Dendritic cells (DCs) are professional antigen presenting cells and play a central role in both innate and adaptive immunity. A decrease in one or both subsets of DC has been reported in HIV-1 infected patients from different populations. The status of DC subsets in subjects at high risk for HIV-1 such as Injecting Drug Users (IDUs) has not been reported so far.

Blood samples from 15 healthy individuals, 15 IDU and 15 HIV-1 positive patients were collected and informed consent was obtained. Plasmacytoid and myeloid DCs were accessed by four-color flow cytometry. The plasma level cytokines and HIV-1 viral load were determined.

We observed a significant decrease in the total DCs and pDCs population in HIV-1 infected patients (%DCs p = 0.0132, %pDCs p = 0.0281) and IDUs (%DCs p = 0.006, %pDCs (p>0.0001) as compared to healthy individuals. The plasma levels of IFN-γ was significantly lower while level of IL-10 was significantly higher in HIV-1 infected patients as compared to IDUs (p = 0.0062, for IFN- γ and p = 0.0071 for IL-10) and healthy subjects (p = 0.004 for IFN- γ and p = 0.0068 for IL-10).

This is the first study to characterize the dendritic cells subpopulations in IDUs who are at high risk for HIV-1 infection. Further longitudinal studies on the status of dendritic cell subpopulations and their correlation with the cytokine profile will enable the elucidation of the precise role of dendritic cells in HIV-1 infection.