Toxoplasma gondii-Induced Neutrophil Extracellular Traps Amplify the Innate and Adaptive Response

Approximately one-third of the human population is estimated to be chronically infected with the obligate intracellular parasite Toxoplasma gondii . Humans are accidental hosts that are infected with T. gondii after consumption of undercooked meat or contaminated water.

Cryo-ET reveals two major tubulin-based cytoskeleton structures in Toxoplasma gondii

In the obligate intracellular parasite, Toxoplasma gondii, the subpellicular microtubules (SPMTs) help maintain shape, while the apical conoid (also tubulin-based) is implicated in invasion. Here, we use cryo-electron tomography to determine the molecular structures of the SPMTs and the conoid-fibrils (CFs) in vitrified and detergent-lysed parasites. Subvolume densities from detergent-extracted parasites yielded averaged density maps at subnanometer resolutions, and these were related back to their architecture in situ. An intraluminal spiral (IS) lines the interior of the 13-protofilament SPMTs, revealing a preferred orientation of these microtubules relative to the parasite's long axis. Each CF is composed of 9 tubulin protofilaments, that produce a comma-shaped cross-section, plus additional associated components. Conoid protrusion, a crucial step in invasion, is associated with an altered pitch of each CF. The use of basic building blocks of protofilaments and different accessory proteins in one organism, illustrates the versatility of these critical structures.

Actin and an unconventional myosin motor, TgMyoF, control the organization and dynamics of the endomembrane network in Toxoplasma gondii

Toxoplasma gondii is an obligate intracellular parasite that relies on three distinct secretory organelles, the micronemes, rhoptries, and dense granules, for parasite survival and disease pathogenesis. Secretory proteins destined for these organelles are synthesized in the endoplasmic reticulum (ER) and sequentially trafficked through a highly polarized endomembrane network that consists of the Golgi and multiple post-Golgi compartments. Currently, little is known about how the parasite cytoskeleton controls the positioning of the organelles in this pathway, or how vesicular cargo is trafficked between organelles. Here we show that F-actin and an unconventional myosin motor, TgMyoF, control the dynamics and organization of the organelles in the secretory pathway, specifically ER tubule movement, apical positioning of the Golgi and post-Golgi compartments, apical positioning of the rhoptries, and finally, the directed transport of Rab6-positive and Rop1-positive vesicles. Thus, this study identifies TgMyoF and actin as the key cytoskeletal components that organize the endomembrane system in T. gondii.

Chlamydia trachomatis TmeA Directly Activates N-WASP To Promote Actin Polymerization and Functions Synergistically with TarP during Invasion

ABSTRACT Chlamydia trachomatis is a medically significant human pathogen and is an epithelial-tropic obligate intracellular parasite. Invasion of nonprofessional phagocytes represents a crucial step in the infection process and has likely promoted the evolution of a redundant mechanism and routes of entry. Like many other viral and invasive bacterial pathogens, manipulation of the host cell cytoskeleton represents a focal point in Chlamydia entry. The advent of genetic techniques in C. trachomatis, such as creation of complete gene deletions via fluorescence-reported allelic exchange mutagenesis (FRAEM), is providing important tools to unravel the contributions of bacterial factors in these complex pathways. The type III secretion chaperone Slc1 directs delivery of at least four effectors during the invasion process. Two of these, TarP and TmeA, have been associated with manipulation of actin networks and are essential for normal levels of invasion. The functions of TarP are well established, whereas TmeA is less well characterized. We leverage chlamydial genetics and proximity labeling here to provide evidence that TmeA directly targets host N-WASP to promote Arp2/3-dependent actin polymerization. Our work also shows that TmeA and TarP influence separate, yet synergistic pathways to accomplish chlamydial entry. These data further support an appreciation that a pathogen, confined by a reductionist genome, retains the ability to commit considerable resources to accomplish bottle-neck steps during the infection process. IMPORTANCE The increasing genetic tractability of Chlamydia trachomatis is accelerating the ability to characterize the unique infection biology of this obligate intracellular parasite. These efforts are leading to a greater understanding of the molecular events associated with key virulence requirements. Manipulation of the host actin cytoskeleton plays a pivotal role throughout Chlamydia infection, yet a thorough understanding of the molecular mechanisms initiating and orchestrating actin rearrangements has lagged. Our work highlights the application of genetic manipulation to address open questions regarding chlamydial invasion, a process essential to survival. We provide definitive insight regarding the role of the type III secreted effector TmeA and how that activity relates to another prominent effector, TarP. In addition, our data implicate at least one source that contributes to the functional divergence of entry mechanisms among chlamydial species.

Insight Into Inflammasome Signaling: Implications for Toxoplasma gondii Infection

Inflammasomes are multimeric protein complexes regulating the innate immune response to invading pathogens or stress stimuli. Recent studies have reported that nucleotide-binding leucine-rich repeat-containing (NLRs) proteins and DNA sensor absent in melanoma 2 (AIM2) serve as inflammasome sentinels, whose stimulation leads to the proteolytic activation of caspase-1, proinflammatory cytokine secretion, and pyroptotic cell death. Toxoplasma gondii, an obligate intracellular parasite of phylum Apicomplexans, is reportedly involved in NLRP1, NLRP3 and AIM2 inflammasomes activation; however, mechanistic evidence regarding the activation of these complexes is preliminary. This review describes the current understanding of inflammasome signaling in rodent and human models of T. gondii infection.

Serum Tyrosine Level in Acute Murine Toxoplasmosis

Background: Toxoplasmosis is a zoonotic disease caused by the obligate intracellular parasite, Toxoplasma gondii. This global infectious disease has been associated with behavioral changes in rodents and can result in humans' neuropsychiatric symptoms. Since the neurotransmitters alteration can cause a behavioral change, in this study, tyrosine level, as a precursor of dopamine, was evaluated in acute murine toxoplasmosis during 2015 and 2016 in Shiraz, Iran. Methods: At the first, 105 tachyzoites of T. gondii were subcutaneously inoculated to 50 BALB/c mice as experimental groups and 10 mice inoculated by PBS considered as the control group. After that, daily, one group of mice was bled, and sera were collected. Then, their serum tyrosine level was evaluated by HPLC method. Results: After data analysis, the maximum mean serum tyrosine level was seen at 2th day of post parasite inoculation (0.0194 mg/ ml), with a significant difference compared to the control group (0.0117 mg/ ml, P=0.025). Moreover, the least quantity of serum tyrosine (0.076 mg/ml) was seen on the 5th day, after parasite inoculation, however, no significant difference was seen. Conclusion: Serum tyrosine level increased in 2 d after inoculation of Toxoplasma, but the level regularly decreased in successive days. Tyrosine level increased by phenylalanine hydroxylase 2 days after inoculation, then tyrosine decreased by tyrosine hydroxylase in the next days. Toxoplasma tyrosine hydroxylase enzymes, at primary days of toxoplasmosis, effect on tyrosine production, and after that, the most effect on tyrosine consumption.

The occurrence of Toxoplasma gondii on raw leafy vegetables in Gaza - Palestine

Toxoplasma gondii a ubiquitous obligate intracellular parasite that can infect all warm-blooded animals, is one of the main pathogens causing foodborne diseases worldwide. In Gaza – Palestine, the leafy vegetables are frequently eaten raw. The present study was carried out to investigate the occurrence of T. gondii oocyst in local leafy vegetables. For this purpose, fifty samples of each kind of six different leafy plants sold in markets, supermarkets, and retail sellers were randomly collected during the period from March to August 2019. , the three hundred samples were collected from six different species of leafy vegetables. The samples were examined microscopy through using a light microscope and after performing the flotation technique of Sheather's solution to easily detect the oocysts, the suspected samples were confirmed by using PCR technique. Upon analyzing the samples and using the PCR method, only 19 out of the 300 samples (6.33 %) were found to be contaminated, whereas by using Sheather's solution method, 35 out of the 300 samples (11.66%) were contaminated. Among the six various plants and according to the PCR method, mint held the highest rate of contamination (10.00 %), followed by both watercress and dill with a similar percentage (8.00%), parsley (6.00%), thyme (4.00%), and finally, lettuce carrying the lowest rate (2.00%). Even though the sequence among those contaminated plants was found similar in the PCR and the Sheather's solution, the rates were different. With this method, mint stood at (18.00%), watercress (14.00%), dill (13.00%), parsley (10.00%), thyme (10.00%) and lettuce (6.00%). Moreover, the present study has reported that the relationship between the period of collection and T. gondii contamination is statistically significant. Whereby, the highest rate of contamination recorded was in July, followed by June, then August. Based on the findings of the present study, leafy vegetables are quite vulnerable to T. gondii contamination.

ClubrootTracker: A Resource to Plan a Clubroot-Free Farm

Clubroot is a devastating disease affecting cruciferous crops worldwide. Clubroot was first described in the 13th century in Russia and from that moment has been affecting European, Asian, and American brassica production. Plasmodiophora brassicae is the clubroot causal agent, and it is an obligate intracellular parasite that, as soil-borne resting spores, can remain viable in soil for many years. This persistence in the soil is a major negative contributing factor to the management of clubroot disease and highlights the importance for brassica growers to have ready access to current information on the distribution of the pathogen. The interactive online tool ClubrootTracker ( http://clubroottracker.ca ) has been developed to enable users to view pathogen and disease presence in geographic locations across the world. ClubrootTracker, as described in this manuscript, has been developed to provide brassica farmers a tool that will contribute to clubroot management and aid in planning a clubroot-free farm. This tool is an open resource that has the main goal of acquisition of GPS information in reporting the pathogen or the disease by the researchers working with it around the world.

Metabolic interactions between Toxoplasma gondii and its host

Toxoplasma gondii is an obligate intracellular parasite belonging to the phylum Apicomplexa that infects all warm-blooded animals, including humans. T. gondii can replicate in every nucleated host cell by orchestrating metabolic interactions to derive crucial nutrients. In this review, we summarize the current status of known metabolic interactions of T. gondii with its host cell and discuss open questions and promising experimental approaches that will allow further dissection of the host–parasite interface and discovery of ways to efficiently target both tachyzoite and bradyzoite forms of T. gondii, which are associated with acute and chronic infection, respectively.

A secretory hexokinase plays an active role in the proliferation of Nosema bombycis

The microsporidian Nosema bombycis is an obligate intracellular parasite of Bombyx mori, that lost its intact tricarboxylic acid cycle and mitochondria during evolution but retained its intact glycolysis pathway. N. bombycis hexokinase (NbHK) is not only a rate-limiting enzyme of glycolysis but also a secretory protein. Indirect immunofluorescence assays and recombinant HK overexpressed in BmN cells showed that NbHK localized in the nucleus and cytoplasm of host cell during the meront stage. When N. bombycis matured, NbHK tended to concentrate at the nuclei of host cells. Furthermore, the transcriptional profile of NbHK implied it functioned during N. bombycis’ proliferation stages. A knock-down of NbHK effectively suppressed the proliferation of N. bombycis indicating that NbHK is an important protein for parasite to control its host.