A tropomyosin gene is differentially expressed in the larval stage of Echinococcus granulosus

Development of an oral nanovaccine for dogs against Echinococcus granulosus

Dogs are the main source of animal and human cystic echinococcosis caused by the Cestode parasite Echinococcus granulosus. Dog vaccination seems to be a good strategy to control this parasitic disease. Here we present the development of a polymeric nanoparticle-based oral vaccine for dogs against Echinococcus granulosus delivered in enteric-coated capsules. To achieve our target, we encapsulated two recombinant antigens into biodegradable polymeric nanoparticles in the presence of Monophosphoryl lipid A as an adjuvant to ensure efficient delivery and activation of a protective mucosal immune response. The formulated delivery system showed a nanoparticle size less than 200 nm with more than 80 % antigen encapsulation efficiency and conserved integrity and immunogenicity. The nanoparticle surface was coated with chitosan to enhance adhesion to the gut mucosa and a subsequent antigen delivery. Chitosan-coated nanoparticles showed a higher cell internalization in murine macrophages and dendritic cells as well as a higher penetration into Caco-2 cells in vitro. Antigen-loaded nanoparticles were freeze-dried and enteric-coated capsules were filled with the obtained powder. The obtained results show a promising nanoparticles delivery system for oral vaccination.

In vitro evaluations on canine monocyte-derived dendritic cells of a nanoparticles delivery system for vaccine antigen against Echinococcus granulosus

Since dogs play a central role in the contamination of humans and livestock with Echinococcus granulosus, the development of an effective vaccine for dogs is essential to control the disease caused by this parasite. For this purpose, a formulation based on biodegradable polymeric nanoparticles (NPs) as delivery system of recombinant Echinococcus granulosus antigen (tropomyosin EgTrp) adjuved with monophosphoryl lipid A (MPLA) has been developed. The obtained nanoparticles had a size of approximately 200 nm in diameter into which the antigen was correctly preserved and encapsulated. The efficiency of this system to deliver the antigen was evaluated in vitro on canine monocyte-derived dendritic cells (cMoDCs) generated from peripheral blood monocytes. After 48 h of contact between the formulations and cMoDCs, we observed no toxic effect on the cells but a strong internalization of the NPs, probably through different pathways depending on the presence or not of MPLA. An evaluation of cMoDCs activation by flow cytometry showed a stronger expression of CD80, CD86, CD40 and MHCII by cells treated with any of the tested formulations or with LPS (positive control) in comparison to cells treated with PBS (negative control). A higher activation was observed for cells challenged with EgTrp-NPs-MPLA compared to EgTrp alone. Formulations with MPLA, even at low ratio of MPLA, give better results than formulations without MPLA, proving the importance of the adjuvant in the nanoparticles structure. Moreover, autologous T CD4+ cell proliferation observed in presence of cMoDCs challenged with EgTrp-NPs-MPLA was higher than those observed after challenged with EgTrp alone (p<0.05). These first results suggest that our formulation could be used as an antigen delivery system to targeting canine dendritic cells in the course of Echinococcus granulosus vaccine development.

Oral Application of Recombinant Bacillus subtilis Spores to Dogs Results in a Humoral Response against Specific Echinococcus granulosus Paramyosin and Tropomyosin Antigens

Bacillus subtilis is known as an endospore- and biofilm-forming bacterium with probiotic properties. We have recently developed a method for displaying heterologous proteins on the surface of B. subtilis biofilms by introducing the coding sequences of the protein of interest into the bacterial genome to generate a fusion protein linked to the C terminus of the biofilm matrix protein TasA. Although B. subtilis is a regular component of the gut microflora, we constructed a series of recombinant B. subtilis strains that were tested for their ability to be used to immunize dogs following oral application of the spores. Specifically, we tested recombinant spores of B. subtilis carrying either the fluorescent protein mCherry or else selected antigenic peptides (tropomyosin and paramyosin) from Echinococcus granulosus, a zoonotic intestinal tapeworm of dogs and other carnivores. The application of the recombinant B. subtilis spores led to the colonization of the gut with recombinant B. subtilis but did not cause any adverse effect on the health of the animals. As measured by enzyme-linked immunosorbent assay and immunoblotting, the dogs were able to develop a humoral immune response against mCherry as well as against E. granulosus antigenic peptides. Interestingly, the sera of dogs obtained after immunization with recombinant spores of E. granulosus peptides were able to recognize E. granulosus protoscoleces, which represent the infective form of the head of the tapeworms. These results represent an essential step toward the establishment of B. subtilis as an enteric vaccine agent.

Hydatid disease: vaccinology and development of the EG95 recombinant vaccine

Hydatid disease is a zoonotic parasitic disease that is distributed widely around the world and causes substantial human morbidity and mortality, particularly in developing countries. Reduction of human hydatid disease using anthelmintics, together with changes in human lifestyle and animal management practices, have been unsuccessful in some developing countries where the disease still persists. Substantial progress has been made towards developing a practical, recombinant vaccine in sheep, to interrupt the lifecycle of Echinococcus granulosus and to prevent subsequent transmission from dogs to humans. This review focuses on the scientific advances in the development of a recombinant vaccine for hydatid disease and the remaining challenges facing the widespread use of the vaccine for control of hydatid disease in endemic areas.

Host-parasite relationship in cystic echinococcosis: an evolving story

The larval stage of Echinococcus granulosus causes cystic echinococcosis, a neglected infectious disease that constitutes a major public health problem in developing countries. Despite being under constant barrage by the immune system, E. granulosus modulates antiparasite immune responses and persists in the human hosts with detectable humoral and cellular responses against the parasite. In vitro and in vivo immunological approaches, together with molecular biology and immunoproteomic technologies, provided us exciting insights into the mechanisms involved in the initiation of E. granulosus infection and the consequent induction and regulation of the immune response. Although the last decade has clarified many aspects of host-parasite relationship in human cystic echinococcosis, establishing the full mechanisms that cause the disease requires more studies. Here, we review some of the recent developments and discuss new avenues in this evolving story of E. granulosus infection in man.

Developmental expression of high molecular weight tropomyosin isoforms in Mesocestoides corti

Tropomyosins are a family of actin-binding proteins with diverse roles in actin filament function. One of the best characterized roles is the regulation of muscle contraction. Tropomyosin isoforms can be generated from different genes, and from alternative promoters and alternative splicing from the same gene. In this work, we have isolated sequences for tropomyosin isoforms from the cestode Mesocestoides corti, and searched for tropomyosin genes and isoforms in other flatworms. Two genes are conserved in the cestodes M. corti and Echinococcus multilocularis, and in the trematode Schistosoma mansoni. Both genes have the same structure, and each gene gives rise to at least two different isoforms, a high molecular weight (HMW) and a low molecular weight (LMW) one. Because most exons are duplicated and spliced in a mutually exclusive fashion, isoforms from one gene only share one exon and are highly divergent. The gene duplication preceded the divergence of neodermatans and the planarian Schmidtea mediterranea. Further duplications occurred in Schmidtea, coupled to the selective loss of duplicated exons, resulting in genes that only code for HMW or LMW isoforms. A polyclonal antibody raised against a HMW tropomyosin from Echinococcus granulosus was demonstrated to specifically recognize HMW tropomyosin isoforms of M. corti, and used to study their expression during segmentation. HMW tropomyosins are expressed in muscle layers, with very low or absent levels in other tissues. No expression of HMW tropomyosins is present in early or late genital primordia, and expression only begins once muscle fibers develop in the genital ducts. Therefore, HMW tropomyosins are markers for the development of muscles during the final differentiation of genital primordia.

An oral recombinant vaccine in dogs against Echinococcus granulosus, the causative agent of human hydatid disease: a pilot study

Dogs are the main source of human cystic echinococcosis. An oral vaccine would be an important contribution to control programs in endemic countries. We conducted two parallel experimental trials in Morocco and Tunisia of a new oral vaccine candidate against Echinococcus granulosus in 28 dogs. The vaccine was prepared using two recombinant proteins from adult worms, a tropomyosin (EgTrp) and a fibrillar protein similar to paramyosin (EgA31), cloned and expressed in a live attenuated strain of Salmonella enterica serovar typhimurium.

In each country, five dogs were vaccinated with the associated EgA31 and EgTrp; three dogs received only the vector Salmonella; and six dogs were used as different controls. The vaccinated dogs received two oral doses of the vaccine 21 d apart, and were challenged 20 d later with 75,000 living protoscoleces. The controls were challenged under the same conditions. All dogs were sacrificed 26–29 d postchallenge, before the appearance of eggs, for safety reasons.

We studied the histological responses to both the vaccine and control at the level of the duodenum, the natural localization of the cestode. Here we show a significant decrease of parasite burden in vaccinated dogs (70% to 80%) and a slower development rate in all remaining worms. The Salmonella vaccine EgA31-EgTrp demonstrated a high efficacy against E. granulosus promoting its potential role in reducing transmission to humans and animals.

In many countries in the world, livestock and humans are affected with hydatid disease, which is caused by the development, in the viscera, of the larval stage of the cestode Echinococcus granulosus. They become infected by ingesting the eggs of this parasite, which are passed in the feces of the dog—the host of the adult worm. Domestic dogs are key in the transmission to livestock and humans.

This disease remains a major economic and public health problem in affected countries. Because dogs are quickly reinfected, control programs in these locations include monthly anthelmintic deworming. These control measures, however, are burdensome for the owner, so they often fail. In contrast, vaccination can take place in control programs at different stages of the parasite life cycle. For example, currently an effective recombinant vaccine for sheep has been developed that should work indirectly to reduce infection in dogs, which tend to eat sheep offal. However, we propose that a recombinant oral vaccine given to the small number of dogs keeping the herd would decrease the number of Echinococcus granulosus adult worms and, consequently, the number of infective eggs. This measure would help reduce the contamination risk factors for humans and livestock, and would be cost-effective for the owners of the dogs.

Invertebrate Muscles: Muscle Specific Genes and Proteins

This is the first of a projected series of canonic reviews covering all invertebrate muscle literature prior to 2005 and covers muscle genes and proteins except those involved in excitation-contraction coupling (e.g., the ryanodine receptor) and those forming ligand- and voltage-dependent channels. Two themes are of primary importance. The first is the evolutionary antiquity of muscle proteins. Actin, myosin, and tropomyosin (at least, the presence of other muscle proteins in these organisms has not been examined) exist in muscle-like cells in Radiata, and almost all muscle proteins are present across Bilateria, implying that the first Bilaterian had a complete, or near-complete, complement of present-day muscle proteins. The second is the extraordinary diversity of protein isoforms and genetic mechanisms for producing them. This rich diversity suggests that studying invertebrate muscle proteins and genes can be usefully applied to resolve phylogenetic relationships and to understand protein assembly coevolution. Fully achieving these goals, however, will require examination of a much broader range of species than has been heretofore performed.

Immunogenicity of two Echinococcus granulosus antigens EgA31 and EgTrp in mice

Here, we investigate in mice the immunogenicity of two antigens EgA31 and EgTrp which are expressed by the larval stage of Echinococcus granulosus. These recombinant proteins were used alone or as a mixture (EgA31-EgTrp) to immunize BALB/c mice. By flow cytometry, we have shown that the ratio CD4+/CD8+ of splenocytes were significantly higher in the antigen-immunized groups. The specific antibody in the sera and cytokine producing splenocytes was evaluated by enzyme-linked immunosorbent assay. EgA31, EgTrp or EgA31-EgTrp elicited high antibody titer of IgG and IgA. Among IgG isotypes, IgG1 was predominant for each antigen tested alone or combined. The production of IL-12, IFN-gamma, IL-10 and IL-6 cytokines was significantly higher in mice immunized with recombinant proteins. Our results suggest that, in BALB/c mice, a mixed Th1/Th2, response to EgA31, EgTrp and EgA31-EgTrp is obtained. The use of both antigens separately or in combination as candidate vaccine proteins is discussed.