Acanthamoeba castellanii stimulates the production of IL-6, IL-12 and TNF-alpha by murine macrophages

Acanthamoeba castellanii is an opportunistic, facultative parasitic protozoa known to be the agent of a serious painful potentially blinding keratitis and fatal encephalitis in humans. Acanthamoeba is ubiquitous and approximately 85% of humans are seropositive implying that protective immunity is the most common outcome of infection. However, how this is achieved is not currently known. Herein, we establish the kinetics of TNFα, IL-12 and IL-6 production by murine macrophages, following challenge with trophozoites of the Acanthamoeba castellani (Neff Strain). The addition of protease inhibitors to cultures increased the levels of cytokines detected. Further studies demonstrated that cytokine levels were considerably lower in macrophage cultures exposed to a clinical isolate of A. castellanii (T4 genotype), from a bilateral keratitis than with the Neff strain. Studies are underway to determine: (i) the molecular mechanism responsible for Acanthamoeba-induced cytokine production and (ii) if differences in protease production and therefore proteolytic cleavage of cytokines is responsible for these observed disparity of cytokine levels in macrophage cultures with the 2 Acanthamoeba strains. These results demonstrate that macrophages release pro-inflammatory cytokines, which can be attenuated by Acanthamoeba-derived proteases. The balance of production of these cytokines with their digestion by Acanthamoeba-producedproteasescould determine efficacy of the immune system to resolve infection. Future studies will focus on the ability of Acanthamoeba castellanii to elude the immune response and the identification of the receptors involved in the recognition of Acanthamoebacastellanii.