Protists are a diverse collection of eukaryotic organisms that account for a significant global infection burden. Often, the immune responses mounted against these parasites cause excessive inflammation and therefore pathology in the host. Elucidating the mechanisms of both protective and harmful immune responses is complex, and often relies of the use of animal models. In any immune response, leucocyte trafficking to the site of infection, or inflammation, is paramount, and this involves the production of chemokines, small chemotactic cytokines of approximately 8-10 kDa in size, which bind to specific chemokine receptors to induce leucocyte movement. Herein, the scientific literature investigating the role of chemokines in the propagation of immune responses against key protist infections will be reviewed, focussing on Plasmodium species, Toxoplasma gondii, Leishmania species and Cryptosporidium species. Interestingly, many studies find that chemokines can in fact, promote parasite survival in the host, by drawing in leucocytes for spread and further replication. Recent developments in drug targeting against chemokine receptors highlights the need for further understanding of the role played by these proteins and their receptors in many different diseases.

Colour print requested for figure 2 and figure 3* Vibrio species are predominantly intracellular within cultures of Neoparamoeba perurans, causative agent of Amoebic Gill Disease (AGD)

Amoebic Gill Disease (AGD) is a major problem in the aquaculture industry, as it is responsible for substantial losses of farmed Atlantic salmon in various worldwide locations. The disease is caused by the usually free-living Paramoeba perurans compromising the gills through the resulting development of hyperplastic lesions and lamellar fusion. These structural changes result in a reduction in the functional surface area of the gill tissues. Recent research has focused on identifying bacteria present within a culture of P. perurans, through performing isolation and identification of bacteria present in the cultures using 16S sequencing. Further NGS sequencing was performed from various culture conditions to provide insight into the changes of the bacterial microbiome during amoeba culture. As attempts to isolate the amoeba from the bacterial contamination has been unsuccessful, consideration into a possible symbiotic relationship between the amoeba and bacteria was considered. A filtering method was used to attempt to identify the genera of bacteria present within the amoeba. The isolation and 16S sequencing identified the presence of various marine bacteria, including those of the Pseudoalteromonas, Halomonas, Cellulophaga and Mesonia genera. The NGS sequencing identified a substantial proportion of sequences to match the Vibrio genus and suggests an association between this genus and the amoeba. If symbiotic relationships between specific bacteria and amoeba can be confirmed, the bacteria could potentially be used as an indicator organism for the risk of AGD outbreak. It may also provide an indirect target for the control and treatment of AGD.

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