RESUMO
Toxoplasma gondii is remarkably unique in its ability to successfully infect vertebrate hosts from multiple phyla and can successfully infect most cells within these organisms. The infection outcome in each of these species is determined by the complex interaction between parasite and host genotype. As techniques to quantify global changes in cell function become more readily available and precise, new data are coming to light about how (i) different host cell types respond to parasitic infection and (ii) different parasite species impact the host. Here we focus on recent studies comparing the response to intracellular parasitism by different cell types and insights into understanding host-parasite interactions from comparative studies on T. gondii and its close extant relatives.
Assuntos
Interações Hospedeiro-Parasita , Toxoplasma , Toxoplasmose , Animais , Apicomplexa/genética , Apicomplexa/imunologia , Apicomplexa/metabolismo , Evolução Biológica , Linhagem Celular , Quimiocinas/metabolismo , Coccidiose/imunologia , Coccidiose/parasitologia , Expressão Gênica , Especificidade de Hospedeiro/genética , Interações Hospedeiro-Parasita/genética , Interações Hospedeiro-Parasita/fisiologia , Humanos , Imunidade , Interferon gama/metabolismo , Mamíferos/parasitologia , Neospora/genética , Neospora/imunologia , Neospora/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas de Protozoários , Células THP-1 , Toxoplasma/genética , Toxoplasma/imunologia , Toxoplasma/metabolismo , Toxoplasmose/imunologia , Toxoplasmose/parasitologia , Transcriptoma , Proteína Supressora de Tumor p53/metabolismo , Virulência/genéticaRESUMO
Most eukaryotic parasites are obligately heteroxenous, requiring sequential infection of different host species in order to survive. Toxoplasma gondii is a rare exception to this rule, having a uniquely facultative heteroxenous life cycle. To understand the origins of this phenomenon, we compared development and stress responses in T. gondii to those of its its obligately heteroxenous relative, Hammondia hammondi and have identified multiple H. hammondi growth states that are distinct from those in T. gondii. Of these, the most dramatic difference was that H. hammondi was refractory to stressors that robustly induce cyst formation in T. gondii, and this was reflected most dramatically in its unchanging transcriptome after stress exposure. We also found that H. hammondi could be propagated in vitro for up to 8 days post-excystation, and we exploited this to generate the first ever transgenic H. hammondi line. Overall our data show that H. hammondi zoites grow as stringently regulated, unique life stages that are distinct from T. gondii tachyzoites, and implicate stress sensitivity as a potential developmental innovation that increased the flexibility of the T. gondii life cycle.
