In the most general terms, when the virus infects a new host cell, the SU protein on the surface of the virion engages with a receptor on the surface of the cell; this interaction then leads to large conformational changes in the Env complex; the end result of these changes is that TM catalyzes the fusion of the viral and cellular membranes, so that the contents of the virion are deposited in the cytoplasm of the new host cell, where they will initiate the next cycle of infection. This evidence concerns the gene ERVW-1 and infection.