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Background:  Following heterosexual intercourse, the Langerhans’ cells (LC) of vaginal mucosa are involved in the transmission of HIV from the sperm to the lymph nodes. CCL20 is a chemokine that is secreted by epithelial cells after stimulation with proinflammatory cytokines; it has been shown to specifically attract LCs. In the present work, we analyzed the cytokine composition of seminal plasmas from HIV- and HIV+ patients and their effect on the attraction of LCs through the production of CCL20 by human vaginal epithelial cells.

Methods:  A total of 65 seminal plasmas (32 from HIV⁺ and 33 from HIV^- men) were tested for the presence of IL1b, TNFa, TGFb, IFNg, IL6, and IL8 by using ELISA. CCL20 production was quantified by ELISA on the supernatants of a vaginal epithelial cell line (SiHa) incubated for 18 h with these seminal plasmas. Incubation with IL1b served as a positive control. The capacity of migration of CCR6⁺ immature dendritic cells (iDC) under the influence of SiHa supernatants was assayed by using Biocoat invasion chambers (BD).

Results:  Among all the cytokines tested in seminal plasma, only IL1b concentrations were significantly different between samples from HIV⁺ (69.64±117 pg/mL) and HIV^- (7.97±12.73 pg/mL) subjects (p = 0.006 by t test). All the 65 seminal plasma specimens were able to stimulate the secretion of CCL20 by SiHa cells by at least 5 fold as compared to untreated cells, and the CCL20-positive supernatants were able to attract iDCs, contrary to untreated SiHa cell supernatant or medium alone. No correlation was observed between the amount of secreted CCL20 and the concentration of seminal IL1b. In addition, the amount of CCL20 secreted by SiHa cells was not influenced by the pre-incubation of IL1b-positive specimens with an anti-IL1b neutralizing antibody.

Conclusions:  These data demonstrate that seminal plasma participates to the process of HIV transmission by attracting LCs via the stimulation of CCL20 secretion by epithelial cells. Moreover, they suggest that seminal factors other than IL1b and also present in the sperm of HIV- subjects are involved in this stimulation and could facilitate the transfer of HIV from HIV⁺ semen to vaginal target cells.

Keywords: Heterosexual transmission; Seminal plasma; CCL20