The human foreskin is an immunologically active tissue containing both lymphoid and myeloid cells. The foreskin has been shown to play an important role in HIV infection as its complete removal during MMC has been shown to reduce the risk of HIV acquisition by up to 60%. CD4+/CCR5+ Langerhan’s cells (LCs) and macrophages are known to be resident in both inner and outer foreskin tissue and are potential HIV target cells. To better understand whether foreskin-derived myeloid cells are promiscuous to HIV-1, we exposed them to HIV in ex-vivochallenge assays.
Foreskin cells were allowed to migrate out of isolated epidermal tissue from adult South African men undergoing vMMC. Briefly, epidermal sheets were obtained after dispase digestion of 1cm2foreskin tissue. Cells were collected after 48-hour incubation and remnant tissue resident cells were enzymatically isolated using liberase (5 mg/ml). Epidermal LCs and macrophages from the inner and outer foreskins were identified using a multiparameter flow panel: CD207, CD1a, CD80/86, HLA-DR, CD11c, CD209, CD206, CD14, CD4, CCR5, CD169 and zombie (live/dead). Ex-vivoHIV challenge assays were set up using migratory cells and HIV infection was detected using reporter genes, GFP and mCherry as well as p24 antibody.
Tissue resident LCs and macrophages were isolated. LCs (4.8 x 105) were more abundant than macrophages (9.4 x 101), with averages of 5% and 0.009% of the entire cell population respectively. Both migrating CD1a+, CD207+ LCs and CD209+, CD163+ macrophages expressed higher levels of CD80/86 (p=0.006) and HLA-DR (p=0.02) relative to cells that remained in the tissue co-expressing these surface antigens (p=0.015). HIV exposed CD11c+ LCs and macrophages expressed 2% mCherry, 13% p24 and absolute CD4 downregulation.
LCs and macrophages that migrate from foreskin epidermal sheets express high levels of maturation and activation markers CD40, CD80/86 and HLA-DR, they are therefore activated and susceptible to HIV infection as evidenced by reporter gene (mCherry) and p24 expression. CD4 downregulation also indicates HIV infection.