Cloning, characterization and DNA immunization of an Onchocerca volvulus glyceraldehyde-3-phosphate dehydrogenase (Ov-GAPDH)

Identification of protein biomarkers of attenuation and immunogenicity of centrin or p27 gene deleted live vaccine candidates of Leishmania against visceral leishmaniasis

Currently, no licensed vaccine is available for human visceral leishmaniasis (VL), a fatal disease caused by the protozoan parasite Leishmania donovani. Two of our live attenuated L. donovani vaccine candidates, either deleted for Centrin1 (LdCen1^-/-) or p27 gene (Ldp27^-/-), that display reduced growth in macrophages were studied to be safe, immunogenic and protective against VL in various animal models. This report involves the identification of differentially expressed proteins, their related pathways and its underlying mechanism in the intracellular stage of these parasites, using Isobaric Tags for Relative and Absolute Quantitation (iTRAQ) methods. Out of 50-60 proteins, found to be differentially expressed in these mutant parasites, 36 were found to be common in both the parasites. Such proteins mainly belong to the functional categories viz. metabolic enzymes, chaperones and stress proteins, proteins involved in translation, processing and transport and proteins involved in nucleic acid processing. Proteins known to be host protective, like Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), cytochrome c, calreticulin and those responsible for inducing immune response, namely tubulins, DEAD box RNA helicases, HSP70 and tryparedoxin, have been detected to be modulated in these parasites. Such proteins could be predicted as biomarkers, with further scope of study for their role in growth attenuation. SIGNIFICANCE: This study aims at predicting proteomic biomarkers of Leishmania parasite growth attenuation, that have immunomodulatory role in the disease leishmaniasis. Advanced studies could be helpful in establishing the role of these identified proteins in parasitic virulence and to predict the host interaction at molecular level. Also, these proteins could be exploited as attenuation markers during the development of genetically modified live attenuated parasites as vaccine candidates. These could be cross validated in varied species of Leishmania and other tyrpanosomatids for similar response towards identifying them as universal biomarkers of attenuation.

Schistosoma mansoni glyceraldehyde-3-phosphate dehydrogenase enhances formation of the blood-clot lysis protein plasmin

Schistosomes are intravascular blood flukes that cause the parasitic disease schistosomiasis. In agreement with Schistosoma mansoni (Sm) proteomic analysis, we show here that the normally intracellular glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is also found at the parasite surface; live worms from all intravascular life stages display GAPDH activity. Suppressing GAPDH gene expression using RNA interference significantly lowers this live worm surface activity. Medium in which the worms are cultured overnight displays essentially no activity, showing that the enzyme is not shed or excreted but remains associated with the worm surface. Immunolocalization experiments confirm that the enzyme is highly expressed in the parasite tegument (skin). Surface activity in schistosomula amounts to ∼8% of that displayed by equivalent parasite lysates. To address the functional role of SmGAPDH, we purified the protein following its expression in Escherichiacoli strain DS113. The recombinant protein displays optimal enzymatic activity at pH 9.2, shows robust activity at the temperature of the parasite's hosts, and has a Michaelis-Menten constant for glyceraldehyde-3-phosphate (GAP) of 1.4 mM±0.24. We show that recombinant SmGAPDH binds plasminogen (PLMG) and promotes PLMG conversion to its active form (plasmin) in a dose response in the presence of tissue plasminogen activator. Since plasmin is a key mediator of thrombolysis, our results support the hypothesis that SmGAPDH, a host-interactive tegumental protein that can enhance PLMG activation, could help degrade blood clots around the worms in the vascular microenvironment and thus promote parasite survival in vivoThis article has an associated First Person interview with the first author of the paper.

Cloning and Expression Profile of Glyceraldehyde-3-Phosphate Dehydrogenase in Haemaphysalis flava (Acari: Ixodidae)

Haemaphysalis flava (Acari: Ixodidae) harbors pathogenic microorganisms and transfers these to hosts during blood feeding. Proteomic analysis in the midgut contents of H. flava detected glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and contig 1683 was retrieved as a GAPDH gene fragment by searching our previous transcriptomic library. In the study, the 5' and 3' ends of contig 1683 were cloned by rapid amplification of cDNA ends (RACE) and a full length, 1340 bp cDNA of Hf-GAPDH was obtained. The open-reading frame had 999 bp and coded for 333 amino acids. Hf-GAPDH was predicted to have an N-terminal NAD binding domain and a C-terminal glyceraldehyde dehydrogenase catalytic domain. The molecular structure of Hf-GAPDH was analyzed and the evolutionary relationship also established. The GAPDH protein sequence was conserved among ticks. The expression pattern of Hf-GAPDH, analyzed by real-time PCR, significantly differed among life phases, feeding stages, and tissues. As the ticks grew, the expression level of Hf-GAPDH was up-regulated. The expression levels of Hf-GAPDH in salivary glands and midguts from half-engorged ticks were lower than the same tissues from engorged ticks. This study will provide reference data for the follow-up verification of the GAPDH-related function and the feasibility as a potential anti-tick vaccine.

Plasminogen-binding proteins as an evasion mechanism of the host's innate immunity in infectious diseases

Pathogens have developed particular strategies to infect and invade their hosts. Amongst these strategies’ figures the modulation of several components of the innate immune system participating in early host defenses, such as the coagulation and complement cascades, as well as the fibrinolytic system. The components of the coagulation cascade and the fibrinolytic system have been proposed to be interfered during host invasion and tissue migration of bacteria, fungi, protozoa, and more recently, helminths. One of the components that has been proposed to facilitate pathogen migration is plasminogen (Plg), a protein found in the host’s plasma, which is activated into plasmin (Plm), a serine protease that degrades fibrin networks and promotes degradation of extracellular matrix (ECM), aiding maintenance of homeostasis. However, pathogens possess Plg-binding proteins that can activate it, therefore taking advantage of the fibrin degradation to facilitate establishment in their hosts. Emergence of Plg-binding proteins appears to have occurred in diverse infectious agents along evolutionary history of host–pathogen relationships. The goal of the present review is to list, summarize, and analyze different examples of Plg-binding proteins used by infectious agents to invade and establish in their hosts. Emphasis was placed on mechanisms used by helminth parasites, particularly taeniid cestodes, where enolase has been identified as a major Plg-binding and activating protein. A new picture is starting to arise about how this glycolytic enzyme could acquire an entirely new role as modulator of the innate immune system in the context of the host–parasite relationship.

Proteomic profiling of the midgut contents of Haemaphysalis flava

Scant information is available regarding the proteins involved in blood meal processing in ticks. Here, we aimed to highlight the midgut proteins involved in preventing blood meal coagulation, and in facilitating intracellular digestion in the tick Haemaphysalis flava. Proteins were extracted from the midgut contents of fully engorged and partially engorged ticks. We used liquid chromatography tandem-mass spectrometry (LC-MS/MS) analysis to identify 131 unique peptides, and 102 proteins. Of these, 15 proteins, each with at least two unique peptides, were recognized with high confidence. We also retrieved 18 unigenes from our previous published transcriptomic libraries of the midguts and salivary glands of H. flava, and inferred the primary structures of nine proteins and fragments of five proteins. There were 23 and 21 unique proteins in the midgut contents of fully engorged and partially engorged ticks, respectively. We detected 58 shared proteins in the midgut contents of both fully engorged and partially engorged ticks. Of these, seven were significantly differentially expressed between fully engorged and partially engorged ticks: actin, calmodulin, elongation factor-1α, hsp90, multifunctional chaperone, tubulin α, and tubulin β. Our results demonstrated that the proteome of the midgut contents, combined with the transcriptome of the midgut, was a viable method for the reinforcement of protein identification. This method will facilitate further study of blood meal processing by ticks, as well as the identification of clues for tick infestation control. The existence of numerous proteins detected in the midgut contents also highlight the complexity of blood digestion in ticks; this area is in need of further investigation.

Onchocerca volvulus: The Road from Basic Biology to a Vaccine

Human onchocerciasis - commonly known as river blindness - is one of the most devastating yet neglected tropical diseases, leaving many millions in sub-Saharan Africa blind and/or with chronic disabilities. Attempts to eliminate onchocerciasis, primarily through the mass drug administration of ivermectin, remains challenging and has been heightened by the recent news that drug-resistant parasites are developing in some populations after years of drug treatment. Needed, and needed now, in the fight to eliminate onchocerciasis are new tools, such as preventive and therapeutic vaccines. This review summarizes the progress made to advance the onchocerciasis vaccine from the research laboratory into the clinic.

Molecular and biochemical characterisation and recognition by the immune host of the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) of the abomasal nematode parasite Teladorsagia circumcincta

A 1023 bp full length cDNA encoding Teladorsagia circumcincta GAPDH (TeciGAPDH) was cloned, expressed in Escherichia coli and the recombinant protein purified and its kinetic properties determined. A phylogenetic tree was constructed using helminth GAPDH sequences. The predicted protein consisted of 341 amino acids and was present as a single band of about 38 kDa on SDS-PAGE. Multiple alignments of the protein sequence of TeciGAPDH with homologues from other helminths showed that the greatest similarity (93%) to the GAPDH of Haemonchus contortus and Dictyocaulus viviparus, 82-86% similarity to the other nematode sequences and 68-71% similarity to cestode and trematode enzymes. Substrate binding sites and conserved regions were identified and were completely conserved in other homologues. At 25 °C, the optimum pH for TeciGAPDH activity was pH 8, the V_max was 1052 ± 23 nmol min^-1 mg^-1 protein and the apparent K_m for the substrate glyceraldehyde-3-phosphate was 0.02 ± 0.01 mM (both mean ± SD, n = 2). Antibodies in both serum and saliva from field-immune, but not nematode-naïve, sheep recognised recombinant TeciGAPDH in enzyme-linked immunosorbent assays. The recognition of the recombinant protein by antibodies generated by exposure of sheep to native GAPDH indicates similar antigenicity of the two proteins.

Plasmin in Parasitic Chronic Infections: Friend or Foe?

Plasmin is the final product of the fibrinolytic system, the physiological mechanism responsible for dissolving fibrin clots. Its broad-range proteolytic activity implies that interaction with fibrinolysis and recruitment of plasmin by blood and tissue parasites is an important mechanism that mediates the invasion and establishment of this kind of pathogen in the hosts. However, recent studies have linked an excess of plasmin generated by this interaction with serious pathological events at the vascular level, including the proliferation and migration of arterial wall cells, inflammation, and degradation of the extracellular matrix. Therefore, we present data that support the need to reconsider the role of plasmin, as well as its benefits or drawbacks, in the context of host-parasite relations.

Glyceradehyde-3-phosphate dehydrogenase as a suitable vaccine candidate for protection against bacterial and parasitic diseases

The enzyme glyceraldehyde-3-P-dehydrogenase (GAPDH) has been identified as having other properties in addition to its key role in glycolysis. The ability of GAPDH to bind to numerous extracellular matrices, modulation of host-immune responses, a role in virulence and surface location has prompted numerous investigators to postulate that GAPDH may be a good vaccine candidate for protection against numerous pathogens. Although immune responses against GAPDH have been described for many microorganisms, vaccines containing GAPDH have been successfully tested in few cases including those against the trematode-Schistosoma mansoni, the helminth-Enchinococcus multilocularis; the nematode filaria- Litomosoides sigmodontis; fish pathogens such as Aeromonas spp., Vibrio spp., Edwarsiella spp., and Streptococcus iniae; and environmental streptococci, namely, Streptococcus uberis and Streptococcus dysgalactiae. Before GAPDH-based vaccines are considered viable options for protection against numerous pathogens, we need to take into account the homology between the host and pathogen GAPDH proteins to prevent potential autoimmune reactions, thus protective GAPDH epitopes unique to the pathogen protein must be identified.

DNA vaccine encoding the moonlighting protein Onchocerca volvulus glyceraldehyde-3-phosphate dehydrogenase (Ov-GAPDH) leads to partial protection in a mouse model of human filariasis

River blindness, caused by the filarial parasite Onchocerca volvulus, is a major socio-economic and public health problem in Sub-Saharan Africa. In January 2015, The Onchocerciasis Vaccine for Africa (TOVA) Initiative has been launched with the aim of providing new tools to complement mass drug administration (MDA) of ivermectin, thereby promoting elimination of onchocerciasis in Africa. In this context we here present Onchocerca volvulus glyceraldehyde-3-phosphate dehydrogenase (Ov-GAPDH) as a possible DNA vaccine candidate. We report that in a laboratory model for filariasis, immunization with Ov-GAPDH led to a significant reduction of adult worm load and microfilaraemia in BALB/c mice after challenge infection with the filarial parasite Litomosoides sigmodontis. Mice were either vaccinated with Ov-GAPDH.DNA plasmid (Ov-pGAPDH.DNA) alone or in combination with recombinantly expressed Ov-GAPDH protein (Ov-rGAPDH). During the following challenge infection of immunized and control mice with L. sigmodontis, those formulations which included the DNA plasmid, led to a significant reduction of adult worm loads (up to 57% median reduction) and microfilaraemia (up to 94% reduction) in immunized animals. In a further experiment, immunization with a mixture of four overlapping, synthetic Ov-GAPDH peptides (Ov-GAPDHpept), with alum as adjuvant, did not significantly reduce worm loads. Our results indicate that DNA vaccination with Ov-GAPDH has protective potential against filarial challenge infection in the mouse model. This suggests a transfer of the approach into the cattle Onchocerca ochengi model, where it is possible to investigate the effects of this vaccination in the context of a natural host-parasite relationship.

Surface-displayed glyceraldehyde 3-phosphate dehydrogenase and galectin from Dirofilaria immitis enhance the activation of the fibrinolytic system of the host

Cardiopulmonary dirofilariosis is a cosmopolitan disease caused by Dirofilaria immitis, a filaroid parasite whose adult worms live for years in the vascular system of its host. Previous studies have shown that D. immitis can use their excretory/secretory (ES) and surface antigens to enhance fibrinolysis, which could limit the formation of clots in its surrounding environment. Moreover, several isoforms of the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and galectin (GAL) were identified in both antigenic extracts as plasminogen-binding proteins. The aim of this work is to study the interaction of the GAPDH and GAL of D. immitis with the fibrinolytic system of the host. This study includes the cloning, sequencing and expression of the recombinant forms of the GAPDH and GAL of D. immitis (rDiGAPDH and rDiGAL) and the analysis of their capacity as plasminogen-binding proteins. The results indicate that rDiGAPDH and rDiGAL are able to bind plasminogen and stimulate plasmin generation by tissue plasminogen activator (tPA). This interaction needs the involvement of lysine residues, many of which are located externally in both proteins as have been shown by the molecular modeling of their secondary structures. In addition, we show that rDiGAPDH and rDiGAL enhance the expression of the urokinase-type plasminogen activator (uPA) on canine endothelial cells in culture and that both proteins are expressed on the surface of D. immitis in close contact with the blood of the host. These data suggest that D. immitis could use the associated surface GAPDH and GAL as physiological plasminogen receptors to shift the fibrinolytic balance towards the generation of plasmin, which might constitute a survival mechanism to avoid the clot formation in its intravascular habitat.

Proteomic analysis of the somatic and surface compartments from Dirofilaria immitis adult worms

Dirofilaria immitis (hearthworm) is a filarial roundworm transmitted by mosquitoes to different vertebrate hosts (dogs, cats and humans, among others), causing dirofilariosis. The adult worms reside in the pulmonary arteries affecting vessels and tissues and resulting in different pathological manifestations. Worms migrate to the heart and surrounding major vessels in heavy infections. Dirofilariosis can result in serious damage to affected hosts. In the last few years, a re-emergence of the disease driven by the climate change has been pointed out. Very recently, the knowledge at molecular level of this parasite has been extended by the published studies on its genome and transcriptome. Nevertheless, studies on the expression of defined protein sets in different parasite compartments and the corresponding role of those proteins in the host-parasite relationship have been relatively scarce to date. These include the description of the adult worm secretome, and some of the proteins eliciting humoural immune responses and those related with plasminogen binding in secreted and surface extracts of the parasite. Here, we investigate by proteomics the somatic and surface compartments of the D. immitis adult worm, adding new information on protein expression and localization that would facilitate a deeper understanding of the host-parasite relationships in dirofilariosis.

Parasitism in optima forma: exploiting the host fibrinolytic system for invasion

The interaction of pathogenic bacteria with the host fibrinolytic system through the plasminogen molecule has been well documented. It has been shown, using animal models, to be important in invasion into the host and establishment of the infection. From a number of recent observations with parasitic protists and helminths, emerges evidence that also in these organisms the interaction with plasminogen may be important for infection and virulence. A group of molecules that act as plasminogen receptors have been identified in parasites. This group comprises the glycolytic enzymes enolase, glyceraldehyde-3-phosphate dehydrogenase and fructose-1,6-biphosphate aldolase, in common with the plasminogen receptors known in prokaryotic pathogens. The interaction with the fibrinolytic system may arm the parasites with the host protease plasmin, thus helping them to migrate and cross barriers, infect cells and avoid clot formation. In this context, plasminogen receptors on the parasite surface or as secreted molecules, may be considered virulence factors. A possible evolutionary scenario for the recruitment of glycolytic enzymes as plasminogen receptors by widely different pathogens is discussed.

Surface associated antigens of Dirofilaria immitis adult worms activate the host fibrinolytic system

Cardiopulmonary dirofilariosis (Dirofilaria immitis) is characterized by apparent contradictory events, like the long-term survival of adult worms in the circulatory system of the infected hosts and the development of life-threatening events like thromboembolisms and others. Thus parasite mechanisms, like the activation of fibrinolytic system, are key to the survival of both the worms and the host. The aim of this study was to investigate the interaction between D. immitis adult worms surface-associated antigens (DiSAA) and the fibrinolytic system of the host. We demonstrate that DiSAA extract is able to bind plasminogen and generate plasmin, with the latter occurring in a tissue plasminogen activator (t-PA) dependent manner. Additionally, 11 plasminogen-binding proteins from DiSAA extract were identified by proteomics and mass spectrometry (MS) (actin-5C, actin-1, enolase, fructose-bisphosphate aldolase, GAPDH, MSP domain protein, MSP 2, beta-galactosidase-binding-lectin, galectin, immunoglobulin I-set domain-containing protein and cyclophilin Ovcyp-2). Because in a previous work we have shown the positive interaction between the excretory/secretory antigens of D. immitis (DiES) and the host fibrinolytic system and many of the molecules identified here are shared by both antigens, we hypothesize that DiSAA cooperate in host fibrinolytic system activation promoting the fibrin clot lysis.

Secreted glyceraldehyde-3-phosphate dehydrogenase as a broad spectrum vaccine candidate against microbial infection in aquaculture

AIMS

Subcellullar localizations and cross-immunities of GAPDHs from six common pathogenic bacteria in aquaculture were investigated.

METHODS AND RESULTS

Subcellullar localizations of GAPDHs of Edwardsiella tarda EIB202, Edwardsiella ictaluri ATCC33202, Aeromonas hydrophila LSA34, Vibrio anguillarum MVM425, Vibrio alginolyticus EPGS020401 and Vibrio harveyi VIB647 were analysed with Western blotting, indirect immunofluorescence and flow cytometry examinations. Immunoprotections of different recombinant GAPDHs against these pathogens were investigated with zebrafish model. Western blotting of subcellular extractions showed that all GAPDHs were secreted into extracellular medium and periplasmic space. In addition, GAPDHs were demonstrated to distribute in the outer membranes except MVM425 and VIB647. And, GAPDHs were confirmed to be present on the surface of these bacteria with indirect immunofluorescence and flow cytometry examinations. The remarkable cross-protective immunities of these recombinant GAPDHs were induced in zebrafish, and the relative protective survivals were almost over 60%.

CONCLUSIONS

Localizations of GAPDHs from these pathogenic bacteria were similar to many other causative agents. And, GAPDHs could be important protective antigens and give remarkable cross-immunity against different pathogens.

SIGNIFICANCE AND IMPACT OF THE STUDY

Recombinant GAPDH could be designed as a broad spectrum vaccine candidate against multiple microbial infections in aquaculture.

Cloning, expression and characterization of NAD+-dependent glyceraldehyde-3-phosphate dehydrogenase of adult Haemonchus contortus†

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) regulates a wide range of biological processes, including pathogen evasion. In the present research, the GAPDH gene of Haemonchus contortus (HcGAPDH) was cloned and characterized. Specific primers for the rapid amplification of cDNA ends (RACE) were designed based on the expressed sequence tag (EST, AW670737) to amplify the 3′ and 5′ ends of HcGAPDH. The full length of cDNA from this gene was obtained by overlapping the sequences of 3′ and 5′ extremities and amplification by reverse transcription polymerase chain reaction (RT-PCR). The biochemical activities of the recombinant protein HcGAPDH, which was expressed in prokaryotic cells and purified by affinity chromatography, were analysed by assays of enzymatic activity, thermal stability and pH. The results showed that the cloned full-length cDNA comprised 1303 bp and encoded a peptide with 341 amino acid residues which showed sequence similarity to several known GAPDHs. The biochemical assay showed that the protein encoded by the HcGAPDH exhibited enzymatic activity with NAD+ as a cofactor. HcGAPDH was stable between pH 5 and 9 and maintained activity at high temperatures of up to 75°C. The natural GAPDH of Haemonchus contortus detected by immunoblot assay was approximately 38 kDa in size, and the recombinant HcGAPDH was recognized strongly by serum from naturally infected goats.

Immunoproteomic analysis of human serological antibody responses to vaccination with whole-cell pertussis vaccine (WCV)

Background

Pertussis (whooping cough) caused by Bordetella pertussis (B.p), continues to be a serious public health threat. Vaccination is the most economical and effective strategy for preventing and controlling pertussis. However, few systematic investigations of actual human immune responses to pertussis vaccines have been performed. Therefore, we utilized a combination of two-dimensional electrophoresis (2-DE), immunoblotting, and mass spectrometry to reveal the entire antigenic proteome of whole-cell pertussis vaccine (WCV) targeted by the human immune system as a first step toward evaluating the repertoire of human humoral immune responses against WCV.

Methodology/Principal Findings

Immunoproteomic profiling of total membrane enriched proteins and extracellular proteins of Chinese WCV strain 58003 identified a total of 30 immunoreactive proteins. Seven are known pertussis antigens including Pertactin, Serum resistance protein, chaperonin GroEL and two OMP porins. Sixteen have been documented to be immunogenic in other pathogens but not in B.p, and the immunogenicity of the last seven proteins was found for the first time. Furthermore, by comparison of the human and murine immunoproteomes of B.p, with the exception of four human immunoreactive proteins that were also reactive with mouse immune sera, a unique group of antigens including more than 20 novel immunoreactive proteins that uniquely reacted with human immune serum was confirmed.

Conclusions/Significance

This study is the first time that the repertoire of human serum antibody responses against WCV was comprehensively investigated, and a small number of previously unidentified antigens of WCV were also found by means of the classic immunoproteomic strategy. Further research on these newly identified predominant antigens of B.p exclusively against humans will not only remarkably accelerate the development of diagnostic biomarkers and subunit vaccines but also provide detailed insight into human immunity mechanisms against WCV. In particular, this work highlights the heterogeneity of the B.p immunoreactivity patterns of the mouse model and the human host.

Control of important helminthic infections vaccine development as part of the solution

Among the tools available for the control of helminth infections, chemotherapy has come to totally dominate the field. In the veterinary field, development of drug resistance has appeared but this is not (yet) a problem in the control of human diseases. Although there is no vaccine commercially available for any human parasitic infection yet, recent progress in vaccine development is making this a future possibility for several diseases. The goal of chemotherapy is to alleviate infection and morbidity in the definitive host, or reduce transmission, while the effect of available vaccine candidates would mainly be to influence transmission through targeting the intermediate or reservoir host, when the infection is zoonotic. Apart from this general scheme, there are also vaccine candidates targeting the parasites in the definitive host, in particular the early developmental stages, which should reduce the risk of drug failure. Since the biological targets in most cases are different, vaccination would be synergistic with drug therapy. This review covers diseases caused by helminthes in both humans and animals and includes examples of diseases caused by cestodes, nematodes and trematodes. The focus is on infections for which vaccine development has been undertaken for a long time, resulting in products that could realistically become integrated into control strategies in the near future.

DNA vaccines: a rational design against parasitic diseases

Parasitic diseases are one of the most devastating causes of morbidity and mortality worldwide. Although immunization against these infections would be an ideal solution, the development of effective vaccines has been hampered by specific challenges posed by parasitic pathogens. Plasmid-based DNA vaccines may prove to be promising immunization tools in this area because vectors can be designed to integrate several antigens from different stages of the parasite life cycle or different subspecies; vaccines, formulations and immunization protocols can be tuned to match the immune response that offers protective immunity; and DNA vaccination is an affordable platform for developing countries. Partial and full protective immunity have been reported following DNA vaccination against the most significant parasitic diseases in the world.

The transcriptomes of the cattle parasitic nematode Ostertagia ostartagi

Ostertagia ostertagi is a gastrointestinal parasitic nematode that affects cattle and leads to a loss of production. In this study, we present the first large-scale genomic survey of O. ostertagi by the analysis of expressed transcripts from three stages of the parasite: third-stage larvae, fourth-stage larvae and adult worms. Using an in silico approach, 2284 genes were identified from over 7000 expressed sequence tags and abundant transcripts were analyzed and characterized by their functional profile. Of the 2284 genes, 66% had similarity to other known or predicted genes while the rest were novel and potentially represent genes specific to the species and/or stages. Furthermore, a subset of the novel proteins were structurally annotated and assigned putative function based on orthologs in Caenorhabditis elegans and corresponding RNA interference phenotypes. Hence, over 70% of the genes were annotated using protein sequences, domains and pathway databases. Differentially expressed transcripts from the two larval stages and their functional profiles were also studied leading to a more detailed understanding of the parasite's life-cycle. The identified transcripts are a valuable resource for genomic studies of O. ostertagi and can facilitate the design of control strategies and vaccine programs.

Proteomic profiling and identification of immunodominant spore antigens of Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis

Differentially expressed and immunogenic spore proteins of the Bacillus cereus group of bacteria, which includes Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis, were identified. Comparative proteomic profiling of their spore proteins distinguished the three species from each other as well as the virulent from the avirulent strains. A total of 458 proteins encoded by 232 open reading frames were identified by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry analysis for all the species. A number of highly expressed proteins, including elongation factor Tu (EF-Tu), elongation factor G, 60-kDa chaperonin, enolase, pyruvate dehydrogenase complex, and others exist as charge variants on two-dimensional gels. These charge variants have similar masses but different isoelectric points. The majority of identified proteins have cellular roles associated with energy production, carbohydrate transport and metabolism, amino acid transport and metabolism, posttranslational modifications, and translation. Novel vaccine candidate proteins were identified using B. anthracis polyclonal antisera from humans postinfected with cutaneous anthrax. Fifteen immunoreactive proteins were identified in B. anthracis spores, whereas 7, 14, and 7 immunoreactive proteins were identified for B. cereus and in the virulent and avirulent strains of B. thuringiensis spores, respectively. Some of the immunodominant antigens include charge variants of EF-Tu, glyceraldehyde-3-phosphate dehydrogenase, dihydrolipoamide acetyltransferase, Delta-1-pyrroline-5-carboxylate dehydrogenase, and a dihydrolipoamide dehydrogenase. Alanine racemase and neutral protease were uniquely immunogenic to B. anthracis. Comparative analysis of the spore immunome will be of significance for further nucleic acid- and immuno-based detection systems as well as next-generation vaccine development.

Identification of proteins in excretory/secretory extracts of Echinostoma friedi (Trematoda) from chronic and acute infections

In the present study, we describe the investigation of Echinostoma friedi excretory/secretory products using a proteomic approach combined with the use of heterologous antibodies. We have identified 18 protein spots corresponding to ten proteins, including cytoskeletal proteins like actin, tropomyosin, and paramyosin; glycolytic enzymes like enolase, glyceraldehyde 3P dehydrogenase, and aldolase; detoxifying enzymes like GSTs; and stress proteins like heat shock protein (Hsp) 70. Among these proteins, both actin and, to a lesser extent, Hsp70, exhibited differential expression patterns between chronic and acute infections in the Echinostoma-rodent model, suggesting that these proteins may play a role in the survival within the host.

Schistosoma bovis: plasminogen binding in adults and the identification of plasminogen-binding proteins from the worm tegument

Schistosoma bovis is a ruminant haematic parasite that lives for years in the mesenteric vessels of the host. The aim of this work was to investigate the ability of adult S. bovis worms to interact with plasminogen, a central component in the host fibrinolytic system. Confocal microscopy analysis revealed that plasminogen bound to the tegument surface of the male-but not female-S. bovis worms and that this binding was strongly dependent on lysine residues. It was also observed that a protein extract of the worm tegument (TG) had the capacity to generate plasmin and to enhance the plasmin generation by the tissue-type plasminogen activator. Proteomic analysis of the TG extract identified 10 plasminogen-binding proteins, among which the major ones were enolase, glyceraldehyde-3-phosphate dehydrogenase and actin. This study represents the first report about the binding of plasminogen to Schistosoma sp. proteins.