Echinococcus multilocularis: purification and characterization of glycoprotein antigens with serodiagnostic potential for canine infection

Serodiagnosis of nasal myasis in camels (Camelus dromedaries) in Egypt using third larval instar affinity-purified glycoprotein

The larvae of Cephalopina titillator cause nasopharyngeal myiasis in camels, which parasitize the living tissues of the nasal and paranasal sinuses, pharynx, and larynx. C. titillator infestation adversely affects camel health, meat, and milk production, and can even cause death. In our study, to improve the immunodiagnosis of camel nasal myiasis, a sensitive and specific enzyme-linked immunosorbent assay (ELISA) was developed and evaluated using the Concanavalin-A (Con-A) affinity purification for the C. titillator-N-acetylglucosamine (Ct-GlucNAc) glycoprotein fraction from third larval instars as an antigen for detecting C. titillator antibodies. Crude antigens were prepared from larval instars of C. titillator and evaluated by indirect ELISA. The third C. titillator larval antigen (L3Ct) had the highest protein content (P < 0.001) and the best diagnostic value; chi-square = 235 (P < 0.001). Four glycoprotein fractions were purified separately from the L3Ct antigen by Con-A purification and evaluated. The Ct-GlucNAc glycoprotein fraction was the fraction of choice with the highest diagnostic accuracy (P < 0.05). Using Ct-GlucNAc as a coating antigen, indirect ELISA showed a 99.3% sensitivity for positive results in camel myiasis samples and 100% specificity for negative results in healthy camel samples. The diagnostic accuracy was 99.7%, and no cross reactivity was detected for other parasitic diseases. The indirect ELISA results were confirmed by the western immunoblotting which was characterized by comparing sera from naturally infested dromedary camels with C. titillator, sera from healthy camels and sera from camels with other parasitic infections (Echinococcus granulosus, Fasciola gigantica, Hard ticks; Hyalomma dromedarii, Trichostronglid sp., Eimeria spp., and Cryptosporidium sp.). Immunoreactive antigenic bands of 63, 50, 30 and 18 kDa were predominantly detected in sera from camels with nasopharyngeal myiasis and didn't react with healthy and camel's sera from other parasitic infections. However, seven immunoreactive bands appeared at 120, 70, 63, 48, 35, 29, and 19 kDa in the crude L3Ct antigen. In addition, a positive rate of C. titillator immunodiagnosis was detected by indirect ELISA (48.6%, chi-square = 483, P < 0.001), which was significantly greater than that of postmortem diagnosis (31%). In conclusion, the current study introduces a new diagnostic immunoaffinity glycoprotein fraction of C. titillator 3rd larval instar-based ELISA as a highly accurate, simple and fast method to detect specific antibodies of nasal myiasis in camels.

Metaperiodate deglycosylation of Strongyloides venezuelensis larvae: Immunochemical characterization and antigen production for human strongyloidiasis diagnosis

Strongyloidiasis is an important helminthiasis affecting million people worldwide. The aim of this study was to use sodium metaperiodate (MP) treatment to immunochemically characterize Strongyloides venezuelensis filariform larvae and use MP-treated heterologous antigen to detect IgG and subclasses in serum. Samples from individuals with definitive diagnosis of strongyloidiasis (n = 50), other parasitic diseases (n = 60) and negative endemic (n = 50) were tested. TG-ROC and two-way ANOVA were applied. MP-treatment resulted on differential localization of carbohydrates at larval structure and no carbohydrate content in saline extract (SE). Electrophoretic profiles were similar before and after treatment. ELISA sensitivity and specificity were: 90%; 88.2% for SE and 92.0%; 94.6% for MP, respectively. When using MP treated antigen we observed reduction in IgG1 and IgG3 detection in strongyloidiasis group and decrease of cross reactions in control groups. Our data demonstrate the role of carbohydrate residues in cross reactions and on the recognition of anti-Strongyloides IgG and its subclasses.

Bioinformatic prediction of the epitopes of Echinococcus granulosus antigen 5

The aim of the present study was to predict and analyze the secondary structure, and B and T cell epitopes of Echinococcus granulosus antigen 5 (Ag5) using online software in order to investigate its immunogenicity and preliminarily evaluate its potential as an effective antigen peptide vaccine for cystic echinococcosis. The PortParam program was used to analyze molecular weight, the theoretical isoelectric point, instability index and other physicochemical properties. The secondary structure of the Ag5 protein was predicted using Self-Optimized Prediction method With Alignment and the tertiary structure of the Ag5 protein was predicted using 3DLigandSite together with Center for Biological Sequence Analysis Prediction Servers. Furthermore, the Immune Epitope Database software was used to predict B cell epitopes, and T cell epitopes were predicted with the BioInformatics and Molecular Analysis Section and SYFPEITHI programs. The results demonstrated that α-helixes, β-turns, random coils and extended strands account for 23.35, 10.95, 41.32, and 24.38% of the secondary structure of the Ag5 protein, respectively. Ten potential B cell epitopes of Ag5 were identified as the amino acids sequences 27-39, 70-80, 117-130, 146-168, 250-262, 284-293, 339-349, 359-371, 403-412 and 454-462, and seven potential T cell epitopes were identified as the amino acid sequences 52-60, 57-65, 182-190, 231-239, 273-281, 318-326 and 467-475. Thus, ten B cell epitopes and seven T cell epitopes were identified on Ag5, suggesting the strong immunogenicity of this protein, which could be applied to design antigen peptide vaccines for echinococcosis.

The timing of worm exclusion in dogs repeatedly infected with the cestode Echinococcus multilocularis

Experimental Echinococcus multilocularis infection and deworming was repeated three or five times in nine dogs at various re-infection schedules. The mean number of worms decreased more than 91% in dogs with repeated infection, compared to first infection controls (n= 6). The copro-antigen assay and the egg count in the faeces suggested that the worm burden gradually decreased each time the dogs were re-infected. To examine whether such worm exclusion was a non-specific response, five dogs were sequentially infected with the parasite four times and subsequently fed freely for 6 months. Even after the 6-month interval, the five dogs that were infected five times with the parasite were still able largely to exclude the adult worms. The results suggested that the ability of worm exclusion in dogs that developed a resistance did not become rapidly extinct. Observation of the condition of faeces and the excretion of hooks in the faeces of repeatedly infected dogs revealed that the exclusion of worms started at the first week after the re-infection, and it continued during the patent period. Serum antibodies specific to the parasite antigen increased gradually until the third infection and significantly decreased during the 6-month interval. There was little enhancement of serum antibodies after the fifth infection in most dogs, although no clear correlation was observed between the antibody response and the worm burden. These findings suggested the possibility of developing a vaccine.

Glycoconjugates in host-helminth interactions

Helminths are multicellular parasitic worms that comprise a major class of human pathogens and cause an immense amount of suffering worldwide. Helminths possess an abundance of complex and unique glycoconjugates that interact with both the innate and adaptive arms of immunity in definitive and intermediate hosts. These glycoconjugates represent a major untapped reservoir of immunomodulatory compounds, which have the potential to treat autoimmune and inflammatory disorders, and antigenic glycans, which could be exploited as vaccines and diagnostics. This review will survey current knowledge of the interactions between helminth glycans and host immunity and highlight the gaps in our understanding which are relevant to advancing therapeutics, vaccine development, and diagnostics.

Characterization of the carbohydrate components of Taenia solium oncosphere proteins and their role in the antigenicity

This study examines the carbohydrate composition of Taenia solium whole oncosphere antigens (WOAs), in order to improve the understanding of the antigenicity of the T. solium. Better knowledge of oncosphere antigens is crucial to accurately diagnose previous exposure to T. solium eggs and thus predict the development of neurocysticercosis. A set of seven lectins conjugates with wide carbohydrate specificity were used on parasite fixations and somatic extracts. Lectin fluorescence revealed that D-mannose, D-glucose, D-galactose and N-acetyl-D-galactosamine residues were the most abundant constituents of carbohydrate chains on the surface of T. solium oncosphere. Lectin blotting showed that posttranslational modification with N-glycosylation was abundant while little evidence of O-linked carbohydrates was observed. Chemical oxidation and enzymatic deglycosylation in situ were performed to investigate the immunoreactivity of the carbohydrate moieties. Linearizing or removing the carbohydrate moieties from the protein backbones did not diminish the immunoreactivity of these antigens, suggesting that a substantial part of the host immune response against T. solium oncosphere is directed against the peptide epitopes on the parasite antigens. Finally, using carbohydrate probes, we demonstrated for the first time that the presence of several lectins on the surface of the oncosphere was specific to carbohydrates found in intestinal mucus, suggesting a possible role in initial attachment of the parasite to host cells.

Characterization of a surface glycoprotein from Echinococcus multilocularis and its mucosal vaccine potential in dogs

Alveolar echinococcosis is a refractory disease caused by the metacestode stage of Echinococcus multilocularis. The life cycle of this parasite is maintained primarily between foxes and many species of rodents; thus, dogs are thought to be a minor definitive host except in some endemic areas. However, dogs are highly susceptible to E. multilocularis infection. Because of the close contact between dogs and humans, infection of dogs with this parasite can be an important risk to human health. Therefore, new measures and tools to control and prevent parasite transmission required. Using 2-dimensional electrophoresis followed by western blot (2D-WB) analysis, a large glycoprotein component of protoscoleces was identified based on reactivity to intestinal IgA in dogs experimentally infected with E. multilocularis. This component, designated SRf1, was purified by gel filtration using a Superose 6 column. Glycosylation analysis and immunostaining revealed that SRf1 could be distinguished from Em2, a major mucin-type antigen of E. multilocularis. Dogs (n = 6) were immunized intranasally with 500 µg of SRf1 with cholera toxin subunit B by using a spray syringe, and a booster was given orally using an enteric capsule containing 15 mg of the same antigen. As a result, dogs immunized with this antigen showed an 87.6% reduction in worm numbers compared to control dogs (n = 5) who received only PBS administration. A weak serum antibody response was observed in SRf1-immunized dogs, but there was no correlation between antibody response and worm number. We demonstrated for the first time that mucosal immunization using SRf1, a glycoprotein component newly isolated from E. multilocularis protoscoleces, induced a protection response to E. multilocularis infection in dogs. Thus, our data indicated that mucosal immunization using surface antigens will be an important tool to facilitate the development of practical vaccines for definitive hosts.

Bioinformatic prediction of epitopes in the Emy162 antigen of Echinococcus multilocularis

The aim of the present study was to predict the secondary structure and the T- and B-cell epitopes of the Echinococcus multilocularis Emy162 antigen, in order to reveal the dominant epitopes of the antigen. The secondary structure of the protein was analyzed using the Gamier-Robson method, and the improved self-optimized prediction method (SOPMA) server. The T- and B-cell epitopes of Emy162 were predicted using Immune Epitope Database (IEDB), Syfpeithi, Bcepred and ABCpred online software. The characteristics of hydrophilicity, flexibility, antigenic propensity and exposed surface area were predicted. The tertiary structure of the Emy162 protein was predicted by the 3DLigandSite server. The results demonstrated that random coils and β sheets accounted for 34.64 and 21.57% of the secondary structure of the Emy162 protein, respectively. This was indicative of the presence of potential dominant antigenic epitopes in Emy162. Following bioinformatic analysis, numerous distinct antigenic epitopes of Emy162 were identified. The high-scoring T-cell epitopes were located at positions 16–29, 36–39, 97–103, 119–125 and 128–135, whilst the likely B-cell epitopes were located at positions 8–10, 19–25, 44–50, 74–81, 87–93, 104–109 and 128–136. In conclusion, five T-cell and seven B-cell dominant epitopes of the Emy162 antigen were revealed by the bioinformatic methods, which may be of use in the development of a dominant epitope vaccine.