Pathogenesis of haematogenous spread in Acanthamoeba castellanii infections

Acanthamoeba castellanii is an amoeboid protozoan which causes opportunistic infections, including granulomatous encephalitis in immune-compromised patients. Haematogenous dissemination follows initial infection and the pathogen exhibits an ability to cross the blood-brain barrier (BBB). In the bloodstream and at the site of BBB penetration in the brain microvasculature A. castellanii is exposed to host humoral immunity. Here, we have provided insights into A. castellanii pathogenesis and the identity of amoeba antigens participating in immune control. We have investigated the role circulating immunoglobulin plays in preventing penetration of the BBB, and whether trophozoites can alter the efficacy of the immune response. Furthermore we have extended previously published data, demonstrating that amoeba proteases can degrade all antibody classes including physiologically-derived antibody. Nonspecific binding of polyclonal antibody was also observed, and attributed to Fc-binding activity by trophozoites. Additionally, we have examined the binding dynamics of A. castellanii under physiological conditions. BBB disruption was shown to be not directly linked to binding, instead it is reliant on secreted proteases. This study provides insights into mechanisms by which A. castellanii evades host immunity and crosses the BBB. This has the potential to enhance therapeutic strategies aimed at restoring essential disease prevention processes. In addition we have identified a number of amoeba antigens that are targets for the immune system and which may therefore be exploited through vaccination or immunotherapy

Pathogenesis of haematogenous spread in Acanthamoeba castellanii infections

Acanthamoeba castellanii is an amoeboid protozoan which causes opportunistic infections, including granulomatous encephalitis in immune-compromised patients. Haematogenous dissemination follows initial infection and the pathogen exhibits an ability to cross the blood-brain barrier (BBB). In the bloodstream and at the site of BBB penetration in the brain microvasculature A. castellanii is exposed to host humoral immunity. Here, we have provided insights into A. castellanii pathogenesis and the identity of amoeba antigens participating in immune control. We have investigated the role circulating immunoglobulin plays in preventing penetration of the BBB, and whether trophozoites can alter the efficacy of the immune response. Furthermore we have extended previously published data, demonstrating that amoeba proteases can degrade all antibody classes including physiologically-derived antibody. Nonspecific binding of polyclonal antibody was also observed, and attributed to Fc-binding activity by trophozoites. Additionally, we have examined the binding dynamics of A. castellanii under physiological conditions. BBB disruption was shown to be not directly linked to binding, instead it is reliant on secreted proteases. This study provides insights into mechanisms by which A. castellanii evades host immunity and crosses the BBB. This has the potential to enhance therapeutic strategies aimed at restoring essential disease prevention processes. In addition we have identified a number of amoeba antigens that are targets for the immune system and which may therefore be exploited through vaccination or immunotherapy

Plasmodium falciparum GBP2 Is a Telomere-Associated Protein That Binds to G-Quadruplex DNA and RNA

In the early-diverging protozoan parasite Plasmodium, few telomere-binding proteins have been identified and several are unique. Plasmodium telomeres, like those of most eukaryotes, contain guanine-rich repeats that can form G-quadruplex structures. In model systems, quadruplex-binding drugs can disrupt telomere maintenance and some quadruplex-binding drugs are potent anti-plasmodial agents. Therefore, telomere-interacting and quadruplex-interacting proteins may offer new targets for anti-malarial therapy. Here, we report that P. falciparum GBP2 is such a protein. It was identified via ‘Proteomics of Isolated Chromatin fragments’, applied here for the first time in Plasmodium. In vitro, PfGBP2 binds specifically to G-rich telomere repeats in quadruplex form and it can also bind to G-rich RNA. In vivo, PfGBP2 partially colocalises with the known telomeric protein HP1 but is also found in the cytoplasm, probably due to its affinity for RNA. Consistently, its interactome includes numerous RNA-associated proteins. PfGBP2 is evidently a multifunctional DNA/RNA-binding factor in Plasmodium.</jats:p

Next generation of non-mammalian blood-brain barrier models to study parasitic infections of the central nervous system

Transmigration of neuropathogens across the blood-brain barrier is a key step in the development of central nervous system infections, making it a prime target for drug development. The ability of neuropathogens to traverse the blood-brain barrier continues to inspire researchers to understand the specific strategies and molecular mechanisms that allow them to enter the brain. The availability of models of the blood-brain barrier that closely mimic the situation in vivo offers unprecedented opportunities for the development of novel therapeutics

Next generation of non-mammalian blood-brain barrier models to study parasitic infections of the central nervous system

Transmigration of neuropathogens across the blood-brain barrier is a key step in the development of central nervous system infections, making it a prime target for drug development. The ability of neuropathogens to traverse the blood-brain barrier continues to inspire researchers to understand the specific strategies and molecular mechanisms that allow them to enter the brain. The availability of models of the blood-brain barrier that closely mimic the situation in vivo offers unprecedented opportunities for the development of novel therapeutics

Next generation of non-mammalian blood-brain barrier models to study parasitic infections of the central nervous system.

Transmigration of neuropathogens across the blood-brain barrier is a key step in the development of central nervous system infections, making it a prime target for drug development. The ability of neuropathogens to traverse the blood-brain barrier continues to inspire researchers to understand the specific strategies and molecular mechanisms that allow them to enter the brain. The availability of models of the blood-brain barrier that closely mimic the situation in vivo offers unprecedented opportunities for the development of novel therapeutics

Acanthamoeba interactions with the blood-brain barrier under dynamic fluid flow.

Acanthamoeba granulomatous encephalitis (AGE), caused by Acanthamoeba castellanii, is a fatal infection of immunocompromised individuals. The pathogenesis of blood-brain barrier (BBB) breach remains unknown. Using a novel in vitro BBB infection model under flow conditions, demonstrates that increases in flow rates lead to decreased binding of A. castellanii to host cells. This is a distinct departure from previous findings under static conditions. However, similarly to static conditions binding of A. castellanii to host cells is host mannose dependent. Disruption of the host cell monolayer was independent of amoeba binding, but dependent on secreted serine proteases. For the first time we report the binding dynamics of A. castellanii under physiological conditions, showing that BBB disruption is not directly linked to binding, instead it is reliant on secreted proteases. Our results offer a platform on which therapies designed at modulating physiological parameters can improve the outcome of infection with A. castellanii