Feline intestinal explants to study interactions of Toxoplasma gondii with the mucosal immune response of its definitive host

International audience

anglais. Toxoplasma gondii is the 3rd most important foodborne parasite identified by the FAO/WHO as a threat to public health. The development of effective vaccines or drugs against toxoplasmosis has largely been hampered by the lack of data on the T. gondii sexual reproductive cycle, which occurs only in felids. We study T. gondii interactions with the feline intestinal microenvironment to decipher local immune responses and understand their impact on the parasite life cycle, to discover new ways to target this clinically important protozoan. We developed a model of feline intestinal explants, which has been previously used to study different intestinal pathologies in various species, but has never been developed in cats. To study the local feline immune response, we used for the first time the RNAscope® technology on intestinal tissue to follow cytokines expression upon different culture conditions and in presence of T. gondii. Culture condition modalities included variation of the duration of the incubation, as well as the atmosphere composition. So far, our work followed the expression of four key Th1/Th2 cytokines: IFN-/IL-12 and IL-4/IL-5. Explant enterocytes can be infected by T. gondii tachyzoites within 24h of infection ex vivo. All four cytokines are expressed in the tissues at the mRNA level, with IL-4 showing the lowest expression. Variation in cytokine expression are observed depending on the length of the incubation, and the presence or the absence of the parasite in the tissues. Moreover, incubation in hyperoxia conditions to extend tissue survival induces variation in both Th1 and Th2 cytokine expression. Quantifications of these observations are currently ongoing.These preliminary results validate the use of intestinal explants and the RNAscope® technology to study T. gondii interactions with the feline intestinal mucosa and the local immune response. They also highlight the need to further standardize the model to allow clear comparisons. Together with other feline cellular models under development, deciphering these specific interactions will help to improve vaccine strategies and protect animal and public health.