Antibody frequency for Toxoplasma gondii and Neospora spp. in domiciliated and stray cats from Araguaína, Tocantins, Eastern Amazonia

Toxoplasma gondii and Neospora spp. are protozoa that have a significant impact on animal health due to the diseases they cause in domestic and wild animals. The aim of the present study was to investigate the presence of antibodies against T. gondii and Neospora spp. in cats from northern Brazil. Serum samples were collected from 180 cats in the municipality of Araguaína, Tocantins and used to evaluate the presence of anti-T. gondii and anti-Neospora spp. antibodies using the indirect fluorescent antibody test, with a cutoff of 1:64 and 1:25, respectively. The association between infection and individual animal characteristics (age, sex, origin, breed, and clinical signs) was tested using univariate analysis, followed by multivariate logistic regression. We found that 48.3% (87/180) of the animals had anti-T. gondii (95% CI: 40.8%–55.90%) and 3.9% (7/180) had anti-Neospora spp. (95% CI: 1.6%–7.8%) antibodies. There was no association between age, sex, breed origin, clinical signs, and seropositivity for T. gondii. Cats of defined breeds were more likely to be infected by Neospora spp. (OR = 10.7). Therefore, we found a high rate of seropositivity for T. gondii and a high rate of occurrence of Neospora infections in cats from the Araguaína region. The exposure of the feline population to the studied coccidia indicates the need to monitor the feline population for these infections and underscores the importance of effective sanitary measures against such pathogens.

Secondary Structure and X-ray Crystallographic Analysis of the Glideosome-Associated Connector (GAC) from Toxoplasma gondii

A model for parasitic motility has been proposed in which parasite filamentous actin (F-actin) is attached to surface adhesins by a large component of the glideosome, known as the glideosome-associated connector protein (GAC). This large 286 kDa protein interacts at the cytoplasmic face of the plasma membrane with the phosphatidic acid-enriched inner leaflet and cytosolic tails of surface adhesins to connect them to the parasite actomyosin system. GAC is observed initially to the conoid at the apical pole and re-localised with the glideosome to the basal pole in gliding parasite. GAC presumably functions in force transmission to surface adhesins in the plasma membrane and not in force generation. Proper connection between F-actin and the adhesins is as important for motility and invasion as motor operation itself. This notion highlights the need for new structural information on GAC interactions, which has eluded the field since its discovery. We have obtained crystals that diffracted to 2.6–2.9 Å for full-length GAC from Toxoplasma gondii in native and selenomethionine-labelled forms. These crystals belong to space group P212121; cell dimensions are roughly a = 119 Å, b = 123 Å, c = 221 Å, α = 90°, β = 90° and γ = 90° with 1 molecule per asymmetric unit, suggesting a more compact conformation than previously proposed

SAG3 Toxoplasma gondii cloning reveals unexpected fivefold infection in the blood of feral cats in the Mexican Caribbean

Background Currently, more than 300 genotypes of Toxoplasma gondii (T. gondii) have been described throughout the world, demonstrating its wide genetic diversity. The SAG3 locus is one of the genes included in the genotyping panel of this parasite. It is associated with its virulence since it participates during the invasion process of the host cells. Therefore, cloning, sequencing, and bioinformatic analysis were used to deepen the understanding of the SAG3 locus genetic diversity of T. gondii in blood samples from feral cats. Results Six different SAG3 sequences were detected, five of which were detected in one feline. Three sequences were first reported here; one of them was an intragenic recombinant. In the cladogram, four out of ten SAG3 sequences did not share nodes with others reported worldwide. Conclusions Cloning and sequencing of samples with more than one restriction pattern by PCR-RFLP were very helpful tools to demonstrate the presence of more than three genotypes of T. gondii in the blood of feral cats from southeastern Mexico. This suggests a potential mixed infection of multiple T. gondii strains and high genetic diversity of the parasites in felines in this tropical region of Mexico.

Novel Data About Unusual Location of Toxoplasma Gondii Within Active Microbial Community in the Anterior Chamber of the Eye of Egyptian Rural Children

In Egypt, many cases of granulomatous anterior uveitis consisting of single or multiple gelatinous nodules were detected in children living in rural areas. These lesions are believed to be waterborne and were previously attributed to flatworms ‘stage, showing some improvement after antiparasitic treatment. In a trial to explore the nature of these ocular lesions among rural Egyptian children, twenty surgically excised ocular lesions were subjected to transmission electron microscopy (TEM) examination. TEM results were combined with previous results of the metagenomic analysis performed for four cases out of the twenty samples, revealing the presence of Toxoplasma gondii (T. gondii), besides, a wide range of microbial communities, including variable species of fungi, bacteria, and archaea. The excised lesions ranged from 1 to 5 mm in size and demonstrated an extensive inflammatory cellular infiltrate. Using TEM, five out of twenty samples revealed active eukaryotic organisms with intact energetic cellular organelles, besides, numerous nuclei encircled within a syncytial layer and enclosed by a hyaline layer rich in mitochondria. Six samples showed inactivity in the cellular and the covering portions, while just inflammatory reaction was seen in the remaining nine samples. Toxoplasma gondii was found free within the distal part of the syncytium while, the proximal part showed the active synthesis of possibly extra polymeric substance, perhaps secreted by the microbial community. In a conclusion, Toxoplasma gondii has been detected among a microbial community in an atypical lesion in the eye. Further studies need to be sustained on genotype characterization, proteomic analysis, besides, the aquatic transmission of these mixed microbial species to the ocular tissues to clarify the reason behind such ocular illness.

Depletion of Intracellular Glutamine Pools Triggers Toxoplasma gondii Stage Conversion in Human Glutamatergic Neurons

Toxoplasma gondii chronically infects the brain as latent cysts containing bradyzoites and causes various effects in the host. Recently, the molecular mechanisms of cyst formation in the mouse brain have been elucidated, but those in the human brain remain largely unknown. Here, we show that abnormal glutamine metabolism caused by both interferon-γ (IFN-γ) stimulation and T. gondii infection induce cyst formation in human neuroblastoma cells regardless of the anti-T. gondii host factor nitric oxide (NO) level or Indoleamine 2,3-dioxygenase-1 (IDO1) expression. IFN-γ stimulation promoted intracellular glutamine degradation in human neuronal cells. Additionally, T. gondii infection inhibited the mRNA expression of the host glutamine transporters SLC38A1 and SLC38A2. These dual effects led to glutamine starvation and triggered T. gondii stage conversion in human neuronal cells. Furthermore, these mechanisms are conserved in human iPSC-derived glutamatergic neurons. Taken together, our data suggest that glutamine starvation in host cells is an important trigger of T. gondii stage conversion in human neurons.

Ionophore-stimulation promotes re-organization of the invasion machinery of Toxoplasma gondii

Host cell invasion by intracellular, eukaryotic parasites, like the many important species within the phylum Apicomplexa, is a remarkable and active process involving the coordinated action of many apical organelles and other structures. To date, capturing how these various structures interact during invasion has been difficult to observe in detail. Here, we used cryogenic electron tomography to generate images of the apical complex of Toxoplasma gondii tachyzoites under conditions that mimic resting parasites and those primed to invade through addition of a calcium ionophore. Using AI-based image-processing we were able to annotate 48 tomograms to identify and extract densities of the relevant subcellular organelles and accurately analyze features in 3D. We describe an interaction between an anteriorly located apical vesicle and a rhoptry tip that occurs only in the ionophore-stimulated parasites and that is associated with dramatic changes in the vesicle's shape in what appears to be a stalled fusion event. We also present information to support the presumption that this vesicle originates from the well-described vesicles that parallel the intraconoidal microtubules and that the latter two structures are linked by a novel tether. Lastly, we show that a previously described rosette is found associated with more than just the anterior-most apical vesicle, indicating that multiple such vesicles are primed to enable rhoptry secretion.

A Toxoplasma gondii Oxopurine Transporter Binds Nucleobases and Nucleosides Using Different Binding Modes

Toxoplasma gondii is unable to synthesize purines de novo, instead salvages them from its environment, inside the host cell, for which they need high affinity carriers. Here, we report the expression of a T. gondii Equilibrative Nucleoside Transporter, Tg244440, in a Trypanosoma brucei strain from which nucleobase transporters have been deleted. Tg244440 transported hypoxanthine and guanine with similar affinity (Km ~1 µM), while inosine and guanosine displayed Ki values of 4.05 and 3.30 µM, respectively. Low affinity was observed for adenosine, adenine, and pyrimidines, classifying Tg244440 as a high affinity oxopurine transporter. Purine analogues were used to probe the substrate-transporter binding interactions, culminating in quantitative models showing different binding modes for oxopurine bases, oxopurine nucleosides, and adenosine. Hypoxanthine and guanine interacted through protonated N1 and N9, and through unprotonated N3 and N7 of the purine ring, whereas inosine and guanosine mostly employed the ribose hydroxy groups for binding, in addition to N1H of the nucleobase. Conversely, the ribose moiety of adenosine barely made any contribution to binding. Tg244440 is the first gene identified to encode a high affinity oxopurine transporter in T. gondii and, to the best of our knowledge, the first purine transporter to employ different binding modes for nucleosides and nucleobases.

The Screening of Rubella Virus, Cytomegalovirus, Hepatitis B Virus, and Toxoplasma gondii Antibodies in Prepregnancy and Reproductive-Age Women in Tabriz, Iran

Objectives. The organisms of Toxoplasma gondii, Rubella virus, Cytomegalovirus, and Herpes simplex virus as an acronym of TORCH are major pathogens in prepregnancy and reproductive-age women. These microorganisms are considered a serious problem and cause 2-3% of all birth defects in the fetus. Our study was aimed at screening the seroprevalence of TORCH antibodies among prepregnancy and reproductive-age women in Tabriz, Iran. Design and Setting. This study was carried out in 2726 prepregnancy and reproductive-age women, who were referred to the laboratory for prenatal TORCH screening. To detect the presence of IgG, IgM antibodies and Hepatitis B surface antigen against these microorganisms were carried out using a chemiluminescence immunoassay analyzer (CLIA). Results. In the current study, the rates of anti-Toxoplasma gondii IgG, anti-Rubella virus IgG, and anti-Cytomegalovirus IgG were found in 722 cases (26.5%), 2579 cases (94.6%0), and 2718 cases (99.7%), respectively. Moreover, the rates of anti-Toxoplasma gondii IgM, anti-Rubella virus IgM, and anti-Cytomegalovirus IgM were discovered in 10 cases (0.4%), 13 cases (0.5%), and 16 cases (0.6%), respectively. The Hepatitis B surface antigen was found in 32 cases (1.2%). The dissemination of positive TORCH in various ages was different ( P < 0.05 ). Conclusions. In our study, the seroprevalence of acute TORCH infections was relatively low. Due to the probability of vertical transmission to the fetus during pregnancy and the unpleasant complication of these pathogens, it is essential to be screened for detection of specific IgG and IgM antibodies in reproductive ages.