Characterising Toxoplasma gondii virulence: role of host and pathogen

Toxoplasma gondii is a major foodborne pathogen as well as a significant cause of ovine abortion worldwide. Research into its genetic diversity has revealed an abundance of atypical strains in South America where there are more cases of severe toxoplasmosis. Despite T. gondii being an important foodborne pathogen, there is little data on the role of meat products in transmission. Meat consumption in Brazil is extremely high so it is crucial to determine its role in T. gondii transmission particularly given the high incidence of atypical strains in this region. The mouse has been an invaluable tool in investigating T. gondii virulence; however, given the lack of evidence of a correlation between virulence in mice versus higher animals, there is an urgent need for a more relevant, host-specific system for identifying host and pathogen factors involved in virulence and predicting disease outcome. This project aims to address the knowledge gaps and assess the role of meatborne transmission as well as characterise virulence in a host-specific system. We will 1) use molecular, in vitro and in vivo techniques to assess the incidence, viability, genetic diversity and virulence of T. gondii in different retail meat products in São Paulo; 2) compare virulent and non-virulent strains of T. gondii using whole genome sequencing to identify markers for virulence; 3) analyse parasite invasion, proliferation and parasite and host-cell gene expression during acute infection of murine, ovine and human cells infected with virulent and non-virulent strains of the parasite; 4) determine the applicability of in vitro 3D host-specific gut organoids (enteroids) for characterising virulence of T. gondii in relevant hosts. Outputs from this project will greatly improve our understanding of foodborne transmission and T. gondii virulence and will provide an in vitro host-specific platform to enable vaccine design and drug discovery in a relevant system.