Production and characterization of antibody against Opisthorchis viverrini via phage display and molecular simulation

In this study, a key issue to be addressed is the safe disposal of hybridoma instability. Hybridoma technology was used to produce anti–O. viverrini monoclonal antibody. Previous studies have shown that antibody production via antibody phage display can sustain the hybridoma technique. This paper presents the utility of antibody phage display technology for producing the phage displayed KKU505 Fab fragment and using experiments in concomitant with molecular simulation for characterization. The phage displayed KKU505 Fab fragment and characterization were successfully carried out. The KKU505 hybridoma cell line producing anti–O. viverrini antibody predicted to bind to myosin was used to synthesize cDNA so as to amplify the heavy chain and the light chain sequences. The KKU505 displayed phage was constructed and characterized by a molecular modeling in which the KKU505 Fab fragment and -O. viverrini myosin head were docked computationally and it is assumed that the Fab fragment was specific to -O. viverrini on the basis of mass spectrometry and Western blot. This complex interaction was confirmed by molecular simulation. Furthermore, the KKU505 displayed phage was validated using indirect enzyme-linked immunosorbent assays (ELISA) and immunohistochemistry. It is worthy to note that ELISA and immunohistochemistry results confirmed that the Fab fragment was specific to the -O. viverrini antigen. Results indicated that the approach presented herein can generate anti–O. viverrini antibody via the phage display technology. This study integrates the use of phage display technology together with molecular simulation for further development of monoclonal antibody production. Furthermore, the presented work has profound implications for antibody production, particularly by solving the problem of hybridoma stability issues.

Mapping the epitopes of Schistosoma japonicum esophageal gland proteins for incorporation into vaccine constructs

BACKGROUND

The development of a schistosome vaccine has proved challenging but we have suggested that characterisation of the self-cure mechanism in rhesus macaques might provide a route to an effective product. The schistosome esophagus is a complex structure where blood processing is initiated by secretions from anterior and posterior glands, achieved by a mixture of ~40 unique proteins. The mechanism of self-cure in macaques involves cessation of feeding, after which worms slowly starve to death. Antibody coats the esophagus lumen and disrupts the secretory processes from the glands, potentially making their secretions ideal vaccine targets.

METHODOLOGY/PRINCIPAL FINDINGS

We have designed three peptide arrays comprising overlapping 15-mer peptides encompassing 32 esophageal gland proteins, and screened them for reactivity against 22-week infection serum from macaques versus permissive rabbit and mouse hosts. There was considerable intra- and inter-species variation in response and no obvious unique target was associated with self-cure status, which suggests that self-cure is achieved by antibodies reacting with multiple targets. Some immuno-dominant sequences/regions were evident across species, notably including: MEGs 4.1C, 4.2, and 11 (Array 1); MEG-12 and Aspartyl protease (Array 2); a Tetraspanin 1 loop and MEG-n2 (Array 3). Responses to MEGs 8.1C and 8.2C were largely confined to macaques. As proof of principle, three synthetic genes were designed, comprising several key targets from each array. One of these was expressed as a recombinant protein and used to vaccinate rabbits. Higher antibody titres were obtained to the majority of reactive regions than those elicited after prolonged infection.

CONCLUSIONS/SIGNIFICANCE

It is feasible to test simultaneously the additive potential of multiple esophageal proteins to induce protection by combining their most reactive regions in artificial constructs that can be used to vaccinate suitable hosts. The efficacy of the approach to disrupt esophageal function now needs to be tested by a parasite challenge.

A novel enolase from Taenia solium metacestodes and its evaluation as an immunodiagnostic antigen for porcine cysticercosis

Cysticercosis is a worldwide parasitic disease of humans and pigs principally caused by infection with the larvae of the pork tapeworm Taenia solium. Through the use of the recently-made-available T. solium genome, we identified a gene within a novel 1448 bp ORF that theoretically encodes for a 433 amino acid-long protein and predicted to be an α-enolase closely related to enolases of other flatworms. Additional bioinformatic analyses revealed a putative plasminogen-binding region on this protein, suggesting a potential role for this protein in pathogenesis. On this basis, we isolated the mRNA encoding for this presumptive enolase from T. solium metacestodes and reverse-transcribed it into cDNA before subsequently cloning and expressing it in both E. coli (rEnoTs) and insect cells (rEnoTsBac), in a 6xHis tagged manner. The molecular weights of these two recombinant proteins were ∼48 and ∼50 kDa, respectively, with the differences likely attributable to differential glycosylation. We used spectrophotometric assays to confirm the enolase nature of rEnoTs as well as to measure its enzymatic activity. The resulting estimates of specific activity (60.000 U/mg) and K_m (0.091 mM) are quite similar to the catalytic characteristics of enolases of other flatworms. rEnoTs also exhibited high immunogenicity, eliciting a strong polyclonal antibody response in immunized rabbits. We subsequently employed rEnoTsBac for use in an ELISA aimed at discriminating between healthy pigs and those infected with T. solium. This diagnostic assay exhibited a sensitivity of 88.4% (95% CI, 74.92%-96.11%) and a specificity of 83.7% (95% CI: 69.29%-93.19%). In conclusión, this study reports on and enzymatically characterizes a novel enolase from T. solium metacestode, and shows a potential use as an immunodiagnostic for porcine cysticercosis.

Subcutaneous injection of exosomes reduces symptom severity and mortality induced by Echinostoma caproni infection in BALB/c mice

Recent studies have shown the importance of exosomes in the host-parasite relationship. These vesicles are an important part of the excretory/secretory pathway for proteins with the potential to alter immune responses. Therefore, in the present study, we examined the immunomodulatory role of exosomes in BALB/c mice using Echinostoma caproni as an experimental model of intestinal helminth infection. For this purpose, BALB/c mice were injected twice s.c. with purified exosomes of E. caproni, followed by experimental infection. We report a delay in the development of the parasite in mice immunised with exosomes, a concomitant reduced symptom severity and increased survival upon infection. Immunisations with exosomes evoked systemic antibody responses with high levels of IgM and IgG. IgG1, IgG2b and IgG3 are the subtypes responsible for the IgG increase. These antibodies showed specific recognition of exosomal proteins, indicating that these vesicles carry specific antigens that are involved in the humoral response. The administration of exosomes induced an increase of IFN-γ, IL-4 and TGF-β levels in the spleen of mice prior to infection. The subsequent infection with E. caproni resulted in a further increase of IL-4 and TGF-β, together with an abrupt overproduction of IL-10, suggesting the development of a Th2/Treg immune response. Our results show that the administration of exosomes primes the immune response in the host, which in turn can contribute to tolerance of the invader, reducing the severity of clinical signs in E. caproni infection.

SCHISTOSOMA-SPECIFIC 26 KDA PROTEIN FOR A DIAGNOSIS OF ACUTE AND CHRONIC SCHISTOSOMIASIS

One of the world wide major public health problems is the schistosomiasis that is caused by Schistosoma (S.) heamatobium. It is also one of the main concerns for the public health community in Egypt. There are several immunodiagnostic methods used for that diagnosis of such disease, but some are more sensitive and specific than others. The purified 26 kDa Schistosoma-specific protein (PSPA-26) detection in serum samples is found out to be more valuable in diagnosis; it also helps in the early diagnosis which will lead to the early treatment before the irreversible damage takes place. PSPA-26 was purified from whole worms by DEAE-Sephadex G-75 ion exchange chromatography and then was injected into rabbits to produce specific polyclonal antibodies (anti-PSPA-26 pAb) which were then used as a primary capture in the indirect ELISA technique to reveal its reactivity using infected human sera. The anti-PSPA-26 was then labeled with horse-radish peroxidase (HRP) and used as a secondary capture. Sandwich ELISA was done for serum samples of human and hamsters infected with S. heamatobium. The results revealed a sensitivity of 85% for human and 80% for hamster's samples, and a specificity of 95% for human and 91.1% for hamsters samples by comparing them with those infected with other parasites and control samples. Data obtained concluded that PSPA-26 antigen can be used as a diagnostic marker for S. haematobium infection using the sandwich ELISA which is cost effective and applicable technique.

Partially Protective Immunity Induced by a 20 kDa Protein Secreted by Trichinella spiralis Stichocytes

Background

Trichinella spiralis infection induces protective immunity against re-infection in animal models. Identification of the antigens eliciting acquired immunity during infection is important for vaccine development against Trichinella infection and immunodiagnosis.

Methods and Findings

The T. spiralis adult cDNA library was immunoscreened with sera from pigs experimentally infected with 20,000 infective T. spiralis larvae. Total 43 positive clones encoding for 28 proteins were identified; one of the immunodominant proteins was 20 kDa Ts-ES-1 secreted by Trichinella stichocytes and existing in the excretory/secretory (ES) products of T. spiralis adult and muscle larval worms. Ts-ES-1 contains 172 amino acids with a typical signal peptide in the first 20 amino acids. The expression of Ts-ES-1 was detected in both the adult and muscle larval stages at the mRNA and protein expression levels. Mice immunized with recombinant Ts-ES-1 (rTs-ES-1) formulated with ISA50v2 adjuvant exhibited a significant worm reduction in both the adult worm (27%) and muscle larvae burden (42.1%) after a challenge with T. spiralis compared to the adjuvant control group (p<0.01). The rTs-ES-1-induced protection was associated with a high level of specific anti-Ts-ES-1 IgG antibodies and a Th1/Th2 mixed immune response.

Conclusion

The newly identified rTs-ES-1 is an immunodominant protein secreted by Trichinella stichocytes during natural infection and enables to the induction of partial protective immunity in vaccinated mice against Trichinella infection. Therefore, rTs-ES-1 is a potential candidate for vaccine development against trichinellosis.

Flow-Through Assay for Detection of Antibodies Using Protein-A Colloidal Gold Conjugate as a Probe

Flow-through assay (FTA) is a rapid, simple-to-perform, cost-effective, and user-friendly diagnostic test for monitoring infections in non-laboratory settings. It is mostly applied for antibody detection. FTA employing protein-A colloidal gold conjugate to detect antibodies against porcine cysticerci using cyst fluid and whole cyst antigens of Taenia solium metacestode is described here. Antibodies in the serum are captured by an antigen spotted onto a nitrocellulose membrane mounted on a flow-through device that serves as the antigen capture matrix. The bound antibodies are visualized by the addition of protein-A colloidal gold conjugate, which imparts a pink color. The test can be completed within 3 min at room temperature without any instrumentation. The sensitivity and specificity of the FTA are in agreement with ELISA.

Brugia pahangi: immunization with early L3 ES alters parasite migration, and reduces microfilaremia and lymphatic lesion formation in gerbils (Meriones unguiculatus)

Previous studies have shown that intradermally (ID) injected Brugia pahangi L3 s migrate through various tissues and into the lymphatics of gerbils in a distinct pattern. Excretory/secretory products (ES) produced at the time of invasion of B. pahangi are likely to be important in this early migration phase of the parasite life cycle in their rodent host. Hence, early L3 ES was collected from 24h in vitro cultures of B. pahangi L3 larvae and used in immunization experiments to investigate the effect of immunity to early L3 ES on worm migration, survival and development of B. pahangi. Immunization of gerbils with ES in RIBI adjuvant produced antibodies to numerous ES proteins eliciting a strong humoral response to ES and indirect fluorescent antibody (IFA) assay using anti-ES serum recognized the ES proteins on the surface of B. pahangi L3 larvae. Following ES immunization, gerbils were challenged either ID or intraperitoneally (IP) with 100 L3 s of B. pahangi and euthanized at 3 or 106 days post inoculation (DPI). Immunization with early ES slowed the migration of ID inoculated L3 at 3 DPI and significantly altered the locations of adult worms at 106 DPI. Immunization did not induce protection in any treatment group. However, immunized animals had significantly fewer microfilariae per female worm suggesting the antigens in ES are important in microfilariae development or survival in the host. The number of lymphatic granulomas was also significantly reduced in ES immunized animals. It is important to note that microfilariae serve as a nidus in these granulomas. Our results shows immunization with early Brugia malayi L3 ES alters the worm migration, affects circulating microfilarial numbers and reduces lymphatic granulomas associated with B. pahangi infection in gerbils.

The infectivity and antigenicity ofToxocara caniseggs can be retained after long-term preservation

Suspensions of fertilized eggs of Toxocara canis were mixed with 2% neutral formalin and preserved at 4 degrees C. When, after storage for 0, 12, 18, 21 and 24 months, samples of the eggs were incubated at 30 degrees C for 12 days, 96.8%, 92.6%, 74.1%, 51.0% and 19.3% of the eggs in the samples were found to embryonate. The embryonated eggs produced from the fertilized eggs preserved (in 2% neutral formalin at 4 degrees C) for 0, 12, 18 and 21 months were then tested for their infectivity to BALB/c mice, each mouse being given 800 embryonated eggs. The numbers of larvae recovered from the mice and the sites from which they were recovered, 2 or 14 days post-infection, appeared unaffected by the length of storage of the eggs. The infected mice all had similar eosinophil counts in their peripheral blood and similar serum titres of Toxocara-specific IgM and IgG antibodies, and cultures of their spleen cells produced similar amounts of interleukin-4, interleukin-5 and interferon-gamma when stimulated with concanavalin A. The results of SDS-PAGE indicated that egg preservation for at least 21 months had no effect on the excretory-secretory antigens in samples of medium from cultures of infective larvae released from the eggs. In summary, at least 50% of the fertilized eggs preserved in 2% neutral formalin at 4 degrees C for 21 months could fully embryonate and then had the same infectivity and antigenicity as embryonated fresh eggs.

Mouse monoclonal antibodies against human urinary protein Sm-UP(2)IP of Schistosoma mansoni

There are innumerable clinical and pathological problems associated with schistosomiasis that have necessitated various control programs. Successful control would naturally depend on effective rapid diagnosis in the field. However, the overlapping distribution of urinary and intestinal schistosomiasis in hyperendemic areas calls for differential diagnosis. This study was aimed at producing anti-Schistosoma mansoni monoclonal antibodies (MAbs) for possible utilization in assays to detect antigens in the urine of infected persons. In order to raise antibodies to less immunogenic urinary parasite antigens, BALB/c mice were immunized with Schistosoma mansoni soluble worm antigens (Sm-SWA) while urinary proteins (Sm-UP(2)IP), isolated from infected human urine samples, was used as a final booster before cell fusion. Hybridoma cells were obtained by the fusion of mouse myeloma and spleen cells from the immunized mice, which were screened by microplate ELISA and then studied further to obtain anti-S. mansoni specific MAbs. The MAbs analyzed presented IgM isotypes. The reactivity of anti-S. mansoni MAbs with Sm-UP(2)IP, 13/43 (30.2%), MAbs showed stronger reactivity. It was observed that one of the MAbs cross-reacted with antigen associated with S. haematobium urinary antigen (Sh-UP(2)IP). Nine (9/13, 69.2%) MAbs recognized glycoprotein antigenic epitopes of Sm-UP(2)IP and Sm-SWA. On the other hand, 4/13 (30.8%) MAbs recognized carbohydrate antigenic epitopes. Band size of 8.9 kDa associated with Sm-UP(2)IP was detected by the 13 MAbs. With Sm-SWA, all the MAbs detected band sizes of 177.8 and 158.5 kDa. In addition, three MAbs recognized a 38.9 kDa band. The generation of anti-S. mansoni species-specific MAbs offers opportunities to develop a specific MAb-based diagnostic tool for use in the field to detect Schistosoma mansoni infection in Ghana.

Roles of partially purified antigens from Gnathostoma spinigerum larvae on antibody production by human B cell culture

A 24 kDa protein from advanced third stage Gnathostoma spinigerum larvae (GsAL3) is used for gnathostomiasis serodiagnosis. This study investigated whether partially purified protein antigen (Ag) from GsAL3 (Gnath Ag), prepared by simple gel filtration chromatography, could be used for serodiagnosis. Using DNA microarray analysis, significant gene expression related to immunoreactivity was examined in peripheral blood mononuclear cells (PBMC) cocultured with Gnath Ag. Antigenicity was then determined by its capacity to induce antibody production among purified naive B cells stimulated with Gnath Ag and anti-CD40. Seven and 14 days post-exposure, immunoglobulin levels (Igs) in culture supernatants were determined by enzyme-linked immunosorbent assay. The Gnath Ag stimulated PBMC had a significant increase in gene expression related to an innate immune response and decreased cell mediated immunity, but the expression of gene related antibody production was not markedly increased. The Gnath Ag stimulated naive B cells or lipopolysaccharide primed B cells to produce low levels of specific antibody. Our findings support the assertion that partially purified Gnath Ag possess low antigenicity for Ig induction. Further studies are needed to improve G. spinigerum larva Ag for serodiagnosis.

[Characterization and preliminary application of six monoclonal antibodies against recombinant signal protein 14-3-3 of Schistosoma japonicum]

OBJECTIVES

To identify the properties of six monoclonal antibodies (McAbs) against recombinant signal protein 14-3-3 of Schistosoma japonicum, and investigate their value in the diagnosis of schistosomiasis.

METHODS

The subclasses, titers, affinity-constants, detection limits and specificities of six McAbs were identified by ELISA and Western blotting. Dot Enzyme-linked Immunosorbent Assay (Dot-ELISA) for detecting the 14-3-3 protein in the sera of rabbits infected with Schistosoma japonicum was established, then it was used to observe the dynamics of 14-3-3 protein in sera of rabbits infected with Schistosoma japonicum before and after treatment. The diagnostic value of Dot-ELISA was investigated through detecting a group of sera samples of rabbits infected with Schistosoma japonicum.

RESULTS

The types of six McAbs against recombinant signal protein 14-3-3 of Schistosoma japonicum of 3F1, 3F7, 5C6, 5D1, 5G9 and 1G6 were all IgG, their subclasses were IgG1, IgG2a, IgG2b, IgG1, IgG1 and IgG1, their antibody-titers in ascites were 1:6.4 x 10(5), 1:8.0 x 10(5) , 1:6.4 x 10(5), 1:3.2 x 10(5), 1:4.8 x 10(5) and 1:2.0 x 10(4), their affinity-constants were 8.82 x 10(8), 4.93 x 10(8), 1.56 x 10(8), 5.12 x 10(8), 1.41 x 10(8) moL/L and 2.30 x 10(7) mol/L, their detection limits in dot-ELISA were 1, 10, 100, 10, 10, 100 ng, respectively. All the six McAbs recognized the recombinant signal protein 14-3-3 of Schistosoma japonicum and the natural signal protein 14-3-3 in SEA, ESA and AWA, and did not react with the protein of E. coli and Clonorchis sinensis in Western blotting. 3F1 and 5D1 were selected to establish the Dot- ELISA for detecting the sera of rabbits infected with Schistosoma japonicum before and after treatment at different time points, it was found that the concentration of 14-3-3 protein in sera of rabbits was increased gradually with time and decreased gradually after the infected rabbits treated with praziquantel. Forty-two sera samples of rabbits infected with Schistosoma japonicum were detected by this Dot-ELISA, 41 samples were positive, the sensitivity was 97.6%, and all of the ten healthy rabbits' sera were negative, the specificity was 100%.

CONCLUSIONS

All the six McAbs could recognize natural signal protein 14-3-3. It has been proved preliminarily that the Dot-ELISA based on 3F1 and 5D1 is valuable for the diagnosis of active infection of Schistosoma japonicum and accessing the chemotherapeutic effect of schistosomiasis.

Immune events associated with high level protection against Schistosoma japonicum infection in pigs immunized with UV-attenuated cercariae

Background

The vaccination of radiation-attenuated Schistosoma japonicum cercariae can induce effective protection in artiodactyl, but the immune events related to protective immunity are not fully understood. To provide a paradigm for a human recombinant antigen vaccine, we have undertaken a vaccination and challenge experiment in pigs, which was recognized as an appropriate animal model in this type of study because of their similarity to human in immunology, and investigated the relative immune events induced by the radiation-attenuated S. japonicum cercariae.

Methods and Findings

We found that pigs immunized once with 400 µw UV-irradiated cercariae exhibited 63.84% and 71.82% reductions in worm burden and hepatic eggs respectively. Protective immunity in vaccinated pigs was associated with high level productions of IgM, total IgG, IgG1 and IgG2; IgG2 was significantly increased in the acute infection. IFN-γ levels could be elicited by immunization. At week 6 post-infection, IFN-γ, IL-4 and IL-10 levels also showed a dramatic rise synchronously in vaccinated pigs. Moreover, the granzyme b, nk-lysin, ifnγ, il4 and il10 mRNA levels in early skin-draining lymph nodes of immunized pigs were higher than those in pigs with non-irradiated cercariae infection. In addition, cytotoxicity-related genes in the mesenteric lymph nodes were significantly upregulated in vaccinated pigs in the acute infection.

Conclusion/Significance

Our results demonstrated that IFN-γ and IgG2 antibody production, as well as genes related to cytotoxicity are associated with the high level protection induced by UV-irradiated Schistosoma japonicum vaccine. These findings indicated that optimal vaccination against S. japonicum required the induction of IFN-γ, IgG2 antibody related to Th1 responses and cytotoxicity effect.

Vaccination against Strongyloides venezuelensis with homologue antigens using new immunomodulators

Control of Strongyloides stercoralis infection is based on antihelminthic treatment. However, the development of an efficient vaccine is an important goal for more effectively managing this disease. Different Strongyloides spp. antigen preparations have been previously tested but without satisfactory results. In the present study, we evaluated whether the doxycholic acid extract of Strongyloides venezuelensis stage 3 larvae was able to protect CD1 mice against a homologue infection. Moreover, we included saponins from Quillaja saponaria (Qs) and immunomodulatory substances, i.e., Phlebodium pseudoaureum hydroalcoholic extract (PAL) or the amino alcohol AA0029, which has an aliphatic chain of 14 carbon atoms with a hydrophilic amino alcohol head, where the amino group is protected with a butoxycarbonyl group. The DOCSv antigen, together with the adjuvant components, was emulsified in a non-mineral water/oil emulsion. We performed duplicate experiments with each of the 2 immunomodulators. The DOCSv antigen used with Qs+PAL induced high levels of protection in terms of fecal egg count reduction (93.2-99.4%), 86-88% in adult worm recovery, and reduction in swelling of the small intestine. Mice vaccinated with the DOCSv antigen, together with Qs+AA0029, showed a 73.7-97.0% reduction in fecal egg count, with reduction in inflammation of the small intestine. High levels of IgG and IgG2a were observed in mice vaccinated with Qs+AA0029+DOCSv, indicating a Th1 immune response. Also, vaccinated mice recognized bands of 34, 39, 43, 95, and 170 kDa in a Western blot.

Intranasal administration of Schistosoma japonicum paramyosin induced robust long-lasting systemic and local antibody as well as delayed-type hypersensitivity responses, but failed to confer protection in a mouse infection model

To investigate intranasal (i.n.) immunization efficacy of Schistosoma japonicum 97-kDa myofibrillar protein paramyosin (PM), a vaccine candidate for Asian schistosomiasis, BALB/c mice were i.n. immunized with Escherichia coli-expressed recombinant PM (rPM). I.n. immunization using rPM mixed with cholera toxin (CT) was more potent than subcutaneous (s.c.) immunization with rPM emulsified in incomplete Freund's adjuvant for induction of serum (IgG, IgE, and IgA) and mucosal (IgA in nose, lung, and intestine) antibody and delayed-type hypersensitivity (DTH) responses. The second i.n. immunization was sufficient to induce maximal serum IgG and DTH responses, which were almost completely maintained for more than 6 months. Next, to evaluate protective efficacy of the rPM against S. japonicum infection, immunized mice were infected with S. japonicum cercariae at 2 weeks after the second immunization. At 7 weeks after infection, we observed no reduction in worm burden or fecundity in both i.n. and s.c. immunized groups. Results showed that i.n. immunization with rPM/CT failed to provide protection against parasite infection, albeit the antigen was a very potent mucosal immunogen. These results may emphasize the need to innovate new mucosal adjuvants or delivery molecules to overcome such hurdles in the construction of a mucosal antiparasite vaccine platform.

Schistosoma mansoni Annexin 2: molecular characterization and immunolocalization

We here describe the cloning and characterization of the Schistosoma mansoni Annexin 2, previously identified in the tegument by proteomic studies, and as an up-regulated gene in schistosomulum stage by microarray data. In silico analysis predicts a conserved core containing four repeat domains of Annexin (ANX) and a variable N-terminal region similar to that described for mammalian isoforms. Real-time RT-PCR and Western blot analysis determined that S. mansoni Annexin 2 is significantly up-regulated in the transition from free-living cercaria to schistosomulum and adult worm parasitic stages. Immunolocalization experiments and tegument membrane preparations confirmed Annexin 2 as a protein mainly localized in the tegument of schistosomula and adult worms. Furthermore, it binds to the tegument surface membranes in a calcium-dependent manner. These results suggest that S. mansoni Annexin 2 is closely associated to the tegument arrangement, being a potential target for immune intervention.

An experimental study for evaluating the efficacy of cercarial vaccine against Schistosoma mansoni

This study assessed the effectiveness of autoclaved cercarial vaccine (ACV) in protection against Schistosoma mansoni infection in 125 Swiss albino mice classified into two main groups: GI: a control group. GII: a test vaccinated with ACV, in a single dose of 0.1 ml of 10(4) ml ACV (G.IIa), double dose; 0.2ml (G.IIb) and two single doses 2 weeks apart (G.IIc). Four weeks later, all mice were challenged with S. mansoni cercariae and sacrificed 10 weeks post infection (P.I.). The results revealed that the vaccine in a single dose (G.IIa) induced a high level of protection against S. mansoni infection. There was a significant reduction in the mean number of adult worm (91.12%), ova/gram liver (91.87%), ova/gram intestine (89.09%) and number & size of granulomas in liver (92.92% & 43.53% respectively). Besides, ACV induced a significant increase in the level of IL-10 mRNA expression as compared to the control group.

Developmental expression analysis and immunolocalization of a biogenic amine receptor in Schistosoma mansoni

A Schistosoma mansoni G-protein coupled receptor (SmGPCR) was previously cloned and shown to be activated by the biogenic amine, histamine. Here we report a first investigation of the receptor's subunit organization, tissue distribution and expression levels in different stages of the parasite. A polyclonal antibody was produced in rabbits against the recombinant third intracellular loop (il3) of SmGPCR. Western blot studies of the native receptor and recombinant protein expressed in HEK293 cells showed that SmGPCR exists both as a monomer (65 kDa) and an apparent dimer of approximately 130 kDa These species were verified by immunoprecipitation of SmGPCR from S. mansoni extracts, using antibody that was covalently attached to agarose beads. Further investigation determined that the SmGPCR dimer was resistant to treatment with various detergents, 4 M urea and 0.1 M DTT but could be made to dissociate at acidic pH, suggesting the dimer is non-covalent in nature. Confocal immunofluorescence studies revealed significant SmGPCR immunoreactivity in sporocysts, schistosomula and adult worms but not miracidia. SmGPCR was found to be most widely expressed in the schistosomula, particularly the tegument, the subtegumental musculature and the acetabulum. In the adult stage we detected SmGPCR immunofluorescence mainly in the tubercles of male worms and, to a lesser extent, the body wall musculature. Localization in sporocysts was mainly confined to the tegument and cells within parenchymal matrices. A real-time quantitative reverse-transcription PCR analysis revealed that SmGPCR is upregulated at the mRNA level in the parasitic stages compared to the free-living miracidium and cercariae, and it is particularly elevated during early sporocyst and schistosomula development. The results identify SmGPCR as an important parasite receptor with potential functions in muscle and the tegument of S. mansoni.

Haplorchis taichui: worm recovery rate and immune responses in infected rats (Rattus norvegicus)

Worm recovery rate, mucosal mast cells (MMCs), eosinophils and serum IgE concentration in rats were investigated after orally feeding 300 Haplorchis taichui metacercariae to male rats. The duodenal, jejunal and ileal tissue sections were stained with 1% alcian blue and 0.5% safranin-O for MMC count. Eosinophil count and the serum IgE concentration assay were measured from cardiac puncture blood. The average worm recovery rates were 20.00%, 13.00%, 0.67%, 1.67% and 0.00% on day 3, 7, 14, 21 and 28 post-infection (PI), respectively. The number of MMCs in the infected rats were significantly higher than in the controls (P<0.01), reaching a peak on day 21 PI. They decreased thereafter, with the decline in worm recovery. Eosinophil count and Serum IgE concentration were also increased but not significantly higher than the controls. However, they showed a positive relationship to worm recovery. It could be concluded from the results that MMCs, eosinophils and IgE may play an important role in the expulsion of H. taichui from rat intestine. However, the mechanism by which the MMC result in the helminth expulsion still need to be understood, and it is recommended that other cells such as goblet cells be studied further.

Trichinella spiralis: Characterization of phage-displayed specific epitopes and their protective immunity in BALB/c mice

Trichinellosis is a global zoonosis mainly caused by Trichinella spiralis. We have previously reported that a novel Ts87 gene from the cDNA library of adult T. spiralis was cloned and expressed in a prokaryotic expression system. Vaccination with recombinant Ts87 protein (rTs87) induced a muscle larvae burden reduction in BALB/c mice by 29% in response to T. spiralis infection. In the present study, we screened a random phage-displayed peptide library using monoclonal antibody 5A3 which recognized Ts87 protein. Four positive phage clones were selected to subcutaneously immunize BALB/c mice without adjuvant. Two phage clones could effectively stimulate specific antibodies against rTs87. Mice vaccinated with these two combined phage clones showed a 28.7% worm burden reduction as compared to the control group. Therefore, the identified phage clones displayed peptides representing specific epitopes of Ts87 protein and could be considered as potential vaccine candidates for T. spiralis.

[Recent advances in the immunodiagnosis of human cystic echinococcosis]

Human cystic echinococcosis is a severe zoonotic infection caused by the larval stage of the taeniid tapeworm Echinococcus granulosus. The infection may be fatal if proper treatment is not provided; hence, early diagnosis is very important. Currently, ELISA and immunoblotting are the most reliable tests for serodiagnostic purposes, although their accuracy is largely dependent on the quality of the antigenic source used. Hydatid cyst fluid has been the antigenic extract of choice for primary immunodiagnosis of the disease, which is mainly based on the detection of antigens B and 5. Several problems are associated with this extract, however, including a lack of sensitivity and specificity, and difficulties with standardization of its use. This paper reviews recent advances in the identification and characterization of novel antigens that may be useful for the immunodiagnosing of human cystic echinococcosis, with emphasis on progress in recombinant technologies and synthetic peptides. Novel approaches are discussed, such as the design of antigenic extracts from other developmental stages of the parasite, as well as the usefulness of serum cytokine detection in the clinical follow-up of affected patients after surgical or pharmacological treatment.

Antibodies elicited by the bovine lungworm, Dictyocaulus viviparus, cross-react with platelet-activating factor

Parasite N-glycans may play an important role in helminth infections. As antibodies from Dictyocaulus viviparus-infected calves strongly react with N-glycans, we investigated the characteristics of the major immunodominant glycoprotein (GP300) of this parasite. Probing of worm extracts with various lectins demonstrated unique binding of GP300 to wheat germ agglutinin. Analysis of lectin-purified GP300 revealed that the glycan was substituted with phosphorylcholine and reacted with the phosphorylcholine-specific antibody TEPC-15. Competitive enzyme-linked immunosorbent assay with GP300-coated plates and GP300-specific immunoglobulin G (IgG) in conjunction with free phosphorylcholine or TEPC-15 demonstrated that antibodies from infected calves recognized phosphorylcholine on GP300. Additional assays showed that these antibodies cross-reacted with the phosphorylcholine moiety present on platelet-activating factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine), a proinflammatory mediator of the host. Heavily infected calves contained high levels of serum GP300-specific IgG1 but low levels of IgA and IgG2 and showed a reduced influx of eosinophils in the lungs, all consistent with a neutralization of PAF activity. In conclusion, we demonstrated that D. viviparus infection elicits GP300-specific antibodies that cross-react with PAF and may neutralize PAF function, thus limiting the development of a protective response as well as parasite-induced host pathology.

Onchocerca volvulus-specific antibody and cytokine responses in onchocerciasis patients after 16 years of repeated ivermectin therapy

The recommended control option against onchocerciasis is repeated ivermectin treatment, which will need to be implemented for decades, and it remains unknown how repeated ivermectin therapy might affect immunity against Onchocerca volvulus in the long term. O. volvulus-specific antibody reactivity and cellular cytokine production were investigated in onchocerciasis patients receiving ivermectin (150 microg/kg) annually for 16 years. In treated patients, the T helper type 2 (Th2) cytokine interleukin (IL)-5 and T regulatory IL-10 in response to O. volvulus antigen (OvAg) and bacteria-derived Streptolysin O (SL-O) diminished to levels found in infection-free endemic controls; also, cellular release of Th1-type interferon (IFN)-gamma at 16 years post initial ivermectin treatment (p.i.t.) approached control levels. In ivermectin-treated onchocerciasis patients, IL-5 production in responses to the mitogen phytohaemagglutinin (PHA) decreased, but IL-10 in response PHA increased, and neither attained the cytokine production levels of endemic controls. At 16 years p.i.t., O. volvulus-specific IgG1 and IgG4 subclass reactivity still persisted at higher levels in onchocerciasis patients than in O. volvulus exposed but microfilariae-free endemic controls. In addition, cytokine responses remained depressed in onchocerciasis patients infected concurrently with Mansonella perstans and Necator americanus or Entamoeba histolytica/dispar. Thus, long-term ivermectin therapy of onchocerciasis may not suffice to re-establish fully a balanced Th1 and Th2 immune responsiveness in O. volvulus microfilariae-negative individuals. Such deficient reconstitution of immune competence may be due to an as yet continuing and uncontrolled reinfection with O. volvulus, but parasite co-infections can also bias and may prevent the development of such immunity.

Molecular characterization of two myoglobins of Paragonimus westermani

Myoglobins (Mbs), globin proteins, are present in high concentrations in trematodes. In Paragonimus westermani, 2 cDNAs were found to encode Mbs. The first clone, Pwmyo1, codes a total of 149 amino acids with a calculated mass of 16.6 kDa. The second, Pwmyo2, encodes a 146-amino acid protein with a calculated mass of 16.2 kDa. The predicted secondary structures showed the presence of 8 helices, which is the basic characteristic of Mbs. Sequence alignment revealed a high homology with the other trematode Mbs. The 2 clones contained the characteristic tyrosyl residues at helical positions B10 and distal E7, which are substitutions that have been previously shown to contribute to the high oxygen affinity of Mbs. Polyclonal antibodies against the recombinant Mbs were raised with no cross-reactivity observed. Immunolocalization revealed the proteins to be distributed generally throughout the parenchymal tissues, but absent from the tegument and reproductive organs. The cell mass of the eggs of the worm stained positive to Pwmyo2 but not Pwmyo1, suggesting the stage-specific expression of these Mbs.

Brugia malayi: comparison of protective immune responses induced by Bm-alt-2 DNA, recombinant Bm-ALT-2 protein and prime-boost vaccine regimens in a jird model

Immunization of jirds with Bm-alt-2 elicited partial protection against challenge infection with the filarial parasite Brugia malayi. In this study, we initially compared the protective immune responses elicited following immunization with recombinant Bm-ALT-2 protein regimen and Bm-alt-2 DNA regimen. These studies showed that protein vaccination conferred approximately 75% protection compared to DNA vaccination that conferred only 57% protection. Analysis of the protective immune responses showed that the protein immunization promoted a Th2-biased response with an increase in IL-4, IL-5 and IgG1 responses, whereas, the DNA vaccine promoted a Th1-biased response with profound IFN-gamma and IgG2a responses. Since protein vaccination gave better results than DNA vaccination, we then wanted to evaluate whether a prime-boost vaccination that combined DNA prime and protein boost will significantly increase the protective responses induced by the protein vaccine. Our results suggest that prime-boost vaccination had no added advantage and was comparatively less effective (64% protection) than the Bm-ALT-2 protein alone vaccination. Prime boost vaccination generated mixed Th1/Th2 responses with a slightly diminished Th2 responses compared to protein vaccination. Thus, our results suggest that Bm-ALT-2 protein vaccination regimen may be slightly better than prime-boost vaccine regimen and the mechanism of protection appears to be largely mediated by a Th2-biased response.

Cross-reactivity induced by Anisakis simplex and Toxocara canis in mice

The aim of this study was to verify whether cross-reactivity appeared between Toxocara canis and Anisakis simplex in an experimental rodent model. No cross-reactions were detected using sera from mice infected with T. canis eggs. When responses obtained against T. canis ES antigen using sera from BALB/c and C57BL/10 mice infected with T. canis eggs were compared with those obtained by testing sera from mice infected with one A. simplex L3, an increase in cross-reactions was observed using the C57BL/10 strain.

Trichinella spiralis: Strong antibody response to a 49kDa newborn larva antigen in infected rats

In this work, we analyzed the kinetics of anti-Trichinella spiralis newborn larva (NBL) antibodies (Ab) and the antigenic recognition pattern of NBL proteins and its dose effects. Wistar rats were infected with 0, 700, 2000, 4000 and 8000 muscle larvae (ML) and bled at different time intervals up to day 31 post infection (p.i.). Ab production was higher with 2000 ML dose and decreased with 8000, 4000 and 700 ML. Abs were not detected until day 10, peaked on day 14 for the 2000 ML dose and on day 19 for the other doses and thereafter declined slowly from 19 to 31 days p.i. In contrast, Abs to ML increased from day 10, peaked on day 19 and remained high until the end of the study. Abs bound strongly at least to three NBL components of 188, 205 and 49 kDa. NBL antigen of 188 and 205 kDa were recognized 10-26 days p.i. and that of 49 kDa from day 10 to day 31 p.i. A weak recognition towards antigens of 52, 54, 62 and 83 kDa was also observed during the infection. An early recognition of 31, 43, 45, 55, 68 and 85 kDa ML antigens was observed whereas the response to those of 43, 45, 48, 60, 64 and 97 kDa (described previously as TSL-1 antigens) occurred late in the infection. A follow-up of antigen recognition up to day 61 with the optimal immunization dose (2000 ML) evidenced a decline of Ab production to the 49 kDa NBL antigen 42 days p.i., which suggested antigenic differences with the previously reported 43 kDa ML antigen strongly recognized late in the infection. To analyze the stage-specificity of the 49 kDa NBL antigen, polyclonal antibodies (PoAb) were obtained in rats immunized with 49 kDa NBL antigen. PoAb reacted strongly with the 49 kDa NBL component in NBL total soluble extract but no reactivity was observed with soluble antigen of the other T. spiralis stages. Albeit with less intensity, the 49 kDa component was also recognized by PoAb together with other antigens of 53, 97 and 107 kDa, in NBL excretory-secretory products (NBL-ESP). Thus, our results reveal differences in the kinetics of anti-NBL and ML Ab responses. While anti-NBL Abs declined slowly from day 19 until the end of the experiment, Abs to ML antigen remained high in the same period. It is remarkable the optimal Ab response to NBL antigens with 2000 ML infective dose and the reduced number of NBL antigens identified throughout the experimental T. spiralis infection, standing out the immunodominant 49 kDa antigen. Interestingly, this antigen, which was prominently expressed in NBL somatic proteins, was also detected in NBL-ESP.

THE USE OF MM3 MONOCLONAL ANTIBODIES FOR THE EARLY IMMUNODIAGNOSIS OF OVINE FASCIOLIASIS

This study reports a new capture ELISA (MM3-SERO) for the serodiagnosis of sheep fascioliasis, based on the use of the monoclonal antibody (mAb) MM3. Like our previously reported indirect ELISA method, based on the use of a FPLC-purified fraction (fraction IV) of the Fasciola hepatica excretion/secretion antigens (ESAs), this new test was able to detect animals infected with very small numbers of metacercariae (5-40) and showed no cross-reaction with sera from sheep infected with other parasites, i.e., Moniezia spp., Cysticercus tenuicollis, and Dicrocoelium dendriticum. In contrast with these 2 methods, some sera (mainly those obtained from animals infected with D. dendriticum) showed high reactivities in indirect ELISA with whole F. hepatica ESAs used as control. Interestingly, the MM3-SERO ELISA has a better signal-to-noise ratio than the fraction-IV ELISA, thus allowing detection of seroconversion in infected sheep on average 1 wk earlier (3.2 +/- 0.4 wk postinfection [PI] for MM3-SERO ELISA vs. 4.2 +/- 0.9 wk PI for fraction IV ELISA). Moreover, the antibody response detected with MM3-SERO ELISA was more uniform, with seroconversion always occurring at 4 wk PI in sheep with 1-2 flukes and at 3 wk PI in sheep with more than 2 flukes. The MM3-SERO ELISA was also used to evaluate the kinetics of antibody response against MM3-recognized antigens in sera from sheep experimentally infected with F. hepatica and then treated with triclabendazole. Our results showed that antibody levels dropped by about 25% during the 4-wk observation period following the flukicide treatment, whereas they remained invariably high in all sheep left untreated. We conclude that the MM3-SERO ELISA is a 100% sensitive and 100% specific test for the early serodiagnosis of sheep fascioliasis. Preliminary studies in our laboratory seem to indicate that this method may also be useful for the determination of anti-F. hepatica antibodies in serum and milk of other ruminants. A commercial version of MM3-SERO is currently available from BIO X Diagnostics (La Jemelle, Belgium).

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.

Experimental Fasciola hepatica infection alters responses to tests used for diagnosis of bovine tuberculosis

Fasciola hepatica is a prevalent helminth parasite of livestock. Infection results in polarization of the host's immune response and generation of type 2 helper (Th2) immune responses, which are known to be inhibitory to Th1 responses. Bovine tuberculosis (BTB) is a bacterial disease of economic and zoonotic importance. Control polices for this disease rely on extensive annual testing and a test-and-slaughter policy. The correct diagnosis of BTB relies on cell-mediated immune responses. We established a model of coinfection of F. hepatica and Mycobacterium bovis BCG to examine the impact of helminth infection on correct diagnosis. We found the predictive capacity of tests to be compromised in coinfected animals and that F. hepatica infection altered macrophage function. Interleukin-4 and gamma interferon expression in whole-blood lymphocytes restimulated in vitro with M. bovis antigen was also altered in coinfected animals. These results raise the question of whether F. hepatica infection can affect the predictive capacity of tests for the diagnosis of BTB and possibly also influence susceptibility to BTB and other bacterial diseases. Further studies on the interplay between helminth infection and BTB are warranted.

Studies on the protective immunity of Schistosoma japonicum bivalent DNA vaccine encoding Sj23 and Sj14

In order to explore the high performance bivalent DNA vaccine of Schistosoma japonicum, the fatty-acid-binding protein (Sj14) and the 23 kDa transmembrane protein (Sj23) two proteins were selected to construct the DNA-based vaccine. It was successful to construct a bivalent DNA vaccine using three strategies: the co-expression of two genes, a fusion gene expression and two kinds of plasmids in combination (cocktail vaccine). The bivalent DNA was proven to express well in vitro and in vivo by indirect immunofluorescence test (IIF) and reverse transcriptase-polymerase chain reaction (RT-PCR). The protective immunity of bivalent DNA vaccine was higher than that of univalent DNA vaccine (p<0.05). There were four groups of bivalent vaccine whose protective immunity was higher than 50%. Granuloma diameter reduction rates were in the range of 18-39%. There was no significant impact on immunity protection exerted by the four factors including dosage, inoculated times, inoculated routes and challenge time after the last immunization in three levels (p>0.05).

Cytokine and antibody subclass responses in the intestinal lymph of sheep during repeated experimental infections with the nematode parasite Trichostrongylus colubriformis

The expression of interleukin (IL)-4, IL-5, IL-10, IL-13, TNF-alpha and IFN-gamma genes, and parasite-specific IgM, IgG1, IgG2, IgA and total IgE levels, were monitored daily in intestinal lymph of sheep infected repeatedly with the nematode parasite Trichostrongylus colubriformis. Host genotype had a significant influence on IL-13 gene activity, with resistant-line (R) sheep consistently expressing higher levels of mRNA than susceptible-line (S) sheep. Mean gene expression of IL-13, IL-4 and IFN-gamma did not differ significantly between the first and second nematode challenge. Field-primed R and S as well as field-primed R and naïve S sheep had lower mean gene expression of IL-5 and IL-10, respectively, during the second when compared to primary challenge. Genes for IL-13 and IL-5 were transiently and strongly up-regulated after nematode infection, particularly in animals with previous exposure to nematodes. Genes for TNF-alpha and IFN-gamma were also transiently up-regulated, but to a lesser extent and more typically after primary challenge. Naïve sheep of both genotypes produced relatively little antibody response after primary challenge. A second nematode challenge resulted in large increases in the lymphatic levels of all antibody sub-classes which were significant for adult antigen-specific IgA and larval antigen-specific IgG1. In naïve S line sheep, the larval-specific IgA and IgG2 response appeared delayed when compared to the R line animals. Field-primed R and S line sheep had relatively high lymphatic IgG1 levels prior to experimental infection and these did not change significantly afterwards. These results demonstrate that during nematode infections, the intestinal micro-environment of sheep is transiently skewed towards Th2 cytokine dominance, although IFN-gamma gene expression continues. This response is accompanied by increases of nematode-specific IgG1, IgA, IgG2 and IgM, as well as of total IgE in lymph plasma.

Classification of the parenchymal cells in Fasciola gigantica based on ultrastructure and their expression of fatty acid binding proteins (FABPs)

Parenchymal cells in adult Fasciola gigantica can be classified into three types based on their ultrastructural features and different quantities of fatty acid binding protein (FABP) being stored. Parenchymal cell type 1 (Pc1) has pale cytoplasm consisting largely of a loose network of fine fibers, and it contains few mitochondria but numerous glycogen particles. This cell type may be specialized in the storage and metabolism of glycogen and glucose. Parenchymal cell type 2 (Pc2) has similar cytoplasmic features as Pc1 but contains more numerous mitochondria, and high concentration of FABP as reflected by high density of immunostaining and immunogold labeling using specific monoclonal antibody (MoAb) to FABP as probe. Pc2 may, thus, specialize in the storage and metabolism of fatty acids and other lipids. Parenchymal cell type 3 (Pc3) has dense cytoplasm containing large amount of rough endoplasmic reticulum, Golgi complex and mitochondria, which is typical of a secretory cell. Furthermore, Pc3 has very little glycogen particles and is not stained by MoAb against FABP. It could, thus, be concerned with the synthesis of fibers, which form the scaffold of the parenchyma.

Swine infection with Trichinella spiralis: Comparative analysis of the mucosal intestinal and systemic immune responses

The immune protective response developed by swine against Trichinella spiralis is not yet fully understood, particularly at the mucosal level. This study aimed to characterise intestinal immunity to T. spiralis by comparison with the systemic response in specifically pathogen-free pigs. For this purpose, the kinetics of cytokine and antibody production were assessed in the intestinal mucosa and serum of swine infected with T. spiralis for up to 60 days post-infection (dpi). An ex vivo model of jejunum mucosa culture was used to collect the supernatant as a source of antibodies (Abs). Mucosal antibodies were observed by Western blot from 15 dpi, while serum antibodies were expressed from 20 dpi. Both sources of antibodies initially recognized a 110 kDa protein, followed by the identification of 35, 43/46 and 55/59 kDa proteins. IgG1 and IgA antibodies were strongly expressed within the mucosa. The expression levels of Type 1 (IFN-gamma, IL-12), Type 2 (IL-4, IL-6), pro-inflammatory (TNF-alpha) and regulatory (IL-10, TGF-beta) cytokines were assessed by RT-PCR in the intestinal mucosa and spleen. Both IL-10 and IFN-gamma mRNA levels were increased in mucosa, whereas IL-6 and IL-12 mRNA were expressed in spleen. Taken together, these results demonstrated a mixed Type 1/Type 2 profile, the Type 2 profile being dominant in the mucosa.

Toxocara canis: effect of inoculum size on pulmonary pathology and cytokine expression in BALB/c mice

Infection of mice with Toxocara canis results in pulmonary inflammation and the induction of a Th2 type of immune response. The aim of this study was to determine whether the effect of infection with this nematode depends on the inoculum size. Results indicate that mice infected with either a high or a low inoculum size showed, in a dose-dependent manner, pulmonary inflammation with eosinophil infiltration, increased levels of total IgE, and Toxocara-specific IgG1 that persisted up to 60 days p.i. Relative quantification of cytokine expression in lungs of mice infected with different doses showed proportional increased expression of the IL-4, IL-5, and IL-10 transcripts, whereas the expression of the IFN-gamma transcript was not different from that of uninfected controls. These results indicate that infection of BALB/c mice with T. canis results in chronic pulmonary inflammation and a dominant Th2 type of immune response, independent of the inoculum size.

Previous or ongoing schistosome infections do not compromise the efficacy of the attenuated cercaria vaccine

A current or previous schistosome infection might compromise the efficacy of a schistosome vaccine administered to humans. We have therefore investigated the influence of infection on vaccination, using the baboon as the model host and irradiated Schistosoma mansoni cercariae as the vaccine. Protection, determined from worm burdens in test and controls, was not diminished when vaccination was superimposed on a chronic infection, nor was it diminished when it followed a primary infection terminated by chemotherapy. Protection was also assessed indirectly based on fecal egg output and circulating antigen levels, as would be the case in human vaccine trials. In almost all instances, these methods overestimated protection, sometimes with discrepancies of >20%. The overwhelming immune response to egg deposition in infected animals made it difficult to discern a contribution from vaccination. Nevertheless, the well-documented immunomodulation of immune responses that follows egg deposition did not appear to impede the protective mechanisms elicited by vaccination with attenuated cercariae.

Localization of Brugia malayi (sub-periodic) adults in different organs of Mastomys coucha and its influence on microfilaraemia and host antibody response

Lymphatic filariasis caused by nematode parasites Wuchereria bancrofti or Brugia malayi is a spectral disease and produces wide range of immune responses and varying levels of microfilaraemia in infected individuals. The relationship between the immune response of host and the developmental stage of the parasite as well as the microfilariae (mf) density and specific location of the adult worms is yet to be understood. As an experimental model, B. malayi adapted in the experimental animal Mastomys coucha has been used widely for various studies in filariasis. The present study was to assess microfilaraemia as well as the humoral immune response of M. coucha during various stages of B. malayi development and their localization in different organs. The result showed that the density of mf in the circulating blood of the experimental animal depended upon the number of female worms as well as the location and co-existence of male and female worms. The mf density in the blood increased with the increase in the number of females. The clearance of inoculated infective stage (L3) or single sex infection or segregation of male and female to different organs of infected host resulted in a microfilaraemic condition. With respect to antibody response, those animals cleared L3 after inoculation and those with adult worm as well as mf showed low antibody levels. But those with developmental fourth stage and/or adult worms without mf showed significantly higher antibody levels.

Regulation of Anaphylactic IgG1 Antibody Production by IL-4 and IL-10

BACKGROUND

Different cytokines have been implicated in the regulation of isotype expression in primary and secondary antibody responses. The aim of this study was to assess the regulation of anaphylactic IgG1 and IgE antibodies by IL-4, IL-10 and IFN-gamma at different time points of the antibody response against PI, an immunosuppressive fraction of Ascaris suum extract, and ovalbumin (OVA).

METHODS

Wild-type or cytokine-deficient C57BL/6 or BALB/c mice were immunized with PI or OVA in different adjuvants. Twenty days later, they were boosted with the respective antigen. IgG1 and IgE antibodies produced during primary and secondary responses were measured by passive cutaneous anaphylaxis.

RESULTS

PI induced low levels of anaphylactic IgG1 antibodies in the primary response and moderate levels after the antigenic booster, which were IL-4-dependent. In the absence of IL-10 and IFN-gamma, PI-specific IgG1 and IgE enhanced significantly, indicating that these cytokines downregulated antibody production in primary and secondary responses. The IgG1 response to OVA in aluminium hydroxide or complete Freund's adjuvant was IL-4-dependent in the beginning of the primary response. Later on, it became only partially regulated by IL-4 in C57BL/6 mice and IL-4-independent in Th2-prone BALB/c mice. In contrast, IgE antibodies depended exclusively upon IL-4 during the entire time course.

CONCLUSIONS

These results indicate, first, that the IL-4 dependency of anaphylactic IgG1 antibody production, mainly in the secondary response, varies among mouse strains, and, second, that the nature of the antigen determines whether IL-10 and IFN-gamma limit the potential to make large amounts of anaphylactic IgG1 and IgE.

Carriage of DRB1*13 is associated with increased posttreatment IgE levels against Schistosoma mansoni antigens and lower long-term reinfection levels

Praziquantel treatment for Schistosoma mansoni infection enhances Th2 responsiveness against parasite Ags, but also increases the variance in Ab isotype levels. This effect may arise partly from genetic heterogeneity. In this study, associations between HLA polymorphisms at three loci (HLA-DQB1, HLA-DQA1, and HLA-DRB1) and posttreatment Ig responses to S. mansoni Ags were assessed in 199 individuals aged 7-50 years from Uganda. Blood samples were assayed for IgG1, IgG4, and IgE levels against soluble worm Ag (SWA), soluble egg Ag, tegument Ag, and a recombinant tegumental Ag (rSm 22.6) 7 wk after treatment. Multivariate ANOVA analysis initially revealed associations between carriage of DRB1*13 and increased levels of IgG1, IgG4, and IgE against SWA, tegument Ag, and rSM22.6. Subsequent analysis of covariance, which controlled for correlations between isotype levels and also included pretreatment IL-4, IL-5, and IL-13 responsiveness against SWA as covariates, revealed an independent association only between DRB1*13 and a factor score summarizing IgE levels to worm-derived Ags, which was strongest in adults. A post hoc age- and sex-stratified analysis revealed lower reinfection intensities at 1 year, 22 mo, and 6 years after the first round of treatment among carriers of DRB1*13. These results indicate that genetic background has a prominent influence on the posttreatment Th2 immune response to S. mansoni Ags, as well as a downstream association with long-term reinfection levels.

Filarial-specific antibody response in East African bancroftian filariasis: effects of host infection, clinical disease, and filarial endemicity

The effect of host infection, chronic clinical disease, and transmission intensity on the patterns of specific antibody responses in Bancroftian filariasis was assessed by analyzing specific IgG1, IgG2, IgG3, IgG4, and IgE profiles among adults from two communities with high and low Wuchereria bancrofti endemicity. In the high endemicity community, intensities of the measured antibodies were significantly associated with infection status. IgG1, IgG2, and IgE were negatively associated with microfilaria (MF) status, IgG3 was negatively associated with circulating filarial antigen (CFA) status, and IgG4 was positively associated with CFA status. None of the associations were significantly influenced by chronic lymphatic disease status. In contrast, IgG1, IgG2, and IgG4 responses were less vigorous in the low endemicity community and, except for IgG4, did not show any significant associations with MF or CFA status. The IgG3 responses were considerably more vigorous in the low endemicity community than in the high endemicity one. Only IgG4 responses exhibited a rather similar pattern in the two communities, being significantly positively associated with CFA status in both communities. The IgG4:IgE ratios were higher in infection-positive individuals than in infection-negative ones, and higher in the high endemicity community than in the low endemicity one. Overall, these results indicate that specific antibody responses in Bancroftian filariasis are more related to infection status than to chronic lymphatic disease status. They also suggest that community transmission intensity play a dominant but subtle role in shaping the observed response patterns.

Eosinophil and IgA responses in sheep infected with Teladorsagia circumcincta

Infections of sheep with the gastrointestinal nematode Teladorsagia circumcincta are characterised by increased concentrations of IgA, eosinophilia and mastocytosis but the interactions between these immune responses are unclear. We investigated the kinetics of the parasite-specific IgA and eosinophil responses in controlled infections in lambs to determine if there were any associations with subsequent worm growth and survival. IgA and eosinophil responses had very similar kinetics and variation in both responses accounted for more of the variation in adult worm length than either trait alone suggesting that IgA and eosinophils interact in regulating the growth of T. circumcincta. Curiously, those animals with higher peak eosinophil responses had longer worms at slaughter emphasising the intriguing complexity of the immune responses to these parasitic infections.

Human antibody responses of patients living in endemic areas for schistosomiasis to the tegumental protein Sm29 identified through genomic studies

Surface proteins of schistosomes are exposed to host tissues and thus present as potential candidate molecules for the development of new intervention strategies. Herein, we have identified a new tegumental protein of Schistosoma mansoni, termed Sm29. In silico analysis revealed a signal peptide, three glycosylation sites and a transmembrane region on Sm29 amino acid sequence. Sm29 transcription in mammalian developmental stages cDNA libraries of S. mansoni was verified by PCR using specific primers for Sm29 nucleotide sequence and it revealed the presence of transcripts in schistosomula and adult worm stages of the parasite. Sm29 (40-169) fragment was produced in Escherichia coli and purified by affinity chromatography to be used in the immunological assays. Confocal microscopy confirmed bioinformatic studies, revealing that Sm29 is a membrane-bound protein localized on the tegument of S. mansoni adult worm. ELISA was performed using rSm29 protein to investigate the antibody isotype profile to Sm29 in sera of patients living in endemic areas for schistosomiasis. IgG1 and IgG3 subclass antibodies to rSm29 were predominant in sera of individuals naturally resistant to infection and resistant to re-infection whereas low levels of IgM, IgA or IgE were measured. Since, IgG1 and IgG3 are involved in parasite killing and in protective immunity the findings reported here suggest the use of Sm29 as a potential candidate vaccine against schistosomiasis.

Analysis of the IgG antibody response against Paramphistomidae trematoda in naturally infected cattle. Application to serological surveys

The IgG antibody response to Calicophoron daubneyi (Digenea: Paramphistomidae) excretory/secretory antigens was evaluated in naturally infected cattle from Lugo (Galicia, NW Spain) by using an ELISA procedure. Two studies were conducted, first a survey in 524 cattle separated into three groups according to age, G-1 (0-2 years old), G-2 (3-5 years old) and G-3 (> 6 years old). In the second study, three groups of cattle were employed: G-I, naturally infected; G-T, naturally infected and treated with oxyclozanide plus levamisole (Nilzan Plus); G-C, cattle maintained in a farm where C. daubneyi has never diagnosed. Variations on egg-output and haematic parameters (erythrocytes, haematocrite, leukocytes and lymphocytes) were also analyzed. The ELISA procedure showed that 61.2% of the cattle in the first study had been exposed to the trematode, but only 10.1% passed eggs in the feces. Age-association with egg-output was shown but not with the IgG values. In the second experiment, the administration of the anthelmintic reduced significantly the IgG kinetic levels and the C. daubneyi-egg-output was suppressed during 12 weeks in the G-T group. The values of red cells, haematocrite, leukocytes and lymphocytes increased significantly in the treated cattle 5 weeks after chemotherapy; however, new reduction after week 5 was recorded, as results of the challenge of these cattle. This is the first investigation in which evaluation of the IgG humoral response against C. daubneyi in cattle has been carried out. We proved that a notable IgG response in naturally infected cattle is induced, and can be detected by using an ELISA procedure. The IgG antibodies did not increase after challenge infection. Our results proved an important percentage of cattle were exposed to this trematode in the area of study and suitable measures for preventing this relationship must be considered.

Application of adult worm and lung-stage antigens to immunize against Schistosoma mansoni using cytokines as adjuvants

Different Schistosoma mansoni antigens; adult worm antigen (SWAP) and lung-stage antigen (SLAP) together with different cytokine adjuvants (Interferon-gamma and Interleukin-4) were used to immunize mice against. S. mansoni. Immunization program was directed towards the production of an intense immune response together with balanced T-helper1 and T-helper2 immune responses. The goal of immunization was not only to protect from infection but also to modulate the pathology inflicted by the parasite. Parameters like adult load, egg counts, anti-Schistosoma antibody titers and liver pathology were used to evaluate the different immunization scheme. SLAP antigen has proven to be a better antigen not only in protection but also in pathology modulation. SLAP plus IFN-gamma as an adjuvant was the best immunization regimen with almost 50% protection and a remarkable resolving of parasite pathology. Unexpectedly, IL-4 had a weak but observed adjuvant protective effect. The results is a step in the path for a Schistosoma vaccine that guides the immune system towards a balanced response targeting the pathology induced by the parasite rather than the parasite itself.

Identification of a 66 kDa Haemonchus contortus excretory/secretory antigen that inhibits host monocytes

A 66 kDa adult Haemonchus contortus excretory/secretory (E/S) antigen was identified in Western blot by reaction with sera from the infected goats. The protein was purified from the adult worm extract and E/S products by anion exchange and ConA-Sepharose chromatography. The purified protein inhibited monocyte function in vitro as judged by decreased production of hydrogen peroxide and nitric oxide in the culture medium. The protein also caused proliferation of peripheral blood mononuclear cells. The absence of protein in the free living L3 larvae suggests that the expression of this protein coincides with the adaptation to the parasitic life. A correlation of antibody titre and worm burden was observed in the infected goats with higher antibody levels in high worm burdened animals. Anti-protein antibody caused loss of adult worm motility in vitro resulting in the death of the parasite. The fact that the protein is recognized by the host together with in vitro killing of adult parasites by antibodies makes this protein a promising candidate for vaccination trial.

Natural IgE Production in the Absence of MHC Class II Cognate Help

IgE induction by parasites and allergens is antigen driven and cognate T cell help dependent. We demonstrate that spontaneously produced IgE in T cell-deficient and germ-free wild-type (wt) mice is composed of natural specificities and induced by a mechanism independent of MHC class II (MHC II) cognate help. This does not require secondary lymphoid structures or germinal center formation, although some bystander T cell-derived IL-4 is necessary. The pathway of spontaneous IgE production is not inhibited by regulatory T cells and increases with age to constitute significant serum concentrations, even in naive animals.

A DNA Vaccine Encoding a Fatty Acid-Binding Protein of Clonorchis sinensis Induces Protective Immune Response in Sprague-Dawley Rats

Clonorchis sinensis, the Chinese liver fluke, resides chronically in the biliary tract, and fatty acid-binding protein (FABP) is known to play an important role in the intracellular transport of long-chain fatty acids obtained from the host. Although FABP has stimulated considerable interest as a vaccine candidate, the nature of C. sinensis FABP (CsFABP) remains unclear. We investigated the immunogenicity and protective efficacy of a DNA vaccine encoding CsFABP. The intradermal injection of plasmid DNA carrying the CsFABP gene (pcDNA3.1-FABP) into Sprague-Dawley (SD) rats induced both humoural and cellular immune responses. Animals injected with pcDNA3.1-FABP developed FABP-specific antibody, which is dominance of IgG2a in sera. In addition, the DNA vaccine elicited the production of IFN-gamma, but not the production of IL-4 in spleen cells stimulated with recombinant FABP. Moreover, pcDNA3.1-FABP induced a significant level of protection, decreased worm burden (40.9%, P<0.05) in SD rats against C. sinensis metacerariae challenge. These results suggest that pcDNA3.1-FABP induces a typical T helper-1-dominated immune response and it is a good candidate for use in future clonorchiasis vaccination studies.

Haemonchus contortus: prokaryotic expression and enzyme activity of recombinant HcSTK, a serine/threonine protein kinase

Members of the PAR-1/MARK serine/threonine protein kinase (STK) subfamily are important regulators of the cytoskeleton, and their characterization can provide insights into a number of critical processes relating to the development and survival of an organism. We previously investigated the mRNA expression for and organization of a gene (hcstk) representing HcSTK, an STK from the parasitic nematode Haemonchus contortus. In the present study, a recombinant form of HcSTK was expressed and characterized. Affinity-purified anti-HcSTK antibodies reacted with native HcSTK in protein homogenates extracted from third-stage larvae (L3) of H. contortus and were also used to immunolocalize the protein around the nuclei of ovarian and intestinal tissues of adult H. contortus. The enzyme activity of the recombinant HcSTK protein was also demonstrated. The findings show that recombinant HcSTK is a functional protein kinase, with activity directed to KXGS motifs, consistent with other members of the PAR-1/MARK STK subfamily.