Attachment and invasion of Toxoplasma gondii and Neospora caninum to a cat and a dog fibroblast cell line and 2 epithelial cell lines (a cat kidney and Vero) were compared in vitro using fluorescence antibody methodology. In addition, trypsin treatment of tachyzoites was used to determine whether protein molecules were essential to the process of invasion. The results show that both T. gondii and N. caninum invaded all 4 cell lines, and that pre-treatment of T. gondii tachyzoites with trypsin caused an increase in the ability of the parasite to invade these host cells. Furthermore T. gondii, in comparison to N. caninum, invaded all 4 cell lines at greater levels. The results here support the conclusion that both T. gondii and N. caninum have the ability to invade a variety of cell types including both dog and cat cells, and questions the utility of Vero cells as an appropriate host cell for in vitro studies on the biology of these taxa.
