Investigating the phenotypic and functional similarities between the protozoan Acanthamoeba and human macrophages

Acanthamoeba is a free-living amoeba that can be found in virtually all soil and water habitats throughout the world. Acanthamoeba lives in all of our homes and can be isolated from kitchen/bathroom taps, showerheads, vacuum cleaner dust and garden soil. Acanthamoeba is a dimorphic organism which exists as a feeding and dividing trophozoite which when it encounters unfavourable conditions forms a highly resistant and dormant cyst stage. What is particularly worrying about this infection is that there is currently no licenced treatment.

The organism usually feeds on bacteria but is an opportunistic pathogen of humans causing a fatal encephalitis in immunocompromised patients as well as a blinding infection of the eye called Acanthamoeba keratitis (AK). In addition to being a direct pathogen of humans Acanthamoeba also acts an environmental host for many bacterial pathogens including Mycobacterium spp, Vibrio cholerae and Legionella pneumophilla. Once internalised the bacteria are protected from predation and persist in the environment.

Acanthamoeba are essentially free living macrophages which seek out bacteria in the environment and phagocytose them using processes conserved with those seen in human macrophages. This, along with the observation that Acanthamoeba are susceptible to the same intracellular bacteria as mammalian macrophages, suggests that they share a distant evolutionary origin.

This proposal will focus on investigating the phenotypic and functional similarities between Acanthamoeba and macrophages isolated from human peripheral blood. The intention of the project is to gain greater understanding of how Acanthamoeba may interact with the human immune system during infection and to potentially identify novel subpopulations and therapeutic targets.