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Background: BALB/c mice control infection with the obligate intracellular parasite Toxoplasma gondii and develop a latent chronic infection in the brain, as do immunocompetent humans. Interferon-gamma-producing CD8+ T cells provide essential protection against T. gondii infection, but the epitopes recognized have so far remained elusive.Methods: We employed caged major histocompatibility complex molecules to generate approximately 250 H-2L(d) tetramers and to distinguish T. gondii-specific CD8+ T cells in BALB/c mice.Results: We identified 2 T. gondii-specific H-2L(d)-restricted T cell epitopes, one from dense granule protein GRA4 and the other from rhoptry protein ROP7. H-2L(d)/GRA4 reactive T cells from multiple organ sources predominated 2 weeks after infection, while the reactivity of the H-2L(d)/ROP7 T cells peaked 6-8 weeks after infection. BALB/c animals infected with T. gondii mutants defective in establishing a chronic infection showed altered levels of antigen-specific T cells, depending on the T. gondii mutant used.Conclusions: Our results shed light on the identity and the parasite stage-specificity of 2 CD8+ T cell epitopes recognized in the acute and chronic phase of infection with T. gondii. [ABSTRACT FROM AUTHOR]

Oral transmission of parasites via environmentally resistant cyst stages in contaminated food or water is a common route of human infection, but there are no effective vaccines available for any enteric parasitic infection. Our knowledge of parasite cyst stage conversion and interaction with the intestinal tract is limited. Here, we investigate infection dynamics of Toxoplasma gondii cyst-stage in murine jejunum and human intestinal microphysiological systems. We focus on parasite ingress, replication, and conversion of the cyst stage to the rapidly replicating dissemination stage. In vivo bioluminescent imaging of mice fed cysts revealed spots of infection throughout the jejunum and ileum, which were selected for further analyses. Immunostaining showed parasite migration and replication predominantly in the stroma, with minimal replication in enterocytes. We recapitulated bradyzoite infection in human intestinal microphysiological systems and showed stage conversation and migration through collagen. This integrated approach elucidates complex host-parasite interactions, highlighting the value of microphysiological systems in advancing understanding and identifying potential therapeutics., Competing Interests: We have read the journal's policy, and the authors of this manuscript have the following competing interests: DJB holds equity in Bellbrook Labs LLC, Tasso Inc., Salus Discovery LLC, Lynx Biosciences Inc., Stacks to the Future LLC, Turba LLC, Flambeau Diagnostics LLC, and Onexio Biosystems LLC. DJB is also a consultant for Abbott Laboratories. The other authors declare that they have no competing interests., (Copyright: © 2025 Ramírez-Flores et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Reactivation of a latent infection by the protozoan parasite Toxoplasma gondii can result in severe neurologic outcomes and even death. T. gondii reactivation cases have been strongly associated with acquired immunodeficiency syndrome, but other immunosuppressive situations are also associated. Anti-TNF-α therapy reliably triggers the reactivation of T. gondii latent cysts in mice models. Reactivation of T. gondii by TNF-a blockade is rare in humans though despite widespread use of TNF-a blockers. Serologic evidence of a possible latent T. gondii infection in humans is common worldwide, so why anti-TNF-α reactivation isn't more common is unknown. Here we present a 74-year-old woman who developed fatal cerebral toxoplasmosis after anti-tumor necrosis factor-α (TNF-α). After presenting to a local urgent care with confusion, a worsening cognitive status led to an emergency room visit. Computed tomography resulted in suspicion of metastatic disease leading to treatment with steroids. Lumbar puncture ruled out bacterial or viral meningitis. With continued cognitive decline, magnetic resonance imaging of the head revealed an increased number of lesions with T. gondii -associated ring-enhancing lesions. A brain biopsy confirmed the presence of T. gondii parasites. Despite standard treatment for toxoplasmosis, the patient expired. At least two possible factors may have contributed to this unfortunate outcome. First, in addition to her rheumatoid arthritis pathology, there is evidence of loss of immune resilience and abnormal T cell subsets. Second, some strains of T. gondii are more virulent than others. Post-mortem mass spectrometry and proteomic analysis of her cerebrospinal fluid show several T. gondii peptides. A literature review suggests that risks associated with anti-TNF-α therapy for patients who are seropositive for T. gondii have not been adequately recognized. We advise T. gondii seropositivity testing be considered before and after initiation of anti-TNF-α therapy as is done for other infections such as tuberculosis., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Dr. Striker is a consultant for Pfizer, Salus Discovery and Voiant., (© 2025 The Authors.)

Bacterial biotherapeutic delivery vehicles have the potential to treat a variety of diseases. This approach obviates the need to purify the recombinant effector molecule, allows delivery of therapeutics in situ via oral or intranasal administration, and protects the effector molecule during gastrointestinal transit. Lactic acid bacteria have been broadly developed as therapeutic delivery vehicles though risks associated with the colonization of a genetically modified microorganism have so-far not been addressed. Here, we present an engineered Limosilactobacillus reuteri strain with reduced colonization potential. We applied a dual-recombineering scheme for efficient barcoding and generated mutants in genes encoding five previously characterized and four uncharacterized putative adhesins. Compared with the wild type, none of the mutants were reduced in their ability to survive gastrointestinal transit in mice. CmbA was identified as a key protein in L. reuteri adhesion to HT-29 and enteroid cells. The nonuple mutant, a single strain with all nine genes encoding adhesins inactivated, had reduced capacity to adhere to enteroid monolayers. The nonuple mutant producing murine IFN-β was equally effective as its wild-type counterpart in mitigating radiation toxicity in mice. Thus, this work established a novel therapeutic delivery platform that lays a foundation for its application in other microbial therapeutic delivery candidates and furthers the progress of the L. reuteri delivery system towards human use.IMPORTANCEOne major advantage to leverage gut microbes that have co-evolved with the vertebrate host is that evolution already has taken care of the difficult task to optimize survival within a complex ecosystem. The availability of the ecological niche will support colonization. However, long-term colonization of a recombinant microbe may not be desirable. Therefore, strategies need to be developed to overcome this potential safety concern. In this work, we developed a single strain in which we inactivated the encoding sortase, and eight genes encoding characterized/putative adhesins. Each individual mutant was characterized for growth and adhesion to epithelial cells. On enteroid cells, the nonuple mutant has a reduced adhesion potential compared with the wild-type strain. In a model of total-body irradiation, the nonuple strain engineered to release murine interferon-β performed comparable to a derivative of the wild-type strain that releases interferon-β. This work is an important step toward the application of recombinant L. reuteri in humans., Competing Interests: J.-P.V.P received unrestricted funds from BioGaia AB, a probiotic-producing company. J.-P.V.P is the founder of the consulting company Next-Gen Probiotics, LLC. J.-P.V.P. and L.M.A. are inventors on a patent application describing the development of microbes with reduced adhesion characteristics

The obligate intracellular parasite Toxoplasma gondii can infect and replicate in any warm-blooded cell tested to date, but much of our knowledge about T. gondii cell biology comes from just one host cell type: human foreskin fibroblasts (HFFs). To expand our knowledge of host-parasite lipid interactions, we studied T. gondii in intestinal epithelial cells, the first site of host-parasite contact following oral infection and the exclusive site of parasite sexual development in feline hosts. We found that highly metabolic Caco-2 cells are permissive to T. gondii growth even when treated with high levels of linoleic acid (LA), a polyunsaturated fatty acid (PUFA) that kills parasites in HFFs. Caco-2 cells appear to sequester LA away from the parasite, preventing membrane disruptions and lipotoxicity that characterize LA-induced parasite death in HFFs. Our work is an important step toward understanding host-parasite interactions in feline intestinal epithelial cells, an understudied but important cell type in the T. gondii life cycle., Competing Interests: The authors declare no conflict of interest.

Toxoplasma gondii, the causative agent of toxoplasmosis, is an obligate intracellular parasite that infects warm-blooded vertebrates across the world. In humans, seropositivity rates of T. gondii range from 10% to 90% across communities. Despite its prevalence, few studies address how T. gondii infection changes the metabolism of host cells. In this study, we investigate how T. gondii manipulates the host cell metabolic environment by monitoring the metabolic response over time using noninvasive autofluorescence lifetime imaging of single cells, metabolite analysis, extracellular flux analysis, and reactive oxygen species (ROS) production. Autofluorescence lifetime imaging indicates that infected host cells become more oxidized and have an increased proportion of bound NAD(P)H compared to uninfected controls. Over time, infected cells also show decreases in levels of intracellular glucose and lactate, increases in oxygen consumption, and variability in ROS production. We further examined changes associated with the pre-invasion "kiss and spit" process using autofluorescence lifetime imaging, which also showed a more oxidized host cell with an increased proportion of bound NAD(P)H over 48 hours compared to uninfected controls, suggesting that metabolic changes in host cells are induced by T. gondii kiss and spit even without invasion.IMPORTANCEThis study sheds light on previously unexplored changes in host cell metabolism induced by T. gondii infection using noninvasive, label-free autofluorescence imaging. In this study, we use optical metabolic imaging (OMI) to measure the optical redox ratio (ORR) in conjunction with fluorescence lifetime imaging microscopy (FLIM) to noninvasively monitor single host cell response to T. gondii infection over 48 hours. Collectively, our results affirm the value of using autofluorescence lifetime imaging to noninvasively monitor metabolic changes in host cells over the time course of a microbial infection. Understanding this metabolic relationship between the host cell and the parasite could uncover new treatment and prevention options for T. gondii infections worldwide., Competing Interests: The authors declare no conflict of interest.

Antunes et al. successfully grew cat-restricted stages of Toxoplasma gondii in cell culture by targeting parasite epigenetics and transcription factors. The highlight of this report is how efficiently parasites convert to these pre-sexual stages. Their work is an important step toward achieving feline-free recapitulation of the T. gondii sexual cycle., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Protocols for characterizing taxonomic assemblages by deep sequencing of short DNA barcode regions (metabarcoding) have revolutionized our understanding of microbial communities and are standardized for bacteria, archaea, and fungi. Unfortunately, comparable methods for host-associated eukaryotes have lagged due to technical challenges. Despite 54 published studies, issues remain with primer complementarity, off-target amplification, and lack of external validation. Here, we present VESPA (Vertebrate Eukaryotic endoSymbiont and Parasite Analysis) primers and optimized metabarcoding protocol for host-associated eukaryotic community analysis. Using in silico prediction, panel PCR, engineered mock community standards, and clinical samples, we demonstrate VESPA to be more effective at resolving host-associated eukaryotic assemblages than previously published methods and to minimize off-target amplification. When applied to human and non-human primate samples, VESPA enables reconstruction of host-associated eukaryotic endosymbiont communities more accurately and at finer taxonomic resolution than microscopy. VESPA has the potential to advance basic and translational science on vertebrate eukaryotic endosymbiont communities, similar to achievements made for bacterial, archaeal, and fungal microbiomes., (© 2024. The Author(s).)

During an immune response, macrophages systematically rewire their metabolism in specific ways to support their diversve functions. However, current knowledge of macrophage metabolism is largely concentrated on central carbon metabolism. Using multi-omics analysis, we identified nucleotide metabolism as one of the most significantly rewired pathways upon classical activation. Further isotopic tracing studies revealed several major changes underlying the substantial metabolomic alterations: 1) de novo synthesis of both purines and pyrimidines is shut down at several specific steps; 2) nucleotide degradation activity to nitrogenous bases is increased but complete oxidation of bases is reduced, causing a great accumulation of nucleosides and bases; and 3) cells gradually switch to primarily relying on salvaging the nucleosides and bases for maintaining most nucleotide pools. Mechanistically, the inhibition of purine nucleotide de novo synthesis is mainly caused by nitric oxide (NO)-driven inhibition of the IMP synthesis enzyme ATIC, with NO-independent transcriptional downregulation of purine synthesis genes augmenting the effect. The inhibition of pyrimidine nucleotide de novo synthesis is driven by NO-driven inhibition of CTP synthetase (CTPS) and transcriptional downregulation of thymidylate synthase (TYMS). For the rewiring of degradation, purine nucleoside phosphorylase (PNP) and uridine phosphorylase (UPP) are transcriptionally upregulated, increasing nucleoside degradation activity. However, complete degradation of purine bases by xanthine oxidoreductase (XOR) is inhibited by NO, diverting flux into nucleotide salvage. Inhibiting the activation-induced switch from nucleotide de novo synthesis to salvage by knocking out the purine salvage enzyme hypoxanthine-guanine phosporibosyl transferase ( Hprt ) significantly alters the expression of genes important for activated macrophage functions, suppresses macrophage migration, and increases pyroptosis. Furthermore, knocking out Hprt or Xor increases proliferation of the intracellular parasite Toxoplasma gondii in macrophages. Together, these studies comprehensively reveal the characteristics, the key regulatory mechanisms, and the functional importance of the dynamic rewiring of nucleotide metabolism in classically activated macrophages., Competing Interests: Conflict of Interest The authors declare no competing interest.

Importance: Lipoxygenases (LOXs) are enzymes that catalyze the deoxygenation of polyunsaturated fatty acids such as linoleic and arachidonic acid. These modifications create signaling molecules that are best characterized for modulating the immune response. Deletion of the first lipoxygenase-like enzyme characterized for Toxoplasma gondii (TgLOXL1) generated a less virulent strain, and infected mice showed a decreased immune response. This virulence defect was dependent on the mouse cytokine interferon gamma IFNγ. TgLOXL1 changes location from inside the parasite in tissue culture conditions to vesicular structures within the host immune cells during mouse infection. These results suggest that TgLOXL1 plays a role in the modification of the host immune response in mice., Competing Interests: The authors declare no conflict of interest.

Toxoplasma gondii , the causative agent of toxoplasmosis, is an obligate intracellular parasite that infects warm-blooded vertebrates across the world. In humans, seropositivity rates of T. gondii range from 10% to 90%. Despite its prevalence, few studies address how T. gondii infection changes the metabolism of host cells. Here, we investigate how T. gondii manipulates the host cell metabolic environment by monitoring metabolic response over time using non-invasive autofluorescence lifetime imaging of single cells, seahorse metabolic flux analysis, reactive oxygen species (ROS) production, and metabolomics. Autofluorescence lifetime imaging indicates that infected host cells become more oxidized and have an increased proportion of bound NAD(P)H with infection. These findings are consistent with changes in mitochondrial and glycolytic function, decrease of intracellular glucose, fluctuations in lactate and ROS production in infected cells over time. We also examined changes associated with the pre-invasion "kiss and spit" process using autofluorescence lifetime imaging, which similarly showed a more oxidized host cell with an increased proportion of bound NAD(P)H over 48 hours. Glucose metabolic flux analysis indicated that these changes are driven by NADH and NADP+ in T. gondii infection. In sum, metabolic changes in host cells with T. gondii infection were similar during full infection, and kiss and spit. Autofluorescence lifetime imaging can non-invasively monitor metabolic changes in host cells over a microbial infection time-course., Competing Interests: CONFLICTS OF INTEREST The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

There are several Entamoeba species that colonize humans, but only Entamoeba histolytica causes severe disease. E. histolytica is transmitted through the fecal-oral route to colonize the intestinal tract of 50 million people worldwide. The current mouse model to study E. histolytica intestinal infection directly delivers the parasite into the surgically exposed cecum, which circumvents the natural route of infection. To develop a fecal-oral mouse model, we screened our vivarium for a natural murine Entamoeba colonizer via a pan- Entamoeba PCR targeting the 18S ribosomal gene. We determined that C57BL/6 mice were chronically colonized by Entamoeba muris. This amoeba is closely related to E. histolytica, as determined by 18S sequencing and cross-reactivity with an E. histolytica-specific antibody. In contrast, outbred Swiss Webster (SW) mice were not chronically colonized by E. muris. We orally challenged SW mice with 1 × 10 5 E. muris cysts and discovered they were susceptible to infection, with peak cyst shedding occurring between 5 and 7 days postinfection. Most infected SW mice did not lose weight significantly but trended toward decreased weight gain throughout the experiment compared to mock-infected controls. Infected mice treated with paromomycin, an antibiotic used against noninvasive intestinal disease, do not become colonized by E. muris . Within the intestinal tract, E. muris localizes exclusively to the cecum and colon. Purified E. muris cysts treated with bovine bile in vitro excyst into mobile, pretrophozoite stages. Overall, this work describes a novel fecal-oral mouse model for the important global pathogen E. histolytica. IMPORTANCE Infection with parasites from the Entamoeba genus are significantly underreported causes of diarrheal disease that disproportionally impact tropical regions. There are several species of Entamoeba that infect humans to cause a range of symptoms from asymptomatic colonization of the intestinal tract to invasive disease with dissemination. All Entamoeba species are spread via the fecal-oral route in contaminated food and water. Studying the life cycle of Entamoeba , from host colonization to infectious fecal cyst production, can provide targets for vaccine and drug development. Because there is not an oral challenge rodent model, we screened for a mouse Entamoeba species and identified Entamoeba muris as a natural colonizer. We determine the peak of infection after an oral challenge, the efficacy of paromomycin treatment, the intestinal tract localization, and the cues that trigger excystation. This oral infection mouse model will be valuable for the development of novel therapeutic options for Entamoeba infections.

Parasites belonging to the Apicomplexa phylum are among the most successful pathogens known in nature. They can infect a wide range of hosts, often remain undetected by the immune system, and cause acute and chronic illness. In this phylum, we can find parasites of human and veterinary health relevance, such as Toxoplasma , Plasmodium , Cryptosporidium , and Eimeria . There are still many unknowns about the biology of these pathogens due to the ethical and practical issues of performing research in their natural hosts. Animal models are often difficult or nonexistent, and as a result, there are apicomplexan life cycle stages that have not been studied. One recent alternative has been the use of three-dimensional (3D) systems such as organoids, 3D scaffolds with different matrices, microfluidic devices, organs-on-a-chip, and other tissue culture models. These 3D systems have facilitated and expanded the research of apicomplexans, allowing us to explore life stages that were previously out of reach and experimental procedures that were practically impossible to perform in animal models. Human- and animal-derived 3D systems can be obtained from different organs, allowing us to model host-pathogen interactions for diagnostic methods and vaccine development, drug testing, exploratory biology, and other applications. In this review, we summarize the most recent advances in the use of 3D systems applied to apicomplexans. We show the wide array of strategies that have been successfully used so far and apply them to explore other organisms that have been less studied.

Protozoan parasites that infect humans are widespread and lead to varied clinical manifestations, including life-threatening illnesses in immunocompromised individuals. Animal models have provided insight into innate immunity against parasitic infections; however, species-specific differences and complexity of innate immune responses make translation to humans challenging. Thus, there is a need for in vitro systems that can elucidate mechanisms of immune control and parasite dissemination. We have developed a human microphysiological system of intestinal tissue to evaluate parasite-immune-specific interactions during infection, which integrates primary intestinal epithelial cells and immune cells to investigate the role of innate immune cells during epithelial infection by the protozoan parasite, Toxoplasma gondii , which affects billions of people worldwide. Our data indicate that epithelial infection by parasites stimulates a broad range of effector functions in neutrophils and natural killer cell-mediated cytokine production that play immunomodulatory roles, demonstrating the potential of our system for advancing the study of human-parasite interactions.

Animals with a chronic infection of the parasite Toxoplasma gondii are protected against lethal secondary infection with other pathogens. Our group previously determined that soluble T. gondii antigens (STAg) can mimic this protection and be used as a treatment against several lethal pathogens. Because treatments are limited for the parasite Cryptosporidium parvum, we tested STAg as a C. parvum therapeutic. We determined that STAg treatment reduced C. parvum Iowa II oocyst shedding in gamma interferon knockout (IFN-γ-KO) mice. Murine intestinal sections were then sequenced to define the IFN-γ-independent transcriptomic response to C. parvum infection. Gene Ontology and transcript abundance comparisons showed host immune response and metabolism changes. Transcripts for type I interferon-responsive genes were more abundant in C. parvum-infected mice treated with STAg. Comparisons between phosphate-buffered saline (PBS) and STAg treatments showed no significant differences in C. parvum gene expression. C. parvum transcript abundance was highest in the ileum and mucin-like glycoproteins and the GDP-fucose transporter were among the most abundant. These results will assist the field in determining both host- and parasite-directed future therapeutic targets.

The symbiont-associated (SA) environmental package is a new extension to the minimum information about any (x) sequence (MIxS) standards, established by the Parasite Microbiome Project (PMP) consortium, in collaboration with the Genomics Standard Consortium. The SA was built upon the host-associated MIxS standard, but reflects the nestedness of symbiont-associated microbiota within and across host-symbiont-microbe interactions. This package is designed to facilitate the collection and reporting of a broad range of metadata information that apply to symbionts such as life history traits, association with one or multiple host organisms, or the nature of host-symbiont interactions along the mutualism-parasitism continuum. To better reflect the inherent nestedness of all biological systems, we present a novel feature that allows users to co-localize samples, to nest a package within another package, and to identify replicates. Adoption of the MIxS-SA and of the new terms will facilitate reports of complex sampling design from a myriad of environments., (© 2022. The Author(s).)

Competing Interests: The authors have declared that no competing interests exist.

Pancreatic ductal adenocarcinoma is the fourth leading cause of cancer-related death in the United States, with few effective treatments available and only 10% of those diagnosed surviving 5 years. Although immunotherapeutics is a growing field of study in cancer biology, there has been little progress in its use for the treatment of pancreatic cancer. Pancreatic cancer is considered a nonimmunogenic tumor because the tumor microenvironment does not easily allow for the immune system, even when stimulated, to attack the cancer. Infection with the protozoan parasite Toxoplasma gondii has been shown to enhance the immune response to clear cancer tumors. A subset of T. gondii proteins called soluble Toxoplasma antigen (STAg) contains an immunodominant protein called profilin. Both STAg and profilin have been shown to stimulate an immune response that reduces viral, bacterial, and parasitic burdens. Here, we use STAg and profilin to treat pancreatic cancer in a KPC mouse-derived allograft murine model. These mice exhibit pancreatic cancer with both Kras and P53 mutations as subcutaneous tumors. Pancreatic cancer tumors in C57BL/6J mice with a wild-type background showed a significant response to treatment with either profilin or STAg, exhibiting a decrease in tumor volume accompanied by an influx of CD4 + and CD8 + T cells into the tumors. Both IFN-γ -/- mice and Batf3 -/- mice, which lack conventional dendritic cells, failed to show significant decreases in tumor volumes when treated. These results indicate that gamma interferon (IFN-γ) and dendritic cells may play critical roles in the immune response necessary to treat pancreatic cancer.

Toxoplasma gondii infection activates pattern recognition receptor (PRR) pathways that drive innate inflammatory responses to control infection. Necroptosis is a proinflammatory cell death pathway apart from the innate immune response that has evolved to control pathogenic infection. In this study, we further defined the role of Z-DNA binding protein 1 (ZBP1) as a PRR and assessed its contribution to necroptosis as a host protection mechanism to T. gondii infection. We found that ZBP1 does not induce proinflammatory necroptosis cell death, and ZBP1 null mice have reduced survival after oral T. gondii infection. In contrast, mice deleted in receptor-interacting serine/threonine-protein kinase 3 (RIPK3 -/- ), a central mediator of necroptosis, have significantly improved survival after oral T. gondii infection without a reduction in parasite burden. The physiological consequences of RIPK3 activity did not show any differences in intestine villus immunopathology, but RIPK3 -/- mice showed higher immune cell infiltration and edema in the lamina propria. The contribution of necroptosis to host survival was clarified with mixed-lineage kinase domain-like pseudokinase null (MLKL -/- ) mice. We found MLKL -/- mice succumbed to oral T. gondii infection the same as wild-type mice, indicating necroptosis-independent RIPK3 activity impacts host survival. These results provide new insights on the impacts of proinflammatory cell death pathways as a mechanism of host defense to oral T. gondii infection., (Copyright © 2021 Cervantes et al.)

Toxoplasma gondii and Eimeria spp. are widely prevalent Coccidian parasites that undergo sexual reproduction during their life cycle. T. gondii can infect any warm-blooded animal in its asexual cycle; however, its sexual cycle is restricted to felines. Eimeria spp. are usually restricted to one host species, and their whole life cycle is completed within this same host. The literature reviewed in this article comprises the recent findings regarding the unique biology of the sexual development of T. gondii and Eimeria spp. The molecular basis of sex in these pathogens has been significantly unraveled by new findings in parasite differentiation along with transcriptional analysis of T. gondii and Eimeria spp. pre-sexual and sexual stages. Focusing on the metabolic networks, analysis of these transcriptome datasets shows enrichment for several different metabolic pathways. Transcripts for glycolysis enzymes are consistently more abundant in T. gondii cat infection stages than the asexual tachyzoite stage and Eimeria spp. merozoite and gamete stages compared to sporozoites. Recent breakthroughs in host-pathogen interaction and host restriction have significantly expanded the understating of the unique biology of these pathogens. This review aims to critically explore advances in the sexual cycle of Coccidia parasites with the ultimate goal of comparing and analyzing the sexual cycle of Eimeria spp. and T. gondii ., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2020 Martorelli Di Genova and Knoll.)

Interpreting other people's intentions during communication represents a remarkable challenge for children. Although many studies have examined children's understanding of, for example, sarcasm, less is known about their interpretation . Using realistic audiovisual scenes, we invited 124 children between 8 and 12 years old to watch video clips of young adults using different speaker intentions. After watching each video clip, children answered questions about the characters and their beliefs, and the perceived friendliness of the speaker. Children's responses reveal age and gender differences in the ability to interpret speaker belief and social intentions, especially for scenarios conveying teasing and prosocial lies. We found that the ability to infer speaker belief of prosocial lies and to interpret social intentions increases with age. Our results suggest that children at the age of 8 years already show adult-like abilities to understand literal statements, whereas the ability to infer specific social intentions, such as teasing and prosocial lies, is still developing between the age of 8 and 12 years. Moreover, girls performed better in classifying prosocial lies and sarcasm as insincere than boys. The outcomes expand our understanding of how children observe speaker intentions and suggest further research into the development of teasing and prosocial lie interpretation.

New treatments for the diseases caused by apicomplexans are needed. Recently, we determined that tartrolon E (trtE), a secondary metabolite derived from a shipworm symbiotic bacterium, has broad-spectrum anti-apicomplexan parasite activity. TrtE inhibits apicomplexans at nM concentrations in vitro, including Cryptosporidium parvum, Toxoplasma gondii, Sarcocystis neurona, Plasmodium falciparum, Babesia spp. and Theileria equi. To investigate the mechanism of action of trtE against apicomplexan parasites, we examined changes in the transcriptome of trtE-treated T. gondii parasites. RNA-Seq data revealed that the gene, TGGT1_272370, which is broadly conserved in the coccidia, is significantly upregulated within 4 h of treatment. Using bioinformatics and proteome data available on ToxoDB, we determined that the protein product of this tartrolon E responsive gene (trg) has multiple transmembrane domains, a phosphorylation site, and localizes to the plasma membrane. Deletion of trg in a luciferase-expressing T. gondii strain by CRISPR/Cas9 resulted in a 68% increase in parasite resistance to trtE treatment, supporting a role for the trg protein product in the response of T. gondii to trtE treatment. Trg is conserved in the coccidia, but not in more distantly related apicomplexans, indicating that this response to trtE may be unique to the coccidians, and other mechanisms may be operating in other trtE-sensitive apicomplexans. Uncovering the mechanisms by which trtE inhibits apicomplexans may identify shared pathways critical to apicomplexan parasite survival and advance the search for new treatments., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Competing Interests: The authors have declared that no competing interests exist.

Toxoplasma gondii causes a prevalent human infection for which only the acute stage has an FDA-approved therapy. To find inhibitors of both the acute stage parasites and the persistent cyst stage that causes a chronic infection, we repurposed a compound library containing known inhibitors of parasitic hexokinase, the first step in the glycolysis pathway, along with a larger collection of new structural derivatives. The focused screen of 22 compounds showed a 77% hit rate (>50% multistage inhibition) and revealed a series of aminobenzamide-linked picolinic acids with submicromolar potency against both T. gondii parasite forms. Picolinic acid 23 , designed from an antiparasitic benzamidobenzoic acid class with challenging ADME properties, showed 60-fold-enhanced solubility, a moderate LogD 7.4 , and a 30% improvement in microsomal stability. Furthermore, isotopically labeled glucose tracing revealed that picolinic acid 23 does not function by hexokinase inhibition. Thus, we report a new probe scaffold to interrogate dual-stage inhibition of T. gondii ., Competing Interests: The authors declare no competing financial interest., (© 2020 American Chemical Society.)

Toxoplasma gondii is an obligate intracellular parasite that can invade any nucleated cell of any warm-blooded animal. In a previous screen to identify virulence determinants, disruption of gene TgME49_305140 generated a T. gondii mutant that could not establish a chronic infection in mice. The protein product of TgME49_305140, here named TgPL3, is a 277 kDa protein with a patatin-like phospholipase (PLP) domain and a microtubule binding domain. Antibodies generated against TgPL3 show that it is localized to the apical cap. Using a rapid selection FACS-based CRISPR/Cas-9 method, a TgPL3 deletion strain (ΔTgPL3) was generated. ΔTgPL3 parasites have defects in host cell invasion, which may be caused by reduced rhoptry secretion. We generated complementation clones with either wild type TgPL3 or an active site mutation in the PLP domain by converting the catalytic serine to an alanine, ΔTgPL3::TgPL3S1409A (S1409A). Complementation of ΔTgPL3 with wild type TgPL3 restored all phenotypes, while S1409A did not, suggesting that phospholipase activity is necessary for these phenotypes. ΔTgPL3 and S1409A parasites are also virtually avirulent in vivo but induce a robust antibody response. Vaccination with ΔTgPL3 and S1409A parasites protected mice against subsequent challenge with a lethal dose of Type I T. gondii parasites, making ΔTgPL3 a compelling vaccine candidate. These results demonstrate that TgPL3 has a role in rhoptry secretion, host cell invasion and survival of T. gondii during acute mouse infection., Competing Interests: PJR is currently employed by the Stratatech Corporation. Her affiliation with this company did not affect this study in any way. This affiliation does not alter our adherence to all PLOS Pathogens policies on sharing data and materials. The other authors have declared that no competing interests exist.

Studies have shown that adolescents are more likely than adults to take risks in the presence of peers than when alone, and that young adolescents' risk perception is more influenced by other teenagers than by adults. The current fMRI study investigated the effect of social influence on risk perception in female adolescents (aged 12-14) and adults (aged 23-29). Participants rated the riskiness of everyday situations and were then informed about the (alleged) risk ratings of a social influence group (teenagers or adults), before rating each situation again. The results showed that adolescents adjusted their ratings to conform with others more than adults did, and both age groups were influenced more by adults than by teenagers. When there was a conflict between the participants' own risk ratings and the ratings of the social influence group, activation was increased in the posterior medial frontal cortex, dorsal cingulate cortex and inferior frontal gyrus in both age groups. In addition, there was greater activation during no-conflict situations in the right middle frontal gyrus and bilateral parietal cortex in adults compared with adolescents. These results suggest that there are behavioral and neural differences between adolescents and adults in conflict and no-conflict social situations.

The obligate intracellular parasite Toxoplasma gondii is auxotrophic for several key metabolites and must scavenge these from the host. It is unclear how T. gondii manipulates host metabolism to support its overall growth rate and non-essential metabolites. To investigate this question, we measured changes in the joint host-parasite metabolome over a time course of infection. Host and parasite transcriptomes were simultaneously generated to determine potential changes in expression of metabolic enzymes. T. gondii infection changed metabolite abundance in multiple metabolic pathways, including the tricarboxylic acid cycle, the pentose phosphate pathway, glycolysis, amino acid synthesis, and nucleotide metabolism. Our analysis indicated that changes in some pathways, such as the tricarboxylic acid cycle, were mirrored by changes in parasite transcription, while changes in others, like the pentose phosphate pathway, were paired with changes in both the host and parasite transcriptomes. Further experiments led to the discovery of a T. gondii enzyme, sedoheptulose bisphosphatase, which funnels carbon from glycolysis into the pentose phosphate pathway through an energetically driven dephosphorylation reaction. This additional route for ribose synthesis appears to resolve the conflict between the T. gondii tricarboxylic acid cycle and pentose phosphate pathway, which are both NADP+ dependent. Sedoheptulose bisphosphatase represents a novel step in T. gondii central carbon metabolism that allows T. gondii to energetically-drive ribose synthesis without using NADP+., Competing Interests: The authors have declared that no competing interests exist.

Eimeria species are intestinal protozoan parasites that cause lack of production, malabsorption and mortality in floor raised chickens. Administering an oral antibody to interleukin 10 (aIL-10) reduces the symptoms of coccidiosis in broilers, indicating interleukin 10 (IL-10) is key to Eimeria pathology. IL-10 is an anti-inflammatory cytokine and acts as a stand down signal to reduce inflammation and host pathology during disease. Related protozoan parasites exploit IL-10 to reduce pathogen-damaging host inflammatory responses. We hypothesize that IL-10 is increased during Eimeria infection through an unknown host-pathogen interaction, and by feeding aIL-10 to neutralize excess IL-10 the bird is allowed to mount an effective immune response to Eimeria. To determine the effects of aIL-10 during the intestinal immune response, intestinal pathology and the relationship between IL-10, interferon gamma (IFNγ) and Eimeria infection were evaluated in this study. In both experiments, broilers were administered either a 10x dose of Advent® Eimeria vaccine or saline. Duodenum, jejunum and cecum samples were collected, processed, stained and examined under a microscope. Evaluation of intestinal histomorphology during aIL-10 administration showed minimal differences in birds fed aIL-10 during infection compared to animals fed a control antibody during Eimeria infection. To further evaluate aIL-10's positive effect during infection, immunofluorescent histochemistry was performed on chicken intestines days 3-7 post Eimeria infection for IL-10 and IFNγ presence in intestinal mucosa in control and infected birds, in regions with and without visible Eimeria burden. IL-10 and IFNγ had significant changes between days 4.5-7 post-infection in birds fed aIL-10 compared to animals fed a control antibody. Overall we found that the duodenum had increased IL-10 presence and increased IFNγ presence, and the jejunum and cecum had decreased IL-10 presence and decreased IFNγ presence. These differences in spatial regulation of IL-10 and IFNγ may indicate Eimeria species induce slightly different cytokine responses., (Published by Elsevier B.V.)

Background: The protozoan pathogen Toxoplasma gondii has the unique ability to develop a chronic infection in the brain of its host by transitioning from the fast growing tachyzoite morphology to latent bradyzoite morphology. A hallmark of the bradyzoite is the development of neuronal cysts that are resilient against host immune response and current therapeutics. The bradyzoite parasites within the cyst have a carbohydrate and protein-rich wall and a slow-replication cycle, allowing them to remain hidden from the host. The intracellular, encysted lifestyle of T. gondii has made them recalcitrant to molecular analysis in vivo., Results: Here, we detail the results from transcriptional and proteomic analyses of bradyzoite-enriched fractions isolated from mouse brains infected with T. gondii over a time course of 21 to 150 days. The enrichment procedure afforded consistent identification of over 2000 parasitic peptides from the mixed-organism sample, representing 366 T. gondii proteins at 28, 90, and 120 day timepoints. Deep sequencing of transcripts expressed during these three timepoints revealed that a subpopulation of genes that are transcriptionally expressed at a high level. Approximately one-third of these transcripts are more enriched during bradyzoite conditions compared to tachyzoites and approximately half are expressed at similar levels during each phase. The T. gondii transcript which increased the most over the course of chronic infection, sporoAMA1, shows stage specific isoform expression of the gene., Conclusions: We have expanded the transcriptional profile of in vivo bradyzoites to 120 days post-infection and provided the first in vivo proteomic profile of T. gondii bradyzoites. The RNA sequencing depth of in vivo bradyzoite T. gondii was over 250-fold greater than previous reports and allowed us to identify low level transcripts and a novel bradyzoite-specific isoform of sporoAMA1.

Existing non-verbal ability tests are typically protected by copyright, preventing them from being freely adapted or computerized. Working towards an open science framework, we provide 80 novel, open-access abstract reasoning items, an online implementation and item-level data from 659 participants aged between 11 and 33 years: the matrix reasoning item bank (MaRs-IB). Each MaRs-IB item consists of an incomplete matrix containing abstract shapes. Participants complete the matrices by identifying relationships between the shapes. Our data demonstrate age differences in non-verbal reasoning accuracy, which increased during adolescence and stabilized in early adulthood. There was a slight linear increase in response times with age, resulting in a peak in efficiency (i.e. a measure combining speed and accuracy) in late adolescence. Overall, the data suggest that the MaRs-IB is sensitive to developmental differences in reasoning accuracy. Further psychometric validation is recommended., Competing Interests: The authors declare no conflict of interest., (© 2019 The Authors.)

Competing Interests: The authors have declared that no competing interests exist.

Coccidiosis is a major gastrointestinal disease caused by several Eimeria species in floor raised chickens. Feeding an antibody to interleukin 10 (aIL-10) ameliorates the negative symptoms of coccidiosis in broilers, i.e., lack of weight gain, decreased feed conversion, and mortality. IL-10 signals by forming a ligand-receptor complex with IL-10 Receptor 1 (IL-10 R1) and IL-10 Receptor 2 (IL-10 R2). In this study, we hypothesize oral antibodies to the IL-10 receptors will neutralize the IL-10 signaling pathway equal to or better than aIL-10 to act as an oral anti-coccidiosis immunotherapy. A total of 5 sequential feed trials, set up as a 4 (diet antibody) × 2 (Eimeria challenge) factorial design, tested oral egg yolk antibodies to a total of 6 IL-10 R1 epitopes and 3 IL-10 R2 epitopes compared to a control antibody diet. A total of 10 pens of 5 chicks/pen/diet antibody/Eimeria challenge were housed for 21 d. On day 3 of age, chicks were either infected or not infected with a 10× dose of an Eimeria vaccine containing Eimeria acervulina, Eimeria tenella, and Eimeria maxima. Pen feed consumption and mean body weights were assessed weekly (d1, d7, d14, and d21); fecal oocyst shedding was assessed on day 10. Data were analyzed using a 2-way ANOVA. No significant interaction on chick weight was observed in chicks fed IL-10 R1 antibodies compared to chicks fed the control antibody was observed. In studies evaluating aIL-10 R2 oral antibodies, infected chicks fed aIL-10 R2: epitope 1 overcame the negative effects of Eimeria infection and had similar 21-d body weight to uninfected chicks (P4 = 0.07). We hypothesized that feeding oral antibodies to the IL-10 receptors would result in equivalent anti-coccidial benefits to aIL-10. However, none of the 6 antibodies to IL-10 R1 epitopes yielded any benefits during Eimeria infection compared to controls. A total of 2 oral antibodies to IL-10 R2 showed promising results equivalent to the aIL-10 immunotherapeutic. Immunofluorescence staining shows that the IL-10R2 significantly increases in abundance in response to Eimeria infection, whereas IL-10R1 does not., (© 2019 Poultry Science Association Inc.)

Many eukaryotic microbes have complex life cycles that include both sexual and asexual phases with strict species specificity. Whereas the asexual cycle of the protistan parasite Toxoplasma gondii can occur in any warm-blooded mammal, the sexual cycle is restricted to the feline intestine. The molecular determinants that identify cats as the definitive host for T. gondii are unknown. Here, we defined the mechanism of species specificity for T. gondii sexual development and break the species barrier to allow the sexual cycle to occur in mice. We determined that T. gondii sexual development occurs when cultured feline intestinal epithelial cells are supplemented with linoleic acid. Felines are the only mammals that lack delta-6-desaturase activity in their intestines, which is required for linoleic acid metabolism, resulting in systemic excess of linoleic acid. We found that inhibition of murine delta-6-desaturase and supplementation of their diet with linoleic acid allowed T. gondii sexual development in mice. This mechanism of species specificity is the first defined for a parasite sexual cycle. This work highlights how host diet and metabolism shape coevolution with microbes. The key to unlocking the species boundaries for other eukaryotic microbes may also rely on the lipid composition of their environments as we see increasing evidence for the importance of host lipid metabolism during parasitic lifecycles. Pregnant women are advised against handling cat litter, as maternal infection with T. gondii can be transmitted to the fetus with potentially lethal outcomes. Knowing the molecular components that create a conducive environment for T. gondii sexual reproduction will allow for development of therapeutics that prevent shedding of T. gondii parasites. Finally, given the current reliance on companion animals to study T. gondii sexual development, this work will allow the T. gondii field to use of alternative models in future studies., Competing Interests: The authors have declared that no competing interests exist.

The long-term host effects caused by the protozoan parasite Toxoplasma gondii are poorly understood. High-throughput RNA sequencing analysis previously determined that the host response in the brain was greater and more complex at 28 days than at 10 days postinfection. Here, we analyzed the host transcriptional profile of age- and sex-matched mice during very early (21 days), early (28 days), mid (3 months), and late (6 months) chronic infection. We found that a majority of the host genes which increase in abundance at day 21 postinfection are still increased at 6 months postinfection for both male and female mice. While most of the differentially expressed genes were similar between sexes, females had far fewer genes that were significantly less abundant, which may have led to the slightly increased cyst burden in males. Transcripts for C-X-C motif chemokine ligand 13 and a C-C motif chemokine receptor 2 (CCR2) were significantly higher in females than in males during infection. As T. gondii chronic infection and profilin (PRF) confer resistance to Listeria monocytogenes infection in a CCR2-dependent manner, the differences in CCR2 expression led us to retest the protection of PRF in both sexes. Male mice were nearly as effective as female mice at reducing the bacterial burden either with a chronic infection or when treated with PRF. These data show that most of the host genes differentially expressed in response to T. gondii infection are similar between males and females. While differences in transcript abundance exist between the sexes, the infection phenotypes tested here did not show significant differences., (Copyright © 2019 American Society for Microbiology.)

Social influence occurs when an individual's thoughts or behaviours are affected by other people. There are significant age effects on susceptibility to social influence, typically a decline from childhood to adulthood. Most research has focused on negative aspects of social influence, such as peer influence on risky behaviour, particularly in adolescence. The current study investigated the impact of social influence on the reporting of prosocial behaviour (any act intended to help another person). In this study, 755 participants aged 8-59 completed a computerized task in which they rated how likely they would be to engage in a prosocial behaviour. Afterwards, they were told the average rating (in fact fictitious) that other participants had given to the same question, and then were asked to rate the same behaviour again. We found that participants' age affected the extent to which they were influenced by other people: children (8-11 years), young adolescents (12-14 years) and mid-adolescents (15-18 years) all significantly changed their ratings, while young adults (19-25 years) and adults (26-59 years) did not. Across the three youngest age groups, children showed the most susceptibility to prosocial influence, changing their reporting of prosocial behaviour the most. The study provides evidence that younger people's increased susceptibility to social influence can have positive outcomes., (© 2018 The Authors. Developmental Science Published by John Wiley & Sons Ltd.)

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit cyclooxygenase (COX) activity and are commonly used for pain relief and fever reduction. NSAIDs are used following childhood vaccinations and cancer immunotherapies; however, how NSAIDs influence the development of immunity following these therapies is unknown. We hypothesized that NSAIDs would modulate the development of an immune response to Listeria monocytogenes -based immunotherapy. Treatment of mice with the nonspecific COX inhibitor indomethacin impaired the generation of cell-mediated immunity. This phenotype was due to inhibition of the inducible COX-2 enzyme, as treatment with the COX-2-selective inhibitor celecoxib similarly inhibited the development of immunity. In contrast, loss of COX-1 activity improved immunity to L. monocytogenes Impairments in immunity were independent of bacterial burden, dendritic cell costimulation, or innate immune cell infiltrate. Instead, we observed that PGE 2 production following L. monocytogenes is critical for the formation of an Ag-specific CD8 + T cell response. Use of the alternative analgesic acetaminophen did not impair immunity. Taken together, our results suggest that COX-2 is necessary for optimal CD8 + T cell responses to L. monocytogenes , whereas COX-1 is detrimental. Use of pharmacotherapies that spare COX-2 activity and the production of PGE 2 like acetaminophen will be critical for the generation of optimal antitumor responses using L. monocytogenes ., (Copyright © 2018 by The American Association of Immunologists, Inc.)

Emerging lipidomic technologies have enabled researchers to dissect the complex roles of phospholipases in lipid metabolism, cellular signaling and immune regulation. Host phospholipase products are involved in stimulating and resolving the inflammatory response to pathogens. While many pathogen-derived phospholipases also manipulate the immune response, they have recently been shown to be involved in lipid remodeling and scavenging during replication. Animal and plant hosts as well as many pathogens contain a family of patatin-like phospholipases, which have been shown to have phospholipase A 2 activity. Proteins containing patatin-like phospholipase domains have been identified in protozoan parasites within the Apicomplexa phylum. These parasites are the causative agents of some of the most widespread human diseases. Malaria, caused by Plasmodium spp., kills nearly half a million people worldwide each year. Toxoplasma and Cryptosporidium infect millions of people each year with lethal consequences in immunocompromised populations. Parasite-derived patatin-like phospholipases are likely effective drug targets and progress in the tools available to the Apicomplexan field will allow for a closer look at the interplay of lipid metabolism and immune regulation during host infection., (© 2017 John Wiley & Sons Ltd.)

Adolescents are particularly susceptible to social influence. Here, we investigated the effect of social influence on risk perception in 590 participants aged eight to fifty-nine-years tested in the United Kingdom. Participants rated the riskiness of everyday situations, were then informed about the rating of these situations from a (fictitious) social-influence group consisting of teenagers or adults, and then re-evaluated the situation. Our first aim was to attempt to replicate our previous finding that young adolescents are influenced more by teenagers than by adults. Second, we investigated the social-influence effect when the social-influence group's rating was more, or less, risky than the participants' own risk rating. Younger participants were more strongly influenced by teenagers than by adults, but only when teenagers rated a situation as more risky than did participants. This suggests that stereotypical characteristics of the social-influence group - risk-prone teenagers - interact with social influence on risk perception., (Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The Toxoplasma gondii cyst stage is resistant to drug therapy. To identify potential targets for new therapeutics, we screened insertional mutants of T. gondii for a reduced ability to form cysts in the brains of mice. In one of these mutants, named 38C3, the mutagenesis plasmid inserted into the mRNA of a protein that is highly conserved in microbes but is not present in humans. The mutation in 38C3 causes reduced brain cyst production during chronic infection, but does not affect acute virulence, so the disrupted gene and protein are called T. gondii Brain Colonization Protein 1 (TgBCP1). TgBCP1 has three potential in frame start codons that produce 51, 33 or 25 kDa proteins. In rapidly replicating tachyzoites, translation initiates at the third methionine, producing the 25 kDa form that is conserved in many bacteria and protozoans. Brain cysts exclusively express the 51 kDa form of TgBCP1, which is secreted from the parasites and localizes to the cyst wall. Only expression of the long form of TgBCP1 restored cyst formation in the 38C3 mutant. TgBCP1 is essential for cyst formation and is the first example of a developmental regulation in translation initiation site preference for a T. gondii protein., (© 2016 John Wiley & Sons Ltd.)

In the current study, we investigated windows for enhanced learning of cognitive skills during adolescence. Six hundred thirty-three participants (11-33 years old) were divided into four age groups, and each participant was randomly allocated to one of three training groups. Each training group completed up to 20 days of online training in numerosity discrimination (i.e., discriminating small from large numbers of objects), relational reasoning (i.e., detecting abstract relationships between groups of items), or face perception (i.e., identifying differences in faces). Training yielded some improvement in performance on the numerosity-discrimination task, but only in older adolescents or adults. In contrast, training in relational reasoning improved performance on that task in all age groups, but training benefits were greater for people in late adolescence and adulthood than for people earlier in adolescence. Training did not increase performance on the face-perception task for any age group. Our findings suggest that for certain cognitive skills, training during late adolescence and adulthood yields greater improvement than training earlier in adolescence, which highlights the relevance of this late developmental stage for education., Competing Interests: The authors declared that they had no conflicts of interest with respect to their authorship or the publication of this article.

Most studies on the development of face cognition abilities have focussed on childhood, with early maturation accounts contending that face cognition abilities are mature by 3-5 years. Late maturation accounts, in contrast, propose that some aspects of face cognition are not mature until at least 10 years. Here, we measured face memory and face perception, two core face cognition abilities, in 661 participants (397 females) in four age groups (younger adolescents (11.27-13.38 years); mid-adolescents (13.39-15.89 years); older adolescents (15.90-18.00 years); and adults (18.01-33.15 years)) while controlling for differences in general cognitive ability. We showed that both face cognition abilities mature relatively late, at around 16 years, with a female advantage in face memory, but not in face perception, both in adolescence and adulthood. Late maturation in the face perception task was driven mainly by protracted development in identity perception, while gaze perception abilities were already comparatively mature in early adolescence. These improvements in the ability to memorize, recognize and perceive faces during adolescence may be related to increasing exploratory behaviour and exposure to novel faces during this period of life.

Intrinsic to Toxoplasma gondii infection is the parasite-induced modulation of the host immune response, which ensures establishment of a chronic lifelong infection. This manipulation of the host immune response allows T. gondii to not only dampen the ability of the host to eliminate the parasite but also trigger parasite differentiation to the slow-growing, encysted bradyzoite form. We previously used RNA sequencing (RNA-seq) to profile the transcriptomes of mice and T. gondii during acute and chronic stages of infection. One of the most abundant host transcripts during acute and chronic infection was Z-DNA binding protein 1 (ZBP1). In this study, we determined that ZBP1 functions to control T. gondii growth. In activated macrophages isolated from ZBP1 deletion (ZBP1(-/-)) mice, T. gondii has an increased rate of replication and a decreased rate of degradation. We also identified a novel function for ZBP1 as a regulator of nitric oxide (NO) production in activated macrophages, even in the absence of T. gondii infection. Upon stimulation, T. gondii-infected ZBP1(-/-) macrophages display increased proinflammatory cytokines compared to wild-type macrophages under the same conditions. These in vitro phenotypes were recapitulated in vivo, with ZBP1(-/-) mice having increased susceptibility to oral challenge, higher cyst burdens during chronic infection, and elevated inflammatory cytokine responses. Taken together, these results highlight a role for ZBP1 in assisting host control of T. gondii infection., (Copyright © 2016, American Society for Microbiology. All Rights Reserved.)

Competing Interests: The authors have declared that no competing interests exist.

Toxoplasma gondii is one of the most common parasitic infections of humans worldwide. Once exposed, humans remain infected with T. gondii for life, and there are no therapeutics capable of eliminating a chronic infection. In the search for novel drug targets, T. gondii is known to contain several unique secretory organelles, one of which is called the rhoptries. Rhoptry organelles contain and secrete numerous proteins with kinase domains, but the roles of most of these kinases during infection remain unknown. In a recent mBio article, B. A. Fox et al. [mBio 7(3):e00193-16, 2016, http://dx.doi.org/10.1128/mBio.00193-16] performed a tour de force deletion analysis of 31 rhoptry kinases and examined their roles in the development of chronic infection. While rhoptry kinase deletion strains that displayed an acute infection defect also showed a reduction in chronic infection cyst burden, two rhoptry kinase deletion strains had decreased cyst burden without any change in acute virulence. These results indicate the necessity of the rhoptry kinases for the establishment and perhaps maintenance of chronic infection. They also highlight the potential of these kinases as drug targets to clear chronic infection or as candidates to generate a nonpersisting vaccine., (Copyright © 2016 Knoll.)

Toxoplasma gondii represents one of the most common parasitic infections in the world. The asexual cycle can occur within any warm-blooded animal, but the sexual cycle is restricted to the feline intestinal epithelium. T. gondii is acquired through consumption of tissue cysts in undercooked meat as well as food and water contaminated with oocysts. Once ingested, it differentiates into a rapidly replicating asexual form and disseminates throughout the body during acute infection. After stimulation of the host immune response, T. gondii differentiates into a slow-growing, asexual cyst form that is the hallmark of chronic infection. One-third of the human population is chronically infected with T. gondii cysts, which can reactivate and are especially dangerous to individuals with reduced immune surveillance. Serious complications can also occur in healthy individuals if infected with certain T. gondii strains or if infection is acquired congenitally. No drugs are available to clear the cyst form during the chronic stages of infection. This therapeutic gap is due in part to an incomplete understanding of both host and pathogen responses during the progression of T. gondii infection. While many individual aspects of T. gondii infection are well understood, viewing the interconnections between host and parasite during acute and chronic infection may lead to better approaches for future treatment. The aim of this review is to provide an overview of what is known and unknown about the complex relationship between the host and parasite during the progression of T. gondii infection, with the ultimate goal of bridging these events., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)