In vitro infection of human epidermal Langerhans cells with HIV

Human immunodeficiency virus type 1 strains of subtypes B and E replicate in cutaneous dendritic cell-T-cell mixtures without displaying subtype-specific tropism

A report that genetic subtype E human immunodeficiency virus type 1 (HIV-1) strains display a preferential tropism for Langerhans cells (epidermal dendritic cells [DCs]) compared to genetic subtype B strains suggested a possible explanation for the rapid heterosexual spread of subtype E strains in Thailand (L. E. Soto-Ramirez et al., Science 271:1291-1293, 1996). In an independent system, we applied subtype E and B isolates to skin leukocytes, since skin is a relevant model for the histologically comparable surfaces of the vagina and ectocervix. Isolates of both HIV-1 subtypes infected DC-T-cell mixtures, and no subtype-specific pattern of infection was observed. Purified DCs did not support the replication of strains of either subtype B or E. Our findings do not support the conclusion that subtype E strains have a preferential tropism for DCs, suggesting that other explanations for the rapid heterosexual spread of subtype E strains in Asia should be considered.

The skin as target, vector, and effector organ in human immunodeficiency virus disease

Langerhans cells are CD4+ antigen-presenting cells in the dendritic cell family that can initiate primary and secondary immune responses after emigration from skin and mucosa. Because of these properties, Langerhans cells have been proposed as potential targets for human immunodeficiency virus (HIV) infection and as potential vectors for the transmission of primary HIV infection to T cells after mucosal exposure. In support of this theory, previous investigative studies have demonstrated that Langerhans cells are targets for HIV infection both in vivo and in vitro and that HIV-pulsed Langerhans cells, as well as blood dendritic cells, induce a productive infection in co-cultured T cells in vitro. In addition, Langerhans cell dysfunction has been proposed as contributing to the pathogenesis of some of the cutaneous manifestations observed in HIV+ individuals. In a recent study, we detected Langerhans cell dysfunction in patients with acquired immune deficiency syndrome, but not in earlier stages of HIV disease. Here we review previous and current investigative studies on HIV and the skin, with an emphasis on Langerhans cells, and discuss possible future investigations in this field.

Dendritic cells: clinical aspects

Clinical aspects of dendritic cells have yet to be studied intensively. One obstacle, that of isolating and identifying dendritic cells from human blood and other tissues like skin and tonsil, is being overcome, although the field would be facilitated by dendritic-cell-specific monoclonals or other probes. Many of the specializations that dendritic cells exhibit as antigen-presenting cells in other mammals are being verified in man. New properties, particularly their capacity to induce clonal expansion of T cells and to be infected with retroviruses, have become evident. Four areas where it may be productive to give more attention to dendritic cells are transplantation, protective T-cell immunity, autoimmunity and HIV-1 infection.