Immunization with newly transformed Schistosoma mansoni schistosomula tegument elicits tegument damage, reduction in egg and parasite burden

Evaluation of schistosomula lung antigen preparation and soluble egg antigen vaccines on experimental schistosomiasis mansoni

Schistosomiasis causes significant morbidity and mortality worldwide. This study aimed to assess the effect of schistosomula lung antigen preparation (SLAP) and soluble egg antigen (SEA) on a murine schistosomiasis mansoni model. Ninety laboratory-bred male Swiss albino mice were divided into 6 groups. Two doses of the vaccine were given at 2-week intervals. All mice were subcutaneously infected with 80±10 Schistosoma mansoni cercariae 2 weeks after the last vaccination dose. They were sacrificed 7 weeks post-infection. Parasitological and histopathological studies were conducted to assess the effect of inoculated antigens (single or combined). The results showed that the combination of SLAP and SEA (combination group) led to a significant reduction in worm burden (65.56%), and liver and intestine egg count (59% and 60.59%, respectively). The oogram pattern revealed a reduction in immature and mature eggs (15±0.4 and 10±0.8, respectively) and an increased number of dead eggs in the combination group (P<0.001). In terms of histopathological changes, the combination group showed notably small compact fibrocellular egg granuloma and moderate fibrosis in the liver. A high percentage of destroyed ova was observed in the intestine of the combination group. This study demonstrates for the first time the prophylactic effect of combined SLAP and SEA vaccine. The vaccine induced a significant reduction in the parasitological and pathological impacts of schistosomiasis mansoni in hepatic and intestinal tissues, making it a promising vaccine candidate for controlling schistosomiasis.

Effects of Immunization with Recombinant Schistosoma mansoni Enzymes AK and HGPRT: Murine Infection Control

Schistosomiasis is one of the most important human helminthiases worldwide. Praziquantel is the current treatment, and no vaccine is available until the present. Thus, the presented study aimed to evaluate the immunization effects with recombinant Schistosoma mansoni enzymes: Adenosine Kinase (AK) and Hypoxanthine-Guanine Phosphoribosyltransferase (HGPRT), as well as a MIX of the two enzymes. Female Balb/c mice were immunized in three doses, and 15 days after the last immunization, animals were infected with S. mansoni. Our results showed that the group MIX presented a reduction in the eggs in feces by 30.74% and 29%, respectively, in the adult worms. The groups AK, HGPRT and MIX could produce IgG1 antibodies, and the groups AK and MIX produced IgE antibodies anti-enzymes and anti-S. mansoni total proteins. The groups AK, HGPRT and MIX induced a reduction in the eosinophils in the peritoneal cavity. Besides, the group AK showed a decrease in the number of hepatic granulomas (41.81%) and the eggs present in the liver (42.30%). Therefore, it suggests that immunization with these enzymes can contribute to schistosomiasis control, as well as help to modulate experimental infection inducing a reduction of physiopathology in the disease.

SmTAL-9, a Member of the Schistosoma mansoni Tegument Allergen-Like Family, Is Important for Parasite Survival and a Putative Target for Drug/Vaccine Development

The tegument of Schistosoma mansoni is involved in essential functions for parasite survival and is known to stimulate immune responses in pre-clinical vaccine trials. Smtal-9, a member of the tegument-allergen-like (TAL) family, is one of the components of the tegument of schistosomula recognized by sera from immunized and protected mice. In this work, we assessed the role of Smtal-9 in parasite survival using the RNAi approach. Also, we cloned and expressed a recombinant form of Smtal-9 and evaluated its ability to induce protection in mice. Smtal-9 knockdown did not impact parasite survival in vitro, but significantly decreased schistosomula size. Additionally, significant reduction in both parasite and egg burdens were observed in mice inoculated with Smtal-9-knockdown schistosomula. Immunization using the Smtal-9 as an antigen conferred partial protection against challenge infection. Overall, our results indicate that Smtal-9 is a candidate target for drug and/or vaccine development due to its important role in parasite biology and survival.

Mechanism by which the combination of SjCL3 and SjGAPDH protects against Schistosoma japonicum infection

A vaccine is an important method to control schistosomiasis. Molecules related to lung-stage schistosomulum are considered potential vaccine candidates. We previously showed that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and cathepsin L3 (CL3) displayed differential expression in the lung-stage schistosomula of Schistosoma japonicum cocultured with host cells. In the present study, we prepared the two proteins and detected the protective effects of SjGAPDH by immunizing mice with this protein alone and in combination with SjCL3 with or without Freund's adjuvant. Then, we investigated the possible mechanisms underlying S. japonicum infection. The results showed that vaccination of adjuvanted SjGAPDH decreased the worm burden (37.8%) and egg load (38.1%), and the combination of adjuvanted SjGAPDH and SjCL3 further decreased the worm burden (65.6%) and egg load (70.9%) during Schistosoma japonicum infection. However, the immunization of a combination of adjuvant-free SjGAPDH and SjCL3 displayed a lower protective effect (< 15%) than those of the adjuvanted SjCL3, the adjuvanted SjGAPDH, and a combination of adjuvanted SjGAPDH and SjCL3. Flow cytometric results showed that the frequency of regulatory T cells (Tregs) was lower (P < 0.05) in the group with adjuvanted SjGAPDH and SjCL3 (2.61%) than the remaining groups. The enzyme-linked immunosorbent assay (ELISA) results indicated that except for the uninfected and infected control groups, the remaining groups displayed a Th1-type shift in immune responses. These results showed the immunization of SjGAPDH resulted in partial protection (approximately 38%); inoculation with a combination of SjCL3 and SjGAPDH in Freund's adjuvant resulted in a high immunoprotective effect (> 65%) against Schistosoma japonicum infection in mice, which was possibly caused by the reduced percentage of Tregs and a Th1-type shift in immune responses; and SjCL3 has no adjuvant-like effect, dissimilar to SmCL3.

Investigating Immunization With Nucleotide Enzymes of Schistosoma mansoni: Nucleoside Diphosphate Kinase and Adenylosuccinate Lyase as New Antigenic Targets Against Schistosomiasis

Schistosomiasis, caused by Schistosoma mansoni trematode worm, affects more than 1.5 million people in Brazil. The current treatment consists in the administration of Praziquantel, the only medicine used for treatment for more than 40 years. Some of the limitations of this drug consist in its inactivity against schistosomula and parasite eggs, the appearance of resistant strains and non-prevention against reinfection. Thus, the objective of this study was to evaluate the effect of immunization with recombinant functional enzymes of the purine salvage pathway of S. mansoni, Nucleoside Diphosphate Kinase (NDPK) and Adenylosuccinate Lyase (ADSL), to evaluate the host immune response, as well as the parasite load after vaccination. For this, Balb/c mice were divided into 5 groups: control (uninfected and untreated), non-immunized/infected, NDPK infected, ADSL infected, and NDPK + ADSL infected. Immunized groups received three enzyme dosages, with a 15-day interval between each dose, and after 15 days of the last application the animals were infected with 80 cercariae of S. mansoni. On the 47th day after the infection, fecal eggs were counted and, on the 48th day after the infection, the evaluation of leukocyte response, parasite load, antibody production, cytokines quantification, and histopathological analysis were performed. The results showed that immunizations with NDPK, ADSL or NDPK + ADSL promoted a discreet reduction in eosinophil counts in lavage of peritoneal cavity. All immunized animals showed increased production and secretion of IgG1, IgG2a, and IgE antibodies. Increased production of IL-4 was observed in the group immunized with the combination of both enzymes (NDPK + ADSL). In addition, in all immunized groups there were reductions in egg counts in the liver and intestine, such as reductions in liver granulomas. Thus, we suggest that immunizations with these enzymes could contribute to the reduction of schistosomiasis transmission, besides being important in immunopathogenesis control of the disease.

Immunogenicity, antibody responses and vaccine efficacy of recombinant annexin B30 against Schistosoma mansoni

AIMS

Schistosomes infect approximately 250 million people worldwide. To date, there is no effective vaccine available for the prevention of schistosome infection in endemic regions. There remains a need to develop means to confer long-term protection of individuals against reinfection. In this study, an annexin, namely annexin B30, which is highly expressed in the tegument of Schistosoma mansoni was selected to evaluate its immunogenicity and protective efficacy in a mouse model.

METHODS AND RESULTS

Bioinformatics analysis showed that there were three potential linear B-cell epitopes and four conformational B-cell epitopes predicted from annexin B30, respectively. Full-length annexin B30 was cloned and expressed in Escherichia coli BL21(DE3). In the presence of adjuvants, the soluble recombinant protein was evaluated for its protective efficacy in two independent vaccine trials. Immunization of CBA mice with recombinant annexin B30 formulated either in alum only or alum/CpG induced a mixed Th1/Th2 cytokine profile but no significant protection against schistosome infection was detected.

CONCLUSION

Recombinant annexin B30 did not confer significant protection against the parasite. The molecule may not be suitable for vaccine development. However, it could be an ideal biomarker recommended for immunodiagnostics development.

Immunization with adult Schistosoma mansoni tegument, treated with sub-curative praziquantel, partially protects mice against the infection

The tegument of schistosomes is a source of many potential anti-Schistosoma vaccine molecules. This work aimed to assess the protective effects of the adult Schistosoma mansoni tegument treated (TT) with sub-curative praziquantel (PZQ), whether in vivo (in vivo TT) or in vitro (in vitro TT), in murine schistosomiasis. In vitro TT and in vivo TT showed great similarity, and they differed from untreated tegument antigen (Teg) in terms of quantity and quality of protein bands on SDS-PAGE. Two immunization trials were performed, each with 50 mice, divided randomly into five groups of 10 mice each: (1) uninfected control mice (UC), (2) infected mice given phosphate buffer saline + adjuvant (PBS + adjuvant), (3) infected, Teg vaccinated, (4) infected, in vivo TT vaccinated, and (5) infected, in vitro TT vaccinated. All the immunizations with antigens induced mixed Th1/Th2 immune responses, as indicated by significantly high (P < 0.001) specific IgG2a and IgG1 levels, with Th1 predominating, as shown by a diminished IgG1/IgG2a ratio, as well as a high serum concentration of IFN-γ, an absence of IL-4 and increased IL-10. In vitro TT gave the most pronounced response. With respect to reduction of total worm burden, relative to PBS + adjuvant mice, in vitro TT achieved the highest significant (P < 0.001) results, followed by in vivo TT and Teg (51.8-57.04%, 44.6-50.2% and 35.2-39.3%, respectively). In scanning electron microscopy studies, all the tested antigens caused tegumental changes in adult worms, with the worst occurring with in vitro TT, such as retracted ventral sucker, an effect on the gynaecophoric canal, and changes to tubercles. In conclusion, in vitro TT, which is cheap to prepare, could be a potential vaccine against S. mansoni.

Schistosoma mansoni schistosomula antigens induce Th1/Pro-inflammatory cytokine responses

Larvae of Schistosoma (schistosomula) are highly susceptible to host immune responses and are attractive prophylactic vaccine targets, although cellular immune responses against schistosomula antigens in endemic human populations are not well characterized. We collected blood and stool from 54 Schistosoma mansoni-infected Ugandans, isolated peripheral blood mononuclear cells and stimulated them for 24 hours with schistosome adult worm and soluble egg antigens (AWA and SEA), along with schistosomula recombinant proteins rSmKK7, Lymphocyte Antigen 6 isoforms (rSmLy6A and rSmLy6B), tetraspanin isoforms (rSmTSP6 and rSmTSP7). Cytokines, chemokines and growth factors were measured in the culture supernatants using a multiplex luminex assay, and infection intensity was determined before and at 1 year after praziquantel (PZQ) treatment using the Kato-Katz method. Cellular responses were grouped and the relationship between groups of correlated cellular responses and infection intensity before and after PZQ treatment was investigated. AWA and SEA induced mainly Th2 responses. In contrast, rSmLy6B, rSmTSP6 and rSmTSP7 induced Th1/pro-inflammatory responses. While recombinant antigens rSmKK7 and rSmLy6A did not induce a Th1/pro-inflammatory response, they had an association with pre-treatment infection intensity after adjusting for age and sex. Testing more schistosomula antigens using this approach could provide immune-epidemiology identifiers necessary for prioritizing next generation schistosomiasis vaccine candidates.

DNA vaccination using recombinant Schistosoma mansoni fatty acid binding protein (smFABP) gene

Schistosomiasis is a fatal disease that has a negative impact on health and economics. Praziquantel (PZQ) is the drug of choice for schistosomiasis treatment, but it has no prophylactic effect; therefore, vaccination is an essential requirement in schistosomiasis control. This work was carried out to investigate the possible effect of DNA vaccination against Schistosoma mansoni infection using recombinant S. mansoni fatty acid binding protein (rsmFABP). The smFABP gene was cloned into the eukaryotic expression vector pcDNAI/Amp in order to obtain an smFABP-pcDNAI recombinant plasmid (DNA vaccine) and was used for the intramuscular DNA vaccination of out-bread Swiss albino mice prior to infection with S. mansoni cercariae. Infected groups, either DNA vaccinated or unvaccinated, were treated with PZQ at week 6 post-infection. After 8 weeks post-infection, all mouse groups were sacrificed and parasitological, immunological and histopathological parameters were studied. DNA vaccinated mice showed a high titer of anti-smFABP-IgG antibodies and acquired significant protection (74.2%, p < 0.01) against S. mansoni infection, with a reduction in ova and granuloma counts. DNA vaccinated and PZQ treated animals had higher titers of anti-smFABP-IgG antibodies and decreased (87%, P < 0.001) parenchymal granulomas compared to the DNA vaccinated PZQ untreated group. Infected mice, either non DNA vaccinated or vaccinated, had very high collagen content and fibrous granulomas (74%) compared to the PZQ treated group (10.3% fibrous granuloma) and PZQ treated + DNA vaccinated group (0% fibrous granuloma). In conclusion, DNA vaccination had protective and anti-pathological effects in naive mice and greatly improved the pathological status in PZQ-treated animals, suggesting an immunological and pathological modulating effect of PZQ treatment.

Molecular characterization of transport lectin vesicular integral membrane protein 36 kDa (VIP36) in the life cycle of Schistosoma mansoni

VIP36 is a protein described as an L-type lectin in animals, responsible for the intracellular transport of glycoproteins within the secretory pathway, and also localized on the plasma membrane. Schistosoma mansoni has a complex system of vesicles and protein transport machinery to the cell surface. The excreted/secreted products of the larvae and eggs are known to be exposed to the host immune system. Hence, characterizing the role and action of SmVIP36 in the S. mansoni life cycle is important for a better understanding of the parasite-host relationship. To this purpose, we firstly performed in silico analysis. Analysis of SmVIP36 in silico revealed that it contains a lectin leg-like domain with a jellyroll fold as seen by its putative 3D tertiary structure. Additionally, it was also observed that its CRD contains calcium ion-binding amino acids, suggesting that the binding of SmVIP36 to glycoproteins is calcium-dependent. Finally, we observed that the SmVIP36 predicted amino acid sequence relative to its orthologs was conserved. However, phylogenetic analysis revealed that SmVIP36 follows species evolution, forming a further cluster with its definitive host Homo sapiens. Moreover, q-PCR analysis in the S. mansoni life cycle points to a significant increase in gene expression in the eggs, schistosomulae, and female adult stages. Similarly, protein expression increased in eggs, cercariae, schistosomulae, and adult worm stages. These results suggest that SmVIP36 might participate in the complex secretory activity within the egg envelope and tegument proteins, both important for the stages of the parasite that interact with the host.

Antibodies are involved in the protective immunity induced in mice by Schistosoma mansoni schistosomula tegument (Smteg) immunization

The Schistosoma mansoni schistosomula tegument (Smteg) plays an important role in triggering the host immune response and mice immunization with Smteg formulated with Freunds adjuvant or alum + CpG induce partial protection against S. mansoni infection associated with an increased antibody production. In this study, we investigated the role of these antibodies in parasite killing both in vitro and in vivo. We demonstrated that these antibodies were able to bind to the surface of S. mansoni recently transformed schistosomula and that these antibodies significantly increase the percentage of schistosomula killed in vitro by complement activation. Passive transference of immune sera decreased the parasite burden and the number of eggs trapped in the organs of mice that received sera containing anti-Smteg antibodies. These results demonstrate that antibodies specific to surface tegumental antigens are involved in parasite elimination in mice immunized with Smteg.

Ultrastructural alterations in adult Schistosoma mansoni, harbored in non-antihelminthic treated and low-inflammatory mice by transmission electron microscopy (TEM)

This original study suggests that alterations observed on tegumental structure and egg quality of adult Schistosoma mansoni harvested from TS mice are due to their high immune tolerogenic and low-inflammatory capacity. The tegument of worms harvested from genetically selected mice for extreme phenotypes of immune oral tolerance, resistance (TR) and susceptibility (TS) were analyzed by transmission electron microscopy (TEM). Parasites recovered from TR mice showed no tegumental morphological changes. However, specimens collected from TS mice exhibited tubercle swelling with blunted and shortened spines in lower density. These tegumental alterations were similar to those described with artemether or praziquantel treatment, but without to affecting the worm surveillance, supporting observations that the host immune system influences the development and function of the tegument of worms harbored in non-antihelminthic treated TS mice. TS mice showed a higher percentage of dead eggs and a lower percentage of immature eggs than TR mice, but had similar quantities of collected eggs. This suggests that in TS mice the alterations in adult worm tegument prevented egg development, but not egg production or worm survival. These results corroborate our previous scanning electron microscopy (SEM) study indicating the influence of the host immune regulatory profile on the development and function of the worm's reproductive system and tegument.

Molecular characterization and identification of Th1 epitopes of a Schistosoma japonicum protein similar to prosaposin

The tegument of schistosomula contains T cell antigens that might simulate the protective mechanisms of the radiation-attenuated vaccine in a mouse model of schistosomiasis. Immune mechanisms mediated by the CD4+ Th1 response are important in the RAV model. To rapidly identify Th1 epitopes in molecules from the Schistosoma japonicum schistosomula tegument, this study analyzed S. japonicum proteomics data. Preliminary experiments identified a protein similar to prosaposin (SjPSAP) from the tegument of schistosomula. We confirmed that SjPSAP was present in the tegument of the parasite using an indirect immunofluorescence assay. We then identified Th cell epitopes in SjPSAP using in silico prediction combined with experimental validation. From the SjPSAP sequence, we used several algorithms to predict 11 promiscuous Th cell epitopes that might bind to both murine and human MHC class II molecules. To validate the in silico predictions, proliferation and cytokine production profiles of spleen lymphocytes from BALB/c mice immunized with the 11 predicted peptides were measured in vitro using a modified methyl thiazolyl tetrazolium assay and flow cytometry. The results showed that 4 of the 11 predicted peptides induced a recall CD4+ Th1 response in vitro. We measured direct binding of the four peptides predicted to induce a response to antigen-presenting cells from BALB/c mice using a fluorometric method and found that the peptides bound to both I-Ad and I-Ed mouse molecules. These results demonstrated that potentially protective Th1-type epitopes in SjPSAP molecules could be identified rapidly by combining in silico prediction with experimental validation. This strategy could be a fast method for identifying Th1 epitopes in a schistosoma antigen with features such as large size or poor expression of recombinant antigens.

Immunoprotection of mice against Schistosomiasis mansoni using solubilized membrane antigens

BACKGROUND

Schistosomiasis continues to be one of the most prevalent parasitic diseases in the world. Despite the existence of a highly effective antischistosome drug, the disease is spreading into new areas, and national control programs do not arrive to complete their tasks particularly in low endemic areas. The availability of a vaccine could represent an additional component to chemotherapy. Experimental vaccination studies are however necessary to identify parasite molecules that would serve as vaccine candidates. In the present work, C57BL/6 female mice were subcutaneously immunized with an n-butanol extract of the adult worm particulate membranous fraction (AWBE) and its protective effect against a S. mansoni challenge infection was evaluated.

METHODOLOGY AND FINDINGS

Water-saturated n-butanol release into the aqueous phase a set of membrane-associated (glyco)proteins that are variably recognized by antibodies in schistosome-infected patients; among the previously identified AWBE antigens there is Alkaline Phosphatase (SmAP) which has been associated with resistance to the infection in mice. As compared to control, a significantly lower number of perfuse parasites was obtained in the immunized/challenged mouse group (P<0.05, t test); and consequently, a lower number of eggs and granulomas (with reduced sizes), overall decreasing pathology. Immunized mice produced high levels of sera anti-AWBE IgG recognizing antigens of ∼190-, 130-, 98-, 47-, 28-23, 14-, and 9-kDa. The ∼130-kDa band (the AP dimer) exhibited in situ SmAP activity after addition of AP substrate and the activity was not apparently inhibited by host antibodies. A preliminary proteomic analysis of the 25-, 27-, and 28-kDa bands in the immunodominant 28-23 kDa region suggested that they are composed of actin.

CONCLUSIONS

Immunization with AWBE induced the production of specific antibodies to various adult worm membrane molecules (including AP) and a partial (43%) protection against a challenging S. mansoni infection by mechanism(s) that still has to be elucidated.

Immunization with tegument nucleotidases associated with a subcurative praziquantel treatment reduces worm burden following Schistosoma mansoni challenge

Schistosomiasis is a debilitating disease caused by flatworm parasites of the Schistosoma genus and remains a high public health impact disease around the world, although effective treatment with Praziquantel (PZQ) has been available since the 1970s. Control of this disease would be greatly improved by the development of a vaccine, which could be combined with chemotherapy. The sequencing of the Schistosoma mansoni transcriptome and genome identified a range of potential vaccine antigens. Among these, three nucleotidases from the tegument of the parasite, presumably involved in purinergic signaling and nucleotide metabolism, were proposed as promising vaccine candidates: an alkaline phosphatase (SmAP), a phosphodiesterase (SmNPP-5) and a diphosphohydrolase (SmNTPDase). Herein, we evaluate the potential of these enzymes as vaccine antigens, with or without subcurative PZQ treatment. Immunization of mice with the recombinant proteins alone or in combination demonstrated that SmAP is the most immunogenic of the three. It induced the highest antibody levels, particularly IgG1, associated with an inflammatory cellular immune response characterized by high TNF-α and a Th17 response, with high IL-17 expression levels. Despite the specific immune response induced, immunization with the isolated or combined proteins did not reduce the worm burden of challenged mice. Nonetheless, immunization with SmAP alone or with the three proteins combined, together with subcurative PZQ chemotherapy was able to reduce the worm burden by around 40%. The immunogenicity and relative exposure of SmAP to the host immune system are discussed, as key factors involved in the apparently synergistic effect of SmAP immunization and subcurative PZQ treatment.

Schistosoma mansoni schistosomula tegument (Smteg) immunization in absence of adjuvant induce IL-10 production by CD4+ cells and failed to protect mice against challenge infection

The Schistosoma mansoni tegument interaction with the immune system plays a key role in disease establishment or elimination. We have recently demonstrated that S. mansoni schistosomula tegument (Smteg) is able to activate innate immune response and to induce protective immunity in a vaccine formulation with Freunds adjuvant. In this work, we evaluated the ability of Smteg to elicit protection in the absence of adjuvant. Smteg mice immunization resulted in significant antibody production, increased percentage of CD4+IFN-g+ and CD4+IL-10+ cells in spleen and increased production of IFN-g and IL-10 by spleen cells, but failed to reduce parasite burden, female fecundity and morbidity. We also demonstrated that BMDC stimulation with Smteg resulted in significant IL-10 production. Our results demonstrate that Smteg has immune modulatory proprieties.

Evaluation of the protective immune response induced in mice by immunization with Schistosoma mansoni schistosomula tegument (Smteg) in association with CpG-ODN

In schistosomiasis, the current control strategy does not prevent reinfection, therefore, vaccine strategies are essential to combat the Schistosoma mansoni. The efficacy vaccine depends on parasite stage and effective adjuvant. We have recently demonstrated that S. mansoni schistosomula tegument (Smteg) is able to activate dendritic cells up regulate CD40 and CD86 molecules and induce a partial protection in mice (43-48%) when formulated with Freund's adjuvant. In this study we evaluated the ability of Smteg + alum or Smteg + alum + CpG-ODN to induce protection in mice. Our results demonstrate that Smteg + alum + CpG-ODN induced a partial reduction in worm burden (43.1%), reduction in the number of eggs eliminated in the feces. The protective response was associated with a predominant Th1 type of immune response, with increased production of specific IgG2c, IFN-γ and TNF-α, B cells proliferation and CD4 cells and macrophages activation.

Schistosoma tegument proteins in vaccine and diagnosis development: an update

The development of a vaccine against schistosomiasis and also the availability of a more sensitive diagnosis test are important tools to help chemotherapy in controlling disease transmission. Bioinformatics tools, together with the access to parasite genome, published recently, should help generate new knowledge on parasite biology and search for new vaccines or therapeutic targets and antigens to be used in the disease diagnosis. Parasite surface proteins, especially those expressed in schistosomula tegument, represent interesting targets to be used in vaccine formulations and in the diagnosis of early infections, since the tegument represents the interface between host and parasite and its molecules are responsible for essential functions to parasite survival. In this paper we will present the advances in the development of vaccines and diagnosis tests achieved with the use of the information from schistosome genome focused on parasite tegument as a source for antigens.

Vaccination with enzymatically cleaved GPI-anchored proteins from Schistosoma mansoni induces protection against challenge infection

The flatworm Schistosoma mansoni is a blood fluke parasite that causes schistosomiasis, a debilitating disease that occurs throughout the developing world. Current schistosomiasis control strategies are mainly based on chemotherapy, but many researchers believe that the best long-term strategy to control schistosomiasis is through immunization with an antischistosomiasis vaccine combined with drug treatment. In the search for potential vaccine candidates, numerous tegument antigens have been assessed. As the major interface between parasite and mammalian host, the tegument plays crucial roles in the establishment and further course of schistosomiasis. Herein, we evaluated the potential of a GPI fraction, containing representative molecules located on the outer surface of adult worms, as vaccine candidate. Immunization of mice with GPI-anchored proteins induced a mixed Th1/Th2 type of immune response with production of IFN-γ and TNF-α, and low levels of IL-5 into the supernatant of splenocyte cultures. The protection engendered by this vaccination protocol was confirmed by 42% reduction in worm burden, 45% reduction in eggs per gram of hepatic tissue, 29% reduction in the number of granulomas per area, and 53% reduction in the granuloma fibrosis. Taken together, the data herein support the potential of surface-exposed GPI-anchored antigens from the S. mansoni tegument as vaccine candidate.

Computational vaccinology: an important strategy to discover new potential S. mansoni vaccine candidates

The flatworm Schistosoma mansoni is a blood fluke parasite that causes schistosomiasis, a debilitating disease that occurs throughout the developing world. Current schistosomiasis control strategies are mainly based on chemotherapy, but many researchers believe that the best long-term strategy to control schistosomiasis is through immunization with an antischistosomiasis vaccine combined with drug treatment. Several papers on Schistosoma mansoni vaccine and drug development have been published in the past few years, representing an important field of study. The advent of technologies that allow large-scale studies of genes and proteins had a remarkable impact on the screening of new and potential vaccine candidates in schistosomiasis. In this postgenomic scenario, bioinformatic technologies have emerged as important tools to mine transcriptomic, genomic, and proteomic databases. These new perspectives are leading to a new round of rational vaccine development. Herein, we discuss different strategies to identify potential S. mansoni vaccine candidates using computational vaccinology.

Identification, structure and function of a novel tetraspaninhomologue from Spirometra erinaceieuropaei

OBJECTIVE

To identify a full length c DNA sequence of a novel tetraspanin (TSP) homologue from Spirometra erinaceieuropaei and to predict the structure and function of its encoding protein using bioinformatics methods.

METHODS

Using the NCBI, EMBI, Expasy and other online sites, the open reading frame (ORF), conserved domain, physical and chemical parameters, signal peptide, transmembrane domain, epitope, topological structures of the protein sequences were predicted. And Vector NTI software was used for multiple sequence alignment and phylogenetic tree construction.

RESULTS

The target sequence was 1132 bp length with a 681 bpbiggest ORF encoding 226 amino acids protein with typical TSP conserved domain. It was confirmed as full length c DNA of TSP16 from Spirometra erinaceieuropaei and named as SeTSP16 (GenBank accession number: JF728872). The predicted molecular weight and isoelectric point of the deduced protein were 24 750.5 Da and 7.88 Da, respectively. Compared with TSP16s from Schistosoma japonicum and Schistosoma mansoni, it showed similarity of 59% and 59%, respectively. SeTSP16 contained four transmembrane domains (TM1-4), intracellular N and C-termini, one short small extracellular loop and one large extracellular loop. Four major epitopes that were significant different from the corresponding epitope regions of TSP16 from Schistosoma mansoni and Schistosoma japonicum were predicted.

CONCLUSIONS

The full length c DNA sequences of SeTSP16 are identified. It encodes a transmembrane protein which might be an ideal diagnosis antigen and target molecule for antiparasitic drugs.

Identification of novel antigens within the Schistosoma japonicum tetraspanin family based on molecular characterization

Tetraspanins (TSPs) are proteins found on the surface of the parasite Schistosoma mansoni that have been regarded as potential protective antigens. However, divergent evolution may occur among the species of S. mansoni and Schistosoma japonicum under different environmental pressure. Thus, it was essential to characterize the S. japonicum TSP family members before selecting potential candidate TSP antigens. In this study, we used bioinformatics and experimental validation to investigate 29 TSP members from S. japonicum, including all known genes, Sj23, TE736, Sj25, and Sj-TSP-2. Five TSP members were found to be variable, and two others (Sj-tsp genes) were alternatively spliced. The phylogenetic analysis showed that schistosome TSPs were highly divergent from those of other phyla. Quantitative RT-PCR revealed that the Sj-tsp genes were differentially transcribed in the developmental stages of cercariae, schistosomula, adult worms, and eggs. Six Sj-tsp genes were significantly up-regulated during the transformation from cercariae to schistosomula. Four Sj-tsp genes, including Sj-tsp-1, Sj-tsp-8, Sj-tsp-14, and Sj-tsp-26 were confirmed as potential protective antigens based on the molecular characterization. RNAi was preformed against the conserved Sj-tsp genes which were highly expressed in schistosomula to explore gene functions. These data will promote the identification of candidate antigens within the TSP family for developing novel vaccines against S. japonicum infections.