Toxoplasma gondii profilin does not stimulate an innate immune response through bovine or human TLR5.

Toxoplasma gondii is responsible for one of the most prevalent infections in people. T. gondii profilin (TgPr) is a protein integral to parasite movement and cellular invasion. Murine TLRs has been described to bind TgPr. Furthermore, more recently, human TLR5 has been described to recognise recombinant TgPr, as well as bacterial flagellin. In addition to infections in humans, T. gondii infects farm animals, but little information is available about its innate recognition. We aimed to investigate whether, similarly to their human orthologue, bovine and porcine TLR5 could also be stimulated by TgPr by using a combination of reporter cell lines expressing full length TLR5 from each species as well as primary cells. Although human and bovine TLR5-transfected cells responded to flagellin, no response was detected upon stimulation with profilin. Furthermore, TgPr failed to elicit IL-6 secretion in human peripheral blood mononuclear cells and CD14+ monocytes. In contrast, exposure of RAW cells, known to express TLR11, to TgPr slightly increased the IL-6 response. Our data cast doubts on the possibility that profilin is a specific ligand for human TLR5 and bovine TLR5. This leaves the immunogenic properties of this potential target antigen (Ag) uncharacterised outside of the murine system.

Generation and characterisation of an equine macrophage cell line (e-CAS cells) derived from equine bone marrow cells.

Macrophages play a pivotal role in the pathophysiology of many diseases by mediating the host immune response to infections and intoxications. The species-specific activation of macrophages and the differential response in cytokine production impedes the extrapolation of results between species. Therefore, the aim of this study was to isolate and immortalise macrophages from equine bone marrow (BM) cells in order to study equine-specific signalling pathways. The isolated BM-derived macrophages (referred to as e-CAS cells) showed proliferation kinetics similar to that of standardised cell lines and were maintained in culture for >76 passages. To characterise the cells, a number of typical parameters of macrophages were tested. Morphological evaluation (May-Grünwald Giemsa staining) and non-specific esterase activity indicated the e-CAS cells to be macrophages. The presence of CD14 and their ability to phagocytose Escherichia coli bioparticles further confirmed their identity, as did their ability to produce cytokines, reactive oxygen and nitrogen intermediates in response to LPS. These data show that the established cell line (e-CAS) shows the characteristics of equine macrophages and may, therefore, prove to be a unique in vitro model for studying the cellular biology of equine inflammation.