Eimeria bovis infection enhances adhesion of peripheral blood mononuclear cells to and their transmigration through an infected bovine endothelial cell monolayer in vitro

Abstract

The first schizogony of Eimeria bovis takes place in lymphatic endothelial cells of the ileum, resulting in the formation of macroschizonts within 2-3 weeks. In this study, we analyse early cellular immune responses to infected host cells on the basis of peripheral blood mononuclear cell (PBMC) adhesion on and transmigration through infected bovine umbilical vein endothelial cell (BUVEC) monolayers. Adhesion of PBMC was upregulated by an E. bovis infection. Most marked effects were observed 1 day p.i.; thereafter, PBMC adhesion declined reaching control levels from day 8 p.i. onward. CD8(+) T cells adhered more frequently to infected BUVEC (42%) than CD4(+) T cells (25%). About one third of attached PBMC were represented by gammadelta-TCR(+) T cells. Adhesion of T cells was not restricted to parasitised host cells, but occurred almost equally on non-infected BUVEC within the same monolayer. Furthermore, we found moderately enhanced levels of PBMC transmigration through infected BUVEC monolayers, in particular on day 2 p.i. The data presented here suggest that E. bovis infection of BUVEC induces endothelial cell-derived proinflammatory reactions, which appear suitable for the initiation of both adaptive and innate immune responses.

Microarray-based transcriptional profiling ofEimeria bovis-infected bovine endothelial host cells

“…Previous work has shown that interactions of E. bovis and endothelial cells result in inflammatory processes associated with the adhesion of PMN [15] and PBMC [31] to infected cell layers and enhanced transcription of genes encoding for immune-modulatory molecules [30]. The enhanced host cell immune responses described here support these reports, most notably on day 8 p.i.…”

“…Interestingly, all up-regulated chemokines belonged to the CXC-family (CXCL1, CXCL3, CXCL6, CXCL8), molecules predominantly acting on PMN and/or lymphocytes [19, 35], both of which are stimulated in E. bovis infections [5, 32]. Up-regulation of the adhesion molecules VCAM1, ICAM1 and SELP may directly contribute to the above mentioned adhesion of leukocytes to infected cell layers [15, 31]. …”

“…Comparative studies investigating the influence of different apicomplexa on the transcription of genes encoding for immunoregulatory molecules showed a relatively weak impact of E. bovis when compared to Toxoplasma gondii and Neospora caninum infections [30]. Interactions of E. bovis -infected endothelium with leukocytes were shown at the level of PBMC and PMN adhesion and seem to rely on infection-induced up-regulation of distinct adhesion molecules [15, 31]. …”

Eimeria bovis meront I-carrying host cells express parasite-specific antigens on their surface membrane

“…Whilst a variety of studies on adaptive immune responses against E. bovis infections (Speer et al 1985;Hughes et al 1988Hughes et al , 1989Fiege et al 1992;Hermosilla et al 1999;Taubert et al 2007;Taubert et al 2008) emphasize the role of parasite antigens in the induction of immunity, no data are available on E. bovis antigens expressed on infected host cells. Since adaptive cellular immune responses occur in vivo already during the prepatency of E. bovis infections (Hughes et al 1988(Hughes et al , 1989Fiege et al 1992;Hermosilla et al 1999;Taubert et al 2007Taubert et al , 2008 and since sporozoites rapidly invade endothelial host cells and then are situated intracellular, developing immune reactions should also be directed against infected host cells.…”

“…Since adaptive cellular immune responses occur in vivo already during the prepatency of E. bovis infections (Hughes et al 1988(Hughes et al , 1989Fiege et al 1992;Hermosilla et al 1999;Taubert et al 2007Taubert et al , 2008 and since sporozoites rapidly invade endothelial host cells and then are situated intracellular, developing immune reactions should also be directed against infected host cells. Given that endothelial cells generally have the capacity of antigenpresentation (Wagner et al 1984;Bosse et al 1993;Knolle 2006;Behling-Kelly and Czuprynski 2007), it appears likely that T cells may act against early stages, such as intracellular sporozoites or meronts I, rather than meronts II and gamonts.…”