FIG. 4.

SEVI and semen enhance virus entry by the XMRV envelope protein. (A) Enhancement of the specific entry of an XMRV env-pseudotyped lentivirus (XMRVenv/SHIV) into HEK-293T cells by SEVI. (B) Infectivities of undiluted or serial fivefold dilutions of XMRVenv/SHIV determined with and without addition of SEVI (10 μg/ml). (C) Enhancement of XMRVenv/SHIV infectivity by semen. Virus supernatants (as indicated) were preincubated with the indicated percentage of semen for 15 min and further diluted 1:15 prior to infecting cells. Data are average values ± standard deviations obtained from triplicate experiments at 2 days postinfection.