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In vitro parasite-monocyte interactions in human leishmaniasis: possible role of fibronectin in parasite attachment
Abstract:
Leishmania spp. must attach to mononuclear phagocyte surfaces before entering this host cell. We investigated the potential role of fibronectin in facilitating parasite attachment. Human plasma fibronectin bound to axenically cultured promastigotes, and promastigotes and amastigotes preferentially bound to fibronectin-coated cover slips. Promastigotes grown in the absence of fibronectin were strikingly deficient in their ability to attach to human monocytes compared with promastigotes grown in the presence of fibronectin. Rabbit anti-human plasma fibronectin antiserum decreased promastigote and amastigote attachment to monocytes. Immunoglobulin G F(ab')2 and Fab fragments also reduced the ability of amastigotes to bind to monocytes. Antiserum pretreatment of amastigotes followed by washing resulted in reduced parasite binding, whereas antibody pretreatment of monocytes did not. Addition of exogenous fibronectin did not enhance parasite attachment to monocytes. These findings suggest that Leishmania spp. can bind fibronectin and may utilize this glycoprotein to facilitate attachment to the mononuclear phagocytes that they infect.
Insights
Leishmania parasites use fibronectin, a host glycoprotein, to attach to mononuclear phagocytes. This binding is crucial for Leishmania infection, as blocking fibronectin reduces parasite attachment to host cells.
Area of Science:
- Parasitology
- Cell Biology
- Immunology
Background:
- Leishmania spp. are protozoan parasites that infect mononuclear phagocytes.
- Parasite attachment to host cells is a critical step in the infection process.
Purpose of the Study:
- To investigate the role of fibronectin in the attachment of Leishmania parasites to mononuclear phagocytes.
Main Methods:
- Assessing fibronectin binding to Leishmania promastigotes and amastigotes.
- Evaluating parasite attachment to fibronectin-coated surfaces.
- Measuring the effect of anti-fibronectin antibodies and fragments on parasite-monocyte interaction.
- Comparing attachment of parasites grown with and without fibronectin.
Main Results:
- Leishmania parasites, in both promastigote and amastigote forms, bind to human plasma fibronectin.
- Parasites preferentially attach to fibronectin-coated surfaces.
- Promastigotes grown in the absence of fibronectin show reduced attachment to monocytes.
- Anti-fibronectin antibodies and their fragments significantly inhibit parasite attachment to monocytes, with antibody pretreatment of parasites being more effective than monocyte pretreatment.
Conclusions:
- Leishmania parasites utilize fibronectin to facilitate their attachment to mononuclear phagocytes.
- Fibronectin serves as a molecular bridge, enhancing parasite adherence to host cells.
- Targeting the fibronectin-parasite interaction could be a potential strategy for controlling Leishmania infections.