Cross-Reactivity ofSchistosoma mansoniCytosolic Superoxide Dismutase, a Protective Vaccine Candidate, with Host Superoxide Dismutase and Identification of Parasite-Specific B Epitopes

Abstract

Schistosoma mansoni, an intravascular parasite, has evolved a number of immune evasion mechanisms to establish itself in the host, such as antioxidant enzymes. Our laboratory has demonstrated that the highest levels of certain antioxidant enzymes are found in adult worms, which are the least susceptible to immune killing. Vaccination of mice with naked DNA constructs containing the gene encoding Cu/Zn cytosolic superoxide dismutase (SmCT-SOD) showed significant levels of protection compared to a control group, and our data demonstrate that the adult worms are a target of the immune response that confers resistance in SmCT-SOD DNA-vaccinated mice. Because SmCT-SOD shows significant identity with the human homologue, we evaluated the reactivity of anti-SmCT-SOD antibodies derived from SmCT-SOD-immunized mice and rabbits and from S. mansoni-infected individuals to human superoxide dismutase (hSOD) and SmCT-SOD parasite-specific peptides to assess the potential for autoimmune responses from immunization with the recombinant molecule. In addition, we evaluated the ability of various SmCT-SOD adjuvant-delivered immunizations to induce cross-reactive antibodies. Both mouse and rabbit antibodies generated against SmCT-SOD recognized the denatured form of hSOD. The same antibodies did not recognize nondenatured hSOD. Sera from infected individuals with different clinical forms of schistosomiasis recognized SmCT-SOD but not hSOD. Antibodies from mice immunized with different SmCT-SOD-containing formulations of both DNA and protein were able to recognize SmCT-SOD-derived peptides but not soluble hSOD. All together, these findings serve as a basis for developing a subunit vaccine against schistosomiasis.Schistosomiasis remains an endemic problem in over 76 countries, although approaches to reduce transmission and morbidity as well as to improve sanitation, mollusciciding and mass chemotherapy, have been attempted (3, 13). Vaccine development to control schistosomiasis is a high priority, as it would offer the potential of cost-efficient, long-lasting prophylaxis (2, 65). Schistosoma mansoni, an intravascular parasite, lives in a hostile environment in close contact with host humoral and cellular cytotoxic factors. Larval parasite killing mechanisms include the release of oxidants by eosinophils, neutrophils, and macrophages potentiated by antibodies and/or cytokines (8,12,16,31,32). However, to establish itself in the host, the parasite has evolved a number of immune evasion mechanisms (17,39,51,60), such as antioxidant enzymes (7,11,30,37). These are essential enzymes involved in the prevention of reactive oxygen species-derived damage. Evidence for the involvement of schistosome antioxidant enzymes, such as cytosolic superoxide dismutase (SmCT-SOD) and glutathione peroxidase (SmGPX), in immune evasion has been presented elsewhere (39). SmCT-SOD and GPX localize to the host-parasite interface (worm tegument and gut epithelium of the adult but not the larval schistosome) (41) and show developmental regulation (29,41,42) wit...

Nucleic Acid Vaccination withSchistosoma mansoniAntioxidant Enzyme Cytosolic Superoxide Dismutase and the Structural Protein Filamin Confers Protection against the Adult Worm Stage

“…The consistent increase in SmCT-SOD-specific IgG2b in both control and pcCT-SOD-vaccinated mice indicates that the antigen stimulates a more T1-type antibody response. This is consistent with our previous results showing a T1 predominance when SmCT-SOD is used in various vaccine formulations (15). In contrast, for pc-filamin-vaccinated mice, a significantly increased frequency of CD4 ϩ cells positive for T2 cytokines after WE stimulation (data not shown) correlates with the increased levels of filamin-specific antibodies in pcfilamin that indicates a more Th0-or mixed Th1-/Th2-type response.…”

“…Serum samples collected as described above were serially diluted and used to determine total IgG and Ig isotype responses by ELISA (8,15). Goat anti-mouse IgG-or goat anti-rabbit IgG-alkaline phosphatase conjugate (Sigma) was then added to each well, and the pNPP phosphatase substrate system (Kirkegaard & Perry Laboratories, Gaithersburg, Md.)…”

“…The entire open reading frame of SmGPX and the 1.7-kb fragment of S. mansoni filamin were cloned into the pGEX-4T-1 and pGEX-3X vectors (Amersham Biosciences, Piscataway, N.J.), respectively. Recombinant protein was expressed in Escherichia coli by using the above-described expression systems and purified by column elution (15). Recombinant His-SmCT-SOD, maltose binding protein (MBP)-SmCT-SOD, glutathione S-transferase (GST)-SmCT-SOD, GST-SmGPXm (a mutated form of SmGPX in which the selenocysteine [TGA] has been changed to cysteine [TCT] [36]), thrombin-cleaved SmGPXm, and GST-filamin were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting prior to use in enzyme-linked immunosorbent assay (ELISA).…”

Immunostimulatory property of a synthetic peptide belonging to the soluble ATP diphosphohydro-lase isoform (SmATPDase 2) and immunolocalisation of this protein in the Schistosoma mansoni egg

“…IgG2a, a Th1 cytokine-derived isotype, has been described as being protec tive against schistosomula and adult worms, possibly through antibody-dependent cell cytotoxic mechanisms, whereas IgG1, a Th2 cytokinederived isotype, has been associated with the immunomodulation of the granulomatous inflammation in schistosomiasis (Mountford et al 1994, Coelho et al 1996, James et al 1998, Zouain et al 2000, Carvalho-Queiroz et al 2004, Kusel et al 2007. The epitopes within soluble ATP diphosphohydrolase from the S. mansoni egg described here, as well as within SmATPDase 2 from the cercariae, schistosomula and adult worm (Levano-Garcia et al 2007), could be related to the success of the parasitism through disease immunomodulation during the course of the parasitic infection.…”

Functional expression and characterization of a cytosolic copper/zinc-superoxide dismutase of Spirometra erinacei

“…SODs have been identified and characterized in various helminth parasites, and their essential roles for parasite survival in the hosts have been well addressed (Henkle et al 1991;Hong et al 1992;HenkleDührsen et al 1995;Kim et al 2000;Tawe et al 2000;Castellanos-González et al 2002;Lee et al 2005;Li et al 2005a, b;Wu et al 2008). Several studies have also suggested the potential of SODs of parasitic helminths as vaccine candidates (Shalaby et al 2003;Carvalho-Queiroz et al 2004;Cook et al 2004;Vaca-Paniagua et al 2008). However, most of these studies have focused on the SODs of trematode and nematode parasites, and only limited information is currently available about the SODs of cestode parasites.…”