The dense granule of Toxoplasma gondii is a secretory vesicular organelle of which the proteins participate in the modification of the parasitophorous vacuole (PV) and PV membrane for the maintenance of intracellular parasitism in almost all nucleated host cells. In this review, the archives on the research of GRA proteins are reviewed on the foci of finding GRA proteins, characterizing molecular aspects, usefulness in diagnostic antigen, and vaccine trials in addition to some functions in host-parasite interactions.
Animals ; Antigens, Protozoan/*metabolism ; Cytoplasmic Granules/metabolism ; *Host-Parasite Interactions ; Humans ; Protozoan Proteins/*metabolism ; Toxoplasma/*metabolism ; Toxoplasmosis/*parasitology ; Vacuoles/*metabolism

The vir genes are antigenic genes and are considered to be possible vaccine targets. Since India is highly endemic to Plasmodium vivax, we sequenced 5 different vir genes and investigated DNA sequence variations in 93 single-clonal P. vivax isolates. High variability was observed in all the 5 vir genes; the vir 1/9 gene was highly diverged across Indian populations. The patterns of genetic diversity do not follow geographical locations, as geographically distant populations were found to be genetically similar. The results in general present complex genetic diversity patterns in India, requiring further in-depth population genetic and functional studies.
Antigens, Protozoan/*genetics ; Humans ; India/epidemiology ; Malaria, Vivax/epidemiology/parasitology ; Phylogeny ; Plasmodium vivax/*genetics ; *Polymorphism, Genetic ; Protozoan Proteins/genetics/*metabolism

OBJECTIVETo characterize the immune response induced by SAG1 encoding plasmid combined with IL-2 gene adjuvant in mice and to assess the protective effect of this vaccination against toxoplasmosis.

METHODSMice were co-injected intramuscularly with plasmid encoding Toxoplasma gondii SAG1 plus murine IL-2 expression vector at a dose of 100 microg. Booster immunizations were employed 2 more times at 3-week interval. As controls, mice were inoculated with PBS or empty plasmid pcDNA3. Humoral and cellular responses were assayed using ELISA for the determination of Ab, Ab isotype and IFN-gamma, as well as IL-4. To detect the integration and dissemination of DNA in the injected mice, PCR and in situ hybridization were performed. All mice were then infected with highly virulent RH tachyzoites of Toxoplasma gondii intraperitoneally.

RESULTSSignificant increases in specific IgG levels were observed in mice after immunization three times with SAG1 expression plasmid. With respect to the IgG isotype, co-inoculation of IL-2 expression plasmid enhanced the level of IgG2a and the production of IFN-gamma. Challenging mice by vaccinating with combined plasmids with RH tachyzoites resulted in prolonged survival.

CONCLUSIONHumoral and cytokine responses elicited by SAG1 DNA immunization can be modulated by co-inoculation with IL-2 expression plasmid. The use of DNA vaccine in combination with an appropriate cytokine gene to prevent T. gondii infection warrants further investigation.

Animals ; Antibodies, Protozoan ; blood ; Antigens, Protozoan ; Cytokines ; biosynthesis ; Female ; Immunization ; Immunoglobulin G ; blood ; classification ; Interleukin-2 ; genetics ; Mice ; Protozoan Proteins ; genetics ; Protozoan Vaccines ; immunology ; Toxoplasma ; immunology ; Toxoplasmosis, Animal ; prevention & control ; Vaccines, DNA ; immunology

The objective of this study was to construct and express recombinant prokaryotic plasmid pET32a (+)- ast1 in E. coli BL21(DE3). Amastin gene was amplified from genomic DNA of Leishmania Donovani and its transmembran region was predicted by the methods of SOSUI and Tmpred; astl located in N-terminus of amastin gene was amplified and cloned into prokaryotic plasmid pET32a(+), which was named pET32a(+)-ast1, and then rAST1 was expressed in E. coli BL21(DE3). The results of SDS-PAGE and immunobloting assay showed that a fusion protein rAST1 (relative molecular mass about 27 kDa) was able to express in BL21. The recombinant prokaryotic plasmid pET32a(+)- ast1 was successfully constructed, and noted to be efficiently expressed in E. coli BL21(DE3).
Animals ; Cloning, Molecular ; Escherichia coli ; genetics ; metabolism ; Extracellular Space ; Genes, Protozoan ; Leishmania donovani ; genetics ; Plasmids ; genetics ; Protozoan Proteins ; biosynthesis ; genetics ; Recombinant Fusion Proteins ; biosynthesis ; genetics

A Cryptosporidium parvum sporozoite and oocyst lambda gt11 cDNA library was screened with a hyperimmune rabbit serum that was developed against insoluble fragments of ultrasonicated oocysts. A clone named Cp22.4.1 encoding a protein of 231 amino acids with 4 zinc-finger domains characterized by a Cys-X2-Cys-X4-His-X4-Cys motif was isolated and characterized. There was a complete match between the sequencing data of the coding region of Cp22.4.1 and the corresponding gene at chromosomal level. Cloning in a pBAD-TOPO-TA expression vector permitted to evaluate the antigenicity of the recombinant His-tagged antigen. This antigen was recognized by 2 out of 5 sera from Cryptosporidium immune calves and not by sera from parasite naive animals.
Amino Acid Sequence ; Animals ; Antibodies, Protozoan/*blood ; Antigens, Protozoan/chemistry/*immunology ; Base Sequence ; Cattle/*immunology ; Cryptosporidium parvum/*immunology ; Molecular Sequence Data ; Protozoan Proteins/chemistry/genetics ; Rabbits ; Recombinant Proteins ; Zinc Fingers/genetics/*immunology

Serologic tests are widely accepted for diagnosing Toxoplasma gondii but purification and standardization of antigen needs to be improved. Recently, surface tachyzoite and bradyzoite antigens have become more attractive for this purpose. In this study, diagnostic usefulness of 3 recombinant antigens (SAG1, SAG2, and SAG3) were evaluated, and their efficacy was compared with the available commercial ELISA. The recombinant plasmids were transformed to JM109 strain of Escherichia coli, and the recombinants were expressed and purified. Recombinant SAG1, SAG2, and SAG3 antigens were evaluated using different groups of sera in an ELISA system, and the results were compared to those of a commercial IgG and IgM ELISA kit. The sensitivity and specificity of recombinant surface antigens for detection of anti-Toxoplasma IgG in comparison with commercially available ELISA were as follows: SAG1 (93.6% and 92.9%), SAG2 (100.0% and 89.4%), and SAG3 (95.4% and 91.2%), respectively. A high degree of agreement (96.9%) was observed between recombinant SAG2 and commercial ELISA in terms of detecting IgG anti-Toxoplasma antibodies. P22 had the best performance in detecting anti-Toxoplasma IgM in comparison with the other 2 recombinant antigens. Recombinant SAG1, SAG2, and SAG3 could all be used for diagnosis of IgG-specific antibodies against T. gondii.
Antibodies, Protozoan/*blood ; Antigens, Protozoan/diagnostic use/*genetics ; Enzyme-Linked Immunosorbent Assay ; Humans ; Immunoglobulin G/blood ; Immunoglobulin M/blood ; Membrane Glycoproteins/*genetics ; Protozoan Proteins/*genetics ; Recombinant Proteins/diagnostic use/immunology ; Sensitivity and Specificity ; Toxoplasma/immunology ; Toxoplasmosis/blood/*diagnosis

The nfa1 gene was cloned from a cDNA library of pathogenic Naegleria fowleri by immunoscreening; it consisted of 360 bp and produced a 13.1 kDa recombinant protein (rNfa1) that showed the pseudopodia-specific localization by immunocytochemistry in the previous study. Based on the idea that the pseudopodia-specific Nfa1 protein mentioned above seems to be involved in the pathogenicity of N. fowleri, we observed the effect of an anti-Nfa1 antibody on the proliferation of N. fowleri trophozoites and the cytotoxicity of N. fowleri trophozoites on the target cells. The proliferation of N. fowleri trophozoites was inhibited after being treated with an anti-Nfa1 polyclonal antibody in a dose-dependent manner for 48 hrs. By a light microscope, CHO cells co-cultured with N. fowleri trophozoites (group I) for 48 hrs showed severe morphological destruction. On the contrary, CHO cells co-cultured with N. fowleri trophozoites and anti-Nfa1 polyclonal antibody (1: 100 dilution) (group II) showed less destruction. In the LDH release assay results, group I showed 50.6% cytotoxicity, and group II showed 39.3%. Consequently, addition of an anti-Nfa1 polyclonal antibody produced a decreasing effect of in vitro cytotoxicity of N. fowleri in a dosedependent manner.
Animals ; Antibodies, Protozoan/*immunology ; Antigens, Protozoan/genetics/*immunology ; CHO Cells ; Dose-Response Relationship, Immunologic ; Female ; Hamsters ; Mice ; Mice, Inbred BALB C ; Naegleria fowleri/growth & development/immunology/*pathogenicity ; Protozoan Proteins/genetics/*immunology ; Recombinant Proteins/immunology ; Support, Non-U.S. Gov't

Endoplasmic Reticulum ; genetics ; metabolism ; Plasmodium berghei ; genetics ; metabolism ; Plasmodium falciparum ; genetics ; metabolism ; Protozoan Proteins ; genetics ; metabolism

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*

OBJECTIVETo establish an tachyzoite-brachyzoite interconversion system for Toxoplasma gondii RH strain in vitro.

METHODSCOS-7 cells were inoculated with purified tachyzoites of T.gondii RH strain and cultured in vitro. The morphology of the cultured cells and parasites was observed and the total cellular RNA extracted on days 1 to 6 following the inoculation for detecting the expression of tachyzoite-specific protein (SAG1) and bradyzoite-specific proteins (BAG1 and SAG2C) using RT-PCR.

RESULTSWith the passage of time, the number of parasites in COS-7 cells increased but the proliferation rate was lowered gradually. The intracellular tachyzoites proliferated by means of budding and binary fission, which led to the changes in the alignment of the parasites in the cells from curved pairs, rosette or clustered, and semi-circular patterns to spherical encapsulation-like structures. These changes indicated the gradual transformation of the tachyzoites into bradyzoites. The expressions of the tachyzoite-specific SAG1 gene were detected throughout the 6 days of in vitro culture. The expression of the bradyzoite-specific BAG1 gene had been detected since the second day after the inoculation and SAG2C gene since the fifth day. Alteration of the culture condition resulted in gradual transformation of the bradyzoites into tachyzoites.

CONCLUSIONAn in vitro tachzoites-bradyzoite interconversion system for T.gondii has been successfully established, which provides the basis for further study of the mechanism of interconversion.

Animals ; COS Cells ; Cell Culture Techniques ; Cercopithecus aethiops ; Cysts ; Female ; Genes, Protozoan ; genetics ; Host-Parasite Interactions ; Mice ; Protozoan Proteins ; biosynthesis ; genetics ; Toxoplasma ; growth & development ; physiology