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

A review of neonatal lupus syndrome

This review article discusses neonatal lupus syndrome (NLS), an immune-mediated disease caused by maternal antibodies. Maternal antibodies in the fetal circulation are mostly but not always protective. NLS is a disease caused by pathogenic maternal autoantibodies in the fetal circulation. The passive immunization of the fetus by NLS-causing maternal antibodies may occur in the absence of a previously known maternal systemic autoimmune rheumatic disease (SARD). Screening for NLS-related antibodies in patients with related SARD or those in whom there is a risk of NLS including first-degree relatives should occur before pregnancy. This screening is best performed as part of a collaborative relationship between obstetrics and rheumatology. Pregnancy preparations in those with SARD include transitioning to pregnancy-safe medications. The symptoms of NLS range from minor skin rashes to fetal demise from heart block. Fetal screening allows for maternal therapeutic interventions that may be beneficial, as well as the use of fetal pacemakers in the more severe cases that include cardiac NLS.

Olfatory HLA-associated mechanism of formation of married couples in the development of congenital heart diseases in children

Taking into account the significance of the HLA complex in the inflammatory and immune responses, we can assume that the potential for limiting or developing pathology in the next generation will be determined at the stage of selection of certain alleles in the spousal genotype.The aim. To study the role of HLA assortativity in couples with healthy children and couples with children with congenital heart diseases (CHD) through the prism of immunogenetic mechanisms of mutual olfactory choice.Materials and methods. We studied the distribution of HLA-DRB1 alleles in married couples with healthy children and with children having CHD. To identify the associations of HLA-DRB1 alleles with odor preferences, we also studied the group included young males and females. HLA-DRB1 gene typing was carried out in all participants.Results. The combination of HLA-DRB1 alleles in couples with healthy children was similar to the combination of these alleles in the mutual olfactory sympathy between unfamiliar young males and females. Allele combinations in the spouses from the experimental group differ from the group of random selection. The frequency of matches for HLA-DRB1 alleles in married couples with children having CHD without was significantly higher than in the control group.Conclusion. The first stage of selection, associated with olfactory selection, is aimed to the whole population, and it is significantly manifested in the control group (married couples with healthy children). At the same time, in the experimental group (couples with children having CHD), some deviations from the main selection were discovered. Generally, specific HLA-DRB1 allele combinations obtained on the basis of olfactory assessments, indicate the involvement of HLA molecules in pheromone reception.

Auxilin is a novel susceptibility gene for congenital heart block which directly impacts fetal heart function

OBJECTIVE

Neonatal lupus erythematosus (NLE) may develop after transplacental transfer of maternal autoantibodies with cardiac manifestations (congenital heart block, CHB) including atrioventricular block, atrial and ventricular arrhythmias, and cardiomyopathies. The association with anti-Ro/SSA antibodies is well established, but a recurrence rate of only 12%-16% despite persisting maternal autoantibodies suggests that additional factors are required for CHB development. Here, we identify fetal genetic variants conferring risk of CHB and elucidate their effects on cardiac function.

METHODS

A genome-wide association study was performed in families with at least one case of CHB. Gene expression was analysed by microarrays, RNA sequencing and PCR and protein expression by western blot, immunohistochemistry, immunofluorescence and flow cytometry. Calcium regulation and connectivity were analysed in primary cardiomyocytes and cells induced from pleuripotent stem cells. Fetal heart performance was analysed by Doppler/echocardiography.

RESULTS

We identified DNAJC6 as a novel fetal susceptibility gene, with decreased cardiac expression of DNAJC6 associated with the disease risk genotype. We further demonstrate that fetal cardiomyocytes deficient in auxilin, the protein encoded by DNAJC6, have abnormal connectivity and Ca2+ homoeostasis in culture, as well as decreased cell surface expression of the Cav1.3 calcium channel. Doppler echocardiography of auxilin-deficient fetal mice revealed cardiac NLE abnormalities in utero, including abnormal heart rhythm with atrial and ventricular ectopias, as well as a prolonged atrioventricular time intervals.

CONCLUSIONS

Our study identifies auxilin as the first genetic susceptibility factor in NLE modulating cardiac function, opening new avenues for the development of screening and therapeutic strategies in CHB.

An Overview of Neonatal Lupus with Anti-Ro Characteristics

Neonatal lupus erythematosus (NLE) is a syndrome of clinical symptoms observed in neonates born to mothers with antibodies to soluble antigens of the cell nucleus. The main factors contributing to the pathogenesis of this disease are anti-Sjögren Syndrome A (anti-SS-A) antibodies, known as anti-Ro, and anti-Sjögren Syndrome B (anti-SS-B) antibodies, known as anti-La. Recent publications have also shown the significant role of anti-ribonucleoprotein antibodies (anti-RNP). Seropositive mothers may have a diagnosed rheumatic disease or they can be asymptomatic without diagnosis at the time of childbirth. These antibodies, after crossing the placenta, may trigger a cascade of inflammatory reactions. The symptoms of NLE can be divided into reversible symptoms, which concern skin, hematological, and hepatological changes, but 2% of children develop irreversible symptoms, which include disturbances of the cardiac stimulatory and conduction system. Preconceptive care and pharmacological prophylaxis of NLE in the case of mothers from the risk group are important, as well as the monitoring of the clinical condition of the mother and fetus throughout pregnancy and the neonatal period. The aim of this manuscript is to summarize the previous literature and current state of knowledge about neonatal lupus and to discuss the role of anti-Ro in the inflammatory process.

Ethnicity and Neonatal Lupus Erythematosus Manifestations Risk in a Large Multiethnic Cohort

OBJECTIVE

To evaluate the association between ethnicity and neonatal lupus erythematosus (NLE), as well as specific NLE manifestations in a large multiethnic population.

METHODS

We conducted a cohort study of the children (≤ 1 yr of age) seen in the NLE clinic at The Hospital for Sick Children (SickKids), between January 2011 and April 2019. The cohort was divided into European, non-European, and mixed European-non-European groups according to parent-reported child's ethnicity (Canada Census categories). Outcomes were NLE and specific NLE manifestations (cardiac, cutaneous, cytopenias, transaminitis, and macrocephaly). The frequency of NLE and specific manifestations were compared between ethnic groups (Fisher exact test). We tested the association between ethnicity and (1) NLE risk, and (2) specific NLE manifestations with logistic regression models, including covariates for child's sex, maternal rheumatic disease status during pregnancy, and maternal use of antimalarials during pregnancy (multiple comparisons threshold P < 0.008).

RESULTS

We included 324 children born to 270 anti-Ro antibody-positive mothers. Median age at first visit was 1.8 (IQR 1.4-2.3) months, and median follow-up time was 12 (IQR 2-24) months. The majority was non-European (48%), with 34% European, and 18% mixed European-non-European. There was no significant association between non-European ethnicity (OR 1.18, 95% CI 0.71-1.94, P = 0.51), mixed European-non-European ethnicity (OR 1.13, 95% CI 0.59-2.16, P = 0.70), and NLE risk compared with European ethnicity. We also did not find an association between ethnicity and specific NLE manifestations in univariate or multivariable-adjusted models.

CONCLUSION

In a large multiethnic cohort, there was no association between a child's ethnicity and NLE risk or specific NLE manifestations.

Interferons and innate immune activation in autoimmune congenital heart block

Autoimmune congenital heart block (CHB) may develop in foetuses of women carrying anti-Ro/SSA and La/SSB autoantibodies and is characterized by disruption of signal conduction at the atrioventricular (AV) node, resulting in partial or complete AV block. If not fatal in utero, complete CHB typically requires lifelong cardiac pacing. No treatment has so far been unequivocally demonstrated to prevent or treat autoimmune CHB, and the relatively low incidence (1%-5%) and recurrence (12%-16%) rates of second/third-degree AV block add to the complexity of managing pregnancies in women with anti-Ro/La antibodies. Altogether, a better understanding of events leading to development of autoimmune CHB is needed to improve surveillance and treatment strategies. In the past decade, studies have started to look beyond the role of maternal autoantibodies in disease pathogenesis to assess other contributing factors such as foetal genetics and, more recently, immune responses in foetuses and neonates of anti-Ro/La antibody-positive women. In this review, we provide an update on the epidemiology, clinical presentation and current treatment approaches of autoimmune CHB, summarize the previously proposed pathogenic mechanisms implicating maternal autoantibodies, and discuss the recent findings of type I interferon (IFN) and innate immune activation in foetuses with autoimmune CHB and in neonates of anti-Ro/La antibody-positive mothers, and how these may contribute to autoimmune CHB pathogenesis.

Natural killer cells and type II interferon in Ro/SSA and La/SSB autoantibody-exposed newborns at risk of congenital heart block

OBJECTIVE

Congenital heart block (CHB) with immune cell infiltration develops in the fetus after exposure to maternal Ro/La autoantibodies. CHB-related serology has been extensively studied, but reports on immune-cell profiles of anti-Ro/La-exposed neonates are lacking. In the current study, we characterised circulating immune-cell populations in anti-Ro/La+mothers and newborns, and explored potential downstream effects of skewed neonatal cell populations.

METHODS

In total, blood from mothers (n=43) and neonates (n=66) was sampled at birth from anti-Ro/La+ (n=36) and control (n=30) pregnancies with or without rheumatic disease and CHB. Flow cytometry, microarrays and ELISA were used for characterising cells and plasma.

RESULTS

Similar to non-pregnant systemic lupus erythematosus and Sjögren-patients, anti-Ro/La+mothers had altered B-cell subset frequencies, relative T-cell lymphopenia and lower natural killer (NK)-cell frequencies. Surprisingly, their anti-Ro/La exposed neonates presented higher frequencies of CD56^dimCD16^hi NK cells (p<0.01), but no other cell frequency differences compared with controls. Type I and II interferon (IFN) gene-signatures were revealed in neonates of anti-Ro/La+ pregnancy, and exposure of fetal cardiomyocytes to type I IFN induced upregulation of several NK-cell chemoattractants and activating ligands. Intracellular flow cytometry revealed IFNγ production by NK cells, CD8⁺ and CD4⁺ T cells in anti-Ro/La exposed neonates. IFNγ was also detectable in their plasma.

CONCLUSION

Our study demonstrates an increased frequency of NK cells in anti-Ro/La exposed neonates, footprints of type I and II IFN and an upregulation of ligands activating NK cells in fetal cardiac cells after type I IFN exposure. These novel observations demonstrate innate immune activation in neonates of anti-Ro/La+pregnancy, which could contribute to the risk of CHB.

Comorbidity and long-term outcome in patients with congenital heart block and their siblings exposed to Ro/SSA autoantibodies in utero

Objective

Congenital heart block (CHB) may develop in fetuses of Ro/SSA autoantibody-positive women. Given the rarity of CHB, information on comorbidity and complications later in life is difficult to systematically collect for large groups of patients. We therefore used nation-wide healthcare registers to investigate comorbidity and outcomes in patients with CHB and their siblings.

Methods

Data from patients with CHB (n= 119) and their siblings (n= 128), all born to anti-Ro/SSA-positive mothers, and from matched healthy controls (n= 1,190) and their siblings (n= 1,071), were retrieved from the Swedish National Patient Register. Analyses were performed by Cox proportional hazard modelling.

Results

Individuals with CHB had a significantly increased risk of cardiovascular comorbidity, with cardiomyopathy and/or heart failure observed in 20 (16.8%) patients versus 3 (0.3%) controls, yielding a HR of 70.0 (95% CI 20.8 to 235.4), and with a HR for cerebral infarction of 39.9 (95% CI 4.5 to 357.3). Patients with CHB also had a higher risk of infections. Pacemaker treatment was associated with a decreased risk of cerebral infarction but increased risks of cardiomyopathy/heart failure and infection. The risk of systemic connective tissue disorder was also increased in patients with CHB (HR 11.8, 95% CI 4.0 to 11.8), and both patients with CHB and their siblings had an increased risk to develop any of 15 common autoimmune conditions (HR 5.7, 95% CI 2.83 to 11.69 and 3.6, 95% CI 1.7 to 8.0, respectively).

Conclusions

The data indicate an increased risk of several cardiovascular, infectious and autoimmune diseases in patients with CHB, with the latter risk shared by their siblings.

Autoimmune-associated Congenital Heart Block: A New Insight in Fetal Life

OBJECTIVE

Congenital heart block (CHB) is a rare but life-threatening disorder. More than half of CHB cases are associated with maternal autoimmune, which are termed as autoimmune-associated CHB. This review summarized the recent research findings in understanding autoimmune-associated CHB, discussed the current diagnostic approaches and management strategies, and summarized the problems and future directions for this disorder.

DATA SOURCES

We retrieved the articles published in English from the PubMed database up to January 2017, using the keywords including "Autoimmune-associated", "Autoimmune-mediated", and "Congenital heart block".

STUDY SELECTION

Articles about autoimmune-associated CHB were obtained and reviewed.

RESULTS

Observational studies consistently reported that transplacental maternal antibodies might recognize fetal or neonatal antigens in various tissues and result in immunological damages, but the molecular mechanisms underlying CHB pathogenesis still need illuminated. Multiple factors were involved in the process of atrioventricular block development and progression. While several susceptibility genes had been successfully defined, how these genes and their protein interact and impact each other remains to be explored. With currently available diagnostic tools, fetal ultrasound cardiography, and fetal magnetocardiography, most of CHB could be successfully diagnosed and comprehensively evaluated prenatally. The efficacy of current approaches for preventing the progression and recurrence of CHB and other autoimmune-mediated damages was still controversial.

CONCLUSIONS

This review highlighted the relationships between autoimmune injuries and CHB and strengthened the importance of perinatal management and therapy for autoimmune-associated CHB.

Association of Natural Killer Cell Ligand Polymorphism HLA-C Asn80Lys With the Development of Anti-SSA/Ro-Associated Congenital Heart Block

OBJECTIVE

Fetal exposure to maternal anti-SSA/Ro antibodies is necessary but not sufficient for the development of autoimmune congenital heart block (CHB), suggesting that other factors, such as fetal genetic predisposition, are important. Given the previously described association between major histocompatibility complex alleles and CHB risk, we undertook the present study to test the hypothesis that a variant form of HLA-C Asn80Lys, which binds with high affinity to an inhibitory killer cell immunoglobulin-like receptor (KIR) and thus renders natural killer (NK) cells incapable of restricting inflammation, contributes to the development of CHB.

METHODS

Members of 192 pedigrees in the US and Europe (194 cases of CHB, 91 unaffected siblings, 152 fathers, 167 mothers) and 1,073 out-of-study controls were genotyped on the Immunochip single-nucleotide polymorphism microarray. Imputation was used to identify associations at HLA-C Asn80Lys (Asn, C1; Lys, C2) and KIR. Tests for association were performed using logistic regression. McNemar's test and the pedigree disequilibrium test (PDT) were used for matched analyses between affected and unaffected children.

RESULTS

Compared with out-of-study controls of the same sex, the C2 allele was less frequent in the mothers (odds ratio [OR] 0.63, P = 0.0014) and more frequent in the fathers (OR 1.40, P = 0.0123), yielding a significant sex-by-C2 interaction (P = 0.0002). The C2 allele was more frequent in affected siblings than in unaffected siblings (OR 3.67, P = 0.0025), which was consistent with the PDT results (P = 0.016); these results were observed in both sexes and across the US and European cohorts. There was no difference in the frequency of the inhibitory KIR genotype (KIR AA) between affected and unaffected children (P = 0.55).

CONCLUSION

These data establish C2 as a novel genetic risk factor associated with CHB. This observation supports a model in which fetuses with C2 ligand expression and maternal anti-SSA/Ro positivity may have impaired NK cell surveillance, resulting in unchecked cardiac inflammation and scarring.

Environmental and lifestyle factors influencing risk of congenital heart block during pregnancy in anti-Ro/SSA-positive women

OBJECTIVES

Congenital heart block (CHB) occurs in 1%-2% of anti-Ro/SSA antibody-positive pregnancies. A population-based recurrence rate of 12% indicates that factors other than maternal autoantibodies influence CHB development. Here we report the first investigation to identify environmental and lifestyle factors influencing the risk of CHB.

METHODS

A questionnaire focused on environmental and lifestyle factors was distributed to anti-Ro/SSA antibody-positive women who had given birth to at least one child with CHB, and additional data were retrieved from national health registers. Statistical analysis was performed comparing pregnancies resulting in a child with CHB (n=81) and pregnancies resulting in unaffected siblings (n=108).

RESULTS

Analysis of maternal body mass index and weight gain during pregnancy as well as medication intake and sun exposure did not reveal significant differences between CHB-affected and non-CHB pregnancies. By contrast, we found that reports of infections and stressful events were significantly more frequent in CHB-affected pregnancies than in non-CHB affected pregnancies (OR 17.9, 95% CI 4.1 to 162.8, p<0.001 and OR 5.5, 95% CI 1.1 to 55.1, p<0.05, respectively). Notably, outdoor activity a few hours per day emerged as a protective factor (OR 0.52, 95% CI 0.27 to 0.99, p<0.05). The previously reported factor seasonal timing of pregnancy was confirmed (OR 2.2, 95% CI 1.1 to 4.2, p<0.05), and multivariate analysis revealed that this association was partly explained by infection and outdoor activity.

CONCLUSIONS

In this retrospective study, infections, stressful events and time spent with outdoor activities emerged as potential environmental and lifestyle factors influencing the risk of CHB, warranting confirmation in prospective studies.

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.