First-generation merozoites of caprineare capable to invade and egress primary host endothelial cells.

Abstract

The caprinespecies belongs to the phylogenetic clade of pathogenic ruminantreplicating within the endothelial cells of central lymph capillaries of the ileum villi. Investigations on-host endothelial cell interactions, including cell invasion, egress, apoptosis, senescence, cell cycle, cytoskeleton, cell metabolism and endothelium-derived innate immune reactions are possible to achieve through permissiveculture systems. Therefore, we here established a suitable(strain GC) culture system using primary bovine umbilical vein endothelial cells (BUVEC) for the development of first-generation macromeronts. After 18-22 days post infection (p.i.), the intracellular sporozoites matured into fully developed-macromeronts, releasing viable merozoites I. Interestingly, two different types of-merozoites I were observed, i.e., thinner and thicker merozoites I. The thinner ones were more active, presented typical gliding motility, and were found intracellularly shortly after their release, while the thicker ones were less active and invasive to BUVEC. Thinnermerozoites I actively invaded and egressed host cells by breaching the plasma membrane without host cell lysis, a phenomenon exclusively reported so far for apicomplexan sporozoites ofand. Additionally, intracellularmerozoites I were monitored over time (up to 30 days), thereby revealing no further development into meront II stages. Further research is needed to assess whether primary endothelial cells of caprine origin could support the complete life cycle of. This novelsystem will contribute not only for further studies onderived invasion- and egress strategies, endothelial cell-derived innate immune reactions, but also for merozoites I- and antigen production requested for vaccination strategies as already reported for other ruminantspecies.