A transmissible human endogenous retrovirus.

The transmissibility of the human endogenous retrovirus HERV-H/RGH-2 was investigated by marker rescue: intraspecies transmission of HERV-H/RGH-2 retrovirus particles was attempted by cocultivation of virion-producing, long-term cell cultures spontaneously formed from peripheral blood mononuclear cells from several multiple sclerosis patient cultures with a retroviral vector construct-harboring cell line. Transmissibility was assessed by assays for productive infection (reverse transcriptase activity), and assays for rescue of the retroviral vector construct in indicator cells. Our studies show that the human endogenous retrovirus HERV-H/RGH-2 is transmissible, albeit at a very low level. The human endogenous retrovirus HERV-H/RGH-2 is associated with multiple sclerosis (MS). Previously, we demonstrated sequence variants of the human endogenous retrovirus HERV-H family in virion form, by applying RT-PCR to virion RNA from the supernatants of long-term MS cell cultures, and to the particulate fraction of a series of MS patient plasma samples.