Uterine Epithelial Cell Regulation of DC-SIGN Expression Inhibits Transmitted/Founder HIV-1 Trans Infection by Immature Dendritic Cells

et al. (2010) Uterine Epithelial Cell Regulation of DC-SIGN Expression Inhibits Transmitted/ Founder HIV-1 Trans Infection by Immature Dendritic Cells. PLoS ONE 5(12): e14306. doi:10.1371/journal.pone.0014306 Uterine Epithelial Cell Regulation of DC-SIGN Expression Inhibits Transmitted/Founder HIV-1 Trans Infection by Immature Dendritic Cells Daniel O. Ochiel 0 Christina Ochsenbauer 0 John C. Kappes 0 Mimi Ghosh 0 John V. Fahey 0 Charles R. 0 Roberto F. Speck, University Hospital Zurich, Switzerland 0 1 Department of Physiology, Dartmouth Medical School , Lebanon, New Hampshire , United States of America, 2 Department of Medicine, University of Alabama , Birmingham , Alabama, United States of America, 3 Department of Microbiology, University of Alabama , Birmingham , Alabama, United States of America, 4 Department of Pathology, University of Alabama , Birmingham, Alabama , United States of America Background: Sexual transmission accounts for the majority of HIV-1 infections. In over 75% of cases, infection is initiated by a single variant (transmitted/founder virus). However, the determinants of virus selection during transmission are unknown. Host cell-cell interactions in the mucosa may be critical in regulating susceptibility to infection. We hypothesized in this study that specific immune modulators secreted by uterine epithelial cells modulate susceptibility of dendritic cells (DC) to infection with HIV-1. Methodology/Principal Findings: Here we report that uterine epithelial cell secretions (i.e. conditioned medium, CM) decreased DC-SIGN expression on immature dendritic cells via a transforming growth factor beta (TGF-b) mechanism. Further, CM inhibited dendritic cell-mediated trans infection of HIV-1 expressing envelope proteins of prototypic reference. Similarly, CM inhibited trans infection of HIV-1 constructs expressing envelopes of transmitted/founder viruses, variants that are selected during sexual transmission. In contrast, whereas recombinant TGF- b1 inhibited trans infection of prototypic reference HIV-1 by dendritic cells, TGF-b1 had a minimal effect on trans infection of transmitted/founder variants irrespective of the reporter system used to measure trans infection. Conclusions/Significance: Our results provide the first direct evidence for uterine epithelial cell regulation of dendritic cell transmission of infection with reference and transmitted/founder HIV-1 variants. These findings have immediate implications for designing strategies to prevent sexual transmission of HIV-1. - Funding: This publication was made possible by National Institutes of Health Grants AI51877 and AI13541 (CRW), and U01-AI067854 (JCK and CO). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. Since it was initially reported over 25 years ago, HIV-1 infection has remained the most challenging health issue [1]. Whereas tangible progress has been made with regards to treatment and prevention efforts [2], there is little knowledge about the biology of sexual transmission, the predominant mode of HIV-1 acquisition [3,4]. This presents a major hurdle for strategies to reduce mucosal transmission of HIV-1, such as microbicides and vaccines. Therefore, defining the determinants of mucosal transmission remains a critical priority to the prevention of sexual acquisition of HIV-1. Sexual transmission is almost exclusively initiated by HIV-1 variants with tropism for the CCR5 co-receptor (R5 viruses) [5,6]. The mechanisms that facilitate preferential transmission of R5 viruses are not fully understood. Further, recent studies examining sequence composition of transmitted viruses indicate that infection is initiated by a single variant in over 75% of heterosexual HIV-1 transmission [6,7,8,9,10]. The genetic and biological characteristics of these transmitted/founder variants are under investigation [6,9,11]. In the female reproductive tract (FRT) mucosa, a variety of immune cell types are found, many of which are possible direct targets for HIV-1 infection [12]. Target cells in the upper and lower FRT include CD4+ T lymphocytes, macrophages, dendritic cells (DC) and epithelial cells [13,14,15,16,17]. Despite their presence, questions remain to be answered with regard to the initial target cells for infection and how HIV-1 is propagated following mucosal exposure. A spectrum of soluble immune mediators, including cytokines, chemokines and growth factors, constitute a local milieu in the sub-mucosa that regulates immune target cells [18]. With regard to HIV-1 infection via the FRT, we and others have demonstrated that these soluble mediators, most of which are hormonally controlled, regulate the expression of receptors and coreceptors that facilitate infection with HIV-1 [15,19,20]. Dynamic cell-cell communication in the FRT mucosa may influence the efficiency of HIV-1 transmission. For example, we previously described the presence of lymphoid aggregates in the endometrium, within which are CD14+ cells in close proximity to epithelial cells [15,21]. The close anatomical juxtaposition of these myeloid cells may represent a mechanism for the regulation of their function by overlying epithelial cells. Evidence for cell-cell communication via local secretions is in part based on our findings that secretions from primary human uterine epithelial cells (UEC) [22,23] modulate the differentiation and maturation processes leading to the generation of tolerogenic DC [24,25]. In previous studies, we determined the mechanisms by which uterine epithelial cell conditioned medium (CM) modulates DC function [24]. DC which were differentiated in the presence of CM (i.e. CM-DC) had reduced surface expression of CD86 and CD83. In contrast, expression of CD1a, CD80, HLA-DR, CD14 and CD163 was not altered significantly with CM-DC relative to that seen on control DC (i.e. Con-DC). Further, following activation with TLR3 ligand (poly(I:C)) or TLR4 ligand (LPS) the expression of CD80, CD86 and CD83 were decreased on CM-DC relative to Con-DC. In addition, CM-DC responded to LPS or PIC stimulation with enhanced IL-10 production. RT-PCR analysis showed that CM-DC significantly increased expressed of mRNA for indoleamine 2,3-Dioxygenase (IDO), an immune tolerance promoting enzyme. Finally, in a mixed leukocyte reaction (MLR) assay, CM-DC had significantly lower allogeneic proliferative responses when compared to Con-DC. Interestingly, uterine epithelial cell CM does not appear to induce the development of Langerhans cells from monocytes, as indicated by the lack of expression of Langerin and E-cadherin (data not shown). These initial findings underscore the critical role of cell-cell interactions in regulating immune responses in the endometrium. Mucosal DC are believed to play an integral role in sexual transmission of HIV-1. For example, DC exp (...truncated)