Restricted HIV type 1 replication under serum-free culture conditions in human monocyte-derived macrophages

HIV-1 infection inhibits cytokine production in human thymic macrophages

OBJECTIVE

The thymus serves as a critical site of T-lymphocyte ontogeny and selection. Thymic infection by HIV-1 is known to disrupt thymocyte maturation by both direct and indirect means; however, the mechanism behind these effects remains poorly defined. Macrophages represent one of the most important peripheral targets of HIV-1 infection, are resident in the thymic stroma, and play a central role in thymocyte maturation.

MATERIALS AND METHODS

Studies presented here define three primary features and outcomes of thymic macrophages (TM) and HIV-1 infection: (1) The distinctive TM phenotype (surface markers and cytokine production measured by immunofluorescence, fluorescence-activated cell sorting, and reverse transcriptase polymerase chain reaction) relative to macrophages from other sources (blood [monocyte-derived macrophages] and bone marrow); (2) infection of TM by different HIV-1 subtypes (X4, R5, and X4/R5) measured by enzyme-linked immunosorbent assay and polymerase chain reaction; and (3) consequences of HIV-1 infection on cytokine production by TM measured by reverse transcriptase polymerase chain reaction.

RESULTS

The results demonstrate that TM display a distinctive phenotype of HIV-1 receptors (CD4(lo), CXCR4(lo), CCR5(med), CCR3(hi)), chemokine production (macrophage inflammatory protein-1α(+); regulated on activation, normal T expressed and secreted(+); macrophage inflammatory protein-1b(-); stromal cell-derived factor -1(-)); and cytokine production (tumor necrosis factor-α(+), interleukin-8(+), macrophage colony-stimulating factor(+), interleukin-6(-)) relative to either monocyte-derived macrophages or bone marrow. TM were infected in vitro with R5 and X4/R5-tropic HIV-1 subtypes, and developed syncytia formation during long-term X4/R5 culture. In contrast, TM supported only transient replication of X4-tropic HIV-1. Lastly, infection of TM with HIV-1 abolished the production of all cytokines tested in long-term in vitro cultures.

CONCLUSIONS

Taken together, these results indicate that TM are a potential direct target of in situ HIV-1 infection, and that this infection may result in the disruption of macrophage functions that govern normal thymocyte maturation.

A hollow-fiber bioreactor for expanding HIV-1 in human lymphocytes used in preparing an inactivated vaccine candidate

An inactivated HIV vaccine intended to elicit broadly neutralizing antibodies is designed to use a pool of population-prevalent HIV-1 from plasma (PHIV), isolated before evolution of antibody-mediated genetic mutations. A suitable cell substrate (CS) for isolating such PHIV is peripheral blood mononuclear cells (PBMC) after stimulating with phytohemagglutinin (PHA) and interleukin-2 (IL-2). Feasibility of employing a hollow-fiber bioreactor under optimized conditions was investigated for large-scale expansion and efficient recovery of concentrated PHIV. Each CS batch was infected in vitro with a prototype PHIV, the infected cells were introduced into the bioreactor for 7-10 days in co-culture, and the cell-free supernatants were assayed for p24 antigen as an index of HIV synthesis. PBMC versus CD8-depleted (CD8D) CS, 20kDa versus 5kDa molecular weight cut-off (MWCO) bioreactor cartridges, 7- versus 10-day culture periods, and varying concentrations of IL-2, fetal bovine serum (FBS) and glucose content in the medium were functionally evaluated for p24 yield. PBMC cultures in 20kDa MWCO cartridges with 15% FBS, 80IU/mL IL-2 and 2.0g/L glucose produced the highest p24 yield; however, CD8D-CS, 20-30% FBS and 80 IU/mL IL-2 within 5kDa cartridges and 2.0 g/L glucose in the circulating medium was more cost-effective for synthesis of virion p24.

In vitro activation of feline immunodeficiency virus in ramified microglial cells from asymptomatically infected cats

Intravenous infection of cats with feline immunodeficiency virus was used as a model system to study activation of virus replication in brain-resident microglial cells in vitro. Virus release by ramified microglial cells isolated from subclinically infected animals was detectable in cell-free tissue culture supernatant only by reverse transcription and nested PCR of gag-specific RNA sequences and not by virion-associated reverse transcriptase activity. In contrast, cocultivation of in vivo-infected microglial cells with mitogen-activated peripheral blood mononuclear cells (PBMC) regularly allows detection of high virus yields in cell-free tissue culture fluid. Besides uptake and multiplication of microglia-derived virus in PBMC, release of virus from microglia is stimulated by cell contact with PBMC. The data suggest that T lymphocytes patrolling the central nervous system could reactivate the semilatent state of lentiviruses in microglial cells in the course of clinically silent central nervous system infection.

The susceptibility of macrophages to human immunodeficiency virus type 1 X4 isolates depends on their activation state

The demonstration that macrophages express CXCR4 has led to a reexamination of their susceptibility to human immunodeficiency (HIV)-1 X4 strains. Here, we examined the susceptibility to X4 HIV-1Lai of two previously characterized macrophage populations, obtained either as 1) adherent cells of five-day cultures of blood mononuclear cells (PBMC), followed by two days without nonadherent PBMC nor added cytokines (MDM-5d); or 2) as adherent cells recovered from one-hour incubation of PBMC, which were cultured for seven days with macrophage colony-stimulating factor (MDM-MCSF). Exposing MDM-5d or MDM-MCSF to HIV-1Lai did not lead to productive infection, as indicated by a lack of (MDM-MCSF) or low (MDM-5d) viral p24 levels in culture supernatants. However, MDM-5d vigorously transmitted HIV-1 Lai to autologous T lymphocytes, which was not the case of HIV-1Lai-exposed MDM-MCSF. PCR analysis of the LTR RU5 region showed that X4 HIV-1Lai entered into both types of macrophages in the same manner as R5 HIV-1 BaL. However, in contrast to MDM-5d, there was a block of HIV-1 Lai retrotransciption in MDM-MCSF. Cytokine profile analysis of the two types of macrophages showed that TNF-alpha, IL-6 and RANTES levels were higher in MDM-5d than in MDM-MSCF, while the IL10 level was higher in MDM-MCSF, both producing similar IL16 levels. Altogether, these data indicate that HIV-1 X4 strains enter into macrophages but that their replication is blocked thereafter in a different manner according to the activation status of the cells.