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Passive transfer of Leishmania lipopolysaccharide confers parasite survival in macrophages
Abstract:
Infection of macrophages by the intracellular protozoan parasite Leishmania involves specific attachment to the host membrane, followed by phagocytosis and intracellular survival and growth. Two parasite molecules have been implicated in the attachment event: Leishmania lipopolysaccharide (L-LPS) and a glycoprotein (gp63). This study was designed to clarify the role of L-LPS in infection and the stage in the process of infection at which it operates. We have recently identified a Leishmania major strain (LRC-L119) which lacks the L-LPS molecule and is not infective for hamsters or mice. This parasite was isolated from a gerbil in Kenya and was identified phenotypically as L. major by isoenzyme and fatty acid analysis. In this study we have confirmed at the genotype level that LRC-L119 is L. major by analyzing and comparing the organization of cloned DNA sequences in the genome of different strains of L. major. Here we show that LRC-L119 promastigotes are phagocytosed rapidly by macrophages in vitro, but in contrast to virulent strains of L. major, they are then killed over a period of 18 hr. In addition, we show that transfer of purified L-LPS from a virulent clone of L. major (V121) into LRC-L119 promastigotes confers on them the ability to survive in macrophages in vitro.
Insights
Leishmania lipopolysaccharide (L-LPS) is crucial for Leishmania parasite survival within macrophages. L-LPS-deficient parasites are phagocytosed but killed, while L-LPS addition restores infectivity.
Area of Science:
- Immunology
- Parasitology
- Molecular Biology
Background:
- Leishmania parasites infect macrophages, a process involving attachment, phagocytosis, and intracellular survival.
- Leishmania lipopolysaccharide (L-LPS) and gp63 are implicated in parasite attachment to host cells.
- A Leishmania major strain (LRC-L119) lacking L-LPS is non-infective in vivo.
Purpose of the Study:
- To elucidate the role of L-LPS in Leishmania infection.
- To determine the stage of infection influenced by L-LPS.
Main Methods:
- Genotypic confirmation of Leishmania major strain LRC-L119 using DNA sequence analysis.
- In vitro phagocytosis assays of LRC-L119 promastigotes by macrophages.
- Assessment of parasite survival post-phagocytosis.
- Experimental transfer of purified L-LPS into LRC-L119 promastigotes.
Main Results:
- LRC-L119 promastigotes, lacking L-LPS, were rapidly phagocytosed by macrophages but subsequently killed within 18 hours.
- Virulent Leishmania major strains exhibit intracellular survival.
- Addition of purified L-LPS to LRC-L119 promastigotes restored their ability to survive within macrophages in vitro.
Conclusions:
- Leishmania lipopolysaccharide (L-LPS) is essential for Leishmania parasite survival within macrophages.
- L-LPS plays a critical role in enabling intracellular growth and infectivity of Leishmania.
- Targeting L-LPS could be a strategy to combat Leishmania infections.