Calomys callosus (Rodentia : Cricetidae) trophoblast cells as host cells to Toxoplasma gondii in early pregnancy

The potential of the RH strain of Toxoplasma gondii to invade trophoblast. cells of the cricetid rodent Calomys callosus in a congenital infection in the initial third of pregnancy was investigated in this study using morphol ogical and immunocytochemical approaches. The animals were intraperitoneall y inoculated on the Ist day of pregnancy and the infection was observed on day 7. Various numbers of parasites could be observed inside the parasitoph orous vacuoles in trophoblastic cells under light and electron microscopy. The trophoblast cells showed characteristics of healthy cells, and no alter ation other than parasite vacuoles in their cytoplasm could be detected. Po lyclonal or monoclonal anti-T. gondii antibodies (respectively, anti-T. gon dii components and the major surface parasite antigen p30) labeled both the parasite surface and parasitophorous vacuole membranes, regardless of the number of parasites inside the compartment. In addition, p30-containing tra ils were detected in the extracellular matrix surrounding trophoblastic cel ls similar to those found with other parasites during locomotion and the in vasion process. Our results show the ability of T. gondii to infect trophob last cells during the early blastocyst-endometrial relationship and open ne w possibilities for more accurate study of the invasion process of this par asite and the role of the trophoblast as an embryo defense barrier.