[Show abstract][Hide abstract] ABSTRACT: Clathrin-mediated vesicular trafficking, the mechanism by which proteins and lipids are transported between membrane-bound organelles, accounts for a large proportion of import from the plasma membrane (endocytosis) and transport from the trans-Golgi network towards the endosomal system. Clathrin-mediated events are still poorly understood in the protozoan Trypanosoma cruzi, the causative agent of Chagas disease in Latin America. In this study, clathrin heavy (TcCHC) and light (TcCLC) chain gene expression and protein localization were investigated in different developmental forms of T. cruzi (epimastigotes, trypomastigotes and amastigotes), using both polyclonal and monoclonal antibodies raised against T. cruzi recombinant proteins.
[Show abstract][Hide abstract] ABSTRACT: Gene knockout is a widely used approach to evaluate loss-of-function phenotypes and it can be facilitated by the incorporation of a DNA cassette having a drug-selectable marker. Confirmation of the correct knockout cassette insertion is an important step in gene removal validation and has generally been performed by polymerase chain reaction (PCR) assays following a time-consuming DNA extraction step. Here, we show a rapid procedure for the identification of Trypanosoma cruzi transfectants by PCR directly from liquid culture - without prior DNA extraction. This simple approach enabled us to generate PCR amplifications from different cultures varying from 106-108 cells/mL. We also show that it is possible to combine different primer pairs in a multiplex detection reaction and even to achieve knockout confirmation with an extremely simple interpretation of a real-time PCR result. Using the "culture PCR" approach, we show for the first time that we can assess different DNA sequence combinations by PCR directly from liquid culture, saving time in several tasks for T. cruzi genotype interrogation.
Memórias do Instituto Oswaldo Cruz 06/2014; · 1.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Heteroxenic and monoxenic trypanosomatids were screened for the presence of actin using a mouse polyclonal antibody produced against the entire sequence of the Trypanosoma cruzi actin gene, encoding a 41.9 kDa protein. Western blot analysis showed that this antibody reacted with a polypeptide of approximately 42 kDa in the whole-cell lysates of parasites targeting mammals (T. cruzi, Trypanosoma brucei and Leishmania major), insects (Angomonas deanei, Crithidia fasciculata, Herpetomonas samuelpessoai and Strigomonas culicis) and plants (Phytomonas serpens). A single polypeptide of approximately 42 kDa was detected in the whole-cell lysates of T. cruzi cultured epimastigotes, metacyclic trypomastigotes and amastigotes at similar protein expression levels. Confocal microscopy showed that actin was expressed throughout the cytoplasm of all the tested trypanosomatids. These data demonstrate that actin expression is widespread in trypanosomatids.
Memórias do Instituto Oswaldo Cruz 08/2013; 108(5):631-6. · 1.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Trypanosoma cruzi is the etiological agent of Chagas disease, an illness that affects about 10 million people, mostly in South America, for which there is no effective treatment or vaccine. In this context, transgenic parasites expressing reporter genes are interesting tools for investigating parasite biology and host-parasite interactions, with a view to developing new strategies for disease prevention and treatment. We describe here the construction of a stably transfected fluorescent T. cruzi clone in which the GFP gene is integrated into the chromosome carrying the ribosomal cistron in T. cruzi Dm28c. This fluorescent T. cruzi produces detectable amounts of GFP only at replicative stages (epimastigote and amastigote), consistent with the larger amounts of GFP mRNA detected in these forms than in the non replicative trypomastigote stages. The fluorescence signal was also strongly correlated with the total number of parasites in T. cruzi cultures, providing a simple and rapid means of determining the growth inhibitory dose of anti-T.cruzi drugs in epimastigotes, by fluorometric microplate screening, and in amastigotes, by the flow cytometric quantification of T. cruzi-infected Vero cells. This fluorescent T. cruzi clone is, thus, an interesting tool for unbiased detection of the proliferating stages of the parasite, with multiple applications in the genetic analysis of T. cruzi, including analyses of host-parasite interactions, gene expression regulation and drug development.
PLoS ONE 06/2013; 8(6):e67441. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Protein tyrosine phosphatases (PTPs) play an essential role in the regulation of cell differentiation in pathogenic trypanosomatids. In this study, we describe a PTP expressed by the non-pathogenic protozoan Trypanosoma rangeli (TrPTP2). The gene for this PTP is orthologous to the T. brucei TbPTP1 and Trypanosoma cruzi (TcPTP2) genes. Cloning and expression of the TrPTP2 and TcPTP2 proteins allowed anti-PTP2 monoclonal antibodies to be generated in BALB/c mice. When expressed by T. rangeli epimastigotes and trypomastigotes, native TrPTP2 is detected as a ~65 kDa protein associated with the parasite's flagellum. Given that the flagellum is an important structure for cell differentiation in trypanosomatids, the presence of a protein responsible for tyrosine dephosphorylation in the T. rangeli flagellum could represent an interesting mechanism of regulation in this structure.
Memórias do Instituto Oswaldo Cruz 09/2012; 107(6):713-9. · 1.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Trypanosomes are parasitic protozoa in which gene expression is primarily controlled through the regulation of mRNA stability and translation. This post-transcriptional control is mediated by various families of RNA-binding proteins, including those with zinc finger CCCH motifs. CCCH zinc finger proteins have been shown to be essential to differentiation events in trypanosomatid parasites. Here, we functionally characterise TcZFP2 as a predicted post-transcriptional regulator of differentiation in Trypanosoma cruzi. This protein was detected in cell culture-derived amastigotes and trypomastigotes, but it was present in smaller amounts in metacyclic trypomastigote forms of T. cruzi. We use an optimised recombinant RNA immunopreciptation followed by microarray analysis assay to identify TcZFP2 target mRNAs. We further demonstrate that TcZFP2 binds an A-rich sequence in which the adenosine residue repeats are essential for high-affinity recognition. An analysis of the expression profiles of the genes encoding the TcZFP2-associated mRNAs throughout the parasite life cycle by microarray hybridisation showed that most of the associated mRNAs were upregulated in the metacyclic trypomastigote forms, also suggesting a role for TcZFP2 in metacyclic trypomastigote differentiation. Knockdown of the orthologous Trypanosoma brucei protein levels showed ZFP2 to be a positive regulator of specific target mRNA abundance.
Memórias do Instituto Oswaldo Cruz 09/2012; 107(6):790-9. · 1.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Proteasomes are large protein complexes, whose main function is to degrade unnecessary or damaged proteins. The inhibition of proteasome activity in Trypanosoma cruzi blocks parasite replication and cellular differentiation. We demonstrate that proteasome-dependent proteolysis occurs during the cellular differentiation of T. cruzi from replicative non-infectious epimastigotes to non-replicative and infectious trypomastigotes (metacyclogenesis). No peaks of ubiquitin-mediated degradation were observed and the profile of ubiquitinated conjugates was similar at all stages of differentiation. However, an analysis of carbonylated proteins showed significant variation in oxidized protein levels at the various stages of differentiation and the proteasome inhibition also increased oxidized protein levels. Our data suggest that different proteasome complexes coexist during metacyclogenesis. The 20S proteasome may be free or linked to regulatory particles (PA700, PA26 and PA200), at specific cell sites and the coordinated action of these complexes would make it possible for proteolysis of ubiquitin-tagged proteins and oxidized proteins, to coexist in the cell.
PLoS ONE 06/2011; 6(6):e21027. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In eukaryotic cells, different RNA species are exported from the nucleus via specialized pathways. The mRNA export machinery is highly integrated with mRNA processing, and includes a different set of nuclear transport adaptors as well as other mRNA binding proteins, RNA helicases, and NPC-associated proteins. The protozoan parasite Trypanosoma cruzi is the causative agent of Chagas disease, a widespread and neglected human disease which is endemic to Latin America. Gene expression in Trypanosoma has unique characteristics, such as constitutive polycistronic transcription of protein-encoding genes and mRNA processing by trans-splicing. In general, post-transcriptional events are the major points for regulation of gene expression in these parasites. However, the export pathway of mRNA from the nucleus is poorly understood. The present study investigated the function of TcSub2, which is a highly conserved protein ortholog to Sub2/ UAP56, a component of the Transcription/Export (TREX) multiprotein complex connecting transcription with mRNA export in yeast/human. Similar to its orthologs, TcSub2 is a nuclear protein, localized in dispersed foci all over the nuclei -except the fibrillar center of nucleolus- and at the interface between dense and non-dense chromatin areas, proposing the association of TcSub2 with transcription/processing sites. These findings were analyzed further by BrUTP incorporation assays and confirmed that TcSub2 is physically associated with active RNA polymerase II (RNA pol II), but not RNA polymerase I (RNA pol I) or Spliced Leader (SL) transcription, demonstrating participation particularly in nuclear mRNA metabolism in T. cruzi. The double knockout of the TcSub2 gene is lethal in T. cruzi, suggesting it has an essential function. Alternatively, RNA interference assays were performed in Trypanosoma brucei. It allowed demonstrating that besides being an essential protein, its knockdown causes mRNA accumulation in the nucleus and decrease of translation levels, reinforcing that Trypanosoma-Sub2 (Tryp-Sub2) is a component of mRNA transcription/export pathway in trypanosomes.
PLoS ONE 06/2011; 6(6):e20730. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The nuclear lamina is a structure that lines the inner nuclear membrane. In metazoans, lamins are the primary structural components of the nuclear lamina and are involved in several processes. Eukaryotes that lack lamins have distinct proteins with homologous functions. Some years ago, a coiled-coil protein in Trypanosoma brucei, NUP-1, was identified as the major filamentous component of its nuclear lamina. However, its precise role has not been determined. We characterized a homologous protein in Trypanosoma cruzi, TcNUP-1, and identified its in vivo DNA binding sites using a chromatin immunoprecipitation assay. We demonstrate for the first time that TcNUP-1 associates with chromosomal regions containing large non-tandem arrays of genes encoding surface proteins. We therefore suggest that TcNUP-1 is a structural protein that plays an essential role in nuclear organization by anchoring T. cruzi chromosomes to the nuclear envelope.
[Show abstract][Hide abstract] ABSTRACT: Two species of the genus Trypanosoma infective to humans have been extensively studied at a cell and molecular level, but study of the third, Trypanosoma rangeli, remains in relative infancy. T. rangeli is non-pathogenic, but is frequently mistaken for the related Chagas disease agent Trypanosoma cruzi with which it shares vectors, hosts, significant antigenicity and a sympatric distribution over a wide geographical area. In this study, we present the T. rangeli gene expression profile as determined by the generation of ESTs (Expressed Sequence Tags) and ORESTES (Open Reading Frame ESTs). A total of 4208 unique high quality sequences were analyzed, composed from epimastigote and trypomastigote forms of SC-58 and Choachí strains, representing the two major phylogenetic lineages of this species. Comparative analyses with T. cruzi and other parasitic kinetoplastid species allowed the assignment of putative biological functions to most of the sequences generated and the establishment of an annotated T. rangeli gene expression database. Even though T. rangeli is apathogenic to mammals, genes associated with virulence in other pathogenic kinetoplastids were found. Transposable elements and genes associated mitochondrial gene expression, specifically RNA editing components, are also described for the first time. Our studies confirm the close phylogenetic relationship between T. cruzi and T. rangeli and enable us to make an estimate for the size of the T. rangeli genome repertoire ( approximately 8500 genes).
Molecular and Biochemical Parasitology 11/2010; 174(1):18-25. · 2.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The sequencing of the complete genome of Anaplasma marginale has enabled the identification of several genes that encode membrane proteins, thereby increasing the chances of identifying candidate immunogens. Little is known regarding the genetic variability of genes that encode membrane proteins in A. marginale isolates. The aim of the present study was to determine the degree of conservation of the predicted amino acid sequences of OMP1, OMP4, OMP5, OMP7, OMP8, OMP10, OMP14, OMP15, SODb, OPAG1, OPAG3, VirB3, VirB9-1, PepA, EF-Tu and AM854 proteins in a Brazilian isolate of A. marginale compared to other isolates. Hence, primers were used to amplify these genes: omp1, omp4, omp5, omp7, omp8, omp10, omp14, omp15, sodb, opag1, opag3, virb3, VirB9-1, pepA, ef-tu and am854. After polimerase chain reaction amplification, the products were cloned and sequenced using the Sanger method and the predicted amino acid sequence were multi-aligned using the CLUSTALW and MEGA 4 programs, comparing the predicted sequences between the Brazilian, Saint Maries, Florida and A. marginale centrale isolates. With the exception of outer membrane protein (OMP) 7, all proteins exhibited 92-100% homology to the other A. marginale isolates. However, only OMP1, OMP5, EF-Tu, VirB3, SODb and VirB9-1 were selected as potential immunogens capable of promoting cross-protection between isolates due to the high degree of homology (over 72%) also found with A. (centrale) marginale.
Memórias do Instituto Oswaldo Cruz 11/2010; 105(7):843-9. · 1.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The three trypanosomatids pathogenic to men, Trypanosoma cruzi, Trypanosoma brucei and Leishmania major, are etiological agents of Chagas disease, African sleeping sickness and cutaneous leishmaniasis, respectively. The complete sequencing of these trypanosomatid genomes represented a breakthrough in the understanding of these organisms. Genome sequencing is a step towards solving the parasite biology puzzle, as there are a high percentage of genes encoding proteins without functional annotation. Also, technical limitations in protein expression in heterologous systems reinforce the evident need for the development of a high-throughput reverse genetics platform. Ideally, such platform would lead to efficient cloning and compatibility with various approaches. Thus, we aimed to construct a highly efficient cloning platform compatible with plasmid vectors that are suitable for various approaches.
We constructed a platform with a flexible structure allowing the exchange of various elements, such as promoters, fusion tags, intergenic regions or resistance markers. This platform is based on Gateway® technology, to ensure a fast and efficient cloning system. We obtained plasmid vectors carrying genes for fluorescent proteins (green, cyan or yellow), and sequences for the c-myc epitope, and tandem affinity purification or polyhistidine tags. The vectors were verified by successful subcellular localization of two previously characterized proteins (TcRab7 and PAR 2) and a putative centrin. For the tandem affinity purification tag, the purification of two protein complexes (ribosome and proteasome) was performed.
We constructed plasmids with an efficient cloning system and suitable for use across various applications, such as protein localization and co-localization, protein partner identification and protein expression. This platform also allows vector customization, as the vectors were constructed to enable easy exchange of its elements. The development of this high-throughput platform is a step closer towards large-scale trypanosome applications and initiatives.
[Show abstract][Hide abstract] ABSTRACT: Aotus and Saimiri are non-human primate models recommended by the World Health Organization for experimental studies in malaria, especially for vaccine pre-clinical trials. However, research using these primates is hindered by the lack of specific reagents to evaluate immune responses to infection or vaccination. As a step toward developing molecular tools for cytokine expression studies in these species, primer pairs for 18 cytokine gene fragments were designed based on human DNA sequences and used to amplify the corresponding genes in Aotus infulatus and Saimiri sciureus genomic DNA samples. IFNγ, TNFα, LTA, IL2, IL3, IL4, IL5, IL6, IL10, IL12, IL13, CSF2 and TGFβ2 gene fragments were amplified and sequenced. Primer pairs for IL8, IL17, IL18, IL27 and MIF failed to generate amplification products. When compared to the available corresponding human and non-human primate sequences, most--except IL3 and IL4--showed identity degrees above 90%. Small variations in sequence can help to explain the failure to amplify certain genes or the amplification only at lower annealing temperatures as compared to human DNA samples for several primer pairs. The sequences made available provide the basis for designing molecular tools such as primers for real time PCR specific for A. infulatus and/or S. sciureus. The nucleotide sequences reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned accession numbers DQ985386 to DQ985389, DQ989356 to DQ989369, FJ89020 to FJ89024, and FJ89029.
[Show abstract][Hide abstract] ABSTRACT: Kinetoplast DNA (kDNA) of trypanosomatid protozoa consists of an unusual arrangement of two types of circular molecules catenated into a single network: (1) a few maxicircles that encode various mitochondrial enzyme subunits and rRNA in a cryptic pattern and (2) thousands of minicircles that encode guide RNAs (gRNAs). kDNA is associated with proteins, known as kinetoplast-associated proteins (KAPs), which condense the kDNA network. However, little is known about the KAPs of Trypanosoma cruzi, a parasite that displays different kDNA condensation patterns during its complex morphogenetic development. We cloned the T. cruzi gene encoding TcKAP3 (kinetoplast-associated protein 3). TcKAP3 is a single-copy gene that is transcribed into a 1.8-kb mRNA molecule and expressed in all stages of the parasite. Mouse antiserum raised against recombinant TcKPA3 recognized a 21.8kDa protein, which was found, by indirect immunofluorescence and immunoelectron microscopy, to be associated with the T. cruzi kinetoplast. Several features of TcKAP3, such as its small size, basic nature and similarity with KAP3 from the insect trypanosomatid Crithidia fasciculata, are consistent with a role in DNA charge neutralization and condensation. This suggests that this protein is involved in organizing the kDNA network. Gene deletion was used to investigate TcKAP3 function. Here we investigated the T. cruzi KAP3 null mutant, analyzing its fitness during proliferation, differentiation and infectivity.
Molecular and Biochemical Parasitology 04/2010; 172(2):90-8. · 2.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Brucella spp. são bactérias gram-negativas, intracelulares facultativas que são patogênicas para muitas espécies de mamíferos causando a brucelose, uma zoonose difundida mundialmente. Por isso a busca de alternativas de controle mais eficientes se faz necessário como o desenvolvimento de novas cepas que possam ser testadas como potenciais imunógenos. Neste estudo realizou-se a deleção do gene virB10 da cepa S2308 de Brucella abortus gerando uma cepa knockout provavelmente incapaz de produzir a proteína nativa correspondente. O gene virB10 faz parte de um operon que codifica para um sistema de secreção do tipo IV, essencial para a sobrevivência intracelular e multiplicação da bactéria em células hospedeiras. A deleção foi realizada pela construção do plasmídeo suicida pBlue:virB10:kan e eletroporação deste em células eletrocompetentes de B. abortus S2308, ocorrendo a troca do gene selvagem pelo gene interrompido, com o gene de resistência a canamicina, por recombinação homóloga dupla. Camundongos BALB/c foram inoculados com as cepas S19, RB-51, ΔvirB10 de B. abortus e B. abortus S2308 selvagem; os resultados demonstraram que camundongos BALB/c inoculados com S19 e camundongos BALB/c inoculados com S2308 apresentaram queda mais rápida de linha de tendência, quando comparadas aos demais grupos, para recuperação bacteriana (RB) e peso esplênico (PE) respectivamente. Os grupos que receberam ΔvirB10 S2308 de B. abortus e RB-51 demonstraram comportamento semelhante para ambas as características. Na sexta semana após a inoculação, os resultados para RB (log de UFC ± desvio padrão) e PE (peso esplênico ± desvio padrão), respectivamente, mostraram: grupos inoculados com as cepas S2308 (4,44±1,97 e 0,44±0,11), S19 (1,83±2,54 e 0,31±0,04), RB-51 (0,00±0,00 e 0,20±0,01) e ΔvirB10 S2308 (1,43±1,25 e 0,19±0,03). Considerado o clearance bacteriano, todos os grupos diferiram estatisticamente do grupo que recebeu S2308 (p<0,0001), o grupo inoculado com ΔvirB10 S2308 de B. abortus foi semelhante ao grupo S19 (p=0,4302) e diferente do grupo RB-51 (p=0,0063). A avaliação da persistência revelou que o gene virB10 é essencial para a manutenção da virulência da bactéria. Os resultados obtidos possibilitarão que outras pesquisas sejam realizadas avaliando o potencial imunogênico desta cepa mutante.
[Show abstract][Hide abstract] ABSTRACT: The kinetoplast DNA (kDNA) of trypanosomatids consists of an unusual arrangement of circular molecules catenated into a single network. The diameter of the isolated kDNA network is similar to that of the entire cell. However, within the kinetoplast matrix, the kDNA is highly condensed. Studies in Crithidia fasciculata showed that kinetoplast-associated proteins (KAPs) are capable of condensing the kDNA network. However, little is known about the KAPs of Trypanosoma cruzi, a parasitic protozoon that shows distinct patterns of kDNA condensation during their complex morphogenetic development. In epimastigotes and amastigotes (replicating forms) the kDNA fibers are tightly packed into a disk-shaped kinetoplast, whereas trypomastigotes (non-replicating) present a more relaxed kDNA organization contained within a rounded structure. It is still unclear how the compact kinetoplast disk of epimastigotes is converted into a globular structure in the infective trypomastigotes.
In this work, we have analyzed KAP coding genes in trypanosomatid genomes and cloned and expressed two kinetoplast-associated proteins in T. cruzi: TcKAP4 and TcKAP6. Such small basic proteins are expressed in all developmental stages of the parasite, although present a differential distribution within the kinetoplasts of epimastigote, amastigote and trypomastigote forms.
Several features of TcKAPs, such as their small size, basic nature and similarity with KAPs of C. fasciculata, are consistent with a role in DNA charge neutralization and condensation. Additionally, the differential distribution of KAPs in the kinetoplasts of distinct developmental stages of the parasite, indicate that the kDNA rearrangement that takes place during the T. cruzi differentiation process is accompanied by TcKAPs redistribution.
[Show abstract][Hide abstract] ABSTRACT: We characterized a gene encoding an YchF-related protein, TcYchF, potentially associated with the protein translation machinery of Trypanosoma cruzi. YchF belongs to the translation factor-related (TRAFAC) class of P-loop NTPases. The coding region of the gene is 1185bp long and encodes a 44.3kDa protein. BlastX searches showed TcYchF to be very similar (45-86%) to putative GTP-binding proteins from eukaryotes, including some species of trypanosomatids (Leishmania major and Trypanosoma brucei). A lower but significant level of similarity (38-43%) was also found between the predicted sequences of TcYchF and bacterial YyaF/YchF GTPases of the Spo0B-associated GTP-binding protein (Obg) family. Some of the most important features of the G domain of this family of GTPases are conserved in TcYchF. However, we found that TcYchF preferentially hydrolyzed ATP rather than GTP. The function of YyaF/YchF is unknown, but other members of the Obg family are known to be associated with ribosomal subunits. Immunoblots of the polysome fraction from sucrose gradients showed that TcYchF was associated with ribosomal subunits and polysomes. Immunoprecipitation assays showed that TcYchF was also associated with the proteasome of T. cruzi. Furthermore, inactivation of the T. brucei homolog of TcYchF by RNA interference inhibited the growth of procyclic forms of the parasite. These data suggest that this protein plays an important role in the translation machinery of trypanosomes.
International journal for parasitology 08/2008; 39(1):49-58. · 3.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Trypanosoma cruzi expresses several proteins containing antigenic amino acid repeats. Here we characterized TcRpL7a and TcRBP28, which carry similar repeat motifs and share homology to the eukaryotic L7a ribosomal protein and to a Trypanosoma brucei RNA binding protein, respectively. Analyses of the full length and truncated recombinant TcRpL7a showed that the humoral response of patients with Chagas disease is directed towards its repetitive domain. Sequence analyses of distinct copies of TcRpL7a genes present in the genome of six T. cruzi strains indicate that the number of repeats is higher in proteins from T. cruzi II than T. cruzi I strains. A serum panel of 59 T. cruzi infected patients showed that 73% reacted with TcRpL7a, 71% reacted with TcRBP28 and 80% reacted with 1:1 mixture of both antigens. Synthetic peptides harboring the TcRpL7a repeat motif reacted with 46% of the serum samples. Antibodies raised against both antigens identified equivalent amounts of the native proteins in all three stages of the parasite life cycle. Analyses of subcellular fractions indicated that TcRBP28 is present in the cytoplasm whereas TcRpL7a co-fractionates with polysomes. Confirming their predicted cellular localization, GFP fusions showed that, whereas GFP::TcRBP28 localizes in the cytoplasm, GFP::TcRpL7a accumulates in the nucleus, where ribosome biogenesis occurs.
Microbes and Infection 07/2008; 10(7):716-25. · 2.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Anaplasma marginale is an important vector-borne rickettsia of ruminants in tropical and subtropical regions of the world. Immunization with purified outer membranes of this organism induces protection against acute anaplasmosis. Previous studies, with proteomic and genomic approach identified 21 proteins within the outer membrane immunogen in addition to previously characterized major surface protein1a-5 (MSP1a-5). Among the newly described proteins were VirB9, VirB10, and elongation factor-Tu (EF-Tu). VirB9, VirB10 are considered part of the type IV secretion system (TFSS), which mediates secretion or cell-to-cell transfer of macromolecules, proteins, or DNA-protein complexes in Gram-negative bacteria. EF-Tu can be located in the bacterial surface, mediating bacterial attachment to host cells, or in the bacterial cytoplasm for protein synthesis. However, the roles of VirB9, VirB10, and TFSS in A. marginale have not been defined. VirB9, VirB10, and EF-Tu have not been explored as vaccine antigens. In this study, we demonstrate that sera of cattle infected with A. marginale, with homologous or heterologous isolates recognize recombinant VirB9, VirB10, and EF-Tu. IgG2 from naturally infected cattle also reacts with these proteins. Recognition of epitopes by total IgG and by IgG2 from infected cattle with A. marginale support the inclusion of these proteins in recombinant vaccines against this rickettsia.
Memórias do Instituto Oswaldo Cruz 04/2008; 103(2):186-90. · 1.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We used differential display to select genes differentially expressed during differentiation of epimastigotes into metacyclic trypomastigotes in the protozoan parasite Trypanosoma cruzi. One of the selected clones had a sequence similar to that of the small-subunit (SSU) processome protein Sof1p, which is involved in rRNA processing. The corresponding T. cruzi protein, TcSof1, displayed a nuclear localization and is downregulated during metacyclogenesis. Heterologous RNA interference assays showed that depletion of this protein impaired growth but did not affect progression through the cell cycle, suggesting that ribosome synthesis regulation and the cell cycle are uncoupled in this parasite. Quantitative PCR (qPCR) assays of several SSU processome-specific genes in T. cruzi also showed that most of them were regulated posttranscriptionally. This process involves the accumulation of mRNA in the polysome fraction of metacyclic trypomastigotes, where TcSof1 cannot be detected. Metacyclic trypomastigote polysomes were purified and separated by sucrose gradient sedimentation. Northern blot analysis of the sucrose gradient fractions showed the association of TcSof1 mRNA with polysomes, confirming the qPCR data. The results suggest that the mechanism of regulation involves the blocking of translation elongation and/or termination.