Toxoplasma gondii induces robust humoral immune response against cyst wall antigens in chronically infected animals and humans

Effective factors in the pathogenesis of Toxoplasmagondii

Toxoplasma gondii (T. gondii) is a cosmopolitan protozoan parasite in humans and animals. It infects about 30 % of the human population worldwide and causes potentially fatal diseases in immunocompromised hosts and neonates. For this study, five English-language databases (ScienceDirect, ProQuest, Web of Science, PubMed, and Scopus) and the internet search engine Google Scholar were searched. This review was accomplished to draw a global perspective of what is known about the pathogenesis of T. gondii and various factors affecting it. Virulence and immune responses can influence the mechanisms of parasite pathogenesis and these factors are in turn influenced by other factors. In addition to the host's genetic background, the type of Toxoplasma strain, the routes of transmission of infection, the number of passages, and different phases of parasite life affect virulence. The identification of virulence factors of the parasite could provide promising insights into the pathogenesis of this parasite. The results of this study can be an incentive to conduct more intensive research to design and develop new anti-Toxoplasma agents (drugs and vaccines) to treat or prevent this infection. In addition, further studies are needed to better understand the key agents in the pathogenesis of T. gondii.

Beyond schistosomiasis: unraveling co-infections and altered immunity

Schistosomiasis is a neglected tropical disease caused by the helminth Schistosoma spp. and has the second highest global impact of all parasites. Schistosoma are transmitted through contact with contaminated fresh water predominantly in Africa, Asia, the Middle East, and South America. Due to the widespread prevalence of Schistosoma, co-infection with other infectious agents is common but often poorly described. Herein, we review recent literature describing the impact of Schistosoma co-infection between species and Schistosoma co-infection with blood-borne protozoa, soil-transmitted helminths, various intestinal protozoa, Mycobacterium, Salmonella, various urinary tract infection-causing agents, and viral pathogens. In each case, disease severity and, of particular interest, the immune landscape, are altered as a consequence of co-infection. Understanding the impact of schistosomiasis co-infections will be important when considering treatment strategies and vaccine development moving forward.

Serological and Molecular Detection of Toxoplasma gondii in Domestic Pigs Intended for Human Consumption and Potential Occupational Hazard to Pig Farmers in India

Toxoplasma gondii, an important food-borne zoonotic parasite, poses a worldwide public health hazard. Domestic pigs are considered one of the main intermediate hosts in the zoonotic transmission of T. gondii. To date, seroepidemiological information on T. gondii in domestic pigs in India is very scarce, and there are no reports of occupational hazards to pig farmers in this country. Here, we aimed at estimating the occurrence of T. gondii (antibodies and parasite DNA) in slaughtered pigs and pig farmers in Central India. Seroprevalence was determined in 410 serum samples from slaughtered pigs and 103 sera from pig farmers using an in-house prepared antigen-based modified agglutination test (MAT), enzyme-linked immunosorbent assay (ELISA), and indirect-fluorescent antibody test (IFAT). Anti-T. gondii IgG antibodies were detected in 200 pigs (up to 48.8%, confidence interval [95% CI]: 40.4-52.2) and 44 pig farmers (up to 42.7%, 95% CI: 35.6-47.3) using MAT, ELISA, and IFAT. Inter-rater agreement showed an excellent agreement (kappa κ = 0.9) among the different serological tests suggesting similar detection potential of these tests. Recently acquired infections in all seropositive subjects were determined using IgG avidity testing and polymerase chain reaction (PCR). IgG avidity showed that 20 (10.3%) of slaughtered pigs and 8 (19.5%) pig farmers had a recently acquired infection. PCR for B1 and 529 repeats was performed in the heart tissues of slaughtered pigs and the blood cells of pig farmers. T. gondii DNA was detected in 14 (7.2%) slaughtered pigs and 5 (12.2%) pig farmers. Univariate analysis revealed that adult animals (>1 year), cats and rodents on the farm, and outdoor access are common factors (p ≤ 0.05) associated with T. gondii infection in pigs. Our results indicate that T. gondii is widely distributed in slaughtered pigs and pig farmers at risk of infection, highlighting a potential zoonotic transmission and health risk to consumers.

Serological and molecular detection of Toxoplasma gondii and Neospora caninum in free-ranging rats from Nagpur, India

Toxoplasma gondii and Neospora caninum are cyst-forming coccidian parasites that infect both wild and domestic non-felids as intermediate hosts, with rodents serving as important reservoir hosts during their life cycles. This study was aimed at investigating T. gondii and N. caninum infections and identifying factors favouring T. gondii infection in free-ranging rats from India. A total of 181 rodents were trap-captured, and blood and brain samples were subsequently collected for serological and molecular examination of T. gondii and N. caninum. Antibodies against T. gondii and N. caninum were detected by MAT/NAT and IFAT in 13.8% (25/181) and 1.65% (3/181) of rodents, respectively. All three N. caninum samples positive by NAT/IFAT were also positive for ELISA, while for T. gondii, 19 of 25 MAT/IFAT positive samples were also positive for ELISA. The antibody titers (MAT/NAT/IFAT) of rodents seropositive for T. gondii ranged from 25 to 400, while those of rats seropositive for N. caninum ranged from 25 to 100. Also, using PCR, DNA from T. gondii (B1 gene) and N. caninum (NC5 gene) was found in 2.76% (5/181) of brain samples and 0.55% (1/181) of brain samples. All PCR positive samples were also seropositive. No mixed infections were observed in the serological and molecular detections. A Chi-square analysis revealed that older rats and rats living in urban areas are significantly associated with T. gondii infection; however, rodent species, gender, location, habitat types, and seasonality were statistically nonsignificant. Overall, this study demonstrated that T. gondii was widely distributed while N. caninum was less prevalent among free-ranging rats in the studied area.

Human neutrophil-like cells demonstrate antimicrobial responses to the chronic cyst form of Toxoplasma gondii

The protozoan parasite Toxoplasma gondii infects approximately 2.5 billion people worldwide. Infection induces a rapid dissemination of parasites throughout the body followed by the formation of lifelong cysts within neurons of the host brain. Both stages require a dynamic immune response comprised of both innate and adaptive cells. Neutrophils are a primary responding cell to acute infection and have been observed in the brain during murine chronic infection. Previous studies investigating human neutrophils found that invasion by Toxoplasma tachyzoites inhibits apoptosis of neutrophils, prolonging their survival under inflammatory conditions. Here, we demonstrate the differentiation of two distinct subsets following exposure of human neutrophil-like-cells (HNLC) to Toxoplasma cysts. In vitro stimulation and imaging studies show cyst-specific induction of cytokines and cyst clearance by HNLCs. Further testing demonstrates that aged HNLCs perform less phagocytosis of cysts compared to non-aged HNLCs. In conclusion, this study identifies a novel response of HNLCs to Toxoplasma cysts and may indicate a role for neutrophils in the clearance of cysts during human infection with Toxoplasma.

Animal Models for Toxoplasma gondii Infection

Toxoplasma gondii is an obligate intracellular protozoan parasite that commonly infects mammals and birds throughout the world. This protocol describes murine models of acute T. gondii infection, toxoplasmic encephalitis and toxoplasma retinochoroiditis. T. gondii infection in severe combined immunodeficient (SCID) mice, deficient in T and B cells, has allowed for the study of T cell-independent mechanisms of defense against intracellular organisms, as described here. The uracil auxotroph strain cps1-1 and temperature-sensitive mutant strains of T. gondii induce protection against challenge with virulent strains of the parasite. They have allowed studies of immunization and adoptive-transfer experiments. A protocol is provided for infection with these mutant strains. The EGS strain of T. gondii has the unique feature of spontaneously forming tissue cysts in cell culture. Dual fluorescent reporter stains of this strain have allowed the study of tachyzoite to bradyzoite transitions in vitro and in vivo. A protocol for in vitro and in vivo growth of this strain and tissue cyst isolation is provided. Genetic manipulation of T. gondii and mice has led to the development of parasites that express fluorescent proteins as well as mice with fluorescently labeled leukocytes. This together with the use of T. gondii that express model antigens and transgenic mice that express the appropriate T cell receptor have facilitated the in vivo study of parasite host-interaction. In addition, parasites that express bioluminescent markers have made it possible to study the dynamics of infection in real time using bioluminescence imaging. Support protocols present methodology for evaluation of progression of infection and immune response to the parasite that includes these newer methodologies. In addition, support protocols address the maintenance of T. gondii tissue cysts and tachyzoites, as well as preparation of T. gondii lysate antigens. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Induction of acute T. gondii infection in mice Basic Protocol 2: Model of toxoplasmic encephalitis and toxoplasma retinochoroiditis in chronically infected mice Basic Protocol 3: Assessment of T. gondii invasion into neural tissue Basic Protocol 4: T. gondii infection in scid/scid (SCID) mice Basic Protocol 5: Infection with the uracil auxotroph strain CPS1-1 or the temperature-sensitive TS-4 strain of T. gondii Basic Protocol 6: In vivo and in vitro maintenance of the EGS strain of T. gondii Support Protocol 1: Assessment of progression of infection and immune response to T. gondii Support Protocol 2: Maintenance of a bank of T. gondii cysts of the ME49 strain Support Protocol 3: Maintenance of T. gondii tachyzoites using human foreskin fibroblasts Support Protocol 4: Maintenance of T. gondii tachyzoites in mice Support Protocol 5: Preparation of T. gondii lysate antigens Support Protocol 6: Isolation of T. gondii tissue cysts from brain.

Tryptophan metabolism and immune alterations in pregnant Hispanic women with chronic Toxoplasma gondii infection

PROBLEM

Pregnancy markedly modifies women's metabolism and immune functions. We hypothesized that pregnancy might alter the immune and metabolic responses to chronic Toxoplasma gondii infection in pregnancy.

METHOD OF STUDY

A population of 690 pregnant Hispanic women were screened for antibodies to T. gondii and 158 women were positive (23% positivity) with 83% showing high avidity indices. These seropositive women were followed through their pregnancies with four data collection time points and a postpartum collection at two clinics in Tampa, Florida. A T. gondii seronegative group (N = 128) was randomly selected to serve as a control group and measured along pregnancy in the same way. Serum levels of tryptophan, kynurenine, and their ratio, phenylalanine, tyrosine and their ratio, neopterin, and nitrite were measured through pregnancy and the postpartum. A plasma cytokine panel (IFN-γ, TNFα, IL-2, IL-10, IL-12, IL-6, IL-17) was analyzed in parallel.

RESULTS

The major findings suggest that indoleamine 2,3-dioxygenase (IDO-1) was less activated in T. gondii seropositive pregnant Hispanic women with chronic infection. Evidence for IDO-1 suppression was that tryptophan catabolism was less pronounced and there were lower levels of multiple inflammatory cytokines including IFN-γ, which is the major inducer of IDO-1, and higher nitrite concentration, a surrogate marker for nitric oxide, an inhibitor of IDO.

CONCLUSIONS

Latent T. gondii infection was associated with higher plasma tryptophan levels, and lower inflammatory cytokines across pregnancy, suggesting suppression of the IDO-1 enzyme, and possible T cell exhaustion during pregnancy.

Assessing and Prioritizing Zoonotic Diseases in Punjab, India: A One Health Approach

Zoonotic diseases have a significant impact on both human and animal health globally. The present study was planned to prioritize the zoonoses in Punjab state of India. To develop a zoonotic disease prioritization scoring system, a comprehensive approach has been taken, including literature review, key person interviews with animal health experts (n = 12) and medical professionals (n = 7), and nine focus group discussions (FGDs) with veterinary academicians, medical professionals, and field veterinary doctors. The scoring system comprises of seven major criteria, each assigned a weightage score (ws): prevalence/incidence of the disease (ws = 0.20), severity of illnesses in humans (ws = 0.18), epidemic potential (ws = 0.16), socio-economic burden (ws = 0.16), availability of effective control and prevention measures (ws = 0.15), inter-sectoral collaborations (ws = 0.1), and bioterrorism potential (ws = 0.05). The finalized scoring system, accompanied by a list of 15 selected zoonotic diseases, was implemented among a group of 23 professionals engaged in zoonoses research (n = 7), animal health (n = 10), and medical health (n = 6) to determine their prioritization. The zoonotic diseases prioritized for the Punjab (India) included, Brucellosis (0.70) > Rabies (0.69) > Anthrax (0.64) > Leptospirosis (0.62) = Toxoplasmosis (0.62) = Highly Pathogenic Avian Influenza (HPAI) (0.62) > Bovine tuberculosis (0.61) > Q fever (0.60) > Cysticercosis (0.59) > Listeriosis (0.58) > Crimean-Congo haemorrhagic fever (CCHF) (0.57) > Japanese encephalitis (0.56) = Echinococcosis (0.56) > Dermatophytosis (0.53) > and Scrub typhus (0.48), respectively. Higher priority is suggested for endemic zoonoses (e.g., brucellosis and rabies) as compared to those with epidemic potential (e.g., CCHF, HPAI etc.) in Punjab. Results of the current study will help in the development of targeted control and prevention strategies for zoonotic diseases in Punjab and other geographical regions facing similar challenges.

Seroprevalence of Toxoplasma gondii infection in sheep and goats from different geographical regions of the world: Systematic review and meta-analysis

The Toxoplasma gondii is an obligate intracellular protozoan parasite which significantly impact small ruminant productivity, international animal trade and transboundary movement of animal across the globe. The seroprevalence of T. gondii infection (toxoplasmosis) in sheep and goats is widely studied in many parts of the world and there is a lack of comprehensive information on prevalence estimates considering the global and regional perspectives. The aim of the study was to use systematic review and meta-analysis methods to estimate the global and regional pooled seroprevalence of T. gondii infection in sheep and goats, as well as factors that influence prevalence estimations. Relevant articles reporting the seroprevalence of toxoplasmosis in sheep and/goats were searched in five electronic databases, including PubMed, Web of Science, Scopus, Embase and ProQuest. After the publications were checked to verify they fit the inclusion criteria, a total of 225 articles were included in the systematic review and meta-analysis, reflecting data from 70 countries/regions. The pooled prevalence was estimated using a random effect meta-analysis model. Overall, the seroprevalence of T. gondii infection was 33.86% (95% CI: 30.47-37.25%) in sheep and 31.78% (95% CI: 28.99-34.58%) in goats, with significant variation in prevalence estimates across geographical locations (p < .001). Substantial heterogeneity (I²  > 75%) was observed in most pooled seroprevalence estimates. The T. gondii infection in global sheep and goat population showed uptrend over the period. This information would be useful for epidemiologist, health authorities and farmers in order to plan future T. gondii survey and infection management strategies both locally and internationally.

The role of Toxoplasma TFIIS-like protein in the early stages of mRNA transcription

BACKGROUND

The mRNA transcription is a multistep process involving distinct sets of proteins associated with RNA polymerase II (RNAPII) through various stages. Recent studies have highlighted the role of RNAPII-associated proteins in facilitating the assembly of functional complexes in a crowded nuclear milieu. RNAPII dynamics and gene expression regulation have been primarily studied in model eukaryotes like yeasts and mammals and remain largely unchartered in protozoan parasites like Toxoplasma gondii, where considerable gene expression changes accompany stage differentiations. Here we report a key modulator of RNAPII activity, TFIIS in Toxoplasma gondii (TgTFIIS).

METHODS

A Pull-down assay demonstrated that TgTFIIS binds to RNAPII subunit TgRPB1. Truncation mutants of TFIIS help us define the regions critical for its binding to TgRPB1. Co-immunoprecipitation analysis confirmed the interaction between the native TgTFIIS and TgRPB1. Confocal microscopy revealed a predominantly nuclear localization. Native TgTFIIS was able to bind promoter DNA which was consistent with the CHIP results.

RESULTS

TgTFIIS complements initiation defects in yeast mutants, and the regions implicated in RNAPII binding appeared essential for this function. Interestingly, the C-terminal zinc finger domain necessary for its potential elongation function is dispensable for TgRPB1 binding. TgTFIIS was found to be associated with the promoter region along with its association with the ORF on an RNAPII transcribed gene.

CONCLUSION

The observations were in line with the potential role of TgTFIIS in early events of RNAPII transcription in addition to elongation.

GENERAL SIGNIFICANCE

The study elucidates the potential role of RNAPII-associated proteins in multiple steps of transcription.

A functionally divergent transcription elongation factor 1-like protein in Toxoplasma gondii

Zinc ribbons, one of the largest fold groups among zinc fingers, often include proteins involved in the transcription machinery. Here, we identify and characterize one such zinc ribbon-bearing protein in the apicomplexan parasite Toxoplasma gondii, annotated as putative transcription elongation factor 1 (ELF1), with predicted functions in transcription and chromatin maintenance. We show that this ELF1 homolog, referred to as T. gondii ELF1-like divergent (TgELD), is expressed in both tachyzoite and bradyzoite developmental stages. TgELD associates with the cytoskeleton in the tachyzoites, while it transiently becomes a part of the cyst wall in the early bradyzoites, followed by a cytosolic and peripheral localization in late bradyzoites. TgELD is phosphorylated by a casein kinase 2-like protein, which has potential implications for its localization and function in the parasite.

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.

Seroprevalence and associated risk factors of Toxoplasma gondii and Neospora caninum infections in cattle in Central India

Toxoplasma gondii and Neospora caninum are closely related cyst-forming parasites identified as important causes of reproductive failures in ruminants. While these parasites have been reported worldwide, seroprevalence and associated risk factors for cattle infections have not been determined in India. A total of 576 serum samples of cattle were analyzed for antibodies to T. gondii and N. caninum using enzyme-linked immunosorbent assay (ELISA), modified/Neospora agglutination test (MAT/NAT), and an indirect fluorescent antibody test (IFAT-tachyzoite and bradyzoite). Additionally, general information about cattle, movement of cats and dogs, the menace of rodents, management, and reproductive disorders were assessed to identify the potential risk factors. Overall, 32.9% (190/576) serum samples reacted positively to T. gondii and 24.8% (143/576) to N. caninum. The performance of the diagnostic tests showed excellent agreement between IFAT and ELISA (kappa [κ] = 0.98) and between MAT/NAT and ELISA (κ = 0.97). Combining both infections on avidity test, 94% sera had high-IgG avidity, and 3% had low-IgG avidity antibodies, indicating chronic infection in the majority of the cases. The identified risk factors (p < 0.05) for exposure to T. gondii were: increasing age (Odds Ratio [OR]: 2.02), movement of cat (OR: 4.8) and rodents (OR: 1.57) in the farm; and for N. caninum: increasing age (OR: 1.6), movement of dogs in the farm (OR: 2.07), drinking pond water (OR: 1.64) and abortion (OR: 1.82). These findings revealed that T. gondii and N. caninum infections are widespread in the study area and suggest conducting nationwide epidemiological studies owing to their economic importance.

Seroprevalence and risk factors of Toxoplasma gondii infection among veterinary personnel and abattoir workers in Central India

Toxoplasmosis, caused by the protozoan parasite Toxoplasma gondii, is an important zoonotic infection. Veterinary personnel and abattoir workers are considered to be at a high risk of T. gondii infection owing to their occupational exposure. However, the association of T. gondii infection with occupational exposure to animals has not been determined in India. Hence, we analysed 139 and 126 blood samples of veterinary personnel and abattoir workers, respectively, for anti-T. gondii antibodies using enzyme-linked immunosorbent assay (ELISA), modified agglutination test (MAT) and indirect fluorescent antibody test (IFAT). The association of seroprevalence with sociodemographic profiles, work activities and dietary habits was determined in the study population. MAT, ELISA and IFAT results demonstrated nearly 46%, 48% and 47% seropositivity, respectively. MAT (kappa = 0.924) and IFAT (kappa = 0.962) results showed good agreement with ELISA results. Of the ELISA positive samples, 46% was copositive for IgG antibody, 1.5% for IgM antibody and 1.5% for both IgG and IgM antibodies. High IgG avidity was observed only in IgG+ IgM- and IgG+ IgM+ samples and not in IgM+ IgG- samples, indicating chronic T. gondii infection in most of the cases. Furthermore, multivariate analysis revealed that T. gondii seropositivity was associated with age > 30 years (odds ration [OR] = 1.992), cat at home (OR = 1.991), not wearing gloves (OR = 1.886), not wearing safety glasses (OR = 1.985) and contact with soil (OR = 1.695). These findings support the presence of a potentially significant association between T. gondii seropositivity and occupational exposure to animals.

An Extracellular Matrix-Based Signature Associated With Immune Microenvironment Predicts the Prognosis and Therapeutic Responses of Patients With Oesophageal Squamous Cell Carcinoma

Evidence has suggested that the cancer-associated extracellular matrix (ECM) could be recognised as immune-related biomarkers that modulate tumour progression and expansion. However, the ECM-associated immune effect on esophageal squamous cell carcinoma (ESCC) prognosis and therapy has not been well characterised. In our study, we first constructed an ECM-related signature including four genes CST1, NELL2, ADAMTSL4, and ANGPTL7 by multivariate Cox regression analyses. This signature could serve as a marker to evaluate the prognosis of patients with ESCC and was successfully validated in testing and combined (training plus testing) cohorts. We also found that there were significant different therapeutic responses to chemotherapy and targeted drugs between the high-risk and low-risk groups of patients defined by the signature. Furthermore, the expression of four genes and immune function analysis suggested that this ECM-related signature gene might play important roles in the changes of the tumour microenvironment. In conclusion, our findings demonstrated that the ECM-related signature might serve as an independent prognostic factor and provide a potential biomarker for chemotherapy responses for patients with ESCC.