Human impact on the diversity and virulence of the ubiquitous zoonotic parasite Toxoplasma gondii

Tumor microbiota of renal cell carcinoma affects clinical prognosis by influencing the tumor immune microenvironment

Despite reported influences of the intratumoral microbiome on cancer progression, its role in this subtype remains unclear. This study aimed to characterize the microbial landscape and signatures of kidney renal clear cell carcinoma using RNA-Seq data from The Cancer Genome Atlas. Following microbial decontamination, differential microbial analysis was conducted between tumorous and adjacent non-tumorous samples. Compared to non-tumorous samples, tumorous microbiota exhibited reduced α and β diversity and distinct phylum-level communities. Differential microbial analysis between patients exhibiting long and short overall survival revealed ten significant differential microbial genera, with six genera correlating with a positive prognosis (Plasmodium, Babesia, Toxoplasma, Cytobacillus, Alicyclobacillus, Verrucomicrobium) and four with a negative prognosis (Colletotrichum, Leuconostoc, Gluconobacter, and Parabacteroides). Employing Cox regression analysis and support vector machines, a prognosis-related microbiome risk signature was developed, achieving an AUC of 0.809. Based on this risk signature, two microbiome-based subtypes were found to be significantly associated with distinct clinical prognoses and immune microenvironments. These findings were corroborated by significant correlations between prognostic-relevant microorganisms and 30 immune-related differentially expressed genes. Specifically, microbial genera associated with a negative prognosis were linked to a pro-tumor acute inflammatory immune response, whereas genera related to a positive prognosis were associated with an anti-tumor adaptive immune response. In conclusion, microbiome-based subtyping revealed correlations between tumor microbiome, clinical prognosis, and tumor microenvironment, indicating intratumoral microbiota as a promising prognostic biomarker for kidney renal clear cell carcinoma.

REIV-TOXO Project: Results from a Spanish cohort of congenital toxoplasmosis (2015-2022). The beneficial effects of prenatal treatment on clinical outcomes of infected newborns

BACKGROUND

Some regions of Spain are withdrawing their pregnancy screening program for congenital toxoplasmosis (CT). The Spanish Research Network of Congenital Toxoplasmosis (REIV-TOXO) was created to describe the current status of CT in Spain. The aims of this study were to describe the epidemiological and clinical characteristics of CT and to evaluate the effect of prenatal treatment on clinical outcomes to inform decision-making policies.

METHODS

Ambispective observational study including CT cases recorded in the REIV-TOXO database that includes 122 hospitals (2015-2022). Inclusion criteria were one or more of the following: positive PCR in maternal amniotic fluid; positive Toxoplasma gondii-specific IgM or IgA antibodies at birth; positive PCR in the placenta, newborn blood, urine or CSF; increase of specific IgG levels during infant follow-up; or specific IgG persistence beyond age 12 months.

FINDINGS

Fifty-six newborns (54 pregnancies) were included. Prenatal screening allowed 92.8% of cases to be identified. The time of maternal infection was well documented in 90.7% of cases, with 61.1% occurring in the third trimester. A total of 66.6% (36/54) pregnant women received antiparasitic treatment: 24/36 spiramycin, 8/36 pyrimethamine, sulfadiazine, and folinic acid, and 4/36 both treatments sequentially. Most cases were asymptomatic at birth (62.5%, 35/56), and 84% (47/56) newborns completed one year of treatment. Median follow-up was 24 months (IQR = 3-72): 14.2% children exhibited new complications, mainly ocular. Newborns born to mothers treated prenatally had four-fold lower risk of CT clinical features at birth (p = 0.03) and six-fold lower risk of further complications during follow-up (p = 0.04) with no treatment-related differences during pregnancy.

CONCLUSIONS

While diagnosis based only on neonatal assessment misses a significant number of CT cases, prenatal screening allows treatment to be started during pregnancy, with better clinical outcomes at birth and during follow-up. REIV-TOXO provides valuable information about CT in Spain, highlighting the need for universal maternal screening.

Functional Characterization of 11 Tentative Microneme Proteins in Type I RH Strain of Toxoplasma gondii Using the CRISPR-Cas9 System

Toxoplasma gondii, a pathogenic apicomplexan parasite, infects approximately one third of the world's population and poses a serious threat to global public health. Microneme proteins (MICs) secreted by the microneme, an apical secretory organelle of T. gondii, play important roles in the invasion, motility, and intracellular survival of T. gondii. In this study, we selected 11 genes of interest (GOIs) of T. gondii, tentative MICs predicted to be localized in micronemes, and we used the CRISPR-Cas9 system to construct epitope tagging strains and gene knockout strains to explore the localization and function of these 11 tentative MICs. Immunofluorescence assay showed that nine tentative MICs (TGME49_243930, TGME49_200270, TGME49_273320, TGME49_287040, TGME49_261710, TGME49_205680, TGME49_304490, TGME49_245485, and TGME49_224620) were localized or partially localized in the microneme, consistent with the prediction. However, TGME49_272380 and TGME49_243790 showed different localizations from the prediction, being localized in the endoplasmic reticulum and the dense granule, respectively. Further functional characterization of the 11 RHΔGOI strains revealed that deletion of these 11 GOIs had no significant effect on plaque formation, intracellular replication, egress, invasion ability, and virulence of T. gondii. Although these 11 GOIs are not essential genes for the growth and virulence of tachyzoites of type I RH strain, they may have potential roles in other developmental stages or other genotypes of T. gondii. Thus, further research should be performed to explore the possible role of the nine mics and the other two GOIs in other life cycle stages and other genotypes of T. gondii.

Human T-cell activation with Toxoplasma gondii antigens loaded in maltodextrin nanoparticles

Toxoplasmosis is the most prevalent parasitic zoonosis worldwide, causing ocular and neurological diseases. No vaccine has been approved for human use. We evaluated the response of peripheral blood mononuclear cells (PBMCs) to a novel construct of Toxoplasma gondii total antigen in maltodextrin nanoparticles (NP/TE) in individuals with varying infectious statuses (uninfected, chronic asymptomatic, or ocular toxoplasmosis). We analyzed the concentration of IFN-γ after NP/TE ex vivo stimulation using ELISA and the immunophenotypes of CD4+ and CD8+ cell populations using flow cytometry. In addition, serotyping of individuals with toxoplasmosis was performed by ELISA using GRA6-derived polypeptides. Low doses of NP/TE stimulation (0.9 μg NP/0.3 μg TE) achieved IFN-γ-specific production in previously exposed human PBMCs without significant differences in the infecting serotype. Increased IFN-γ expression in CD4+ effector memory cell subsets was found in patients with ocular toxoplasmosis with NP/TE but not with TE alone. This is the first study to show how T-cell subsets respond to ex vivo stimulation with a vaccine candidate for human toxoplasmosis, providing crucial insights for future clinical trials.

Genotyping of European Toxoplasma gondii strains by a new high-resolution next-generation sequencing-based method

PURPOSE

A new high-resolution next-generation sequencing (NGS)-based method was established to type closely related European type II Toxoplasma gondii strains.

METHODS

T. gondii field isolates were collected from different parts of Europe and assessed by whole genome sequencing (WGS). In comparison to ME49 (a type II reference strain), highly polymorphic regions (HPRs) were identified, showing a considerable number of single nucleotide polymorphisms (SNPs). After confirmation by Sanger sequencing, 18 HPRs were used to design a primer panel for multiplex PCR to establish a multilocus Ion AmpliSeq typing method. Toxoplasma gondii isolates and T. gondii present in clinical samples were typed with the new method. The sensitivity of the method was tested with serially diluted reference DNA samples.

RESULTS

Among type II specimens, the method could differentiate the same number of haplotypes as the reference standard, microsatellite (MS) typing. Passages of the same isolates and specimens originating from abortion outbreaks were identified as identical. In addition, seven different genotypes, two atypical and two recombinant specimens were clearly distinguished from each other by the method. Furthermore, almost all SNPs detected by the Ion AmpliSeq method corresponded to those expected based on WGS. By testing serially diluted DNA samples, the method exhibited a similar analytical sensitivity as MS typing.

CONCLUSION

The new method can distinguish different T. gondii genotypes and detect intra-genotype variability among European type II T. gondii strains. Furthermore, with WGS data additional target regions can be added to the method to potentially increase typing resolution.

First detection of Toxoplasma gondii Africa 4 lineage in a population of carnivores from South Africa

Introduction

There have only been a few molecular studies conducted on the detection of T. gondii in tissues of carnivores in South Africa, with no data on the genetic diversity of this parasite. That is why the aim of this study was to detect and genotype T. gondii DNA in tissues of selected wild and domestic carnivores in South Africa.

Methods

Samples were collected from 80 animals of 20 species (mainly road-killed) in the four provinces of Limpopo (n=57), Mpumalanga (n=21), Gauteng (n=1) and Free State (n=1) during the period 2014-2018. Samples of brain (n=31), heart (n=4), liver (n=40), spleen (n=2) and lung (n=3) were used to detect T. gondii by real-time PCR targeting a 529 bp repeating fragment of T. gondii DNA. Samples that were positive in real-time PCR were genotyped using 15 microsatellite markers.

Results

T. gondii DNA was detected in 4 (5 %) samples: in the brain from a Black-backed Jackal (Canis mesomelas), in the liver from a African Wildcat (Felis silvestris lybica) and in the liver and heart of two Rusty-spotted Genets (Genetta maculata) respectively. The DNA sample from Black-backed Jackal was genotyped and characterized as belonging to the type Africa 4 lineage (equivalent to RFLP genotype ToxoDB#20), that is a widespread lineage in Africa.

Discussion

This is the first genetic characterization of T. gondii isolated from a wild carnivore on the African continent and the first report of T. gondii in Black-backed Jackal. The Africa 4 lineage was also confirmed in the region of Southern Africa for the first time.

Results of the REIV-TOXO national survey on prenatal screening for toxoplasmosis in Spain

INTRODUCTION

Currently, the status of serological screening for toxoplasmosis in pregnant women in Spain is unknown, and there is no official recommendation. The objective of this study is to show the current practice of gestational screening for toxoplasmosis in hospitals belonging to the Spanish Network for Research on Congenital Toxoplasmosis (REIV-TOXO).

METHODS

An electronic survey was sent between April 2021 and September 2021 to investigators from 118 hospitals of REIV-TOXO, representing all Spanish regions. Nine items related to gestational screening for toxoplasmosis were collected. This information was compared with cases of congenital toxoplasmosis (CT) identified in REIV-TOXO to determine if these were diagnosed in the presence of gestational screening.

RESULTS

During the study period, serological screening was performed in 53.3% (63/118) hospitals, with variations between regions and even among hospitals within the same region. Testing performed in each trimester was the most common practice (57.7%), followed by a single determination (24.4%). 89.4% of CT cases between January 2015 and September 2021 were diagnosed due to gestational screening.

CONCLUSION

The decision to perform gestational screening for toxoplasmosis in Spain is highly heterogeneous, with significant local and regional differences. Despite this, screening still allows the diagnosis of most CT cases. It is urgent to have current epidemiological data to inform decision-making in public health.

Bat-associated microbes: Opportunities and perils, an overview

The potential biotechnological uses of bat-associated bacteria are discussed briefly, indicating avenues for biotechnological applications of bat-associated microbes. The uniqueness of bats in terms of their lifestyle, genomes and molecular immunology may predispose bats to act as disease reservoirs. Molecular phylogenetic analysis has shown several instances of bats harbouring the ancestral lineages of bacterial (Bartonella), protozoal (Plasmodium, Trypanosoma cruzi) and viral (SARS-CoV2) pathogens infecting humans. Along with the transmission of viruses from bats, we also discuss the potential roles of bat-associated bacteria, fungi, and protozoan parasites in emerging diseases. Current evidence suggests that environmental changes and interactions between wildlife, livestock, and humans contribute to the spill-over of infectious agents from bats to other hosts. Domestic animals including livestock may act as intermediate amplifying hosts for bat-origin pathogens to transmit to humans. An increasing number of studies investigating bat pathogen diversity and infection dynamics have been published. However, whether or how these infectious agents are transmitted both within bat populations and to other hosts, including humans, often remains unknown. Metagenomic approaches are uncovering the dynamics and distribution of potential pathogens in bat microbiomes, which might improve the understanding of disease emergence and transmission. Here, we summarize the current knowledge on bat zoonoses of public health concern and flag the gaps in the knowledge to enable further research and allocation of resources for tackling future outbreaks.

Fatal toxoplasmosis in a captive squirrel monkey (Saimiri boliviensis) in Portugal

New World monkeys are especially vulnerable to develop severe clinical manifestations and succumb to acute toxoplasmosis. This study aimed to describe the histopathological findings and genotypic characterization of the Toxoplasma gondii strain involved in a lethal case occurring in a zoo-housed black-capped squirrel monkey (Saimiri boliviensis) in Portugal. Cyst-like structures suggestive of Sarcocystidae parasites and acute injuries in liver and brain were observed by light microscopy examination. By immunohistochemistry, calprotectin, T. gondii antigen and Iba1 antigen had a positive signaling in lung, liver and brain tissues. Toxoplasma gondii B1, ITS1 and 529 repetitive element fragments amplifications together with the genotyping of 13 microsatellite markers confirmed a systemic T. gondii infection linked to a non-clonal type II strain. This description is consistent to the majority T. gondii strains circulating in Europe.

A Case-Control Seroprevalence Survey of Toxoplasmosis in Hemodialysis Patients and Healthy Subjects in Kazeroon and Jahrom Districts in Fars Province, Southern Iran

Opportunistic parasites such as Toxoplasma gondii (T. gondii) are capable of causing neurological and ocular manifestations in patients undergoing hemodialysis. By designing a matched case-control study, we conducted a seromolecular survey of T. gondii in hemodialysis patients compared to a healthy group from Jahrom and Kazeroon cities in Fars Province, Iran. For this purpose, 75 hemodialysis patients from Kazeroon city, 75 hemodialysis patients from Jahrom city, and 75 healthy individuals were recruited for the study. The serum levels of specific immunoglobulins (IgG/IgM) in the case and control groups were evaluated using the enzyme-linked immunosorbent assay (ELISA) method. Also, buffy coat samples were used to extract genomic DNA. Then, Polymerase Chain Reaction (PCR) was accomplished using the RE and GRA6 genes of T. gondii. A standard questionnaire containing demographic factors was administered. Although the seroprevalence of the anti-T. gondii IgG antibody in hemodialysis patients from Kazeroon (18.66% (14/75)) and Jahrom (25.33% (19/75)) was higher than that in the control group (13.33% (10/75)), no statistically significant difference was observed between the case and control groups (P value = 0.373 from Kazeroon and P value = 0.354 from Jahrom). Among the studied variables, only residence (urban) was significantly associated with the anti-T. gondii IgG antibody in the case group from Kazeroon. Also, no IgM antibody titers and DNA of T. gondii were detected in the case and control groups from both cities. Although high seroprevalence of anti-T. gondii IgG antibody was seen in hemodialysis patients, further epidemiological studies with larger samples need to be done in Jahrom and Kazeroon cities and in other parts of Iran. It is also necessary for health officials to establish programs for the prevention and control of T. gondii infection in hemodialysis patients.

Toxoplasma gondii in small mammals in Romania: the influence of host, season and sampling location

BACKGROUND

Toxoplasma gondii is a protozoan parasite that infects a large spectrum of warm-blooded animals, including humans. Small rodents and insectivores play an important role in the epidemiology of T. gondii and may serve as a source of infection for both, domestic and wild definitive felid hosts. Factors influencing the occurrence of T. gondii in wild small mammals are unknown, despite the fact that many intermediate host species are identified. We have used small mammals (Rodentia and Lipotyphla) captured over two years in various habitats, both in urbanised and in natural landscapes. We assessed the importance of land-use, season and host ecology on T. gondii infection.

RESULTS

We examined 471 individuals belonging to 20 small mammal species, collected at 63 locations spread over wide altitude, habitat and land-use ranges from Romania. Heart tissue samples were individually analysed by PCR targeting the 529 bp repetitive DNA fragment of T. gondii. The overall prevalence of infection was 7.3%, with nine species of rodents and two species of shrews being found to carry T. gondii DNA. Five species showed high frequency of infection, with the highest prevalence found in Myodes glareolus (35.5%), followed by Spermophilus citellus (33.3%), Sorex minutus (23.1%), S. araneus (21.7%) and Micromys minutus (11.1%). Adults seemed more often infected than young, however when controlling for season, the difference was not significant, as in spring both adults and young showed higher infection rates, but more adults were sampled. Contrary to our expectations, urban/rural areas (with their implicit high density of domestic feline presence) had no effect on infection prevalence. In addition, neither habitat, nor land-use at sampling sites was important as only geographical location and host species were contributing factors to the infection risk.

CONCLUSIONS

High prevalence of T. gondii infection showed a highly localised, patchy occurrence, with long living and higher mobility host species being the most common carriers, especially during autumn.

Genotyping of toxoplasma gondii isolates from México reveals non-archetypal and potentially virulent strains for mice

Genotyping and virulence studies of Toxoplasma gondii are essential to investigate the pathogenesis of strains circulating worldwide. In this study, eight T. gondii isolates obtained from a congenitally infected newborn, a calf, two cats, three dogs, and a wallaby from five states of México were genotyped by Mn-PCR-RFLP with 11 typing markers (SAG1, SAG2 5'3', alt. SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico), five virulence markers (CS3, ROP16, ROP17, ROP18 and ROP5), 15 microsatellite markers (TUB-2, W35, TgM-A, B18, B17, M33, IV.1, XI.1, M48, M102, N60, N82, AA, N61, N83), and sequencing. A phylogenetic network was built to determine the relationship between Mexican isolates and those reported worldwide. Six different genotypes were identified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), ToxoDB #8, #10, #28 (n = 3), #48, #116, and #282. Genotyping by microsatellite analysis differentiated the three PCR-RFLP genotype #28 isolates into two strains, revealing a total of seven microsatellite genotypes. Three different allele combinations of ROP18/ROP5 virulence markers were also found, 3/3, 1/1, and 4/1. The last two combinations are predicted to be highly virulent in the murine model. According to the phylogenetic network, the T. gondii strains studied here are related to archetypal strains I and III, but none are related to the strains previously reported in México. The genotypes identified in this study in different species of animals demonstrate the great genetic diversity of T. gondii in México. The ToxoDB-PCR-RFLP #28 genotype was found in three isolates from different hosts and states. Additionally, four of the isolates are predicted to be highly virulent in mice. The next step will be to perform in vitro and in vivo assays to determine the phenotype of these T. gondii isolates in murine models.

Isolation and Genetic Characterization of Toxoplasma gondii from a Patas Monkey (Erythrocebus patas) in China

Many cases of Toxoplasma gondii infection have been reported worldwide in non-human primates (NHPs), especially in captive New World monkeys. However, few studies on toxoplasmosis in Old World monkeys have been conducted. In this study, serological and molecular biological analyses were carried out to look for T. gondii antibodies and T. gondii infection in 13 NHPs from China. T. gondii infection was confirmed in 8 NHP cases. T. gondii antibodies were detected in 1/5 New World monkeys and in 4/7 Old World monkeys. T. gondii DNA was detected in 3/5 New World monkeys and 5/7 Old World monkeys. The one ring-tailed lemur was negative for both antibodies and DNA of T. gondii. The most common clinical manifestations of T. gondii infection were malaise, poor appetite, emaciation, and foamy nasal discharge. The most common histopathological findings were interstitial pneumonia, necrotic hepatitis, necrotizing myocarditis, lymphadenitis, and necrotic splenitis. One viable T. gondii strain was successfully isolated from the myocardium of a patas monkey (Erythrocebus patas) by bioassay in mice. T. gondii tachyzoites were obtained from cell cultures and were designated as TgMonkeyCHn2. The genotype of this strain belongs to ToxoDB genotype #9, and the allele of ROP18/ROP5 gene was 3/6. TgMonkeyCHn2 tachyzoites were avirulent in Swiss mice. To our knowledge, this is the first report of fatal toxoplasmosis in a patas monkey. T. gondii infection in patas monkeys may indicate environmental contamination by oocysts. The patas monkey is a new host record for T. gondii.

Protein kinases on carbon metabolism: potential targets for alternative chemotherapies against toxoplasmosis

The apicomplexan parasite Toxoplasma gondii is the causative agent of toxoplasmosis, a global disease that significantly impacts human health. The clinical manifestations are mainly observed in immunocompromised patients, including ocular damage and neuronal alterations leading to psychiatric disorders. The congenital infection leads to miscarriage or severe alterations in the development of newborns. The conventional treatment is limited to the acute phase of illness, without effects in latent parasites; consequently, a cure is not available yet. Furthermore, considerable toxic effects and long-term therapy contribute to high treatment abandonment rates. The investigation of exclusive parasite pathways would provide new drug targets for more effective therapies, eliminating or reducing the side effects of conventional pharmacological approaches. Protein kinases (PKs) have emerged as promising targets for developing specific inhibitors with high selectivity and efficiency against diseases. Studies in T. gondii have indicated the presence of exclusive PKs without homologs in human cells, which could become important targets for developing new drugs. Knockout of specific kinases linked to energy metabolism have shown to impair the parasite development, reinforcing the essentiality of these enzymes in parasite metabolism. In addition, the specificities found in the PKs that regulate the energy metabolism in this parasite could bring new perspectives for safer and more efficient therapies for treating toxoplasmosis. Therefore, this review provides an overview of the limitations for reaching an efficient treatment and explores the role of PKs in regulating carbon metabolism in Toxoplasma, discussing their potential as targets for more applied and efficient pharmacological approaches.

A ring trial to harmonize Toxoplasma gondii microsatellite typing: comparative analysis of results and recommendations for optimization

A ring trial among five European laboratories was organized to reach consistency in microsatellite (MS) typing of the zoonotic parasite Toxoplasma gondii. Three sample sets were circulated and analyzed by each laboratory following a previously published method that is based on fragment length polymorphism of 15 MS markers. The first sample set compared typing results in general and focused on effects of DNA concentration; the second sample set focused on the polymorphic fingerprinting markers that can differentiate T. gondii strains within the same archetypal lineage; and the third set focused on non-archetypal genotypes. Methodological variations between laboratories, including the software programs used to determine MS fragment length, were collated using a questionnaire. Overall, lineage-level typing results reached a high level of agreement, especially in samples with the highest DNA concentrations. However, laboratory-specific differences were observed for particular markers. Major median differences in fragment length, of up to 6 base pairs, were related to the fluorophore used to label fragment-specific primers. In addition, primer pairs with identical sequences obtained from different suppliers resulted in fragments of differing length. Furthermore, differences in the way the sequencing profiles were assessed and interpreted may have led to deviating results in fragment length determination. Harmonization of MS typing, for example, by using the same fluorophores or by numerical adjustments applied to the fragment-lengths determined, could improve the uniformity of the results across laboratories. This is the first interlaboratory comparison, providing guidelines (added as a supplement) for the optimization of this technique.

Seroprevalence and Risk Factors for Toxoplasma gondii Infection in Horses

BACKGROUND

Toxoplasma gondii is classified as intracellular protozoa and is one of the major zoonotic parasites. Most warm-blooded intermediate hosts, including humans, are commonly infected by this parasite. The epidemiology of T. gondii infection in Egyptian horses is currently poorly understood.

METHODS

420 blood samples were randomly collected from horses raised in four governorates in Northern Egypt (110 each from Giza and Kafr El Sheikh, and 100 each from Qalyubia and Gharbia) to investigate the existence of antibodies against T. gondii using a commercial ELISA kit, and to ascertain the risk factors for the infection.

RESULTS

the antibodies for T. gondii were found in 16.2% (68/420) of the examined horses, with no significant differences among the four studied governorates. The highest prevalence rate was observed in Giza. The results revealed that sex, breed, age, and contact with domestic ruminants or cats were recognized as potential risk factors. The high prevalence rate was found in mixed breed horses (OR = 2.63, 95% CI: 0.95-7.26), mares (OR = 2.35, 95% CI: 1.31-4.19), and horses aged over 10 years (OR = 2.78, 95% CI: 1.30-3.44). Moreover, the likelihood of seropositivity for T. gondii infection was higher in horses raised in environments with cats (OR = 1.97, 95% CI: 1.13-3.44, p = 0.017) or domestic ruminants (OR = 2.16, 1.21-3.86, p = 0.010). This report confirms that horses in Northern Egypt are exposed to T. gondii and thus raises the possibility that people and other animals could contract the disease.

CONCLUSIONS

routine examination and management of T. gondii infection in horses in these governorates is advised.

Virulence evolution of Toxoplasma gondii within a multi‐host system

Current research on the virulence evolution of Toxoplasma gondii is mainly conducted via experiments, and studies using mathematical models are still limited. Here, we constructed a complex cycle model of T. gondii in a multi-host system considering multiple transmission routes and cat-mouse interaction. Based on this model, we studied how the virulence of T. gondii evolves with the factors related to transmission routes and the regulation of infection on host behavior under an adaptive dynamics framework. The study shows that all factors that enhance the role of mice favored decreased virulence of T. gondii, except the decay rate of oocysts that led to different evolutionary trajectories under different vertical transmission. The same was true of the environmental infection rate of cats, whose effect was different under different vertical transmission. The effect of the regulation factor on the virulence evolution of T. gondii was the same as that of the inherent predation rate depending on its net effect on direct and vertical transmissions. The global sensitivity analysis on the evolutionary outcome suggests that changing the vertical infection rate and decay rate was most effective in regulating the virulence of T. gondii. Furthermore, the presence of coinfection would favor virulent T. gondii and make evolutionary bifurcation easy to occur. The results reveal that the virulence evolution of T. gondii had a compromise between adapting to different transmission routes and maintaining the cat-mouse interaction thereby leading to different evolutionary scenarios. This highlights the significance of evolutionary ecological feedback to evolution. In addition, the qualitative verification of T. gondii virulence evolution in different areas by the present framework will provide a new perspective for the study of evolution.

High infection rates of Toxoplasma gondii in cattle, sheep and pigs from Israel

Toxoplasma gondii is an obligate intracellular parasite belonging to the phylum Apicomplexa, which causes the zoonotic disease toxoplasmosis. T. gondii infects almost all warm blood animals. Generally, infected animals are asymptomatic and remain infected for life. Infection of humans occurs by consumption of infected undercooked meat or contaminated vegetables, fruit and water. The aim of this study was to evaluate the prevalence and seroprevalence of T. gondii in livestock in Israel. For the serological screening we investigated the presence of antibodies against T. gondii in sera using the indirect fluorescent antibody test (IFAT). Molecular screening was preformed using conventional PCR and nested PCR for the detection of T. gondii DNA in tissue samples. Serum samples of 249 cattle and 138 sheep were collected from farms. This serological survey showed high seroprevalence with seropositivity of 29 % in cattle and 33 % in sheep. In addition, 526 paired sera and tissue samples from cattle, sheep and pigs were obtained in slaughterhouses. The serological prevalence of T. gondii in healthy animals intended for human consumption was 29.4 % in cattle, 26.1 % in sheep and 8.1 % in pigs. The molecular detection of T. gondii in the tissue samples was 7.5 % in cattle, 7.3 % in sheep and 6.3 % in pigs. Considering the combined positive results from both serological and molecular assays, exposure to or infection with the parasite was present in 26.2 % of the samples (33.8 % in cattle, 30.3 % in sheep, 12.5 % in pigs). The prevalence of T. gondii in pigs was significantly lower compared to that of cattle and sheep (P < 0.001). All PCR positive samples from animals and 12 human positive samples were genotyped using a restriction fragment length polymorphism (PCR-RFLP) method. The results showed the existence of atypical genotypes in the majority of the samples and no correlation between animals and human samples could be determined from this study. Widespread exposure to T. gondii in Israel with the presence of parasite DNA in meat from cattle, sheep and pigs meant for human consumption was found.

Molecular prevalence, genetic characterization and patterns of Toxoplasma gondii infection in domestic small mammals from Cotonou, Benin

Toxoplasmosis, one of the most prevalent parasitic infections in humans and animals, is caused by the intracellular protozoan parasite Toxoplasma gondii. Small mammals play a key role as intermediate reservoir hosts in the maintenance of the T. gondii life cycle. In this study, we estimated the molecular prevalence and provide genetic diversity data for T. gondii in 632 small mammals sampled in four areas of Cotonou city, Benin. Both the brain and heart of each individual were screened through T. gondii-targeting qPCR, and positive samples were then genotyped using a set of 15 T. gondii-specific microsatellites. Prevalence data were statistically analyzed in order to assess the relative impact of individual host characteristics, spatial distribution, composition of small mammal community, and urban landscape features. An overall T. gondii molecular prevalence of 15.2% was found and seven genotypes, all belonging to the Africa 1 lineage, could be retrieved from the invasive black rat Rattus rattus and the native African giant shrew Crocidura olivieri. Statistical analyses did not suggest any significant influence of the environmental parameters used in this study. Rather, depending on the local context, T. gondii prevalence appeared to be associated either with black rat, shrew, or mouse abundance or with the trapping period. Overall, our results highlight the intricate relationships between biotic and abiotic factors involved in T. gondii epidemiology and suggest that R. rattus and C. olivieri are two competent reservoirs for the Africa 1 lineage, a widespread lineage in tropical Africa and the predominant lineage in Benin.

Additional evidence of tigers (Panthera tigris altaica) as intermediate hosts for Toxoplasma gondii through the isolation of viable strains

Toxoplasmosis is one of the most common zoonotic diseases in the world. Felines excrete Toxoplasma gondii oocysts, which play a key role in the transmission of this protozoon. Pathological diagnoses were performed on four carcasses of captive tigers collected from 2019 to 2021 in China, and T. gondii was surveyed using serology, molecular analysis, and aetiology. Striated muscle samples of the tigers (n = 4) were bioassayed in mice. DNA derived from T. gondii tachyzoites was isolated and characterized using PCR-RFLP. The pathological diagnoses revealed that ageing, declined immune function, liver, and kidney failures caused the deaths in the tigers examined. A modified agglutination test (cut-off: 1:25) revealed that IgG antibodies to T. gondii were 100% (4/4) in the captive tigers. Two viable T. gondii strains (TgTigerCHn3 and TgTigerCHn4) were isolated from tiger striated muscles and seeded on the Vero cell culture for further propagation. The genotypes of TgTigerCHn3 and TgTigerCHn4 were ToxoDB#20 and ToxoDB#2, respectively. The two strains were avirulent for Swiss mice, which matched the ROP18 and ROP5 gene alleles of TgtigerCHn3 (3/4) and TgtigerCHn4 (3/3). Few brain tissue cysts (0-213) were observed in the mice after inoculation with TgTigerCHn3 and TgTigerCHn4. This is the first documented isolation of T. gondii ToxoDB#20 and ToxoDB#2 from tigers. The results provide additional direct evidence of tiger as intermediate hosts for T. gondii. Tigers in the zoos may potentially transmit T. gondii to other animals and humans.

Managing host-parasite interactions in humans and wildlife in times of global change

Global change in the Anthropocene has modified the environment of almost any species on earth, be it through climate change, habitat modifications, pollution, human intervention in the form of mass drug administration (MDA), or vaccination. This can have far-reaching consequences on all organisational levels of life, including eco-physiological stress at the cell and organism level, individual fitness and behaviour, population viability, species interactions and biodiversity. Host-parasite interactions often require highly adapted strategies by the parasite to survive and reproduce within the host environment and ensure efficient transmission among hosts. Yet, our understanding of the system-level outcomes of the intricate interplay of within host survival and among host parasite spread is in its infancy. We shed light on how global change affects host-parasite interactions at different organisational levels and address challenges and opportunities to work towards better-informed management of parasite control. We argue that global change affects host-parasite interactions in wildlife inhabiting natural environments rather differently than in humans and invasive species that benefit from anthropogenic environments as habitat and more deliberate rather than erratic exposure to therapeutic drugs and other control efforts.

A unique Toxoplasma gondii haplotype accompanied the global expansion of cats

Toxoplasma gondii is a cyst-forming apicomplexan parasite of virtually all warm-blooded species, with all true cats (Felidae) as definitive hosts. It is the etiologic agent of toxoplasmosis, a disease causing substantial public health burden worldwide. Few intercontinental clonal lineages represent the large majority of isolates worldwide. Little is known about the evolutionary forces driving the success of these lineages, the timing and the mechanisms of their global dispersal. In this study, we analyse a set of 156 genomes and we provide estimates of T. gondii mutation rate and generation time. We elucidate how the evolution of T. gondii populations is intimately linked to the major events that have punctuated the recent history of cats. We show that a unique haplotype, whose length represents only 0.16% of the whole T. gondii genome, is common to all intercontinental lineages and hybrid populations derived from these lineages. This haplotype has accompanied wildcats (Felis silvestris) during their emergence from the wild to domestic settlements, their dispersal in the Old World, and their expansion in the last five centuries to the Americas. The selection of this haplotype is most parsimoniously explained by its role in sexual reproduction of T. gondii in domestic cats.

Toxoplasma gondii Serotypes in Italian and Foreign Populations: A Cross-Sectional Study Using a Homemade ELISA Test

Toxoplasma gondii is a protozoan parasite responsible for human toxoplasmosis. The three major clonal lineages and different recombinant strains of T. gondii have a varied global distribution. This study aimed at evaluating the epidemiological distribution of types II and I–III and recombinant or mixed T. gondii in Italians and foreigners residing in Italy, establishing an association between serotypes and demographic characteristics. We collected the sera of 188 subjects who had tested positive for specific T. gondii antibodies. The population was differentiated into groups based on sex, nationality, and place of birth (Italy, Africa, South America, Asia, or Europe (except Italy)). We then performed a homemade ELISA test that detected both the antibodies against the amino acid sequences of the three main genotype antigens (I–III) in human sera and discerned the T. gondii strains. Serotype II of T. gondii was the most prevalent in the Italian population, whereas type I–III was the most prevalent in the foreign group. Surprisingly, we observed a notable amount of recombinant or mixed serotypes in European and Italian subjects. Moreover, we showed a significant difference in the prevalence of T. gondii serotypes between men and women, Italians, and foreigners. This descriptive study is the first to investigate the epidemiological distribution of T. gondii serotypes in humans in Italy using a homemade ELISA. We considered this technique suitable for discriminating between serotypes II and I–III and, consequently, for an epidemiological study focusing on the observation of circulating T. gondii strains and clinical correlations.

Toxoplasma gondii dense granule protein 3 promotes endoplasmic reticulum stress-induced apoptosis by activating the PERK pathway

Background

Toxoplasma gondii is a neurotropic single-celled parasite that can infect mammals, including humans. Central nervous system infection with T. gondii infection can lead to Toxoplasma encephalitis. Toxoplasma infection can cause endoplasmic reticulum (ER) stress and unfolded protein response (UPR) activation, which ultimately can lead to apoptosis of host cells. The dense granule protein GRA3 has been identified as one of the secretory proteins that contribute to the virulence of T. gondii; however, the mechanism remains enigmatic.

Methods

The expression of the GRA3 gene in RH, ME49, Wh3, and Wh6 strains was determined using quantitative real-time polymerase chain reaction (qRT–PCR). pEGFP-GRA3_Wh6 was constructed by inserting Chinese 1 Wh6 GRA3 (GRA3_Wh6) cDNA into a plasmid encoding the enhanced GFP. Mouse neuro2a (N2a) cells were transfected with either pEGFP or pEGFP-GRA3_Wh6 (GRA3_Wh6) and incubated for 24–36 h. N2a cell apoptosis and ER stress-associated proteins were determined using flow cytometry and immunoblotting. Furthermore, N2a cells were pretreated with GSK2656157 (a PERK inhibitor) and Z-ATAD-FMK (a caspase-12 inhibitor) before GRA3_Wh6 transfection, and the effect of the inhibitors on GRA3_Wh6-induced ER stress and apoptosis were investigated.

Results

GRA3 gene expression was higher in the less virulent strains of type II ME49 and type Chinese 1 Wh6 strains compared with the virulent strains of type I RH strain and type Chinese 1 Wh3 strain. Transfection with GRA3_Wh6 plasmid induced neuronal apoptosis and increased the expression of GRP78, p-PERK, cleaved caspase-12, cleaved caspase-3, and CHOP compared with the control vector. Pretreatment with GSK2656157 and Z-ATAD-FMK decreased apoptosis in N2a cells, and similarly, ER stress- and apoptosis-associated protein levels were significantly decreased.

Conclusion

GRA3 induces neural cell apoptosis via the ER stress signaling pathway, which could play a role in toxoplasmic encephalitis.

Graphical Abstract

Paving the Way: Contributions of Big Data to Apicomplexan and Kinetoplastid Research

In the age of big data an important question is how to ensure we make the most out of the resources we generate. In this review, we discuss the major methods used in Apicomplexan and Kinetoplastid research to produce big datasets and advance our understanding of Plasmodium, Toxoplasma, Cryptosporidium, Trypanosoma and Leishmania biology. We debate the benefits and limitations of the current technologies, and propose future advancements that may be key to improving our use of these techniques. Finally, we consider the difficulties the field faces when trying to make the most of the abundance of data that has already been, and will continue to be, generated.

Unifying Virulence Evaluation in Toxoplasma gondii: A Timely Task

Toxoplasma gondii, a major zoonotic pathogen, possess a significant genetic and phenotypic diversity that have been proposed to be responsible for the variation in clinical outcomes, mainly related to reproductive failure and ocular and neurological signs. Different T. gondii haplogroups showed strong phenotypic differences in laboratory mouse infections, which provide a suitable model for mimicking acute and chronic infections. In addition, it has been observed that degrees of virulence might be related to the physiological status of the host and its genetic background. Currently, mortality rate (lethality) in outbred laboratory mice is the most significant phenotypic marker, which has been well defined for the three archetypal clonal types (I, II and III) of T. gondii; nevertheless, such a trait seems to be insufficient to discriminate between different degrees of virulence of field isolates. Many other non-lethal parameters, observed both in in vivo and in vitro experimental models, have been suggested as highly informative, yielding promising discriminatory power. Although intra-genotype variations have been observed in phenotypic characteristics, there is no clear picture of the phenotypes circulating worldwide; therefore, a global overview of T. gondii strain mortality in mice is presented here. Molecular characterization has been normalized to some extent, but this is not the case for the phenotypic characterization and definition of virulence. The present paper proposes a baseline (minimum required information) for the phenotypic characterization of T. gondii virulence and intends to highlight the needs for consistent methods when a panel of T. gondii isolates is evaluated for virulence.

Toxoplasma gondii Genotyping: A Closer Look Into Europe

Toxoplasma gondii is a major zoonotic agent which may cause harmful effects mainly in pregnant and immunocompromised hosts. Despite many efforts on its genetic characterization, an entirely clear picture of the population structure in Europe has not been achieved yet. The present study aimed to summarize the available genotyping information and to map the distribution of circulating strains. There is consensus on type II T. gondii genotypes prevailing in Europe, but the absence of harmonization in the use of typing methods limits detailed knowledge. Standardized, high-end typing tools and integrative strategies are needed to fill the gaps and complete an accurate image of the T. gondii genetic population in Europe.

Comparative Phosphoproteomic Analysis of Sporulated Oocysts and Tachyzoites of Toxoplasma gondii Reveals Stage-Specific Patterns

Toxoplasma gondii is an obligate intracellular protozoan of severe threat to humans and livestock, whose life history harbors both gamic and apogamic stages. Chinese 1 (ToxoDB#9) was a preponderant genotype epidemic in food-derived animals and humans in China, with a different pathogenesis from the strains from the other nations of the world. Posttranslational modifications (PTMs) of proteins were critical mediators of the biology, developmental transforms, and pathogenesis of protozoan parasites. The phosphoprotein profiling and the difference between the developmental phases of T. gondii, contributing to development and infectivity, remain unknown. A quantitative phosphoproteomic approach using IBT integrated with TiO₂ affinity chromatography was applied to identify and analyze the difference in the phosphoproteomes between the sporulated oocysts and the tachyzoites of the virulent ToxoDB#9 (PYS) strain of T. gondii. A total of 4058 differential phosphopeptides, consisting of 2597 upregulated and 1461 downregulated phosphopeptides, were characterized between sporulated the oocysts and tachyzoites. Twenty-one motifs extracted from the upregulated phosphopeptides contained 19 serine motifs and 2 threonine motifs (GxxTP and TP), whereas 16 motifs identified from downregulated phosphopeptides included 13 serine motifs and 3 threonine motifs (KxxT, RxxT, and TP). Beyond the traditional kinases, some infrequent classes of kinases, including Ab1, EGFR, INSR, Jak, Src and Syk, were found to be corresponding to motifs from the upregulated and downregulated phosphopeptides. Remarkable functional properties of the differentially expressed phosphoproteins were discovered by GO analysis, KEGG pathway analysis, and STRING analysis. S8GFS8 (DNMT1-RFD domain-containing protein) and S8F5G5 (Histone kinase SNF1) were the two most connected peptides in the kinase-associated network. Out of these, phosphorylated modifications in histone kinase SNF1 have functioned in mitosis and interphase of T. gondii, as well as in the regulation of gene expression relevant to differentiation. Our study discovered a remarkable difference in the abundance of phosphopeptides between the sporulated oocysts and tachyzoites of the virulent ToxoDB#9 (PYS) strain of T. gondii, which may provide a new resource for understanding stage-specific differences in PTMs and may enhance the illustration of the regulatory mechanisms contributing to the development and infectivity of T. gondii.

Characterization of antimicrobial resistance genes and virulence factor genes in an Arctic permafrost region revealed by metagenomics

Antimicrobial resistance genes (ARGs) and virulence factor genes (VFGs) constitute a serious threat to public health, and climate change has been predicted to affect the increase in bacterial pathogens harboring ARGs and VFGs. However, studies on bacterial pathogens and their ARGs and VFGs in permafrost region have received limited attention. In this study, a metagenomic approach was applied to a comprehensive survey to detect potential ARGs, VFGs, and pathogenic antibiotic resistant bacteria (PARB) carrying both ARGs and VFGs in the active layer and permafrost. Overall, 70 unique ARGs against 18 antimicrobial drug classes and 599 VFGs classified as 38 virulence factors were detected in the Arctic permafrost region. Eight genes with mobile genetic elements (MGEs) carrying ARGs were identified; most MGEs were classified as phages. In the metagenome-assembled genomes, the presence of 15 PARB was confirmed. The soil profile showed that the transcripts per million (TPM) values of ARGs and VFGs in the sub-soil horizon were significantly lower than those in the top soil horizon. Based on the TPM value of each gene, major ARGs, VFGs, and these genes in PARB from the Arctic permafrost region were identified and their distribution was confirmed. The major host bacteria for ARGs and VFGs and PARB were identified. A comparison of the percentage identity distribution of ARGs and VFGs to reference databases indicated that ARGs and VFGs in the Arctic soils differ from previously identified genes. Our results may help understand the characteristics and distribution of ARGs, VFGs, and these genes in PARB in the Arctic permafrost region. This findings suggest that the Arctic permafrost region may serve as potential reservoirs for ARGs, VFGs, and PARB. These genes could pose a new threat to human health if they are released by permafrost thawing owing to global warming and propagate to other regions.

Development of a new serotyping ELISA for Toxoplasma gondii type II, type III and Africa 1 lineages using in silico peptide discovery methods, well categorized feline and human outbreak serum samples

BACKGROUND

Discovery of new Toxoplasma gondii serotyping epitopes is important due to reports showing the influence of genotype on the severity of toxoplasmosis. In Turkey, genotypes belonging to type II, type III and Africa 1 lineages were mainly detected. The present study focused on to find out epitopes with high discriminative capacity to serotype these genotypes using well characterized strains isolated from Turkey.

METHODS

To meet this objective, GRA6 and GRA7 genes were sequenced from strains belonging to the type II, III and Africa 1 lineages, and B cell epitopes inside these sequences were predicted by Bcepred and additional docking analysis was performed with B cell receptor. Based on these analyses, 22 peptides harboring lineage specific epitopes were synthesized. Then, the serotyping potency of these peptides was tested using peptide ELISA and well categorized serum samples collected from stray cats infected with genotypes of the different lineages type II (n:9), III (n:1) and Africa 1 (n:1). As a result of peptide-ELISA, a serotyping schema was constructed with peptides that show high discriminative capacity and this assay was validated by sera collected from humans after an outbreak (n:30) and mother/newborn pair sera (n:3). Later, the validated serotyping schema was used to serotype a larger group of human (n:38) and cat (n:24) sera.

RESULTS

Among 22 peptides, GRA6II/c, GRA7III/d, and GRA6 Africa 1/b epitopes have shown discriminative capacity. During the validation of peptide-ELISA, the serotype of toxoplasmosis outbreak and mother/newborn cases were detected to be serotype II. Moreover, the analyses in a larger group showed that serotype II was prevalent in humans and stray cats.

CONCLUSIONS

Overall, the results showed that the serotyping schema could be successfully used to serotype T. gondii infections caused by type II, III and Africa 1 genotype.

Association of Common Zoonotic Pathogens With Concentrated Animal Feeding Operations

Animal farming has intensified significantly in recent decades, with the emergence of concentrated animal feeding operations (CAFOs) in industrialized nations. The congregation of susceptible animals in CAFOs can lead to heavy environmental contamination with pathogens, promoting the emergence of hyper-transmissible, and virulent pathogens. As a result, CAFOs have been associated with emergence of highly pathogenic avian influenza viruses, hepatitis E virus, Escherichia coli O157:H7, Streptococcus suis, livestock-associated methicillin-resistant Staphylococcus aureus, and Cryptosporidium parvum in farm animals. This has led to increased transmission of zoonotic pathogens in humans and changes in disease patterns in general communities. They are exemplified by the common occurrence of outbreaks of illnesses through direct and indirect contact with farm animals, and wide occurrence of similar serotypes or subtypes in both humans and farm animals in industrialized nations. Therefore, control measures should be developed to slow down the dispersal of zoonotic pathogens associated with CAFOs and prevent the emergence of new pathogens of epidemic and pandemic potential.

The pathogenicity and virulence of Toxoplasma gondii

Toxoplasma gondii is a parasitic protist infecting a wide group of warm-blooded animals, ranging from birds to humans. While this infection is usually asymptomatic in healthy individuals, it can also lead to severe ocular or neurological outcomes in immunocompromised individuals or in developing fetuses. This obligate intracellular parasite has the ability to infect a considerable range of nucleated cells and can propagate in the intermediate host. Yet, under the pressure of the immune system it transforms into an encysted persistent form residing primarily in the brain and muscle tissues. Encysted parasites, which are resistant to current medication, may reactivate and give rise to an acute infection. The clinical outcome of toxoplasmosis depends on a complex balance between the host immune response and parasite virulence factors. Susceptibility to the disease is thus determined by both parasite strains and host species. Recent advances on our understanding of host cell-parasite interactions and parasite virulence have brought new insights into the pathophysiology of T. gondii infection and are summarized here.

Toxoplasma gondii Genotypes Circulating in Serbia-Insight into the Population Structure and Diversity of the Species in Southeastern Europe, a Region of Intercontinental Strain Exchange

In Europe, Toxoplasma gondii lineage II is dominant, and ToxoDB#1 the most frequently occurring genotype. The abundance of lineage III genotypes varies geographically and lineage I are rare, yet present in several regions of the continent. Data on the T. gondii population structure in southeastern Europe (SEE) are scarce, yet necessary to appreciate the diversity of the species in Europe. To help fill this gap, we genotyped 67 strains from nine species of intermediate hosts in Serbia by MnPCR-RFLP, determined the population structure, and identified the genotypes using ToxoDB. A neighbor-joining tree was also constructed from the isolates genotyped on nine loci. While 42% of the total genotype population consisted of ToxoDB#1 and ToxoDB#2, variant genotypes of both lineages comprised 46% of the population in wildlife and 28% in domestic animals and humans. One genotype of Africa 4 lineage was detected in a human sample. Interestingly, the findings include one lineage III variant and one II/III recombinant isolate with intercontinental distribution, which appear to be moderately related to South American genotypes. Based on these findings, SEE is a region of underappreciated T. gondii genetic diversity and possible strain exchange between Europe and Africa.

Challenges in modelling the dynamics of infectious diseases at the wildlife-human interface

The Covid-19 pandemic is of zoonotic origin, and many other emerging infections of humans have their origin in an animal host population. We review the challenges involved in modelling the dynamics of wildlife–human interfaces governing infectious disease emergence and spread. We argue that we need a better understanding of the dynamic nature of such interfaces, the underpinning diversity of pathogens and host–pathogen association networks, and the scales and frequencies at which environmental conditions enable spillover and host shifting from animals to humans to occur. The major drivers of the emergence of zoonoses are anthropogenic, including the global change in climate and land use. These, and other ecological processes pose challenges that must be overcome to counterbalance pandemic risk. The development of more detailed and nuanced models will provide better tools for analysing and understanding infectious disease emergence and spread.

Nanos gigantium humeris insidentes: old papers informing new research into Toxoplasma gondii

Since Nicolle, Manceaux and Splendore first described Toxoplasma gondii as a parasite of rodents and rabbits in the early 20th century, a diverse and vigorous research community has been built around studying this fascinating intracellular parasite. In addition to its importance as a pathogen of humans, livestock and wildlife, modern researchers are attracted to T. gondii as a facile experimental system to study many aspects of evolutionary biology, cellular biology, host-microbe interactions, and host immunity. For new researchers entering the field, the extensive literature describing the biology of the parasite, and the interactions with its host, can be daunting. In this review, we examine four foundational studies that describe various aspects of T. gondii biology, presenting a 'journal club'-style analysis of each. We have chosen a paper that established the beguiling life cycle of the parasite (Hutchison et al., 1971), a paper that described key features of its cellular biology that the parasite shares with related organisms (Gustafson et al., 1954), a paper that characterised the origin of the unique compartment in which the parasite resides within host cells (Jones and Hirsch, 1972), and a paper that established a key mechanism in the host immune response to parasite infection (Pfefferkorn, 1984). These interesting and far-reaching studies set the stage for subsequent research into numerous facets of parasite biology. As well as providing new researchers with an entry point into the literature surrounding the parasite, revisiting these studies can remind us of the roots of our discipline, how far we have come, and the new directions in which we might head.

Long-term impact of congenital toxoplasmosis on phenotypic and functional features of circulating leukocytes from infants one year after treatment onset

Changes in immune response of children with congenital toxoplasmosis (CT) regarding infection evolution and therapeutic intervention was addressed. Infants with CT presented increased counts of monocytes, CD3^-CD16^-CD56^High, CD3⁺CD56⁺ and CD4⁺ T-cells 1-year after treatment onset (TOXO_1-yearAT). Smaller numbers of CD3^-CD16^-CD56⁺ and TCRγδ⁺ T-cells were specifically observed in infants with retinochoroidal lesions (L(+)). When infants were classified based on the baseline status, expansion of CD3^-CD16^-CD56^High and CD4⁺ T-cells were observed in L(+) who had active, active/cicatricial or cicatricial lesions. Infants who had active or active/cicatricial lesions display augmented numbers of monocytes, CD3^-CD16⁺CD56⁺, CD3⁺CD56⁺, CD8⁺DR⁺ and TCRγδ⁺ T-cells and those with active/cicatricial or cicatricial at baseline displayed increase in CD14⁺CD64⁺ monocytes. Moreover, all L(+) had increased IFN-γ⁺ and IL-10⁺ CD4⁺ T-cells, while L(-) had increased ratios of TNF⁺, IFN-γ⁺ and IL-4⁺ NK-cells upon antigen-specific stimulation. Persistent alterations in leukocytes in TOXO_1-yearAT suggest long-term sequels in the immune system of infants with CT.

Prevalence of Antibodies to Toxoplasma gondii in Different Wild Bird Species Admitted to Rehabilitation Centres in Portugal

Toxoplasma gondii is a worldwide zoonotic parasite. According to the “One Health” approach, studies on toxoplasmosis are essential since it affects humans and domestic and wild animals. In the present study, antibodies to T. gondii were determined in serum samples from 263 wild birds located in five wildlife rehabilitation centres in mainland Portugal by using the modified agglutination test (MAT) with a cut-off titre of 20. An overall seroprevalence of 36.5% (95% confidence interval [CI]: 30.7–42.6) was observed. For the first time, antibodies to T. gondii were detected in some avian species, including pallid swift (Apus pallidus) (33.3%), black-backed gull (Larus fuscus) (39.3%), European turtle-dove (Streptopelia turtur) (100%), bee-eater (Merops apiaster) (50.0%), carrion crow (Corvus corone) (33.3%), and Egyptian vulture (Neophron percnopterus) (100%), which expands the list of intermediate hosts of T. gondii. A lower seroprevalence was found in juvenile birds (31.9%) compared to adults (48.7%) (p = 0.016). The central region of Portugal was considered a risk factor for T. gondii infection in wild birds (odds ratio: 3.61; 95% CI: 1.09–11.91). This pioneer study calls attention to the need for further studies, to provide a clearer understanding of T. gondii epidemiology in Portugal, because it reflects wide dispersion of T. gondii oocysts in the environment.

Human Codon Usage: The Genetic Basis of Pathogen Latency

Infectious diseases pose two main compelling issues. First, the identification of the molecular factors that allow chronic infections, that is, the often completely asymptomatic coexistence of infectious agents with the human host. Second, the definition of the mechanisms that allow the switch from pathogen dormancy to pathologic (re)activation. Furthering previous studies, the present study (1) analyzed the frequency of occurrence of synonymous codons in coding DNA, that is, codon usage, as a genetic tool that rules protein expression; (2) described how human codon usage can inhibit protein expression of infectious agents during latency, so that pathogen genes the codon usage of which does not conform to the human codon usage cannot be translated; and (3) framed human codon usage among the front-line instruments of the innate immunity against infections. In parallel, it was shown that, while genetics can account for the molecular basis of pathogen latency, the changes of the quantitative relationship between codon frequencies and isoaccepting tRNAs during cell proliferation offer a biochemical mechanism that explains the pathogen switching to (re)activation. Immunologically, this study warns that using codon optimization methodologies can (re)activate, potentiate, and immortalize otherwise quiescent, asymptomatic pathogens, thus leading to uncontrollable pandemics.

Toxoplasma gondii in South America: a differentiated pattern of spread, population structure and clinical manifestations

Toxoplasma gondii is an obligate intracellular parasite belonging to the phylum Apicomplexa. It has a worldwide distribution and can infect a wide variety of intermediate hosts, including humans. In South America, toxoplasmosis shows high health impacts, and the incidence of the disease is frequently reported and more severe than in other regions, such as Europe. Although most T. gondii infections are asymptomatic, severe manifestations can occur in cases of congenital toxoplasmosis and immunocompromised individuals. In South America, the ocular disease in immunocompetent individuals is also frequently reported. Treatment for any clinical manifestation of toxoplasmosis consists of the combination of sulfadiazine (SDZ) and pyrimethamine (PYR). However, failures in the treatment of toxoplasmosis have been reported, especially in South America, suggesting the acquisition of resistance against SDZ and PYR. Another paradigm present in the literature is that once infected with T. gondii, the host is immunologically protected from further reinfections. However, some studies indicate cases of congenital transmission of T. gondii from immunocompetent pregnant women with chronic infection, suggesting the possibility of reinfection in humans. Thus, in this review, we will cover several aspects of South American T. gondii isolates, such as genetic characterization, disease manifestation, host reinfection and drug resistance.

Seasonal variations and public search interests in Toxoplasma: a 16-year retrospective analysis of big data on Google Trends

BACKGROUND

This study aims to understand whether there is a seasonal change in the internet search interest for Toxoplasma by using the data derived from Google Trends (GT).

METHODS

The present study searched for the relative search volume (RSV) for the search term 'Toxoplasma' in GT within six major English-speaking countries (Australia, New Zealand [Southern Hemisphere] and Canada, Ireland, the UK and the USA [Northern Hemisphere] from 1 January 2004 to 31 December 2019, utilizing the category of 'health'. Data regarding the RSV of Toxoplasma was obtained and further statistical analysis was performed in R software using the 'season' package.

RESULTS

There were significantly seasonal patterns for the RSV of the search term 'Toxoplasma' in five countries (all p<0.05), except for the UK. A peak in December-March and a trough in July-September (Canada, Ireland, the UK and the USA) were observed, while a peak in June/August and a trough in December/February (Australia, New Zealand) were also found. Moreover, the presence of seasonal patterns regarding RSV for 'Toxoplasma' between the Southern and Northern Hemispheres was also found (both p<0.05), with a reversed meteorological month.

CONCLUSIONS

Overall, our study revealed the seasonal variation for Toxoplasma in using internet search data from GT, providing additional evidence on seasonal patterns in Toxoplasma.

INFECTION PRESSURE IS NECESSARY, BUT NOT SUFFICIENT BY ITSELF, TO EXPLAIN TOXOPLASMA GONDII SEROPREVALENCE IN INTERMEDIATE HOST SPECIES

Parasite infection pressure is suggested to be a strong driver of transmission within ecosystems. We tested if infection pressure drives seroprevalence in intermediate host species for Toxoplasma gondii. We defined Toxoplasma infection pressure to intermediate host species as the combined influence of cat abundance, environmental conditions, and its prevalence in the cat population. We sampled and tested 2 species of rodent and collated information on Toxoplasma seroprevalence in koalas, wallabies, kangaroos, and sheep. All species were sampled using equivalent methods, within a 2-yr period, and from adjacent regions of low and high Toxoplasma infection pressure. The seroprevalence of Toxoplasma in kangaroos scaled with infection pressure, but we observed no statistical difference in seroprevalence for any other species between these 2 regions. Within the region of low infection pressure, Toxoplasma seroprevalence did not differ between species. However, within the region of high Toxoplasma infection pressure, we observed large variation in seroprevalence between species. Our results demonstrate that infection pressure is not sufficient by itself, but merely necessary, to drive Toxoplasma seroprevalence in intermediate host species. Where Toxoplasma seroprevalence in an intermediate host species is already low, further reducing infection pressure will not necessarily further decrease seroprevalence in those species. This has important ramifications for the mitigation of parasite infections and suggests that reductions in Toxoplasma infection pressure, intended to reduce infections, may be most effective and applicable to species that are known to experience high rates of infection.

Pathophysiological Aspects of Ocular Toxoplasmosis: Host-parasite Interactions

Purpose: This review aims to present the state of the art to understand the pathophysiology of ocular toxoplasmosis (OT), providing further foundations that would help to improve the future treatment and prognosis of this potentially blinding disease.Methods: A thorough literature search was performed in PubMed database. An additional search was made in Google Scholar to complete the collected items.Results: Toxoplasma gondii ocular infection is one of the most frequent causes of posterior uveitis. Despite the ocular barriers, the parasite reaches the eye through different mechanisms. Once inside, it remains encysted livelong within the retina, and recurrences cannot be completely avoided. The complexity of host-parasite interactions, leading to the success of this parasite, encompasses host factors such as genetic predisposition, immune status, and age; and parasite factors such as strain diversity, virulence, phylogenetic origin, and geographical distribution. These factors influence the clinical presentation, course, and progression of the disease. Additional elements, such as pregnancy, eating behavior, and environmental, social, and cultural factors may also contribute to this complex balance.Conclusions: The host-parasite interaction in OT is a complex and multifactorial relationship, with the parasite always on the driving edge of the game. There are still multiple incompletely understood fields to be investigated. Future research would permit further insight into the immune-biology of the parasite and recognition of the host-parasite interplay to improve the diagnostic and management performance.

Toxoplasma gondii infection in white spoonbills (Platalea leucorodia) from Henan Province, China

Toxoplasma gondii oocysts in the environment are a threat to humans and animals. This study is aimed to evaluate the prevalence of T. gondii in white spoonbills and isolate viable T. gondii from white spoonbills. In 28.6% (2/7) of white spoonbills, T. gondii antibodies were found in heart juice by the modified agglutination test (cut-off: 1:4). T. gondii DNA was detected in tissues of 42.9% (3/7) white spoonbills. One viable T. gondii strain, named TgSpoonbillCHn1, was isolated from the myocardium of a white spoonbill by bioassay in mice. DNA extracted from TgSpoonbillCHn1 tachyzoites was characterized by PCR-restriction fragment length polymorphism with ten markers and the virulence genes ROP5 and ROP18. The results revealed that it was ToxoDB#2 (Type III). The ROP18/ROP5 genotype combination predicts that this strain is avirulent for mice, which is supported by the infection experiments in mice. This is the first report of the isolation of viable T. gondii strain from white spoonbil. The prevalence of T. gondii in white spoonbills may be indicative of environmental contamination of oocysts. This report provides direct evidence of white spoonbill as an intermediate host of T. gondii.

Azathioprine-induced toxoplasma gondii infection in a patient with Crohn's disease with NUDT15 variation: A case report

INTRODUCTION

Azathioprine (AZA) has been widely used for the treatment of various immune-related diseases and has become a mainstay in the treatment of inflammatory bowel disease. However, patients with genetic mutations may experience severe adverse events when treated with azathioprine. Most of the previous literature focused on the TPMP gene-related adverse reactions, herein, we report a case of Crohn's disease patient with nucleoside diphosphate-linked moiety X motif 15 gene (NUDT15) variation and wild-type TPMP gene who developed toxoplasma gondii infection after azathioprine treatment.

PATIENT CONCERNS

A 56-year-old Crohn's disease patient developed toxoplasma gondii infection within 2 months after the administration of azathioprine; however, he had no relevant high-risk factors.

DIAGNOSIS

Subsequent genetic testing revealed that the patient was heterozygous for NUDT15. Therefore, it was reasonable to consider that the patient's genetic mutation resulted in reduced tolerance to azathioprine, leading to low immunity and eventually toxoplasma infection.

INTERVENTIONS

AZA was then discontinued; after anti-infection, antipyretic and other supportive treatments were administered, the patient's condition gradually improved.

OUTCOMES

The patient was followed up at 1, 3, and 6 months after discharge; fortunately, he was in good health.

CONCLUSION

We report a case of Crohn's disease in a patient who developed severe pneumonia caused by toxoplasma gondii infection due to the administration of AZA, with normal TPMP gene but NUDT15 gene mutation. This indicates that NUDT15 variation may contribute to severe adverse events in patients treated with azathioprine, and we suggest that NUDT15 genotype be detected before the use of azathioprine in order to provide personalized therapy and reduce side effects.

Recent epidemiologic, clinical, and genetic diversity of Toxoplasma gondii infections in non-human primates

Toxoplasma gondii infections are common in humans and animals worldwide. The present review summarizes worldwide information on the prevalence of clinical and subclinical infections, epidemiology, diagnosis, and genetic diversity of T. gondii in non-human primates (NHP) for the past decade. Seroprevalence estimates of T. gondii worldwide were tabulated for each host. Risk factors associated with T. gondii infections are evaluated. New World NHP in captivity are highly susceptible to T. gondii infection with high mortality associated with disseminated toxoplasmosis. T. gondii can be transmitted to NHP in contact with symptomatic NHP. Therefore, precautions should be taken to prevent transmission of T. gondii to humans while handling symptomatic NHP. There were no reports of clinical toxoplasmosis in Old World NHP. Among the different genera of New World NHP, susceptibility to clinical toxoplasmosis varies a great deal; however, factors affecting this susceptibility are not fully understood. Genetic characteristics of T. gondii strains from monkeys is summarized.

Rosuvastatin revert memory impairment and anxiogenic-like effect in mice infected with the chronic ME-49 strain of Toxoplasma gondii

The aim of this study was to investigate the effect of rosuvastatin treatment on memory impairment, and anxiogenic-like effects in mice chronically infected with Toxoplasma gondii. For this, Balb/c mice were infected orally with chronic ME-49 strain of Toxoplasma gondii. Oral treatment with rosuvastatin (40mg/kg/day) started on the 51^st day post-infection and was performed daily for 21 days. After completion of treatment, anxiety-like effects and locomotion were investigated in the open field (OF) test, whereas novel object recognition (NOR) test was used for evaluation of short- and long-term memory. At the end of the experiments, the brain was collected for Toxoplasma gondii DNA quantification and histopathological analysis. Infection with ME-49 strain decreased the time spent in the center of OF, indicating an anxiogenic effect, without affecting total and peripheral locomotion. Rosuvastatin treatment inhibited the change in the center time. Besides, pharmacological treatment increased total and central locomotion in both non-infected and infected animals. Infection also impaired both short- and long-term memory in the NOR test, and these effects were reverted by rosuvastatin treatment. In addition to effects in behavioral changes, rosuvastatin also reduced parasite load in the brain and attenuated signs of brain inflammation such as perivascular cuffs, inflammatory cell infiltration and tissue damage. These findings indicate for the first time the efficacy of rosuvastatin in treatment of memory impairment and anxiogenic effect evoked by infection with Toxoplasma gondii. These effects might be mediated by reduced cyst load, which in turn decrease inflammation and damage in the brain.

Toxoplasma gondii infection in wild boars (Sus scrofa) from the State of São Paulo, Brazil: Serology, molecular characterization, and hunter's perception on toxoplasmosis

The consumption of wild boar meat, common in many countries, became popular in Brazil after the hunting of these animals was authorized in 2013. The meat of these animals is often consumed by hunters and their social groups, and their offal is occasionally used as supplemental food in the diet of hunting dogs. Given the high frequency of foodborne diseases related to wild boar meat consumption in other countries, including toxoplasmosis, knowledge on these diseases is essential for risk assessment and elaboration of education campaigns for the exposed public. Thus, this study aimed diagnosing, isolating, and genotyping Toxoplasma gondii in hunted wild boars. For that, we obtained samples of serum and tissues (brain, tongue, diaphragm, and heart) from 26 wild boar hunted in three areas in São Paulo State, Brazil, based on convenience sampling strategy. The serum samples were submitted to the indirect immunofluorescence reaction test (IFAT) test while the tissue samples (n = 22) were used to perform a bioassay in mice to isolate the parasite. The isolated samples were genetically characterized by PCR-RFLP with SAG1, 5' and 3' SAG2, alt.SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico markers. Questionnaires were also formulated and applied to wildlife hunters to assess knowledge about toxoplasmosis. The seroprevalence of T. gondii was 76.9% (20/26), with titers ranging from 16 to 1024. Viable parasites accounted for 4.5% (1/22) of the samples. The ToxoDB #6 genotype of TgJava1 alone was detected. Most interviewed hunters, 84.2% (16/19) consume game meat and a few of them (15.7%; 3/19) prefer undercooked meat. Also, 15.7% (3/19) of the hunters reported supplementing their hunting dogs' diet with wild boar meat and/or offal. As antibodies to T. gondii were detected in 76.9% (20/26) of the studied wild boars, we concluded that infection by T. gondii is frequent in wild boars used for human and animal consumption in the studied areas. Although genotype #6 is commonly found in Brazil in domestic animals, wild animals, and humans, causing everything from mild clinical symptoms to death, this study found, for the first time, the detection of this genotype in wild boars. These results also reaffirm the importance of these animals as a possible source of T. gondii infection for humans and domestic animals.

A hotspot of Toxoplasma gondii Africa 1 lineage in Benin: How new genotypes from West Africa contribute to understand the parasite genetic diversity worldwide

Through international trades, Europe, Africa and South America share a long history of exchanges, potentially of pathogens. We used the worldwide parasite Toxoplasma gondii to test the hypothesis of a historical influence on pathogen genetic diversity in Benin, a West African country with a longstanding sea trade history. In Africa, T. gondii spatial structure is still non-uniformly studied and very few articles have reported strain genetic diversity in fauna and clinical forms of human toxoplasmosis so far, even in African diaspora. Sera from 758 domestic animals (mainly poultry) in two coastal areas (Cotonou and Ouidah) and two inland areas (Parakou and Natitingou) were tested for T. gondii antibodies using a Modified Agglutination Test (MAT). The hearts and brains of 69 seropositive animals were collected for parasite isolation in a mouse bioassay. Forty-five strains were obtained and 39 genotypes could be described via 15-microsatellite genotyping, with a predominance of the autochthonous African lineage Africa 1 (36/39). The remaining genotypes were Africa 4 variant TUB2 (1/39) and two identical isolates (clone) of Type III (2/39). No difference in terms of genotype distribution between inland and coastal sampling sites was found. In particular, contrarily to what has been described in Senegal, no type II (mostly present in Europe) was isolated in poultry from coastal cities. This result seems to refute a possible role of European maritime trade in Benin despite it was one of the most important hubs during the slave trade period. However, the presence of the Africa 1 genotype in Brazil, predominant in Benin, and genetic analyses suggest that the triangular trade was a route for the intercontinental dissemination of genetic strains from Africa to South America. This supports the possibility of contamination in humans and animals with potentially imported virulent strains.

The parasite Toxoplasma gondii is a worldwide-distributed pathogen, able to infect all warm-blooded animals. There are important differences in the clinical expression of the infection in direct relation with the parasite genetic profile. In some regions, the geographical structuration of its genetic diversity points towards a crucial role of human activities in some lineages introduction or sorting. Benin is a West African country with a history of extensive transcontinental exchanges. Our genetic study of Toxoplasma in Benin shows a surprisingly homogeneous and autochthonous diversity, which contrasts with previous studies from other West and Central African countries. In Benin, the absence of European Toxoplasma lineages may be explained by the extreme rarity of the house mouse (Mus musculus), a host species that was previously described as highly susceptible to the mouse-virulent African strains. Might Benin be the origin region for the Africa 1 lineage, our results suggest that Guinean Gulf coasts may be a starting point of this lineage towards South America, especially Brazil, during the slave trade. As a whole, the present study provides further insights into the recent evolutionary history of Toxoplasma gondii and its consequences on human and animal health.

Molecular prevalence, risk factors and genotypes of Toxoplasma gondii DNA in wild marine snails collected from offshore waters in eastern China

Increasing evidence exisits for the role that shellfish play in the epidemiology of Toxoplasma gondii in marine environment. However, limited information is available on the level of T. gondii infection in wild marine snails, which can play a role in the transmission of T. gondii to other marine organisms and humans. In this study, the prevalence of T. gondii DNA in wild marine snails collected from three coastal cities in China was determined. Between January 2018 and November 2019, 1,206 wild marine snails were randomly collected and examined for the presence of T. gondii DNA using a nested polymerase chain reaction (PCR) targeting T. gondii B1 gene. The amplified products were genotyped using multilocus PCR-restriction fragment length polymorphism analysis. We also examined whether species of snail, sampling region, sampling season, surface runoff near samplic site, residential water discharge near samplic site, and proximity to livestock farms are associated with the occurrence of T. gondii DNA in marine snails. Our results showed that 23 (1.91%) snails were positive for T. gondii B1 gene. The genotype of two of the 23 T. gondii amplicons was consistent with ToxoDB Genotype #9. Multiple logistic regression revealed that surface runoff near the sampling site (P = 0.039, odds ratio [OR] = 3.413, 95% confidence interval [CI]: 1.07-10.94) and residential water discharge near the sampling site (P = 0.021, OR = 3.990, 95%CI: 1.24-12.87) are more likely to be associated with the presence of T. gondii DNA in marine snails. The detection of T. gondii DNA in marine snails in China highlights the potential impact of the anthropogenic activities on marine organisms and the potential foodborne risk posed to humans with such an important terrestrial pathogen.

Models in parasite and pathogen evolution: Genomic analysis reveals predominant clonality and progressive evolution at all evolutionary scales in parasitic protozoa, yeasts and bacteria

The predominant clonal evolution (PCE) model of pathogenic microorganisms postulates that the impact of genetic recombination in those pathogens' natural populations is not enough to erase a persistent phylogenetic signal at all evolutionary scales from microevolution till geological times in the whole ecogeographical range of the species considered. We have tested this model with a set of representative parasitic protozoa, yeasts and bacteria in the light of the most recent genomic data. All surveyed species, including those that were considered as highly recombining, exhibit similar PCE patterns above and under the species level, from macro- to micro-evolutionary scales (Russian doll pattern), suggesting gradual evolution. To our knowledge, it is the first time that such a strong common evolutionary feature among very diverse pathogens has been evidenced. The implications of this model for basic biology and applied research are exposed. These implications include our knowledge on the pathogens' reproductive mode, their population structure, the possibility to type strain and to follow up epidemics (molecular epidemiology) and to revisit pathogens' taxonomy through a flexible use of the phylogenetic species concept (Cracraft, 1983).