HIV-1-infected monocyte-derived dendritic cells do not undergo maturation but can elicit IL-10 production and T cell regulation

Abstract

Dendritic cells (DCs) undergo maturation during virus infection and thereby become potent stimulators of cell-mediated immunity. HIV-1 replicates in immature DCs, but we now find that infection is not accompanied by many components of maturation in either infected cells or uninfected bystanders. The infected cultures do not develop potent stimulating activity for the mixed leukocyte reaction (MLR), and the DCs producing HIV-1 gag p24 do not express CD83 and DC-lysosome-associated membrane protein maturation markers. If different maturation stimuli are applied to DCs infected with HIV-1, the infected cells selectively fail to mature. When DCs from HIV-1-infected patients are infected and cultured with autologous T cells, IL-10 was produced in 6 of 10 patients. These DC-T cell cocultures could suppress another immune response, the MLR. The regulation was partially IL-10-dependent and correlated in extent with the level of IL-10 produced. Suppressor cells only developed from infected patients, rather than healthy controls, and the DCs had to be exposed to live virus rather than HIV-1 gag peptides or protein. These results indicate that HIV-1-infected DCs have two previously unrecognized means to evade immune responses: maturation can be blocked reducing the efficacy of antigen presentation from infected cells, and T cell-dependent suppression can be induced.

Figures

Fig. 1.

p24 expression by HIV-1-infected iDCs. (a) DCs were exposed to the BaL isolate of HIV-1 for 2 h at 37°C. The FACS was used to monitor HIV infection (FITC anti-gag p24) and surface antigens (y axis) 5 days later. (b) DCs were infected without or with 1 μM AZT and stained for CD11c and p24. One of six similar experiments is shown.

Fig. 2.

HIV-1 infection does not mature DCs. (a) iDC and DCs matured with a cytokine mixture (mDC) were infected with BaL and stained for the DC–LAMP maturation marker and p24 (intracellular staining). Similar findings were made in eight experiments, including other maturation stimuli like LPS and CD40 ligation (Table 2). (b) The iDCs and mDCs were infected with Yu2-HIV-1/GFP and analyzed for maturation markers (y axis) by FACS after 5 days (surface staining). (c) Allo MLR stimulation was monitored by CFSE dilution by using CFSE-labeled T cells and the indicated DCs. The experiment shown is representative of three or more experiments.

Fig. 3.

Effect of maturation stimuli added to HIV-1-infected DCs. iDCs were infected for 2 h. After washing, maturation cytokines (or LPS or CD40L, Table 2) were added immediately (time 0) or at the indicated times. Cells were analyzed at 5 days by PCR for HIV-1 reverse transcripts (a) and FACS for expression of p24 and the maturation marker DC–LAMP (b).

Fig. 4.

Detection and expansion of T cells secreting IFN-γ and IL-10. iDCs were generated from HIV-1-infected patients (a) or uninfected donors (b), infected with HIV-1 for 4 days, and added to autologous T cells. IFN-γ and IL-10 production were assessed by ELISPOT immediately (day 0) or after 7 days of coculture. Each symbol is a different patient. Statistical comparisons (P values at top) between uninfected and infected DCs were made by using Student's t tests.

Fig. 5.

Cocultures of infected immature DCs and T cells inhibit a MLR. DCs from HIV-1-infected patients were infected or not with HIV-1 for 4 days and then added to autologous T cells for 7 days. The indicated cells (Center) were then placed in a transwell chamber. In the lower wells, an MLR was generated, and proliferation was assessed by CFSE dilution. T CFSE indicates T cells cultured without DCs. (A)(Left) Correlation between suppression of the MLR and production of IL-10 (Table 2). (Right) Comparison between immature and mature DCs to show the suppression by iDC HIV + T (fourth row). (b and c) Comparison between iDCs infected with HIV-1 or pulsed with gag protein (b) or peptides (c). (d) Neutralizing anti-IL-10 or isotype control antibody was added at 10 μg/ml, and healthy controls studied in parallel (Left).