Infection of mouse neural progenitor cells by Toxoplasma gondii affects in vitro proliferation, differentiation and migration

Congenital toxoplasmosis constitutes a major cause of pre- and post-natal complications. Fetal infection with Toxoplasma gondii influences development and can lead to microcephaly, encephalitis, and neurological abnormalities. Few studies have attempted to explain the impact of T. gondii infection on the physiology of mature nerve cells, and no systematic study concerning the effect of infection of neural progenitor cells by T. gondii in the biology of these progenitors is available. We infected cortical intermediate progenitor cell cultivated as neurospheres obtained from E16.5 Swiss Webster mice with T. gondii (Me49 strain) tachyzoites to mimic the developing mouse cerebral cortex in vitro. Infection decreased cell proliferation as detected by Ki67 staining at 48 and 72 hours post infection (hpi) in floating neurospheres, resulting in reduced cellularity at 96 hpi. Neurogenic and gliogenic potential, assessed in plated neurospheres, was shown to be impaired in infected cultures, as indicated by neurofilament heavy chain (NF-200) and GFAP staining, respectively. To further investigate the impact of infection on neuronal differentiation, Neuro2a neuroblasts were infected and after 24 hpi, neurogenic differentiation was induced with serum withdrawal. We confirmed that infection induces a decrease in neuroblast-neuron differentiation rates in cells stained for NF-200, with reduced neuritogenesis. Migration rates were analyzed in plated neurospheres. At 120 h after plating, infected cultures exhibited decreased overall migration rates and altered the radial migration of nestin-, GFAP- and NF-200-positive cells. These findings indicate that T. gondii infection of neural progenitor cells may lead to reduced neuro/gliogenesis due to an imbalance in cell proliferation alongside an altered migratory profile. If translated to the in vivo situation, these data could explain, in part, the cortical malformations observed in congenitally infected individuals.