RESUMO
The mammalian genomic DNA is known to contain a variety o f endogenous proviruses but their expression is usually restricted to reproductive tissues such as the placenta and a variety of human tumour cells. More definitive characterization of retroviral gene products has been hampered by unavailability of specific biological reagents. In this study, polyclonal and a total of six monoclonal antibodies (mAbs) were raised against endogenous (intact) retroviral particles isolated from human placental villous tissue. These antibodies were characterized using immunohistochemical and biochemical methods. Five polyclonal antibodies and one mAb (RV1-17) showed strong specific immunohistochemical and immunogold staining with submembraneous structures within placental syncytiotropblast. The reactivity of these antibodies was consistent with the pattern of apical syncytiotrophoblastic budding of retroviral particles previously reported in ultrastructural analyses.