPA expressed on innate immune cells sustains interferon- and toll-like receptor 7-dependent B1a cell expansion and autoantibody production. Specific pharmacological interruption of EPCR-LBPA signaling attenuates major aPL-elicited pathologies and the development of autoimmunity in a mouse model of systemic lupus erythematosus. Thus, aPLs recognize a single cell surface lipid-protein receptor complex to perpetuate a self-amplifying autoimmune signaling loop dependent on the cooperation with the innate immune complement and coagulation pathways.

Detection of Anti-Phospholipid and Anti-DNA Antibodies and their Idiotypes in Newborns of Mothers with Anti-Phospholipid Syndrome and Sle

The titers, isotypes and idiotypes of antiphospholipid and anti-dsDNA antibodies were determined in seven pairs of mothers with antiphospholipid syndrome (APLS) and their offspring, in 11 pairs of SLE mothers and their matched infants and in seven respective pairs of healthy subjects. In addition, maternal as well as fetal sera were evaluated for the presence of anti-SSA (Ro), anti-SSB (La) and anti-70 kd RNP autoantibodies.

In the sera from APLS patients, as well as in the sera from their offspring, the mean antibody titer of IgG aCL was found to be significantly higher then the corresponding value in the control group (P < 0.01). Highly significant increased titers of IgG anti-DNA antibodies were found in the sera of SLE mothers and their matched offspring (P < 0.0008).

The prevalance of anti-SSA, anti-SSA, and anti-7OKd RNP antibodies was lower then that of antiphospholipid and anti-dsDNA antibodies. Only one of the respective offspring had increased levels of these antibodies.

The quantity of maternal antibodies transferd to the fetus was depended on their concentration in the maternal circulation, as well as on their type and specificity. Follow-up of newborn sera showed a progressive decrease in the antiphospholipid antibody titers during 3 months. After 6 months it was undetected.

Our results point to a transplacental transfer of aCL and anti-DNA antibodies, a phenomenon which is not necessarily associated with respective clinical manifestations, in contrast to the classical humoral mediated autoimmune diseases (e.g. myasthenia gravis).

[Research progress on the relationship and mechanisms between periodontal disease and preterm birth and low-birth-weight infants]

Preterm birth (PB) is defined as the birth of a baby less than 37 weeks of gestational age. Low birth weight (LBW) is defined as a newborn baby's weight of less than 2 500 g. PB is often accompanied by LBW. Preterm low birth weight (PLBW) is the leading cause of newborn deaths. Periodontal disease (PD) is a chronic oral infectious disease, and it is closely related with general health. Epidemiological data show that PD is a risk factor for PLBW and other adverse pregnancy outcomes. The possible mechanisms include the direct effects of periodontal bacteria, inflammatory reactions, and immune response; however, the exact pathogenetic mechanism involved remains controversial. This article aims to review the research progress on the relationship between PD and PLBW and their underlying mechanisms, as well as the effects of periodontal treatment on PLBW incidence.

Decreased hippocampal cell proliferation in mice with experimental antiphospholipid syndrome

The antiphospholipid syndrome (APS) is an autoimmune disease characterized by the presence of antiphospholipid antibodies, which may trigger vascular thrombosis with consecutive infarcts. However, cognitive dysfunctions representing one of the most commonest neuropsychiatric symptoms are frequently present despite the absence of any ischemic brain lesions. Data on the structural and functional basis of the neuropsychiatric symptoms are sparse. To examine the effect of APS on hippocampal neurogenesis and on white matter, we induced experimental APS (eAPS) in adult female Balb/C mice by immunization with β2-glycoprotein 1. To investigate cell proliferation in the dentate gyrus granular cell layer (DG GCL), eAPS and control mice (n = 5, each) were injected with 5-bromo-2'-deoxyuridine (BrdU) once a day for 10 subsequent days. Sixteen weeks after immunization, eAPS resulted in a significant reduction of BrdU-positive cells in the DG GCL compared to control animals. However, double staining with doublecortin and NeuN revealed a largely preserved neurogenesis. Ultrastructural analysis of corpus callosum (CC) axons in eAPS (n = 6) and control mice (n = 7) revealed no significant changes in CC axon diameter or g-ratio. In conclusion, decreased cellular proliferation in the hippocampus of eAPS mice indicates a limited regenerative potential and may represent one neuropathological substrate of cognitive changes in APS while evidence for alterations of white matter integrity is lacking.

Cofactor-independent antiphospholipid antibodies activate the NLRP3-inflammasome via endosomal NADPH-oxidase: implications for the antiphospholipid syndrome

The antiphospholipid syndrome (APS) is an autoimmune disease characterised by thromboembolic events and/or pregnancy morbidity in the presence of antiphospholipid antibodies (aPL). Here we show that three cofactor independent human monoclonal aPL can induce transcription of NLRP3 and caspase-1 resulting in inflammasome activation specific for NLRP3. This depends fully on activation of endosomal NADPH-oxidase-2 (NOX2) by aPL. Activation of NOX2 and subsequent inflammasome activation by aPL are independent from TLR2 or TLR4. While endosomal superoxide production induces caspase-1 and NLRP3 transcription, it does not affect prae-IL-1β transcription. Therefore, release of IL-1β occurs only after activation of additional pathways like TLR7/8 or TLR2. All effects exerted by the monoclonal aPL can be reproduced with IgG fractions of APS patients proving that the monoclonal aPL are representative for the APS. IgG fractions of healthy controls or patients suffering from systemic lupus erythematosus have no effect. In a mouse model of the APS we can show inflammasome activation in vivo. Furthermore, mononuclear cells isolated from patients with the APS show an increased expression of caspase-1 and NLRP3 which is accompanied by a three-fold increased serum concentration of IL-1β suggesting chronic inflammasome activation in APS patients. In summary, we provide further evidence that endosomal NOX2 can be activated by cofactor independent aPL. This leads to induction of the NLRP3 inflammasome. Our data indicate that cofactor independent aPL might contribute significantly to the pathogenesis of the APS.

Case Report Hepatic Infarction in a Pregnant Patient with the ‘Primary’ Antiphospholipid Syndrome

We describe a patient with previous venous thrombosis while using oral contraceptives and recurrent pregnancy loss, who presented with massive hepatic infarction in the last trimester of the fourth gestation. Thrombocytopenia, the lupus anticoagulant (LA) and the anti-cardiolipin antibody (aCL) were detected and a diagnosis of a ‘primary’ antiphospholipid syndrome (APS) was made. The clinical and histological manifestations and the differential diagnosis, especially with DIC and pre-eclampsia, are discussed.

Fish oil attenuates neurologic severity of antiphospholipid syndrome in a mice experimental model

INTRODUCTION

Murine experimental models of antiphospholipid syndrome (eAPLS) showed neurologic dysfunction and therapeutic effect of the anticoagulant enoxaparin is well established. Omega-3 fatty acids and curcumin, tested in neuroinflammation and auto-immunity diseases, might be interesting therapeutic candidates. The aim of this study was to evaluate the effects of these candidates on neurologic severity in eAPLS.

METHODS

One month after immunization of BALB/c mice with beta-2-glycoprotein I, daily treatments were initiated with enoxaparin (1 mg/kg), omega-3 fatty acids (0.5 g/kg), and curcumin (200 mg/kg) for 3 months.

RESULTS

Mortality was significantly decreased by enoxaparin and omega-3 treatments. Fish oil and curcumin group exhibited the highest mean of swimming behavior in forced swim test in surviving mice. Mice under omega-3 fatty acids or curcumin presented low anxiety-like behavior in the elevated plus-maze test. Cerebral histopathology revealed heavy inflammatory infiltrates in cortical and subcortical regions with vacuolization, swelling, and degeneration of astrocytes in the control group, with aggravation under curcumin; no infiltrate was retrieved in enoxaparin and omega-3 groups.

CONCLUSION

Our study is the first to demonstrate a potential therapeutic effect of omega-3 fatty acids in eAPLS. Enoxaparin and omega-3 fatty acids combination would be interesting for further investigation.

Cytokines in recurrent miscarriage

Cytokines act at all stages of pregnancy from implantation to parturition. This review examines their relevance in recurrent miscarriage. However, recurrent miscarriage may be due to an inherently abnormal embryo (e.g., chromosomal abberations) or maternal factors (e.g., uterine anomalies or antiphospholipid antibodies). In the former, cytokines are not causitive, but may be part of the mechanism of abortion. In the antiphospholipid syndrome, cytokines such as TNFa and IL-6 may be responsible for the associated thrombosis. Hence, an appropriate cytokine milieu could be responsible for whether the antibodies are pathogenic or merely an epiphenomenon. Natural killer cells seem to have a key role in immunosurveillance of the invading trophoblast. However, if activated by TNFa, natural killer cells may induce apoptosis in the trophoblast possibly leading to miscarriage. This action is inhibited by TGFb. Early ultrasound scanning and embryoscopy have revealed structural anomalies in karyotypically normal embryos which have terminated in first trimester missed abortion. Teratogens such as cyclophosphamide cause fetal demise by excessive apoptosis. Excessive apoptosis may be mediated by TNFa, TGFb and other cytokines. GM-CSF has been reported to prevent teratogenesis in laboratory animals. Both immunomodulation and hormonal support (progesterone or hCG supplements) have been used to improve the live birth rate in recurrently aborting women. Each may modulate the balance between various cytokines. Although neither hormonal support or immunopotentiation have been proven to be beneficial, the results and the role of cytokines themselves can only be assessed in trials of karyotypically normal embryos.

Autoantibodies associated with reproductive failure

Autoimmune factors are involved in some of the cases of reproductive failure. These factors entail several autoantibodies, especially in patients having systemic lupus erythematosus (SLE) or the antiphospholipid syndrome (APS). These autoantibodies include mainly antibodies directed to phospholipid such as cardiolipin, phosphatidylserine, phosphatidylethanolamine or phospholipids binding glycoproteins such as b2glycoprotein-I, annexin V, prothrombin and protein-Z. There are also some other autoantibodies directed to laminin-I, thromboplastin, mitochondrial antibodies of the M5 type, corpus luteum, prolactin, poly (ADP-ribose), thyroglobulin and more, which were also found in SLE or APS patients with reproductive failure. Moreover, the presence of additional autoantibodies directed to actin, enolase, cubilin and others, needs further investigation to support a firm association to reproductive failure in women. Future studies are likely to help to determine and expand the number of autoantibodies screened in these patients, as well as by the use of proteomics technology, to determine peptides resembling the epitope specificities associated with the specific clinical manifestations.

Atherosclerosis in LDL-receptor knockout mice is accelerated by immunization with anticardiolipin antibodies

Atherosclerosis is a process initiated by accumulation of macrophages in distinct areas of endothelial cell damage and uptake of large amounts of lipids. Recently, it has been shown that the immune system plays an active part in the progression of the atherosclerotic plaque although its precise role has not yet been elucidated.

Anticardiolipin antibodies (aCL) are generally found in the sera of patients with the antiphospholipid syndrome (APS) and are associated with a prothrombotic state. Several authors have demonstrated that aCL can activate platelets and endothelial cells as well as increase oxidized low density lipoprotein (LDL) uptake by macrophages. In the present study we sought to assess the effect of immunization with aCL (Ab1, leading to the production of mouse aCL-Ab3) on the progression of atherosclerosis. Two groups of 8-weeks old female LDL-receptor knockout mice (n = 13 per group) were immunized with IgG purified from the serum of an APS patient or with normal human IgG, respectively. The aCL immunized mice developed high titres of 'self' aCL (detected using the standard aCL ELISA) as compared with the normal human IgG immunized mice, whereas no differences were noted between both study groups with respect to the serum lipid levels. The extent of fatty streak formation was significantly higher in the aCL immunized mice in comparison with the human IgG injected mice (mean aortic lesion size of 5308 ± 471 μm2 vs 1027 ± 184 μm2, respectively, P < 0.01). The immunohistochemical analysis of the atherosclerotic plaques from both mouse groups did not display differences in cellular composition.

The results of the study show that mouse aCL induced by immunization with human aCL from an APS patient enhance atherogenesis in LDL-RKO mice and imply that these antibodies may play a role in atherosclerosis development in patients with the APS.

Antiphospholipid Antibodies: Their Origin and Development

Antiphospholipid antibodies (aPL) are a hallmark of the antiphospholipid syndrome (APS), which is the most commonly acquired thrombophilia. To date there is consensus that aPL cause the clinical manifestations of this potentially devastating disorder. However, there is good evidence that not all aPL are pathogenic. For instance, aPL associated with syphilis show no association with the manifestations of APS. While there has been intensive research on the pathogenetic role of aPL, comparably little is known about the origin and development of aPL. This review will summarize the current knowledge and understanding of the origin and development of aPL derived from animal and human studies.

The role of anti-phospholipid antibodies in autoimmune reproductive failure

Anti-phospholipid antibodies (aPL) are autoantibodies that are associated with thrombosis and a range of pregnancy complications including recurrent pregnancy loss and pre-eclampsia. The three clinically relevant, well-characterized aPL are anti-cardiolipin antibodies, lupus anticoagulant and anti-beta-2-glycoprotein I (β2GPI) antibodies. aPL do not bind directly to phospholipids but instead bind to a plasma-binding ‘cofactor’. The most extensively studied cofactor is β2GPI, whose role in pregnancy is not fully elucidated. Although the pathogenicity of aPL in recurrent pregnancy loss is well established in humans and animal models, the association of aPL with infertility does not appear to be causative. aPL may exert their detrimental effects during pregnancy by directly binding trophoblast cells of the placenta, altering trophoblast signalling, proliferation, invasion and secretion of hormones and cytokines, and by increasing apoptosis. Heparin is commonly used to treat pregnant women with aPL; however, as thrombotic events do not occur in the placentae of all women with aPL, it may exert a protective effect by preventing the binding of aPL to β2GPI or by acting through non-thrombotic pathways. The aim of this review is to present evidence summarizing the current understanding of this field.

Elucidation of the potential disease-promoting influence of IgM apoptotic cell-reactive antibodies in lupus

The undigested remnants of apoptosis are believed to stimulate the generation of autoantibodies in lupus. The biological properties of initiator, disease-specific IgM antibodies that specifically recognize apoptotic cells, readily detected in the sera of lupus patients, remain unclear. Apoptotic cell-reactive IgM monoclonal antibodies (generated from lupus-prone mice), as opposed to control IgM, preferentially stimulated maturation of bone marrow-derived dendritic cells (BMDCs) derived from such mice, relative to BMDCs derived from healthy mice. An influence of both antibody specificity and cell genotype was also apparent in the secretion of signature inflammatory cytokines. Immunization of such antibodies in lupus-prone animals induced increases in total serum IgG levels, with the elicited antibodies also preferentially recognizing moieties on dying cells. An expanded specificity was apparent both upon Western blot on cellular lysate and from the enhanced recognition of dsDNA, Ro60, RNP68 and Sm; the antibody most efficient in mediating autoreactive diversity, while being germline encoded, also induced the highest degree of phenotypic changes on BMDCs. Apoptotic cell-reactive IgM antibodies may therefore be potentially capable of influencing the course of systemic autoimmune disease by affecting both innate and adaptive immunity.

Mice with experimental antiphospholipid syndrome display hippocampal dysfunction and a reduction of dendritic complexity in hippocampal CA1 neurones

AIMS

The antiphospholipid syndrome (APS) is an autoimmune disease characterized by high titres of auto-antibodies (aPL) leading to thrombosis and consequent infarcts. However, many affected patients develop neurological symptoms in the absence of stroke. Similarly, in a mouse model of this disease (eAPS), animals consistently develop behavioural abnormalities despite lack of ischemic brain injury. Therefore, the present study was designed to identify structural alterations of hippocampal neurones underlying the neurological symptoms in eAPS.

METHODS

Adult female Balb/C mice were subjected to either induction of eAPS by immunization with β2-Glycoprotein 1 or to a control group. After sixteen weeks animals underwent behavioural and cognitive testing using Staircase test (experiment 1 and 2) and Y-maze alternation test (experiment 1) and were tested for serum aPL levels (both experiments). Animals of experiment 1 (n = 7/group) were used for hippocampal neurone analysis using Golgi-Cox staining. Animals of experiment 2 (n = 7/group) were used to analyse molecular markers of total dendritic integrity (MAP2), presynaptic plasticity (synaptobrevin 2/VAMP2) and dendritic spines (synaptopodin) using immunohistochemistry.

RESULTS

eAPS mice developed increased aPL titres and presented with abnormal behaviour and impaired short term memory. Further, they revealed a reduction of dendritic complexity of hippocampal CA1 neurones as reflected by decreased dendritic length, arborization and spine density, respectively. Additional decrease of the spine-associated protein expression of Synaptopodin points to dendritic spines as major targets in the pathological process.

CONCLUSION

Reduction of hippocampal dendritic complexity may represent the structural basis for the behavioural and cognitive abnormalities of eAPS mice.

Periodontal disease, atherosclerosis, adverse pregnancy outcomes, and head-and-neck cancer

Interrelationships between periodontal infection and systemic conditions such as cardiovascular disease, adverse pregnancy outcomes, and head-and-neck cancer have become increasingly appreciated in recent years. Periodontitis is associated with cardiovascular disease (CVD) and, experimentally, with measures of atherosclerosis and endothelial dysfunction. Periodontal therapy may reduce atherosclerotic changes and improve endothelial function. Preliminary findings suggest a role for the genetic locus ANRIL in the pathobiology of both CVD and periodontitis. Periodontal pathogens induce anticardiolipin in periodontitis patients by molecular mimicry of the serum protein β-2 glycoprotein I. These antibodies have biological and pathological activities consistent with those reported for other infection-induced antiphospholipid antibodies. Anticardiolipin may explain some of the observed associations between periodontitis and systemic conditions such as CVD and adverse pregnancy outcomes. The oral commensal Fusobacterium nucleatum (Fn) becomes pathogenic on migration to extra-oral sites. Fn infection of the fetal-placental unit has been linked to pregnancy complications, including preterm birth, stillbirth, and early-onset neonatal sepsis. Reagents aimed at inhibiting or resolving inflammatory responses may be used to treat or prevent pregnancy complications due to bacterial infection. Chronic periodontitis may be independently associated with head-and-neck squamous cell carcinoma (HNSCC) through direct toxic effects of bacteria and their products, and/or through indirect effects of inflammation. Additionally, chronic periodontitis may facilitate the acquisition and persistence of oral HPV infection, a recently emerged risk factor for HNSCC.

Altered receptor binding densities in experimental antiphospholipid syndrome despite only moderately enhanced autoantibody levels and absence of behavioral features

Experimental antiphospholipid syndrome (eAPS) in Balb/c mice causes neuropsychiatric abnormalities including hyperactivity, increased explorative behavior and cognitive deficits. Recently, we have demonstrated that these behavioral changes were linked to an upregulation of serotonergic 5-HT1A receptor binding densities in cortical and hippocampal regions while excitatory and inhibitory neurotransmitter receptors remain largely unchanged. To examine whether the observed behavioral features depend on a critical antibody concentration, mice with only moderately enhanced antiphospholipid antibodies (aPL), about 50-80% of high levels, were analyzed and compared to controls. The staircase test was used to test animals for hyperactivity and explorative behavior. The brains were analyzed for tissue integrity and inflammation. Ligand binding densities of NMDA, AMPA, GABAA, 5-HT1A, M1 and M2 muscarinic acetylcholine receptors, respectively, were analyzed by in vitro receptor autoradiography and compared to brains of mice from our previous study with high levels of aPL. Mice with only moderately enhanced aPL did not develop significant behavioral changes. Brain parenchyma remained intact and neither inflammation nor glial activation was detectable. However, there was a significant decrease of NMDA receptor binding densities in the motor cortex as well as an increase in M1 binding densities in cortical and hippocampal regions, whereas the other receptors analyzed were not altered. Lack of neuropsychiatric symptoms may be due to modulations of receptors resulting in normal behavior. In conclusion, our results support the hypothesis that high levels of aPL are required for the manifestation of neuropsychiatric involvement while at lower antibody levels compensatory mechanisms may preserve normal behavior.

Coagulopathy triggered autoimmunity: experimental antiphospholipid syndrome in factor V Leiden mice

BACKGROUND

We investigated interactions between genetically and autoimmune-mediated coagulopathies by inducing experimental antiphospholipid syndrome (eAPS) in mice carrying the factor V Leiden (FVL) mutation.

METHODS

eAPS was induced in heterozygous and homozygous FVL transgenic mice (C57BL/6 background) by immunization with β(2)-glycoprotein I (β(2)-GPI). Autoantibody levels were measured at 1 and 5 months post-immunization. Mice were tested at 4 months post-immunization for behavior and cognitive function in the staircase, elevated plus-maze, and swim T-maze tests. Brains were removed and analyzed by immunohistochemistry for inflammatory markers and neurodegenerative processes.

RESULTS

A single immunization with β(2)-GPI induced significantly higher and longer-lasting immune responses, and this was dependent on the number of FVL alleles. At 1 and 5 months post-immunization, levels of antibodies rose from 1.17 ± 0.07 to 1.62 ± 0.17 (optical density units; ODU) in homozygous FVL mice, compared with stable levels of 0.59 ± 0.17 and 0.48 ± 0.16 ODU in heterozygous FVL mice and a drop from 1.62 ± 0.21 to 0.61 ± 0.13 ODU in wild-type mice. Behavioral and cognitive clinical features of eAPS were also correlated with FVL allele load, as assessed by the elevated plus-maze (altered anxiety), staircase (hyperactivity and higher exploration), and swim T-maze (impaired learning) tests. Histological studies identified significant neurodegenerative changes in both grey and white matter in the eAPS-FVL brains. In spite of the potential interaction of two prothrombotic disease states, there were no ischemic lesions seen in this group.

CONCLUSIONS

The results indicate that genetically mediated coagulopathies increase the risk of developing coagulation-targeted autoimmune responses, and suggest the importance of antibody-mediated neurodegenerative processes in the brain in APS.

The anti-phospholipid antibody-dependent and independent effects of periodontopathic bacteria on threatened preterm labor and preterm birth

PURPOSE

Periodontal disease is considered to be a risk factor for threatened preterm labor (TPL) and preterm birth (PB), but pathogenic mechanisms have not yet been elucidated. We hypothesized that infection with periodontopathic bacteria may enhance thrombosis through molecular mimicry with TLRVYK peptides on beta-2 glycoprotein I, a target molecule in anti-phospholipid syndrome. This study aimed to examine the effects of periodontitis on TPL and PB.

METHODS

Ninety-five pregnant women (47 TPL and 48 healthy subjects) participated. Periodontal clinical parameters and periodontopathic bacteria were examined. Molecular mimicry between TLRVYK peptides and homologous peptides on the periodontopathic bacteria was examined by enzyme-linked immunosorbent assay (ELISA) using rabbit polyclonal antibodies specific for the respective peptides (SIRVYK on Aggregatibacter actinomycetemcomitans, TLRIYT on Porphyromonus gingivalis, and TLALYK on Treponema denticola). Serum high-sensitivity C-reactive protein, anti-TLRVYK and anti-SIRVYK IgG antibodies were measured using ELISA.

RESULTS

Among the rabbit antibodies specific for the bacterial homologous peptides, only anti-SIRVYK IgG antibody reacted with TLRVYK peptides. Multivariable analysis showed that anti-SIRVYK IgG antibody was significantly associated with diagnosis of TPL. Of 95 births, 14 (14.7 %) delivered preterm. The preterm birth rate was higher in the anti-SIRVYK IgG antibody >median group than in the ≤median group. Of the 47 TPL subjects 13 had PB, and ordinal logistic regression analysis revealed that past smoking, presence of P. gingivalis and anti-SIRVYK IgG antibody were significantly correlated with PB.

CONCLUSIONS

Infection with P. gingivalis and the antibody response to SIRVYK might be associated with TPL and PB.

Infections and vaccines in the etiology of antiphospholipid syndrome

PURPOSE OF REVIEW

To present scientific evidence supporting the infectious origin for the antiphospholipid syndrome (APS) by molecular mimicry between pathogens, infection and vaccination with β2-glycoprotein I (β2-GPI) molecule.

RECENT FINDINGS

APS is characterized by the presence of pathogenic autoantibodies against β2-GPI. The infection etiology of APS was well established. Likewise, a link between vaccination such as tetanus toxoid may trigger antibodies targeting tetanus toxoid and β2-GPI, due to molecular mimicry between the two molecules. During the years, the pathogenic potential of anti-tetanus toxoid antibodies cross reactive with β2-GPI were found to be pathogenic in animal models, inducing experimental APS.

SUMMARY

Accumulated evidence supports that the presence of anti-β2-GPI antibodies is associated with a history of infections and the main mechanism to explain this correlation is molecular mimicry. The relationship between tetanus toxoid vaccination and APS reveals a novel view on the autoimmune/autoinflammatory syndrome induced by adjuvants (ASIA).

Th1/Th2/Th17/Treg expression in cultured PBMCs with antiphospholipid antibodies

The aim of this study was to evaluate the expression of T-helper cell subtypes Th1, Th2, Th17 and Treg in antiphospholipid syndrome (APS), and whether they are related to anti-cardiolipin antibody (aPL) titers. Peripheral mononuclear cells (PBMCs) were isolated from healthy donors, and incubated with aPLs. Subsequent to a 48‑h incubation, PBMCs were collected and detected by flow cytometry. The results revealed that aPLs at higher concentrations may induce a significant increase in Th2 and Th17 frequencies, as opposed to a significant decrease in Th1 and Treg frequencies and the Th1/Th2 ratio. These results indicate that there is a Th1/Th2 imbalance, a Th17 upregulation and a Treg downregulation present in APS, and that these factors are positively correlated with aPL titers, suggesting a potential role of Th cells in the pathogenesis of APS.

Adjuvant immunization induces high levels of pathogenic antiphospholipid antibodies in genetically prone mice: another facet of the ASIA syndrome

Adjuvants may induce autoimmune diseases in susceptible individuals, a phenomenon recently defined as autoimmune/inflammatory syndrome induced by adjuvants (ASIA). Patients with both antiphospholipid antibodies (aPL) and the genetic coagulopathy factor V Leiden (FVL) are frequently found. We therefore evaluated whether adjuvant can induce aPL in heterozygous FVL mice. aPL were measured in naïve mice and at 1 and 5 months after immunization with either complete or incomplete Freund's adjuvant (CFA, IFA) in FVL and control C57/B6 background mice. We defined antibody levels 3 SD above the mean of C57/B6 mice immunized with adjuvant as positive (specificity of 99%). For β(2)GPI-dependent aPL, 28.6% (6/21) of FVL mice 5 months after immunization with adjuvant (both IFA and CFA) were positive compared with 4.8% (1/22) of FVL mice 1 month after adjuvant and 0% of naïve FVL and C57/B6 mice (0/16, p < 0.001). aPL levels correlated with behavioral hyperactivity in the staircase test. FVL mice immunized with adjuvant did not develop β(2)GPI-independent aPL. We hypothesize that the FVL aPL association is not a coincidence, but that chronic coagulation defects combined with external inflammatory stimuli analogous to adjuvant may induce aPL and also antiphospholipid syndrome, thus supporting the notion of ASIA.

Significant changes in the levels of secreted cytokines in brains of experimental antiphospholipid syndrome mice

Antiphospholipid syndrome (APS) is characterized by thromboses and neuropsychiatric manifestations possibly linked to brain inflammation. In order to examine the levels of proinflammatory and anti-inflammatory cytokines in experimental APS (eAPS) mice brains, we measured the levels of TNF-α, IFN-γ, and IL-10 in brain homogenates (cytosolic fractions) and in brain slices (secreted level) at 6, 15, and 24 weeks after immunization. We induced eAPS by immunization of Balb/c mice with β(2)-glycoprotein I (β(2)GPI), the major autoantigen in the disease and controls with adjuvant alone. We found increased levels of secreted TNF-α in eAPS mice for the entire experiment period. Cytosolic and secreted IL-10 and IFN-γ levels in eAPS mice were lower at 6 and 15 weeks and higher at 24 weeks after immunization. The results suggest that brain disease in APS is associated with significant and complex changes in proinflammatory and anti-inflammatory cytokines.

In vivo distribution of β2 glycoprotein I under various pathophysiologic conditions

In vitro studies have documented β2 glycoprotein I (β2GPI) binding to endothelial cells (ECs) and trophoblast using antiphospholipid antibodies. The in vivo binding of β2GPI to these cells and the conditions that favor their interaction have not been investigated. We analyzed the in vivo distribution of cyanine 5.5-labeled β2GPI in mice and evaluated the effect of pregnancy and circulating antibodies on its tissue localization. The signal was detected in the liver by whole body scan and ex vivo analysis. The β2GPI failed to bind to the vascular endothelium and reacted only with the ECs of uterine vessels. In pregnant mice the protein was localized on ECs and trophoblast at the embryo implantation sites. Immunized mice showed a similar β2GPI biodistribution to naive mice but the immunized pregnant animals exhibited a significant increase in fetal loss associated with C3 and C9 deposition at the implantation sites. Treatment of mice with LPS after β2GPI-Cy5.5 injection promoted protein localization on gut and brain ECs associated with IgG, C1q, and C9 deposition in immunized mice. These findings indicate that β2GPI binding to EC requires priming with pro-inflammatory factors which is not needed for uterine and placental localization probably dependent on hormonal changes.

Reproductive immunology: current status and future directions (part I)

Extensive research work over the past couple of decades has indicated a series of intricate relations between immune and reproductive systems. A range of reproductive immunology topics including the roles of adoptive and innate immunity in infertility and pregnancy, the immune system's role in induction of labor and preterm delivery, and immuno-modulatory effects of the female sex hormones will be discussed in this and the next issue of the Journal. The implications of this research on the development of novel therapeutic approaches are also addressed.

Prevalence of anticardiolipin antibodies in pregnancies with history of repeated miscarriages

AIM

This study aimed at evaluating the prevalence of high anticardiolipin antibody and lupus anticoagulant levels in women with histories of at least two miscarriages.

METHODS

The presence of high anticardiolipin antibody and lupus anticoagulant levels were evaluated in 52 patients with ages between 17 and 41 (mean 26.7 years old) who had histories of repeated miscarriages.

RESULTS

High anticardiolipin antibody levels were identified in 55.77% and lupus anticoagulant levels in 2% of the individuals.

CONCLUSION

In conclusion, women who suffer from repeated miscarriages present with a high prevalence of anticardiolipin antibodies. Further studies on this issue are crucial as these antibodies are associated with hypercoagulability and thus increased the risk of thromboembolic events.

The neonatal Fc receptor as therapeutic target in IgG-mediated autoimmune diseases

Therapy approaches based on lowering levels of pathogenic autoantibodies represent rational, effective, and safe treatment modalities of autoimmune diseases. The neonatal Fc receptor (FcRn) is a major factor regulating the serum levels of IgG antibodies. While FcRn-mediated half-life extension is beneficial for IgG antibody responses against pathogens, it also prolongs the serum half-life of IgG autoantibodies and thus promotes tissue damage in autoimmune diseases. In the present review article, we examine current evidence on the relevance of FcRn in maintaining high autoantibody levels and discuss FcRn-targeted therapeutic approaches. Further investigation of the FcRn-IgG interaction will not only provide mechanistic insights into the receptor function, but should also greatly facilitate the design of therapeutics combining optimal pharmacokinetic properties with the appropriate antibody effector functions in autoimmune diseases.

Pathogenetic potential of antiphospholipid antibodies

Antiphospholipid antibodies are autoantibodies that recognize phospholipid-binding proteins such as beta2 glycoprotein (beta2GP)-I, prothrombin or annexins. These antibodies have been associated with arterial or venous thrombotic events and pregnancy morbidity. The molecular mechanisms responsible for the pathogenetic potential of these antibodies include: resistance to activated protein C, acquired Factor XII deficiency resulting in suppression of intrinsic fibrinolytic activity, activation of endothelial cells through the nuclear factor kappaB pathway leading to tissue factor upregulation, adhesion molecule and cytokine expression and activation of platelets. Opposite effects, such as the potentiation of the inhibitory action of beta2GPI on the activation of Factor XI, make the dynamics of the interaction of these antibodies with the coagulation system rather complex. Many of the above functions can be mediated by signaling through molecules of the tumor necrosis factor receptor family, such as CD40, which is recognized by purified anti-beta2GPI antibodies.

Common infectious agents prevalence in antiphospholipid syndrome

Antiphospholipid syndrome is characterized by thrombosis and pregnancy loss. Infections are generally associated with autoimmune diseases, but in the setting of antiphospholipid syndrome this link has been suggested as having a pathogenic role. In this study, 98 patients with antiphospholipid syndrome were screened for antibodies directed to several infectious agents. The main finding in this study is the significantly higher prevalence of IgM antibodies to toxoplasma and rubella. This novel finding suggests that these infections might be associated with antiphospholipid syndrome. As autoimmune diseases and, in particular, antiphospholipid syndrome are associated with infections, mainly the catastrophic type of the syndrome, this finding implies that a current infection with these agents, i.e. toxoplasma and rubella, might either be related to the pathogenesis of antiphospholipid syndrome or alternatively to its manifestations. Lupus (2009) 18, 1149—1153.

Mechanisms of antiphospholipid antibody-associated pregnancy complications

Women with antiphospholipid syndrome (APS) and antiphospholipid antibodies (aPL) are at high risk for recurrent spontaneous miscarriage and late pregnancy complications, such as preeclampsia and preterm labor. Recent clinical and experimental observations suggest that the pathophysiology of pregnancy failure in patients with APS may involve inflammation at the maternal-fetal interface and disruption of normal trophoblast function and survival, rather than a pro-thrombotic event. While treatment with heparin and aspirin from early pregnancy has been shown to significantly increase the live birth rate in recurrent miscarriage patients with APS, the incidence of severe late pregnancy complications still remains high. This review will discuss what is currently known about the mechanisms by which aPL may compromise pregnancy outcome.

Antiphospholipid antibodies induce a pro-inflammatory response in first trimester trophoblast via the TLR4/MyD88 pathway

PROBLEM

Women with antiphospholipid antibodies (aPL) are at risk for recurrent miscarriage, pre-eclampsia, and pre-term labor. aPL target the placenta directly by binding to beta(2)-glycoprotein I (beta(2)GPI) expressed on the surface of trophoblast cells. The objective of this study was to determine the effects of aPL on trophoblast function and the mechanisms involved.

METHOD OF STUDY

First trimester trophoblast cells were treated with anti-beta(2)GPI monoclonal antibodies and patient-derived aPL, after which cell survival and function was evaluated.

RESULTS

We report that anti-beta(2)GPI antibodies trigger an inflammatory response in trophoblast, characterized by increased secretion of interleukin (IL)-8, MCP-1, GRO-alpha, and IL-1beta, and that this occurs in a TLR-4/MyD88-dependent manner. At high concentrations, these antibodies also induce caspase-mediated cell death. This was attenuated upon disabling of the MyD88 pathway, suggesting that anti-beta(2)GPI-induced inflammatory mediators compromise trophoblast survival by acting in an autocrine/paracrine manner. Enhanced IL-8, GRO-alpha, and IL-1beta secretion also occurred when trophoblast cells were incubated with antibodies from patients with antiphospholipid syndrome. Heparin, which acts as a pro-survival factor in human trophoblast, attenuated the anti-beta(2)GPI antibody-mediated cell death, and also the pro-inflammatory response, but only at high concentrations.

CONCLUSION

These findings demonstrate that aPL triggers a placental inflammatory response via the TLR-4/MyD88 pathway, which in turn compromises trophoblast survival. Thus, the TLR-4/MyD88 pathway may provide a new therapeutic target to improve pregnancy outcome in antiphospholipid syndrome patients.

Antiphospholipid syndrome induction exacerbates a transgenic Alzheimer disease model on a female background

The antiphospholipid syndrome (APS) is characterized by antiphospholipid antibodies (aPL) and vascular brain disease which is often associated with dementia. We examined the neurodegenerative pathological processes underlying APS by inducing APS in a transgenic animal model of Alzheimer's disease. Female C57B6/SJL mice carrying the APP(695)SWE mutation (Tg2576) and wild-type (wt) controls were immunized with β₂-glycoprotein-I (APS mice) or adjuvant alone (controls) at 4 months of age. At the age of 8 months the APP-APS mice developed high levels of aPL associated with motor hypoactivity in a staircase test (p<0.03 by t-test) and impaired performance in the cognitive T-maze (p<0.02 for main effect of treatment by repeated measures ANOVA) relative to APP-CFA mice and controls. wt-APS and wt-control did not differ significantly in their behavior or cognition. Histological studies revealed mature plaques only in the APP-APS group which also had higher amyloid load and number of activated microglia compared to all other groups. The results indicate a significant interaction between APP genotype and the induction of APS on a female background. The mechanisms involved may also be important in human APS-AD co-morbidity.

Antiphospholipid antibodies: laboratory and pathogenetic aspects

Antiphospholipid antibodies (aPL) constitute a heterogeneous group of autoantibodies that share the ability to bind phospholipids (PL) alone, protein-PL complexes, or PL-binding proteins. They have been detected in isolation, in association with autoimmune diseases such as systemic lupus erythematosus (SLE), and during the course of different infections. aPL have been associated with an array of clinical manifestations in virtually every organ, although deep vein and arterial thrombosis as well as pregnancy morbidity are predominant. The co-occurrence of these clinical findings with aPL constitutes the so-called antiphospholipid syndrome (APS). aPL can be detected by immunological methods [e.g., anticardiolipin antibodies (aCL)] or by functional methods that exploit the effect of aPL on blood coagulation [lupus anticoagulant (LA)]. Since aPL are heterogeneous, numerous immunological and coagulation assays have been developed. These assays have not been fully standardized, and, therefore, problems such as high interlaboratory variation are relatively frequent. Recently, recommendations have been published regarding LA and aCL testing. Not all aPL are pathogenic. However, when they are not associated with infections, they have a role in the pathogenesis of APS. Clinical and experimental data have shown that aPL exert their pathogenic activity by interfering with the function of coagulation factors, such as thrombin and factors X, XI and XII, and with the function of anticoagulant proteins of the protein C system. In addition, aPL interaction with platelets and endothelial cells induces a pro-adhesive activated phenotype.