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Abstract Background Plant lectins such as Galanthus nivalis agglutinin (GNA) and Hippeastrum hybrid agglutinin (HHA) are natural proteins able to link mannose residues, and therefore inhibit HIV-target cell interactions. Plant lectins are candidate for microbicide development. Objective To evaluate the activity against HIV of the mannose-specific plant lectins HHA and GNA at the cellular membrane level of epithelial cells and monocyte-derived dendritic cells (MDDC), two potential target cells of HIV at the genital mucosal level. Methods The inhibitory effects of HHA and GNA were evaluated on HIV adsorption to genital epithelial HEC-1A cell line, on HIV transcytosis throughout a monolayer of polarized epithelial HEC-1A cells, on HIV adsorption to MDDC and on transfer of HIV from MDDC to autologous T lymphocytes. Results HHA faintly inhibited attachment to HEC-1A cells of the R5-tropic HIV-1Ba-L strain, in a dose-dependent manner, whereas GNA moderately inhibited HIV adsorption in the same context, but only at high drug doses. Only HHA, but not GNA, inhibited HIV-1JR-CSF transcytosis in a dose-dependent manner. By confocal microscopy, HHA, but not GNA, was adsorbed at the epithelial cell surface, suggesting that HHA interacts specifically with receptors mediating HIV-1 transcytosis. Both plant lectins partially inhibited HIV attachment to MDDC. HHA inhibited more efficiently the transfer of HIV from MDDC to T cell, than GNA. Both HHA and GNA lacked toxicity below 200 μg/ml irrespective the cellular system used and do not disturb the monolayer integrity of epithelial cells. Conclusion These observations demonstrate higher inhibitory activities of the lectin plant HHA by comparison to GNA, on HIV adsorption to HEC-1A cell line, HIV transcytosis through HEC-1A cell line monolayer, HIV adsorption to MDDC and HIV transfer from MDDC to T cells, highlighting the potential interest of HHA as effective microbicide against HIV.

CD21, the C3d/CD23/Epstein–Barr virus (EBV), receptor is expressed at low density on cells of the T lineage. Immature thymocytes express CD21 with high density. In the present study, we have analyzed the expression of CD21 during intrathymic maturation of T cells. An intense staining for CD21 was observed at the double-negative stage and at the stage of early acquisition of CD4. CD21 expression was decreased at the double-positive and single-positive stages, to then reach levels similar to those of peripheral blood T cells. Staining of thymus sections showed a bright fluorescent signal on thymocytes entering the thymus in the cortical region. Taking advantage of the immature phenotype of cells expressing high amounts of CD21 (CD21++), we depleted thymocyte suspensions in CD3+ and CD8+ cells to study the properties of CD21 on this cell subset. Triggering of CD21 with its ligands iC3b, CD23 and anti-CD21 mAb did not alter the proliferative response of thymocytes to IL-7, and did not induce the differentiation of early cells into CD4+CD8+ thymocytes. Immunoprecipitation did not reveal any molecule associated with CD21 that could play a signaling role in thymocytes. Finally, EBV induced a down-regulation of CD21 and an up-regulation of CD1 in CD21++ thymocytes. Taken together, our observations demonstrate a regulated expression of CD21 on human thymocytes and suggest that the CD21++ subset may be a target for EBV. We further suggest that CD21 on early thymocytes acts as a ligand for CD23-expressing cells in the thymus. [ABSTRACT FROM PUBLISHER]