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HIV-1 promotes intake of Leishmania parasites by enhancing phosphatidylserine-mediated, CD91/LRP-1-dependent phagocytosis in human macrophages.

Lodge R, Ouellet M, Barat C, Andreani G, Kumar P, Tremblay MJ - PLoS ONE (2012)

Bottom Line: This effect can be driven by HIV-1 Tat protein and transforming growth factor-beta (TGF-β).We determined also that enhanced CD91/LRP-1 surface expression occurs rapidly following HIV-1 infection, and is triggered by the activation of extracellular TGF-β.Thus, these results establish an intricate link between HIV-1 infection, Tat, surface CD91/LRP-1, TGF-β, and enhanced Leishmania phosphatidylserine-mediated phagocytosis.

View Article: PubMed Central - PubMed

Affiliation: Centre de Recherche en Infectiologie, Centre Hospitalier Universitaire de Québec-CHUL, Université Laval, Québec, Canada.

ABSTRACT
Over the past decade, the number of reported human immunodeficiency virus type-1 (HIV-1)/Leishmania co-infections has risen dramatically, particularly in regions where both diseases are endemic. Although it is known that HIV-1 infection leads to an increase in susceptibility to Leishmania infection and leishmaniasis relapse, little remains known on how HIV-1 contributes to Leishmania parasitaemia. Both pathogens infect human macrophages, and the intracellular growth of Leishmania is increased by HIV-1 in co-infected cultures. We now report that uninfected bystander cells, not macrophages productively infected with HIV-1, account for enhanced phagocytosis and higher multiplication of Leishmania parasites. This effect can be driven by HIV-1 Tat protein and transforming growth factor-beta (TGF-β). Furthermore, we show for the first time that HIV-1 infection increases surface expression of phosphatidylserine receptor CD91/LRP-1 on human macrophages, thereby leading to a Leishmania uptake by uninfected bystander cells in HIV-1-infected macrophage populations. The more important internalization of parasites is due to interactions between the scavenger receptor CD91/LRP-1 and phosphatidylserine residues exposed at the surface of Leishmania. We determined also that enhanced CD91/LRP-1 surface expression occurs rapidly following HIV-1 infection, and is triggered by the activation of extracellular TGF-β. Thus, these results establish an intricate link between HIV-1 infection, Tat, surface CD91/LRP-1, TGF-β, and enhanced Leishmania phosphatidylserine-mediated phagocytosis.

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HIV-1 infection exerts a different effect on MDM phagocytosis of zymosan particles or Leishmania parasites.Mock-infected control MDMs (panels A and C) or cells infected for 6 days with NL4-3-Bal-IRES-HSA reporter virus (panels B and D) were put in contact either with complement-opsonized Alexa488-tagged zymosan particles (panels A and B) or GFP-expressing Leishmania parasites (panels C and D) (both shown in green) for 1 hour. Next, excess zymosan particles/Leishmania amastigotes were washed out and MDMs cultured for an additional 3 hours. Cells were then fixed, mounted and immunostained for HSA (shown in red) and DNA (using DRAQ5, shown in blue) to detect HIV-1-infected cells and Leishmania DNA/host cell DNA, respectively. Shown are representative images obtained by confocal microscopy. Arrows indicate uninfected bystander MDMs displaying numerous internalized Leishmania parasites.
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pone-0032761-g001: HIV-1 infection exerts a different effect on MDM phagocytosis of zymosan particles or Leishmania parasites.Mock-infected control MDMs (panels A and C) or cells infected for 6 days with NL4-3-Bal-IRES-HSA reporter virus (panels B and D) were put in contact either with complement-opsonized Alexa488-tagged zymosan particles (panels A and B) or GFP-expressing Leishmania parasites (panels C and D) (both shown in green) for 1 hour. Next, excess zymosan particles/Leishmania amastigotes were washed out and MDMs cultured for an additional 3 hours. Cells were then fixed, mounted and immunostained for HSA (shown in red) and DNA (using DRAQ5, shown in blue) to detect HIV-1-infected cells and Leishmania DNA/host cell DNA, respectively. Shown are representative images obtained by confocal microscopy. Arrows indicate uninfected bystander MDMs displaying numerous internalized Leishmania parasites.

Mentions: Following 6 days of HIV-1 infection, we observed, using fluorescence confocal microscopy, that between 7 and 12% of MDMs (compiled from 9 independent donors) were productively infected with HIV-1 (i.e. HSA+) (data not shown). We then compared the capability of productively-infected and uninfected bystander MDMs, along with mock-infected control cells, to internalize GFP-expressing Leishmania parasites. We also assessed the phagocytic index of zymosan using complement-opsonized Alexa488-labeled particles based on the notion that such protein-carbohydrate complexes prepared from yeast cell wall are commonly used targets in phagocytosis assays. Representative confocal microscopy images of mock-infected (i.e. without HIV-1) (left panels) or MDMs inoculated with HIV-1 (i.e. both uninfected bystander/HSA- and productively-infected cells/HSA+) (right panels) are shown in Figure 1. As expected, quantitative analyses of confocal microscopy images indicated that mock-infected control cells internalized much higher amounts of zymosan particles than uninfected bystander (i.e. HSA−) (P = 0.006) and HIV-1-infected MDMs (i.e. HSA+) (P = 0.017) (Figure 2). Moreover, zymosan internalization was more efficient in uninfected bystander cells compared to HIV-1-infected MDMs. On the other hand, uninfected bystander MDMs exhibited a significant increase in Leishmania phagocytosis, as compared to either their HSA-expressing counterparts (P = 0.008) or the mock-infected control MDMs (P = 0.049). Therefore, opposite effects were observed in uninfected bystander MDMs compared to mock-infected control MDMs concerning the engulfment of opsonized zymosan particles (i.e. decrease) or the phagocytosis of Leishmania parasites (i.e. increase).


HIV-1 promotes intake of Leishmania parasites by enhancing phosphatidylserine-mediated, CD91/LRP-1-dependent phagocytosis in human macrophages.

Lodge R, Ouellet M, Barat C, Andreani G, Kumar P, Tremblay MJ - PLoS ONE (2012)

HIV-1 infection exerts a different effect on MDM phagocytosis of zymosan particles or Leishmania parasites.Mock-infected control MDMs (panels A and C) or cells infected for 6 days with NL4-3-Bal-IRES-HSA reporter virus (panels B and D) were put in contact either with complement-opsonized Alexa488-tagged zymosan particles (panels A and B) or GFP-expressing Leishmania parasites (panels C and D) (both shown in green) for 1 hour. Next, excess zymosan particles/Leishmania amastigotes were washed out and MDMs cultured for an additional 3 hours. Cells were then fixed, mounted and immunostained for HSA (shown in red) and DNA (using DRAQ5, shown in blue) to detect HIV-1-infected cells and Leishmania DNA/host cell DNA, respectively. Shown are representative images obtained by confocal microscopy. Arrows indicate uninfected bystander MDMs displaying numerous internalized Leishmania parasites.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3295765&req=5

pone-0032761-g001: HIV-1 infection exerts a different effect on MDM phagocytosis of zymosan particles or Leishmania parasites.Mock-infected control MDMs (panels A and C) or cells infected for 6 days with NL4-3-Bal-IRES-HSA reporter virus (panels B and D) were put in contact either with complement-opsonized Alexa488-tagged zymosan particles (panels A and B) or GFP-expressing Leishmania parasites (panels C and D) (both shown in green) for 1 hour. Next, excess zymosan particles/Leishmania amastigotes were washed out and MDMs cultured for an additional 3 hours. Cells were then fixed, mounted and immunostained for HSA (shown in red) and DNA (using DRAQ5, shown in blue) to detect HIV-1-infected cells and Leishmania DNA/host cell DNA, respectively. Shown are representative images obtained by confocal microscopy. Arrows indicate uninfected bystander MDMs displaying numerous internalized Leishmania parasites.
Mentions: Following 6 days of HIV-1 infection, we observed, using fluorescence confocal microscopy, that between 7 and 12% of MDMs (compiled from 9 independent donors) were productively infected with HIV-1 (i.e. HSA+) (data not shown). We then compared the capability of productively-infected and uninfected bystander MDMs, along with mock-infected control cells, to internalize GFP-expressing Leishmania parasites. We also assessed the phagocytic index of zymosan using complement-opsonized Alexa488-labeled particles based on the notion that such protein-carbohydrate complexes prepared from yeast cell wall are commonly used targets in phagocytosis assays. Representative confocal microscopy images of mock-infected (i.e. without HIV-1) (left panels) or MDMs inoculated with HIV-1 (i.e. both uninfected bystander/HSA- and productively-infected cells/HSA+) (right panels) are shown in Figure 1. As expected, quantitative analyses of confocal microscopy images indicated that mock-infected control cells internalized much higher amounts of zymosan particles than uninfected bystander (i.e. HSA−) (P = 0.006) and HIV-1-infected MDMs (i.e. HSA+) (P = 0.017) (Figure 2). Moreover, zymosan internalization was more efficient in uninfected bystander cells compared to HIV-1-infected MDMs. On the other hand, uninfected bystander MDMs exhibited a significant increase in Leishmania phagocytosis, as compared to either their HSA-expressing counterparts (P = 0.008) or the mock-infected control MDMs (P = 0.049). Therefore, opposite effects were observed in uninfected bystander MDMs compared to mock-infected control MDMs concerning the engulfment of opsonized zymosan particles (i.e. decrease) or the phagocytosis of Leishmania parasites (i.e. increase).

Bottom Line: This effect can be driven by HIV-1 Tat protein and transforming growth factor-beta (TGF-β).We determined also that enhanced CD91/LRP-1 surface expression occurs rapidly following HIV-1 infection, and is triggered by the activation of extracellular TGF-β.Thus, these results establish an intricate link between HIV-1 infection, Tat, surface CD91/LRP-1, TGF-β, and enhanced Leishmania phosphatidylserine-mediated phagocytosis.

View Article: PubMed Central - PubMed

Affiliation: Centre de Recherche en Infectiologie, Centre Hospitalier Universitaire de Québec-CHUL, Université Laval, Québec, Canada.

ABSTRACT
Over the past decade, the number of reported human immunodeficiency virus type-1 (HIV-1)/Leishmania co-infections has risen dramatically, particularly in regions where both diseases are endemic. Although it is known that HIV-1 infection leads to an increase in susceptibility to Leishmania infection and leishmaniasis relapse, little remains known on how HIV-1 contributes to Leishmania parasitaemia. Both pathogens infect human macrophages, and the intracellular growth of Leishmania is increased by HIV-1 in co-infected cultures. We now report that uninfected bystander cells, not macrophages productively infected with HIV-1, account for enhanced phagocytosis and higher multiplication of Leishmania parasites. This effect can be driven by HIV-1 Tat protein and transforming growth factor-beta (TGF-β). Furthermore, we show for the first time that HIV-1 infection increases surface expression of phosphatidylserine receptor CD91/LRP-1 on human macrophages, thereby leading to a Leishmania uptake by uninfected bystander cells in HIV-1-infected macrophage populations. The more important internalization of parasites is due to interactions between the scavenger receptor CD91/LRP-1 and phosphatidylserine residues exposed at the surface of Leishmania. We determined also that enhanced CD91/LRP-1 surface expression occurs rapidly following HIV-1 infection, and is triggered by the activation of extracellular TGF-β. Thus, these results establish an intricate link between HIV-1 infection, Tat, surface CD91/LRP-1, TGF-β, and enhanced Leishmania phosphatidylserine-mediated phagocytosis.

Show MeSH
Related in: MedlinePlus