EVALUATION OF ANTI-INFECTIVE ACTIVITY OF GLYCOMIMETIC DC-SIGN LIGANDS

Background. HIV remains one of the leading causes of mortality and morbidity worldwide. As the vast majority of HIV infections occurs via unprotected sexual intercourses, the development of topical microbicides is a new and promising approach to prevent HIV sexual transmission. DC-SIGN, a C-type Lectin Receptor (CLR), participates in the initial stages of sexually transmitted HIV infection by recognizing highly mannosylated structures displayed in multiple copies on HIV gp120. Dendritic cells located in genital mucosae internalize HIV through DC-SIGN and transmit the virus in trans to CD4 T lymphocytes, promoting virus dissemination. Furthermore, binding of HIV to DC-SIGN activates signaling pathways that induce immunosuppression and promote HIV replication and transmission. Thus, inhibition of HIV interaction with DC-SIGN represents a potential therapeutic approach to prevent HIV infection at the mucosal level. Aim of this study was to evaluate the efficacy in inhibiting HIV infection and the potential toxicity of a multimeric glycomimetic DC-SIGN ligand (dendron 12). Methods. In the initial phase of this study, the ability of dendron 12 to block laboratory and primary HIV-1 strains transmission to CD4 T cells was assessed using a trans infection assay in vitro. Owing the results obtained, the efficacy of dendron 12 in inhibiting HIV-1 infection of mucosal tissue taken from human uterine cervix was evaluated. Cervical explants were treated with the dendron 12 and then exposed to different HIV-1 strains in a non polarized manner, mimicking a condition of compromised epithelial integrity. Infection was determined by measuring p24 HIV-1 core protein concentration in supernatants of cell and explant cultures. β chemokines production following stimulation of monocyte-derived DCs was also analyzed. The selectivity of dendron 12 towards DC-SIGN and Langerin, another CLR that recognize high mannosylated structures, was evaluated by Surface Plasmon Resonance (SPR) studies. Toxicity of the compound was evaluated in both cellular and tissue models. Results. Dendron 12 prevented trans infection of CD4 T lymphocytes and infection of human cervical tissue by multiple clades of R5 and X4 tropic HIV-1 strains, even in presence of elevated viral loads. The compound displayed a prolonged activity and absence of toxicity at the highest concentration tested in infection assays. Treatment with dendron 12 did not interfere with the activity of Langerin that, in contrast to DC-SIGN, prevents HIV transmission promoting the degradation of the virus. Moreover dendron 12 significantly elicited the production of the β chemokines MIP-1α, MIP-1β and RANTES. The dendron 12 was found to be soluble in physiological media and stable at both neutral and acid pH. Conclusion. Dendron 12 inhibits HIV-1 infection by competition with binding of HIV to DC-SIGN and stimulation of β chemokines production. Furthermore dendron 12 is highly soluble in physiological media, stable at acidic vaginal pH, no toxic and endowed with a long-lasting effect. Thus, dendron 12 represents a promising lead compound for the development of anti-HIV topical microbicides.