Fasciola gigantica excretory-secretory products for immunodiagnosis and prevention of sheep fasciolosis

Transcriptomic landscape of hepatic lymph nodes, peripheral blood lymphocytes and spleen of swamp buffaloes infected with the tropical liver fluke Fasciola gigantica

The tropical liver fluke Fasciola gigantica is a parasitic helminth that has been frequently reported to infect mammals, typically involving water buffaloes. In this study, we characterized the tissue transcriptional landscape of buffaloes following infection by F. gigantica. RNAs were isolated from hepatic lymph nodes (hLNs), peripheral blood lymphocytes (pBLs), and spleen at 3-, 42- and 70-days post-infection (dpi), and all samples were subjected to RNA sequencing analyses. At 3 dpi, 2603, 460, and 162 differentially expressed transcripts (DETs) were detected in hLNs, pBLs, and spleen, respectively. At 42 dpi, 322, 937, and 196 DETs were detected in hLNs, pBLs, and spleen, respectively. At 70 dpi, 376, 334, and 165 DETs were detected in hLNs, pBLs, and spleen, respectively. Functional enrichment analysis identified upregulated immune-related pathways in the infected tissues involved in innate and adaptive immune responses, especially in hLNs at 42 and 70 dpi, and pBLs at 3 and 42 dpi. The upregulated transcripts in spleen were not enriched in any immune-related pathway. Co-expression network analysis further identified transcriptional changes associated with immune response to F. gigantica infection. Receiver operating characteristic (ROC) curve analysis showed that 107 genes in hLNs, 32 genes in pBLs, and 36 genes in spleen correlated with F. gigantica load. These findings provide new insight into molecular mechanisms and signaling pathways associated with F. gigantica infection in buffaloes.

Fasciola gigantica is a socioeconomically important tropical liver fluke of mammals, causing fascioliasis–a neglected tropical disease. In the present study, RNA sequencing and bioinformatic approach were employed to explore the global transcriptional changes of hepatic lymph nodes (hLNs), peripheral blood lymphocytes (pBLs), and spleen of water buffaloes during F. gigantica infection at 3-, 42-, and 70-days post-infection (dpi). The results revealed significant transcriptional upregulation of genes associated with innate and adaptive immune responses in infected hLNs (42 and 70 dpi) and pBLs (3 and 42 dpi). However, downregulation of transcripts involved in immune response was detected in pBLs at 70 dpi. The downregulated transcripts were enriched in metabolic pathways, such as drug metabolism-cytochrome P450 in infected hLNs at 3 dpi. These findings provide new insight into the pathogenesis of F. gigantica in its natural mammalian host.

Characterization of the Pathology, Biochemistry, and Immune Response in Kunming (KM) Mice Following Fasciola gigantica Infection

As a putative model of Fasciola gigantica infection, detailed data in Kunming (KM) mice infected with F. gigantica are lacking. In this study, KM mice were orally infected with 15 metacercaria for 8 weeks. Macroscopic and microscopic changes, serum biochemistry, cytokine responses, and changes in parasite-specific immunoglobulin G (IgG) antibody levels were monitored at 1, 3, 5, 7, and 8 weeks post-infection (wpi), respectively. The serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) increased after infection, while that of albumin (ALB) decreased, which was positively correlated with the degree of liver damage. Between 5 and 7 wpi, the mice showed symptoms of anemia and weight loss, possibly caused by the decrease of alkaline phosphatase (ALP). Moreover, the changing tendencies of the levels of globulin (GLB) and parasite-specific IgG antibody were similar, suggesting a potential correlation between GLB production and adaptive immune response in the host. Coordinated variations in interferon gamma (IFN-γ) and interleukin 4 (IL-4) indicated a mixed T helper 1 (Th1)/Th2 cellular immune response. Furthermore, the serum IgG antibody increased after infection and peaked at 5 wpi, and it was positively correlated with the average parasite burdens. The worms collected from mice were approximately 1 cm in length at 8 wpi, their digestive and reproductive systems were well developed, and no eggs were found in the uterus. To the best of our knowledge, this is the first report describing detailed histological, biochemical, and immunological indices in KM mice infected with F. gigantica, which provides basic information on KM mice against infection with F. gigantica.

Milk As a New Diagnostic Tool for Rapid Detection of Fascioliasis in Dairy Goats Using Excretory/Secretory Antigen

PURPOSE

Fascioliasis is a serious livestock illness of particular importance for dairy goats; the objectives of this study were to describe effects of F. gigantica on milk composition and to use this information to estimate economic damages linked with Fasciola spp. infections. Furthermore, the study sought to standardize the use of milk instead of serum for early diagnosis of fascioliasis in dairy goats.

METHODS

One-hundred samples of goat milk along with corresponding blood samples were obtained at random from flocks in Cairo and Giza Governorates. The ELISA and DOT-ELISA were performed in both serum and milk of dairy goats.

RESULTS

Total mesophilic count (mean value) was 2.12 × 10⁶ ± 1.63 × 10⁵ CFU/ml in enzyme-linked immunosorbent assay (ELISA) positive samples and 1.46 × 10⁴ ± 8.58 × 10² CFU/ml in ELISA-negative samples. The mean values were significantly different (P < 0.05). The mean values of percentages of fat, SNF, protein, salts, lactose, pH, and MSCC/ml in ELISA-positive samples were 2.3 ± 0.17, 8.21 ± 0.63, 3.08 ± 0.18, 0.90 ± 0.06, 3.64 ± 0.28, 6.93 + 0.53, and 1.18 × 10⁶ ± 9.07 × 10⁴ cells/ml, respectively. A significant difference (P < 0.05) between the mean values of two composition parameters, i.e., percent of fat and MSCC/ml in ELISA-positive and -negative samples, for Fasciola gigantica was observed. The antigen used for the diagnosis of F. gigantica was excretory/secretory (E/S) antigen. The dilutions of (E/S) concentrations after checkerboard titration for indirect ELISA were 20 μg/ml protein and for dot-ELISA, 300 ng/μl. Sera dilution was 1:100 in the two tests, and milk dilution was 1:50 for indirect ELISA, and 1:25 for dot-ELISA. The two tests were performed using known F. gigantica positive and negative goat sera and known rat hyper immunized negative and positive sera against E/S antigen of F. gigantica as well as known sera for paramphistomes without F. gigantica infection. The cutoff values in indirect ELISA were 0.45 for sera and 0.35 for milk.

CONCLUSION

The application of different serological technique in goat farms reveals a good test in rapid diagnosis of fascioliasis especially the uses of dot ELISA when using the milk instead of the serum.

Fasciola gigantica-Derived Excretory-Secretory Products Alter the Expression of mRNAs, miRNAs, lncRNAs, and circRNAs Involved in the Immune Response and Metabolism in Goat Peripheral Blood Mononuclear Cells

Fasciola gigantica produces excretory-secretory products (ESPs) with immune-modulating effects to promote its own survival. In this study, we performed RNA-seq to gain a comprehensive global understanding of changes in the expression of mRNAs, miRNAs, lncRNAs, and circRNAs in goat peripheral blood mononuclear cells (PBMCs) treated with F. gigantica ESPs. A total of 1,544 differently expressed mRNAs (790 upregulated and 754 downregulated genes), 30 differently expressed miRNAs (24 upregulated and 6 downregulated genes), 136 differently expressed circRNAs (83 upregulated and 53 downregulated genes), and 1,194 differently expressed lncRNAs (215 upregulated and 979 downregulated genes) were identified. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that F. gigantica ESPs altered the expression of genes associated with the host immune response, receptor signaling, disease and metabolism. Results from RNA-seq were validated by qRT-PCR. These findings provide an important resource for future investigation of the role of mRNAs and non-coding RNAs in mediating the immune-modulating effects of F. gigantica ESPs.

Dysregulation of hepatic microRNA expression in C57BL/6 mice affected by excretory-secretory products of Fasciola gigantica

The excretory-secretory products released by the liver fluke Fasciola gigantica (FgESPs) play important roles in regulating the host immune response during the infection. Identification of hepatic miRNAs altered by FgESPs may improve our understanding of the pathogenesis of F. gigantica infection. In this study, we investigated the alterations in the hepatic microRNAs (miRNAs) in mice treated with FgESPs using high-throughput small RNA (sRNA) sequencing and bioinformatics analysis. The expression of seven miRNAs was confirmed by quantitative stem-loop reverse transcription quantitative PCR (qRT-PCR). A total of 1,313 miRNAs were identified in the liver of mice, and the differentially expressed (DE) miRNAs varied across the time lapsed post exposure to FgESPs. We identified 67, 154 and 53 dysregulated miRNAs at 1, 4 and 12 weeks post-exposure, respectively. 5 miRNAs (miR-126a-3p, miR-150-5p, miR-155-5p, miR-181a-5p and miR-362-3p) were commonly dysregulated at the three time points. We also found that most of the DE miRNAs were induced by FgESPs in the mouse liver after 4 weeks of exposure. These were subjected to Gene Ontology (GO) enrichment analysis, which showed that the predicted targets of the hepatic DE miRNAs of mice 4 weeks of FgESPs injection were enriched in GO terms, including cell membrane, ion binding, cellular communication, organelle and DNA damage. KEGG analysis indicated that the predicted targets of the most downregulated miRNAs were involved in 15 neural activity-related pathways, 6 digestion-related pathways, 20 immune response-related pathways and 17 cancer-related pathways. These data provide new insights into how FgESPs can dysregulate hepatic miRNAs, which play important roles in modulating several aspects of F. gigantica pathogenesis.

DNA methylation and hydroxymethylation profiles reveal possible role of highly methylated TLR signaling on Fasciola gigantica excretory/secretory products (FgESPs) modulation of buffalo dendritic cells

BACKGROUND

Excretory/secretory products (ESPs) released by parasites influence the development and functions of host dendritic cells (DCs). However, little is known about changes of DNA (hydroxy)methylation on DC development during Fasciola gigantica infection. The present study aimed to investigate whether F. gigantica ESPs (FgESPs) affects the development and functions of buffalo DCs through altering the DNA (hydroxy)methylation of DCs.

METHODS

Buffalo DCs were prepared from peripheral blood mononuclear cells (PBMCs) and characterized using scanning and transmission electron microscopy (SEM/TEM) and quantitative reverse transcriptional PCR (qRT-RCR). DCs were treated with 200 μg/ml of FgESPs in vitro, following DNA extraction. The DNA methylome and hydroxymethylome were profiled based on (hydroxy)methylated DNA immunoprecipitation sequencing [(h)MeDIP-Seq] and bioinformatics analyses. qRT-RCR was also performed to assess the gene transcription levels of interest.

RESULTS

FgESPs markedly suppressed DC maturation evidenced by morphological changes and downregulated gene expression of CD1a and MHC II. Totals of 5432 and 360 genes with significant changes in the 5-methylcytosine (5-mC) and the 5-hydroxymethylcytosine (5-hmC) levels, respectively, were identified in buffalo DCs in response to FgESPs challenge. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that these differentially expressed genes were highly enriched in pathways associated with immune response. Some cancer-related pathways were also indicated. There were 111 genes demonstrating changes in both 5-mC and 5-hmC levels, 12 of which were interconnected and enriched in 12 pathways. The transcription of hypermethylated genes TLR2, TLR4 and IL-12B were downregulated or in a decreasing trend, while the mRNA level of high-hydroxymethylated TNF gene was upregulated in buffalo DCs post-exposure to FgESPs in vitro.

CONCLUSIONS

To our knowledge, the present study provides for the first time a unique genome-wide profile of DNA (hydroxy)methylation for DCs that interact with FgESPs, and suggests a possible mechanism of FgESPs in suppressing DC maturation and functions that are involved in TLR signaling.

Transcriptome and excretory-secretory proteome of infective-stage larvae of the nematode Gnathostoma spinigerum reveal potential immunodiagnostic targets for development

Background: Gnathostoma spinigerum is a harmful parasitic nematode that causes severe morbidity and mortality in humans and animals. Effective drugs and vaccines and reliable diagnostic methods are needed to prevent and control the associated diseases; however, the lack of genome, transcriptome, and proteome databases remains a major limitation. In this study, transcriptomic and secretomic analyses of advanced third-stage larvae of G. spinigerum (aL3Gs) were performed using next-generation sequencing, bioinformatics, and proteomics. Results: An analysis that incorporated transcriptome and bioinformatics data to predict excretory–secretory proteins (ESPs) classified 171 and 292 proteins into classical and non-classical secretory groups, respectively. Proteins with proteolytic (metalloprotease), cell signaling regulatory (i.e., kinases and phosphatase), and metabolic regulatory function (i.e., glucose and lipid metabolism) were significantly upregulated in the transcriptome and secretome. A two-dimensional (2D) immunomic analysis of aL3Gs-ESPs with G. spinigerum-infected human sera and related helminthiases suggested that the serine protease inhibitor (serpin) was a promising antigenic target for the further development of gnathostomiasis immunodiagnostic methods. Conclusions: The transcriptome and excretory–secretory proteome of aL3Gs can facilitate an understanding of the basic molecular biology of the parasite and identifying multiple associated factors, possibly promoting the discovery of novel drugs and vaccines. The 2D-immunomic analysis identified serpin, a protein secreted from aL3Gs, as an interesting candidate for immunodiagnosis that warrants immediate evaluation and validation.

Diagnostic potential of low molecular weight excretory secretory proteins of Paramphistomum epiclitum for caprine amphistomosis

In the present study, the 75% alcoholic fractionation of excretory-secretory (ES) antigen isolated from 200 to 300 live P. epiclitum was assessed for its diagnostic potential for the detection of caprine amphistomosis by using antibody detection enzyme immunoassay. Prior to enzyme immunoassay, 75% alcoholic fractionation of excretory-secretory (ES) antigen was subjected to SDS- PAGE and western blot analysis for the presence of immunoreactive polypeptides. SDS-PAGE analysis of ES antigen resolved a total 7 polypeptides bands of size 56, 27, 25, 22.5, 12, 11 and 10 kDa. Western blot analysis revealed only two immunoreactive polypeptides (11 kDa and 12 kDa) when polypeptides resolved in SDS-PAGE were probed with known positive pooled serum. None of the polypeptides showed reactions with pooled known negative serum. The working dilutions of antigen, sera and conjugates were determined by checkerboard titration for employing ELISA and cut-off O.D. was calculated 0.616 by using the mean absorbance value of 11 negative kid sera. The sensitivity and specificity of ELISA was found to be 100% and 86.76%, respectively. As per kappa value estimation, the strength of agreement was found to be good. Antibodies to 75% alcoholic fractionation of ES antigen was detected in 20% goats (n = 160) of either sex, although faecal examination detected 10.6% goats to be infected with amphistomosis. The study confirmed that 75% alcoholic fractionation of ES antigen of P. epiclitum based ELISA had good value for serodiagnosis of caprine amphistomosis.

A. AS, Abidi SMA. Immunolocalization and immunodetection of the excretory/secretory (ES) antigens of Fasciola gigantica

The digenetic trematode Fasciola gigantica is a parasite of great agricultural and economic importance. Along with Fasciola hepatica, F. gigantica incurs huge economic losses to the agricultural sector. Because of unavailability of an effective and commercial vaccine, the earliest diagnosis of the disease is the only way to control the disease. The conventional coprological techniques are able to detect the disease only after the parasites get matured and starts releasing their eggs with the faeces of host, therefore prepatent infection remain undiagnosed. The alternative method is by serological tests that uses circulatory antigens. Despite high sensitivity, their reliability is quite low because of the common antigens shared between different helminth parasites. To overcome this, investigation was shifted to identify the copro-antigens which could be more sensitive and reliable. In the present study, we tried to identify some of the immunodominant proteins from the Excretory Secretory (ES) product of F. gigantica which can be further characterized and used for early detection of infection and also as drug and vaccine candidates. The ES products of F. gigantica were collected and used for raising the polyclonal antibody in rabbit. The polypeptide profile was generated as well as immunogenic polypeptides were identified. The Source of ES antigen was immunolocalized using confocal microscopy and dot blot assay was performed to diagnose field infection. The polypeptide profile of ES products revealed a total of 24 polypeptides out of which 12 immunogenic polypeptides were identified by western blotting. Confocal micrographs showed the immunolocalization of antigens in the intestinal caecae, vitalline glands, gonads as well as in the tegument of the worm. The dot blot assay confirmed the utility of ES products for the detection of field infection. Subsequently, cross reactivity was found negative with Gigantocotyle explanatum; an amphitome parasite of same habitat. However, the cross reactivity with other helminths needs to be worked out.

Fasciola gigantica enolase is a major component of worm tegumental fraction protective against sheep fasciolosis

Infection of cattle and sheep with the parasite Fasciola gigantica is a cause of important economic losses throughout Asia and Africa. Many of the available anthelmintics have undesirable side effects, and the parasite may acquire drug resistance as a result of mass and repeated treatments of livestock. Accordingly, the need for developing a vaccine is evident. Triton-soluble surface membrane and tegumental proteins (TSMTP) of 60, 32, and 28 kDa previously shown to elicit protective immunity in mice against challenge F. gigantica infection were found to be strongly immunogenic in sheep eliciting vigorous specific antibody responses to a titer>1:16,000 as assessed by enzyme-linked immunosorbent assay. Furthermore, the 60 kDa fraction induced production of antibodies able to bind to the surface membrane of newly excysted juvenile flukes and mediate their attrition in antibody-dependent complement- and cell-mediated cytotoxicity assays, and significant (P<0.05) 40% protection of sheep against F. gigantica challenge infection. Amino acid micro sequencing of the 60 kDa-derived tryptic peptides revealed the fraction predominantly consists of F. gigantica enolase. The cDNA nucleotide and translated amino acid sequences of F. gigantica enolase showed homology of 92% and 95%, respectively to Fasciola hepatica enolase, suggesting that a fasciolosis vaccine might be effective against both tropical and temperate liver flukes.

The role of Ser-(Arg-Ser-Arg-Ser-GlucNAc)19-GlucNAc Fasciola gigantica glycoprotein in the diagnosis of prepatent fasciolosis in rabbits

In the present study, the carbohydrate structures associated with Fasciola gigantica adult worm were identified by indirect hemagglutination inhibition test. Glucose was found to be the main monosaccharide associated with the fluke. According to indirect hemagglutination inhibition results, purification of glycoprotein fractions from worm crude extract was carried out by affinity chromatography immobilized glucose agarose gel and Con-A lectin columns. The isolated glycoprotein fractions, FI and FII, were characterized by SDS-PAGE which revealed one band in FI of 26 kDa and another one band of 19.5 kDa in FII compared with 12 bands associated with whole worm extract. Both fractions were also characterized by isoelectric focusing technique which proved that both bands were acidic in nature with pIs 6.4 and 6.5 respectively. The comparative diagnostic evaluation of the two isolated glycoprotein fractions and crude extract of experimental fasciolosis in rabbits by ELISA revealed that FII was more potent in the diagnosis during prepatent (first week post infection) and patent periods (10 weeks post infection) than FI and crude extract. Moreover, infected rabbit sera at ten weeks post infection identified both bands; 26 and 19.5 kDa in western blot analysis confirming its immunodiagnostic activities which was proved previously by ELISA. FII proved potency in diagnosis of fasciolosis in 200 buffalo serum samples of different ages and sexes using ELISA which recorded 95 % positive and 5 % negative samples. Moreover, the detailed structural analyses of the most potent fraction, F11, using mass spectrum was made and elucidated chemical structure; O-glycan [Ser-(Arg-Ser-Arg-Ser-GlucNAc)19-GlucNAc]. The present result introduces GlucNAc rich fraction of F .gigantica that can be used successfully in the diagnosis of acute and chronic fasciolosis.

Immunodiagnosis of fascioliasis using sandwich enzyme-linked immunosorbent assay for detection of Fasciola gigantica paramyosin antigen

Background:

Many immunological techniques have been developed over years using the different Fasciola antigens for diagnosis of parasitic infection and to replace the parasitological techniques, which are time consuming and usually lack sensitivity and reproducibility.

Materials and Methods:

In this study, Fasciola gigantica paramyosin (Pmy) antigen was early detected in cattle sera using sandwich enzyme-linked immunosorbent assay (ELISA), to evaluate the Pmy antigen performance in diagnosis. This work was conducted on 135 cattle blood samples, which were classified according to parasitological investigation into, healthy control (30), fascioliasis (75), and other parasites (30) groups.

Results:

The sensitivity of Sandwich ELISA was 97.33%, and the specificity was 95%, in comparison with parasitological examination, which recorded 66.66% sensitivity and 100% specificity, respectively.

Conclusions:

It was clear that the native F. gigantica Pmy is considered as a powerful antigen in early immunodiagnosis of fascioliasis, using a highly sensitive and specific sandwich ELISA technique.

Antigenic components, isolation and partial characterization of excretion-secretion fraction of Paramphistomum cervi

The immunogenic components of adult Paramphistomum cervi excretion-secretion (ES) fraction were revealed by SDS-PAGE and immunoblotting technique using sera from cattle naturally infected with P. cervi, Fasciola gigantica, strongylids, Trichuris sp., and Strongyloides sp. By SDS-PAGE, it was found that the ES fraction comprised 13 distinct protein bands. Immunoblotting analysis of these proteins exhibited nine prominent antigenic bands which were recognized by paramphistomosis antisera. These antigenic proteins had molecular weights ranging from 10-170 kDa. One antigenic protein band of 40 kDa was found to give a consistent reaction with sera from all infected cattle. Its diagnostic sensitivity, specificity and accuracy using this test were 100%, 98.9% and 99.3%, respectively. The positive and negative predictive values were 98% and 100%, respectively. The 40 kDa antigen was partially purified by gel filtration and ion-exchange chromatography. The antigenicity of 40 kDa protein for diagnosis of P. cervi infection was confirmed by immunoblotting and indirect ELISA (at 1:78,125 dilution) using a pool of sera and individual serum samples from infected cattle. The present findings suggest that the 40 kDa protein may be used as a diagnostic antigen for paramphistomosis.

Evaluation and characterization of Fasciola hepatica tegument protein extract for serodiagnosis of human fascioliasis

Tegument protein extract from Fasciola hepatica adult flukes (FhTA) was obtained and assessed for its potential as a diagnostic agent for the serological detection of human fascioliasis using an indirect enzyme-linked immunosorbent assay (ELISA). In an analysis of sera from 45 patients infected with F. hepatica, sera from 41 patients with other parasitic infections, and sera from 33 healthy controls, the FhTA-ELISA showed sensitivity, specificity, and accuracy of 91.1%, 97.3%, and 95%, respectively. Specific IgG1 and IgG4 were the antibody isotypes mainly detected in sera from patients with fascioliasis. Polypeptides of 52, 38, 24 to 26, and 12 to 14 kDa were identified by Western blotting as the most immunoreactive components of the FhTA. A proteomic approach led us to identify enolase, aldolase, glutathione S-transferase, and fatty acid binding protein as the major immunoreactive components of the FhTA.