Envelope gene of the human endogenous retrovirus HERV-W encodes a functional retrovirus envelope

A member of the human endogenous retrovirus (HERV) family termed HERV-W enc odes a highly fusogenic membrane glycoprotein that appears to be expressed specifically in the placenta. It is unclear whether the glycoproteins of th e HERVs can serve as functional retrovirus envelope proteins to confer infe ctivity on retrovirus particles. We found that the HERV-W envelope glycopro tein can form pseudotypes with human immunodeficiency virus type 1 virions and confers tropism for CD4-negative cells. Thus, the HERV-W env gene repre sents the first HERV env gene demonstrated to encode the functional propert ies of a retrovirus envelope glycoprotein.