Role of HLA in congenital heart block: susceptibility alleles in mothers

Transient Congenital Complete Heart Block: A Case Report

Congenital complete heart block is defined as a complete atrioventricular block occurring prenatally, at birth, or within the first month of life. Congenital complete heart block has a high mortality rate, and in infants with normal heart morphology, it is often associated with maternal connective tissue disease. In these latter cases, neonatal congenital complete heart block is usually irreversible. We present a rare case of a female neonate who had bradycardia noted at a gestational age of 37 weeks. Her mother had no autoimmune disease history. She had no structural heart disease, and the serology surveys for autoantibodies including SSA/Ro and SSB/La were all negative. Without intervention or medication, her congenital complete heart block completely recovered to a normal sinus rhythm within 5 days. The cause of the transient congenital complete heart block was unknown in this case.

Autoimmune congenital heart block: complex and unusual situations

Autoimmune congenital heart block (ACHB) is an immune-mediated cardiac disease included among the manifestations collectively referred to as neonatal lupus. The placental transference of maternal Ro/La autoantibodies may damage the conduction tissues during fetal development leading to blocking of signal conduction at the atrioventricular (AV) node in an otherwise structurally normal heart. Irreversible complete AV block is the main cardiac manifestation of ACHB, but some babies may develop endocardial fibroelastosis, valvular insufficiency, and/or frank cardiomyopathies with significantly reduced cardiac function requiring transplant. The severity of ACHB is illustrated by a global mortality rate of 20% and pacemaker rates of at least 64%, often within the first year of life. This review analyses the main complex and/or unusual clinical situations associated with ACHB, including unusual maternal immunological profiles, infrequent maternal autoimmune diseases, cardiac damage unrelated to AV block, fetal invasive management, late complications after birth, risk of congenital heart block (CHB) in ovodonation and in vitro fertilization techniques, the role of maternal features other than autoimmunity, the influence of the birth order or the risk of CHB in twins and triplets.

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.

Passively acquired anti-SSA/Ro antibodies are required for congenital heart block following ovodonation but maternal genes are not

Anti-SSA/Ro antibodies are necessary but not sufficient to provoke autoimmune-associated congenital heart block (CHB). Genetic factors are likely contributory. Accordingly, HLA-related candidates and single-nucleotide polymorphisms in the promoter region of tumor necrosis factor α and codon 10 in transforming growth factor β1 (TGFβ1) were evaluated in a unique family: the surrogate mother (anti-SSA/Ro positive), the biologic father, and the CHB-affected child (product of ovodonation). There was an HLA mismatch between the affected child and the surrogate mother. However, both the biologic and the surrogate mothers shared DQ2 and the profibrosing leucine polymorphism at codon 10 of TGFβ. In conclusion, we observed that CHB can develop in a genetically unrelated child exposed in utero to anti-SSA/Ro antibodies. Testing for anti-SSA/Ro antibodies might be considered in women undergoing artificial fertilization. It is possible that there is no direct association of maternal genes beyond a contributory role in generating the autoantibody.

Maternal MHC regulates generation of pathogenic antibodies and fetal MHC-encoded genes determine susceptibility in congenital heart block

Congenital heart block develops in fetuses of anti-Ro52 Ab-positive women. A recurrence rate of 20%, despite the persistence of maternal autoantibodies, indicates that there are additional, yet unidentified, factors critical for development of congenital heart block. In this study, we demonstrate that besides the maternal MHC controlling Ab specificity, fetal MHC-encoded genes influence fetal susceptibility to congenital heart block. Using MHC congenic rat strains, we show that heart block develops in rat pups of three strains carrying MHC haplotype RT1(av1) (DA, PVG.AV1, and LEW.AV1) after maternal Ro52 immunization, but not in LEW rats (RT1(l)). Different anti-Ro52 Ab fine specificities were generated in RT1(av1) versus RT1(l) animals. Maternal and fetal influence was determined in an F(2) cross between LEW.AV1 and LEW strains, which revealed higher susceptibility in RT1(l) than RT1(av1) pups once pathogenic Ro52 Abs were present. This was further confirmed in that RT1(l) pups more frequently developed heart block than RT1(av1) pups after passive transfer of RT1(av1) anti-Ro52 sera. Our findings show that generation of pathogenic Ro52 Abs is restricted by maternal MHC, whereas the fetal MHC locus regulates susceptibility and determines the fetal disease outcome in anti-Ro52-positive pregnancies.

Mechanisms of autoantibody production and the relationship between autoantibodies and the clinical manifestations in Sjögren's syndrome

The major target organs of Sjögren's syndrome (SS) are lacrimal glands and salivary glands where prominent lymphocytic infiltration occurs, which may induce varying levels of autoantibody production. Multiple factors, including environmental stress, viral infection, hormonal imbalance, and apoptosis, are thought to be involved in the pathogenesis of SS. Production of anti-SS-A/Ro and anti-SS-B/La antibodies is thought to be regulated by the presentation of autoantigens in context with an aberrant expression pattern of human leukocyte antigen (HLA) in situ. Molecular mimicry with some viral sequences is also hypothesized. The apoptosis-resistance phenotype of B cells in labial salivary glands (LSGs) of SS is important in autoantibody production. CD40/CD40L (CD40 ligand) and Bcl-2 family proteins, in tandem with B cell-activating factor (BAFF), are supposed to protect infiltrating lymphocytes from apoptosis. Anti-muscarinic3 receptor antibody plays an important role in cholinergic hyperresponsiveness in SS. Fragmentation of autoantigens such as SS-B/La or alfa-fodrin during the process of apoptosis causes the redistribution of these autoantigens, leading to the production of autoantibodies in SS. In this review, the role of autoantibodies found in SS, corresponding to clinical aspects of each antibody as well as the mechanisms of production, is discussed.

Genetic association of cutaneous neonatal lupus with HLA class II and tumor necrosis factor ?: Implications for pathogenesis

OBJECTIVE

Cutaneous neonatal lupus resembles subacute cutaneous lupus erythematosus (SCLE), and photosensitivity is a common symptom. Tumor necrosis factor alpha (TNFalpha) release by ultraviolet light-exposed keratinocytes may be exaggerated in SCLE patients who have the haplotype TNFalpha -308A;DRB1*03. Accordingly, this study was undertaken to seek genetic and histologic evidence for a role of TNFalpha in the pathogenesis of cutaneous neonatal lupus.

METHODS

DNA was isolated from 83 children (22 with rash, 35 with congenital heart block [CHB], 26 unaffected siblings) and 58 mothers from the Research Registry for Neonatal Lupus.

RESULTS

The -308A allele (associated with higher TNFalpha production), HLA-DRQB1*02, and HLA-DRB1*03 were each present in the majority of children with rash (64%, 68%, and 64%, respectively). The frequency of all 3 6p alleles occurring together in 1 individual was greater in children with rash than in children who had either CHB or no manifestation of neonatal lupus (59% versus 30%; P = 0.02). This association with neonatal lupus rash was equivalent to published findings in a cohort of patients with SCLE, but significantly greater than the association in patients with discoid lupus erythematosus. Prominent TNFalpha staining in the epidermis was observed in lesional skin from 3 children with rash, but not in skin from a healthy neonate.

CONCLUSION

Taken together, the finding of a genetic predisposition to generate increased levels of TNFalpha following tissue injury and the histologic demonstration of TNFalpha in the target organ support the notion that this inflammatory cytokine plays a role in the pathogenesis of cutaneous neonatal lupus. Furthermore, the results of these studies provide evidence of a biologic link between neonatal lupus and the rash of SCLE.

Update in Sjögren syndrome

Sjögren syndrome (SS), the second most common autoimmune rheumatic disease, refers to keratoconjunctivitis sicca and xerostomia resulting from immune lymphocytes that infiltrate the lacrimal and salivary glands. However, differential diagnosis remains confusing due to the high prevalence of vague symptoms of dryness, fatigue, and myalgias in the general population. The problems of diagnosis are further compounded by the finding of "positive" antinuclear antibodies in a high percent of the general population. Unless minor salivary gland biopsies are read by experienced observers, nonspecific changes of sialadenitis are frequently confused with the focal lymphocytic infiltrates that are characteristic of SS. The distinction between fibromyalgia patients with low titer antinuclear antibodies and primary SS remains difficult. Even in patients fulfilling strict criteria for SS, the genomic search for critical genes has proven difficult due to the multigenic pattern of inheritance and strong role of currently undefined environmental factors. No single environmental factor has been detected in the majority of SS patients. SS-like syndrome has been detected in certain patients with HTLV-1 and hepatitis C infection, providing clues to pathogenesis. Even in SS patients with marked sicca symptoms, minor salivary gland biopsy shows that almost 50% of glandular cells are still detected on biopsy. These results imply the importance of immune factors such as cytokines and autoantibodies in decreasing neuro-secretory circuits and induction of glandular dysfunction. Of potential importance, an antibody against muscarinic M3 receptor that can decrease secretory function when injected into rodents is frequently found in the sera of SS patients. Newly developed topical and oral therapies can ease the oral and ocular dryness. Orally administered agonists of the muscarinic M3 receptor (pilocarpine and cevimeline) have recently been approved by the US Food and Drug Administration to increase salivary secretion. Topical ocular use of low-dose corticosteroids or cyclosporin may decrease conjunctival surface inflammation. In a Phase II double-blind study, orally administered interferon alpha (150 U) led to improved saliva flow and symptoms. In pregnant patients with evidence of fetal distress, oral dexamethasone is preferred because this agent crosses the placenta effectively. In animal models, antagonists of tumor necrosis factor and inhibitors of de novo pyrimidine synthesis appear promising.

Neonatal lupus erythematosus: analysis of HLA class I genes in Japanese child/mother pairs

Neonatal lupus erythematosus (NLE), characterized by two major symptoms of congenital heart block (CHB) and transient cutaneous lesions, is an antibody mediated disorder due to placentally transmitted maternal autoantibodies to Ro/SSA and/or La/SSB. We genotyped 14 mothers, 9 children with CHB, 8 with cutaneous NLE only and 5 asymptomatic siblings at HLA class I loci, by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) combined with sequence-specific amplification. Mothers of children with NLE exhibited a very high polymorphism of HLA class I genes. Significant increases of HLA-B*1501 (B62) and Cw*0303 (Cw9) with absence of HLA-A1/B8 haplotype in Japanese mothers differed from the serologically defined HLA class I profiles among NLE mothers in white and North American black populations. Child/mother heterozygous HLA-A/B/C haplotype identity, which extended to HLA-class II DR/DQ loci, was observed in only one of 9 cases with CHB. No association was found between HLA class I alleles of children and the symptoms of NLE. These findings provide for the opportunity to investigate the primary genetic associations with NLE/CHB in different ethnic groups.

Role of HLA in congenital heart block: susceptibility alleles in children

Congenital heart block (CHB) is a syndrome of uncertain pathogenesis leading to cardiac conduction disturbances in the foetus and newborns. It has been proposed that maternal antibodies transmit immunological injury in the developing foetal heart, thus causing irreversible damage of the atrioventricular node, leading to third-degree atrioventricular block. However, some genetic or environmental factors may also be involved. We have searched for genetic markers that play a role in immune response and that would be pathognomonic for the disease, either in mothers by regulating their immune response or in children by affecting antigen presentation and target for the maternal immune response. We have compared HLA class I and II alleles of the children with their mother and with healthy individuals and searched for HLA markers that would be emphasized in children. We have shown that particular DQ alleles in the child predispose to CHB, perhaps serving as antigen-presenting molecules on site. In addition, the HLA-Cw3 allele is involved, although its function remains to be clarified. In our results, children with CHB were often identical to their mothers in alleles of DRB, DQA and DQB loci, thus affecting foetomaternal recognition and suggesting that cell-mediated mechanisms could be involved in the pathogenesis.