Binding and transfer of human immunodeficiency virus by DC-SIGN⁺ cells in human rectal mucosa

The role of DC-SIGN on human rectal mucosal dendritic cells is unknown. Using highly purified human rectal mucosal DC-SIGN⁺ cells and an ultrasensitive real-time reverse transcription-PCR assay to quantify virus binding, we found that HULA-BR⁺/DC-SIGN⁺ cells can bind and transfer more virus than the HLA-DR⁺/DC-SIGN^- cells. Greater than 90% of the virus bound to total mucosal mononuclear cells (MMCs) was accounted for by the DC-SIGN⁺ cells, which comprise only 1 to 5% of total MMCs. Significantly, anti-DC-SIGN antibodies blocked 90% of the virus binding when more-physiologic amounts of virus inoculum were used. DC-SIGN expression in the rectal mucosa was significantly correlated with the interleukin-10 (IL-10)/ IL-12 ratio (r = 0.58, P < 0.002; n = 26) among human immunodeficiency virus (HIV)-positive patients. Ex vivo and in vitro data implicate the role of IL-10 in upregulating DC-SIGN expression and downregulating expression of the costimulatory molecules CD80/CD86. Dendritic cells derived from monocytes (MDDCs) in the presence of IL-10 render the MDDCs less responsive to maturation stimuli, such as lipopolysaccharide and tumor necrosis factor alpha, and migration to the CCR7 ligand macrophage inflammatory protein 3β. Thus, an increased IL-10 environment could render DC-SIGN ⁺ cells less iinmunosiimulatory and migratory, thereby dampening an effective immune response. DC-SIGN and the IL-10/IL-12 axis may play significant roles in the mucosal transmission and pathogenesis of HIV type 1.