Molecular characterization of triosephosphate isomerase from Echinococcus granulosus

Protective efficacy of six recombinant proteins as vaccine candidates against Echinococcus granulosus in dogs

BACKGROUND

Cystic echinococcosis (CE) is caused by the infection of Echinococcus granulosus sensu lato (E. granulosus s.l.), one of the most harmful zoonotic helminths worldwide. Infected dogs are the major source of CE transmission. While praziquantel-based deworming is a main measure employed to control dog infections, its efficacy is at times compromised by the persistent high rate of dog re-infection and the copious discharge of E. granulosus eggs into the environment. Therefore, the dog vaccine is a welcome development, as it offers a substantial reduction in the biomass of E. granulosus. This study aimed to use previous insights into E. granulosus functional genes to further assess the protective efficacy of six recombinant proteins in dogs using a two-time injection vaccination strategy.

METHODS

We expressed and combined recombinant E. granulosus triosephosphate isomerase (rEgTIM) with annexin B3 (rEgANXB3), adenylate kinase 1 (rEgADK1) with Echinococcus protoscolex calcium binding protein 1 (rEgEPC1), and fatty acid-binding protein (rEgFABP) with paramyosin (rEgA31). Beagle dogs received two subcutaneous vaccinations mixed with Quil-A adjuvant, and subsequently orally challenged with protoscoleces two weeks after booster vaccination. All dogs were sacrificed for counting and measuring E. granulosus tapeworms at 28 days post-infection, and the level of serum IgG was detected by ELISA.

RESULTS

Dogs vaccinated with rEgTIM&rEgANXB3, rEgADK1&rEgEPC1, and rEgFABP-EgA31 protein groups exhibited significant protectiveness, with a worm reduction rate of 71%, 57%, and 67%, respectively, compared to the control group (P < 0.05). Additionally, the vaccinated groups exhibited an inhibition of worm growth, as evidenced by a reduction in body length and width (P < 0.05). Furthermore, the level of IgG in the vaccinated dogs was significantly higher than that of the control dogs (P < 0.05).

CONCLUSION

These verified candidates may be promising vaccines for the prevention of E. granulosus infection in dogs following two injections. The rEgTIM&rEgANXB3 co-administrated vaccine underscored the potential for the highest protective efficacy and superior protection stability for controlling E. granulosus infections in dogs.

Characterization of Fructose-1,6-Bisphosphate Aldolase 1 of Echinococcus multilocularis

Glycolysis is one of the important ways by which Echinococcus multilocularis acquires energy. Fructose-1, 6-bisphosphate aldolase (FBA) plays an important role in this process, but it is not fully characterized in E. multilocularis yet. The results of genome-wide analysis showed that the Echinococcus species contained four fba genes (FBA1-4), all of which had the domain of FBA I and multiple conserved active sites. EmFBA1 was mainly located in the germinal layer and the posterior of the protoscolex. The enzyme activity of EmFBA1 was 67.42 U/mg with K_m and V_max of 1.75 mM and 0.5 mmol/min, respectively. EmFBA1 was only susceptible to Fe³⁺ but not to the other four ions (Na⁺, Ca²⁺, K⁺, Mg²⁺), and its enzyme activity was remarkably lost in the presence of 0.5 mM Fe³⁺. The current study reveals the biochemical characters of EmFBA1 and is informative for further investigation of its role in the glycolysis in E. multilocularis.

EgGLUT1 Is Crucial for the Viability of Echinococcus granulosus sensu stricto Metacestode: A New Therapeutic Target?

Cystic echinococcosis (CE) is a zoonotic parasitic disease caused by infection with the larvae of Echinococcus granulosus sensu lato (s.l.) cluster. It is urgent to identify novel drug targets and develop new drug candidates against CE. Glucose transporter 1 (GLUT1) is mainly responsible for the transmembrane transport of glucose to maintain its constant cellular availability and is a recent research hotspot as a drug target in various diseases. However, the role of GLUT1 in E. granulosus s.l. (EgGLUT1) was unknown. In this study, we cloned a conserved GLUT1 homology gene (named EgGLUT1-ss) from E. granulosus sensu stricto (s.s.) and found EgGLUT1-ss was crucial for glucose uptake and viability by the protoscoleces of E. granulosus s.s. WZB117, a GLUT1 inhibitor, inhibited glucose uptake by E. granulosus s.s. and the viability of the metacestode in vitro. In addition, WZB117 showed significant therapeutic activity in E. granulosus s.s.-infected mice: a 10 mg/kg dose of WZB117 significantly reduced the number and weight of parasite cysts (P < 0.05) as efficiently as the reference drug, albendazole. Our results demonstrate that EgGLUT1-ss is crucial for glucose uptake by the protoscoleces of E. granulosus s.s., and its inhibitor WZB117 has a therapeutic effect on CE.

Molecular characterization and serodiagnostic potential of Echinococcus granulosus hexokinase

Background

Cystic echinococcosis (CE), caused by the larval stage of Echinococcus granulosus (sensu stricto), is a life-threatening but neglected zoonosis. Glycolytic enzymes are crucial molecules for the survival and development of E. granulosus. The aim of this study was to investigate the molecular characterization, immunogenicity, tissue distribution and serodiagnostic potential of E. granulosus hexokinase (EgHK), the first key enzyme in the glycolytic pathway.

Methods

EgHK was cloned and expressed in Escherichia coli. Specific serum antibodies were evaluated in mice immunized with recombinant EgHK (rEgHK). The location of EgHK in the larval stage of E. granulosus was determined using fluorescence immunohistochemistry, and the potential of rEgHK as a diagnostic antigen was investigated in patients with CE using indirect enzyme-linked immunosorbent assay (ELISA).

Results

Recombinant EgHK could be identified in the sera of patients with CE and in mouse anti-rEgHK sera. High titers of specific immunoglobulin G were induced in mice after immunization with rEgHK. EgHK was mainly located in the tegument, suckers and hooklets of protoscoleces and in the germinal layer and laminated layer of the cyst wall. The sensitivity and specificity of the rEgHK-ELISA reached 91.3% (42/46) and 87.8% (43/49), respectively.

Conclusions

We have characterized the sequence, structure and location of EgHK and investigated the immunoreactivity, immunogenicity and serodiagnostic potential of rEgHK. Our results suggest that EgHK may be a promising candidate for the development of vaccines against E. granulosus and an effective antigen for the diagnosis of human CE.