Genomic organization and expression of elongation factor-1 alpha genes in Trypanosoma brucei

Global Proteomic Analysis of Lysine Malonylation in Toxoplasma gondii

Lysine malonylation (Kmal) is a new post-translational modification (PTM), which has been reported in several prokaryotic and eukaryotic species. Although Kmal can regulate many and diverse biological processes in various organisms, knowledge about this important PTM in the apicomplexan parasite Toxoplasma gondii is limited. In this study, we performed the first global profiling of malonylated proteins in T. gondii tachyzoites using affinity enrichment and Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Three experiments performed in tandem revealed 294, 345, 352 Kmal sites on 203, 236, 230 malonylated proteins, respectively. Computational analysis showed the identified malonylated proteins to be localized in various subcellular compartments and involved in many cellular functions, particularly mitochondrial function. Additionally, one conserved Kmal motif with a strong bias for cysteine was detected. Taken together, these findings provide the first report of Kmal profile in T. gondii and should be an important resource for studying the physiological roles of Kmal in this parasite.

Characterization of the Activities of Dinuclear Thiolato-Bridged Arene Ruthenium Complexes against Toxoplasma gondii

The in vitro effects of 18 dinuclear thiolato-bridged arene ruthenium complexes (1 monohiolato compound, 4 dithiolato compounds, and 13 trithiolato compounds), originally designed as anticancer agents, on the apicomplexan parasite Toxoplasma gondii grown in human foreskin fibroblast (HFF) host cells were studied. Some trithiolato compounds exhibited antiparasitic efficacy at concentrations of 250 nM and below. Among those, complex 1 and complex 2 inhibited T. gondii proliferation with 50% inhibitory concentrations (IC₅₀s) of 34 and 62 nM, respectively, and they did not affect HFFs at dosages of 200 μM or above, resulting in selectivity indices of >23,000. The IC₅₀s of complex 9 were 1.2 nM for T. gondii and above 5 μM for HFFs. Transmission electron microscopy detected ultrastructural alterations in the matrix of the parasite mitochondria at the early stages of treatment, followed by a more pronounced destruction of tachyzoites. However, none of the three compounds applied at 250 nM for 15 days was parasiticidal. By affinity chromatography using complex 9 coupled to epoxy-activated Sepharose followed by mass spectrometry, T. gondii translation elongation factor 1α and two ribosomal proteins, RPS18 and RPL27, were identified to be potential binding proteins. In conclusion, organometallic ruthenium complexes exhibit promising activities against Toxoplasma, and the potential mechanisms of action of these compounds as well as their prospective applications for the treatment of toxoplasmosis are discussed.

Toxoplasma gondii Elongation Factor 1-Alpha (TgEF-1α) Is a Novel Vaccine Candidate Antigen against Toxoplasmosis

Toxoplasma gondii (T. gondii) is an obligate intracellular parasite which can infect almost all warm-blood animals, leading to toxoplasmosis. Screening and discovery of an effective vaccine candidate or new drug target is crucial for the control of this disease. In this study, the recombinant T. gondii elongation factor 1-alpha (rTgEF-1α) was successfully expressed in in Escherichia coli. Passive immunization of mice with anti-rTgEF-1α polyclonal antibody following challenge with a lethal dose of tachyzoites significantly increased the survival time compared with PBS control group. The survival time of mice challenged with tachyzoites pretreated with anti-rTgEF-1α PcAb also was significantly increased. Invasion of tachyzoites into mouse macrophages was significantly inhibited in the anti-rTgEF-1α PcAb pretreated group. Mice vaccinated with rTgEF-1α induced a high level of specific anti-T. gondii antibodies and production of IFN-gamma, interleukin-4. The expression levels of MHC-I and MHC-II molecules as well as the percentages of CD4⁺ and CD8⁺ T cells in mice vaccinated with rTgEF-1α was significantly increased, respectively (P < 0.05), compared with all the controls. Immunization with rTgEF-1α significantly (P < 0.05) prolonged survival time (14.53 ± 1.72 days) after challenge infection with the virulent T. gondii RH strain. These results indicate that T. gondii EF-1α plays an essential role in mediating host cell invasion by the parasite and, as such, could be a candidate vaccine antigen against toxoplasmosis.

Protective immunity against acute toxoplasmosis in BALB/c mice induced by a DNA vaccine encoding Toxoplasma gondii elongation factor 1-alpha

BACKGROUND

Toxoplasma gondii can infect almost all warm-blood animals including human beings. The high incidence and severe damage that can be caused by T. gondii infection clearly indicates the need for the development of a vaccine. T. gondii elongation factor 1-alpha (TgEF-1α) plays an important role in pathogenesis and host cell invasion for this parasite. The aim of this study was to evaluate the immune protective efficacy of a DNA vaccine encoding TgEF-1α gene against acute T. gondii infection in mice.

METHODS

A DNA vaccine (pVAX-EF-1α) encoding T. gondii EF-1a (TgEF-1α) gene was constructed and its immune response and protective efficacy against lethal challenge in BALB/c mice were evaluated.

RESULTS

Mice inoculated with the pVAX-EF-1α vaccine had a high level of specific anti-T. gondii antibodies and produced high levels of IFN-gamma, interleukin (IL)-4, and IL-17. The expression levels of MHC-I and MHC-II molecules as well as the percentages of both CD4(+) and CD8(+) T cells in mice vaccinated with pVAX-EF-1α were significantly increased (p < 0.05), compared with those in all the mice from control groups (blank control, PBS, and pVAXI). Immunization with pVAX-EF-1α significantly (p < 0.05) prolonged mouse survival time to 14.1 ± 1.7 days after challenge infection with the virulent T. gondii RH strain, compared with mice in the control groups which died within 8 days.

CONCLUSIONS

DNA vaccination with pVAX-EF-1α triggered strong humoral and cellular responses and induced effective protection in mice against acute T. gondii infection, indicating that TgEF-1α is a promising vaccine candidate against acute toxoplasmosis.

Elongation factor-1α is a novel protein associated with host cell invasion and a potential protective antigen of Cryptosporidium parvum

The phylum Apicomplexa comprises obligate intracellular parasites that infect vertebrates. All invasive forms of Apicomplexa possess an apical complex, a unique assembly of organelles localized to the anterior end of the cell and involved in host cell invasion. Previously, we generated a chicken monoclonal antibody (mAb), 6D-12-G10, with specificity for an antigen located in the apical cytoskeleton of Eimeria acervulina sporozoites. This antigen was highly conserved among Apicomplexan parasites, including other Eimeria spp., Toxoplasma, Neospora, and Cryptosporidium. In the present study, we identified the apical cytoskeletal antigen of Cryptosporidium parvum (C. parvum) and further characterized this antigen in C. parvum to assess its potential as a target molecule against cryptosporidiosis. Indirect immunofluorescence demonstrated that the reactivity of 6D-12-G10 with C. parvum sporozoites was similar to those of anti-β- and anti-γ-tubulins antibodies. Immunoelectron microscopy with the 6D-12-G10 mAb detected the antigen both on the sporozoite surface and underneath the inner membrane at the apical region of zoites. The 6D-12-G10 mAb significantly inhibited in vitro host cell invasion by C. parvum. MALDI-TOF/MS and LC-MS/MS analysis of tryptic peptides revealed that the mAb 6D-12-G10 target antigen was elongation factor-1α (EF-1α). These results indicate that C. parvum EF-1α plays an essential role in mediating host cell entry by the parasite and, as such, could be a candidate vaccine antigen against cryptosporidiosis.

Oscheius tipulae as an example of eEF1A gene diversity in nematodes

We characterized four eEF1A genes in the alternative rhabditid nematode model organism Oscheius tipulae. This is twice the copy number of eEF1A genes in C. elegans, C. briggsae, and, probably, many other free-living and parasitic nematodes. The introns show features remarkably different from those of other metazoan eEF1A genes. Most of the introns in the eEF1A genes are specific to O. tipulae and are not shared with any of the other genes described in metazoans. Most of the introns are phase 0 (inserted between two codons), and few are inserted in protosplice sites (introns inserted between the nucleotide sequence A/CAG and G/A). Two of these phase 0 introns are conserved in sequence in two or more of the four eEF1A gene copies, and are inserted in the same position in the genes. Neither of these characteristics has been detected in any of the nematode eEF1A genes characterized to date. The coding sequences were also compared with other eEF1A cDNAs from 11 different nematodes to determine the variability of these genes within the phylum Nematoda. Parsimony and distance trees yielded similar topologies, which were similar to those created using other molecular markers. The presence of more than one copy of the eEF1A gene with nearly identical coding regions makes it difficult to define the orthologous cDNAs. As shown by our data on O. tipulae, careful and extensive examination of intron positions in the eEF1A gene across the phylum is necessary to define their potential for use as valid phylogenetic markers.

Nuclear calcium flux in Trypanosoma brucei can be quantified with targeted aequorin

The following study was undertaken to determine if calcium ions move from the plasma membrane to the nucleus of Trypanosoma brucei. Nuclear and cytosolic calcium flux was measured with the calcium sensitive photoprotein, aequorin which was targeted to various locations in stably transformed procyclic cells. Immunoblots revealed that the recombinant proteins, CYT-AEQ and NUC-AEQ were translated in transformants, and that CYT-AEQ was contained in a soluble fraction. Immunolocalization demonstrated that NUC-AEQ was contained within the trypanosome nucleus. To evaluate calcium movement from the plasma membrane to the nucleus in live trypanosomes, aequorin was reconstituted in vivo with coelenterazine and luminescence was recorded. The resting levels of [Ca2+]cyt and [Ca2+]nuc were similar (314 +/- 43 and 287 +/- 28 nM, respectively). When calcium influx across the plasma membrane was initiated with 2 microM ionomycin, [Ca2+]cyt and [Ca2+]nuc each became elevated in parallel to a new steady state which was approximately 2-fold above the resting level. Compound 48/80 initiated a calcium flux across the plasma membrane by a different mechanism from ionomycin, and in a manner that was inhibited by the calcium channel antagonist, La3+. Compound 48/80 (8 micrograms/ml) transiently elevated [Ca2+]cyt to 1.73 +/- 0.3 microM over the course of 20 s, and also generated a transient rise in [Ca2+]nuc which peaked at 1.32 + 0.29 microM over the same time course. Overall, these data demonstrate that calcium moves into and out of the trypanosome nucleus in a manner which closely parallels changes in [Ca2+]cyt. A small calcium ion gradient between nucleus and cytoplasm was also observed.