Maturation of Blood-Derived Dendritic Cells Enhances Human Immunodeficiency Virus Type 1 Capture and Transmission

Abstract

Dendritic cells (DCs) are specialized antigen-presenting cells. However, DCs exposed to human immunodeficiency virus type 1 (HIV-1) are also able to transmit a vigorous cytopathic infection to CD4؉ T cells, a process that has been frequently related to the ability of DC-SIGN to bind HIV-1 envelope glycoproteins. The maturation of DCs can increase the efficiency of HIV-1 transmission through trans infection. We aimed to comparatively study the effect of maturation in monocyte-derived DCs (MDDCs) and bloodderived myeloid DCs during the HIV-1 capture process. In vitro capture and transmission of envelopepseudotyped HIV-1 and its homologous replication-competent virus to susceptible target cells were assessed by p24 gag detection, luciferase activity, and both confocal and electron microscopy. Maturation of MDDCs or myeloid DCs enhanced the active capture of HIV-1 in a DC-SIGN-and viral envelope glycoprotein-independent manner, increasing the life span of trapped virus. Moreover, higher viral transmission of mature DCs to CD4 ؉ T cells was highly dependent on active viral capture, a process mediated through cholesterol-enriched domains. Mature DCs concentrated captured virus in a single large vesicle staining for CD81 and CD63 tetraspanins, while immature DCs lacked these structures, suggesting different intracellular trafficking processes. These observations help to explain the greater ability of mature DCs to transfer HIV-1 to T lymphocytes, a process that can potentially contribute to the viral dissemination at lymph nodes in vivo, where viral replication takes place and there is a continuous interaction between susceptible T cells and mature DCs.

HIV-1 Capture and Antigen Presentation by Dendritic Cells: Enhanced Viral Capture Does Not Correlate with Better T Cell Activation

“…We previously showed that mDC LPS capture greater amounts of HIV-1 than do iDC, thus facilitating viral transmission to T lymphocytes (6). Before evaluating the Ag-presentation abilities of iDC and mDC, we studied the viral capture and trans-infection capabilities of DC matured for 48 h with LPS or with ITIP, the gold standard for DC maturation in immunotherapy (14,20).…”

“…After incubation, cells were extensively washed with PBS to remove uncaptured viral particles and lysed with 0.5% Triton X-100 at a final concentration of 5 3 10 5 cells/ml. Lysates were cleared of cell debris by centrifugation to measure intracellular p24 Gag Ag content using an ELISA (PerkinElmer), as described elsewhere (6). Before lysis, 10 4 HIV-1-pulsed DC were cocultured with the TZM-bl reporter cell line at a ratio of 1:1/well in a 96-well plate at a final volume of 100 ml.…”

“…For electron microscopy analysis of viral capture by DC, cells were processed as described elsewhere (6). In brief, 3 3 10 6 mDC LPS were pulsed at 37˚C overnight with 1600 ng p24 Gag of HIV NL4-3 or HIV NL4-3DIN .…”

“…Although it is well documented that the higher viral capture of mDC LPS results in increased trans-infection to target cells (4,6,8), little is known about the Ag-presentation ability of this DC subset. It was recently suggested that Mycobacterium tuberculosis promotes HIV-1 transinfection similarly to LPS, while suppressing class II Ag processing by DC (19).…”

“…For instance, DC matured in the presence of PGE 2 are inefficient in HIV-1 transmission to T lymphocytes (8), whereas other maturation factors, such as TNF and LPS, are very potent in transmission of HIV-1 (16). We previously showed that mDC LPS (i.e., both monocyte-derived and blood-derived myeloid DC) capture higher amounts of HIV-1 than do immature DC (iDC) (6) and that this finding correlated with a greater ability to transfer HIV-1 to susceptible target cells (6,9,17). In addition, plasma LPS levels, which are significantly augmented in chronically HIV-1-infected individuals as the result of increased microbial translocation, might also support the contribution of mDC to the spread of HIV-1 in vivo (18).…”