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Title: Characterization of Acanthamoeba macrophage activation
Author: Cano, Antonella
ISNI:       0000 0004 5370 858X
Awarding Body: University of Strathclyde
Current Institution: University of Strathclyde
Date of Award: 2015
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Acanthamoeba castellanii is a free-living amoeba ubiquitous in nature, with worldwide distribution. Although it is capable of living and proliferating without invading hosts, it can occasionally cause opportunistic as well as non opportunistic diseases in humans. Dissecting the immunology of Acanthamoeba infections has been always considered problematic due to the very low incidence despite the high exposure rates. The aim of this study was to investigate the effects of Acanthamoeba on the activation of resting macrophages. Towards this purpose bone marrow derived macrophages were co-cultured with either a laboratory strain, named Neff, or a clinical isolate of A. castellanii. Acanthamoeba was found to induce a pro-inflammatory macrophage phenotype following exposure to Neff strain, characterized by significant production of TNF-α, IL-12 and IL-6 from macrophages. In comparison the clinical isolate induced IL-12 and IL-6 to a significantly lesser degree than the Neff strain (p < 0.00 05) and did not induce TNF-α. The utilization of macrophages derived from MyD88, TRIF, TLR2, TLR4, TLR2/4, and PAR2 deficient mice along with a PAR1 specific antagonist indicated that Acanthamoeba-induced pro-inflammatory cytokine production was through MyD88-dependent (p < 0.0005), TLR4-induced events (p < 0.0005), with a further contribution from PAR1 (p < 0.05). Acanthamoeba trophozoites were also found to induce arginase activity in macrophages (p < 0.0005). Conversely, nitric oxide (NO) was not significantly detected in macrophages co-incubated with Acanthamoeba. By inducing arginase activity in macrophages, Acanthamoeba trophozoites were also found to be capable of inducing a tissue-repair, wound healing phenotype. Macrophage/Acanthamoeba co-incubation, analysed using a metabolomics approach, showed a peculiar metabolic snap-shot where both amoeba and macrophage metabolites might play a role in modulating the development and outcome of infection. The information obtained from this experimental study has provided new and interesting insights about the immunological aspects of Acanthamoeba infections, which may be helpful for future practical applications in pharmaceutical, immunological and diagnostic fields.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral