Intracellular Theileria Parasites PIN Down Host Metabolism

Theileria annulata subtelomere-encoded variable secreted protein-TA05560 interacts with bovine RNA binding motif protein 39 (RBM39)

Theileria annulata is the only eukaryotic pathogen able to transform bovine leukocytes, including B cells, macrophages and dendritic cells. T. annulata-transformed cells exhibit several cancer-like phenotypes, such as hyperproliferation, immortalization and dissemination. Although several parasite factors involved in bovine cell transformation have been explored, the roles of subtelomere-encoded variable secreted proteins (SVSPs) of the parasite in host-cell interactions are largely unknown. In the present study, the target molecule TA05560, a member of the SVSP multigene family of T. annulata, was identified at the mRNA level during different life cycles through a quantitative real-time PCR assay, and the subcellular distribution of TA05560 was examined via confocal microscopy. The results showed that the parasite molecule TA05560 was transcribed mainly in the schizont stage of T. annulata infection, and the protein was distributed in the nucleus and cytoplasm of the parasitized cells. The potential host cell proteins that interact with TA05560 were screened using the yeast two-hybrid system, and the direct interaction between TA05560 and its prey protein, Bos taurus RNA binding motif protein 39 (RBM39) was further identified in HEK293T cells by using confocal microscopy, coimmunoprecipitation and bimolecular fluorescence complementation assays. Moreover, the interaction between TA05560 and its host protein was observed in T. annulata-infected cells via confocal microscopy. Therefore, our study is the first to show that the T. annulata-secreted TA05560 protein directly binds to both the exogenous and endogenous host cell molecule RBM39, laying the foundation for exploring host-parasite interactions and understanding the transformation mechanisms induced by T. annulata and other transforming parasites.

Theileria parasites sequester host eIF5A to escape elimination by host-mediated autophagy

Intracellular pathogens develop elaborate mechanisms to survive within the hostile environments of host cells. Theileria parasites infect bovine leukocytes and cause devastating diseases in cattle in developing countries. Theileria spp. have evolved sophisticated strategies to hijack host leukocytes, inducing proliferative and invasive phenotypes characteristic of cell transformation. Intracellular Theileria parasites secrete proteins into the host cell and recruit host proteins to induce oncogenic signaling for parasite survival. It is unknown how Theileria parasites evade host cell defense mechanisms, such as autophagy, to survive within host cells. Here, we show that Theileria annulata parasites sequester the host eIF5A protein to their surface to escape elimination by autophagic processes. We identified a small-molecule compound that reduces parasite load by inducing autophagic flux in host leukocytes, thereby uncoupling Theileria parasite survival from host cell survival. We took a chemical genetics approach to show that this compound induced host autophagy mechanisms and the formation of autophagic structures via AMPK activation and the release of the host protein eIF5A which is sequestered at the parasite surface. The sequestration of host eIF5A to the parasite surface offers a strategy to escape elimination by autophagic mechanisms. These results show how intracellular pathogens can avoid host defense mechanisms and identify a new anti-Theileria drug that induces autophagy to target parasite removal.

Novel secretory organelles of parasite origin - at the center of host-parasite interaction

Reorganization of cell organelle-deprived host red blood cells by the apicomplexan malaria parasite Plasmodium falciparum enables their cytoadherence to endothelial cells that line the microvasculature. This increases the time red blood cells infected with mature developmental stages remain within selected organs such as the brain to avoid the spleen passage, which can lead to severe complications and cumulate in patient death. The Maurer's clefts are a novel secretory organelle of parasite origin established by the parasite in the cytoplasm of the host red blood cell in order to facilitate the establishment of cytoadherence by conducting the trafficking of immunovariant adhesins to the host cell surface. Another important function of the organelle is the sorting of other proteins the parasite traffics into its host cell. Although the organelle is of high importance for the pathology of malaria, additional putative functions, structure, and genesis remain shrouded in mystery more than a century after its discovery. In this review, we highlight our current knowledge about the Maurer's clefts and other novel secretory organelles established within the host cell cytoplasm by human-pathogenic malaria parasites and other parasites that reside within human red blood cells.

Cancerogenic parasites in veterinary medicine: a narrative literature review

Parasite infection is one of the many environmental factors that can significantly contribute to carcinogenesis and is already known to be associated with a variety of malignancies in both human and veterinary medicine. However, the actual number of cancerogenic parasites and their relationship to tumor development is far from being fully understood, especially in veterinary medicine. Thus, the aim of this review is to investigate parasite-related cancers in domestic and wild animals and their burden in veterinary oncology. Spontaneous neoplasia with ascertained or putative parasite etiology in domestic and wild animals will be reviewed, and the multifarious mechanisms of protozoan and metazoan cancer induction will be discussed.

Trifloxystrobin blocks the growth of Theileria parasites and is a promising drug to treat Buparvaquone resistance

Theileria parasites are responsible for devastating cattle diseases, causing major economic losses across Africa and Asia. Theileria spp. stand apart from other apicomplexa parasites by their ability to transform host leukocytes into immortalized, hyperproliferating, invasive cells that rapidly kill infected animals. The emergence of resistance to the theilericidal drug Buparvaquone raises the need for new anti-Theileria drugs. We developed a microscopy-based screen to reposition drugs from the open-access Medicines for Malaria Venture (MMV) Pathogen Box. We show that Trifloxystrobin (MMV688754) selectively kills lymphocytes or macrophages infected with Theileria annulata or Theileria parva parasites. Trifloxystrobin treatment reduced parasite load in vitro as effectively as Buparvaquone, with similar effects on host gene expression, cell proliferation and cell cycle. Trifloxystrobin also inhibited parasite differentiation to merozoites (merogony). Trifloxystrobin inhibition of parasite survival is independent of the parasite TaPin1 prolyl isomerase pathway. Furthermore, modeling studies predicted that Trifloxystrobin and Buparvaquone could interact distinctly with parasite Cytochrome B and we show that Trifloxystrobin was still effective against Buparvaquone-resistant cells harboring TaCytB mutations. Our study suggests that Trifloxystrobin could provide an effective alternative to Buparvaquone treatment and represents a promising candidate for future drug development against Theileria spp.

Theileria annulata SVSP455 interacts with host HSP60

Background

Theileria annulata, a transforming parasite, invades bovine B cells, dendritic cells and macrophages, promoting the uncontrolled proliferation of these cells. This protozoan evolved intricate strategies to subvert host cell signaling pathways related to antiapoptotic signaling to enable survival and proliferation within the host cells. However, the molecular mechanisms of the cell transformation induced by T. annulata remain largely unclear. Although some studies have predicted that the subtelomere-encoded variable secreted protein (SVSP) family plays roles in host-parasite interactions, the evidence for this is limited.

Methods

In the present study, the SVSP455 (TA05545) gene, a member of the SVSP gene family, was used as the target molecule. The expression pattern of SVSP455 in different life-cycle stages of T. annulata infection was explored using a quantitative real-time PCR assay, and the subcellular distribution of SVSP455 was observed using confocal microscopy. The host cell proteins interacting with SVSP455 were screened using the Y2H system, and their interactions were verified in vivo and in vitro using both bimolecular fluorescence complementation and confocal microscopy, and co-immunoprecipitation assays. The role played by SVSP455 in cell transformation was further explored by using overexpression, RNA interference and drug treatment experiments.

Results

The highest level of the SVSP455 transcript was detected in the schizont stage of T. annulata, and the protein was located both on the surface of schizonts and in the host cell cytoplasm. In addition, the interaction between SVSP455 and heat shock protein 60 was shown in vitro, and their link may regulate host cell apoptosis in T. annulata-infected cells.

Conclusion

Our findings are the first to reveal that T. annulata-secreted SVSP455 molecule directly interacts with both exogenous and endogenous bovine HSP60 protein, and that the interaction of SVSP455-HSP60 may manipulate the host cell apoptosis signaling pathway. These results provide insights into cancer-like phenotypes underlying Theilera transformation and therapeutics for protection against other pathogens.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05427-z.

Quantitative Proteomics Reveals Metabolic Reprogramming in Host Cells Induced by Trophozoites and Intermediate Subunit of Gal/GalNAc Lectins from Entamoeba histolytica

Entamoeba histolytica is an intestinal protozoan parasite with remarkable ability to kill and phagocytose host cells, causing amoebic colitis and extraintestinal abscesses. The intermediate subunit (Igl) of galactose (Gal)- and N-acetyl-d-galactosamine (GalNAc)-specific lectins is considered an important surface antigen involved in the pathogenesis of E. histolytica. Here, we applied mass spectrometry-based quantitative proteomics technology to analyze the protein expression profile changes occurring in host Caco2 cells incubated with E. histolytica trophozoites or stimulated by purified native Igl protein. The expression levels of 1,490 and 489 proteins were significantly altered in the E. histolytica-treated and Igl-treated groups, respectively, among 6,875 proteins totally identified. Intriguingly, central carbon metabolism of host cells was suppressed in both E. histolytica-treated and Igl-treated groups, with evidence of decreased expression levels of several key enzymes, including pyruvate kinase muscle type 2, presenting a Warburg-like effect in host cells. Besides, Igl had potential physical interactions with central carbon metabolism enzymes and the proteolytic degradation family members proteasome subunit alpha and beta, which may be responsible for the degradation of key enzymes in carbon metabolism. These results provided a novel perspective on the pathogenic mechanism of E. histolytica and compelling evidence supporting the important role of Igl in the virulence of E. histolytica.

IMPORTANCE Metabolic reprogramming is considered a hallmark of some infectious diseases. However, in amoebiasis, a neglected tropical disease caused by protozoan parasite E. histolytica, metabolic changes in host cells have yet to be proven. In this study, advanced data-independent acquisition mass spectrometry-based quantitative proteomics was applied to investigate the overall host cellular metabolic changes as high-throughput proteomics could measure molecular changes in a cell or tissue with high efficiency. Enrichment analysis of differentially expressed proteins showed biological processes and cellular pathways related to amoeba infection and Igl cytotoxicity. Specifically, central carbon metabolism of host cells was dramatically suppressed in both E. histolytica-treated and Igl-treated groups, indicating the occurrence of a Warburg-like effect induced by trophozoites or Igl from E. histolytica. Distinct differences in ubiquitin-mediated proteolysis, rapamycin (mTOR) signaling pathway, autophagy, endocytosis, and tight junctions provided novel perspectives on the pathogenic mechanism of E. histolytica.

Acute insulin-responsive hyperglycemia and hypocalcemia in Theileria spp. infected goat

Theileriosis can be manifested in appreciably variable clinical forms among domestic ruminants and may often become life-threatening. The present report narrates, the quick remarkable clinical recovery of a lactating goat infected with Theileria spp., exhibiting acute insulin-responsive hyperglycemia and hypocalcemia, by providing intensive therapy. A four year old doe was presented with the complaint of acute manifestation of weakness, ventroflexion of neck with flaccid muscles, recumbency, hypersalivation, severe abdominal breathing, anorexia and polyuria since last eighteen hours. The animal kidded three kids one month before, out of which one was mummified. Clinical examination revealed severe depression, dehydration, dyspnoea, congested mucous membrane, sluggish rumen motility and reduced pupillary light reflex. Laboratory investigation revealed severe granulocytopenia, thrombocytopenia, hypocalcemia, hyperglycemia and Theileria spp. infection. The animal showed significant improvement within a few minutes of initiating the evidence-based stabilization therapy to correct hydration status, cellular glucose uptake, calcium levels and Theileria spp. infection. This case indicates the significance of investigating the metabolic status of animals suffering from theileriosis for achieving better clinical responses. Also, future studies may focus on the endocrinological perspectives of metabolic impact of Theileria spp. infection in goats.

Screening and identification of Theileria annulata subtelomere-encoded variable secreted protein-950454 (SVSP454) interacting proteins from bovine B cells

BACKGROUND

Theileria annulata is a protozoan parasite that can infect and transform bovine B cells, macrophages, and dendritic cells. The mechanism of the transformation is still not well understood, and some parasite molecules have been identified, which contribute to cell proliferation by regulating host signaling pathways. Subtelomeric variable secreted proteins (SVSPs) of Theileria might affect the host cell phenotype, but its function is still not clear. Therefore, in the present study, we explored the interactions of SVSP454 with host cell proteins to investigate the molecular mechanism of T. annulata interaction with host cells.

METHODS

The transcription level of an SVSP protein from T. annulata, SVSP454, was analyzed between different life stages and transformed cell passages using qRT-PCR. Then, SVSP454 was used as a bait to screen its interacting proteins from the bovine B cell cDNA library using a yeast two-hybrid (Y2H) system. The potential interacting proteins of host cells with SVSP454 were further identified by using a coimmunoprecipitation (Co-IP) and bimolecular fluorescence complementation (BiFC) assays.

RESULTS

SVSP454 was transcribed in all three life stages of T. annulata but had the highest transcription during the schizont stage. However, the transcription level of SVSP454 continuously decreased as the cultures passaged. Two proteins, Bos Taurus coiled-coil domain 181 (CCDC181) and Bos Taurus mitochondrial ribosomal protein L30 (MRPL30), were screened. The proteins CCDC181 and MRPL30 of the host were further identified to directly interact with SVSP454.

CONCLUSION

In the present study, SVSP454 was used as a bait plasmid, and its prey proteins CCDC181 and MRPL30 were screened out by using a Y2H system. Then, we demonstrated that SVSP454 directly interacted with both CCDC181 and MRPL30 by Co-IP and BiFC assays. Therefore, we speculate that SVSP454-CCDC181/SVSP454MRPL30 is an interacting axis that regulates the microtubule network and translation process of the host by some vital signaling molecules. Identification of the interaction of SVSP454 with CCDC181 and MRPL30 will help illustrate the transformation mechanisms induced by T. annulata.

Dynamic methylation of histone H3K18 in differentiating Theileria parasites

Lysine methylation on histone tails impacts genome regulation and cell fate determination in many developmental processes. Apicomplexa intracellular parasites cause major diseases and they have developed complex life cycles with fine-tuned differentiation events. Yet, apicomplexa genomes have few transcription factors and little is known about their epigenetic control systems. Tick-borne Theileria apicomplexa species have relatively small, compact genomes and a remarkable ability to transform leucocytes in their bovine hosts. Here we report enriched H3 lysine 18 monomethylation (H3K18me1) on the gene bodies of repressed genes in Theileria macroschizonts. Differentiation to merozoites (merogony) leads to decreased H3K18me1 in parasite nuclei. Pharmacological manipulation of H3K18 acetylation or methylation impacted parasite differentiation and expression of stage-specific genes. Finally, we identify a parasite SET-domain methyltransferase (TaSETup1) that can methylate H3K18 and represses gene expression. Thus, H3K18me1 emerges as an important epigenetic mark which controls gene expression and stage differentiation in Theileria parasites.

Theileria annulata Subtelomere-Encoded Variable Secreted Protein-TA05575 Binds to Bovine RBMX2

Tropical theileriosis is the disease caused by tick-transmitted apicomplexan parasite Theileria annulata, which has ability to transform bovine leukocytes, including B cells, macrophage cells, and dendritic cells. The T. annulata transformed cells are characterized as uncontrolled proliferation and shared some cancer-like phenotypes. The mechanism of the transformation by T. annulata is still not understood well. In previous reports, the subtelomere-encoded variable secreted proteins (SVSP) of T. parva were considered to contribute to phenotypic changes of the host cell, but the role of SVSP of T. annulata in host-pathogen relationship remains unknown. In the present study, a member of SVSP family, TA05575 of T. annulata was selected as the target molecule to analyze its expression profiles in different life cycle stages of T. annulata by qPCR and investigate its subcellular distribution of different passages of T. annulata transformed cells using confocal experiments. From the results, the transcription level of TA05575 at schizont stage was significantly higher than the other two life stages of T. annulata, and the protein of TA05575 was mainly distributed in nucleus of T. annulata infected cells. In addition, the potential proteins of host cells interacting with TA05575 were screened by Yeast-two hybrid system. The results of Co-IP experiment confirmed that TA05575 interacted with RBMX2-like protein that participated in transcription regulation of cells. In addition, a novel BiFC assay and flow cytometry were carried out, and the results further revealed that TA05575-RBMX2-like pair was directly interacted in cell context. Moreover, this interacting pair was found to distribute in intracellular compartments of HEK293T cells by using confocal microscopy. The results of the present study suggest that TA05575 may contribute for cells transformation due its distribution. According to the function of RBMX2, the interaction of TA05575 and RMMX2-like will provide a new information to further understand the mechanisms of cells transformation by T. annulata.