Sperm can act as vectors for HIV-1 transmission into vaginal and cervical epithelial cells

Sperm are the major cells in semen. Human sperm possess a number of HIV-1 gp120 binding ligands including sulfogalactosylglycerolipid (SGG). However, the mechanisms of how sperm capture HIV-1 onto their surface are unclear. Furthermore, the ability of sperm to deliver HIV-1 to vaginal/cervical epithelial cells lining the lower female reproductive tract, as a first step in HIV-1 transmission, needs to be determined.

Sperm from healthy donors were incubated with dual-tropic HIV-1_CS204 (clinical isolate), and virus capture was determined by p24 antigen ELISA. The involvement of SGG in HIV-1 capture was assessed by determining K_d values of HIV-1 gp120-SGG binding as well as computational docking of SGG to the gp120 V3 loop. The ability of sperm-associated HIV-1 to infect peripheral blood mononuclear cells (PBMCs) and TZM-bl indicator cells was determined. Lastly, infection of vaginal (Vk2/E6E7), ectocervical (Ect1/E6E7), and endocervical (End1/E6E7) epithelial cells mediated by HIV-1-associated sperm was evaluated.

Sperm were able to capture HIV-1 in a dose-dependent manner, and the capture reached a maximum within 5 minutes. Captured HIV-1, however, could be removed from sperm by Percoll-gradient centrifugation. Affinity of gp120 for SGG was substantial, implicating sperm SGG in HIV-1 capture. Sperm-associated HIV-1 could productively infect PBMCs and TZM-bl cells, and was capable of being transmitted into vaginal/cervical epithelial cells.

Sperm are able to capture HIV-1, which remains infectious and is able to be transmitted into vaginal/cervical epithelial cells, a result indicating the importance of sperm in HIV transmission.