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Sexual development in Toxoplasma gondii is a multistep process that culminates in the production of oocysts, constituting approximately 50% of human infections. However, the molecular mechanisms governing sexual commitment in this parasite remain poorly understood. Here, we demonstrate that the transcription factors AP2XI-2 and AP2XII-1 act as negative regulators, suppressing merozoite-primed pre-sexual commitment during asexual development. Depletion of AP2XI-2 in type II Pru strain induces merogony and production of mature merozoites in an alkaline medium but not in a neutral medium. In contrast, AP2XII-1-depleted Pru strain undergoes several rounds of merogony and produces merozoites in a neutral medium, with more pronounced effects observed under alkaline conditions. Additionally, we identified two additional AP2XI-2-interacting proteins involved in repressing merozoite programming. These findings underscore the intricate regulation of pre-sexual commitment by a network of factors and suggest that AP2XI-2 or AP2XII-1-depleted Pru parasites can serve as a model for studying merogony in vitro. Wang et al. discovered that AP2XI-2 and AP2XII-1 negatively regulate merozoite-primed pre-sexual commitment in Toxoplasma gondii, and parasites depleted of either AP2XI-2 or AP2XII-1 can serve as a valuable in vitro model for studying merogony. [ABSTRACT FROM AUTHOR]

Toxoplasma gondii causes one of the most common protozoal diseases of humans and animals worldwide. With the aim of designing an effective vaccine against T. gondii infection, we examined the immunogenicity of a DNA vaccine expressing heat shock protein 40 (HSP40) against challenge with T. gondii (type I RH and type II Pru) strains in Kunming mice. The plasmid pVAX1-HSP40 was constructed and used to immunize mice by intramuscular injection for three sequential immunizations with two-week intervals. This immunization regimen significantly reduced parasite cyst burden in pVAX1-HSP40-immunized mice (1871.9 ± 142.3) compared with control mouse groups immunized with pVAX1 (3479.2 ± 204.4), phosphate buffered saline (3024.4 ± 212.8), or left untreated (3275.0 ± 179.8) as healthy controls (p

Sheep are highly susceptible to infections with Toxoplasma gondii and play a major role in the transmission of toxoplasmosis to humans. In the present study, 779 serum samples from sheep were collected from Henan province, central China from March 2015 to May 2016, and antibodies to T. gondii were detected by modified agglutination test (MAT). The overall seroprevalence of T. gondii in sheep was 12.71% (99/779). The risk factors significantly associated with T. gondii seroprevalence were the geographical origin, age, presence of cats, and the rearing system. This is the first report of T. gondii infection in sheep in Henan province, central China, and of an association of seropositivity to T. gondii with risk factors.

Toxoplasmosis, caused by Toxoplasma gondii , is a common disease worldwide and could be severe and even fatal in immunocompromised individuals and fetuses. Limitation in current available treatment options drives the need to develop novel therapeutics. This study assessed the anti- T. gondii potential of 103 marine natural products. A luminescence-based β-galactosidase activity assay was used to screen the marine natural products library. Afterward, those compounds that displayed over 70% parasite inhibition ratio were further chosen to assess their cytotoxicity. Compounds exhibiting low cytotoxicity (≥80% cell viability) were applied to evaluate the inhibition efficacy on discrete steps of the T. gondii lytic cycle, including invasion, intracellular growth, and egress abilities as well as the cell cycle. We found that both estradiol benzoate and octyl gallate caused >70% inhibition of tachyzoite growth with IC50 values of 4.41 ± 0.94 and 5.66 ± 0.35 μM, respectively, and displayed low cytotoxicity with TD50 values of 34.11 ± 2.86 and 26.4 ± 0.98 μM, respectively. Despite their defects in inhibition of invasion and egress of tachyzoite, the two compounds markedly inhibited the tachyzoite intracellular replication. Flow cytometric analyses further suggested that the anti- T. gondii activity of estradiol benzoate, rather than octyl gallate, may be linked to halting cell cycle progression of tachyzoite from G1 to S phase. Taken together, these findings suggest that both estradiol benzoate and octyl gallate are potential inhibitors for anti- T. gondii infection and support the further exploration of marine natural products as a thinkable source of alternative and active agents against T. gondii. [ABSTRACT FROM AUTHOR]

Important progress has been made in understanding how immunity is elicited against Toxoplasma gondii – a complex pathogen with multiple mechanisms of immune evasion. Many vaccine candidates have been tested using various strategies in animal models. However, none of these strategies has delivered as yet, and important challenges remain in the development of vaccines that can eliminate the tissue cysts and/or fully block vertical transmission. In this review, we provide an overview of the current understanding of the host immune response to T. gondii infection and summarize the key limitations for the development of an effective, safe, and durable toxoplasmosis vaccine. We also discuss how the successes and failures in developing and testing vaccine candidates have provided a roadmap for future vaccine development. Highlights There is a compelling need to develop a safe and effective toxoplasmosis vaccine. Successful vaccination of domestic cats is the key step in reducing T. gondii transmission to humans and food-producing animals. An effective toxoplasmosis vaccine must be able to induce both humoral and cellular immune responses, directed against multiple different proteins, at different stages of the parasite life cycle. Live attenuated T. gondii strains offer good protection against toxoplasmosis, but the possibility of reversion to the virulent type remains possible. There is a need to identify more immunogenic antigens, adjuvants, and antigen-delivery systems together with defining robust immunocorrelates of protection. Having a standardized protocol for assessment of vaccine efficacy can facilitate the synergy between the results obtained by various research groups. 'Omics' technologies have revolutionized our understanding of the pathophysiology of toxoplasmosis, paving the way for development of a safe and effective vaccine. [ABSTRACT FROM AUTHOR]

Background: Toxoplasmosis is a worldwide zoonosis caused by the intracellular parasite Toxoplasma gondii. However, no effective vaccine is yet available. Poly(lactide-co-glycolide) polymers can reduce protein degradation and sustain the release of antigens over a long period, which could generate a long-lasting immune response in vivo. Using a mouse model of toxoplasmosis, we evaluated the protective efficacy of vaccination with two recombinant proteins, which are formulated in biodegradable polymers.Methods: Two recombinant proteins, rCDPK6 and rROP18, were encapsulated in poly(D,L-lactide-co-glycolide) (PLG), and then injected subcutaneously into Kunming mice. The mice immune responses were evaluated in terms of lympho-proliferation, cytokine expression, and antibodies. The survival of infected mice and brain cyst formation were also evaluated at 6 weeks after challenge with T. gondii RH strain (genotype I) or PRU strain (genotype II).Results: Both protein vaccines induced Th1-biased immune responses, with increased specific antibodies and T cells, high levels of interferon-γ and interleukin 2, and strong lymphocyte proliferative responses. The mice immunized with the various protein vaccines survived slightly longer time than the control groups (P > 0.05) after injection with T. gondii RH strain. There were fewer brain cysts in the mice in all the immunized groups than that in the control groups, and the brain cysts were significantly reduced in mice immunized with proteins + 206, rCDPK6 + PLG and rCDPK6 + rROP18 + PLG (P < 0.05) compared controls. Further comparison of the immune responses to the proteins adjuvanted with PLG or Montanide™ ISA 206 VG 6 weeks after the last immunization revealed that antigens encapsulated in PLG conferred greater protective immunity against challenge.Conclusions: These findings suggest that the two recombinant T. gondii proteins encapsulated in PLG conferred immunity to T. gondii for an extended period, providing the foundation for the further development of a commercial vaccine against toxoplasmosis. [ABSTRACT FROM AUTHOR]

Toxoplasma gondii, a significant public health risk, is able to infect almost all warm-blooded animals including humans, and it results in economic losses in production animals. In the last three years, a large number of vaccination experiments have been performed to controlT. gondiiinfection, with the target of limiting the acute infection and reducing or eliminating tissue cysts in the intermediate hosts. In this paper, we summarize the latest results of the veterinary vaccines againstT. gondiiinfection since 2013. Immunization with live-attenuated whole organisms of non-reverting mutants has been shown to induce remarkably potent immune responses associated with control of acute and chronic toxoplasmosis. The non-cyst-forming mutants are promising new tools for the development of veterinary vaccines againstT. gondiiinfection. [ABSTRACT FROM PUBLISHER]

Objectives: To evaluate the protective efficacy of two novel DNA vaccines expressingToxoplasma gondiirhomboid 4 (ROM4) and rhomboid 5 (ROM5) proteins against acute and chronic toxoplasmosis. Methods: DNA vaccines (pVAX-TgROM5 and pVAX-TgROM4) were constructed and their immunogenicity evaluated in Kunming mice. Results: Mice vaccinated with pVAX-TgROM5 or pVAX-TgROM4 elicited strong Th1-type humoral and cellular responses, with higher level of IgG antibody titers (the predominance of IgG2a production), and increased levels of CD4+and CD8+T cells and cytokines IFN-γ, IL-2, IL-12 (p70) and IL-23. Mice vaccinated with pVAX-TgROM5 (11 days) showed a significantly longer survival time compared with controls (8 days) (p < 0.05) after lethal challenge. Brain cyst numbers of mice vaccinated with pVAX-TgROM5 and pVAX-TgROM4 reduced significantly (p < 0.05) (72.04 and 44.08%, respectively) compared with control groups after chronic challenge.Conclusion: The pVAX-TgROM5 showed a better protective efficacy against acute and chronic toxoplasmosis compared to pVAX-TgROM4. [ABSTRACT FROM PUBLISHER]

Toxoplasmosis, caused by the obligate intracellular protozoan parasite Toxoplasma gondii, has become a serious public health problem worldwide. T. gondii can infect almost all warm-blooded animals, including parrots. However, little is known of T. gondii infection in parrots in China. Antibodies against T. gondii in 311 parrots including 202 Budgerigars ( Melopsittacus undulatus), 26 Lovebirds ( Agapornis sp.), 22 Cockatiels ( Nymphicus hollandicus), and 61 Alexandrine Parakeets ( Psittacula eupatria) in the cities of Beijing and Weifang in north China were tested using the modified agglutination test (MAT). Twenty-six (8.36%) out of 311 serum samples were positive for T. gondii at the cutoff of 1:5. Among the four species, a higher seroprevalence of T. gondii was found in Cockatiels (13.64%, 95% confidence interval [CI] 0.00-27.98), although the difference was not statistically significant ( p=0.61). Seropositivity rates against T. gondii in male parrots (10.43%, 95% CI 5.74-15.12) were not statistically different from that in female parrots (6.08%, 95% CI 2.23-9.93, p=0.17). The seropositivity of T. gondii in parrots from Weifang and Beijing was 11.11% (95% CI 6.13-16.09) and 5.70% (95% CI 2.08-9.31), respectively. The seroprevalence varied in parrots of different age groups, ranging from 5.71% (95% CI 1.27-10.15) to 13.00% (95% CI 6.41-19.69), however, the difference among age groups was not statistically significant ( p=0.12). The seroprevalence of T. gondii infection in parrots in summer (11.63%, 95% CI 6.84-16.42) was significantly higher than in spring (4.32%, 95% CI 0.94-7.70, p=0.02). The results of the present survey indicated that parrots in China are exposed to T. gondii. To our knowledge, this is the first report of T. gondii seroprevalence in parrots in China. [ABSTRACT FROM AUTHOR]

Toxoplasmosis caused by the protozoan Toxoplasma gondii is a major public health problem, infecting one-third of the world human beings, and leads to abortion in domestic animals. A vaccine strategy would be an ideal tool for improving disease control. Many efforts have been made to develop vaccines against T. gondii to reduce oocyst shedding in cats and tissue cyst formation in mammals over the last 20 years, but only a live-attenuated vaccine based on the S48 strain has been licensed for veterinary use. Here, the authors review the recent development of T. gondii vaccines in cats, food-producing animals and mice, and present its future perspectives. However, a single or only a few antigen candidates revealed by various experimental studies are limited by only eliciting partial protective immunity against T. gondii. Future studies of T. gondii vaccines should include as many CTL epitopes as the live attenuated vaccines. [ABSTRACT FROM AUTHOR]

In the present study, we performed a cross-sectional survey to determine the occurrence and genotype distribution of T. gondii DNA in soil samples collected from different sources from six geographic regions in China. Between March 2015 and June 2017, 2100 soil samples were collected from schools, parks, farms and coastal beaches, and examined for T. gondii DNA using three PCR assays targeting 529-bp repeat element (RE) sequence, B1 gene and ITS-1 gene sequences. Also, we investigated whether geographic region, soil source and type, and sampling season can influence the prevalence of T. gondii DNA in the soil. Soil samples collected from farms and parks had the highest prevalence, whereas samples collected from school playgrounds and coastal beaches had the lowest prevalence. PCR assays targeting 529-bp RE and ITS-1 gene sequences were more sensitive than the B1 gene-based assay. Positive PCR products were genotyped using multi-locus PCR-RFLP, and ToxoDB #9 was the predominant genotype found in the contaminated soil samples. Multiple logistic regression identified factors correlated significantly with the presence of T. gondii DNA in the soil to be the source of the soil, including farms (odds ratio 3.10; 95% confidence interval [CI], 1.52 to 6.29; p = 0.002) and parks (2.59; 95% CI 1.28 to 5.27; p = 0.009). These results show that Chinese soil hosts T. gondii of the most prevalent genotype in China (ToxoDB#9) and that the soil type influences infection patterns. • The largest study to determine the prevalence and genotype of T. gondii DNA in soil samples from China. • We provide the first joint use of three PCR assays to detect T. gondii DNA in soil samples. • Soil source is were key risk factor associated with soil contamination with T. gondii DNA. • The first report of ToxoDB#9 genotype from soil samples in China. [ABSTRACT FROM AUTHOR]

Mussels, randomly collected from fish markets in China, were analyzed by a semi-nested PCR to detect B1 gene of Toxoplasma gondii. Out of the 2215 samples, fifty-five (2.48%) were detected T. gondii -positive. The prevalence in Shandong province, Liaoning province and Zhejiang province were 2.51%, 2.26% and 2.69%, respectively. T. gondii oocysts were more frequently detected in digestive glands (1.04%) and haemolymph (1.49%) when compared with gills (0.23%). Of the 55 positive DNA, only two samples showed complete genotype at 11 locus and were authenticated as ToxoDB Genotype #9. To our knowledge, the present study is the first to confirm the presence of T. gondii in market-sold mussels in China. The findings point to the risk of humans acquiring T. gondii infection by consuming mussels bought in the aquatic product market. • This is the first report of Toxoplasma gondii in mussels in China. • Fifty-five (2.48%) out of 2215 mussels were tested T. gondii -positive by a semi-nested PCR targeting the B1 gene. • Haemolymph and digestive glands are the most common organs that T. gondii oocysts settled in. • ToxoDB Genotype #9 was found in the examined mussels. [ABSTRACT FROM AUTHOR]

Toxoplasma gondii can infect nearly all warm-blooded animals including birds. However, limited information on the molecular epidemiology and genotypes of T. gondii infecting poultry is available in China. Therefore, the present study characterized T. gondii genotypes in poultry meat in eastern China. During August 2015 and September 2016, muscle tissue samples collecting from 414 poultries (257 chickens, 115 ducks and 42 geese) in Shandong provinces were used to detect the T. gondii B1 gene by a semi-nested PCR, and the positive samples were genotyped at 10 nuclear loci (i.e., SAG1, alternative SAG2, 5′- and 3′-SAG2, SAG3, L358, BTUB, c22-8, GRA6, c29-2, PK1) and an apicoplast locus Apico by multi-locus PCR-RFLP technology. Thirty-two (7.37%) samples from 414 poultry meat were T. gondii B1 gene positive. Chicken had the highest T. gondii prevalence (8.17%), followed by ducks (7.83%) and geese (4.76%). Furthermore, only one genotype (ToxoDB#9) was identified. This is the first genetic characterization of T. gondii isolates from poultry meat in Shandong province, eastern China and also the first report of genotype ToxoDB#9 was found in poultry in China, which provide basic data for the surveillance and control of T. gondii infection in poultry, other animals and humans. [ABSTRACT FROM AUTHOR]

Pig is the well-known intermediate host of T. gondii , a ubiquitous and obligate intracellular zoonotic pathogen. However, information about prevalence and genotypes of T. gondii infection in free-ranging pigs is scarce. Therefore a total of 186 hilar lymph nodes specimens were collected from free-ranging pigs from rural regions from Jilin (n = 119) and Liaoning (n = 67) provinces, northeastern China, and were investigated from T. gondii infection by semi-nested PCR of the B1 gene. Positive testing samples were genotyped by using polymerase chain reaction followed by restriction-fragment length polymorphism technology (PCR-RFLP) applied to 11 loci. The overall prevalence of T. gondii in investigated free-ranging pigs was 18.3% (34/186), with 16.4% (11/67) in Liaoning Province and 19.3% (23/119) in Jilin Province. Moreover, two genotypes, namely ToxoDB #9 and ToxoDB #10, were detected in investigated pigs. The present study showed a high T. gondii prevalence in free-ranging compared to farmed pigs as reported in previous studies by others, raising a major public health concern. It is essential to establish efficient strategies to prevent and control T. gondii infection in free-ranging pigs, other animals and humans in investigated regions. [ABSTRACT FROM AUTHOR]

Toxoplasma gondii oocysts in the water might be filtered through the gills of shellfish in the process of feeding, and can be concentrated in the digestive glands. Consumers might become infected through ingestion of the shellfish unless they are discharged or inactivated by the shellfish. Thus, the purpose of this study was to evaluate the presence of T. gondii in market-sold oysters in China under natural conditions using a molecular approach. A total of 998 oysters were collected from markets in four cities (Weihai, Qingdao, Yantai and Rizhao) of Shandong province, eastern China. Of these, 26 samples (2.61%) were tested positive by nested PCR amplification of T. gondii B1 gene. Only one of the 26 positive samples was typed completely, and was identified as ToxoDB Genotype #9. This is first report of T. gondii in market-sold oysters in China, suggesting that oysters have the ability to filter and retain T. gondii oocysts in their tissues, which represents a risk to public health because oysters are frequently ingested in nature. [ABSTRACT FROM AUTHOR]

Toxolasma gondii is one of the most important obligate intracellular protozoan parasites. Recently, toxoplasmosis is of increasing concerns because T. gondii not only has a worldwide distribution but also can infect virtually all warm-blooded hosts including donkeys. However, limited information is available concerning the genetic characterization of T. gondii in donkeys in northeastern China. In this study, a total of 302 brain tissue samples collected from donkeys from Jilin ( n = 108) and Liaoning ( n = 194) provinces, northeastern China, were examined for T. gondii infection by semi-nested PCR of B1 gene. The positive samples were genotyped at 11 loci (i.e., SAG1, alternative SAG2, 5′-and 3′-SAG2, SAG3, L358, BTUB, c22-8, GRA6, c29-2, PK1 and Apico) using polymerase chain reaction-restriction fragment length polymorphism technology. Of 302 brain tissue samples, 19 (6.29%) were PCR-positive for T. gondii . The prevalence rates of T. gondii were 6.48% (7/108) and 6.19% (12/194) in Jilin Province and Liaoning Province, respectively. The prevalence of T. gondii in different season groups varied from 5.56% to 7.41%. The prevalence of T. gondii in “Cage-free” donkeys was higher than that in “Captive” donkeys. Of the 19 positive samples, only two isolates were successfully genotyped at all loci, three were genotyped at 9 loci. In total, four samples belong to ToxoDB genotype #9, one belong to ToxoDB genotype #10. This is firstly characterized the T. gondii isolates from donkeys in northeastern China. The results of the present study will improve the information of the distribution of T. gondii genotypes in China. [ABSTRACT FROM AUTHOR]

Abstract: Toxoplasma gondii is an obligate intracellular protozoan parasite infecting humans, mammals and birds. Eukaryotic translation initiation factor (eIF4A) is a newly identified protein associated with tachyzoite virulence. To evaluate the protective efficacy of T. gondii eIF4A, a DNA vaccine (pVAX-eIF4A) encoding T. gondii eIF4A (Tg-eIF4A) gene was constructed. The expression ability of this recombinant DNA plasmid was examined in Marc145 cells by IFA. Then, Kunming mice were intramuscularly immunized with pVAX-eIF4A and followed by challenge infection with the highly virulent T. gondii RH strain. The results showed that vaccination with pVAX-eIF4A elicited specific humoral responses, with high IgG antibody titers and specific lymphocyte proliferative responses. The cellular immune response was associated with significant production of IFN-γ, IL-2 in Kunming mice, and a mixed IgG1/IgG2a response with predominance of IgG2a production, indicating that a Th1 type response was elicited after immunization with pVAX-eIF4A. In addition, the increase of the percentage of CD8+ T cells in lymphoid in mice suggested the activation of MHC class I restricted antigen presentation pathways. After lethal challenge, the mice vaccinated with the pVAX-eIF4A showed a significantly prolonged survival time (23.0±5.5 days) compared with control mice which died within 7 days of challenge (P <0.05). These results demonstrate that pVAX-eIF4A could elicit strong humoral, Th1-type cellular immune responses and increase survival time of immunized mice, suggesting that eIF4A is a promising vaccine candidate against acute T. gondii infection in mice. [Copyright &y& Elsevier]

• Toxoplasma gondii (T. gondii) is prevalent and unevenly distributed in Chinese cattle farms. • The warm and wet environment may be one of the reasons for the difference in T. gondii seroprevalence of cattle in China. • The use of ELISA may help relevant personnel to obtain more accurate test data. Toxoplasma gondii can infect almost all warm-blooded animals, including cattle, causing serious disease to animals and humans. Because cattle provide milk and meat for humans, an increasing number of people are raising cattle as a source of income. However, T. gondii may be transmitted to humans through the meat and milk of cattle. Although substantial relevant studies have been performed, overall data on the seroprevalence of T. gondii in cattle is still lacking. In this meta-analysis, 71 relevant studies were included from five databases that investigated the seroprevalence of T. gondii in cattle in China from 2010 to 2019. The overall pooled T. gondii seroprevalence in cattle was 10.1% (4217/39,274) in China. The seroprevalence of T. gondii was highest in southwestern China (21.6%, 727/3117) and lowest in northern China (4.5%, 185/1966). Due to the implementation of disease control measures during 2012 to 2020, the lowest positive rate was seen in the post-2017 subgroup of sampling years (5.8%, 170/3022). In the cattle breeds subgroups, the seroprevalence was highest in yaks (14.3%, 1695/10,777). Cattle aged ≥12 months (9.6%, 1248/12,438) had a higher seroprevalence than those <12 months (6.7%, 226/3132). Female cattle had a slightly higher seroprevalence (12.5%, 793/6670) than male cattle (11.7%, 418/3856). The seroprevalence in summer (11.8%, 517/4744) was the highest of all seasons. The present study shows that T. gondii is common in cattle in China. Therefore, monitoring measures and further research are needed to control T. gondii and improve public health. [ABSTRACT FROM AUTHOR]