RESUMO
To characterize antibody specificities associated with pre-eclampsia (PE), bacterial displayed peptide library screening and evolution was applied to identify peptide epitopes recognized by plasma antibodies present in women with PE near the time of delivery. Pre-eclamptic women exhibited elevated IgG1 titers towards a peptide epitope KRPSCIGCK within the Epstein-Barr virus nuclear antigen 1 (EBNA-1). EBNA-1 epitope antibodies cross-reacted with a similar epitope within the extracellular N-terminus of the human G protein-coupled receptor, GPR50, expressed in human placental tissue and immortalized placental trophoblast cells. We observed increased antibody binding activity to epitopes from EBNA-1 and GPR50 among women with PE (n=42) compared to healthy-outcome pregnancies (n=43) and nulligravid samples (n=21). The EBNA-1 peptide potently blocked binding of the PE-associated antibody to the GPR50 epitope (IC50=58-81pM). These results reveal the existence of molecular mimicry between EBNA-1 and placental GPR50, supporting a mechanism for IgG1 deposition in the pre-eclamptic placenta.
Assuntos
Anticorpos Antivirais/imunologia , Herpesvirus Humano 4/imunologia , Proteínas do Tecido Nervoso/imunologia , Placenta/imunologia , Pré-Eclâmpsia/imunologia , Receptores Acoplados a Proteínas G/imunologia , Adulto , Sequência de Aminoácidos , Anticorpos Antivirais/metabolismo , Reações Cruzadas/imunologia , Ensaio de Imunoadsorção Enzimática , Epitopos/imunologia , Epitopos/metabolismo , Antígenos Nucleares do Vírus Epstein-Barr/imunologia , Antígenos Nucleares do Vírus Epstein-Barr/metabolismo , Feminino , Células HEK293 , Herpesvirus Humano 4/metabolismo , Humanos , Imunoglobulina G/imunologia , Imunoglobulina G/metabolismo , Imuno-Histoquímica , Proteínas do Tecido Nervoso/metabolismo , Placenta/metabolismo , Pré-Eclâmpsia/metabolismo , Gravidez , Ligação Proteica/imunologia , Receptores Acoplados a Proteínas G/metabolismoRESUMO
The presence of maternal autoantibodies has been previously associated with preeclampsia, although the composition of the antibody repertoire in preeclampsia has not been well characterized. Given this, we applied a bacterial display peptide library to identify peptides that preferentially react with plasma antibodies from patients with preeclampsia (n=15) versus healthy-outcome pregnancies (n=18). Screening using fluorescence-activated cell sorting identified 38 peptides that preferentially bind to antibodies from individuals with preeclampsia. These preeclampsia-specific peptides possessed similar motifs of R(G)/S(G)/-WW(G)/S, RWW(G)/S, or WGWGXX(R)/K distinct from the angiotensin II type 1 receptor epitope AFHYESQ. Seven library-isolated peptides and a cell surface-displayed angiotensin II type 1 receptor epitope were used to construct a diagnostic algorithm with a training set of 18 new preeclamptic and 22 healthy-outcome samples from geographically distinct cohorts. Cross-validation within the training group resulted in averaged areas underneath a receiver operating characteristic curve of 0.78 and 0.72 with and without the known receptor epitope, respectively. In a small validation set (12 preeclamptic; 8 healthy), the algorithm consisting only of library-isolated peptides correctly classified 10 preeclamptic and 6 healthy samples using a predefined cutoff that achieved 61% sensitivity (95% confidence interval, 36%-83%) at 95% specificity (95% confidence interval, 77%-100%) in training set (n=40) cross-validation. Our results indicate that antibodies with specificities other than anti-angiotensin II type 1 receptor are prevalent in preeclampsia patients and may be useful as diagnostic biomarkers.