The in vitro development of Neospora caninum bradyzoites

Neospora caninum is a recently identified apicomplexan protozoan parasite t hat is closely related to Toxoplasma gondii. Neospora caninum is of signifi cant economic importance as it causes neurological disease and abortion in numerous animals. Antibodies to BAG1/hsp30 (also known as BAGS), a T. gondi i bradyzoite-specific protein, have been demonstrated to react with N. cani num tissue cysts in vivo. Bradyzoite differentiation of N. caninum in vitro was investigated using culture conditions previously utilised for T, gondi i in vitro bradyzoite development. Utilising the NC-Liverpool isolate of N, canimum, cyst-like structures developed within 3-4 days of culture of this parasite in human fibroblasts. In addition, an antigen reacting with mAb 7 4.1.8 (anti-BAG1) and rabbit anti-recombinant BAG1 was demonstrable by immu nofluorescence, fluorescence-activated cell sorter, and immunoblot analyses , Expression of this antigen was increased by stress conditions, similar to that which has been described for T. gondii bradyzoite induction. Cyst-wal l formation in vitro, as assayed by lectin binding, did not occur as readil y for N. caninum as it does for T. gondii. (C) 1999 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.