While HIV-1 has been reported to induce DC maturation [47,62], there is considerably more evidence to suggest that HIV-1 does not induce maturation [44,63–67]. Because one measure of DC maturation is the surface
expression of distinct surface molecules, we first determined if HIV-1 infection influences the cell surface phenotype of MDDC during the course of maturation. After incubation with Mitomycin C HIV-1 for 24 h and 48 h of culture, there was no change in the expression of CD80, CD86, CD83, CD40, CCR7, MHC-I or MHC-II, indicating that HIV-1 itself was not capable of inducing DC maturation. There was, however, an increase in DC-SIGN expression following HIV-1 infection (Fig. 3a). After iMDDC were infected with HIV-1 and then stimulated to mature, they expressed lower levels of CCR7 and MHC-II than that observed in uninfected cells (Fig. 3b,c), suggesting that HIV-1 inhibits the full maturation of iMDDCs. Functional analysis. Analyses were conducted as follows. 1. Endocytosis: while a phenotypic analysis of MDDC can be used to partially
identify the maturation status of an MDDC, determining the effects of HIV-1 on the functional character of MDDC over the course of maturation is required to elucidate a comprehensive picture of the effects of HIV-1 on MDDC maturation. One critical function of DC is the uptake of antigen from Selleckchem MG132 the periphery for processing and presentation in lymphoid organs . After endocytosing antigens, immature DC undergo maturation and move from the anatomic periphery to secondary lymphoid organs where their role becomes that of antigen presentation and not uptake [3,68]. As a measure of endocytic activity, and therefore the maturation state
of MDDC, the effect of HIV-1 on dextran uptake was evaluated. As expected, maturation of uninfected iMDDC resulted in Nintedanib (BIBF 1120) a decrease in FITC–dextran uptake (Fig. 4a). While HIV infection had no impact on the ability of iMDDC to take up dextran (Fig. 4b), HIV-1 infection was associated with blunted down-regulation of endocytosis by iMDDC (Fig. 4c). HIV-1 infection therefore appeared to inhibit maturation reflected by the fact that HIV-1 infected DC partially retain their endocytic function. 2. Antigen presentation: a primary function of DC is the presentation of antigens to naive T cells in peripheral lymphoid tissue . The effect of HIV-1 infection on the ability of MDDC to present antigen to autologous CD8+ T cells was determined by incubating HIV-1-infected MDDC with autologous PBMC in the presence of a CEF peptide pool, as described previously . After culturing CEF peptide-pulsed iMDDC with autologous PBMCs for 7 days, CD8+ T cells proliferated as expected (Fig. 5). When iMDDC were infected with HIV-1, however, CD8+ T cell proliferation in response to the CEF peptide pool was not observed (Fig. 5), suggesting that HIV-1 infection of DC prevented or interfered with antigen presentation. 3.