Transcriptional activity of human endogenous retroviruses is higher at birth in inversed correlation with gestational age.

Human endogenous retroviruses (HERVs) have been studied in relation to the onset and/or progression of several diseases. However, increasing evidence highlights that they also have important physiologic roles, for instance they are involved in preimplantation embryonic growth and in placentation. We assessed the transcriptional activity of HERVs in PBMCs of healthy newborns, infants and children to gather further information on their potential physiological roles. mRNA expression of HERV-H, K and W was evaluated in PBMCs of 63 preterm newborns, 47 term newborns, 38 infants (1-24 months of age), and 36 children (25-131 months of age) using a PCR real time Taqman amplification assay and normalization to glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The expression levels of HERV-H, K, and W were significantly higher at birth than in infancy and childhood. Furthermore, HERV activation was highest in preterm newborns and a significant inverse correlation was found between HERV transcripts and duration of pregnancy. The overexpression of HERVs at birth in inversed correlation with gestational age are further clues of their potential involvement in early life events.