IN-VITRO MODEL FOR TOXOPLASMA-GONDII INVASION INTO NEUROEPITHELIAL CELLS

In order to study the interactions of Toxoplasma gondii and neuroepith elial cells morphologically and biochemically we established an easy i n vitro model, which simulates cellular contacts in congenital toxopla smosis. Monolayer cultures of neuroepithelial cells from 13-14-day-old mouse embryos were prepared containing the typical ventricular cell t ypes found in an embryonic brain, such as young neurons, macroglial an d microglial cells. Ultrastructural investigations on cultures incubat ed for 1, 5 and 30 min or 1, 6, 12, 24 and 48 h with T. gondii indicat ed that all three cell types had been invaded by the parasites, multip lying in parasite vacuoles by means of endodyogeny. Microglial cells h ad already been penetrated by trophozoites within one minute and showe d up to 3 or 5 parasite vacuoles per cell. Neurons and glial cells wer e invaded within 5 min and contained only one vacuole per host cell. A ll the parasite vacuoles were bounded by a membrane and bordered by th e rough endoplasmic reticulum and mitochondria of the host cell after a few minutes. The vacuoles also contained some membranic tubuli. Afte r 30 min some neuronal neurites were destroyed while the perikarya see med to be unchanged. After 6 h the cytoplasm of the microglia lost mor e and more ribosomes and organelles. Neurons and glial cells showed no alterations. After 12 h large areas of the vacuole membrane were fold ed up and lay curled up in the vacuoles. After 24 h incubation T gondi i had destroyed nearly all the microglial cells. The ultrastructure of neurons and glial cells now began to change in the same way as shown for microglial cells. The organelles and cellular membranes disintegra ted and after 48 h incubation nearly all the cells in the neuroepithel ial cell culture had fallen to pieces. For an identification of T. gon dii in vitro by light microscopy or for the characterization of the ce ll surface we tried to label the parasites with 11 different FITC-stai ned lectins. None of the tested lectins bound to the parasites. We con clude that our in vitro-model for invasion of T. gondii in neuroepithe lial cells opens an opportunity for studying the interaction of these cells or the pharmacological effects on this interaction under defined conditions.