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Studies on the ultrastructure, virus-like particles and infectivity of Leishmania hertigi
Abstract:
Five strains of Leishmania hertigi hertigi isolated in Panama and three strains of L. hertigi deanei isolated in Brazil were studied. Ultrastructural examination of promastigotes grown in culture showed virus-like particles (VLPs), 55--60 nm diameter, in the cytoplasm of all strains. The VLPs were normally either organized in paracrystalline clusters or associated with induced tubules. In some cases the VLPs were associated with dense vesicular bodies. Mitochondria with which the VLPs were associated had enlarged elongate or circular cristae. Elongate 'microbodies' containing rod-like structures were observed in promastigotes grown in culture. Poor infections of promastigotes developed in the midguts of 10% of laboratory-bred Lu. longipalpis following experimental feeding on cultures of L. h. hertigi. VLPs were seen in a promastigote in the midgut of a sandfly five days after feeding. Laboratory mammals proved poor hosts for L. hertigi. Cryptic infections in the visceral organs of immunosuppressed hamsters and immunodeficient 'nude' mice were detectable only by culture. Infections of DS cell and mouse peritoneal macrophage cultures showed amastigotes with a high ribosomal density and deep invaginations of the pellicular layer. VLPs were rarely seen in these amastigotes.
Insights
Virus-like particles (VLPs) were identified in Leishmania hertigi parasites from Panama and Brazil. These VLPs were observed in cultured promastigotes and within sandflies, but not in laboratory mammals.
Area of Science:
- Parasitology
- Microbiology
- Cell Biology
Background:
- Leishmania hertigi is a species of protozoan parasite.
- Understanding parasite ultrastructure and host interactions is crucial for disease control.
Purpose of the Study:
- To investigate the ultrastructural characteristics of Leishmania hertigi strains.
- To identify and characterize virus-like particles (VLPs) within these parasites.
- To assess the infectivity of L. hertigi in insect vectors and laboratory mammals.
Main Methods:
- Ultrastructural examination of cultured promastigotes and amastigotes.
- Experimental infections of Lu. longipalpis sandflies.
- Infections of laboratory mammals (hamsters, mice) and cell cultures (DS cells, macrophages).
Main Results:
- Virus-like particles (VLPs), 55-60 nm in diameter, were consistently observed in the cytoplasm of cultured L. hertigi promastigotes from both Panamanian and Brazilian isolates.
- VLPs were associated with paracrystalline clusters, induced tubules, and dense vesicular bodies, and altered mitochondrial cristae.
- Poor infections were established in Lu. longipalpis, with VLPs detected in a sandfly midgut promastigote five days post-feeding.
- Laboratory mammals served as poor hosts, with cryptic infections detectable only by culture in immunosuppressed or immunodeficient animals.
- Amastigotes in cell cultures exhibited high ribosomal density and deep pellicular invaginations, with rare detection of VLPs.
Conclusions:
- Leishmania hertigi harbors cytoplasmic virus-like particles (VLPs) in its promastigote stage.
- The parasite shows limited infectivity in Lu. longipalpis and is a poor host for laboratory mammals.
- Further research is needed to understand the role and nature of VLPs in L. hertigi biology and pathogenesis.