Development of Schizont Stages of Toxoplasma gondii in Primary Cell Culture of Feline Enterocytes

Abstract

Intestinal epithelial cell cultures are a potentially applicable model for investigating enteropathogens such as the protozoan Toxoplasma gondii, the etiological agent of toxoplasmosis. Felids such as domestic cats are the only known definitive hosts where the parasite undergoes sexual reproduction, which occurs in the enterocytes. Primary feline intestinal epithelial cell (FIEC) cultures were obtained from the fetal small gut of felines, and the epithelial nature of these cells was confirmed by the revelation of cytokeratin and intestinal alkaline phosphatase content by fluorescence microscopy, besides alignment, microvilli, and adherent intercellular junctions by ultrastructural analysis. FIECs infected with T. gondii bradyzoite forms showed that the parasite:cell ratio was determinant for establishing the lytic cycle and cystogenesis and the induction of schizont-like forms. Type C and D schizonts were identified by light and electron microscopies, which showed morphological characteristics like those previously described based on the analysis of cat intestines experimentally infected with T. gondii. These data indicate that FIECs simulate the microenvironment of the felid intestine, allowing the development of schizogony and classic endopolygeny. This cellular framework opens new perspectives for the in vitro investigation of biological and molecular aspects involved in the T. gondii enteric cycle.

Massive invasion of organellar DNA drives nuclear genome evolution in Toxoplasma

“…Segregation of the nucleus and organelles to daughter parasites does not happen at the same time ( 64 ). Toxoplasma divides by endodyogeny (two daughter cells forming within the parent cell) in asexual replication ( 65 ) and utilizes schizogony (a process in which nuclear and some organellar division precedes cell division) in sexual reproduction ( 66 ). While it is known when the nuclear DNA replicates, the timing of organellar DNA replication is unknown.…”

Advances towards the complete in vitro life cycle of Toxoplasma gondii

“…This fact has puzzled T. gondii researchers for decades. Experiments with cell lines derived from the feline intestinal epithelium have provided evidence that infection with bradyzoites could lead to the development of type C and D schizonts 101 , 102 . A big step forward to explain this remarkable species specificity, despite T. gondii ’s otherwise promiscuous host range, was reported recently by Martorelli Di Genova et al .…”