THE EXPRESSION OF HUMAN ENDOGENOUS RETROVIRUS-3 IN FETAL CARDIAC TISSUE AND ANTIBODIES IN CONGENITAL HEART-BLOCK

Endogenous retrovirus-3 (ERV-3) is an endogenous retrovirus encoding a n open reading frame for an envelope protein expressed in placenta. In this study we also found high levels of expression in fetal heart, wi th peak expression occurring between 11 and 17 weeks of gestation. Ant ibodies to a peptide corresponding to a predicted epitope of ERV-3 wer e studied by ELISA in sera from 32 healthy women, 47 women during preg nancy. 19 post-partum, 34 with Sjogren's syndrome (SS), 28 with system ic lupus erythematosus (SLE) and 48 mothers of babies with congenital heart block (CHB). Elevated levels of antibodies to ERV-3 were found i n normal pregnancy and in patients with SS or SLE. Compared with norma l sera the highest levels occurred in mothers of CHB babies (P<0.001). Antibodies from sera from three CHB mothers bound to recombinant tran smembrane protein of ERV-3 on immunoblots, and to sections of fetal ca rdiac tissue and placenta. This study has shown evidence of autoimmuni zation to ERV-3 during pregnancy, with particularly high levels of ant ibodies in mothers of CHB babies. The expression of ERV-3 in fetal hea rt and the presence of antibodies in maternal sera suggest a possible role in the pathogenesis of CHB.