Medical Biology - Theses

Permanent URI for this collection

http://hdl.handle.net/11343/239

Filters

2023 1
Reset filters

Settings
Statistics
Citations
Subject: Malaria × Type: PhD thesis × Author: Clucas, Danielle Bridget ×

Search Results

Now showing 1 - 1 of 1
  • Item
    Thumbnail Image
    Studies of Plasmodium-Iron Interactions
    Clucas, Danielle Bridget ( 2023-09)
    Background Iron deficiency anaemia and malaria co-exist across sub-Saharan Africa where they disproportionately affect young children and pregnant women. Iron supplementation is recommended to treat anaemia, but there are concerns regarding its safety and the potential protection afforded by iron deficiency. An interaction between host iron status and malaria risk has been hypothesised for decades, but confounding factors mean that conclusions are difficult to draw from field studies alone. In this thesis the complex interaction between Plasmodium and iron is investigated using clinical, pre-clinical and in vitro studies. Methods The effect of host iron deficiency on the risk of Plasmodium falciparum parasitaemia by PCR was assessed in a cohort of 711 anaemic Malawian pregnant women, and the risk of intravenous iron supplementation on subsequent risk of parasitaemia explored. These findings were dissected using Plasmodium berghei infection in C57Bl/6 mouse models of iron deficiency (Tmprss6 knockout (Tmprss6-KO)) and iron overload (inducible hepcidin knockout (iHamp-KO)). Tmprss6 knockdown (Tmprss6-KD) was used to assess the phenotype in Tmprss6-KO mice and to explore Tmprss6 as a druggable target; achieved through treatment of wild-type C57Bl/6 mice with siTMP, a GalNAc conjugate targeting Tmprss6. The effect of iron restriction on the parasite was investigated through iron chelation of in vitro P. falciparum cultures, followed by transcriptomic and proteomic analysis. A role of post-transcriptional regulation in the response to iron chelation was further explored. In the setting of known post transcriptional regulation of cellular iron in other organisms via the iron responsive element (IRE)/Iron regulatory protein (IRP) system, and with an IRP-like protein described in P. falciparum, the role of PfIRP was explored through the generation and characterisation of PfIRP-KO parasites. Results Among anaemic Malawian pregnant women iron deficiency was associated with a 53% reduced risk of P. falciparum parasitaemia (Adjusted risk ratio 0.47, 95% confidence interval (0.34, 0.60), p<0.0001), with this finding robust to varied definitions of iron deficiency. Intravenous iron did not increase the subsequent risk of P. falciparum parasitaemia. These findings were supported by the mouse models. Tmprss6-KO mice had improved survival when infected with P. berghei. Conversely, iHamp-KO mice exhibited decreased liver stage infection but an unaltered course in the blood stage of infection. Tmprss6-KD did not replicate the KO phenotype; the disease course was not changed in siTMP treated mice. In vitro, iron chelation inhibited parasite growth and induced substantial changes in the transcriptome and proteome of P. falciparum. Differential expression of genes and proteins involved in key processes in the parasite’s lifecycle, and with plausible links to iron were identified, as was a possible role for post-transcriptional regulation. Investigating this showed PfIRP-KO parasites were more susceptible to iron chelation. Transcriptomic and proteomic analysis identified proteins that might be regulated in an IRE/IRP-like manner. Conclusions This work adds to the current understanding of the complex interaction between Plasmodium and iron. Taken together, these data support iron deficiency being protective against P. falciparum infection. In vitro studies highlighted genes of potential further interest in P. falciparum iron homeostasis and support an iron related role for PfIRP.