Modelling parasite dissemination: host cell subversion and immune evasion by Toxoplasma gondii

Protozoan parasites belong to the most widespread and devastating human pathogens. Their ability to manipulate host responses and establish infection in their hosts continues to puzzle researchers. Recent developments of experimental model systems are contributing to the discovery of new aspects of the biology of parasite dissemination. Here, we review current knowledge on strategies utilized by the apicomplexan parasite Toxoplasma gondii to disseminate and establish infection in its host. Recent findings have revealed intricate mechanisms by which this obligate intracellular protozoan sequesters cellular functions of the immune system to assure propagation. These mechanisms include the hijacking of migratory leucocytes, modulation of migratory properties of infected cells and rapid transfer of parasites between different leucocyte populations by cytotoxicity-induced parasite egress. Collectively, Toxoplasma strikes a delicate balance, assuring efficient dissemination and establishment of asymptomatic lifelong infection in its host while protecting its intracellular entity and limiting host pathology.