Variability in the Response against Teladorsagia circumcincta in Lambs of Two Canarian Sheep Breeds.

The increasing resistance to anthelmintics has necessitated the exploration of alternative control strategies of gastrointestinal nematode (GIN) infections. A sustainable option is genetic selection based on differences in susceptibility to GIN infection between and within breeds of sheep. Here, three-month-old Canaria Hair breed (GIN-resistant) and Canaria Sheep breed (GIN-susceptible) showed no significant between-breed differences after trickle infection with Teladorsagia circumcincta, whereas considerable individual variability was found in both breeds. Next, data from lambs of both breeds were used to explore the relationships between parasitological variables and T. circumcincta-specific IgA levels, local immune cell populations, and abomasal lymph node gene expression to understand the possible mechanisms underlying resistance. Mucosal IgA levels as well as numbers of globular leukocytes and MHC-II+ cells were associated with protection. Analysis of lymph node gene expression revealed the associations between lower parasite numbers and cumulative fecal egg counts and several immune pathways, such as leukocyte cell adhesion, activation and differentiation of T cells, in particular CD4+ and IL-4 production. The data obtained here may inform on the relationship between phenotypic resistance variability and protective responses at the humoral, cellular, and transcriptomic levels, thus contributing to identifying immune responses in young lambs that could be used as markers for selection.

Transcriptomic analysis of the poultry red mite, Dermanyssus gallinae, across all stages of the lifecycle.

BACKGROUND: The blood feeding poultry red mite (PRM), Dermanyssus gallinae, causes substantial economic damage to the egg laying industry worldwide, and is a serious welfare concern for laying hens and poultry house workers. In this study we have investigated the temporal gene expression across the 6 stages/sexes (egg, larvae, protonymph and deutonymph, adult male and adult female) of this neglected parasite in order to understand the temporal expression associated with development, parasitic lifestyle, reproduction and allergen expression. RESULTS: RNA-seq transcript data for the 6 stages were mapped to the PRM genome creating a publicly available gene expression atlas (on the OrcAE platform in conjunction with the PRM genome). Network analysis and clustering of stage-enriched gene expression in PRM resulted in 17 superclusters with stage-specific or multi-stage expression profiles. The 6 stage specific superclusters were clearly demarked from each other and the adult female supercluster contained the most stage specific transcripts (2725), whilst the protonymph supercluster the fewest (165). Fifteen pairwise comparisons performed between the different stages resulted in a total of 6025 Differentially Expressed Genes (DEGs) (P > 0.99). These data were evaluated alongside a Venn/Euler analysis of the top 100 most abundant genes in each stage. An expanded set of cuticle proteins and enzymes (chitinase and metallocarboxypeptidases) were identified in larvae and underpin cuticle formation and ecdysis to the protonymph stage. Two mucin/peritrophic-A salivary proteins (DEGAL6771g00070, DEGAL6824g00220) were highly expressed in the blood-feeding stages, indicating peritrophic membrane formation during feeding. Reproduction-associated vitellogenins were the most abundant transcripts in adult females whilst, in adult males, an expanded set of serine and cysteine proteinases and an epididymal protein (DEGAL6668g00010) were highly abundant. Assessment of the expression patterns of putative homologues of 32 allergen groups from house dust mites indicated a bias in their expression towards the non-feeding larval stage of PRM. CONCLUSIONS: This study is the first evaluation of temporal gene expression across all stages of PRM and has provided insight into developmental, feeding, reproduction and survival strategies employed by this mite. The publicly available PRM resource on OrcAE offers a valuable tool for researchers investigating the biology and novel interventions of this parasite.

Cellular and humoral immune responses associated with protection in sheep vaccinated against Teladorsagia circumcincta.

Due to increased anthelmintic resistance, complementary methods to drugs are necessary to control gastrointestinal nematodes (GIN). Vaccines are an environmentally-friendly and promising option. In a previous study, a Teladorsagia circumcincta recombinant sub-unit vaccine was administered to two sheep breeds with different levels of resistance against GIN. In the susceptible Canaria Sheep (CS) breed, vaccinates harboured smaller worms with fewer eggs in utero than the control group. Here, we extend this work, by investigating the cellular and humoral immune responses of these two sheep breeds following vaccination and experimental infection with T. circumcincta. In the vaccinated CS group, negative associations between antigen-specific IgA, IgG2 and Globule Leukocytes (GLs) with several parasitological parameters were established as well as a higher CD4+/CD8+ ratio than in control CS animals, suggesting a key role in the protection induced by the vaccine. In the more resistant Canaria Hair Breed (CHB) sheep the vaccine did not significantly impact on the parasitological parameters studied and none of these humoral associations were observed in vaccinated CHB lambs, although CHB had higher proportions of CD4+ and CD8+ T cells within the abomasal lymph nodes, suggesting higher mucosal T cell activation. Each of the component proteins in the vaccine induced an increase in immunoglobulin levels in vaccinated groups of each breed. However, levels of immunoglobulins to only three of the antigens (Tci-MEP-1, Tci-SAA-1, Tci-ASP-1) were negatively correlated with parasitological parameters in the CS breed and they may be, at least partially, responsible for the protective effect of the vaccine in this breed. These data could be useful for improving the current vaccine prototype.

A genomic analysis and transcriptomic atlas of gene expression in Psoroptes ovis reveals feeding- and stage-specific patterns of allergen expression.

BACKGROUND: Psoroptic mange, caused by infestation with the ectoparasitic mite, Psoroptes ovis, is highly contagious, resulting in intense pruritus and represents a major welfare and economic concern for the livestock industry Worldwide. Control relies on injectable endectocides and organophosphate dips, but concerns over residues, environmental contamination, and the development of resistance threaten the sustainability of this approach, highlighting interest in alternative control methods. However, development of vaccines and identification of chemotherapeutic targets is hampered by the lack of P. ovis transcriptomic and genomic resources. RESULTS: Building on the recent publication of the P. ovis draft genome, here we present a genomic analysis and transcriptomic atlas of gene expression in P. ovis revealing feeding- and stage-specific patterns of gene expression, including novel multigene families and allergens. Network-based clustering revealed 14 gene clusters demonstrating either single- or multi-stage specific gene expression patterns, with 3075 female-specific, 890 male-specific and 112, 217 and 526 transcripts showing larval, protonymph and tritonymph specific-expression, respectively. Detailed analysis of P. ovis allergens revealed stage-specific patterns of allergen gene expression, many of which were also enriched in "fed" mites and tritonymphs, highlighting an important feeding-related allergenicity in this developmental stage. Pair-wise analysis of differential expression between life-cycle stages identified patterns of sex-biased gene expression and also identified novel P. ovis multigene families including known allergens and novel genes with high levels of stage-specific expression. CONCLUSIONS: The genomic and transcriptomic atlas described here represents a unique resource for the acarid-research community, whilst the OrcAE platform makes this freely available, facilitating further community-led curation of the draft P. ovis genome.

Impacts of breed type and vaccination on Teladorsagia circumcincta infection in native sheep in Gran Canaria.

Vaccines and genetic resistance offer potential future alternatives to the exclusive use of anthelmintics to control gastrointestinal nematodes (GIN). Here, a Teladorsagia circumcincta prototype vaccine was administered to two sheep breeds which differ in their relative levels of resistance to infection with GIN. Vaccination of the more susceptible Canaria Sheep (CS) breed induced significant reductions in worm length and numbers of worm eggs in utero (EIU) when compared to control CS sheep. In the more resistant Canaria Hair Breed (CHB), although vaccination induced a reduction in all parasitological parameters analysed, differences between vaccinated and control sheep were not statistically significant. Such interactions between sheep breed and vaccination may allow better integrated control of GIN in future.

Evaluation of vaccine delivery systems for inducing long-lived antibody responses to Dermanyssus gallinae antigen in laying hens.

Dermanyssus gallinae, the poultry red mite, is a global threat to the commercial egg-laying industry. Control of D. gallinae is difficult, with only a limited number of effective pesticides and non-chemical treatments available. Here, we characterize the candidate vaccine antigen D. gallinae cathepsin D-1 (Dg-CatD-1) and demonstrate that purified refolded recombinant Dg-Cat-D1 (rDg-CatD-1) is an active aspartyl proteinase which digests haemoglobin with a pH optimum of pH 4. Soluble protein extracts from D. gallinae also have haemoglobinase activity, with a pH optimum comparable to the recombinant protein, and both proteinase activities were inhibited by the aspartyl proteinase inhibitor Pepstatin A. Enzyme activity and the ubiquitous localization of Dg-CatD-1 protein in sections of adult female mites is consistent with Dg-CatD-1 being a lysosomal proteinase. Using Dg-CatD-1 as a model vaccine antigen, we compared vaccine delivery methods in laying hens via vaccination with: (i) purified rDg-CatD-1 with Montanide™ ISA 71 VG adjuvant; (ii) recombinant DNA vaccines for expression of rDg-CatD-1 and (iii) transgenic coccidial parasite Eimeria tenella expressing rDg-CatD-1. In two independent trials, only birds vaccinated with rDg-CatD-1 with Montanide™ ISA 71 VG produced a strong and long-lasting serum anti-rDg-Cat-D1 IgY response, which was significantly higher than that in control birds vaccinated with adjuvant only. Furthermore, we showed that egg-laying rates of D. gallinae mites fed on birds vaccinated with rDg-CatD-1 in Montanide™ ISA 71 VG was reduced significantly compared with mites fed on unvaccinated birds. RESEARCH HIGHLIGHTS Dermanyssus gallinae cathepsin D-1 (Dg-CatD-1) digests haemoglobin Vaccination of hens with rDg-CatD-1 in Montanide™ ISA 71 VG results in long-lasting IgY levels Serum anti-rDg-CatD-1 antibodies reduce egg laying in D. gallinae after a single blood meal.

Gene silencing by RNA interference in the ectoparasitic mite, Psoroptes ovis.

The presence of components of the RNA interference (RNAi) pathway in Psoroptes ovis, an ectoparasitic mite responsible for psoroptic mange, was investigated through interrogation of the P. ovis genome. Homologues of transcripts representing critical elements for achieving effective RNAi in the mite, Tetranychus urticae and the model organisms Caenorhabditis elegans and Drosophila melanogaster were identified and, following the development of a non-invasive immersion method of double stranded RNA delivery, gene silencing by RNAi was successfully demonstrated in P. ovis. Significant reductions in transcript levels were achieved for three target genes which encode the Group 2 allergen (Pso o 2), mu-class glutathione S-transferase (PoGST-mu1) and beta-tubulin (Poßtub). This is the first demonstration of RNAi in P. ovis and provides a mechanism for mining transcriptomic and genomic datasets for novel control targets against this economically important ectoparasite.

A recombinant subunit vaccine for the control of ovine psoroptic mange (sheep scab).

Sheep scab, caused by infestation with the mite Psoroptes ovis, is highly contagious, causing intense pruritus and represents a major welfare and economic concern. Disease control strategies rely upon chemotherapy, however, sustainability is questionable due to issues of chemical residues, eco-toxicity and acaricide resistance. Control by vaccination is supported by demonstration of protective immunity in sheep previously infested with P. ovis. We identified vaccine candidates for P. ovis based on: (1) antigens selected by their interaction with host signalling pathways and the host immune-response; and (2) those shown to be either immunogenic or involved in mite feeding. This resulted in the development and validation, in repeated immunisation and challenge trials, of a seven recombinant protein sub-unit cocktail vaccine. Sheep were inoculated on three occasions, 2 weeks apart, along with QuilA adjuvant. Vaccination resulted in highly significant reductions in both lesion size (up to 63%) and mite numbers (up to 56%) following challenge. Mean lesion size in vaccinates was significantly smaller than controls from 1 week post infestation (wpi) until the end of the experiment at 6 wpi. All antigens elicited serum IgG responses following immunisation and prior to infestation, whereas controls did not produce antigen-specific IgG during the pre-infestation period. Vaccinated animals showed an amnestic response, with levels of antigen-specific IgG against muGST, Pso o 1 and Pso o 2 increasing following infestation. This vaccine represents the greatest reduction in lesion size to date with a sheep scab vaccine, providing encouragement for future production of a commercially-viable means of immunoprophylaxis.

Integrating immune mechanisms to model nematode worm burden: an example in sheep.

Gastrointestinal nematodes represent important sources of economic losses in farmed ruminants, and the increasing frequency of anthelmintic resistance requires an increased ability to explore alternative strategies. Theoretical approaches at the crossroads of immunology and epidemiology are valuable tools in that context. In the case of Teladorsagia circumcincta in sheep, the immunological mechanisms important for resistance are increasingly well-characterized. However, despite the existence of a wide range of theoretical models, there is no framework integrating the characteristic features of this immune response into a tractable phenomenological model. Here, we propose to bridge that gap by developing a flexible modelling framework that allows for variability in nematode larval intake which can be used to track the variations in worm burdens. We parameterize this model using data from trickle infection of sheep and show that using simple immunological assumptions, our model can capture the dynamics of both adult worm burdens and nematode fecal egg counts. In addition, our analysis reveals interesting dose-dependent effects on the immune response. Finally, we discuss potential developments of this model and highlight how an improved cross-talk between empiricists and theoreticians would facilitate important advances in the study of infectious diseases.

Development of a recombinant protein-based ELISA for diagnosis of larval cyathostomin infection.

Cyathostomins are ubiquitous nematodes of horses. Once ingested, they can spend a substantial time as encysted larvae in the intestinal wall. The larvae can comprise up to 90% of the total burden, with up to several million worms reported in individuals. These stages can emerge in large numbers to cause life-threatening colitis. Direct methods for detection of encysted larval burdens in live horses do not exist. Previously, two antigen complexes were identified as promising markers for infection. A component of these, cyathostomin gut associated larval antigen-1 (Cy-GALA-1), was identified following immunoscreening of a complementary DNA library. Serum immunoglobulin G(T) (IgG(T)) responses to Cy-GALA-1 were shown to inform on larval infection. Sequence analysis of polymerase chain reaction products amplified from individual worms indicated that Cy-GALA-1 was derived from Cyathostomum pateratum. As cyathostomin infections always comprise multiple species, a diagnostic test must account for this. Here, segments of the Cy-gala gene were isolated from four common species, Cyathostomum catinatum, Cylicocyclus ashworthi, Cylicostephanus goldi and Cylicostephanus longibursatus, and the associated proteins expressed in recombinant form. The specificity and immunogenicity of each protein was confirmed. Each protein was assessed by enzyme linked immuno sorbent assay (ELISA) for its ability for informing on the presence of encysted larval infection and the level of burden.

Gene silencing by RNA interference in the house dust mite, Dermatophagoides pteronyssinus.

This is the first report of gene silencing by RNA interference (RNAi) in the European house dust mite, Dermatophagoides pteronyssinus, Trouessart, 1897. Using a non-invasive immersion method first developed for the honey bee mite, Varroa destructor, a significant reduction in the expression of D. pteronyssinus glutathione-S-transferase mu-class 1 enzyme (DpGST-mu1) was achieved following overnight immersion in double stranded RNA encoding DpGST-mu1. Although no detrimental phenotypic changes were observed following silencing, this technique can now be used to address fundamental physiological questions and assess the potential therapeutic benefit in silencing D. pteronyssinus target genes in selected domestic situations of high human-mite interface.

Comparative proteomic analysis of different Toxoplasma gondii genotypes by two-dimensional fluorescence difference gel electrophoresis combined with mass spectrometry.

Toxoplasma gondii is a protozoan parasite infecting almost all warm-blooded animals and humans. There are three infective stages of T. gondii: the tachyzoites, the bradyzoites, and the oocysts. The tachyzoite is a rapidly multiplying stage and the main pathogenic factor. In North America and Europe, T. gondii is consisted of four major clonal lineages (namely Types I, II, III, and Type 12). In this study, we explored the proteomic profiles of different genotypes (Type I-RH strain, Type II-PRU strain, Type II-TgQHO strain, and ToxoDB 9-TgC7 strain) of T. gondii tachyzoites by using 2D DIGE combined with MALDI-TOF MS. Totally, 110 differentially abundant protein spots were selected. Of these, 98 spots corresponding to 56 proteins from T. gondii were successfully identified. These included surface antigen (SAG1), heat shock protein 70 (Hsp 70), disulfide isomerase, coronin, heat shock protein 60 (Hsp 60), pyruvate kinase, receptor for activated C kinase 1, and peroxiredoxin. Gene ontology enrichment analysis revealed that most of the differentially abundant proteins were involved in biological regulation, metabolic process, response to stress, binding, antioxidant activity, and transporter activity. According to the KEGG metabolic pathway maps of T. gondii, some identified proteins were involved in the glycolytic/gluconeogenesis pathway. The present study identified differentially abundant proteins among different genotypes of T. gondii and these findings have implications for the better understanding of the phenotypic differences among the examined T. gondii genotypes, which in turn may contribute to the better control of toxoplasmosis.

A curated multivariate approach to study efficacy and optimisation of a prototype vaccine against teladorsagiasis in sheep.

This work discusses and demonstrates the novel use of multivariate analysis and data dimensionality reduction techniques to handle the variety and complexity of data generated in efficacy trials for the development of a prototype vaccine to protect sheep against the Teladorsagia circumcincta nematode. A curated collection of data dimension reduction and visualisation techniques, in conjunction with sensible statistical modelling and testing which explicitly model key features of the data, offers a synthetic view of the relationships between the multiple biological parameters measured. New biological insight is gained into the patterns and associations involving antigen-specific antibody levels, antibody avidity and parasitological parameters of efficacy that is not achievable by standard statistical practice in the field. This approach can therefore be used to guide vaccine refinement and simplification through identifying the most immunologically relevant antigens, and it can be analogously implemented for similar studies in other areas. To facilitate this, the associated data and computer codes written for the R open system for statistical computing are made freely available.

Characterisation of protective vaccine antigens from the thiol-containing components of excretory/secretory material of Ostertagia ostertagi.

Previous vaccination trials have demonstrated that thiol proteins affinity purified from Ostertagia ostertagi excretory-secretory products (O. ostertagi ES-thiol) are protective against homologous challenge. Here we have shown that protection induced by this vaccine was consistent across four independent vaccine-challenge experiments. Protection is associated with reduced cumulative faecal egg counts across the duration of the trials, relative to control animals. To better understand the diversity of antigens in O. ostertagi ES-thiol we used high-resolution shotgun proteomics to identify 490 unique proteins in the vaccine preparation. The most numerous ES-thiol proteins, with 91 proteins identified, belong to the sperm-coating protein/Tpx/antigen 5/pathogenesis-related protein 1 (SCP/TAPS) family. This family includes previously identified O. ostertagi vaccine antigens O. ostertagi ASP-1 and ASP-2. The ES-thiol fraction also has numerous proteinases, representing three distinct classes, including: metallo-; aspartyl- and cysteine proteinases. In terms of number of family members, the M12 astacin-like metalloproteinases, with 33 proteins, are the most abundant proteinase family in O. ostertagi ES-thiol. The O. ostertagi ES-thiol proteome provides a comprehensive database of proteins present in this vaccine preparation and will guide future vaccine antigen discovery projects.

Structural and functional analyses of nematode-derived antimicrobial peptides support the occurrence of direct mechanisms of worm-microbiota interactions.

The complex relationships between gastrointestinal (GI) nematodes and the host gut microbiota have been implicated in key aspects of helminth disease and infection outcomes. Nevertheless, the direct and indirect mechanisms governing these interactions are, thus far, largely unknown. In this proof-of-concept study, we demonstrate that the excretory-secretory products (ESPs) and extracellular vesicles (EVs) of key GI nematodes contain peptides that, when recombinantly expressed, exert antimicrobial activity in vitro against Bacillus subtilis. In particular, using time-lapse microfluidics microscopy, we demonstrate that exposure of B. subtilis to a recombinant saposin-domain containing peptide from the 'brown stomach worm', Teladorsagia circumcincta, and a metridin-like ShK toxin from the 'barber's pole worm', Haemonchus contortus, results in cell lysis and significantly reduced growth rates. Data from this study support the hypothesis that GI nematodes may modulate the composition of the vertebrate gut microbiota directly via the secretion of antimicrobial peptides, and pave the way for future investigations aimed at deciphering the impact of such changes on the pathophysiology of GI helminth infection and disease.

Salmon lice (Lepeophtheirus salmonis) showing varying emamectin benzoate susceptibilities differ in neuronal acetylcholine receptor and GABA-gated chloride channel mRNA expression.

BACKGROUND: Caligid copepods, also called sea lice, are fish ectoparasites, some species of which cause significant problems in the mariculture of salmon, where the annual cost of infection is in excess of €300 million globally. At present, caligid control on farms is mainly achieved using medicinal treatments. However, the continued use of a restricted number of medicine actives potentially favours the development of drug resistance. Here, we report transcriptional changes in a laboratory strain of the caligid Lepeophtheirus salmonis (Krøyer, 1837) that is moderately (~7-fold) resistant to the avermectin compound emamectin benzoate (EMB), a component of the anti-salmon louse agent SLICE® (Merck Animal Health). RESULTS: Suppression subtractive hybridisation (SSH) was used to enrich transcripts differentially expressed between EMB-resistant (PT) and drug-susceptible (S) laboratory strains of L. salmonis. SSH libraries were subjected to 454 sequencing. Further L. salmonis transcript sequences were available as expressed sequence tags (EST) from GenBank. Contiguous sequences were generated from both SSH and EST sequences and annotated. Transcriptional responses in PT and S salmon lice were investigated using custom 15 K oligonucleotide microarrays designed using the above sequence resources. In the absence of EMB exposure, 359 targets differed in transcript abundance between the two strains, these genes being enriched for functions such as calcium ion binding, chitin metabolism and muscle structure. γ-aminobutyric acid (GABA)-gated chloride channel (GABA-Cl) and neuronal acetylcholine receptor (nAChR) subunits showed significantly lower transcript levels in PT lice compared to S lice. Using RT-qPCR, the decrease in mRNA levels was estimated at ~1.4-fold for GABA-Cl and ~2.8-fold for nAChR. Salmon lice from the PT strain showed few transcriptional responses following acute exposure (1 or 3 h) to 200 µg L-1 of EMB, a drug concentration tolerated by PT lice, but toxic for S lice. CONCLUSIONS: Avermectins are believed to exert their toxicity to invertebrates through interaction with glutamate-gated and GABA-gated chloride channels. Further potential drug targets include other Cys-loop ion channels such as nAChR. The present study demonstrates decreased transcript abundances of GABA-Cl and nAChR subunits in EMB-resistant salmon lice, suggesting their involvement in avermectin toxicity in caligids.

Two major ruminant acute phase proteins, haptoglobin and serum amyloid A, as serum biomarkers during active sheep scab infestation.

Two ruminant acute phase proteins (APPs), haptoglobin (Hp) and serum amyloid A (SAA), were evaluated as serum biomarkers (BMs) for sheep scab-a highly contagious ectoparasitic disease caused by the mite Psoroptes ovis, which is a major welfare and production threat worldwide. The levels of both APPs increased in serum following experimental infestation of sheep with P. ovis, becoming statistically significantly elevated from pre-infestation levels at 4 weeks post-infestation. Following successful treatment of infested sheep with an endectocide, Hp and SAA serum levels declined rapidly, with half lives of less than 3 days. In contrast, serum IgG levels which specifically bound the P. ovis-derived diagnostic antigen Pso o 2 had a half-life of 56 days. Taking into account pre-infestation serum levels, rapidity of response to infestation and test sensitivity at the estimated optimum cut-off values, SAA was the more discriminatory marker. These studies illustrated the potential of SAA and Hp to indicate current sheep scab infestation status and to augment the existing Pso o 2 serological assay to give disease-specific indications of both infestation and successful treatment.

The effect of Psoroptes ovis infestation on ovine epidermal barrier function.

Sheep scab is an intensively pruritic, exudative and allergic dermatitis of sheep caused by the ectoparasitic mite Psoroptes ovis. The purpose of the present study was to investigate the effect of P. ovis infestation on different components of the ovine epidermal barrier within the first 24 hours post-infestation (hpi). To achieve this, the expression of epidermal differentiation complex (EDC) genes and epidermal barrier proteins, the nature and severity of epidermal pathology and transepidermal water loss (TEWL) were evaluated.By 1 hpi a significant dermal polymorphonuclear infiltrate and a significant increase in TEWL with maximal mean TEWL (598.67 g/m2h) were observed. Epidermal pathology involving intra-epidermal pustulation, loss of epidermal architecture and damage to the basement membrane was seen by 3 hpi. Filaggrin and loricrin protein levels in the stratum corneum declined significantly in the first 24 hpi and qPCR validation confirmed the decrease in expression of the key EDC genes involucrin, filaggrin and loricrin observed by microarray analysis, with 5.8-fold, 4.5-fold and 80-fold decreases, respectively by 24 hpi.The present study has demonstrated that early P. ovis infestation disrupts the ovine epidermal barrier causing significant alterations in the expression of critical barrier components, epidermal pathology, and TEWL. Many of these features have also been documented in human and canine atopic dermatitis suggesting that sheep scab may provide a model for the elucidation of events occurring in the early phases of atopic sensitisation.

Suppression of ovine lymphocyte activation by Teladorsagia circumcincta larval excretory-secretory products.

Teladorsagia circumcincta is an important pathogenic nematode of sheep. It has been demonstrated previously that stimulation of murine T lymphocytes with excretory-secretory (ES) products derived from fourth stage larvae of T. circumcincta (Tci-L4-ES) results in de novo expression of Foxp3, a transcription factor intimately involved in regulatory T cell function. In the current study, Foxp3⁺ T cell responses in the abomasum and the effects of Tci-L4-ES on ovine peripheral blood mononuclear cells (PBMC) following T. circumcincta infection were investigated. T. circumcincta infection resulted in a significant increase in numbers of abomasal Foxp3⁺ T cells, but not an increase in the proportion of T cells expressing Foxp3. Unlike in mice, Tci-L4-ES was incapable of inducing T cell Foxp3 expression but instead suppressed mitogen-induced and antigen-specific activation and proliferation of ovine PBMC in vitro. This effect was heat labile, suggesting that it is mediated by protein(s). Suppression was associated with up-regulation of interleukin-10 (IL-10) mRNA, and specific monoclonal antibody neutralisation of IL-10 resulted in a 50% reduction in suppression, indicating involvement of the IL-10 signaling pathway. Suppression was significantly reduced in PBMC isolated from T. circumcincta infected vs. helminth-naïve lambs, and this reduction in suppression was associated with an increase in Tci-L4-ES antigen-specific T cells within the PBMC. In conclusion, we have identified a mechanism by which T. circumcincta may modulate the host adaptive immune response, potentially assisting survival of the parasite within the host. However, the impact of Tci-L4-ES-mediated lymphocyte suppression during T. circumcincta infection remains to be determined.

Characterization of the ovine complement 4 binding protein-beta (C4BPB) chain as a serum biomarker for enhanced diagnosis of sheep scab.

Sheep scab, caused by the highly contagious mite Psoroptes ovis, is endemic in a number of sheep-producing countries worldwide, and is a major animal welfare and economic concern. Recent developments in the diagnosis of sheep scab include a highly sensitive and specific serum antibody-based assay which can be used to indicate exposure to the parasite but not necessarily current disease status. Here, a transcriptomic and bioinformatics analysis of the circulating leukocytes of sheep with active P. ovis infestation indicated that the transcription levels of complement 4 binding protein beta (C4BPB) increased by 12 fold from pre-infestation to 6 weeks post-infestation. Semi-quantitative studies confirmed increased serum C4BPB protein levels in sheep infested with P. ovis. To quantify this serum protein response and characterize ovine C4BPB as a biomarker for active P. ovis infestation, the ovine C4BPB gene was sequenced, a recombinant protein expressed, antibodies against this protein were raised in rabbits and a sandwich ELISA developed. The results from this assay indicated that serum C4BPB protein levels increased 4-fold from pre-infestation to 6 weeks post-infestation, which demonstrated the potential of the assay to quantify C4BPB in sheep sera and indicated the potential of C4BPB as a biomarker of current disease status in sheep post-infestation and post-treatment.