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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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Related in: MedlinePlus

MDMs productively infected with HIV-1 secrete a factor that is necessary for inducing enhanced Leishmania parasite intake.MDMs were treated for 24 hours with cell-free supernatants from 6-day old virus-infected macrophages or uninfected MDM supernatants supplemented with EFZ. Mock-treated cells or MDMs treated for 24 hours with IL-10 were used as controls. Next, MDMs were pulsed for 1 hour either with complement-opsonized Alexa488-labeled zymosan particles or GFP-expressing Leishmania parasites. Thereafter, excess zymosan particles/Leishmania parasites were washed out and MDMs cultured for another 3 hours. After fixing and mounting the cells, the numbers of internalized zymosan particles or Leishmania parasites were then determined by fluorescence microscopy. Results are from a donor representative of three (mean number of targets ± SEM).
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pone-0032761-g003: MDMs productively infected with HIV-1 secrete a factor that is necessary for inducing enhanced Leishmania parasite intake.MDMs were treated for 24 hours with cell-free supernatants from 6-day old virus-infected macrophages or uninfected MDM supernatants supplemented with EFZ. Mock-treated cells or MDMs treated for 24 hours with IL-10 were used as controls. Next, MDMs were pulsed for 1 hour either with complement-opsonized Alexa488-labeled zymosan particles or GFP-expressing Leishmania parasites. Thereafter, excess zymosan particles/Leishmania parasites were washed out and MDMs cultured for another 3 hours. After fixing and mounting the cells, the numbers of internalized zymosan particles or Leishmania parasites were then determined by fluorescence microscopy. Results are from a donor representative of three (mean number of targets ± SEM).

Mentions: In order to identify by what mechanism Leishmania phagocytosis was specifically enhanced in the uninfected bystander cell subpopulation compared to HIV-1-infected MDMs, we investigated if this effect was dependent on a soluble factor released by productively HIV-1-infected MDMs. We therefore treated a fresh culture of MDMs (i.e. uninfected with HIV-1) with 6-day old cell-free supernatants from virus-infected or uninfected MDMs to which was added Efavirenz (EFZ), a specific inhibitor of the virus-encoded reverse transcriptase enzyme. This enabled us to abrogate viral infection when such supernatants were added to new cultures of MDMs, as detected by ELISA against the major core p24 protein for up to 7 days (data not shown). As depicted in Figure 3, a 24-hour exposure of uninfected MDMs to supernatants from HIV-1-infected macrophages containing EFZ was sufficient to enhance Leishmania phagocytosis to more than 50% of those found in untreated control MDMs, but to similar levels found in cells treated with IL-10 (P = 0.67), a cytokine known to favor Leishmania multiplication and survival [18]. Additionally, a significant drop in the ability of the supernatant-treated cells to internalize zymosan particles was also observed as compared to untreated cells (P = 0.029). These results suggested that a soluble factor present in cell-free supernatants from HIV-1-infected MDMs was responsible for the higher parasite uptake in uninfected bystander cells.


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)

MDMs productively infected with HIV-1 secrete a factor that is necessary for inducing enhanced Leishmania parasite intake.MDMs were treated for 24 hours with cell-free supernatants from 6-day old virus-infected macrophages or uninfected MDM supernatants supplemented with EFZ. Mock-treated cells or MDMs treated for 24 hours with IL-10 were used as controls. Next, MDMs were pulsed for 1 hour either with complement-opsonized Alexa488-labeled zymosan particles or GFP-expressing Leishmania parasites. Thereafter, excess zymosan particles/Leishmania parasites were washed out and MDMs cultured for another 3 hours. After fixing and mounting the cells, the numbers of internalized zymosan particles or Leishmania parasites were then determined by fluorescence microscopy. Results are from a donor representative of three (mean number of targets ± SEM).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3295765&req=5

pone-0032761-g003: MDMs productively infected with HIV-1 secrete a factor that is necessary for inducing enhanced Leishmania parasite intake.MDMs were treated for 24 hours with cell-free supernatants from 6-day old virus-infected macrophages or uninfected MDM supernatants supplemented with EFZ. Mock-treated cells or MDMs treated for 24 hours with IL-10 were used as controls. Next, MDMs were pulsed for 1 hour either with complement-opsonized Alexa488-labeled zymosan particles or GFP-expressing Leishmania parasites. Thereafter, excess zymosan particles/Leishmania parasites were washed out and MDMs cultured for another 3 hours. After fixing and mounting the cells, the numbers of internalized zymosan particles or Leishmania parasites were then determined by fluorescence microscopy. Results are from a donor representative of three (mean number of targets ± SEM).
Mentions: In order to identify by what mechanism Leishmania phagocytosis was specifically enhanced in the uninfected bystander cell subpopulation compared to HIV-1-infected MDMs, we investigated if this effect was dependent on a soluble factor released by productively HIV-1-infected MDMs. We therefore treated a fresh culture of MDMs (i.e. uninfected with HIV-1) with 6-day old cell-free supernatants from virus-infected or uninfected MDMs to which was added Efavirenz (EFZ), a specific inhibitor of the virus-encoded reverse transcriptase enzyme. This enabled us to abrogate viral infection when such supernatants were added to new cultures of MDMs, as detected by ELISA against the major core p24 protein for up to 7 days (data not shown). As depicted in Figure 3, a 24-hour exposure of uninfected MDMs to supernatants from HIV-1-infected macrophages containing EFZ was sufficient to enhance Leishmania phagocytosis to more than 50% of those found in untreated control MDMs, but to similar levels found in cells treated with IL-10 (P = 0.67), a cytokine known to favor Leishmania multiplication and survival [18]. Additionally, a significant drop in the ability of the supernatant-treated cells to internalize zymosan particles was also observed as compared to untreated cells (P = 0.029). These results suggested that a soluble factor present in cell-free supernatants from HIV-1-infected MDMs was responsible for the higher parasite uptake in uninfected bystander cells.

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