T lymphocyte-dependent IL-10 down-regulates a cytokine storm driven by GRA24.

As a model organism in the study of immunity to infection, has been instrumental in establishing key principles of host anti-microbial defense and its regulation. Here, we employed an attenuated uracil auxotroph strain of Type I designated OMP to further untangle the early immune response to this parasitic pathogen. Experiments using αβ T cell-deficient mice unexpectedly revealed that an intact αβ T lymphocyte compartment was essential to survive infection with OMP.

chitinase-like protein TgCLP1 regulates the parasite cyst burden.

, an important intracellular parasite of humans and animals, causes life-threatening toxoplasmosis in immunocompromised individuals. Although secretory proteins during acute infection (tachyzoite, which divides rapidly and causes inflammation) have been extensively characterized, those involved in chronic infection (bradyzoite, which divides slowly and is surrounded by a cyst wall) remain uncertain. Regulation of the cyst wall is essential to the parasite life cycle, and polysaccharides, such as chitin, in the cyst wall are necessary to sustain latent infection.

Protective efficacy of recombinant Toxoplasma gondii dense granule protein 15 against toxoplasmosis in C57BL/6 mice.

Toxoplasma gondii is a pervasive protozoan parasite that is responsible for significant zoonoses. A wide array of vaccines using different effector molecules of T. gondii have been studied worldwide to control toxoplasmosis.

From O/GABA-AT, GABA, and T-263 Mutant to Conception of .

causes morbidity, mortality, and disseminates widely via cat sexual stages. Here, we find ornithine aminotransferase (OAT) is conserved across phyla. We solve O/GABA-AT structures with bound inactivators at 1.

Dense granule protein 3 of plays a crucial role in the capability of the tissue cysts of the parasite to persist in the presence of anti-cyst CD8 T cells during the chronic stage of infection.

establishes chronic infection by forming tissue cysts, and this chronic infection is one of the most common parasitic infections in humans. Our recent studies revealed that whereas CD8 T cells of genetically resistant BALB/c mice have the capability to remove the tissue cysts of the parasite through their perforin-mediated activities, small portions of the cysts are capable of persisting in the presence of the anti-cyst CD8 T cells. It is currently unknown how those small portions of the cysts resist or escape the T-cell immunity and persist in the hosts.

Theft of Host Transferrin Receptor-1 by is required for infection.

Nutrient acquisition by apicomplexan parasites is essential to drive their intracellular replication, yet the mechanisms that underpin essential nutrient acquisition are not defined. Using the apicomplexan model , we show that host cell proteins including the transferrin receptor 1, transferrin, ferritin heavy and light chains, and clathrin light chain are robustly taken up by tachyzoites. Tachyzoite acquisition of host cell protein was not related to host cell type or parasite virulence phenotypes.

Cutting Edge: CD36 Mediates Phagocyte Tropism and Avirulence of .

Resistance and tolerance are vital for survivability of the host-pathogen relationship. Virulence during infection in mice is mediated by parasite kinase-dependent antagonism of IFN-γ-induced host resistance. Whether avirulence requires expression of parasite factors that induce host tolerance mechanisms or is a default status reflecting the absence of resistance-interfering factors is not known.

A Family of Toxoplasma gondii Genes Related to GRA12 Regulate Cyst Burdens and Cyst Reactivation.

causes a chronic infection that renders the immunocompromised human host susceptible to toxoplasmic encephalitis triggered by cyst reactivation in the central nervous system. The dense granule protein GRA12 is a major parasite virulence factor required for parasite survival during acute infection. Here, we characterized the role of four GRA12-related genes in acute and chronic stages of infection.

Toxoplasma gondii dense granule protein GRA24 drives MyD88-independent p38 MAPK activation, IL-12 production and induction of protective immunity.

The apicomplexan Toxoplasma gondii induces strong protective immunity dependent upon recognition by Toll-like receptors (TLR)11 and 12 operating in conjunction with MyD88 in the murine host. However, TLR11 and 12 proteins are not present in humans, inspiring us to investigate MyD88-independent pathways of resistance. Using bicistronic IL-12-YFP reporter mice on MyD88+/+ and MyD88-/- genetic backgrounds, we show that CD11c+MHCII+F4/80- dendritic cells, F4/80+ macrophages, and Ly6G+ neutrophils were the dominant cellular sources of IL-12 in both wild type and MyD88 deficient mice after parasite challenge.

Succinylated Wheat Germ Agglutinin Colocalizes with the Toxoplasma gondii Cyst Wall Glycoprotein CST1.

The glycosylated mucin domain of the cyst wall glycoprotein CST1 is heavily stained by agglutinin, a lectin that binds to -acetylgalactosamine. The cyst wall is also heavily stained by the chitin binding lectin succinylated wheat germ agglutinin (s-WGA), which selectively binds to acetylglucosamine-decorated structures. Here, we tracked the localization of acetylglucosamine-decorated structures that bind to s-WGA in immature and mature cysts.

Toxoplasma gondii Parasitophorous Vacuole Membrane-Associated Dense Granule Proteins Regulate Maturation of the Cyst Wall.

After differentiation is triggered, the tachyzoite-stage parasitophorous vacuole membrane (PVM) has been hypothesized to transition into the cyst membrane that surrounds the cyst wall and encloses bradyzoites. Here, we tracked the localization of two PVM dense granule (GRA) proteins (GRA5 and GRA7) after differentiation of the tachyzoite stage parasitophorous vacuole into the mature cyst. GRA5 and GRA7 were visible at the cyst periphery at 6 h and at all later times after differentiation, suggesting that the PVM remained intact as it transitioned into the cyst membrane.

Toxoplasma gondii Intravacuolar-Network-Associated Dense Granule Proteins Regulate Maturation of the Cyst Matrix and Cyst Wall.

Little is known regarding how the chronic cyst develops. Here, we investigated intravacuolar-network-associated dense granule (GRA) proteins GRA1, GRA2, GRA4, GRA6, GRA9, and GRA12 during cyst development after differentiation of the tachyzoite-stage parasitophorous vacuole. By day 1 postdifferentiation, GRA1, GRA4, GRA6, GRA9, and GRA12 colocalized with agglutinin stain at the cyst periphery.

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

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.

CD40 in Endothelial Cells Restricts Neural Tissue Invasion by Toxoplasma gondii.

Little is known about whether pathogen invasion of neural tissue is affected by immune-based mechanisms in endothelial cells. We examined the effects of endothelial cell CD40 on invasion of the retina and brain, organs seeded hematogenously. circulates in the bloodstream within infected leukocytes (including monocytes and dendritic cells) and as extracellular tachyzoites.

The dense granule protein 8 (GRA8) is a component of the sub-pellicular cytoskeleton in Toxoplasma gondii.

After host cell invasion, Toxoplasma secretes a variety of dense granule proteins (GRA proteins) from its secretory dense granules, which are involved in the biogenesis of the parasitophorous vacuole (PV). TgGRA8 is predicted to contain proline-rich domains, which are structural features of some cytoskeleton-related proteins. In agreement with this observation, previous proteomic analyses revealed the presence of TgGRA8 in the Toxoplasma sub-pellicular cytoskeleton.

Glycolysis is important for optimal asexual growth and formation of mature tissue cysts by Toxoplasma gondii.

Toxoplasma gondii can grow and replicate using either glucose or glutamine as the major carbon source. Here, we have studied the essentiality of glycolysis in the tachyzoite and bradyzoite stages of T. gondii, using transgenic parasites that lack a functional hexokinase gene (Δhk) in RH (Type-1) and Prugniaud (Type-II) strain parasites.

Lactate dehydrogenase in Toxoplasma gondii controls virulence, bradyzoite differentiation, and chronic infection.

In the asexual stages, Toxoplasma gondii stage converts between acute phase rapidly replicating tachyzoites and chronic phase slowly dividing bradyzoites. Correspondingly, T. gondii differentially expresses two distinct genes and isoforms of the lactate dehydrogenase enzyme, expressing LDH1 exclusively in the tachyzoite stage and LDH2 preferentially in the bradyzoite stage.

Pyrimidine Pathway-Dependent and -Independent Functions of the Toxoplasma gondii Mitochondrial Dihydroorotate Dehydrogenase.

Dihydroorotate dehydrogenase (DHODH) mediates the fourth step of de novo pyrimidine biosynthesis and is a proven drug target for inducing immunosuppression in therapy of human disease as well as a rapidly emerging drug target for treatment of malaria. In Toxoplasma gondii, disruption of the first, fifth, or sixth step of de novo pyrimidine biosynthesis induced uracil auxotrophy. However, previous attempts to generate uracil auxotrophy by genetically deleting the mitochondrion-associated DHODH of T.

Secretion of Rhoptry and Dense Granule Effector Proteins by Nonreplicating Toxoplasma gondii Uracil Auxotrophs Controls the Development of Antitumor Immunity.

Nonreplicating type I uracil auxotrophic mutants of Toxoplasma gondii possess a potent ability to activate therapeutic immunity to established solid tumors by reversing immune suppression in the tumor microenvironment. Here we engineered targeted deletions of parasite secreted effector proteins using a genetically tractable Δku80 vaccine strain to show that the secretion of specific rhoptry (ROP) and dense granule (GRA) proteins by uracil auxotrophic mutants of T. gondii in conjunction with host cell invasion activates antitumor immunity through host responses involving CD8α+ dendritic cells, the IL-12/interferon-gamma (IFN-γ) TH1 axis, as well as CD4+ and CD8+ T cells.

The Toxoplasma gondii Rhoptry Kinome Is Essential for Chronic Infection.

Unlabelled: Ingestion of the obligate intracellular protozoan parasite Toxoplasma gondii causes an acute infection that leads to chronic infection of the host. To facilitate the acute phase of the infection, T. gondii manipulates the host response by secreting rhoptry organelle proteins (ROPs) into host cells during its invasion.

Attenuated therapy of disseminated pancreatic cancer generates long-lasting immunity to pancreatic cancer.

We have recently reported that treatment of disseminated pancreatic cancer with an attenuated uracil auxotroph vaccine promoted antitumor CD8 T cell responses and long-term survival. Here, we optimized the treatment strategy for disseminated pancreatic cancer and show that attenuated therapy stimulated effective long-term immunity to pancreatic cancer through mechanisms involving CD4 T cells and pancreatic tumor-specific IgG. Our results suggest that cell-mediated immunity in conjunction with humoral antibody immunity may offer greater resistance to recurrence of highly aggressive tumors.

Intravacuolar Membranes Regulate CD8 T Cell Recognition of Membrane-Bound Toxoplasma gondii Protective Antigen.

Apicomplexa parasites such as Toxoplasma gondii target effectors to and across the boundary of their parasitophorous vacuole (PV), resulting in host cell subversion and potential presentation by MHC class I molecules for CD8 T cell recognition. The host-parasite interface comprises the PV limiting membrane and a highly curved, membranous intravacuolar network (IVN) of uncertain function. Here, using a cell-free minimal system, we dissect how membrane tubules are shaped by the parasite effectors GRA2 and GRA6.