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Rhoptry and Dense Granule Secreted Effectors Regulate CD8+ T Cell Recognition of Toxoplasma gondii Infected Host Cells. 2019

Leah M Rommereim, and Barbara A Fox, and Kiah L Butler, and Viviana Cantillana, and Gregory A Taylor, and David J Bzik
Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Lebanon, NH, United States.

Toxoplasma gondii secretes rhoptry (ROP) and dense granule (GRA) effector proteins to evade host immune clearance mediated by interferon gamma (IFN-γ), immunity-related GTPase (IRG) effectors, and CD8+ T cells. Here, we investigated the role of parasite-secreted effectors in regulating host access to parasitophorous vacuole (PV) localized parasite antigens and their presentation to CD8+ T cells by the major histocompatibility class I (MHC-I) pathway. Antigen presentation of PV localized parasite antigens by MHC-I was significantly increased in macrophages and/or dendritic cells infected with mutant parasites that lacked expression of secreted GRA (GRA2, GRA3, GRA4, GRA5, GRA7, GRA12) or ROP (ROP5, ROP18) effectors. The ability of various secreted GRA or ROP effectors to suppress antigen presentation by MHC-I was dependent on cell type, expression of IFN-γ, or host IRG effectors. The suppression of antigen presentation by ROP5, ROP18, and GRA7 correlated with a role for these molecules in preventing PV disruption by IFN-γ-activated host IRG effectors. However, GRA2 mediated suppression of antigen presentation was not correlated with PV disruption. In addition, the GRA2 antigen presentation phenotypes were strictly co-dependent on the expression of the GRA6 protein. These results show that MHC-I antigen presentation of PV localized parasite antigens was controlled by mechanisms that were dependent or independent of IRG effector mediated PV disruption. Our findings suggest that the GRA6 protein underpins an important mechanism that enhances CD8+ T cell recognition of parasite-infected cells with damaged or ruptured PV membranes. However, in intact PVs, parasite secreted effector proteins that associate with the PV membrane or the intravacuolar network membranes play important roles to actively suppress antigen presentation by MHC-I to reduce CD8+ T cell recognition and clearance of Toxoplasma gondii infected host cells.

UI MeSH Term Description Entries
D008810 Mice, Inbred C57BL One of the first INBRED MOUSE STRAINS to be sequenced. This strain is commonly used as genetic background for transgenic mouse models. Refractory to many tumors, this strain is also preferred model for studying role of genetic variations in development of diseases. Mice, C57BL,Mouse, C57BL,Mouse, Inbred C57BL,C57BL Mice,C57BL Mice, Inbred,C57BL Mouse,C57BL Mouse, Inbred,Inbred C57BL Mice,Inbred C57BL Mouse
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D000953 Antigens, Protozoan Any part or derivative of any protozoan that elicits immunity; malaria (Plasmodium) and trypanosome antigens are presently the most frequently encountered. Protozoan Antigens
D014122 Toxoplasma A genus of protozoa parasitic to birds and mammals. T. gondii is one of the most common infectious pathogenic animal parasites of man. Toxoplasma gondii,Toxoplasma gondius,Toxoplasmas,gondius, Toxoplasma
D014124 Toxoplasmosis, Animal Acquired infection of non-human animals by organisms of the genus TOXOPLASMA. Animal Toxoplasmoses,Animal Toxoplasmosis,Toxoplasmoses, Animal
D014617 Vacuoles Any spaces or cavities within a cell. They may function in digestion, storage, secretion, or excretion. Vacuole
D015800 Protozoan Proteins Proteins found in any species of protozoan. Proteins, Protozoan
D017346 Protein Serine-Threonine Kinases A group of enzymes that catalyzes the phosphorylation of serine or threonine residues in proteins, with ATP or other nucleotides as phosphate donors. Protein-Serine-Threonine Kinases,Serine-Threonine Protein Kinase,Serine-Threonine Protein Kinases,Protein-Serine Kinase,Protein-Serine-Threonine Kinase,Protein-Threonine Kinase,Serine Kinase,Serine-Threonine Kinase,Serine-Threonine Kinases,Threonine Kinase,Kinase, Protein-Serine,Kinase, Protein-Serine-Threonine,Kinase, Protein-Threonine,Kinase, Serine-Threonine,Kinases, Protein Serine-Threonine,Kinases, Protein-Serine-Threonine,Kinases, Serine-Threonine,Protein Kinase, Serine-Threonine,Protein Kinases, Serine-Threonine,Protein Serine Kinase,Protein Serine Threonine Kinase,Protein Serine Threonine Kinases,Protein Threonine Kinase,Serine Threonine Kinase,Serine Threonine Kinases,Serine Threonine Protein Kinase,Serine Threonine Protein Kinases
D051379 Mice The common name for the genus Mus. Mice, House,Mus,Mus musculus,Mice, Laboratory,Mouse,Mouse, House,Mouse, Laboratory,Mouse, Swiss,Mus domesticus,Mus musculus domesticus,Swiss Mice,House Mice,House Mouse,Laboratory Mice,Laboratory Mouse,Mice, Swiss,Swiss Mouse,domesticus, Mus musculus
D017951 Antigen Presentation The process by which antigen is presented to lymphocytes in a form they can recognize. This is performed by antigen presenting cells (APCs). Some antigens require processing before they can be recognized. Antigen processing consists of ingestion and partial digestion of the antigen by the APC, followed by presentation of fragments on the cell surface. (From Rosen et al., Dictionary of Immunology, 1989) Antigen Processing,Antigen Presentations,Antigen Processings

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