Association of Human Mannose Receptor in Sexual Transmission of Human Immunodeficiency Virus in Serodiscordant Couples

HIV binds specifically to the human mannose receptor (hMR) on vaginal epithelial cells that are devoid of a conventional CD4 receptor. HIV binding to hMR on vaginal epithelial cells induces the production of matrix metalloproteinase 9 (MMP9) leading to degradation of the extracellular matrix, which may increase the risk of HIV entry into vaginal epithelial cells and further transmission into distal cells. Immunofluorescent localization of hMR on vaginal epithelial cells of seronegative females from the general population included the control group (n = 52) and seronegative females from serodiscordant couples. There was PCR amplification of DNA from peripheral blood mononuclear cells (PBMCs) of the serodiscordant females for the CCR5 gene flanking the CCR5-Delta 32 region; PCR amplification and sequencing of the C2-V3 region of HIV variants in PBMCs and sperm of the infected male partners of the serodiscordant couples; and the presence of hMR on 0-11% of the vaginal epithelial cells of seronegative females (n = 39) from serodiscordant couples and 90-95% that of a control group of females (n = 52). Nine of these serodiscordant females did not show a CCR5-Delta 32 deletion. The translated amino acid sequence of the C2-V3 region of the env gene of HIV-1C in PBMCs (n = 9) and sperm (n = 5) of the male partners showed the presence of distinct variants and the variation in PBMCs and sperm of serodiscordant males was almost similar to that of infected males from concordant couples. The presence of hMR in a smaller number of vaginal epithelial cells of serodiscordant females prevented binding and HIV entry into these cells and therefore prevented sexual transmission of HIV.