HIV-infected Langerhans cells preferentially transmit virus to proliferating autologous CD4+ memory T cells located within Langerhans cell-T cell clusters.

Langerhans cells (LC) are likely initial targets for HIV following sexual exposure to virus and provide an efficient means for HIV to gain access to lymph node T cells. The purpose of this study was to examine the nature of the CD4(+) T cell that becomes infected by HIV-infected LC. We infected human LC within tissue explants ex vivo and then, 3 days later, cocultured HIV-infected LC with different subsets of autologous CD4(+) T cells. Using multicolor flow cytometric analyses of LC-CD4(+) T cell cocultures, we documented that HIV-infected LC preferentially infected memory (as compared with naive) CD4(+) T cells. Proliferating and HIV-infected CD4(+) memory T cells were more frequently detected in conjugates of LC and autologous CD4(+) T cells, suggesting that T cells become activated and preferentially get infected through cluster formation with infected LC, rather than getting infected with free virus produced by single HIV-infected LC or T cells. p24(+) Memory CD4(+) T cells proliferated well in the absence of superantigen; by contrast, p24(+) T cells did not divide or divided only once in the presence of staphylococcal enterotoxin B, suggesting that virus production was rapid and induced apoptosis in these cells before significant proliferation could occur. These results highlight that close interactions between dendritic cells, in this case epidermal LC, and T cells are important for optimal HIV replication within specific subsets of CD4(+) T cells. Disrupting cluster formation between LC and memory CD4(+) T cells may be a novel strategy to interfere with sexual transmission of HIV.