The protective capacity of UV-exposedClinostomum complanatummetacercariae against challenge infections inArdeola ibis ibis

Exposure of encysted metacercariaeof Clinostomum complanatumto UV light (254 nm) for 60 min reduced their development into adult worms in buff-backed herons (95.7% reduction in worm burden). Metacercariae that succeeded in developing into adult worms, showed low fecundity levels. Furthermore, 30% of eggs laid showed abnormal shape; however, all normal and abnormal eggs failed to hatch into miracidia. The effectiveness of UV-irradiated metacercariae as a vaccine was investigated. Compared to control unvaccinated herons, the vaccinated group showed a significantly high protection rate (73.8%) against challenge.In vitro, worm development after challenge showed decreased fecundity and increased egg abnormalities, where only 1.5% of all eggs produced hatched into miracidia. A passive haemagglutination test revealed increased antibody titres against soluble adult worm antigen in both vaccinated and vaccinated-challenged birds. It was concluded that vaccination of herons using encysted metacercariae UV-irradiated for 60 min can protect them against challenge infection.

Evaluation of anti-Schistosoma mansoni igG antibodies in patients with chronic schistosomiasis mansoni before and after specific treatment

The circumoval precipitin test (COPT), enzyme-linked immunosorbent assay (ELISA) and the immunoblotting anti-adult worm antigen (AWA) and soluble egg antigen (SEA) tests were applied to 17 chronically schistosome-infected patients for the detection of anti-Schistosoma mansoni antibodies before and on four occasions after oxamniquine administration over a period of six months. Compared to a control group, schistosomiasis patients showed high levels of IgG antibodies in AWA and SEA-ELISA. A decrease in IgG levels was observed six months after treatment, although negative reactions were not obtained. Significant decreases in IgG1, IgG3 and, mainly, IgG4, but not anti-SEA IgG2 levels were observed six months after treatment, again without negativity. Analysis of anti-AWA IgG antibodies by immunoblotting before treatment showed a 31 kDa strand in 14 patients (82%) which disappeared in three cases up to six months after treatment; furthermore, anti-SEA IgG antibodies showed the same band in nine patients (53%) before treatment, which disappeared in only four cases up to six months after treatment.

Role of Adult Worm Antigen-Specific Immunoglobulin E in Acquired Immunity to Schistosoma mansoni Infection in Baboons

ABSTRACT Allergic-type immune responses, particularly immunoglobulin E (IgE), correlate with protective immunity in human schistosomiasis. To better understand the mechanisms of parasite elimination we examined the immune correlates of protection in baboons (Papio cynocephalus anubis), which are natural hosts forSchistosoma mansoni and also develop allergic-type immunity with infection. In one experiment, animals were exposed to a single infection (1,000 cercariae) or were exposed multiple times (100 cercariae per week for 10 weeks) and subsequently were cured with praziquantel prior to challenge with 1,000 cercariae. Singly and multiply infected animals mounted 59 and 80% reductions in worm burden, respectively (P < 0.01). In a second experiment, animals were inoculated with S. mansoniova and recombinant human interleukin 12 (IL-12). This produced a 37 to 39% reduction in adult worm burden after challenge (P< 0.05). Parasite-specific IgG, IgE, IgM, and peripheral blood cytokine production were evaluated. The only immune correlate of protection in both experiments was levels of soluble adult worm antigen (SWAP)-specific IgE in serum at the time of challenge infection and/or 6 weeks later. Baboons repeatedly infected with cercariae or immunized with ova and IL-12 developed two- to sixfold-greater levels of SWAP-specific IgE in serum than did controls, and this correlated with reductions in worm burden (r 2, −0.40 to −0.64; P, <0.01). Thus, in baboons and unlike mice, adult worm-specific IgE is uniquely associated with acquired immunity to S. mansoni infection. This similar association of parasite-specific IgE and protection among primates infected with schistosomiasis, along with similar pathology, anatomy, and genetic make-up, indicates that baboons provide an excellent permissive experimental model for better understanding the mechanisms of innate and acquired immunity to schistosomiasis in humans.

Induction of protective immunity and modulation of granulomatous hypersensitivity in mice using PIII, an anionic fraction of Schistosoma mansoni adult worm

This study was performed in order to define Schistosoma mansoni antigens that are able to function as modulator agents in the granulomatous hypersensitivity to parasite eggs in BALB/c and C57BL/6 mice. A fraction of S. mansoni, designated PIII, derived from adult worm antigen preparation (SWAP) was obtained using anion-exchange chromatography on an FPLC system. Immunization of mice with PIII in the presence of Corynebacterium parvum and Al(OH)3 as adjuvant induced an immune response in these animals as determined by ELISA and spleen cell proliferation assays against S. mansoni antigens SEA, SWAP and PIII. In addition, PIII caused a significant degree of protection against a challenge infection in immunized mice as observed by the decrease on worm burden recovered from the portal system. We also showed that PIII profoundly inhibited the vigorous anamnestic granulomatous response to eggs in the liver and lungs. This suppression correlated with a significant decrease in granuloma size. From these results we conclude that the PIII preparation contains antigens that can mediate protective anti-parasite immunity and downregulate granulomatous hypersensitivity to S. mansoni eggs.