Background: Topical microbicides are a viable alternative to reduce or prevent sexual transmission of HIV-1 which accounts for over 60% of transmission. We previously described elevated expression of IL-8 associated with HPV E7 mRNA expression in cervical biopsies from African women. The purpose of this study was to determine the role of IL-8 in transmission of HIV-1 across the cervix.

Methods: Ectocervical, endocervical, and transition zone biopsies were obtained from 10 benign hysterectomy specimens. These 4 mm punch biopsies were cultured in a transwell apparatus that maintained the polarity of normal tissue. Tissues were pre-treated (1 hr) with IL-8 (1 ng/mL) with and without serial dilutions of the IL-8 antagonist SB225002 (1 nM–100 nM). The tissues were then infected with 600 TCID₅₀ HIV-1_Bal (R5) or HIV-1_Lai (X4) and harvested after 24 hrs. Supernatants from the lower chamber of the transwell were added to cMAGI cells to quantify HIV-1 infectivity. Similar experiments were performed using cervical biopsies treated with purified HPV E7 protein. In these experiments, IL-8 mRNA was quantified in mRNA extracted from the tissue using real-time RTPCR.

Results: Addition of IL-8 to cervical explants cultures resulted in a 10- to 18-fold increase in susceptibility to HIV-1 infection compared to untreated controls (p = 0.001). Further, cervical organotypic cultures containing IL-8 exhibited increased susceptibility to X4-using HIV-1 relative to untreated controls consistent with a decreased CCR5:CXCR4 ratio in the explants. Competitive inhibition of the IL-8 receptor with SB225002 resulted in a 45%–70% decrease in cervical explant susceptibility to HIV-1 infection. IL-8 mRNA expression in cervical explant tissue increased 1.5- to 9-fold following the tissues with purified HPV E7 protein. Increased IL-8 expression was demonstrated by 2-color immunofluorescence predominantly in epithelial cells and macrophages.

Conclusions: The cytokine IL-8 is highly expressed in cervical tissue from African women. IL-8 expression correlates with the presence of HPV E7 protein, a viral oncoprotein expressed in dysplastic or cancerous cervical lesions. IL-8 increases susceptibility of cervical explant tissue to HIV-1 infection 10- to 18-fold while decreasing the CCR5:CXCR4 ratio and increasing infection with X4 isolates of HIV-1. The small molecule SB225002 decreases the effects of IL-8 on HIV-1 susceptibility and may have potential in reducing HIV-1 transmission.