ABSTRACT
Tissue mononuclear phagocytes (MNP) are specialised in pathogen detection and antigen presentation. As such they deliver HIV to its primary target cells; CD4 T cells. Most MNP HIV transmission studies have focused on epithelial MNPs. However, as mucosal trauma and inflammation are now known to be strongly associated with HIV transmission, here we examine the role of sub-epithelial MNPs which are present in a diverse array of subsets. We show that HIV can penetrate the epithelial surface to interact with sub-epithelial resident MNPs in anogenital explants and define the full array of subsets that are present in the human anogenital and colorectal tissues that HIV may encounter during sexual transmission. In doing so we identify two subsets that preferentially take up HIV, become infected and transmit the virus to CD4 T cells; CD14+CD1c+ monocyte-derived dendritic cells and langerin-expressing conventional dendritic cells 2 (cDC2).
Subject(s)
Anal Canal/cytology , Antigens, CD/metabolism , Dendritic Cells/metabolism , Genitalia/cytology , HIV-1/physiology , Lectins, C-Type/metabolism , Mannose-Binding Lectins/metabolism , Monocytes/metabolism , CD4-Positive T-Lymphocytes/immunology , Cell Shape , Collagenases/metabolism , Dermis/metabolism , HIV Infections/immunology , HIV Infections/virology , Humans , Lipopolysaccharide Receptors/metabolism , Mucous Membrane/metabolism , Phagocytes/metabolism , Phenotype , Receptors, CCR5/metabolism , Sialic Acid Binding Ig-like Lectin 1/metabolism , Transcription, GeneticABSTRACT
Mononuclear phagocytes are present in skin and mucosa and represent one of the first lines of defense against invading pathogens, which they detect via an array of pathogen-binding receptors expressed on their surface. However, their extraction from tissue is difficult, and the isolation technique used has functional consequences on the cells obtained. Here, we compare mononuclear phagocytes isolated from human skin using either enzymatic digestion or spontaneous migration. Cells isolated via enzymatic digestion are in an immature state, and all subsets are easily defined. However, cells isolated by spontaneous migration are in a mature state, and CD141 cross-presenting DCs (cDC1) are more difficult to define. Different pathogen-binding receptors are susceptible to cleavage by blends of collagenase, demonstrating that great care must be taken in choosing the correct enzyme blend to digest tissue if carrying out pathogen-interaction assays. Finally, we have optimized mononuclear phagocyte culture conditions to enhance their survival after liberation from the tissue.
