Monocytes modulate enhancement of HIV-1 replication by Mycobacterium tuberculosis

Abstract

To investigate the effects of Mycobacterium tuberculosis on HIV-1 replication, peripheral blood mononuclear cells (PBMC) of bacille Calmette-Guerin (BCG)-vaccinated donors and non-BCG-vaccinated donors were infected in vitro with a lymphotropic isolate of HIV-1 and cultured in the presence of purified protein derivative (PPD). Addition of PPD resulted in enhanced HIV-1 replication and lymphoproliferation in BCG-vaccinated donor PBMC, while PPD had no such effects in control PBMC. HIV-1 replication increased even more when monocytes were removed from PBMC, while lymphoproliferation was decreased. High percentages of monocytes were associated with a decreased HIV-1 replication and proliferation that could not be reversed by addition of antibodies against the cytokines IL-1, transforming growth factor-beta (TGF-beta) or indomethacin. PPD stimulates PBMC to release IL-10, a cytokine known to down-regulate proliferation and HIV-1 replication. PPD-induced effects on proliferation as well as HIV-1 replication could be partially blocked by adding a monoclonal antibody against MHC class II molecules, suggesting that part of the mechanism of PPD-induced enhancement is T memory cell activation.

Fig. 1

Purified protein derivative (PPD)-induced HIV-1 replication in peripheral blood mononuclear cells (PBMC) of bacille Calmette–Guérin (BCG)-vaccinated and non-BCG-vaccinated donors. PBMC of BCG-vaccinated (□) and non-BCG-vaccinated donors (▪) were cultured in the presence of increasing amounts of PPD for 7 days. Before the addition of PPD the cells were infected for 2 h with HIV-1. The amount of HIV-1 produced during the total incubation period was assessed by a p24 ELISA. Relative amounts of p24 were determined and expressed as stimulation index (SI), amount of p24 above background level. Mean ± s.d. of five individuals is shown. Each determination was performed in triplicate. *P < 0.05; **P < 0.01; ***P < 0.005.

Fig. 2

Purified protein derivative (PPD)-induced HIV-1 replication in peripheral blood mononuclear cells (PBMC) and peripheral blood lymphocytes (PBL) of bacille Calmette–Guérin (BCG)-vaccinated donors. Comparison of PBMC (□) and PBL (▪) of BCG-vaccinated donors in their capacity to promote HIV-1 replication after stimulation by increasing amounts of PPD. For details, see Fig. 1.

Fig. 3

Purified protein derivative (PPD)-induced HIV-1 replication and proliferation of peripheral blood mononuclear cells (PBMC) and peripheral blood lymphocytes (PBL) of bacille Calmette–Guérin (BCG)-vaccinated donors. The effect of PPD on HIV-1 replication in PBMC (a) and PBL (b) was measured after 7 days of incubation (○). For proliferation assays, ³H-TdR incorporation was measured after 4 days of incubation (•). Relative amounts of p24 and ³H-TdR incorporation were determined and expressed as stimulation index (SI). Mean ± s.d. for HIV-1 replication (n = 5) and ³H-TdR incorporation (n = 3) are shown. Each determination was performed in triplicate. *P < 0.05; **P < 0.01; ***P < 0.005.

Fig. 4

Suppression of purified protein derivative (PPD)-induced HIV-1 replication by increasing amounts of monocytes. HIV-1-infected peripheral blood lymphocytes (PBL) were incubated together with different percentages of autologous monocytes in the presence of 10 μg/ml PPD. After 7 days, p24 production was determined. Mean ± s.d. of three individuals is shown. Each determination was performed in triplicate.

Fig. 5

Suppression of purified protein derivative (PPD)-induced lymphoproliferation by increasing amounts of monocytes. Peripheral blood lymphocytes (PBL) were incubated together with different percentages of autologous monocytes in the presence of 10 μg/ml PPD. Lymphoproliferation was determined after 7 days of incubation. Mean ± s.d. of three individuals is shown. Each determination was performed in triplicate.

Fig. 6

Partial inhibition of purified protein derivative (PPD)-induced HIV-1 replication by anti-MHC class II MoAb. HIV-1-infected peripheral blood lymphocytes (PBL) of bacille Calmette–Guérin (BCG)-vaccinated donors were incubated with 10 μg/ml PPD for 7 days, in the presence (PdV5.2) or absence (−) of anti-MHC class II MoAb PdV5.2, and p24 production was determined. As an isotype control, anti-CD14 MoAb 60bca was used (control). Mean ± s.d. of three individuals is shown. Each determination was performed in triplicate.