Toxoplasma gondii is a single-celled parasite that infects nearly all warm-blooded animals, including humans (Montoya and Liesenfeld, 2004). It occurs worldwide and can persist for a lifetime in mammals. Humans get infected by eating undercooked meat of animals containing the tissue cysts of this parasite. In immune-competent individuals, T. gondii infection usually does not cause significant clinical symptoms, whereas in pregnant or immunocompromised individuals, T. gondii infection (toxoplasmosis) can cause more serious problems like abortion and even death (Dunn et al., 1999; Wang et al., 2017). A combination of pyrimethamine and sulfadiazine is usually used to treat toxoplasmosis, although it is generally inefficient and causes side effects (Alday and Doggett, 2017). Worse still, there is a lack of vaccines to prevent T. gondii infection in humans or animals.
Toxoplasma/enzymology* ; Animals ; Humans ; Toxoplasmosis ; Mitochondria/enzymology* ; Protozoan Proteins/metabolism*

The most common medications for the treatment of zoonotic toxoplasmosis are pyrimethamine and sulfadiazine, which may cause serious undesirable side effects. Thus, there is an urgent need to develop novel therapeutics. Baicalein (BAI, C₁₅H₁₀O₅) has been shown to perform well against protozoan parasites including Leishmania and Cryptosporidium. In this study, the inhibition efficacy of BAI on Toxoplasma gondii was evaluated using plaque, invasion, and intracellular proliferation assays. BAI effectively inhibited T. gondii (half-maximum inhibitory concentration (IC₅₀)=6.457×10^-5 mol/L), with a reduced invasion rate (33.56%) and intracellular proliferation, and exhibited low cytotoxicity (half-maximum toxicity concentration (TC₅₀)=5.929×10^-4 mol/L). Further investigation using a mouse model shed light on the inhibitory efficacy of BAI against T. gondii, as well as the potential mechanisms underlying its anti-parasitic effects. The survival time of T. gondii-infected ICR mice treated with BAI was remarkably extended, and their parasite burdens in the liver and spleen were greatly reduced compared with those of the negative control group. Histopathological examination of live sections revealed effective therapeutic outcomes in the treatment groups, with no notable pathological alterations observed. Furthermore, alterations in cytokine levels indicated that BAI not only effectively suppressed the growth of T. gondii but also prevented excessive inflammation in mice. Collectively, these findings underscore the significant inhibitory efficacy of BAI against T. gondii, positioning it as a promising alternative therapeutic agent for toxoplasmosis.
Animals ; Toxoplasma/drug effects* ; Flavanones/therapeutic use* ; Mice ; Antiparasitic Agents/therapeutic use* ; Mice, Inbred ICR ; Toxoplasmosis/drug therapy* ; Female

OBJECTIVE: To analyze the RNA binding protein of Toxoplasma gondii (TgDDX39) using bioinformatics technology, and to evaluate the immunogenicity of TgDDX39, so as to provide insights into development of toxoplasmosis vaccines. METHODS: The amino acid sequences of TgDDX39 were retrieved from the ToxoDB database, and the physicochemical properties, transmembrane structure domain, signal peptide sites, post-translational modification sites, coils, secondary and tertiary structures, hydrophobicity, and antigenic epitopes of the TgDDX39 protein were predicted using online bioinformatics tools, incluiding ProtParam, TMHMM 2.0, SignalP 5.0, NetPhos 3.1, COILS, SOPMA, Phyre2, ProtScale, ABCpred, SYFPEITHI and DNA-STAR. RESULTS: TgDDX39 protein was predicted to be an unstable hydrophilic protein with the molecular formula of C₂₁₇₃H₃₄₅₈N₅₉₈O₆₆₁S₁₈, which contained 434 amino acids and had an estimated molecular weight of 49.1 kDa and a theoretical isoelectric point of 5.55. The protein was predicted to have an extremely low possibility of signal peptides, without transmembrane regions, and contain 27 phosphorylation sites. The β turn and random coils accounted for 39.63% of the secondary structure of the TgDDX39 protein, and a coiled helix tended to produce in one site. In addition, the TgDDX39 protein contained multiple B and T cell antigenic epitopes. CONCLUSIONS Bioinformatics analyses predict that TgDDX39 protein has high immunogenicity and contains multiple antigenic epitopes. TgDDX39 protein is a potential candidate antigen for vaccine development.
Humans ; Toxoplasma/metabolism* ; Toxoplasmosis/prevention & control* ; Vaccines ; Epitopes, T-Lymphocyte ; Computational Biology ; Protozoan Proteins/chemistry*

Toxoplasma gondii is a worldwide parasite that can infect almost all kinds of mammals and cause fatal toxoplasmosis in immunocompromised patients. Apoptosis is one of the principal strategies of host cells to clear pathogens and maintain organismal homeostasis, but the mechanism of cell apoptosis induced by T. gondii remains obscure. To explore the apoptosis influenced by T. gondii, Vero cells infected or uninfected with the parasite were subjected to apoptosis detection and subsequent dual RNA sequencing (RNA-seq). Using high-throughput Illumina sequencing and bioinformatics analysis, we found that pro-apoptosis genes such as DNA damage-inducible transcript 3 (DDIT3), growth arrest and DNA damage-inducible α (GADD45A), caspase-3 (CASP3), and high-temperature requirement protease A2 (HtrA2) were upregulated, and anti-apoptosis genes such as poly(adenosine diphosphate (ADP)-ribose) polymerase family member 3 (PARP3), B-cell lymphoma 2 (Bcl-2), and baculoviral inhibitor of apoptosis protein (IAP) repeat containing 5 (BIRC5) were downregulated. Besides, tumor necrosis factor (TNF) receptor-associated factor 1 (TRAF1), TRAF2, TNF receptor superfamily member 10b (TNFRSF10b), disabled homolog 2 (DAB2)‍-interacting protein (DAB2IP), and inositol 1,4,5-trisphosphate receptor type 3 (ITPR3) were enriched in the upstream of TNF, TNF-related apoptosis-inducing ligand (TRAIL), and endoplasmic reticulum (ER) stress pathways, and TRAIL-receptor 2 (TRAIL-R2) was regarded as an important membrane receptor influenced by T. gondii that had not been previously considered. In conclusion, the T. gondii RH strain could promote and mediate apoptosis through multiple pathways mentioned above in Vero cells. Our findings improve the understanding of the T. gondii infection process through providing new insights into the related cellular apoptosis mechanisms.
Animals ; Apoptosis ; Chlorocebus aethiops ; Gene Expression Profiling ; Humans ; Mammals/genetics* ; Toxoplasma/genetics* ; Toxoplasmosis/pathology* ; Vero Cells ; ras GTPase-Activating Proteins/genetics*

For improving epitope immunogenicity and achieving the co-immunization, late protein 1 (L1) of HPV type 16 (HPV16L1) was selected as the vector to carry the dominant epitope of Toxoplasma gondii because of the shared common population between Toxoplasma gondii and human papillomavirus (HPV). RSepitope-HPV16L1 (RSepitope fused at the "N-terminus" of HPV16L1) and HPV16L1-RSepitope (RSepitope fused at the "C-terminus" of HPV16L1) chimeras were constructed. After transfection of COS-7 cells with the recombinants, Western blot, RT-PCR, and immunofluorescence experiments confirmed that RSepitope-HPV16L1 could successfully express the corresponding mRNA and protein of RSepitope and HPV16L1, but the HPV16L1-RSepitope construct could not. A "prime-boost" immunization program was applied in mice to further evaluate the immune response elicited by the constructs, and the RSepitope-HPV16L1 immunization group produced the most significantly increased humoral and cellular immune responses (the highest RSepitope-specific IgG antibody level and the highest IFN-γ production, respectively), in which both elevated Th1 and Th2 immune responses were obtained. Moreover, the advantage of HPV16L1 as an epitope carrier was remarkable for RSepitope-HPV16L1, which induced a more prominent immunological response than RSepitope alone (without fusion with HPV16L1). Our research indicated that the N-terminus of HPV16L1 could be a better insertion site for enhancing target epitope immunogenicity, and our study offers a design for epitope vaccine of reasonable combination.
Animals ; Antibody Formation ; Epitopes ; Immunization ; Mice ; Mice, Inbred BALB C ; Toxoplasma ; Vaccination ; Vaccines, DNA

OBJECTIVE: To investigate the changes in the exosomes secreted by mouse dendritic cell line DC2.4 after infection with and to analyze the possible regulatory mechanisms underlying such changes. METHODS: The exosomes were extracted by ultracentrifugation from DC2.4 cells at 28 h after infection with . The morphology of the exosomes was examined with transmission electron microscopy, and the exosome size and density were determined using a nanoparticle tracker. High-throughput sequencing was carried out to identify the differentially expressed small RNAs in the exosomes derived from the infected cells. RESULTS: infection resulted in a significantly increased density of exosomes secreted by DC2.4 cells. Small RNA sequencing revealed that infection caused an increase in the number of miRNAs and piRNAs in the exosomes. The significantly up-regulated piRNAs after the infection included piR-mmu-159, piR-mmu-1526, piR-mmu-9082, piR-mmu-17405, and piR-mmu-25576. CONCLUSIONS infection causes accumulation and enrichment of exosomes secreted by DC2.4 cells with increased miRNAs and piRNAs in the exosomes.
Animals ; Cell Line ; Dendritic Cells ; Exosomes ; Mice ; MicroRNAs ; RNA, Small Interfering ; Toxoplasma

Toxoplasmosis is a cosmopolitan zoonotic infection, caused by a unicellular protozoan parasite known as Toxoplasma gondii that belongs to the phylum Apicomplexa. It is estimated that over one-third of the world's population has been exposed and are latently infected with the parasite. In humans, toxoplasmosis is predominantly asymptomatic in immunocompetent persons, while among immunocompromised individuals may be cause severe and progressive complications with poor prognosis. Moreover, seronegative pregnant mothers are other risk groups for acquiring the infection. The life cycle of T. gondii is very complex, indicating the presence of a plurality of antigenic epitopes. Despite of great advances, recognize and construct novel vaccines for prevent and control of toxoplasmosis in both humans and animals is still remains a great challenge for researchers to select potential protein sequences as the ideal antigens. Notably, in several past years, constant efforts of researchers have made considerable advances to elucidate the different aspects of the cell and molecular biology of T. gondii mainly on microneme antigens, dense granule antigens, surface antigens, and rhoptry proteins (ROP). These attempts thereby provided great impetus to the present focus on vaccine development, according to the defined subcellular components of the parasite. Although, currently there is no commercial vaccine for use in humans. Among the main identified T. gondii antigens, ROPs appear as a putative vaccine candidate that are vital for invasion procedure as well as survival within host cells. Overall, it is estimated that they occupy about 1%–30% of the total parasite cell volume. In this review, we have summarized the recent progress of ROP-based vaccine development through various strategies from DNA vaccines, epitope or multi epitope-based vaccines, recombinant protein vaccines to vaccines based on live-attenuated vectors and prime-boost strategies in different mouse models.
Animals ; Antigens, Surface ; Apicomplexa ; Cell Size ; Epitopes ; Humans ; Immunization ; Life Cycle Stages ; Mice ; Molecular Biology ; Mothers ; Parasites ; Prognosis ; Toxoplasma* ; Toxoplasmosis ; Vaccines ; Vaccines, DNA ; Vaccines, Synthetic ; Zoonoses

The roles of mast cells in allergic diseases and helminth infections are well known. However, the roles of mast cells in T. gondii infection is poorly understood. This study was focused on the production of pro-inflammatory cytokines (TNF-α, IL-4), chemokines (CXCL8, MCP-1) and nitric oxide (NO) by mast cells in response to soluble lysate of T. gondii tachyzoites. Production of CXCL8 (IL-8), MCP-1, TNF-α and IL-4 were measured by RT-PCR and ELISA. Western blot were used for detection of CXCR-1 and CXCR2. Our results showed that T. gondii lysates triggered mast cells to release CXCL8, MCP-1, TNF-α, IL-4 and to produce NO. This suggests that mast cells play an important role in inflammatory responses to T. gondii.
Blotting, Western ; Chemokines ; Cytokines ; Enzyme-Linked Immunosorbent Assay ; Helminths ; Humans ; Interleukin-4 ; Mast Cells ; Nitric Oxide ; Toxoplasma

Both Plasmodium spp. and Toxoplasma gondii are important apicomplexan parasites, which infect humans worldwide. Genetic analyses have revealed that 33% of amino acid sequences of inner membrane complex from the malaria parasite Plasmodium berghei is similar to that of Toxoplasma gondii. Inner membrane complex is known to be involved in cell invasion and replication. In this study, we investigated the resistance against T. gondii (ME49) infection induced by previously infected P. berghei (ANKA) in mice. Levels of T. gondii-specific IgG, IgG1, IgG2a, and IgG2b antibody responses, CD4+ and CD8+ T cell populations were found higher in the mice infected with P. berghei (ANKA) and challenged with T. gondii (ME49) compared to that in control mice infected with T. gondii alone (ME49). P. berghei (ANKA) + T. gondii (ME49) group showed significantly reduced the number and size of T. gondii (ME49) cysts in the brains of mice, resulting in lower body weight loss compared to ME49 control group. These results indicate that previous exposure to P. berghei (ANKA) induce resistance to subsequent T. gondii (ME49) infection.
Amino Acid Sequence ; Animals ; Antibody Formation ; Body Weight ; Brain ; Humans ; Immunoglobulin G ; Malaria ; Membranes ; Mice ; Parasites ; Plasmodium berghei ; Plasmodium ; Toxoplasma ; Toxoplasmosis

Based on the reactive oxygen species (ROS) regulatory properties of diphenyleneiodonium (DPI), we investigated the effects of DPI on host-infected T. gondii proliferation and determined specific concentration that inhibit the intracellular parasite growth but without severe toxic effect on human retinal pigment epithelial (ARPE-19) cells. As a result, it is observed that host superoxide, mitochondria superoxide and H2O2 levels can be increased by DPI, significantly, followed by suppression of T. gondii infection and proliferation. The involvement of ROS in anti-parasitic effect of DPI was confirmed by finding that DPI effect on T. gondii can be reversed by ROS scavengers, N-acetyl-L-cysteine and ascorbic acid. These results suggest that, in ARPE-19 cell, DPI can enhance host ROS generation to prevent T. gondii growth. Our study showed DPI is capable of suppressing T. gondii growth in host cells while minimizing the un-favorite side-effect to host cell. These results imply that DPI as a promising candidate material for novel drug development that can ameliorate toxoplasmosis based on ROS regulation.
Acetylcysteine ; Ascorbic Acid ; Humans ; Mitochondria ; Parasites ; Reactive Oxygen Species ; Retinaldehyde ; Superoxides ; Toxoplasma ; Toxoplasmosis