Characterisation of tropomyosin and paramyosin as vaccine candidate molecules for the poultry red mite, Dermanyssus gallinae

In Vivo Characterization of the Anti-Glutathione S-Transferase Antibody Using an In Vitro Mite Feeding Model

Poultry red mites (Dermanyssus gallinae, PRMs), tropical fowl mites (Ornithonyssus bursa, TFMs), and northern fowl mites (O. sylviarum, NFMs) are blood-feeding pests that debilitate poultry worldwide. Glutathione S-transferase (GST) plays an important role in the detoxification and drug metabolism of mites. However, research on avian mite GSTs as vaccine antigens is still lacking. Therefore, we aimed to evaluate the potential of avian mite GSTs for vaccine development. We identified GST genes from TFMs and NFMs. We prepared recombinant GST (rGST) from TFMs, NFMs, and PRMs, and assessed their protein functions. Moreover, we evaluated the cross-reactivity and acaricidal effect of immune plasma against each rGST on TFMs, NFMs, and PRMs. The deduced amino acid sequences of GSTs from TFMs and NFMs were 80% similar to those of the PRMs. The rGSTs exhibited catalytic activity in conjugating glutathione to the 1-chloro-2,4-dinitrobenzene substrate. Immune plasma against each rGST showed cross-reactivity with rGST from different mite species. Moreover, the survival rate of PRMs fed with immune plasma against the rGST of TFMs and NFMs was significantly lower than that of the control plasma. These results demonstrate the potential application of GST as an antigen for the development of a broad-spectrum vaccine against avian mites.

Advances in Non-Chemical Tools to Control Poultry Hematophagous Mites

The blood-sucking mites Dermanyssus gallinae ("red mite"), Ornithonyssus sylviarum ("northern fowl mite"), and Ornithonyssus bursa ("tropical fowl mite") stand out for causing infestations in commercial poultry farms worldwide, resulting in significant economic damage for producers. In addition to changes in production systems that include new concerns for animal welfare, global climate change in recent years has become a major challenge in the spread of ectoparasites around the world. This review includes information regarding the main form of controlling poultry mites through the use of commercially available chemicals. In addition, non-chemical measures against blood-sucking mites were discussed such as extracts and oils from plants and seeds, entomopathogenic fungi, semiochemicals, powder such as diatomaceous earth and silica-based products, and vaccine candidates. The control of poultry mites using chemical methods that are currently used to control or eliminate them are proving to be less effective as mites develop resistance. In contrast, the products based on plant oils and extracts, powders of plant origin, fungi, and new antigens aimed at developing transmission-blocking vaccines against poultry mites provide some encouraging options for the rational control of these ectoparasites.

Characterization of cysteine proteases from poultry red mite, tropical fowl mite, and northern fowl mite to assess the feasibility of developing a broadly efficacious vaccine against multiple mite species

Infestation with poultry red mites (PRM, Dermanyssus gallinae) causes anemia, reduced egg production, and death in serious cases, resulting in significant economic losses to the poultry industry. As a novel strategy for controlling PRMs, vaccine approaches have been focused upon and several candidate vaccine antigens against PRMs have been reported. Tropical (TFM, Ornithonyssus bursa) and northern (NFM, Ornithonyssus sylviarum) fowl mites are also hematophagous and cause poultry industry problems similar to those caused by PRM. Therefore, ideal antigens for anti-PRM vaccines are molecules that cross-react with TFMs and NFMs, producing pesticidal effects similar to those against PRMs. In this study, to investigate the potential feasibility of developing vaccines with broad efficacy across mite species, we identified and characterized cysteine proteases (CPs) of TFMs and NFMs, which were previously reported to be effective vaccine antigens of PRMs. The open reading frames of CPs from TFMs and NFMs had the same sequences, which was 73.0% similar to that of PRMs. Phylogenetic analysis revealed that the CPs of TFMs and NFMs clustered in the same clade as CPs of PRMs. To assess protein functionality, we generated recombinant peptidase domains of CPs (rCP-PDs), revealing all rCP-PDs showed CP-like activities. Importantly, the plasma obtained from chickens immunized with each rCP-PD cross-reacted with rCP-PDs of different mites. Finally, all immune plasma of rCP-PDs reduced the survival rate of PRMs, even when the plasma was collected from chickens immunized with rCP-PDs derived from TFM and NFM. Therefore, CP antigen is a promising, broadly efficacious vaccine candidate against different avian mites.

Potential of ferritin 2 as an antigen for the development of a universal vaccine for avian mites, poultry red mites, tropical fowl mites, and northern fowl mites

Introduction

Poultry red mites (PRMs, Dermanyssus gallinae), blood-sucking ectoparasites, are a threat to the poultry industry because of reduced production caused by infestation. In addition, tropical fowl mites (TFMs, Ornithonyssus bursa) and northern fowl mites (NFMs, Ornithonyssus sylviarum) are hematophagous, distributed in various regions, genetically and morphologically close to PRMs, and cause similar problems to the poultry industry. Vaccine approaches have been studied for PRM control, and several molecules have been identified in PRMs as candidates for effective vaccine antigens. The development of an anti-PRM vaccine as a universal vaccine with broad efficacy against avian mites could improve the productivity of poultry farms worldwide. Molecules that are highly conserved among avian mites and have critical functions in the physiology and growth of mites could be ideal antigen candidates for the development of universal vaccines. Ferritin 2 (FER2), an iron-binding protein, is critical for the reproduction and survival of PRMs and has been reported as a useful vaccine antigen for the control of PRMs and a candidate for the universal vaccine antigen in some tick species.

Method and results

Herein, we identified and characterized FER2 in TFMs and NFM. Compared with the sequence of PRM, the ferroxidase centers of the heavy chain subunits were conserved in FER2 of TFMs and NFMs. Phylogenetic analysis revealed that FER2 belongs to clusters of secretory ferritins of mites and other arthropods. Recombinant FER2 (rFER2) proteins from PRMs, TFMs, and NFMs exhibited iron-binding abilities. Immunization with each rFER2 induced strong antibody responses in chickens, and each immune plasma cross-reacted with rFER2 from different mites. Moreover, mortality rates of PRMs fed with immune plasma against rFER2 from TFMs or NFMs, in addition to PRMs, were higher than those of control plasma.

Discussion

rFER2 from each avian mite exhibited anti-PRM effects. This data suggests that it has the potential to be used as an antigen candidate for a universal vaccine against avian mites. Further studies are needed to access the usefulness of FER2 as a universal vaccine for the control of avian mites.

Poultry Mites: Ubiquitous, Spreading, and Still a Growing Threat

Poultry mites continue to be a major threat to poultry meat and egg production all over the world, with some species being blood-feeding arthropods that spend most of their time off-host and others burrowing under the bird's skin. Regardless of feeding strategy, these mites create welfare issues and production losses in poultry production systems in terms of bird growth, egg quality, and egg quantity. Furthermore, some species are able to transmit pathogens, introducing secondary infections that affect the birds' development and survival. Because of national restrictions on acaricide use and the development of mite resistance to available control products, the eradication of poultry mites is far from being achieved. However, new drugs and a better understanding of mite genetic and transcriptomic factors should aid the development of new control and treatment strategies. This review focuses on the main poultry mite species, their significance, and their current and future control.

Two ferritins from Dermanyssus gallinae: characterization and in vivo assessment as protective antigens

BACKGROUND

The poultry red mite, Dermanyssus gallinae is recognized worldwide as the most important bloodsucking ectoparasite in layer and breeder flocks. In bloodsucking ectoparasites, ferritins (FERs), the iron-storage proteins, play a pivotal role in dealing with the challenge of large amounts of released iron during the digestion of blood meal. However, no information is available concerning FERs of D. gallinae. The aim of the present study was to investigate the characteristics, functions and the vaccine efficacy of FERs in D. gallinae.

RESULTS

Two heavy-chain FERs of D. gallinae were identified and characterized. Phylogenetic analysis indicated that Dg-FER1 may be a secretory FER and Dg-FER2 an intracellular one. RNAi results demonstrated that Dg-fers play key roles in mite survival, successful reproduction and blood digestion. Immunization with rDg-FER1 or rDg-FER2 successfully induced chickens to produce high levels of antigen-specific IgY, resulting in a significant increase in mite mortality (by 58.67% on Day 5) and decreases in oviposition (by 42.15%) and fecundity (by 68.97%) in the rDg-FER1 group, and a 13.73% increase in mite mortality and a 20.89% decrease in fecundity in the rDg-FER1 group. The overall immunization efficacy of rDg-FER1 was 93.51%.

CONCLUSION

Two Dg-FERs are crucial to the survival, reproduction and blood digestion of D. gallinae. This study has provided preliminary evidence demonstrating the potential of rDg-FER1 as a vaccine antigen for D. gallinae. © 2021 Society of Chemical Industry.

Characterization of a Novel Cysteine Protease Inhibitor from Poultry Red Mites: Potential Vaccine for Chickens

Poultry red mite (PRM; Dermanyssus gallinae) is a hazardous, blood-sucking ectoparasite of birds that constitutes a threat to poultry farming worldwide. Acaricides, commonly used in poultry farms to prevent PRMs, are not effective because of the rapid emergence of acaricide-resistant PRMs. However, vaccination may be a promising strategy to control PRM. We identified a novel cystatin-like molecule in PRMs: Dg-Cys. Dg-Cys mRNA expression was detected in the midgut and ovaries, in all stages of life. The PRM nymphs that were artificially fed with the plasma from chickens that were immunized with Dg-Cys in vitro had a significantly reduced reproductive capacity and survival rate. Moreover, combination of Dg-Cys with other antigen candidates, like copper transporter 1 or adipocyte plasma membrane-associated protein, enhanced vaccine efficacies. vaccination and its application as an antigen for cocktail vaccines could be an effective strategy to reduce the damage caused by PRMs in poultry farming.

In vitro evaluation of a cysteine protease from poultry red mites, Demanyssus gallinae, as a vaccine antigen for chickens

Poultry red mites (PRMs, Dermanyssus gallinae) are hematophagous ectoparasites that negatively affect egg production, which causes serious economic losses to the poultry industry worldwide. Currently, the emergence of acaricide-resistant PRMs has impeded PRM control in poultry farms. Several alternatives for acaricide use have been described for managing PRM-caused problems. Vaccination is among the methods for controlling PRMs in poultry houses. Currently, several candidates for vaccine antigens have been identified. This study identified a cysteine protease, Deg-CPR-2, which differs from 2 other previously reported cysteine proteases in PRMs, from previously obtained data from RNA-sequencing (RNA-seq) analysis. We investigated the characteristics of Deg-CPR-2 and assessed its efficacy as a vaccine antigen in vitro. Phylogenetic analysis revealed that Deg-CPR-2 belonged to a different cluster from those of other cysteine proteases in PRMs. This cluster also included cathepsin L-like proteases, enzymes thought to be involved in hemoglobin digestion in ticks. Expression analysis revealed Deg-CPR-2 expression in midguts and all the life-stages; however, there were differences in the expression levels across the life-stages. The enzyme activity of recombinant Deg-CPR-2 was inhibited in the presence of a cysteine protease inhibitor, which suggests that Deg-CPR-2 functions as a cysteine protease in PRMs. Finally, there was an in vitro increase in the mortality of PRMs, mainly protonymphs that were artificially fed with plasma from chickens immunized with Deg-CPR-2. These findings suggest that Deg-CPR-2 may contribute to protein digestion in the midgut of PRMs and is crucially involved in physiological processes in PRMs. Additionally, immunization with Deg-CPR-2 may reduce the number of protonymphs, and Deg-CPR-2 should be considered as a candidate antigen for anti-PRM vaccine development.

Introducing a new anti-Rhipicephalus (Boophilus) microplus tick recombinant vaccine candidate using cathepsin and tropomyosin multi-epitope gene

Rhipicephalus (Boophilus) spp. are important vectors for Babesia and Anaplasma species causing severe economic losses in livestock. Chemical compounds are commonly used to control tick infestation; however, acaricides resistance in tick has led to move toward alternative strategies such as vaccination. In this study, we introduced a vaccine candidate, namely CaTro against Rh. microplus tick composing of immunogenic B-cell epitopes derived from Rh. microplus cathepsin L and tropomyosin proteins. To evaluate this vaccine candidate, firstly the CaTro sequence was inserted into the prokaryotic expression vector and the recombinant protein CaTro was expressed in Bl21 bacteria. Afterward, purification was performed by Ni-NTA affinity chromatography. The quality of purified recombinant CaTro was also analyzed using sodium dodecyl sulfate-gel electrophoresis and western blotting. Moreover, to evaluate the induction of immune response, the rabbits were immunized with purified recombinant protein combined with Freund's adjuvant. The findings of this study revealed molecular weight of expressed protein (CaTro) as 38.00 kDa. Furthermore, anti-CaTro antibody was detected in immunized rabbit's sera through dot blotting; while, there was not any response to the control rabbit's sera. The results suggest that CaTro is a potential candidate to develop an anti- Rh. microplus tick.

In vitro characterization of adipocyte plasma membrane-associated protein from poultry red mites, Dermanyssus gallinae, as a vaccine antigen for chickens

The poultry red mite (Dermanyssus gallinae; PRM) is a blood-sucking ectoparasite of chickens that is a threat to poultry farming worldwide and significantly reduces productivity in the egg-laying industry. Chemical acaricides that are widely used in poultry farms for the prevention of PRMs are frequently ineffective due to the emergence of acaricide-resistant PRMs. Therefore, alternative control methods are needed, and vaccination is a promising strategy for controlling PRMs. A novel adipocyte-plasma membrane-associated protein-like molecule (Dg-APMAP) is highly expressed in blood-fed PRMs according to a previous RNA sequencing analysis. Here, we attempted to identify the full sequence of Dg-APMAP, study its expression in different life stages of PRMs, and evaluate its potential as a vaccine antigen. Dg-APMAP mRNA was expressed in the midgut and ovaries, and in all life stages regardless of feeding states. Importantly, in vitro feeding of PRMs with plasma derived from chickens immunized with the recombinant protein of the extracellular region of Dg-APMAP significantly reduced their survival rate in nymphs and adults, which require blood meals. Our data suggest that the host immune responses induced by vaccination with Dg-APMAP could be an effective strategy to reduce the suffering caused by PRMs in the poultry industry.

Characterization of a copper transporter 1 from Dermanyssus gallinae as a vaccine antigen

Poultry red mites (Dermanyssus gallinae, PRM) are dangerous ectoparasites that infest chickens and threaten the poultry industry worldwide. PRMs usually develop resistance to chemical acaricides, necessitating the development of more effective preventive agents, and vaccination could be an alternative strategy for controlling PRMs. The suitability of plasma membrane proteins expressed in the midguts as vaccine antigens was evaluated because these molecules are exposed to antibodies in the ingested blood and the binding of antibodies could potentially induce direct damage to midgut tissue and indirect damage via inhibition of the functions of target molecules. Therefore, in the present study, a copper transporter 1-like molecule (Dg-Ctr1) was identified and its efficacy as a vaccine antigen was assessed in vitro. Dg-Ctr1 mRNA was expressed in the midguts and ovaries and in all the life stages, and flow cytometric analysis indicated that Dg-Ctr1 was expressed on the plasma membrane. Importantly, nymphs fed on plasma derived from chickens immunized with the recombinant protein of the extracellular region of Dg-Ctr1 showed a significant reduction in the survival rate. These data indicate that the application of Dg-Ctr1 as a vaccine antigen could reduce the number of nymphs in the farms, contributing to reduction in the economic losses caused by PRMs in the poultry industry. To establish an effective vaccination strategy, the acaricidal effects of the combined use of Dg-Ctr1 with chemical acaricides or other vaccine antigens must be examined.

Identification and Amino Acid Analysis of Allergenic Epitopes of a Novel Allergen Paramyosin (Rap v 2) from Rapana venosa

Besides tropomyosin (TM) that is widely recognized as a major allergen in molluscs, a 99-kDa novel allergen (Rap v 2) was recently found in the sea snail Rapana venosa and identified as paramyosin (PM). However, the allergenic epitopes of PM in any molluscs have not been identified yet. In the present study, seven allergenic epitopes of Rap v 2 were identified by immunoinformatics tools, dot-blot inhibition assay, and basophil degranulation assay. Based on the analysis of PM and allergenic epitope amino acids, it was found that highly hydrophobic and positively charged amino acid residues play an important role in the formation of Rap v 2 epitopes. In addition, three potential critical amino acids that may account for TM and PM cross-reactivity in molluscs were found by sequence- and structure-based methods. These findings could be of major importance for improving the understanding of relevant paramyosin epitopes and the prevention and therapy of mollusc allergy.

Characterisation of a cysteine protease from poultry red mites and its potential use as a vaccine for chickens

Poultry red mites (PRMs, Dermanyssus gallinae) are ectoparasites that negatively affect farmed chickens, leading to serious economic losses worldwide. Acaricides have been used to control PRMs in poultry houses. However, some PRMs have developed resistance to acaricides, and therefore different approaches are required to manage the problems caused by PRMs. Vaccination of chickens is one of the methods being considered to reduce the number of PRMs in poultry houses. In a previous study, a cysteine protease, Deg-CPR-1, was identified as a candidate vaccine against PRMs distributed in Europe. In this study, we investigated the characteristics of Deg-CPR-1. A phylogenetic analysis revealed that Deg-CPR-1 is closely related to the digestive cysteine proteases of other mite species, and it was classified into a cluster different from that of chicken cathepsins. Deg-CPR-1 of PRMs in Japan has an amino acid substitution compared with that of PRMs in Europe, but it showed efficacy as a vaccine, consistent with previous findings. Deg-CPR-1 exhibited cathepsin L-like enzyme activity. In addition, the Deg-CPR-1 mRNA was expressed in the midgut and in all stages of PRMs that feed on blood. These results imply that Deg-CPR-1 in the midgut may have important functions in physiological processes, and the inhibition of its expression may contribute to the efficacy of a Deg-CPR-1-based vaccine. Further research is required to fully understand the mechanisms of vaccine efficacy.

Purification, Characterization, and Three-Dimensional Structure Prediction of Paramyosin, a Novel Allergen of Rapana venosa

Paramyosin (PM) is an important structural protein in molluscan muscles. However, as an important allergen, there is a little information on PM in the molluscs. In this study, a 99 kDa molecular weight allergen protein was purified from Rapana venosa and confirmed as PM by mass spectrometry. The results of immunoglobulin E (IgE)-binding activity and physicochemical characterization showed that R. venosa PM could react with a specific IgE of the sera from sea snail-allergic patients, and the IgE-binding activity could be reduced by thermal treatment. The full-length cDNA of R. venosa PM was cloned, which encodes 859 amino acid residues, and it has a higher homology among molluscan species. According to the circular dichroism results, Fourier transform infrared, and 2D and 3D structure analysis, both PM and tropomyosin are conserved proteins, which are mainly composed of the α-helix structure. These results are significant for better understanding the anaphylactic reactions in sea snail-allergic patients and allergy diagnosis.

An efficient high-welfare feeding device for assessing northern fowl mite interventions in vivo: an improved method for the identification of protective antigens/systemic acaricides/repellent effect

The northern fowl mite (NFM), Ornithonyssus sylviarum, is an obligate hematophagous ectoparasite of domestic and wild birds, and it is an economic pest of laying hen in North America, China, India, Australia, Myanmar, and Brazil. Such an economically important pest remains neglected in many parts of the world, including Asian countries. Therefore, concerted action is required in both basic and applied research directed at the biology and control of this destructive pest. In the present study, we have developed a novel, high-welfare in vivo feeding capsule that would permit pre-screening of new interventions, repellency and deterrence effects of plant-derived products and other semiochemical compounds before proceeding to large-scale field experiments/bioassays, while the minimum number of animals is required to obtain results. Mites were fed on the birds through either a mesh or without a mesh. The average feeding rates of mites was significantly higher when fed directly on chickens, whereas 106 μm nylon mesh was the top-performing mesh when compared with 125 μm aperture nylon mesh. For optimal feeding, the feeding capsules contain NFM and are attached to the skin of the chicken's thigh for 6 h. This is a simple, reproducible, and easy approach and can be adapted to facilitate many aspects of bioassays.

The evaluation of feeding, mortality and oviposition of poultry red mite ( Dermanyssus gallinae) on aging hens using a high welfare on-hen feeding device

A study was performed to examine any effect of hen age on the feeding ability and mortality of different life-stages of Dermanyssus gallinae [Poultry Red Mite (PRM)] when fed using a high welfare, on-hen mite feeding device. Mite feeding assays were carried out every two weeks on a cohort of five Lohman Brown hens with devices containing adult and deutonymph PRM or adult and protonymph PRM. Feeding rates and mortality of each PRM life stage and oviposition of adult female PRM were evaluated over an 18-week period. There was a significant reduction in oviposition rates of female PRM as they fed on hens of increasing age. However, no clear trend was detected between the feeding rates of all three haematophagous life stages and hen age. The same conclusion was reached regarding mite mortality post-feeding in both deutonymph and adult female PRMs, although a weak positive association was apparent between hen age and protonymph PRM mortality. This study shows that the on-hen feeding device can be used both for short term studies to assess novel anti-PRM products (new acaricides, vaccines etc.) and longer, longitudinal studies to determine longevity of the effects of such novel anti-PRM products. It also demonstrates that blood feeding by mites on older hens is less able to sustain PRM populations than feeding on younger hens. This on-hen mite feeding device directly impacts upon reduction and refinement by greatly reducing the numbers of birds required per experimental group compared to traditional PRM challenge infestation models and by eliminating the need for birds to be exposed to large numbers of mites for extended periods of time that can cause welfare concerns. This paper describes the methodology for these studies and how to assemble pouches and handle mites both before and after feeding assays.

De novo assembly and discovery of genes related to blood digestion in the transcriptome of Dermanyssus gallinae (Acari: Dermanyssidae)

Dermanyssus gallinae is an economically important blood-feeding ectoparasite affecting layer chicken farms in many countries. Similar to other blood-feeding arthropods, the blood-meal digestion plays a key role in the survival and reproduction of D. gallinae. The knowledge of the genes involved in blood digestion processes may provide new targets for drug and vaccine against the red mites. In the present study, we sequenced and de novo assembled the transcriptomes of unfed and fed adult red mites using Illumina RNA sequencing (RNA-seq) technology. Up to 40,506 unigenes were assembled, and 13,018 unigenes were identified and annotated. GO analysis of the annotated unigenes clustered into three main GO terms. The dominant GO terms of biological processes were cellular process and metabolic process, the prevailing GO terms of the cellular component were cell part and membrane part, and the dominant GO terms of molecular functions were catalytic and binding activities. Up to 6,443 annotated sequences were assigned to 246 active pathways by KEGG analysis. Differentially expressed genes (DEGs) analysis identified 2,877 unigenes with upregulated 2,094 and downregulated 783 in fed female mites compared with unfed female mites. The biological function of these DEGs was further investigated using the KEGG and GO databases. The upregulated DEGs were potentially involved in nutrient metabolism, highlighting their importance in red mite biology. Quantitative reverse transcription real-time PCR (qRT-PCR) validated that the expression levels of the selected six upregulated DEGs were consistent with those in RNA-seq, indicating that the transcriptomic data are reliable. The present study provides valuable and fundamental knowledge that improves our understanding of the physiology of D. gallinae digestion at a molecular level. Moreover, these transcriptomic data will facilitate the identification of novel function genes and candidate antigens for the development of effective vaccines or drug targets to control D. gallinae.

A vaccinology Approach to the Identification and Characterization of Dermanyssus Gallinae Candidate Protective Antigens for the Control of Poultry Red Mite Infestations

The poultry red mite (PRM), Dermanyssus gallinae, is a hematophagous ectoparasite considered as the major pest in the egg-laying industry. Its pesticide-based control is only partially successful and requires the development of new control interventions such as vaccines. In this study, we follow a vaccinology approach to identify PRM candidate protective antigens. Based on proteomic data from fed and unfed nymph and adult mites, we selected a novel PRM protein, calumenin (Deg-CALU), which is tested as a vaccine candidate on an on-hen trial. Rhipicephalus microplus Subolesin (Rhm-SUB) was chosen as a positive control. Deg-CALU and Rhm-SUB reduced the mite oviposition by 35 and 44%, respectively. These results support Deg-CALU and Rhm-SUB as candidate protective antigens for the PRM control.

Reduction in Oviposition of Poultry Red Mite (Dermanyssus gallinae) in Hens Vaccinated with Recombinant Akirin

The poultry red mite (PRM), Dermanyssus gallinae, is a hematophagous ectoparasite of birds with worldwide distribution that causes economic losses in the egg-production sector of the poultry industry. Traditional control methods, mainly based on acaricides, have been only partially successful, and new vaccine-based interventions are required for the control of PRM. Vaccination with insect Akirin (AKR) and its homolog in ticks, Subolesin (SUB), have shown protective efficacy for the control of ectoparasite infestations and pathogen infection/transmission. The aim of this study was the identification of the akr gene from D. gallinae (Deg-akr), the production of the recombinant Deg-AKR protein, and evaluation of its efficacy as a vaccine candidate for the control of PRM. The anti-Deg-AKR serum IgY antibodies in hen sera and egg yolk were higher in vaccinated than control animals throughout the experiment. The results demonstrated the efficacy of the vaccination with Deg-AKR for the control of PRM by reducing mite oviposition by 42% following feeding on vaccinated hens. A negative correlation between the levels of serum anti-Deg-AKR IgY and mite oviposition was obtained. These results support Deg-AKR as a candidate protective antigen for the control of PRM population growth.

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.

A novel, high-welfare methodology for evaluating poultry red mite interventions in vivo

Optimisation and use of a device for the on-hen in vivo feeding of all hematophagous stages of Dermanyssus gallinae is described. The sealed mesh device contains the mites and is applied to the skin of the hen's thigh where mites can feed on the bird through a mesh which has apertures large enough to allow the mites' mouth-parts to access to the bird but small enough to contain the mites. By optimising the depth and width of the mesh aperture size we have produced a device which will lead to both reduction and refinement in the use of animals in research, allowing the pre-screening of new vaccines and systemic acaricides/insecticides which have been developed for the control of these blood-feeding parasites before progressing to large field trials. For optimal use, the device should be constructed from 105 μm aperture width, 63 μm depth, polyester mesh and the mites (irrespective of life stage) should be conditioned with no access to food for 3 weeks at 4 °C for optimal feeding and post-feeding survival.

Spotlight on avian pathology: red mite, a serious emergent problem in layer hens

Dermanyssus gallinae, the poultry red mite, is currently the most important ectoparasite of the egg laying industry worldwide with an expanding global prevalence. As a blood-feeder, it causes anaemia and severe welfare issues to the hens and it is a major cause of economic losses. It is also a vector for Salmonella species, avian influenza and potentially for other vector-borne pathogens. Paradoxically, there is a notable lack of funding for research into poultry red mite and an urgent need for effective and safe control strategies, sustainable therapies, prophylactics and integrated pest management.

Metazoan Parasite Vaccines: Present Status and Future Prospects

Eukaryotic parasites and pathogens continue to cause some of the most detrimental and difficult to treat diseases (or disease states) in both humans and animals, while also continuously expanding into non-endemic countries. Combined with the ever growing number of reports on drug-resistance and the lack of effective treatment programs for many metazoan diseases, the impact that these organisms will have on quality of life remain a global challenge. Vaccination as an effective prophylactic treatment has been demonstrated for well over 200 years for bacterial and viral diseases. From the earliest variolation procedures to the cutting edge technologies employed today, many protective preparations have been successfully developed for use in both medical and veterinary applications. In spite of the successes of these applications in the discovery of subunit vaccines against prokaryotic pathogens, not many targets have been successfully developed into vaccines directed against metazoan parasites. With the current increase in -omics technologies and metadata for eukaryotic parasites, target discovery for vaccine development can be expedited. However, a good understanding of the host/vector/pathogen interface is needed to understand the underlying biological, biochemical and immunological components that will confer a protective response in the host animal. Therefore, systems biology is rapidly coming of age in the pursuit of effective parasite vaccines. Despite the difficulties, a number of approaches have been developed and applied to parasitic helminths and arthropods. This review will focus on key aspects of vaccine development that require attention in the battle against these metazoan parasites, as well as successes in the field of vaccine development for helminthiases and ectoparasites. Lastly, we propose future direction of applying successes in pursuit of next generation vaccines.

Bacillus subtilis spore with surface display of paramyosin from Clonorchis sinensis potentializes a promising oral vaccine candidate

Background

Clonorchiasis caused by Clonorchis sinensis has become increasingly prevalent in recent years. Effective prevention strategies are urgently needed to control this food-borne infectious disease. Previous studies indicated that paramyosin of C. sinensis (CsPmy) is a potential vaccine candidate.

Methods

We constructed a recombinant plasmid of PEB03-CotC-CsPmy, transformed it into Bacillus subtilis WB600 strain (B.s-CotC-CsPmy), and confirmed CsPmy expression on the spore surface by SDS-PAGE, Western blotting and immunofluorescence assay. The immune response and protective efficacy of the recombinant spore were investigated in BALB/c mice after intragastrical or intraperitoneal immunization. Additionally, biochemical enzyme activities in sera, the intestinal histopathology and gut microflora of spore-treated mice were investigated.

Results

CsPmy was successfully expressed on the spore surface and the fusion protein on the spore surface with thermostability. Specific IgG in sera and intestinal mucus were increased after intraperitoneal and intragastrical immunization. The sIgA level in intestinal mucus, feces and bile of B.s-CotC-CsPmy orally treated mice were also significantly raised. Furthermore, numerous IgA-secreting cells were detected in intestinal mucosa of intragastrically immunized mice. No inflammatory injury was observed in the intestinal tissues and there was no significant difference in levels of enzyme-indicated liver function among the groups. Additionally, the diversity and abundance of gut microbiota were not changed after oral immunization. Intragastric and intraperitoneal immunization of B.s-CotC-CsPmy spores in mice resulted in egg reduction rates of 48.3 and 51.2% after challenge infection, respectively. Liver fibrosis degree in B.s-CotC-CsPmy spores treated groups was also significantly reduced.

Conclusions

CsPmy expressed on the spore surface maintained its immunogenicity. Both intragastrical and intraperitoneal immunization with B.s-CotC-CsPmy spores induced systemic and local mucosal immune response in mice. Although both intragastric and intraperitoneal immunization elicited a similar protective effect, intragastric immunization induced stronger mucosal immune response without side effects to the liver, intestine and gut microbiota, compared with intraperitoneal immunization. Oral immunization with B. subtilis spore expressing CsPmy on the surface was a promising, safe and needle-free vaccination strategy against clonorchiasis.

A review of the biology, ecology, and control of the northern fowl mite, Ornithonyssus sylviarum (Acari: Macronyssidae)

The northern fowl mite, Ornithonyssus sylviarum (Canestrini & Fanzago, 1877), is found on several continents and has been a major pest of poultry in the United States for nearly a century. Lack of earlier USA reports in the United States suggests an introduction or change to pest status in domestic poultry systems occurred in the early 1900s. Though predominantly a nest-parasite of wild birds, this obligate hematophagous mite is a permanent ectoparasite on domestic birds, especially egg-laying chickens. Economic damage is incurred by direct blood feeding and activation of the of host's immune responses. This in turn causes decreased egg production and feed conversion efficiency, and severe infestations can cause anemia or death to birds. Here we review the biology, ecology, and recent control measures for the northern fowl mite. Photomicrographs are included of adult males and females, protonymphs, and larvae with key characters indicated. Special emphasis is placed on current knowledge gaps of basic and applied science importance.

Field evaluation of poultry red mite (Dermanyssus gallinae) native and recombinant prototype vaccines

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Field trial testing of a native and recombinant poultry red mite vaccines.

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Vaccination with a soluble mite extract (SME) resulted in a 78% reduction in mite numbers.

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Poor antibody persistence may relate to lack of effect of a recombinant cocktail vaccine.

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A semi-protective naturally acquired immunity may develop.

Vaccination is a desirable emerging strategy to combat poultry red mite (PRM), Dermanyssus gallinae. We performed trials, in laying hens in a commercial-style cage facility, to test the vaccine efficacy of a native preparation of soluble mite extract (SME) and of a recombinant antigen cocktail vaccine containing bacterially-expressed versions of the immunogenic SME proteins Deg-SRP-1, Deg-VIT-1 and Deg-PUF-1. Hens (n = 384 per group) were injected with either vaccine or adjuvant only (control group) at 12 and 17 weeks of age and then challenged with PRM 10 days later. PRM counts were monitored and, at the termination of the challenge period (17 weeks post challenge), average PRM counts in cages containing birds vaccinated with SME were reduced by 78% (p < 0.001), compared with those in the adjuvant-only control group. When the trial was repeated using the recombinant antigen cocktail vaccine, no statistically significant differences in mean PRM numbers were observed in cages containing vaccinated or adjuvant-only immunised birds. The roles of antigen-specific antibody levels and duration in providing vaccine-induced and exposure-related protective immunity are discussed.