Plasmodium ookinetes are an invasive stage of the malaria life cycle that occurs in the mosquito vector. Ookinetes traverse the mosquito midgut epithelium where they come to rest under the basal lamina and transform into oocysts. The close association of the developing parasites with the basal lamina has led to proposals that the basal lamina may provide signals to induce transformation of ookinetes into oocysts. This hypothesis was tested using an in vitro culture system for the murine malaria parasite, Plasmodium berghei, and transformationw as found to occur independentlyo f the presenceo f laminin. The putative role of laminin in invasion was also investigated in vitro; however, the insect cell lines used in co-cultures, that had been previously described to be invaded by ookinetes, were found instead to phagocytose ookinetes. Thus, phagocytosis of ookinetes by four insect cell lines is reported. Finally, laminin has been shown to bind to Plasmodium ookinete proteins and oocysts have been reported to incorporate this molecule into the oocyst capsule. It has been hypothesised that Plasmodium incorporation of laminin, and other basal lamina components, into the oocyst capsule would enable the parasite to mask itself from the innate immune system of the vector. Anopheles stephensi mosquitoes were infected with P. berghei and incorporation of laminin into the oocyst capsule was investigated using immunogold labeling and electron microscopy techniques. Laminin was observed to coat oocysts and was found to be incorporated in the oocyst capsule. The close proximity of the vector stages of malaria parasites to the insect basal lamina have led to several suggestions that important interactions may occur between the parasite and the basal lamina that are essential for parasite development. The results obtained demonstrate that laminin is not important in the early stages of sporogonic development.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:573763 |
| Date | January 2007 |
| Creators | Nacer, Adela |
| Publisher | Keele University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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