bims-toxgon Biomed News
on Toxoplasma gondii metabolism
Issue of 2026–05–31
ten papers selected by
Lakesh Kumar, BITS Pilani
  1. Inhibitors of the FASII Metabolic Pathway in Toxoplasma gondii: Advances and Therapeutic Perspectives.
  2. Tunnelling Nanotube Projections May Interfere with Toxoplasma gondii Interaction with Host Cells.
  3. Legacy 4(1H)-Quinolone Scaffolds Activity against Acute and Chronic Toxoplasma gondii Infection.
  4. Genetic analysis of pyrimidine biosynthetic enzymes in Plasmodium falciparum.
  5. Advances and Translational Challenges in Toxoplasma gondii Vaccine Development: From Antigen Discovery to mRNA and One Health Strategies.
  6. A dual-aptazyme system for genetic complementation reveals stage-specific roles for the Trypanosoma cruzi cytoskeleton-associated protein 5.5.
  7. Remodeling of tRNA modification in Trypanosoma cruzi life forms.
  8. Chemical biology tools for studying histone post-translational modifications.
  9. Biophysical and enzymatic comparison of Bacillus safensis and Bacillus subtilis malate dehydrogenase (MDH) enzymes.
  10. Transgenic selection and underlying mechanisms in apicomplexan parasites.
  1. Microorganisms. 2026 May 09. pii: 1072. [Epub ahead of print]14(5):
    Inhibitors of the FASII Metabolic Pathway in Toxoplasma gondii: Advances and Therapeutic Perspectives.
    Claudia Jessica Castillo-Villanueva, Jhony Anacleto-Santos, Teresa de Jesús López-Pérez, Brenda Casarrubias-Tabarez, Teresa I Fortoul, Marcela Rojas-Lemus, Nelly López-Valdez, Elisa Vega-Ávila, Fernando Calzada, Perla Yolanda López-Camacho, Norma Rivera-Fernández.
      Toxoplasma gondii is an obligate intracellular parasite of the phylum Apicomplexa and the causative agent of toxoplasmosis, a disease with a worldwide distribution that causes serious consequences in immunocompromised patients and during pregnancy. Current pharmacological treatments have significant limitations, including their toxicity, lack of efficacy against the chronic phase of the parasite, and low selectivity, highlighting the need to develop new therapeutic targets. One of the most promising targets is the fatty acid synthesis pathway II (FASII), a metabolic pathway located in the parasite's apicoplast and absent in mammalian hosts. This review synthesizes the available evidence on FASII pathway inhibitors described to date, as well as their potential impact on the viability and development of T. gondii. Overall, the reviewed studies support the FASII pathway as an attractive therapeutic target for the development of more selective and effective treatments against toxoplasmosis.
    Keywords:  FASII; Toxoplasma gondii; anti-Toxoplasma compounds; apicoplast; fatty acid metabolism; lipid inhibitors; lipidome
    DOI:  https://doi.org/10.3390/microorganisms14051072
  2. Microorganisms. 2026 Apr 26. pii: 971. [Epub ahead of print]14(5):
    Tunnelling Nanotube Projections May Interfere with Toxoplasma gondii Interaction with Host Cells.
    Everson Reili de Souza Teles, Wanderley de Souza.
      Toxoplasma gondii, the causative agent of toxoplasmosis, a disease widely distributed, is an intracellular parasite that invades host cells of different tissues using specialized endocytic activity. Recent studies suggest that tunneling nanotubes (TNTs), thin cell-surface projections, may participate in the parasite-host cell interaction. Here we report results that suggest the involvement of host-cell TNTs in the adhesion of T. gondii tachyzoites to epithelial LLC-MK2 cells. Microscopy analysis showed that incubating cells in a medium containing 0.45 M sucrose induces reversible assembly of TNTs without affecting cell viability. The presence of extended TNTs correlated with increased parasite adhesion and reduced parasite entry, thus suggesting a structural or signaling role in mediating adhesion. TNTs assembled following sucrose incubation contain both actin and tubulin components as determined by immunofluorescence microscopy. These results highlight a possible functional relevance of TNTs in T. gondii host cell interaction, especially in parasite adhesion, opening new perspectives for understanding T. gondii-host cell interaction.
    Keywords:  Toxoplasma gondii; electron microscopy; fluorescence microscopy; parasite-host cell adhesion and interaction; tunneling nanotubes
    DOI:  https://doi.org/10.3390/microorganisms14050971
  3. ACS Infect Dis. 2026 May 26.
    Legacy 4(1H)-Quinolone Scaffolds Activity against Acute and Chronic Toxoplasma gondii Infection.
    Melissa A Sleda, Khaly Diagne, Victoria Mills Clifton, Baihetiya Baierna, Roman Manetsch, Silvia N J Moreno.
      Toxoplasma gondii is a protozoan parasite capable of infecting most warm-blooded animals, including humans, and can cause severe disease in immunocompromised individuals and the developing fetus. Current treatments for toxoplasmosis are effective only against the acute stage of infection and have limited or no activity against the latent bradyzoite stage found within tissue cysts. The mitochondrion of T. gondii is a validated drug target, and the clinically used drug atovaquone acts by inhibiting the mitochondrial electron transport chain (ETC) at the coenzyme Q:cytochrome c oxidoreductase (bc1 complex). In this study, we evaluate two legacy 4(1H)-quinolones, ICI 56,780 and WR 243246, previously shown to inhibit the Plasmodium falciparum bc1 complex, for their efficacy against T. gondii. Both compounds inhibit tachyzoite growth with low-nanomolar EC50 values (0.34 nM for ICI 56,780 and 24 nM for WR 243246) and disrupt parasite mitochondrial function by blocking cytochrome c reduction and collapsing the mitochondrial membrane potential. Importantly, ICI 56,780 protects mice from lethal infection with type I RH tachyzoites. It also exhibits potent activity against chronic-stage parasites, reducing cyst size and bradyzoite viability in vitro and showing low-nanomolar EC50 values against in vivo-derived bradyzoites (EC50: 3.9 nM). In mice chronically infected with T. gondii, treatment with ICI 56,780 significantly decreases brain cyst burden. Although these 4(1H)-quinolones display some pharmacokinetic limitations, our findings highlight their potential as promising chemotypes active against both acute and chronic stages of T. gondii and provide a basis for future medicinal chemistry efforts to improve drug-like properties while preserving or enhancing antibradyzoite activity.
    Keywords:  Toxoplasma gondii; bradyzoites; chronic infection; electron transport chain; quinolones; tissue cysts
    DOI:  https://doi.org/10.1021/acsinfecdis.5c01074
  4. PLoS Pathog. 2026 May 27. 22(5): e1014269
    Genetic analysis of pyrimidine biosynthetic enzymes in Plasmodium falciparum.
    Krithika Rajaram, Montana L Sievert, Rubayet Elahi, James Blauwkamp, Lucas B Dillard, Sabrina Absalon, Sean T Prigge.
      The malaria parasite Plasmodium falciparum depends entirely on de novo pyrimidine synthesis, as it is unable to salvage these essential nucleotides. This reliance makes the pyrimidine biosynthesis pathway a compelling target for antimalarial drugs, with several inhibitors targeting its rate-limiting enzyme, dihydroorotate dehydrogenase (PfDHODH), already in clinical development. In this study, we investigated the roles of three other pathway enzymes aspartate transcarbamoylase (PfATC), carbamoyl phosphate synthetase II (PfCPSII), and dihydroorotase (PfDHO). PfATC features a unique N-terminal extension predicted to serve as an apicoplast trafficking peptide. However, using antibodies against the native protein and epitope-tagged versions, we found no evidence of apicoplast localization. Knockdown of PfATC expression proved lethal and could not be rescued by an apicoplast metabolic bypass. Complementation assays further revealed that truncation of the N-terminal domain impaired parasite growth, suggesting that this region is important for PfATC function or stability in vivo. PfCPSII, which harbors large Plasmodium-specific insertions between its catalytic domains, was likewise found to be essential for parasite proliferation. To assess the role of PfDHO, we engineered parasites to salvage uracil via heterologous expression of a yeast enzyme. Deletion of PfDHO in this parasite line resulted in uracil auxotrophy, confirming the enzyme's essential function in pyrimidine synthesis. Together, these findings reveal multiple vulnerable nodes within the pyrimidine biosynthesis pathway.
    DOI:  https://doi.org/10.1371/journal.ppat.1014269
  5. Vet Sci. 2026 Apr 30. pii: 437. [Epub ahead of print]13(5):
    Advances and Translational Challenges in Toxoplasma gondii Vaccine Development: From Antigen Discovery to mRNA and One Health Strategies.
    Abdul Qadeer, Mohamed Tharwat, Muhammad Zahoor Khan, Alexandra Juhasz, Fahad A Alshanbari.
      Toxoplasmosis, caused by the obligate intracellular parasite T. gondii, is one of the most prevalent parasitic infections worldwide, affecting approximately one-third of the global population. Despite decades of intensive research, no effective human vaccine exists. The only commercially available vaccine, Toxovax, is restricted to veterinary use in sheep and is unsuitable for human application due to safety concerns. Beyond summarizing the literature, this review offers a critical appraisal of why translation has stalled and where the field should focus next. Live-attenuated vaccines remain the most immunogenic in preclinical models but face significant translational barriers for human use. Key antigenic targets include surface antigens (SAG), dense granule antigens (GRA), rhoptry proteins (ROP), and microneme proteins (MIC). Protective immunity relies critically on Th1-type immune responses characterized by interferon-gamma production. Major obstacles include the parasite's complex life cycle, strain diversity, and difficulty achieving sterile immunity. Subunit and mRNA-based platforms offer more favorable safety profiles and established clinical precedents, representing the most viable pathway toward a human vaccine. Recent advances in CRISPR/Cas9 gene editing and emerging mRNA vaccine platforms offer promising new directions. This review advances the field in three ways. (i) It prioritizes mRNA and adjuvanted subunit formulations targeting multistage conserved antigens as the most realistic near-term human candidates. (ii) It identifies the limited targeting of bradyzoite-stage biology as a principal, under-addressed gap. (iii) It argues that future development must be differentiated into three complementary One Health goals-prevention of congenital disease in humans, reduction in tissue-cyst burden in livestock, and interruption of environmental transmission by vaccinating cats. In practice, a veterinary-first deployment strategy is the most immediate and impactful pathway to reducing the human and zoonotic burden of toxoplasmosis.
    Keywords:  CRISPR/Cas9; DNA vaccines; One Health; Toxoplasma gondii; bradyzoite antigens; immune response; live-attenuated vaccines; mRNA vaccines; translational barriers; vaccine development
    DOI:  https://doi.org/10.3390/vetsci13050437
  6. mSphere. 2026 May 29. e0009026
    A dual-aptazyme system for genetic complementation reveals stage-specific roles for the Trypanosoma cruzi cytoskeleton-associated protein 5.5.
    Justin Wiedeman, Ganesh Babu Malli Mohan, Gonzalo Seminario-Mondejar, Ronald Drew Etheridge.
      Parasitic trypanosomatids, such as Trypanosoma cruzi, Trypanosoma brucei, and Leishmania spp., cause devastating tropical diseases, with T. cruzi being increasingly recognized as a public health concern in the United States due to established sylvatic cycles and rising autochthonous transmission. Although T. brucei has long served as the model trypanosomatid due to the array of molecular tools available for its study, T. cruzi shares greater biological similarity with the majority of trypanosomatids regarding nutrient uptake, transmission strategy, and metabolism. Recent advancements in genetic tools have now enabled in-depth studies in T. cruzi previously restricted to T. brucei. Here, using the Small Hammerhead Aptazyme-Regulated Knockdown (SHARK) system, we report the characterization of cytoskeleton-associated protein 5.5 (CAP5.5) in T. cruzi. To validate this phenotype, we introduce a novel method for simultaneous knockdown and rescue of a target protein using two tetracycline-responsive aptazymes. Knockdown of CAP5.5 revealed stage-specific roles in the maintenance of cell shape, organelle segregation, and proliferation. To quantify these phenotypes, we leveraged open-source, state-of-the-art segmentation software to develop a semi-automated, high-throughput image analysis pipeline. Our data suggest a potential role for CAP5.5 in repairing motility-related damage to the microtubule cytoskeletal array. These findings demonstrate the emerging utility of T. cruzi as a robust model trypanosomatid.IMPORTANCETrypanosoma cruzi is the causative agent of Chagas disease, a neglected tropical disease that presents a growing public health concern. Historically, research into T. cruzi biology has been hindered by a scarcity of genetic tools, forcing scientists to rely on models from related but biologically distinct parasites. In this study, we utilize genetic tools (the SHARK conditional knockdown system) to characterize a cytoskeletal protein, CAP5.5, revealing that it is required for the parasite to maintain its shape and divide during its motile stage. We further demonstrate the use of a dual-control system that allows simultaneous gene knockdown and rescue, alongside a new high-throughput 3D imaging pipeline. This work establishes a rigorous technical framework that empowers the community to conduct in-depth investigations of essential T. cruzi genes directly, thus accelerating the discovery of potential therapeutic targets.
    Keywords:  CAP5.5; Chagas disease; Trypanosoma cruzi; cell morphogenesis; conditional knockdown; cytokinesis; cytoskeleton; fluorescent image analysis; shark
    DOI:  https://doi.org/10.1128/msphere.00090-26
  7. PLoS Pathog. 2026 May;22(5): e1014249
    Remodeling of tRNA modification in Trypanosoma cruzi life forms.
    Herbert Guimaraes de Sousa Silva, Janaina de Freitas Nascimento, Marilene Souza Braga, Ana Paula de Jesus Menezes, Ariel M Silber, Matthew K Waldor, Julia Pinheiro Chagas da Cunha, Satoshi Kimura.
      Trypanosoma cruzi, the etiological agent of Chagas disease, infects millions of people in the Americas. This parasite undergoes drastic changes in its morphology and metabolism between infective and noninfective forms through global remodeling of its proteome. Chemical modification of tRNA (tRNA modification) contributes to the control of protein expression by modulating the codon decoding process. However, knowledge of tRNA modification profiles, the enzymes that create modifications and their regulation in different cellular conditions is largely restricted to relatively few model organisms. Here, we profile tRNA modifications in both infective and noninfective forms of T. cruzi to probe their dynamic changes. Genome mining of tRNA modifying enzymes identified 65 putative tRNA-modifying enzymes in T. cruzi for 27 species of tRNA modifications, most of which were detected in T. cruzi tRNA by liquid chromatography mass spectrometry analyses. tRNA sequencing detected reverse transcription-derived signatures at 170 sites in T. cruzi tRNAs that are likely derived from 19 tRNA modifications. tRNA modifications and tRNA modification enzymes are differentially modulated across the life stages of T. cruzi. We found that hydroxywybutosine (OHyW) at position 37 on tRNAPhe(GAA) had a reduced level in the infective form (metacyclic trypomastigote) and the associated modification enzyme Tyw1a exhibited reduced expression in this stage. Knockout of Tyw1a increased the differentiation from epimastigote (noninfective form) to metacyclic trypomastigote, suggesting that changes in OHyW37 modification levels alter the rate of metacyclogenesis. Overall, our findings suggest that tRNA modification changes during the life stages of T. cruzi contribute to the differentiation of this parasite.
    DOI:  https://doi.org/10.1371/journal.ppat.1014249
  8. Cell Chem Biol. 2026 May 26. pii: S2451-9456(26)00150-9. [Epub ahead of print]
    Chemical biology tools for studying histone post-translational modifications.
    Cameron J Douglas, Ciaran P Seath.
      Post-translational modifications (PTMs) of histones are central regulators of chromatin organization and gene expression, providing a dynamic and reversible mechanism to encode cellular state. While advances in mass spectrometry have rapidly expanded the catalog of histone PTMs beyond classical acetylation and methylation, defining their functional roles remains a major challenge. A central bottleneck is linking specific PTMs to the enzymes that write and erase them, as well as the reader proteins that interpret them within native chromatin environments. The dysregulation of this regulatory machinery is increasingly implicated in cancer, neurodevelopmental disorders, and metabolic disease. Here, we argue that resolving PTM function requires integrating chemical precision with increasing biological complexity. We review chemical biology strategies for interrogating histone PTMs across this spectrum-from synthetic peptides to semisynthetic nucleosomes and intact chromatin-highlighting how each approach balances experimental control with physiological relevance and propose future directions for systematically mapping PTM-dependent interactions.
    Keywords:  acetylation; butyrylation; chemical biology; chromatin; histone; methylation; phosphorylation; post-translational modifications; ubiquitylation
    DOI:  https://doi.org/10.1016/j.chembiol.2026.04.015
  9. bioRxiv. 2026 May 14. pii: 2026.05.13.723581. [Epub ahead of print]
    Biophysical and enzymatic comparison of Bacillus safensis and Bacillus subtilis malate dehydrogenase (MDH) enzymes.
    Haley R Zafiropoulo, Juliette E Thomas, Nicholas R Cortez, Korina Apostol, Alice de Sá, Ryan Khosravi, Liam Moore, Christopher E Berndsen, Brianna Bibel.
      Species of Bacillus bacteria including Bacillus safensis and Bacillus subtilis are finding increasing uses in biotechnology and bioremediation, thanks in part to their metabolic robustness. Malate dehydrogenase (MDH) is at the heart of central metabolism and thus a better understanding of Bacillus MDH proteins could aid in the optimization of these applications. MDH of Bacillus spp. belong to the lactate dehydrogenase (LDH)-like class of MDH's, otherwise known as the MDH3 class. Despite wide prevalence in nature among prokaryotes and archaea, this typically homotetrameric class is understudied compared to the MDH1 and MDH2 classes found in eukaryotes. We therefore recombinantly expressed and purified MDH proteins from two societally relevant Bacillus spp. - B. safensis and B. subtilis -and characterized them biophysically (via Size Exclusion Chromatography-Small Angle X-ray Scattering (SEC-SAXS) and Differential Scanning Fluorimetry (DSF)) and enzymatically (via spectroscopic activity assays). As expected based on their high sequence identity, the two MDH orthologs had similar properties in most regards, including a tetrameric structure and high susceptibility to substrate inhibition. However, we uncovered differences in conditional thermal stability, in addition to subtle differences in enzymatic activity that offer insight into the workings of LDH-like MDH.
    Summary statement: Malate dehydrogenase (MDH) is a fundamental metabolic enzyme, from microbes to mammals, yet comparably little is known about microbial MDH, especially MDH of the tetrameric MDH3 class. We compare the biophysical and enzymatic properties of two such enzymes from the societally relevant bacterial species Bacillus subtilis and Bacillus safensis , offering useful insight with potential biotechnological implications.
    DOI:  https://doi.org/10.64898/2026.05.13.723581
  10. FEBS J. 2026 May 26.
    Transgenic selection and underlying mechanisms in apicomplexan parasites.
    Swaroop Peddiraju, Rakhee Lohia, Nishith Gupta.
      The field of apicomplexan transgenics has been transformed by selectable markers that couple metabolism, drug action, and genetic engineering. This review consolidates three decades of progress across model parasites, Toxoplasma, Plasmodium, Cryptosporidium, Neospora, Eimeria, Babesia, and Theileria, illustrating how selection markers have enabled genome engineering. We dissect the rationale and mechanisms underlying positive and negative drug selections and emphasize marker recycling. Practical guidance is paired with failure diagnostics that determine whether transgenic selections succeed in vitro or in vivo. Looking forward, we outline new directions for expanding the toolkit: exploiting auxotrophy, importing orthogonal resistance genes, and leveraging CRISPR-based marker-free editing. We discuss translational constraints, especially the need for self-excising or transient markers in vaccine research, adapting selection in nonmodel species and the value of selection marker cocktails for pathway-scale engineering. By integrating models, mechanisms, methods, and modalities, this article provides a rigorous framework for parasite engineering and a clear path to novel orthogonal, host-sparing selection strategies.
    Keywords:  Apicomplexa; marker recycling; positive–negative selection; purine metabolism; pyrimidine metabolism; selection markers; transgenics; translation inhibition markers
    DOI:  https://doi.org/10.1111/febs.70588
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