A chitinase-like protein from Sarcoptes scabiei as a candidate anti-mite vaccine that contributes to immune protection in rabbits.

BACKGROUND: Scabies is caused by Sarcoptes scabiei burrowing into the stratum corneum of the host's skin and is detrimental to the health of humans and animals. Vaccines are an attractive alternative to replace the acaricides currently used in their control. METHODS: In the present study, the S. scabiei chitinase-like protein 5 (SsCLP5) was characterized and recombinant SsCLP5 (rSsCLP5) was evaluated as a candidate vaccine protein for anti-mite protection in rabbits. The expression, characterization and immunolocalization of SsCLP5 were examined. Vaccination experiments were performed on three test groups (n = 12 per group) immunized with purified rSsCLP5. Control groups (n = 12 per group) were immunized with PBS, QuilA saponin or empty vector protein. After challenge, the inflammatory reaction and skin lesions were graded and rSsCLP5 indirect ELISA was used to detect antibody IgG levels in serum samples at the time of vaccination and post-challenge. RESULTS: The results showed that rSsCLP5 had high immunoreactivity and immunogenicity. In S. scabiei, SsCLP5 had a wide distribution in the chewing mouthpart, legs and exoskeleton, especially the outer layer of the exoskeleton. Vaccination with rSsCLP5 resulted in 74.3% (26/35) of rabbits showing no detectable lesions after challenge with S. scabiei. CONCLUSIONS: Our data demonstrate that rSsCLP5 is a promising candidate for a recombinant protein-based vaccine against S. scabiei. This study also provides a method for studying scabies vaccine using rabbit as an animal model and a basis for screening more effective candidate proteins.

Identification of a novel PYP-1 gene in Sarcoptes scabiei and its potential as a serodiagnostic candidate by indirect-ELISA.

Scabies is a parasitic disease caused by the ectoparasite Sarcoptes scabiei, affecting different mammalian species, including rabbits, worldwide. In the present study, we cloned and expressed a novel inorganic pyrophosphatase, Ssc-PYP-1, from S. scabiei var. cuniculi. Immunofluorescence staining showed that native Ssc-PYP-1 was localized in the tegument around the mouthparts and the entire legs, as well as in the cuticle of the mites. Interestingly, obvious staining was also observed on the fecal pellets of mites and in the integument of the mites. Based on its good immunoreactivity, an indirect enzyme-linked immunosorbent assay (ELISA) using recombinant Ssc-PYP-1 (rSsc-PYP-1) as the capture antigen was developed to diagnose sarcoptic mange in naturally infected rabbits; the assay had a sensitivity of 92·0% and specificity of 93·6%. Finally, using the rSsc-PYP-1-ELISA, the Ssc-PYP-1 antibody from 10 experimentally infected rabbits could be detected from 1 week post-infection. This is the first report of S. scabiei inorganic pyrophosphatase and the protein could serve as a potential serodiagnostic candidate for sarcoptic mange in rabbits.

Transcriptomics and proteomic studies reveal acaricidal mechanism of octadecanoic acid-3, 4 - tetrahydrofuran diester against Sarcoptes scabiei var. cuniculi.

In our previous study, a new compound, octadecanoic acid-3, 4-tetrahydrofuran diester, possessing potent acaricidal activity was obtained from neem oil. This study performed RNA-seq transcriptomics and iTRAQ proteomics to uncover the acaricidal mechanism of the compound against Sarcoptes scabiei var. cuniculi. The results of transcriptomics indicated that after treatment with octadecanoic acid-3, 4-tetrahydrofuran diester, genes related to "Energy metabolism" were significantly up-/down-regulated, including citrate cycle, oxidative phosphorylation pathway and fatty acid metabolism. Proteomics analysis showed accordant changes of proteins related to oxidative phosphorylation pathway. The target proteins of the compound were NADH dehydrogenase, Ubiquinol-cytochrome c reductase, Cytochrome c oxidase, ATP synthase, enolase and superoxide dismutase. In transcriptomics-proteomics correlation analysis, the concordance rate between protein abundances and their corresponding mRNAs was 57%, while others (43%) were discordant changes, suggesting divergent regulating effects of octadecanoic acid-3, 4-tetrahydrofuran diester. These results suggested that the acaricidal mechanism of octadecanoic acid-3, 4-tetrahydrofuran diester attributed to interference with energy metabolism, especially oxidative phosphorylation pathway.

Molecular characterization of calmodulin from Sarcoptes scabiei.

Scabies, caused by the mite Sarcoptes scabiei, is a highly contagious parasitic disease that affects millions of people and other mammals worldwide. Calmodulin (CaM) is an important calcium sensor that participates in various critical physiological processes. In this study, the CaM of Sarcoptes scabiei (SsCaM) was cloned and expressed, and sequence analyses were performed using bioinformatics tools. Recombinant SsCaM (rSsCaM) was used to detect antigenicity using immunoblotting assays, and the serodiagnostic potential of rSsCaM was assessed by indirect enzyme-linked immuno-sorbent assay (ELISA). The calcium binding properties and 8-anilinonaphthalene-1-sulfonic acid (ANS) fluorescence of rSsCaM were also measured. The results indicated that SsCaM contains a 450-bp open reading frame that encodes for a polypeptide with 149 amino acids, and SsCaM was expressed as a soluble protein. Multiple sequence alignment and phylogenetic analyses indicated similarity and genetic distance between SsCaM and other species. The calcium binding properties and ANS fluorescence of rSsCaM indicated typical calcium binding characteristics. Immunolocalizaton assay showed that SsCaM was widespread in S. scabiei. SsCaM-based ELISA exhibited a sensitivity of 87.5% (28/32) and a specificity of 22.5% (9/40) for detecting anti-CaM antibodies in the sera of naturally infected rabbits. The findings of this study provide a comprehensive molecular characterization of SsCaM and suggest that rSsCaM is inappropriate for detecting S. scabiei. The results may also contribute to future studies on the molecular characteristics of the CaM of parasites.

A Proteomic Analysis of Sarcoptes scabiei (Acari: Sarcoptidae).

The pruritic skin disease scabies is caused by the burrowing of the itch mite Sarcoptes scabiei (De Geer). It is difficult to diagnose this disease because its symptoms often resemble those of other skin diseases. No reliable blood or molecular diagnostic test is available. The aim of this project was to begin to characterize the scabies proteome to identify scabies mite proteins, including those that may be useful in the development of a diagnostic test or vaccine. Various scabies mite extracts were separated by two-dimensional electrophoresis, and 844 Coomassie Blue-stained protein spots were excised, subjected to trypsin digestion, and analyzed by Matrix Assisted Laser Desorption/Ionization Time-Of-Flight/Time-Of-Flight (MALDI-TOF/TOF) mass spectrometry (MS). Tryptic fragment sequences determined by MS were searched against the recently completed S. scabiei annotated genome, leading to the identification of >150 proteins. Only 10 proteins hit to previously identified scabies proteins including actin, tropomyosin, and several ABC transporters. Thirteen proteins had homology to dust mite allergens (members of groups 8, 10, 13, 17, 20, 25, and 28). Most other sequences showed some homology to proteins in other mites and ticks including homologs of calmodulin, calreticulin, lipocalin, and glutathione-S-transferase. These data will now allow the identification of the proteins to which scabies patients produce antibodies, including those that may be good candidates for inclusion in a diagnostic test and vaccine.

Identification and expression of macrophage migration inhibitory factor in Sarcoptes scabiei.

Macrophage migration inhibitory factor (MIF) is a pleiotropic proinflammatory cytokine produced by many mammalian tissues including skin. It is also found in many invertebrate parasites of mammals including ticks and may function to aid the parasite to evade the innate and adaptive immune responses in the host. In this study, the cDNA for a MIF gene was sequenced from Sarcoptes scabiei, the scabies mite, using RT-PCR and RACE molecular techniques. The resulting nucleotide sequence had a length of 405 base pairs and the putative amino acid sequences for the mite and tick (Dermacentor variabilis) proteins were identical. The initial steps for the project resulted in the production of expressed scabies mite cDNAs. A real time (qPCR) assay was performed with MIF from scabies mites and various tick species. Results show that mRNA encoding MIF homologues was three times more abundant in the mite samples when compared to RNA prepared from D. variabilis salivary glands and 1.3 times more abundant when compared with RNA prepared from D. variabilis midgut.

A diagnostic test for scabies: IgE specificity for a recombinant allergen of Sarcoptes scabiei.

Scabies infestations are difficult to diagnose clinically and current serologic tests have less than 50% accuracy. To develop more reliable diagnosis of scabies, specific IgE antibodies to a major scabies antigen recombinant Sar s 14.3 (rSar s 14.3) were measured in 140 plasma samples from scabies-infested and control subject groups using dissociation-enhanced lanthanide fluorescent immunoassays (DELFIA). Levels of rSar s 14.3-specific IgE were quantified, and cross-reactivity with its house dust mite homologue, Der p 14, was assessed. The rSar s 14.3 DELFIA showed excellent diagnostic capability, with 100% sensitivity and 93.75% specificity for distinguishing subjects with current scabies infestation from control, uninfested subjects. Recombinant Der p 14 preparation was ineffective at inhibiting IgE binding to rSar s 14.3. This study shows that quantification of levels of IgE antibody to rSar s 14.3 is a highly sensitive method for diagnosis of scabies infestation in clinical practice.

Characterization of a serine protease homologous to house dust mite group 3 allergens from the scabies mite Sarcoptes scabiei.

The scabies mite, Sarcoptes scabiei var. hominis, infests human skin, causing allergic reactions and facilitating bacterial infection by Streptococcus sp., with serious consequences such as rheumatic fever and rheumatic heart disease. To identify a possible drug target or vaccine candidate protein, we searched for homologues of the group 3 allergen of house dust mites, which we subsequently identified in a cDNA library. The native protein, designated Sar s 3, was shown to be present in the mite gut and excreted in fecal pellets into mite burrows within the upper epidermis. The substrate specificity of proteolytically active recombinant rSar s 3 was elucidated by screening a bacteriophage library. A preference for substrates containing a RS(G/A) sequence at the P1-P2' positions was revealed. A series of peptides synthesized as internally quenched fluorescent substrates validated the phage display data and high performance liquid chromatography/mass spectrometry analysis of the preferred cleaved substrate and confirmed the predicted cleavage site. Searches of the human proteome using sequence data from the phage display allowed the in silico prediction of putative physiological substrates. Among these were numerous epidermal proteins, with filaggrin being a particularly likely candidate substrate. We showed that recombinant rSar s 3 cleaves human filaggrin in vitro and obtained immunohistological evidence that the filaggrin protein is ingested by the mite. This is the first report elucidating the substrate specificity of Sar s 3 and its potential role in scabies mite biology.

Extracts of Sarcoptes scabiei De Geer downmodulate secretion of IL-8 by skin keratinocytes and fibroblasts and of GM-CSF by fibroblasts in the presence of proinflammatory cytokines.

Previous in vitro studies showed that molecules in an extract of the mite Sarcoptes scabiei variety canis De Geer could modulate the secretion of cytokines from cultured normal human epidermal keratinocytes and dermal fibroblasts in the absence of proinflammatory cytokines in the cell culture media. The purpose of this study was to investigate whether scabies extract could also modulate cytokine and chemokine secretion from epidermal keratinocytes and dermal fibroblasts in the presence of proinflammatory cytokines that are likely present in the scabietic lesion in vivo. In particular, could the downmodulating properties of this ectoparasitic mite on skin cells be maintained in the presence of proinflammatory cytokines? We found that even in the presence of the proinflammatory cytokines interleukin (IL)-1alpha, IL-beta, and a mixture of tumor necrosis factor (TNF)alpha + IL-17, scabies extract still downregulated the levels of IL-8 secretion from keratinocytes and fibroblasts and of granulocyte/macrophage-colony stimulating factor (GM-CSF) secretion from fibroblasts that were induced by stimulation of the cells with proinflammatory cytokines alone. This study also showed that scabies molecules induced secretions of growth-related oncogene alpha (GROalpha), transforming growth factor alpha (TGFalpha), and cutaneous T-cell attracting chemokine (CTACK) from keratinocytes and IL-6 and granulocyte-colony stimulating factor (G-CSF) from fibroblasts. These findings, coupled with the previous findings that molecules in scabies extract could downregulate expression of intracellular adhesion molecule-1 (ICAM-1) and E-selectin by normal dermal microvascular endothelial cells and secretion of IL-1alpha from keratinocytes, suggest that multiple factors from scabies mites play a role in the characteristic delayed inflammatory response to a primary infestation with S. scabiei. These are adaptations that favor invasion of the host by the parasite.

Sarcoptes scabiei (Acari: Sarcoptidae) mite extract modulates expression of cytokines and adhesion molecules by human dermal microvascular endothelial cells.

The inflammatory and immune responses seen with the worldwide disease scabies, caused by the mite Sarcoptes scabiei (De Geer) (Acari: Sarcoptidae), are complex. Clinical symptoms are delayed for weeks in patients when they are infested with scabies for the first time. This study was undertaken to elucidate the role of the human dermal microvascular endothelial cell (HMVEC-D) in modulating the inflammatory and immune responses in the skin to S. scabiei. Extracts of S. scabiei were incubated with HMVEC-D and the expression of adhesion molecules and chemokine receptors on the cells and the secretion of selected cytokines were determined by enzyme-linked immunosorbent assay. S. scabiei extract was found to inhibit HMVEC-D expression of E-selectin and vascular cell adhesion molecule-1, although not intercellular adhesion molecule-1. The secretion of interleukin-8 also was inhibited by S. scabiei extract. S. scabiei extract increased expression of the chemokine receptor CXCR-1 and both down-regulated and up-regulated expression of CXCR-2, depending on the concentration tested. These findings help explain the delayed inflammatory reaction to infestation with S. scabiei.

Evidence that scabies mites (Acari: Sarcoptidae) influence production of interleukin-10 and the function of T-regulatory cells (Tr1) in humans.

We performed experiments to determine whether an extract of Sarcoptes scabiei (De Geer) influenced cytokine expression by human T-lymphocytes. Peripheral blood mononuclear cells from five sensitized donors and four donors without sensitization to scabies mites were challenged with a T-cell mitogen alone, with scabies extract (SS) alone, or with mitogen and SS together. Supernatants were analyzed for the cytokines interferon-gamma (IFNgamma), interleukin (IL)-2, IL-4, and IL-10. No IL-2 or IL-4 was produced in response to scabies extract. Cells from both naive and sensitized donors produced large amounts of IFNgamma and IL-10. The lack of IL-4 but high levels of IL-10 suggests that IL-10 was likely secreted by type 1 T-regulatory cells, which were activated by something in the scabies extract. IL-10 has anti-inflammatory and immune-suppressive effects. It may play a key role in depressing the inflammatory and immune responses in humans so that clinical symptoms are not seen until 4-6 wk after a person becomes infested with scabies mites.

Characterization of an atypical antigen from Sarcoptes scabiei containing an MADF domain.

We have cloned a cDNA encoding a novel antigen from a Sarcoptes scabiei (Acari) cDNA library by immunoscreening with sera from S. scabiei-infected dogs. The antigen is encoded by a 2,157 bp mRNA with a predicted open reading frame of 719 amino acids (molecular weight 79 kDa). Our sequence analysis identified the presence of a MADF domain in the N-terminus, and downstream of this domain there was a region of low sequence complexity. This latter region contained several blocks of triplets and quadruplets of polar amino acids (Asn, Gln and Ser), and these 3 amino acids represented 39.7% of all amino acids. The antigen was named Atypical Sarcoptes Antigen 1 (ASA1) since the MADF domain normally is found in proteins involved in transcriptional regulation. In addition, 15 out of 62 S. scabiei-infected dogs reacted with a purified recombinant version of ASA1 in Western blot analysis. With immunohistochemistry we could show that ASA1 is expressed throughout the parasite, and that IgG specific for ASA1 binds to the inside wall of the mite's burrow. To our knowledge, this is the first description of an antigen containing an MADF domain.

Extracts of scabies mites (Sarcoptidae: Sarcoptes scabiei) modulate cytokine expression by human peripheral blood mononuclear cells and dendritic cells.

We performed a series of experiments to determine if human peripheral blood mononuclear cells (PBMCs) from a healthy donor and dendritic cells (NHDCs) derived from these PBMCs reacted to molecules in a scabies extract. PBMCs extravasate from the circulatory system and enter tissues such as scabietic lesions, where monocytes become macrophages. Cells were cultured in medium alone or medium containing 50 microg/ml of Sarcoptes scabiei (SS) extract, 50 ng/ml E. coli lipopolysaccharide (LPS), or SS + LPS together. Supernatants were collected and assayed by enzyme-linked immunosorbent assay (ELISA) for specific cytokines. PBMCs stimulated with SS or LPS exhibited moderately upregulated production of interleukin (IL)-1beta and huge increases in secretions of IL-6, IL-8 and TNF-alpha. Cells co-stimulated with both SS and LPS generally secreted more of these cytokines than cells stimulated with either SS or LPS alone. LPS induced a small amount of IL-1alpha secretion, whereas SS did not, and neither additive resulted in the production of IL-10. NHDCs did not produce IL-1alpha, IL-1beta, IL-6, IL-8, or IL-10 in response to stimulation with SS. These cells did produce IL-6, IL-8, and tumor necrosis factor (TNF)-alpha in response to LPS. When cells were co-stimulated with both LPS and SS, the production of IL-6 and IL-8 was significantly reduced compared with the levels secreted after LPS stimulation alone. These studies show that molecules in a whole body extract of S. scabiei modulate the function of PBMCs (probably monocytes) and dendritic cells.