Effect of route of infection on outcome of Toxoplasma gondii infection in hu-PBL SCID mice

Toxoplasma gondii (T. gondii) causes serious infection, especially in immunocompromised hosts. The relevance of animal models of toxoplasmosis to human disease is unclear, but have indicated that the route of Toxoplasma infection may affect the outcome. A humanized model of toxoplasmosis of immunocompromised mice (i.e. hu-PBL SCID), using the intraperitoneal (IP) route demonstrated long-term engraftment of human cells and worsening of inflammation compared to controls. In this study, we examined the effect of route of infection on this hu-PBL SCID model using a Toxoplasma strain (i.e. DAG) isolated from an immunocompromised human. Oral infection led to an asymptomatic infection, whereas animals infected by the IP route succumbed more quickly to infection. Human cells, detected through species-specific β-actin mRNA, were not as prominent in IP-infected animals as compared to orally infected and uninfected animals. There was evidence of control of toxoplasmosis in some orally infected animals, and this was associated with the presence of human cells in multiple tissues. Thus, the route of infection dramatically affects the outcome of infection, either by affecting parasite replication or expansion of human immune cells. Further studies of oral Toxoplasma infection using hu-PBL SCID mice may help in developing chemotherapies and immunotherapeutic strategies for toxoplasmosis.