Differentiation of into latent forms is linked to central carbon metabolism and requires a GID/CTLH-type E3 ubiquitin ligase.

and other Apicomplexan parasites, switch between different developmental stages to persist in and transmit between hosts. can alternate between systemic tachyzoites and encysted bradyzoite forms found in the CNS and muscle tissues. How parasites sense these tissue types and trigger differentiation remains largely unknown.

A pre-existing chronic Toxoplasma gondii infection promotes epileptogenesis and neuropathology in a mouse model of mesial temporal lobe epilepsy.

Objective: There is initial evidence that the common neurotropic parasite Toxoplasma gondii is a risk factor for the development of epilepsy; however, whether it influences epileptogenesis is unknown. This study investigated whether a pre-existing chronic T. gondii infection alters epileptogenesis and neuropathology in a mouse model of mesial temporal lobe epilepsy.

Seroprevalence and risk factors for Toxoplasma gondii exposure in Australian feral and stray cats using an in-house modified agglutination test.

Toxoplasma gondii is a globally distributed zoonotic protist, capable of infecting all warm-blooded animals. In Australia, cats (Felis catus) are the only definitive host capable of spreading T. gondii infection via oocysts.

A pre-existing Toxoplasma gondii infection exacerbates the pathophysiological response and extent of brain damage after traumatic brain injury in mice.

Traumatic brain injury (TBI) is a key contributor to global morbidity that lacks effective treatments. Microbial infections are common in TBI patients, and their presence could modify the physiological response to TBI. It is estimated that one-third of the human population is incurably infected with the feline-borne parasite, Toxoplasma gondii, which can invade the central nervous system and result in chronic low-grade neuroinflammation, oxidative stress, and excitotoxicity-all of which are also important pathophysiological processes in TBI.

Pre-existing infection increases susceptibility to pentylenetetrazol-induced seizures independent of traumatic brain injury in mice.

Introduction: Post-traumatic epilepsy (PTE) is a debilitating chronic outcome of traumatic brain injury (TBI), and neuroinflammation is implicated in increased seizure susceptibility and epileptogenesis. However, how common clinical factors, such as infection, may modify neuroinflammation and PTE development has been understudied. The neurotropic parasite, incurably infects one-third of the world's population.

Transcriptional modification of host cells harboring Toxoplasma gondii bradyzoites prevents IFN gamma-mediated cell death.

Toxoplasma gondii develops a latent infection in the muscle and central nervous system that acts as a reservoir for acute-stage reactivation in vulnerable patients. Little is understood about how parasites manipulate host cells during latent infection and the impact this has on survival. We show that bradyzoites impart a unique transcriptional signature on infected host cells.

Depletion of a Toxoplasma porin leads to defects in mitochondrial morphology and contacts with the endoplasmic reticulum.

The voltage-dependent anion channel (VDAC) is a ubiquitous channel in the outer membrane of the mitochondrion with multiple roles in protein, metabolite and small molecule transport. In mammalian cells, VDAC protein, as part of a larger complex including the inositol triphosphate receptor, has been shown to have a role in mediating contacts between the mitochondria and endoplasmic reticulum (ER). We identify VDAC of the pathogenic apicomplexan Toxoplasma gondii and demonstrate its importance for parasite growth.

Environmental sensing and regulation of motility in Toxoplasma.

Toxoplasma and other apicomplexan parasites undergo a unique form of cellular locomotion referred to as "gliding motility." Gliding motility is crucial for parasite survival as it powers tissue dissemination, host cell invasion and egress. Distinct environmental cues lead to activation of gliding motility and have become a prominent focus of recent investigation.

Metabolomic Analysis of Toxoplasma gondii Tachyzoites.

This protocol describes the use of C-stable isotope labeling, combined with metabolite profiling, to investigate the metabolism of the tachyzoite stage of the protozoan parasite Toxoplasma gondii. T. gondii tachyzoites can infect any nucleated cell in their vertebrate (including human) hosts, and utilize a range of carbon sources that freely permeate across the limiting membrane of the specialized vacuole within which they proliferate.

An apically located hybrid guanylate cyclase-ATPase is critical for the initiation of Ca signaling and motility in .

Protozoan parasites of the phylum Apicomplexa actively move through tissue to initiate and perpetuate infection. The regulation of parasite motility relies on cyclic nucleotide-dependent kinases, but how these kinases are activated remains unknown. Here, using an array of biochemical and cell biology approaches, we show that the apicomplexan parasite expresses a large guanylate cyclase (TgGC) protein, which contains several upstream ATPase transporter-like domains.

Protein -fucosyltransferase 2-mediated -glycosylation of the adhesin MIC2 is dispensable for tachyzoite infection.

is a ubiquitous, obligate intracellular eukaryotic parasite that causes congenital birth defects, disease in immunocompromised individuals, and blindness. Protein glycosylation plays an important role in the infectivity and evasion of immune responses of many eukaryotic parasites and is also of great relevance to vaccine design. Here we demonstrate that micronemal protein 2 (MIC2), a motility-associated adhesin of , has highly glycosylated thrombospondin repeat (TSR) domains.

Protein kinase A negatively regulates Ca2+ signalling in Toxoplasma gondii.

The phylum Apicomplexa comprises a group of obligate intracellular parasites that alternate between intracellular replicating stages and actively motile extracellular forms that move through tissue. Parasite cytosolic Ca2+ signalling activates motility, but how this is switched off after invasion is complete to allow for replication to begin is not understood. Here, we show that the cyclic adenosine monophosphate (cAMP)-dependent protein kinase A catalytic subunit 1 (PKAc1) of Toxoplasma is responsible for suppression of Ca2+ signalling upon host cell invasion.

Development of a Novel CD4 TCR Transgenic Line That Reveals a Dominant Role for CD8 Dendritic Cells and CD40 Signaling in the Generation of Helper and CTL Responses to Blood-Stage Malaria.

We describe an MHC class II (I-A)-restricted TCR transgenic mouse line that produces CD4 T cells specific for species. This line, termed PbT-II, was derived from a CD4 T cell hybridoma generated to blood-stage ANKA (PbA). PbT-II cells responded to all species and stages tested so far, including rodent (PbA, NK65, AS, and 17XNL) and human () blood-stage parasites as well as irradiated PbA sporozoites.

A forward genetic screen identifies a negative regulator of rapid Ca-dependent cell egress (MS1) in the intracellular parasite .

, like all apicomplexan parasites, uses Ca signaling pathways to activate gliding motility to power tissue dissemination and host cell invasion and egress. A group of "plant-like" Ca-dependent protein kinases (CDPKs) transduces cytosolic Ca flux into enzymatic activity, but how they function is poorly understood. To investigate how Ca signaling activates egress through CDPKs, we performed a forward genetic screen to isolate gain-of-function mutants from an egress-deficient knockout strain.

Merozoite Antigens of Plasmodium falciparum Elicit Strain-Transcending Opsonizing Immunity.

It is unclear whether naturally acquired immunity to Plasmodium falciparum results from the acquisition of antibodies to multiple, diverse antigens or to fewer, highly conserved antigens. Moreover, the specific antibody functions required for malaria immunity are unknown, and hence informative immunological assays are urgently needed to address these knowledge gaps and guide vaccine development. In this study, we investigated whether merozoite-opsonizing antibodies are associated with protection from malaria in a strain-specific or strain-transcending manner by using a novel field isolate and an immune plasma-matched cohort from Papua New Guinea with our validated assay of merozoite phagocytosis.

Multiple Plasmodium falciparum Merozoite Surface Protein 1 Complexes Mediate Merozoite Binding to Human Erythrocytes.

Successful invasion of human erythrocytes byPlasmodium falciparummerozoites is required for infection of the host and parasite survival. The early stages of invasion are mediated via merozoite surface proteins that interact with human erythrocytes. The nature of these interactions are currently not well understood, but it is known that merozoite surface protein 1 (MSP1) is critical for successful erythrocyte invasion.

Regulation of Starch Stores by a Ca(2+)-Dependent Protein Kinase Is Essential for Viable Cyst Development in Toxoplasma gondii.

Transmissible stages of Toxoplasma gondii store energy in the form of the carbohydrate amylopectin. Here, we show that the Ca(2+)-dependent protein kinase CDPK2 is a critical regulator of amylopectin metabolism. Increased synthesis and loss of degradation of amylopectin in CDPK2 deficient parasites results in the hyperaccumulation of this sugar polymer.

An aspartyl protease defines a novel pathway for export of Toxoplasma proteins into the host cell.

Infection by Toxoplasma gondii leads to massive changes to the host cell. Here, we identify a novel host cell effector export pathway that requires the Golgi-resident aspartyl protease 5 (ASP5). We demonstrate that ASP5 cleaves a highly constrained amino acid motif that has similarity to the PEXEL-motif of Plasmodium parasites.

The merozoite surface protein 1 complex is a platform for binding to human erythrocytes by Plasmodium falciparum.

Plasmodium falciparum is the causative agent of the most severe form of malaria in humans. The merozoite, an extracellular stage of the parasite lifecycle, invades erythrocytes in which they develop. The most abundant protein on the surface of merozoites is merozoite surface protein 1 (MSP1), which consists of four processed fragments.

Modulation of PF10_0355 (MSPDBL2) alters Plasmodium falciparum response to antimalarial drugs.

Malaria's ability to rapidly adapt to new drugs has allowed it to remain one of the most devastating infectious diseases of humans. Understanding and tracking the genetic basis of these adaptations are critical to the success of treatment and intervention strategies. The novel antimalarial resistance locus PF10_0355 (Pfmspdbl2) was previously associated with the parasite response to halofantrine, and functional validation confirmed that overexpression of this gene lowered parasite sensitivity to both halofantrine and the structurally related antimalarials mefloquine and lumefantrine, predominantly through copy number variation.

Insights into Duffy binding-like domains through the crystal structure and function of the merozoite surface protein MSPDBL2 from Plasmodium falciparum.

Invasion of human red blood cells by Plasmodium falciparum involves interaction of the merozoite form through proteins on the surface coat. The erythrocyte binding-like protein family functions after initial merozoite interaction by binding via the Duffy binding-like (DBL) domain to receptors on the host red blood cell. The merozoite surface proteins DBL1 and -2 (PfMSPDBL1 and PfMSPDBL2) (PF10_0348 and PF10_0355) are extrinsically associated with the merozoite, and both have a DBL domain in each protein.

Structural and functional association of Trypanosoma brucei MIX protein with cytochrome c oxidase complex.

A mitochondrial inner membrane protein, designated MIX, seems to be essential for cell viability. The deletion of both alleles was not possible, and the deletion of a single allele led to a loss of virulence and aberrant mitochondrial segregation and cell division in Leishmania major. However, the mechanism by which MIX exerts its effect has not been determined.

Fishing for anti-leishmania drugs: principles and problems.

To date, there are no vaccines against any of the major parasitic diseases including leishmaniasis, and chemotherapy is the main weapon in our arsenal. Current drugs are toxic and expensive, and are losing their effectiveness due to parasite resistance. The availability of the genome sequence of two species of Leishmania, Leishmania major and Leishmania infantum, as well as that of Trypanosoma brucei and Trypanosoma cruzi should provide a cornucopia of potential new drug targets.

A mitochondrial protein affects cell morphology, mitochondrial segregation and virulence in Leishmania.

The single mitochondrion of kinetoplastids divides in synchrony with the nucleus and plays a crucial role in cell division. However, despite its importance and potential as a drug target, the mechanism of mitochondrial division and segregation and the molecules involved are only partly understood. In our quest to identify novel mitochondrial proteins in Leishmania, we constructed a hidden Markov model from the targeting motifs of known mitochondrial proteins as a tool to search the Leishmania major genome.

A family of leukemia inhibitory factor-binding peptides that can act as antagonists when conjugated to poly(ethylene glycol).

A panel of six naïve 14-residue random peptide libraries displayed polyvalently on M13 phage was pooled and sorted against human leukemia inhibitory factor (LIF). After four rounds of selection, a single large family of peptides with the consensus sequence XCXXXXG(A/S)(D/E)(W/F)WXCF was found to bind specifically to LIF. Peptides within this family did not bind related members of the interleukin-6 family of cytokines, nor to murine LIF that has 80% sequence identity with human LIF.