A linear trimannoside mimic inhibits DC-SIGN mediated HIV infection by polyvalent presentation

Background: Development of topical microbicides is a promising approach to prevent sexually transmitted HIV infection. DC-SIGN, expressed by dendritic cells at mucosal tissues, captures HIV by binding envelope glycoprotein gp120. Then DCs migrate to lymph nodes where mediate trans infection of CD4 T lymphocytes, promoting HIV dissemination. Therefore inhibition of HIV interaction with DCSIGN may represent a strategy to prevent early stages of HIV infection. The main DC-SIGN ligand on HIV gp120, is the high mannose glycan Man9. Structural analogues of high mannose terminal di or trisaccharides, able to compete with binding of DC-SIGN to HIV gp120, were synthesized. These compounds were prepared in multivalent systems to improve the affinity to DC-SIGN. Methods: Synthesized DC-SIGN inhibitors were tested in a trans infection in vitro assay. The B-THP1/ DC-SIGN cells (a B cell line transfected to express high DC-SIGN levels and supporting efficient DCSIGN-mediated HIV transmission) were pre-treated with different concentration of compounds, prior to exposure to HIV-1 R5 and X4 tropic strains, in the continued presence of compounds. Then BTHP1/DC-SIGN cells were co-coltured with CD4 T cells purified from healthy donors. After three days viral infection was evaluated by measuring p24 levels in co-culture supernatants. In a different protocol inhibitors were washed after pre-treatment, to evaluate duration of antiviral activity. Cytotoxicity of the compounds was evaluated by staining with 7AAD and cytofluorimetric analysis. Results: One of compounds tested, a tetravalent dendron containing four copies of a linear trimannoside mimic, was able to inhibit HIV trans infection of CD4 T lymphocytes at low micromolar range, with an IC50 of 5microM. At 100 microM the compound almost completely abrogated the transmission to CD4 T cells of HIV-1 laboratory strains or primary isolates, both R5 and X4 tropic. Notably the antiviral effect persisted up to 12 hours when the compound was removed after a 30 minutes pre-treatment. Moreover toxicity of the compound was neglectable at the highest concentration tested in infection assay. Conclusion: The tetravalent dendron presenting trimannoside mimic, in consequence of its anti-infective activity independent of viral tropism, absence of toxicity and long-lasting effect is potentially suitable for development as a vaginal microbicide.