Autoantibody response to the Ro/La particle may predict outcome in neonatal lupus erythematosus

Systemic Diseases and Heart Block

Systemic diseases can cause heart block owing to the involvement of the myocardium and thereby the conduction system. Younger patients (<60) with heart block should be evaluated for an underlying systemic disease. These disorders are classified into infiltrative, rheumatologic, endocrine, and hereditary neuromuscular degenerative diseases. Cardiac amyloidosis owing to amyloid fibrils and cardiac sarcoidosis owing to noncaseating granulomas can infiltrate the conduction system leading to heart block. Accelerated atherosclerosis, vasculitis, myocarditis, and interstitial inflammation contribute to heart block in rheumatologic disorders. Myotonic, Becker, and Duchenne muscular dystrophies are neuromuscular diseases involving the myocardium skeletal muscles and can cause heart block.

Systemic Diseases and Heart Block

Systemic diseases can cause heart block owing to the involvement of the myocardium and thereby the conduction system. Younger patients (<60) with heart block should be evaluated for an underlying systemic disease. These disorders are classified into infiltrative, rheumatologic, endocrine, and hereditary neuromuscular degenerative diseases. Cardiac amyloidosis owing to amyloid fibrils and cardiac sarcoidosis owing to noncaseating granulomas can infiltrate the conduction system leading to heart block. Accelerated atherosclerosis, vasculitis, myocarditis, and interstitial inflammation contribute to heart block in rheumatologic disorders. Myotonic, Becker, and Duchenne muscular dystrophies are neuromuscular diseases involving the myocardium skeletal muscles and can cause heart block.

Prenatal predisposing factors associated with neonatal lupus erythematosus

OBJECTIVES

To identify the prenatal predisposing factors related to neonatal lupus erythematosus (NLE).

MATERIALS AND METHODS

A retrospective case-control study was made of 131 pregnant women with positive anti-Ro or anti-La autoantibodies and known neonatal outcomes between January 2002 and December 2019 at Siriraj Hospital, Bangkok, Thailand. There were 101 unaffected neonates and 30 NLE cases confirmed postnatally. Demographic and clinical data of the mothers and neonates with and without NLE were statistically compared.

RESULTS

NLE was diagnosed in 30 out of 131 cases. A multivariate analysis identified the following significant factors for NLE: maternal anti-La antibodies (odds ratio (OR), 3.591; p = 0.030); and maternal treatment with either hydroxychloroquine (OR, 0.082; p = 0.001) or prednisolone (OR, 0.136; p = 0.017). Of the significant variables examined in the multivariate analysis models, high levels of maternal anti-La antibodies were found to be the strongest predictor of noncardiac NLE (OR, 4.558; p = 0.032), while a female baby was significantly higher in pregnancies complicated by cardiac NLE (OR, 5.374; p = 0.046). Hydroxychloroquine still provided a protective effect for both cardiac and noncardiac NLE (p = 0.039 and 0.032, respectively).

CONCLUSIONS

The maternal anti-La antibodies were a beneficial predictor for NLE, especially as their high titers were influentially associated with noncardiac features. A female fetus seemed to present an increased risk for developing a congenital heart block. Nevertheless, the treatment with hydroxychloroquine during the pregnancies demonstrated a potentially protective factor against both cardiac and noncardiac manifestations.

Systemic Diseases and Heart Block

Systemic diseases can cause heart block owing to the involvement of the myocardium and thereby the conduction system. Younger patients (<60) with heart block should be evaluated for an underlying systemic disease. These disorders are classified into infiltrative, rheumatologic, endocrine, and hereditary neuromuscular degenerative diseases. Cardiac amyloidosis owing to amyloid fibrils and cardiac sarcoidosis owing to noncaseating granulomas can infiltrate the conduction system leading to heart block. Accelerated atherosclerosis, vasculitis, myocarditis, and interstitial inflammation contribute to heart block in rheumatologic disorders. Myotonic, Becker, and Duchenne muscular dystrophies are neuromuscular diseases involving the myocardium skeletal muscles and can cause heart block.

Identification of a unique anti-Ro60 subset with restricted serological and molecular profiles

Anti-Ro60 is one of the most common and clinically important serum autoantibodies that has a number of diagnostic and predictive capabilities. Most diagnostic laboratories report this simply as a qualitative positive/negative result. The objective of this study was to examine the clinical and serological relevance of a novel subset of anti-Ro60 in patients who display low levels of anti-Ro60 (anti-Ro60low ). We retrospectively identified anti-Ro60 sera during a 12-month period at a major immunopathology diagnostic laboratory in Australia. These all were anti-Ro60-precipitin-positive on the diagnostic gold standard counter-immuno-electrophoresis (CIEP). Lineblot immunoassay was used to stratify patients into either anti-Ro60low or anti-Ro60high subsets. We compared the medical and laboratory parameters associated with each group. Enzyme-linked immunosorbent assay (ELISA) and mass spectrometry techniques were used to analyse the serological and molecular basis behind the two subsets. Anti-Ro60low patients displayed less serological activity than anti-Ro60high patients with less intermolecular spreading, hypergammaglobulinaemia and less tendency to undergo anti-Ro60 isotype-switching than anti-Ro60high patients. Mass spectrometric typing of the anti-Ro60low subset showed restricted variable heavy chain subfamily usage and amino acid point mutations. This subset also displayed clinical relevance, being present in a number of patients with systemic autoimmune rheumatic diseases (SARD). We identify a novel anti-Ro60low patient subset that is distinct from anti-Ro60high patients serologically and molecularly. It is not clear whether they arise from common or separate origins; however, they probably have different developmental pathways to account for the stark difference in immunological maturity. We hence demonstrate significance to anti-Ro60low and justify accurate detection in the diagnostic laboratory.

The clinical spectrum of autoimmune congenital heart block

Autoimmune congenital heart block (CHB) is an immune-mediated acquired disease that is associated with the placental transference of maternal antibodies specific for Ro and La autoantigens. The disease develops in a fetal heart without anatomical abnormalities that could otherwise explain the block, and which is usually diagnosed in utero, but also at birth or within the neonatal period. Autoantibody-mediated damage of fetal conduction tissues causes inflammation and fibrosis and leads to blockage of signal conduction at the atrioventricular (AV) node. Irreversible complete AV block is the principal cardiac manifestation of CHB, although some babies might develop other severe cardiac complications, such as endocardial fibroelastosis or valvular insufficiency, even in the absence of cardiac block. In this Review, we discuss the epidemiology, classification and management of women whose pregnancies are affected by autoimmune CHB, with a particular focus on the autoantibodies associated with autoimmune CHB and how we should test for these antibodies and diagnose this disease. Without confirmed effective preventive or therapeutic strategies and further research on the aetiopathogenic mechanisms, autoimmune CHB will remain a severe life-threatening disorder.

Neonatal Lupus erythematosus Following Rheumatoid Arthritis: Case Report and Literature Review

BACKGROUND

Neonatal lupus erythematosus (NLE) is a transient autoimmune disease of developing fetus and neonate in mothers with systemic lupus erythematosus (SLE). In this report we introduce an infant with NLE whose mother had rheumatoid arthritis.

CASE PRESENTATION

Our case was a 40 day old male infant with discoid-like and annular skin lesions over forehead and neck, irritability and low grade fever. There was a history of prematurity due to preeclampsia. There was no cytopenia or cardiac involvement but liver enzymes were more than 5-fold increased. FANA, Anti Ro and La were negative. The mother had a history of un-controlled rheumatoid arthritis for 12 years with deformity in metacarpal and PIP and ulnar deviation in hands. FANA=1/640 and anti-SSB/La was positive in the mother but there was no other clinical and paraclinical sign of SLE. Without any treatment and during months, the skin and mucosal lesions gradually disappeared without any scar and liver enzymes reached the normal level. After 6 months follow up, he was symptom free with normal growth and development.

CONCLUSION

We recommend to check anti SSA/Ro and anti SSB/La antibodies in all pregnant women with connective tissue diseases to prevent life-threatening involvement of the infant.

The HLA locus contains novel foetal susceptibility alleles for congenital heart block with significant paternal influence

OBJECTIVE

The main aim of this study was to identify foetal susceptibility genes on chromosome six for Ro/SSA autoantibody-mediated congenital heart block.

SUBJECTS AND DESIGN

Single nucleotide polymorphism (SNP) genotyping of individuals in the Swedish Congenital Heart Block (CHB) study population was performed. Low-resolution HLA-A, -Cw and -DRB1 allele typing was carried out in 86 families comprising 339 individuals (86 Ro/SSA autoantibody-positive mothers, 71 fathers, 87 CHB index cases and 95 unaffected siblings).

RESULTS

A case-control comparison between index cases and population-based out-of-study controls (n = 1710) revealed association of CHB with 15 SNPs in the 6p21.3 MHC locus at a chromosome-wide significance of P < 2.59 × 10(-6) (OR 2.21-3.12). In a family-based analysis of association of SNP markers as well as distinct MHC class I and II alleles with CHB, HLA-DRB1*04 and HLA-Cw*05 variants were significantly more frequently transmitted to affected individuals (P < 0.03 and P < 0.05, respectively), whilst HLA-DRB1*13 and HLA-Cw*06 variants were significantly less often transmitted to affected children (P < 0.04 and P < 0.03). We further observed marked association of increased paternal (but not maternal) HLA-DRB1*04 transmission to affected offspring (P < 0.02).

CONCLUSIONS

HLA-DRB1*04 and HLA-Cw*05 were identified as novel foetal HLA allele variants that confer susceptibility to CHB in response to Ro/SSA autoantibody exposure, whilst DRB1*13 and Cw*06 emerged as protective alleles. Additionally, we demonstrated a paternal contribution to foetal susceptibility to CHB for the first time.

Congenital heart block maternal sera autoantibodies target an extracellular epitope on the α1G T-type calcium channel in human fetal hearts

BACKGROUND

Congenital heart block (CHB) is a transplacentally acquired autoimmune disease associated with anti-Ro/SSA and anti-La/SSB maternal autoantibodies and is characterized primarily by atrioventricular (AV) block of the fetal heart. This study aims to investigate whether the T-type calcium channel subunit α1G may be a fetal target of maternal sera autoantibodies in CHB.

METHODOLOGY/PRINCIPAL FINDINGS

We demonstrate differential mRNA expression of the T-type calcium channel CACNA1G (α1G gene) in the AV junction of human fetal hearts compared to the apex (18-22.6 weeks gestation). Using human fetal hearts (20-22 wks gestation), our immunoprecipitation (IP), Western blot analysis and immunofluorescence (IF) staining results, taken together, demonstrate accessibility of the α1G epitope on the surfaces of cardiomyocytes as well as reactivity of maternal serum from CHB affected pregnancies to the α1G protein. By ELISA we demonstrated maternal sera reactivity to α1G was significantly higher in CHB maternal sera compared to controls, and reactivity was epitope mapped to a peptide designated as p305 (corresponding to aa305-319 of the extracellular loop linking transmembrane segments S5-S6 in α1G repeat I). Maternal sera from CHB affected pregnancies also reacted more weakly to the homologous region (7/15 amino acids conserved) of the α1H channel. Electrophysiology experiments with single-cell patch-clamp also demonstrated effects of CHB maternal sera on T-type current in mouse sinoatrial node (SAN) cells.

CONCLUSIONS/SIGNIFICANCE

Taken together, these results indicate that CHB maternal sera antibodies readily target an extracellular epitope of α1G T-type calcium channels in human fetal cardiomyocytes. CHB maternal sera also show reactivity for α1H suggesting that autoantibodies can target multiple fetal targets.

Detection of autoantibodies in a point-of-care rheumatology setting

Autoimmune rheumatic diseases are common and confront society with serious medical, social, and financial burdens imposed by their debilitating nature. Many autoimmune diseases are associated with a particular set of autoantibodies, which have emerged as highly useful to define and classify disease, predict flares, or monitor efficacy of therapy. However, current practice for monitoring autoantibodies is protracted, labor-intensive, and expensive. This review provides an overview on the value of point-of-care (POC) biosensor technology in the diagnosis and management of patients with autoimmune rheumatic diseases. Real-time measurement of autoantibodies will clearly benefit the rheumatology practice in emergency and urgent care settings, where definitive diagnosis is essential for initiation of correct critical care therapy. Immediate serological information in clinic will provide considerable value for long-term patient care and an opportunity for an instant, result-deduced therapeutic action, avoiding delays and improving compliance, especially in field-based and remote areas. We describe the particular autoantibodies that are useful disease and activity markers and would, therefore, be attractive to POC applications. Already existing biosensors and platforms that show promise for autoantibody testing are summarized and comparatively evaluated. As POC assessment is gaining momentum in several areas of patient care, we propose that rheumatology is poised to benefit from this innovative and affordable technology.

Congenital heart block: evidence for a pathogenic role of maternal autoantibodies

During pregnancy in autoimmune conditions, maternal autoantibodies are transported across the placenta and may affect the developing fetus. Congenital heart block (CHB) is known to associate with the presence of anti-Ro/SSA and anti-La/SSB antibodies in the mother and is characterized by a block in signal conduction at the atrioventricular (AV) node. The mortality rate of affected infants is 15% to 30%, and most live-born children require lifelong pacemaker implantation. Despite a well-recognized association with maternal anti-Ro/La antibodies, CHB develops in only 1% to 2% of anti-Ro-positive pregnancies, indicating that other factors are important for establishment of the block. The molecular mechanisms leading to complete AV block are still unclear, and the existing hypotheses fail to explain all aspects of CHB in one comprehensive model. In this review, we discuss the different specificities of maternal autoantibodies that have been implicated in CHB as well as the molecular mechanisms that have been suggested to operate, focusing on the evidence supporting a direct pathogenic role of maternal antibodies. Autoantibodies targeting the 52-kDa component of the Ro antigen remain the antibodies most closely associated with CHB. In vitro experiments and animal models of CHB also point to a major role for anti-Ro52 antibodies in CHB pathogenesis and suggest that these antibodies may directly affect calcium regulation in the fetal heart, leading to disturbances in signal conduction or electrogenesis or both. In addition, maternal antibody deposits are found in the heart of fetuses dying of CHB and are thought to contribute to an inflammatory reaction that eventually induces fibrosis and calcification of the AV node, leading to a complete block. Considering that CHB has a recurrence rate of 12% to 20% despite persisting maternal autoantibodies, it has long been clear that maternal autoantibodies are not sufficient for the establishment of a complete CHB, and efforts have been made to identify additional risk factors for this disorder. Therefore, recent studies looking at the influence of genetic and environmental factors will also be discussed.

A population-based investigation of the autoantibody profile in mothers of children with atrioventricular block

The objective of the study was to investigate the antigen specificity and occurrence of individual autoantibodies in mothers of children diagnosed with atrioventricular (AV) block in a nation-wide setting. Patients with AV block detected before 15 years of age were identified using national quality registries as well as a network of pediatric and adult cardiologists and rheumatologists at the six university hospitals in Sweden. Patients with gross heart malformations, surgically or infectiously induced blocks were excluded. Blood samples were obtained from the mothers and maternal autoantibody profile, including the occurrence of antibodies against Ro52, Ro60, La, SmB, SmD, RNP-70k, RNP-A, RNP-C, CENP-C, Scl-70, Jo-1, ribosomal RNP and histones was investigated in 193 mothers of children with AV block by immunoblotting and ELISA. Autoantibody reactivity was detected in 48% (93/193) of the mothers of children with AV block. In autoantibody-positive mothers, the vast majority, 95% (88/93), had antibodies against Ro52, while 63% (59/93) had autoantibodies to Ro60 and 58% (54/93) had autoantibodies to La. In addition, 13% (12/93) of the autoantibody-positive mothers had antibodies to other investigated antigens besides Ro52, Ro60 and La, and of these anti-histone antibodies were most commonly represented, detected in 8% (7/93) of the mothers. In conclusion, this Swedish population-based study confirms that maternal autoantibodies may associate with heart block in the child. Further, our data demonstrate a dominant role of Ro52 antibodies in association with AV block.

Non-cardiac manifestations of neonatal lupus erythematosus

Neonatal lupus erythematosus (NLE) is characterized by the transplacental passage of maternal anti-Ro and/or anti-La antibodies and characteristic illnesses in the foetus/neonate. Most attention has focused on the most serious complication- cardiac involvement. This article will focus on non-cardiac involvement. Skin involvement (cutaneous NLE) is present in 15-25% of children with NLE. The rash of NLE tends to be photosensitive but may be present at birth or in non-sun exposed areas. It is most frequently seen around the eyes, not in the malar area, but also occurs in other parts of the body. The pathology resembles the rash of subacute cutaneous lupus erythematosus. Anti-Ro antibodies are present in >95% with the remaining mothers having anti-U1RNP antibodies only. Asymptomatic elevation of liver function tests, which may be associated with evidence of cholestasis, is seen in 10-25% of cases of NLE. Mild hepatomegaly and less commonly splenomegaly may be present. Liver involvement seen in isolation or associated with other features. The pathology resembles idiopathic neonatal giant cell hepatitis. Any haematological lineage, neutropenia and thrombocytopenia most commonly, may be affected by NLE. Haematological involvement is almost always asymptomatic. There are protean manifestations of neurologic involvement in NLE: hydrocephalus, non-specific white matter changes, calcification of the basal ganglia and a 'vasculopathy'. The most unusual feature of NLE is the radiographic finding of stippling of the epiphyses (chondrodysplasia punctata). Overall, non-cardiac involvement of NLE is more common than cardiac. The study of these manifestations may lead to new insight into how autoantibodies lead to disease.

Autoantibodies associated with congenital heart block

Congenital heart block is the most severe manifestation of neonatal lupus syndrome. It is a passively acquired disease where transplacental passage of maternal autoantibodies is associated with irreversible damage of the foetal cardiac conduction system. It is well established that the condition, in the absence of structural abnormalities, is strongly associated with maternal autoantibodies to the Ro/La antigens. More specifically the disease has been closely linked to antibodies to the Ro52 component of the antigen complex. Congenital heart block constitutes a unique model where specific autoantibodies target and mediate organ-specific disease. A wide panel of maternal antibodies has been discussed in literature in association with the disease and are described in this review.

The benefits of transplacental treatment of isolated congenital complete heart block associated with maternal anti-Ro/SSA antibodies: a review

Isolated congenital complete atrio-ventricular block (CAVB) is associated with the transplacental passage of maternal autoantibodies directed to foetal Ro/SSA ribonucleoproteins. Their interactions most likely trigger the inflammation of the atrio-ventricular node and the myocardium in susceptible foetuses. The inflamed tissues may then heal with fibrosis that may cause heart block, endocardial fibroelastosis, and dilated cardiomyopathy. CAVB, the most common cardiac complication, typically develops between 18 and 24 gestational weeks. Untreated, the condition carries a significant mortality risk as the foetus needs to overcome the sudden drop in ventricular rate, the loss of normal atrial systolic contribution to ventricular filling, and perhaps concomitant myocardial inflammation and fibrosis. The rationale to treat a foetus at the stage of CAVB is primarily to mitigate myocardial inflammation and to augment foetal cardiac output. Maternal dexamethasone administration has been shown to improve incomplete foetal AV block, myocardial dysfunction, and cavity effusions. Beta-sympathomimetics may be useful to increase the foetal heart rate and myocardial contractility. Published data from our institution suggest an improved survival >90% if maternal high-dose dexamethasone was initiated at the time of CAVB detection and maintained during the pregnancy and if a beta-adrenergic drug was added at foetal heart rates below 55 beats/min. Despite the improvement in outcome, there is an ongoing debate about treatment-related risks. In this review, we will appraise the natural history of untreated CAVB, discuss currently available management options, and examine the results and risks of in-utero treatment of antibody-mediated CAVB.

The importance of the level of maternal anti-Ro/SSA antibodies as a prognostic marker of the development of cardiac neonatal lupus erythematosus a prospective study of 186 antibody-exposed fetuses and infants

OBJECTIVES

The purpose of this study was to determine whether cardiac complications of neonatal lupus erythematosus (NLE) are related to maternal anti-Ro and anti-La autoantibody-levels.

BACKGROUND

Autoantibody-positive mothers are frequently referred for serial echocardiography because of the elevated fetal risk of developing immune-mediated heart block. Little is known why only some and not all offspring are affected.

METHODS

All cases referred since 2000 for serial fetal echocardiography or cardiac complications related to maternal antibodies were included. Patients without cardiac NLE (group 1) and with cardiac NLE (group 2) were compared. Antibody levels were measured by enzyme-linked immunosorbent assay with a cutoff value of 8 U/ml for a positive test result.

RESULTS

Group 1 included 146 serially screened fetuses with normal pregnancy outcomes. Group 2 consisted of 40 fetuses/neonates with a diagnosis of heart block or endocardial fibroelastosis or both, and included 4 fetuses diagnosed during serial screening. All cardiac complications were associated with moderate (>or=50 U/ml; 15%) or high (>or=100 U/ml; 85%) maternal anti-Ro levels, independently of anti-La antibody titres. The event rate of complete heart block was 5% for prospectively screened fetuses with Ro-values >or=50 U/ml (odds ratio: 7.8) and 0% for fetuses with lower titres (p < 0.0001). Infants with pre-natal exposure to high-titre anti-La levels >or=100 U/ml were the most likely to have noncardiac features of NLE (event rate: 57%; odds ratio: 4.7).

CONCLUSIONS

Our findings support that the amount of maternal antibodies, rather than their presence, is associated with fetal tissue injury. As anti-Ro levels correlate with the risk of cardiac complications, serial echocardiography should be limited to women with high anti-Ro-titres.

Antibodies to amino acid 200-239 (p200) of Ro52 as serological markers for the risk of developing congenital heart block

Maternal autoantibodies to the p200-epitope of Ro52 have been suggested to correlate with development of congenital heart block. The aim of the present study was to evaluate the clinical relevance and predictive value of p200-antibodies in high-risk pregnancies. Sera from 515 Finnish, Swedish and American women were included in the study. Sera originated from 202 mothers with an infant affected by second- or third-degree atrioventricular block (AVB), 177 mothers with rheumatic disease having infants with normal heart rate and female blood donors (n = 136). A novel serological assay for Ro52 p200-antibodies with intra- and inter-assay variability of 3% and 3.8% respectively was developed. Mothers of children affected by AVB II-III had significantly higher p200-antibody levels than mothers with rheumatic disease having children with normal heart rate (P < 0.001). In the Swedish cohort, a distinction between foetuses with normal conduction, AVB I, AVB II and III was possible. A significant difference in anti-p200 levels between AVB I and AVB II-III groups compared with foetuses with normal conduction (P < 0.05 and P < 0.01) was observed. Using p200-antibodies as a second step analysis in Ro52-positive pregnancies increased the positive predictive value for foetal cardiac involvement (AVB I, II or III) from 0.39 (0.27-0.51) to 0.53 (0.37-0.68). In conclusion, Ro52 p200-antibodies may occur in women with unaffected children, but levels are significantly higher in mothers of children with congenital heart block and are suggested as a relevant marker in evaluating the risk for foetal AV block.

Infants born to mothers with anti-SSA/Ro autoantibodies: neonatal outcome and follow-up

Neonatal lupus syndrome is considered a model of passively acquired autoimmune disease. The first 10 newborns born to mothers with connective tissue disease and positive for anti-SSA/Ro antibodies enrolled in a follow-up program to evaluate the incidence of cardiac, hepatobiliary, hematologic, echoencephalographic, and cutaneous manifestations until 9 months of age are described in this study. No congenital heart block was observed, but only transient rhythm alterations were observed. In all, 1 infant showed typical neonatal lupus syndrome skin lesions at 3 months of age. During the neonatal period, echoencephalographic alterations were found more frequently, whereas at follow-up, hepatic and hematologic alterations were more often observed. In all, 1 baby showed persistent neutropenia. A standard program that enrolls all infants born to mothers with anti-SSA/Ro autoantibodies, who are at risk of developing neonatal lupus syndrome, should also include tests performed some time after birth, as a number of clinical manifestations might appear at a late stage.

Neonatal lupus syndromes

Neonatal lupus has become an important model of passively acquired autoimmunity since the seminal observation in the late 1970s that sera from nearly all mothers of children with isolated congenital heart block (CHB) contain specific autoantibodies.

Structurally derived mutations define congenital heart block-related epitopes within the 200-239 amino acid stretch of the Ro52 protein

Congenital heart block is a passively transferred autoimmune condition, which affects the children of mothers with Ro/SSA autoantibodies. During pregnancy, the antibodies are transported across the placenta and affect the fetus. We have previously demonstrated that antibodies directed to the 200-239 amino acid (aa) stretch of the Ro52 component of the Ro/SSA antigen correlate with the development of congenital heart block. In this report, we investigated the antibody-antigen interaction of this target epitope in detail at a molecular and structural level. Peptides representing aa 200-239 (p200) with structurally derived mutations were synthesized to define the epitopes recognized by two Ro52 human monoclonal antibodies, S3A8 and M4H1, isolated from patient-derived phage display libraries. Analyses by ELISA, circular dichroism and MALDI-TOF-MS demonstrate that the antibody recognition is dependent on a partly alpha-helical fold within the putative leucine zipper of the 200-239 aa stretch and that the two human anti-p200 monoclonal antibodies, M4H1 and S3A8, recognize different epitopic structures within the p200 peptide. In addition, we investigated the representation of each fine specificity within the sera of mothers with children born with congenital heart block, and in such sera, antibodies of the S3A8 idiotype were more commonly detected and at higher levels than M4H1-like antibodies.

Autoimmune-associated congenital heart block: dissecting the cascade from immunologic insult to relentless fibrosis

Few diseases exemplify the integration of research from bench to bedside as well as neonatal lupus, often described as a model of passively acquired autoimmunity. The signature histologic lesion of autoimmune congenital heart block (CHB) is fibrosis of the conducting tissue and, in some cases, the surrounding myocardium. Although anti-SSA/Ro-SSB/La antibodies are detected in > 85% of mothers whose fetuses are identified with conduction abnormalities in a structurally normal heart, the risk for a woman with the candidate antibodies to have a child with CHB is 2%. The mechanism by which maternal anti-SSA/Ro-SSB/La antibodies initiate and finally eventuate in atrioventricular nodal scarring is not yet defined, but it is clear that the antibodies alone are insufficient to cause disease and fetal factors are likely contributory. Previous in vitro and in vivo studies suggest that the pathologic cascade is initiated via apoptosis, resulting in translocation of SSA/Ro-SSB/La antigens to the cell surface where they are bound by maternal autoantibodies. Subsequently, the Fc portion of the bound immunoglobulin engages Fcgamma receptors on tissue macrophages, resulting in release of TGF-beta at a threshold favoring a profibrotic milieu and irreversible scarring. This cascade also involves tissue-specific activation of TGF-beta, which promotes the modulation of fibroblasts into myofibroblasts, a scarring phenotype. Recent findings point to genetic polymorphisms that promote high production of TGF-beta as possible fetal risk factors for CHB. Further elucidation of maternal and fetal contributory factors should provide insight into the pathogenesis of CHB and the rarity of irreversible injury.

Proposal for a new definition of congenital complete atrioventricular block

The classic old definition of congenital heart block by Yater (1929) is still generally accepted: 'Heart block established in a young patient. There must be some evidence of the existence of the slow pulse at a fairly early age and absence of a history of any infection which might cause the condition after birth: notably diphtheria, rheumatic fever, chorea and congenital syphilis'. However, other definitions are used. We systematically reviewed 1825 cases from 38 separate studies. We conclude that complete AV blocks detected in utero in the absence of structural abnormalities differ from blocks detected later in life with respect to pathogenesis (they are generally associated with maternal anti-Ro/SSA antibodies), poorer childhood prognosis, increased risk of developing late-onset dilated cardiomyopathy, different maternal clinical features and increased risk of recurrence in future pregnancies. For these reasons we propose a new modern definition of congenital complete AV block which might be acceptable to cardiologists, rheumatologists, pediatricians and obstetricians: 'an AV block is defined as congenital if it is diagnosed in utero, at birth or within the neonatal period (0-27 days after birth)'.

Incidence and spectrum of neonatal lupus erythematosus: a prospective study of infants born to mothers with anti-Ro autoantibodies

OBJECTIVE

Neonatal lupus erythematosus (NLE) is characterized by complete congenital heart block (CCHB), cutaneous rash, and laboratory abnormalities in infants born to mothers with autoantibodies directed against SSA/Ro, SSB/La, or both. We carried out a prospective study to determine the incidence of individual NLE features.

STUDY DESIGN

The study was performed in two centers: Toronto, Canada, and Milano, Italy. Mothers had been referred for the presence of anti-SSA/Ro autoantibodies, regardless of their diagnosis. All the children were seen at least once within the first 6 months of life for clinical evaluation and laboratory testing. The study group consisted of 128 infants born from 124 pregnancies in 112 women with anti-Ro antibodies with or without anti-La antibodies.

RESULTS

There were two cases of CCHB for an overall percentage of 1.6%. Twenty-one children (16%) developed cutaneous NLE. Laboratory testing showed hematologic abnormalities in 27% of the babies and elevation of liver enzymes in 26%.

CONCLUSIONS

Mothers with autoimmune diseases and anti-Ro antibodies are at risk of delivering a child with NLE but at a low risk of delivering a child with CCHB. Infants born to mothers with anti-Ro or anti-La antibodies should be monitored for other features of NLE in addition to CCHB.

Endocardial fibroelastosis associated with maternal anti-Ro and anti-La antibodies in the absence of atrioventricular block

OBJECTIVES

This study was designed to document the association of endocardial fibroelastosis (EFE) and maternal autoantibodies.

BACKGROUND

Neonatal lupus erythematosus is associated with the transplacental passage of maternal anti-Ro and anti-La antibodies, leading to complete atrioventricular block (CAVB). In some cases, CAVB is associated with EFE. Isolated EFE may be independently related to maternal anti-Ro and anti-La antibodies.

METHODS

We identified three cases (one fetus and two infants, all female) of isolated EFE in infants born to autoantibody-positive mothers in the absence of CAVB. Demographics, echocardiograms, and pathology were reviewed. Immunohistochemical analyses for immunoglobulin (Ig)G, IgM, IgA, T-cell, B-cell, and terminal deoxynucleoleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) (test for cell apoptosis) staining were performed on multiple sections of the heart in each case and compared with negative controls.

RESULTS

Two cases died and one received a cardiac transplant. All three cases had histologically confirmed EFE. All cases demonstrated significant diffuse IgG infiltration. To a lesser extent, myocardial tissue was also positive for IgM, CD43, and Granzyme B. None of the specimens were TUNEL positive.

CONCLUSIONS

These are the first reported cases of isolated EFE associated with maternal anti-Ro and anti-La antibodies in the absence of CAVB. The diffuse deposition of IgG and the presence of a T-cell infiltrate throughout the myocardium suggest that the transplacental passage of maternal autoantibodies induces an immune reaction within the myocardium, leading to isolated EFE. Autoantibody-mediated EFE may be an etiologic factor in cases of fetal and neonatal "idiopathic" dilated cardiomyopathy.

A serologic marker for fetal risk of congenital heart block

OBJECTIVE

To analyze the humoral immune response to Ro/SSA and La/SSB antigens in detail, in order to identify markers in mothers at high risk of having children with congenital heart block (CHB).

METHODS

Serum samples were obtained from 9 Ro/La-positive mothers who gave birth to affected children, from their 8 newborns with CHB, and from 26 Ro/La-positive mothers whose children were healthy. Antibodies against Ro 52-kd, Ro 60-kd, and La were analyzed by enzyme-linked immunosorbent assay and immunoblotting, using recombinant proteins and synthetic peptides.

RESULTS

IgG anti-Ro 52-kd antibodies were detected in all mothers who gave birth to children with CHB, as well as in their affected children, but were less frequent and at lower levels in control mothers. Fine mapping revealed a striking difference in which the response in mothers with affected children was dominated by antibodies to amino acids 200-239 of the Ro 52-kd protein (P = 0.0002), whereas the primary activity in control mothers was against amino acids 176-196 (P = 0.001). Furthermore, 8 of 9 mothers of children with CHB had antibody reactivity against amino acids 1-135 of the Ro 52-kd protein, containing 2 putative zinc fingers reconstituted under reducing conditions.

CONCLUSION

The results suggest that development of CHB is strongly dependent on a specific antibody profile to Ro 52-kd, which may be a useful tool to identify pregnant Ro/La-positive women at risk of delivering a baby with CHB. Close monitoring of mothers at high risk would enable early detection of a block that is still developing and allow early treatment to combat more serious complications.

Interaction between 52 kDa SSA/Ro and deubiquitinating enzyme UnpEL: a clue to function

The detection of isolated heart block in utero strongly predicts the presence of maternal autoantibodies reactive with 52 kDa SSA/Ro. The mechanisms that underlie this observation may be elucidated by defining the function of the target antigen. The initial approach was to identify proteins interactive with 52Ro using transcriptional activity in the yeast 2-hybrid system. A cDNA library was constructed using RNA isolated from human fetal hearts (12-23 weeks) and cloned into the HybriZAP vector encoding the activation domain of GAL4(AD) as target. Approximately 7 x 10(6) cDNAs were cotransformed with the bait into YRG-2. Plasmids from five interactive colonies were sequenced and three identified as the specific human deubiquitinating enzyme, UnpEL. UnpEL did not interact with bait plasmid encoding 52 beta, an alternative leucine zipper-minus form of 52 kDa SSA/Ro which is maximally expressed in fetal life. The mammalian 2-hybrid assay confirmed the interaction between full-length 52Ro and UnpEL. Further support for a biologic interaction was the marked redistribution in cellular localization of UnpEL following cotransfection of the two proteins into cultured human cardiocytes, human renal carcinoma cells (293 cells), and monkey kidney fibroblasts (COS-1). In conclusion, the interaction of full-length 52Ro and UnpEL implies that the former may also be involved in the ubiquitin pathway, an observation of particular interest since 52Ro contains a RING finger domain, a motif common to several recently reported proteins involved in modulating ubiquitination. The absence of an interaction with 52 beta raises the consideration that regulation of protein ubiquitination might differ in fetal life.

The health of mothers of children with cutaneous neonatal lupus erythematosus differs from that of mothers of children with congenital heart block

PURPOSE

Neonatal lupus erythematosus is caused by the transplacental passage of maternal autoantibodies. The aim of this study was to determine the risk of connective tissue disorders in mothers of children with cutaneous neonatal lupus erythematosus, as compared with the risk in mothers of children with congenital heart block, which is also often caused by maternal autoantibodies.

SUBJECTS AND METHODS

We prospectively studied all mothers of children with cutaneous neonatal lupus erythematosus during a 14-year period at the Hospital for Sick Children, Toronto, Ontario, Canada. We identified 28 mothers, of whom 24 were eligible for study. The health and antibody status of the mothers were determined at the birth of the child and at followup.

RESULTS

All mothers had anti-Ro antibodies at the time of birth. Initially 10 mothers were healthy and 14 mothers had either a defined (n = 9) or an undifferentiated (n = 5) autoimmune disorder. At a mean follow-up of 7 years, 13 (1 of whom had died) had a defined connective tissue disease, and 5 had an undifferentiated autoimmune disorder. Only 6 (25%) remained asymptomatic. By comparison, 36 (56%) of 64 mothers of children with congenital heart block were asymptomatic at follow-up (P <0.005).

CONCLUSIONS

The majority of mothers of children with cutaneous neonatal lupus erythematosus had a defined or undifferentiated autoimmune disorder at the time of the child's birth, and others developed these conditions during follow-up. The health of these mothers appears to differ from that of mothers of children with congenital heart block.

Neonatal Lupus Erythematosus

Neonatal lupus is categorized by typical clinical features and the presence of maternal auto-antibodies. Mothers are uncommonly affected with clinical disease. The major clinical manifestations in neonates are cardiac, dermatological and hepatic, with rare instances of haemolytic anaemia and thrombocytopenia. The major morbidity and mortality result from complete congenital heart block. Dermatological manifestations occur mainly over the face and present with plaques of erythema with central atrophy, a mid-facial erythema, atrophy around the eyes and a telangiectatic variety. The long term outcome is usually excellent.

Neonatal lupus erythematosus

This article discusses neonatal lupus erythematosus, which is a disease of the newborn defined by the presence of maternal autoantibodies and characteristic clinical features in the neonatal period. Although the autoantibodies often are not associated with clinical disease in the mother, neonatal lupus erythematosus is likely the result of fetal or neonatal tissue damage caused by maternally transmitted IgG autoantibodies.

Cardiac expression of 52beta, an alternative transcript of the congenital heart block-associated 52-kd SS-A/Ro autoantigen, is maximal during fetal development

OBJECTIVE

Congenital heart block (CHB), associated with antibodies to SS-A/Ro and SS-B/La, is most often detected between 18 and 24 weeks of gestation, yet the maternal heart is unaffected. We recently described an alternatively spliced 52-kd SS-A/Ro messenger RNA (mRNA) derived from the skipping of exon 4 which encodes a smaller protein, 52beta (MW 45 kd), recognized by CHB maternal antisera. This study was designed to identify whether cardiac expression of 52beta and full-length 52alpha relates to the development of CHB.

METHODS

Reverse transcriptase-polymerase chain reaction was performed using primers flanking exon 4 and mRNA from 22 human fetal hearts (age 11-25 weeks) and 3 adult hearts. The brain, kidney, liver, lung, and spleen were similarly evaluated in a 15-week, an 18-week, and a 24-week fetus.

RESULTS

Expression of 52beta was greatest and 52alpha lowest between 14 and 16 weeks of gestation. In fetal hearts ages 22-25 weeks and adult heart, the 52beta transcript was markedly diminished and 52alpha clearly dominated. The 52beta mRNA was observed in a 15-week brain, kidney, lung, and spleen; however, its expression relative to 52alpha was greatest in the heart.

CONCLUSION

Since expression of the alternative product 52beta is maximal at the time of cardiac ontogeny when maternal antibodies gain access to the fetal circulation, just prior to the clinical detection of bradyarrhythmia, a role for 52beta in the development of CHB is implicated. Although other fetal tissues express 52beta, there may be differences in accessibility of antigen or regenerative capacities.