Proteomic characterization of the pellicle of Toxoplasma gondii

Detection and identification of highly antigenic proteins from cytoskeleton of Toxoplasma gondii by immune-proteomics

Research on the immunogenic molecules of Toxoplasma is a key priority in the development of protective vaccines against the parasite. In the present study, we analyzed the profile of immunorecognized proteins from the Toxoplasma cytoskeleton using sera from patients with both acute and chronic toxoplasmosis. The immunorecognized spots were analyzed by mass spectrometry and characterized by bioinformatic methods, leading to the identification of a total of 313 proteins. Sixty-three antigenic proteins were recognized by IgM antibodies and 250 antigenic proteins were recognized by IgG antibodies. About 10 proteins specifically reported as cytoskeletal proteins were identified with the IgG antibodies while 9 cytoskeletal proteins were detected by IgM antibodies. Bioinformatic analyses of the identified antigenic proteins were performed to determine their immunogenic potential, including the number of epitopes recognized by B lymphocytes, cytotoxic T lymphocytes (CD8+), and helper T lymphocytes (CD4+) receptors. This analysis enabled the selection of highly immunogenic proteins, which could serve as potential candidates for the design of a future vaccine against toxoplasmosis. SIGNIFICANCE: The study of immunogenic molecules from Toxoplasma gondii is a key priority in the search for protective vaccines. Despite partial success in previous strategies, identifying immunogenic proteins from the T. gondii cytoskeleton using immune-proteomics and bioinformatic approaches is crucial for vaccine development. This study provides valuable data that could serve as the foundation for designing novel immunogenic and immunoprotective molecules against toxoplasmosis.

AP2XII-9 is essential for parasite growth and suppresses bradyzoite differentiation in Toxoplasma gondii

Cyst formation, resulting from the differentiation of rapidly replicating tachyzoites into slowly growing bradyzoites, is the primary cause of chronic toxoplasmosis. Although the mechanisms governing bradyzoite differentiation have been partially elucidated, they remain incompletely understood. In this study, we show that the transcription factor AP2XII-9 is localized in the nucleus and exhibits periodic expression during the tachyzoite stage, with peak expression observed during the synthesis and mitosis phases. Conditional knockdown of AP2XII-9 in both the type I RH strain and type II cyst-forming Pru strain revealed that AP2XII-9 plays a critical role in the lytic cycle by regulating the formation of the inner membrane complex, proper apicoplast inheritance, and normal cell division, underscoring its essential role in T. gondii growth. Furthermore, depletion of AP2XII-9 induced bradyzoite differentiation even in the absence of alkaline stress. Transcriptomic analysis revealed that the deletion of AP2XII-9 resulted in the downregulation of tachyzoite growth-related genes and upregulation of a series of bradyzoite-specific genes. Taken together, these findings indicate that AP2XII-9 is essential for maintaining the rapid and normal replication of tachyzoites while actively repressing bradyzoite differentiation, reflecting the complexity of the mechanisms underlying bradyzoite differentiation.

Immunogenicity and protective efficacy of recombinant chimeric antigens based on surface proteins of Toxoplasma gondii

Introduction

Toxoplasmosis is caused by the opportunistic, cosmopolitan protozoan Toxoplasma gondii is one of the most common parasitoses in the world. This parasite can pose a threat to people with immunodeficiency but also to the fetus, since the invasion can lead to miscarriages. Moreover, this parasite can contribute to economic losses in livestock farming. These problems lead to the implementation of new, safe solutions for the development of effective toxoplasmosis immunoprophylaxis.

Methods

In this work, newly produced recombinant trivalent chimeric proteins of T. gondii, based on SAG1-SAG2 recombinant chimeric antigen that differ in one terminal antigenic component, were tested in terms of their ability to induce an effective post-vaccination response. Antigens were tested in vitro to assess their ability to elicit APC cells response and further mice of the C3H/HeOuJ strain were immunized using those antigens, to evaluate their immunogenicity and immunoprotective effect in vivo. Two weeks after the last dose mice were either sacrificed to assess selected parameters of the immune response or infected with T. gondii DX strain to determine the degree of protection one month later.

Results

The results of serological tests revealed a high level of serum IgG antibodies specific for the native T. gondii TLA antigens. TLA-stimulated splenocytes produced cytokines that are important in inhibiting protozoal invasion. Additionally, CD3+ CD4+ and CD3+ CD8+ T cell subpopulations of splenocytes were analysed by flow cytometry. One month after experimental infection mice were sacrificed, and their brains were isolated to count T. gondii tissue cyst. Immunization of mice with recombinant trivalent chimeric proteins of T. gondii resulted in reduction of tissue cyst burden rates reaching even 74%.

Discussion

The obtained results demonstrate strong immunogenicity of the studied proteins and will allow to select candidates for further research aimed at increasing the immunoprotective properties of experimental vaccines against toxoplasmosis based on T. gondii chimeric antigens.

Animal venoms: a novel source of anti-Toxoplasma gondii drug candidates

Toxoplasma gondii (T. gondii) is a nucleated intracellular parasitic protozoan with a broad host selectivity. It causes toxoplasmosis in immunocompromised or immunodeficient patients. The currently available treatments for toxoplasmosis have significant side effects as well as certain limitations, and the development of vaccines remains to be explored. Animal venoms are considered to be an important source of novel antimicrobial agents. Some peptides from animal venoms have amphipathic alpha-helix structures. They inhibit the growth of pathogens by targeting membranes to produce lethal pores and cause membrane rupture. Venom molecules generally possess immunomodulatory properties and play key roles in the suppression of pathogenic organisms. Here, we summarized literatures of the last 15 years on the interaction of animal venom peptides with T. gondii and attempt to explore the mechanisms of their interaction with parasites that involve membrane and organelle damage, immune response regulation and ion homeostasis. Finally, we analyzed some limitations of venom peptides for drug therapy and some insights into their development in future studies. It is hoped that more research will be stimulated to turn attention to the medical value of animal venoms in toxoplasmosis.

Mining the Proteome of Toxoplasma Parasites Seeking Vaccine and Diagnostic Candidates

Simple Summary

The One Health concept to toxoplasmosis highlights that the health of humans is closely related to the health of animals and our common environment. Toxoplasmosis outcomes might be severe and fatal in patients with immunodeficiency, diabetes, and pregnant women and infants. Consequently, the development of effective vaccine and diagnostic strategies is urgent for the elimination of this disease. Proteomics analysis has allowed the identification of key proteins that can be utilized in the development of novel disease diagnostics and vaccines. This work presents relevant proteins found in the proteome of the life cycle-specific stages of Toxoplasma parasites. In fact, it brings together the main functionality key proteins from Toxoplasma parasites coming from proteomic approaches that are most likely to be useful in improving the disease management, and critically proposes innovative directions to finally develop promising vaccines and diagnostics tools.

Abstract

Toxoplasma gondii is a pathogenic protozoan parasite that infects the nucleated cells of warm-blooded hosts leading to an infectious zoonotic disease known as toxoplasmosis. The infection outcomes might be severe and fatal in patients with immunodeficiency, diabetes, and pregnant women and infants. The One Health approach to toxoplasmosis highlights that the health of humans is closely related to the health of animals and our common environment. The presence of drug resistance and side effects, the further improvement of sensitivity and specificity of serodiagnostic tools and the potentiality of vaccine candidates to induce the host immune response are considered as justifiable reasons for the identification of novel targets for the better management of toxoplasmosis. Thus, the identification of new critical proteins in the proteome of Toxoplasma parasites can also be helpful in designing and test more effective drugs, vaccines, and diagnostic tools. Accordingly, in this study we present important proteins found in the proteome of the life cycle-specific stages of Toxoplasma parasites that are potential diagnostic or vaccine candidates. The current study might help to understand the complexity of these parasites and provide a possible source of strategies and biomolecules that can be further evaluated in the pathobiology of Toxoplasma parasites and for diagnostics and vaccine trials against this disease.

Unraveling Toxoplasma gondii GT1 Strain Virulence and New Protein-Coding Genes with Proteogenomic Analyses

Toxoplasma gondii is one of the most widespread parasites of great relevance to planetary health. It infects approximately one-third of the world population. T. gondii establishes itself in warm-blooded animals and causes adverse health outcomes, particularly in immunocompromised patients. T. gondii is also widely used as a model organism to study other related apicomplexan parasites, which requires a deeper understanding of its molecular biology. Type I strains (GT1 and RH) of T. gondii are considered the most virulent forms. The whole-genome sequencing of T. gondii annotated 8460 predicted gene models in the parasite. To this end, the proteogenomics technology allows harnessing of mass spectrometry (MS)-derived proteomic data to unravel new protein-coding genes, not to mention validation and correction of the existing gene models. In this study using the proteogenomic approach, we report the identification of 31 novel protein-coding genes while reannotating 88 existing gene models. Notably, the genome annotations were corrected for genes, such as SAG5C, GRA6, ROP4, ROP5, and ROP26. The associated proteins are known to play important roles in host-parasite interactions, particularly in relation to parasite virulence, suppression of host immune response, and distinctively pertinent for the survival of the parasite inside the host system. These new findings offer new insights, informing planetary health broadly and the knowledge base on T. gondii virulence specifically. The proteogenomics approach also provides a concrete example to study related apicomplexan organisms of relevance to planetary health, and so as to develop new diagnostics and therapeutics against toxoplasmosis and related diseases.