cDNA cloning and recombinant expression of collagen-binding and complement inhibitor activity of Taenia solium paramyosin (AgB)

What about the Cytoskeletal and Related Proteins of Tapeworms in the Host's Immune Response? An Integrative Overview

Recent advances have increased our understanding of the molecular machinery in the cytoskeleton of mammalian cells, in contrast to the case of tapeworm parasites, where cytoskeleton remains poorly characterized. The pertinence of a better knowledge of the tapeworm cytoskeleton is linked to the medical importance of these parasitic diseases in humans and animal stock. Moreover, its study could offer new possibilities for the development of more effective anti-parasitic drugs, as well as better strategies for their surveillance, prevention, and control. In the present review, we compile the results of recent experiments on the cytoskeleton of these parasites and analyze how these novel findings might trigger the development of new drugs or the redesign of those currently used in addition to supporting their use as biomarkers in cutting-edge diagnostic tests.

Mapping of the complement C1q binding site on Trichinella spiralis paramyosin

Background

Trichinella spiralis is a tissue-dwelling parasite has developed the ability to evade the host immune attack to establish parasitism in a host. One of the strategies evolved by the nematode is to produce proteins that immunomodulate the host immune system. TsPmy is a paramyosin secreted by T. spiralis on the surface of larvae and adult worms that can interact with complement components C1q and C8/C9 to compromise their activation and functions. To better understand the mechanism of TsPmy involved in the C1q inactivation and immune evasion, the C1q-binding site on TsPmy was investigated.

Methods

The TsPmy C1q-binding site was investigated by sequential narrow-down fragment expression in bacteria and peptide binding screening. C1q binding activity was identified by Far-Western blotting and ELISA assays.

Results

After several runs of sequential fragment expression, the C1q binding site was narrowed down to fragments of N-terminal TsPmy226-280aa and TsPmy231-315aa, suggesting the final C1q binding site is probably located to TsPmy231-280aa. A total of nine peptides covering different amino acid sequences within TsPmy231-280aa were synthesized. The binding assay to C1q determined that only P2 peptide covering TsPmy241-280aa binds to C1q, indicating that the C1q binding domain may need both the linearized sequence and conformational structure required for binding to C1q. The binding of peptide P2 to C1q significantly inhibited both C1q-initiated complement classical activation and C1q-induced macrophage chemotaxis.

Conclusions

This study identifies the C1q binding site within TsPmy which provides helpful information for developing a vaccine against trichinellosis by targeting the C1q-binding activity of TsPmy.

Fasciclin-calcareous corpuscle binary complex mediated protein-protein interactions in Taenia solium metacestode

Background

Neurocysticercosis (NC) caused by Taenia solium metacestode (TsM) is a serious neurological disease of global concern. Diverse bioactive molecules involved in the long-term survival of TsM might contribute to disease progression. Fasciclin (Fas) is an extracellular protein that mediates adhesion, migration and differentiation of cells by interacting with other molecules. We hypothesized that TsMFas might bind to calcareous corpuscle (CC) through its adhesive property and participate in crucial protein-protein interactions, thus contributing to the creation of a symbiotic interactome network.

Methods

Two paralogous TsMFas (TsMFas1 and TsMFas2) were isolated, and their molecular properties were characterized. The co-localization pattern of TsMFas1 and TsMFas2 with CC was determined. CC-TsMFas binary complex was generated by incubating CC with recombinant proteins (rTsMFas1 and 2). In vitro binding assay of CC-rTsMFas1 or CC-rTsMFas2 binary complex with TsM cellular proteins extracted from scolex and neck was conducted. Their binding partners were identified through proteomic analysis. Integrated protein-protein interaction networks were established.

Results

TsMFas1 (6072 bp long) was composed of 15 exons (841 amino acid polypeptide) interrupted by 14 introns. TsMFas2 (5201 bp long) comprised of 11 exons (597 amino acids) and 10 intervening introns. These proteins displayed 22% amino acid sequence identity to each other, but tightly conserved Fas-related domains. Several isoforms of Fas1 and Fas2 proteins might have been expressed through post-translational modifications. They showed adhesion activity with other cells. TsMFas proteins were largely distributed in parenchymal regions of the scolex and bladder wall. These molecules were co-localized with CC, a unique organelle found in platyhelminths. Subsequent proteome analysis of CC-Fas binary complex mediated protein-protein interactions revealed seven protein ligands in the TsM cellular proteins. Their functions were mainly segregated into carbohydrate metabolism (enolase, phosphoenolpyruvate carboxykinase, phosphoglycerate kinase and glyceraldehyde 3-phosphate dehydrogenase) and cytoskeleton/cellular motility (actin, paramyosin and innexin nuc-9). Those proteins had direct (physical) and/or indirect (functional) relationships along with their biochemical properties and biological roles.

Conclusion

Protein repertoires strongly suggest that TsMFas and CC may symbiotically mediate protein-protein interactions during biological processes to maintain efficacious homeostatic functions and ensure the prolonged survival of TsM in the host.

Electronic supplementary material

The online version of this article (10.1186/s13071-017-2359-2) contains supplementary material, which is available to authorized users.

Mapping of the complement C9 binding domain on Trichinella spiralis paramyosin

Background

Trichinellosis is an important foodborne zoonosis that is distributed worldwide. Trichinella spiralis may evade host complement-mediated attack by expressing complement inhibitory proteins, such as paramyosin (Pmy). Previous studies have shown that Trichinella spiralis paramyosin (Ts-Pmy) is able to bind to the human complement component C9 to inhibit the complement activation and protect the parasite from complement-mediated attack. Further determination of the complement-binding domain on Ts-pmy will enable us to better understand the Ts-Pmy’s biofunction in the immune evasion and provide feasible approach to develop epitope-based subunit vaccine against trichinellosis.

Methods

The complement C9 binding region on Ts-Pmy was determined by expression of overlapped fragments of Ts-Pmy and their binding activities to C9. The exact binding site was further narrowed-down to a 14-amino acid peptide at C-terminus using synthesized peptides with different size of amino acid sequence. The C9 complement-binding of the 14-amino acid peptide and its interference in the C9 polymerization and the complement-mediated lysis of rabbit erythrocytes was investigated.

Results

The protein interaction between human C9 and native Ts-Pmy was further confirmed by immunoprecipitation with T. spiralis lysates. The fragmental expression and C9 binding assays identified that the binding region of Ts-Pmy to C9 is located within 831–885 of Ts-Pmy C-terminus. The exact binding site on Ts-Pmy to C9 was narrowed down to 14 amino acid residues (⁸⁶⁶Val-⁸⁷⁹Met) by using different sizes of synthesized peptides. In the presence of the synthesized 14-amino acid peptide, human C9 polymerization and the hemolytic activity of the human complement was inhibited.

Conclusions

Our results revealed the precise molecular basis for T. spiralis to produce Ts-Pmy as an immunomodulator to evade the attack of the host complement system as a survival mechanism.

Tissue expression and the host's immunological recognition of a Rhipicephalus microplus paramyosin

Rhipicephalus microplus is a parasite that causes economic losses in cattle herds, and immunological control is the most promising alternative to replace chemical control. The muscular protein paramyosin has been additionally found in non-muscle tissues and characterized as presenting activities that enable the evasion of the host's immune system in various parasites. This report investigated the recognition level of paramyosin by sera of infested bovines, its expression in tissues, organs and different life stages of R. microplus. ELISA analyses showed that paramyosin and salivary gland extract were recognized by infested Bos taurus and B. indicus sera. Paramyosin gene expression was evaluated in egg, larvae, adult male, and several tissues of partially- and fully-engorged females by qRT-PCR, showing the highest expression levels in fat body. These results show that R. microplus paramyosin is immunologically recognized during the tick infestation and together with the high transcription rate found in organs that do not present a highly developed musculature, further suggests that it may possess additional, non-muscle functions in the tick-bovine relationship.

Synthetic peptide-targeted selection of phage display mimotopes highlights immunogenic features of α-helical vs non-helical epitopes of Taenia solium paramyosin: implications for parasite- and host-protective roles of the protein

Paramyosin of the pig-human parasite Taenia solium (TPmy) is a α-helical protein located on the worm surface that is suggested to fulfill an immunomodulatory role protecting the parasite against host immune system. Besides, in challenging experiments the protein shows a vaccine potential. These observations imply that TPmy harbors antigenic determinants for each of these contrasting actions. However the suggestion was not given a support from experimental data because respective epitopes have not been described thus far. To circumvent this difficulty, we use synthetic peptides with sequences of regions composed of α-helical or linear structure to induce rabbit antibody responses for phage-display mapping of epitope core amino-acid sets. Antibodies to α-helical regions were weak binders and M13 phage-displayed peptides selected by them from two different libraries exhibited no amino-acid similarities with the original protein site. In contrast, the antibodies produced in response to non-helical segment within α-helical structure were better binders and selectors of perfect structural mimics of the protein site. This first phage display epitope analysis of TPmy supports the notion that the rod-like α-helix, which encompasses over 90% of the total amino acids, may serve as an immunomodulatory shield that protects the parasite. Further, the seven non-helical segments of the TPmy molecule may represent the only anti-parasite discrete immunogenic epitopes whose representative mimotopes can be utilized in development of pure epitope vaccines.

The hamster model for identification of specific antigens of Taenia solium tapeworms

Humans acquire taeniasis by ingesting pork meat infected with Taenia solium cysticerci, which are the only definitive hosts of the adult stage (tapeworm) and responsible for transmitting the human and porcine cysticercosis. Hence, detection of human tapeworm carriers is a key element in the development of viable strategies to control the disease. This paper presents the identification of specific antigens using sera from hamsters infected with T. solium tapeworms analyzed by western blot assay with crude extracts (CEs) and excretion-secretion antigens (E/S Ag) obtained from T. solium cysticerci and tapeworms and extracts from other helminthes as controls. The hamster sera infected with T. solium tapeworms recognized specific bands of 72, 48, 36, and 24 kDa, in percentages of 81, 81, 90, and 88%, respectively, using the T. solium tapeworms E/S Ag. The antigens recognized by these hamster sera could be candidates to improve diagnosis of human T. solium taeniasis.

Molecular cloning and characterization of a paramyosin from Clonorchis sinensis

Paramyosin is a myofibrillar protein present in helminth parasites and plays multifunctional roles in host-parasite interactions. In this study, we identified the gene encoding paramyosin of Clonorchis sinensis (CsPmy) and characterized biochemical and immunological properties of its recombinant protein. CsPmy showed a high level of sequence identity with paramyosin from other helminth parasites. Recombinant CsPmy (rCsPmy) expressed in bacteria had an approximate molecular weight of 100 kDa and bound both human collagen and complement 9. The protein was constitutively expressed in various developmental stages of the parasite. Imunofluorescence analysis revealed that CsPmy was mainly localized in the tegument, subtegumental muscles, and the muscle layer surrounding the intestine of the parasite. The rCsPmy showed high levels of positive reactions (74.6%, 56/75) against sera from patients with clonorchiasis. Immunization of experimental rats with rCsPmy evoked high levels of IgG production. These results collectively suggest that CsPmy is a multifunctional protein that not only contributes to the muscle layer structure but also to non-muscular functions in host-parasite interactions. Successful induction of host IgG production also suggests that CsPmy can be applied as a diagnostic antigen and/or vaccine candidate for clonorchiasis.

Paragonimus westermani: Biochemical and immunological characterizations of paramyosin

Paramyosin of the helminth parasite is a muscle protein that plays multifunctional roles in host-parasite relationships. In this study, we have cloned a gene encoding Paragonimus westermani paramyosin (PwPmy) and characterized biochemical and immunological properties of the recombinant protein. The recombinant PwPmy (rPwPmy) was shown to bind both human immunoglobulin G (IgG) and collagen. The protein was constitutively expressed in various developmental stages of the parasite and its expression level increased progressively as the parasite matured. Immunohistological analysis revealed that PwPmy was mainly localized in subtegumental muscle, tegument and cells surrounding the oral sucker, intestine, and ovary of the parasite. Sera from patients with paragonimiasis showed antibody reactivity against rPwPmy, and IgG1 and IgG4 were predominant. Immunization of mice with rPwPmy also induced high IgG responses. Biochemical and immunological characterization of PwPmy may provide valuable information for the further study to develop a vaccine or a chemotherapeutic agent for paragonimiasis.

Control of scavenger receptor-mediated endocytosis by novel ligands of different length

The scavenger receptor recognized as a multiligand family of receptors falls in the group that is internalised through endocytosis. In this report we used several recombinant fragments of the tapeworm protein paramyosin, known to form filamentous dimers that bind collagenous structures as ligands of different length for the class A type I scavenger receptor (SR-AI). While native CHO cells are unresponsive to any of the recombinant fragments, it is shown that CHO cells transfected with this receptor efficiently internalise recombinant fragments that correspond to two thirds of the full-length paramyosin. In contrast, recombinant products corresponding to one-third of the full-length paramyiosin are not internalised. It is also shown that important molecules in the organization of the coated pit, are enriched when the two-thirds long paramyosin fragments were bound and internalised through the SR-AI. Moreover, internalisation of these fragments trigger a classical apoptotic pathway shown by the presence of TUNEL positive cells and the appearance of apoptotic bodies. We report paramyosin as a new ligand for the scavenger receptor and provide evidence supporting the notion that these receptors upon the formation of arrays with length-specific molecules, not only trigger endocytosis but also seem to regulate the synthesis of molecules involved in the organization of coated pits.

Molecular cloning and characterization of full-length cDNAs encoding a novel high-molecular-weight Dermatophagoides pteronyssinus mite allergen, Der p 11

BACKGROUND

Dermatophagoides pteronyssinus (Dp) and D. farinae (Df) mites are the most important source of indoor aeroallergens. Most Dp mite allergens identified to date have relatively low molecular weights (MWs). Identification of high-MW mite allergens is a crucial step in characterizing the complete spectrum of mite allergens and to provide appropriate tools for diagnostic and therapeutic application.

METHODS

The full-length Der p 11 cDNA clone was isolated using cDNA library immunoscreening, the 5'-3' rapid amplification of cDNA ends (RACE) system and polymerase chain reactions (PCR). The whole cDNA insert and its PCR-derived DNA fragments (p1 to p4) were generated and expressed in the Escherichia coli expression system. The allergenicity of the recombinant protein and its peptide fragments was examined by IgE immunodot assays. The IgE-binding reactivity of rDer p 11 was analyzed in the serum of 50 asthmatic children with positive reactivity to Dp mite extract. Its recombinant peptide fragments were also examined by immunodot assays in 30 mite-allergic children.

RESULTS

Der p 11 cDNA consists of a 2625-bp open reading frame encoding a 103-kDa protein with 875 amino acids. It exhibits significant homology with the paramyosin of other invertebrates. The protein sequence alignment of this newly identified Dp mite allergen (denominated as Der p 11) revealed over 89% identity with Der f 11 and Blo t 1. Among 50 Dp-sensitive asthmatic children, rDer p 11 showed positive IgE-binding reactivity to 39 patients (78%). Using immunodot assays, multiple human IgE-binding activities were demonstrated in all four fragments of Der p 11. Using immunoblot assays, the dominant IgG-binding epitope for monoclonal antibody (mAb642) was located in fragment p3 only. In immunoblot assays, cross-inhibition between rDer p 11 and rDer f 11 was up to 73-80% at concentrations of 100 microg/ml.

CONCLUSIONS

This study confirms that the newly identified recombinant Der p 11 is a novel and important high-MW Dp mite allergen for asthmatic children. Our data also indicates that human IgE-binding major epitopes are scattered over the entire molecule of Der p 11.

Invertebrate Muscles: Muscle Specific Genes and Proteins

This is the first of a projected series of canonic reviews covering all invertebrate muscle literature prior to 2005 and covers muscle genes and proteins except those involved in excitation-contraction coupling (e.g., the ryanodine receptor) and those forming ligand- and voltage-dependent channels. Two themes are of primary importance. The first is the evolutionary antiquity of muscle proteins. Actin, myosin, and tropomyosin (at least, the presence of other muscle proteins in these organisms has not been examined) exist in muscle-like cells in Radiata, and almost all muscle proteins are present across Bilateria, implying that the first Bilaterian had a complete, or near-complete, complement of present-day muscle proteins. The second is the extraordinary diversity of protein isoforms and genetic mechanisms for producing them. This rich diversity suggests that studying invertebrate muscle proteins and genes can be usefully applied to resolve phylogenetic relationships and to understand protein assembly coevolution. Fully achieving these goals, however, will require examination of a much broader range of species than has been heretofore performed.

Cloning and expression of a Na+, K+-ATPase α-subunit from Taenia solium (TNaK1α)

The Na(+), K(+)-ATPase are membrane-associated enzymes that transport Na(+) and K(+) across the membrane generating chemical and electrical gradients, essential to maintain the resting potential for the excitation of myocytons and neurons and for transport of nutrients. The cDNA encoding a full-length isoform of Taenia solium Na(+), K(+)-ATPase alpha-subunit (TNaK1alpha) was isolated from a cysticercal cDNA library. TNaK1alpha has 1014 amino acids and a predicted molecular mass of 111,989Da. The protein displays strong sequence homology and conserved motifs typical of Na(+), K(+)-ATPase alpha-subunits. Northern and Southern hybridizations reveal a TNaK1alpha mRNA of about 3.7kb, which is encoded by a single gene. Polyclonal antibodies raised against a synthetic peptide corresponding to the NH(2)-terminal sequence of TNaK1alpha recognized a 100-kDa polypeptide in the membrane fraction of adult and larval stages of T. solium and other Taenia species. Immunolocalization studies using the same antibodies revealed that the TNaK1 is preferentially localized in muscle cells and protonephridial ducts, and in small quantities in the tegument of T. solium cysticerci.

Avian reovirus nonstructural protein microNS forms viroplasm-like inclusions and recruits protein sigmaNS to these structures

The M3 genome segment of avian reovirus 1733, which encodes the nonstructural protein microNS, is 1996 nucleotides long and contains a long open reading frame that is predicted to encode a polypeptide of 635 amino acid residues. Examination of the deduced amino acid sequence of microNS revealed the presence of two regions near its carboxyl terminus with a high probability of forming alpha-helical coiled coils. Expression of the M3 gene in both infected and transfected cells revealed that this gene specifies two protein isoforms that are recognized by a microNS-specific antiserum. Only the larger microNS isoform, but not the smaller one, interacts with the nonstructural protein sigmaNS in infected cells, suggesting that the two isoforms play different roles during avian reovirus infection. In the second part of this study, we show that microNS and the nonstructural protein sigmaNS colocalize throughout the viral life cycle in large and small phase-dense globular cytoplasmic inclusions, which are believed to be the sites of viral replication and assembly. Individual expression of these proteins in transfected cells of avian and mammalian origin revealed that while microNS is able to form inclusions in the absence of other viral proteins, sigmaNS distributes diffusely throughout the cytoplasm in the absence of microNS. These data suggest that microNS is the minimal viral factor required for inclusion formation during avian reovirus infection. On the other hand, our findings that sigmaNS associates with microNS in infected cells, and that sigmaNS colocalizes with microNS in viroplasm-like inclusions when the two proteins are coexpressed in transfected cells, suggest that microNS mediates the association of sigmaNS to inclusions in avian reovirus-infected cells.

Observations on the musculature and isolated muscle fibres of the liver fluke, Fasciola hepatica

The liver fluke, Fasciola hepatica relies on a well-developed muscular system, not only for attachment, but for many aspects of its biology. Despite this, little is known about the system beyond the gross organization of the main somatic muscle layers. In the present study, a range of techniques have been applied to F. hepatica in order to understand more about various aspects of muscle organization, biochemistry (in terms of muscle proteins) and identity of isolated muscle fibres. Scanning electron microscopy has provided a direct visualization in situ of the somatic muscle layers and the organization of the muscle fibres within the ventral sucker. The muscle bundles contributing to the main somatic muscle layers are made up of up to 10 individual muscle fibres. Phalloidin staining for actin, in conjunction with confocal microscopy, confirmed the presence of 2 main somatic muscle layers (outer circular, inner longitudinal), beneath which lies a third layer of oblique muscle fibres. The use of propidium iodide in combination with phalloidin staining for actin demonstrated that the cell bodies associated with the 2 main somatic muscle layers are situated beneath the longitudinal muscle layer and are connected to their respective muscle fibres by short cytoplasmic processes. Myosin immunoreactivity was demonstrated in the somatic muscle layers and in the muscle layers surrounding various organ systems within the fluke. Double labelling for actin and myosin confirmed the co-localization of the 2 muscle proteins in the muscle fibres of the ventral sucker. Muscle fibres from the somatic muscle layers and the ventral sucker have been isolated and images obtained with phase-contrast microscopy and scanning electron microscopy. The muscle fibres contain actin and myosin, but lack a nucleus, the connection with the cell body having been broken during the isolation procedure.

Vaccination against cestode parasites: anti-helminth vaccines that work and why

Highly effective recombinant vaccines have been developed against the helminth parasites Taenia ovis, Taenia saginata and Echinococcus granulosus. These vaccines indicate that it is possible to achieve a reliable, high level of protection against a complex metazoan parasite using defined recombinant antigens. However, the effectiveness of the vaccines against the taeniid cestodes stands in contrast to the more limited successes which characterise attempts to develop vaccines against other platyhelminth or nematode parasites. This review examines the features of the host-parasite relationships among the taeniid cestodes which have formed the basis for vaccine development. Particular consideration is given to the methodologies that have been used in making the cestode vaccines that might be of interest to researchers working on vaccination against other helminths. In developing the cestode vaccines, antigens from the parasites' infective larval stage contained within the egg (oncosphere) were identified as having the potential to induce high levels of protection in vaccinated hosts. A series of vaccination trials with antigen fractions, and associated immunological analyses, identified individual protective antigens or fractions. These were cloned from cDNA and the recombinant proteins expressed in Escherichia coli. This strategy was independently successful in developing vaccines against T. ovis and E. granulosus. Identification of protective antigens for these species enabled rapid identification, cloning and expression of their homologues in related species and thereby the development of effective vaccines against T. saginata, E. multilocularis and, more recently, T. solium. The T. saginata vaccine provides an excellent example of the use of two antigen components, each of which were not protective when used individually, but when combined they induce a reliable, high level of protection. One important contributing factor to the success of vaccine development for the taeniid cestodes was the concentration on studies seeking to identify native host-protective antigens, before the adoption of recombinant methodologies. The cestode vaccines are being developed towards practical (commercial) application. The high level of efficacy of the vaccines against T. solium cysticercosis and hydatid disease suggests that they would be effective also if used directly in humans.

Comparative allergenicity studies of native and recombinant Blomia tropicalis Paramyosin (Blo t 11)

BACKGROUND

The complementary DNA (cDNA) encoding for Blo t 11, a 102 kD allergen from Blomia tropicalis (Bt) was isolated, expressed and characterized previously. This study aimed to isolate the native Blo t 11 allergen and compare its allergenicity with the recombinant forms.

METHODS

Native Blo t 11 (nBlo t 11) was isolated from crude Bt extract by immuno-affinity chromatography, analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot, and verified by MALDI-TOF MS. Recombinant full-length Blo t 11 (rFL-Blo t 11) and its immunodominant peptide (fD) were expressed as glutathione S-transferase (GST)-fusion proteins in Escherichia coli. Immunoglobulin E (IgE) reactivity of the Blo t 11 allergens were determined by enzyme-linked immunosorbent assay (ELISA) and skin prick test. The inhibition capacity of the nBlo t 11 against fD and vice versa was determined by absorption studies.

RESULTS

Affinity purified nBlo t 11 was susceptible to degradation with the major degraded product resolved at approximately 66 kD. The nBlo t 11 was confirmed by immunoblot analysis and MALDI-TOF MS that generated 13 peptides with complete identity to the deduced amino acid sequence of Blo t 11. Comparative in vitro and in vivo allergenicity tests and the cross inhibition studies between the native and recombinant Blo t 11 showed that recombinant fD, but not the rFL-Blo t 11, has comparable IgE reactivity with the native counterpart.

CONCLUSIONS

This comparative study confirmed that the recombinant peptide fD contains the main immunodominant region of Blo t 11. This recombinant peptide, instead of the full-length protein, is a good candidate for diagnostic and therapeutics development for mite allergy.

Peptide mapping of immunoglobulin E and immunoglobulin G immunodominant epitopes of an allergenic Blomia tropicalis paramyosin, Blo t 11

BACKGROUND

The identification of immunodominant peptides containing the IgE and IgG epitopes on allergen molecules is an important step in understanding the interaction of the allergen with the immune system and, thus, essential for the development of effective immunotherapeutic and diagnostic reagents. The present study aimed to map the IgE and IgG immunodominant peptides of Blomia tropicalis (Bt) allergen Blo t 11, a high molecular weight allergen homologous to paramyosin, exhibiting important allergenic activity.

METHODS

Eleven overlapping fragments of Blo t 11 cDNA gene were expressed as glutathione s-transferase (GST) fusion peptides, which were affinity-purified using the glutathione-Sepharose column. Human IgE and IgG immunodominant peptides were determined by dot blot immunoassay using crude Bt extract-positive sera from asthmatic patients. Evaluation of allergenicity, specific hIgG subclass analysis, and cross- and self-inhibition studies were determined by enzyme-linked immunosorbent assay.

RESULTS

Blo t 11 contains multiple IgE and IgG immunodominant peptides scattered throughout the molecule. The dominant IgE and IgG peptides were mapped at amino acid positions 336-557 and 698-875, respectively. An immunodominant peptide (fD) registered a higher percentage of IgE and IgG reactivity compared to the rFL-Blo t 11. Significant serum levels of Blo t 11- and fD-specific IgG1, IgG2 and IgG4, but not IgG3 were detected in the Bt extract-positive sera tested. Cross-inhibition study revealed the rFL-Blo t 11 was significantly inhibited by fD.

CONCLUSION

The IgE and IgG immunodominant peptides of Blo t 11 have been mapped. Our data suggest that utilization of Blo t 11 fragment(s) or chimeric fusion fragments containing IgE and IgG epitopes could be a better alternative in the development of diagnostic and therapeutic reagents for mite allergy.

cDNA cloning and expression of Blo t 11, the Blomia tropicalis allergen homologous to paramyosin

Blomia tropicalis is an important mite species in many parts of the world and the most predominant mite species in tropical countries. The prevalence of sensitization to this species has probably been underestimated because commercial extracts are largely unavailable. Identification and characterization of B. tropicalis allergens is an important step toward understanding the role of this species in allergic sensitization and could provide appropriate reagents for diagnostic and therapeutic procedures. This paper describes the isolation, sequence analysis, expression and allergenicity of a cDNA gene coding for a B. tropicalis allergen with homology to paramyosin, a high-molecular-weight allergen previously identified in Dermatophagoides farinae. The full-length Blo t 11 cDNA gene was isolated by cDNA library screening, 5'-rapid amplification of cDNA ends and long-distance PCR. Sequence analysis was performed with a combination of CLUSTAL W, CGC and BLAST program packages. The cDNA gene was expressed as a GST fusion protein in Escherichia coli and purified by affinity chromatography using the glutathione Sepharose column. Allergenicity of the rBlo t 11 was tested by human IgE dot blot immunoassay. Blo t 11 is a 3,111-bp cDNA gene with a 2,625-bp open reading frame coding for an 875-amino acid protein, exhibiting significant homology with different invertebrate paramyosins. The human IgE dot blot immunoassay showed that the rBlo t 11 reacted positively to 52% (33/63) of sera from asthmatic patients. Blo t 11 is the homolog of Der f 11 exhibiting potentially important allergenic activity.

Human T and B cell epitope mapping of Taenia solium paramyosin

Taenia solium paramyosin is an immunodominant antigen in human and porcine cysticercosis that has shown promise as a vaccine candidate against schistosomiasis and some filariasis. There are few studies to identify the immunologically relevant regions of paramyosin. In this work, we characterize the humoral and cellular response of neurocysticercotic patients against T. solium paramyosin. Western blots using different recombinant fragments of T. solium paramyosin, showed that the sera from neurocysticercotic patients were strongly reactive against the carboxyl end region, with poor recognition of the central and amino regions. In contrast, the cellular immune response of patients did not show preferential recognition of any region of paramyosin.

Characterization and protective potential of the immune response to Taenia solium paramyosin in a murine model of cysticercosis

Paramyosin has been proposed as a vaccine candidate in schistosomiasis and filariasis. However, limited information is available about its protective potential against cysticercosis and the immune response it induces. Immunization of mice with recombinant full-length paramyosin of Taenia solium (TPmy) results in about a 52% reduction in parasite burden after a subsequent challenge by intraperitoneal inoculation of Taenia crassiceps cysticerci. Immunization assays using recombinant fragments of TPmy, corresponding approximately to thirds on the amino, central, or carboxyl regions, suggest that protective epitopes are located mostly in the amino-end third. Proliferation assays using T cells obtained from mice immunized with the full-length recombinant TPmy also showed a preferential response to the amino-terminal fragment. In contrast, antibodies in the sera from these mice predominantly recognize epitopes located in the carboxyl-terminal fragment, being the immunoglobulin G1 subclass, the predominant antibody isotype. Characterization of the cellular immune response induced against the protective amino-terminal fragment reveals production of gamma interferon and interleukin-2, but not interleukin-4, suggesting a Th1-like profile.

Serum specific IgE reactivity to recombinant Der f 11 in asthmatic children

This study was designed to examine the prevalence of positive serum IgE reactivity to the recombinant group 11 Dermatophagoides farinae allergen (rDer f 11) in asthmatic children in Taiwan. Using immunoblot analysis in a preliminary study of 18 asthmatic children, 13 (72.2%) reacted positively to rDer f 11 and 16 (88.9%) showed positive reactivity to D. farinae extracts. The allergenicity of rDer f 11 was further evaluated with in vivo skin tests and in vitro IgE immunodot assays in 24 mite skin-test-positive asthmatic children. Whereas 17 (70.8%) had positive skin tests to rDer f 11, 18 (75.0%) had positive serum IgE reactivity to rDer f 11. A good coincidence (87.5%) between the immunodot assay and the skin test was confirmed in these asthmatic children. Moreover, the prevalence of serum IgE reactivity to rDer f 11 was further investigated in a large panel of 49 mite skin-test-positive asthmatic children. Again, 38 (77.6%) had positive serum IgE reactivity to rDer f 11 in immunodot assays. Taken together the positive IgE reactivity to rDer f 11 in immunodot analysis ranged from 75 to 77.6% in two groups of 73 mite skin-test-positive asthmatic children. High incidence of serum IgE antibodies specific for rDer f 11 in the present study suggests that Der f 11 is a novel major allergen of house dust mites.

Paramyosin from the parasitic mite Sarcoptes scabiei: cDNA cloning and heterologous expression

The burrowing mite Sarcoptes scabiei is the causative agent of the highly contagious disease sarcoptic mange or scabies. So far, there is no in vitro propagation system for S. scabiei available, and mites used for various purposes must be isolated from infected hosts. Lack of parasite-derived material has limited the possibilities to study several aspects of scabies, including pathogenesis and immunity. It has also hampered the development of high performance serological assays. We have now constructed an S. scabiei cDNA expression library with mRNA purified from mites isolated from red foxes. Immunoscreening of the library enabled us to clone a full-length cDNA coding for a 102.5 kDa protein. Sequence similarity searches identified the protein as a paramyosin. Recombinant S. scabiei paramyosin expressed in Escherichia coli was recognized by sera from dogs and swine infected with S. scabiei. We also designed a small paramyosin construct of about 17 kDa that included the N-terminal part, an evolutionary variable part of the helical core, and the C-terminal part of the molecule. The miniaturized protein was efficiently expressed in E. coli and was recognized by sera from immunized rabbits. These data demonstrate that the cDNA library can assist in the isolation of important S. scabiei antigens and that recombinant proteins can be useful for the study of scabies.

Vaccination against cysticercosis and hydatid disease

Infections with the larval stages of taeniid cestode parasites cause substantial human morbidity as well as economic losses in domestic livestock species. Despite ongoing efforts around the world, few countries have been able substantially to reduce or eradicate these infections through the use of anthelmintics and lifestyle changes. Vaccines offer an additional potential tool to assist with the control of parasite transmission. Here, Marshall Lightowlers and colleagues review the substantial progress that has been made towards developing practical vaccines against hydatid disease in sheep and cysticercosis in sheep and cattle. Recombinant antigens have been used to induce more than 90% protection against challenge infections. Such success in animals encourages investigation of the potential use of vaccines in humans to prevent hydatid disease arising from infection with Echinococcus granulosus and cysticercosis from infection with Taenia solium.

Protein sequence analysis and mapping of IgE and IgG epitopes of an allergenic 98-kDa Dermatophagoides farinae paramyosin, Der f 11

BACKGROUND

A 98-kDa mite paramyosin (Der f 11) from Dermatophagoides farinae (Df) is highly allergenic, and its cDNA (Df642) has been cloned. This paper describes the sequence characteristics and the mapping of the immunodominant human IgE and IgG epitopes of Der f 11.

METHODS

The protein sequence analysis was performed with a combination of FASTA, GCG, and CLUSTAL W computing packages. The whole cDNA insert and its PCR-derived DNA fragments were generated and expressed in E. coli. These overlapping recombinant peptides (F1 to F5) were used for B-cell epitope mapping with 18 mite-allergic sera by dot immunoassays.

RESULTS

Df642 cDNA encodes a partial sequence that contains the 2nd to 26th 28-residue repeats and lacks the N-terminus and the C-terminus. The sequence identity of Der f 11 with other known paramyosins is 34-60%. The dominant IgE epitopes are located in peptides F1 and F4, whereas the dominant IgG epitopes are located in peptides F1 and F2. These peptides are more reactive than whole rDf642.

CONCLUSIONS

Mite paramyosin is very similar to other known paramyosins. The human IgE and IgG epitopes are scattered throughout the entire molecule. Data also indicate the presence of unique IgE and IgG epitopes in Der f 11.

Sequence analysis and expression of a cDNA clone encoding a 98-kDa allergen in Dermatophagoides farinae

BACKGROUND

The important dust mite allergens identified to date are of molecular weights ranging from 14 to 60 kDa. Our previous protein study indicated that the 98-kDa native paramyosin in Dermatophagoides farinae mite showed IgE reactivity with 82% of the mite-sensitive asthmatic patients suggesting that it is a novel major mite allergen. This study described the isolation and characterization of the cDNA clone encoding the 98-kDa mite allergen.

METHODS

A Dermatophagoides farinae cDNA library was constructed in lambda ZAPII vector and the library was immunoscreened with a monoclonal antibody 642. The cDNA insert was sub-cloned into M13 sequencing vector for single-stranded sequencing. The whole cDNA insert was expressed in pGEX-2T Escherichia coli expression system as a fusion protein with GST. The allergenicity of the recombinant peptides was tested by skin tests and IgE immunoassay. The IgE and IgG immunoassays were performed with sera from 20 mite-allergic patients.

RESULTS

The cDNA clone Df642 was 2134 bp long, coding for a polypeptide of 711 amino acid residues. Protein sequence analysis and alignment confirmed that the deduced polypeptide is a mite paramyosin which is truncated slightly at the N- and C-terminuses. In vivo skin tests and in vitro IgE-binding study showed that 62% (13/21) and 50% (10/20) of the mite-sensitive asthmatic patients reacted positively with the recombinant Dermatophagoides farinae paramyosin, respectively.

CONCLUSION

The study indicated that 98-kDa mite paramyosin is an important allergen.

A new potent antigen from Echinococcus granulosus associated with muscles and tegument

An immunoscreening of a cDNA library derived from the adult stage of the parasitic platyhelminth Echinococcus granulosus has been carried out with sera from infected dogs. The EgA31 clone encodes a fibrous protein which shares some sequence elements with paramyosins. The corresponding gene is present as a single copy in the genome. As revealed by an antibody obtained against a fusion protein produced in bacteria, the polypeptide has a molecular weight of 66 kDa. This polypeptide is present at all developmental stages studied and is a potent antigen during an infection by the adult stage in the dog and during cyst growth in human patients. By immunohistology, it was shown that it is present in the tegument and subtegumental parenchyma of the adult with a main location in the region of the suckers where it rapidly accumulates at the time of the head evagination. It is also present in the germinal layer of the cyst and on the protoscolex.

Characterization of cerebrospinal fluid antibody specificities in neurocysticercosis using phage display peptide library

To identify epitopes for antibodies present in cerebrospinal fluid (CSF) samples from two patients with confirmed neurocysticercosis, we used a phage peptide library that displayed random dodecapeptides as a fusion to the minor coat protein (pIII) of phage M13. To increase the specificity of selection, plates coated with anti-human Fc antibody were used in five rounds of biopanning. The DNA inserts of 30 selected clones were determined and the deduced amino acid sequences were analyzed. Sequence similarities between affinity-selected clones and three known T. solium and T. crassiceps proteins were encountered. Two phage clones have been shown to react in enzyme-linked immunosorbent assay with CSF samples from other patients with neurocysticercosis, and no reaction was observed with CSF samples from patients with other neurological disorders used as negative controls. Our results suggest that affinity selection of peptides from phage libraries using CSF samples from patients is an attractive tool for the development of novel reagents for a simple and sensitive immunodiagnostic test and for understanding the molecular mechanisms participating in the pathogenesis of neurocysticercosis.

Primary peptide sequences from squid muscle and optic lobe myosin IIs: a strategy to identify an organelle myosin

The squid giant axon provides an excellent model system for the study of actin-based organelle transport likely to be mediated by myosins, but the identification of these motors has proven to be difficult. Here the authors purified and obtained primary peptide sequence of squid muscle myosin as a first step in a strategy designed to identify myosins in the squid nervous system. Limited digestion yielded fourteen peptides derived from the muscle myosin which possess high amino acid sequence identities to myosin II from scallop (60-95%) and chick pectoralis muscle (31-83%). Antibodies generated to this purified muscle myosin were used to isolate a potential myosin from squid optic lobe which yielded 11 peptide fragments. Sequences from six of these fragments identified this protein as a myosin II. The other five sequences matched myosin II (50-60%, identities), and some also matched unconventional myosins (33-50%). A single band that has a molecular weight similar to the myosin purified from optic lobe copurifies with axoplasmic organelles, and, like the optic lobe myosin, this band is also recognized by the antibodies raised against squid muscle myosin II. Hence, this strategy provides an approach to the identification of a myosin associated with motile axoplasmic organelles.

A vaccine against the Asian schistosome, Schistosoma japonicum: an update on paramyosin as a target of protective immunity

Paramyosin from parasitic worms of the genus Schistosoma has shown promise as a vaccine target and it is one of the candidates selected by WHO for the development of a vaccine against schistosomiasis. Here we discuss the literature of the past decade and report on different recombinant paramyosin constructs we are using in our laboratory to develop a vaccine against the Asian schistosoma, Schistosoma japonicum.

Granuloma cytokines in murine cysticercosis

Neurocysticercosis, caused by Taenia solium, is one of the most common causes of seizures worldwide. The symptoms result from granulomatous inflammation associated with dying cyst forms of the parasite. Although the invasive larvae can be killed by immune serum plus complement, immunity to the cyst stage depends on a cellular response. This dichotomous immune response is reminiscent of the extremes of the immune response associated with T helper 1 (Th1) and Th2 cytokine profiles. To characterize the cytokine response in cysticercosis, granulomas were removed from the peritoneal cavity of mice infected with Taenia crassiceps cysts and examined for cytokine message by in situ hybridization using 35S-labeled RNA probes. The granulomas were staged based on histologic appearance of the degenerating parasite. Message for gamma interferon (IFN-gamma) was identified by light microscopy in 11 of the 12 granulomas, and interleukin-2 (IL-2) message was identified in 9 of the 12. By laser scanning confocal microscopy, significantly increased IFN-gamma and IL-2 pixel intensity was identified in nearly all of the granulomas from early histologic stages. Message for IL-4 was seen in 6 of the 12 granulomas. Only granulomas with complete destruction of the parasite architecture displayed more than minimal amounts of IL-4 message by light microscopy, and only 2 of 12 granulomas had IL-4 pixel intensity significantly above background. Only minimal amounts of IL-10 message were detected in 4 of 11 granulomas. Thus, early granulomas in cysticercosis are predominantly associated with a Th1 response, whereas later granulomas, in which parasite destruction is complete, have a mixture of Th1 and IL-4. The Th1 response appears to play an important role both in the pathogenesis of disease as well as in the clearing of the parasites, with IL-4 involved in downregulation of the initial response.

Immunocharacterization of Taenia solium oncosphere and metacestode antigens

A partial immunocharacterization of oncosphere and metacestode antigens of Taenia solium was carried out and compared to antigens from other taeniid species. The results indicated that T. solium metacestode antigen contained epitopes cross reactive with rabbit anti-sera to adult and oncospheral stages of the parasite. Oncospheres, however, consisted largely of stage specific antigens. Western blot analysis indicated that T. solium and T. pisiformis shared several oncospheral antigens; however, this was not the case with T. solium and T. hydatigena. Western blot analysis showed a time-related increase in the number of molecules recognized by antibodies to T. solium oncosphere and metacestode antigens in pigs experimentally infected with T. solium eggs. Oncosphere specific antibodies were detected in pig sera one month after experimental infection whereas antibodies to cystic stage antigens were not present until the 3rd to 5th month post infection. Sera from neurocysticercotic patients as well as naturally infected cysticercotic pigs recognized high molecular weight antigens in the oncospheres.

Gene cloning and complete nucleotide sequence of philippine Schistosoma japonicum paramyosin

The development of an effective vaccine is recognised as a necessary adjunct to the control of schistosomiasis japonica, a disease affecting several million people in China and the Philippines. Currently, recombinant Schistosoma japonicum molecules are considered most suitable for large scale vaccine production and a number of genes encoding vaccine candidate polypeptides have been cloned and expressed (see Waine et al., 1993a). One of the molecules providing most promise as a vaccine target is paramyosin (Butterworth, 1992), a major structural protein of thick filaments in the muscle of most invertebrates; paramyosin genes have now been cloned from a range of parasitic helminths, including schistosomes (Limberger and McReynolds, 1990; Laclette et al., 1991; Dahmen et al., 1993; Landa et al., 1993; Mühlschlegel et al., 1993, Nara et al., 1994). The cloning and nucleotide sequence of S. Japonicum paramyosin is described.

Schistosoma japonicum: heterogeneity in paramyosin genes

Paramyosin is an integral muscle protein found in many invertebrates including schistosomes, and is considered an important candidate vaccine antigen in schistosomiasis. The characterisation of natural molecular variation in vaccine antigens including paramyosin is important because strain-specific vaccination may be necessary against schistosomiasis japonica. We have isolated partial cDNAs encoding paramyosin from an adult, Chinese strain Schistosoma japonicum gene library. Two of these cDNAs (B6 and Y6) encode the same region of paramyosin but their nucleotide sequences differ at eight positions and their deduced amino acid sequences differ by an arginine/cysteine substitution, demonstrating intrastrain variation in paramyosin. Southern blot analysis of genomic DNA from the Chinese and Philippine strains of S. japonicum demonstrated strain-related RFLPs at the paramyosin locus, and suggested that more than one copy of the paramyosin gene was present in the S. japonicum genome. PCR-based RFLP analysis which exploited restriction site differences between B6 and Y6 showed that paramyosin genotype B6 was much more common in schistosome populations and verified the existence of introns in the paramyosin gene(s) of S. japonicum.