Background:  Carbohydrate-binding agents represent innovative anti-HIV compounds selectively targeting the glycans of the HIV-1 envelope glycoprotein gp120 and preventing DC-SIGN-directed HIV capture by dendritic cells (DC) and transmission to CD4⁺ T lymphocytes. We wanted to investigate the ability of carbohydrate-binding agents to inhibit HIV-1 capture by human primary monocyte-derived macrophages (MDM) and to inhibit the subsequent virus transmission from HIV-1-captured MDM to CD4⁺ T lymphocytes.

Methods: HIV-1 capture was assessed by p24 antigen enzyme-linked immunosorbent assay (ELISA), in MDM infected by several HIV-1 strains and exposed to various doses of mannose-specific (plant lectins:  HHA, GNA, NPA, and CA; procaryotic cyanovirin-N [CV-N]), or GlcNAc-specific (plant lectin UDA) carbohydrate-binding agents. HIV-1 transmission between MDM infected with carbohydrate-binding agents-exposed HIV-1 and CD4⁺ T lymphocyte cell line (C8166) was analyzed by p24 antigen production and by syncytia formation. Virus production was analyzed in MDM at day 14 after carbohydrate-binding agents-exposed R5 HIV-1 infection. MDM were pre-incubated with different antibodies against macrophage mannose receptor (MMR), DC-SIGN, and CD4, or with mannan and than analyzed for both HIV-1 capture and virus transmission to C8166 cells by measuring p24 antigen. The experiments were carried out in triplicate and the results are presented as mean values with standard deviation.

Results:  We demonstrated that the carbohydrate-binding agents efficiently prevent R5 HIV-1 infection of MDM in the nanomolar range with a dose-dependent effect. The revealed values of EC₅₀ were 0.04, 0.038, 0.026, 0.01, 0.207, 0.0005, 3.8 µM, for HHA, GNA, NPA, CA, UDA, CV-N, PRM-A, respectively. The same order of magnitude was observed in C8166. Interestingly, both R5 and X4 HIV-1 strains were efficiently captured by MMR-expressing MDM. HIV-1 capture by MDM was dose-dependently inhibited by short pre-exposure of X4 HIV-1 to carbohydrate-binding agents, by MMR antibody (99% of capture inhibition ±SD 0.01, compared to control), and by the mannan (55% of capture inhibition ±SD 0.2, compared to control). Short pre-exposure of X4 HIV-1 to carbohydrate-binding agents also dose-dependently prevented virus transmission and subsequent syncytia formation in co-cultures of the carbohydrate-binding agent-exposed HIV-1-captured MDM and uninfected C8166.

Conclusions: The potential of carbohydrate-binding agents to impair MDM in their capacity to capture and to transmit HIV to CD4⁺ T lymphocytes might be an important property to be taken into consideration in the eventual choice to select microbicide candidate drugs for clinical investigation.