Vaccination of sheep against Schistosoma japonicum with either glutathione S-transferase, keyhole limpet haemocyanin or the freeze/thaw schistosomula/BCG vaccine

The protective potential of glutathione S-transferase (GST), keyhole limpet haemocyanin (KLH) and the freeze/thaw (F/T) schistosomula/BCG vaccine was evaluated against Schistosoma japonicum in the natural sheep host. Groups of ten sheep each were vaccinated as follows: • Group I: 2 × F/T 30 000 schistosomula + BCG 3 × 10 8 organisms, with a 2 week interval between vaccinations (F/T ‘Low’). • Group II: 3 × F/T 20 000 schistosomula + BCG 3 × 10 8, with 4 week interval (F/T ‘High’). • Group III: 2 × GST 0.24 mg + FCA (Freund's complete adjuvant) with 2 week interval (GST ‘Low’). • Group IV: 3 × GST 0.24 mg + FCA, with 4 week interval (GST ‘SHigh’). • Group V: 2 × KLH 1.0 mg in phosphate-buffered saline (PBS), with 2 week interval (KLH ‘Low’). • Group VI: 3 × KLH 1.0 mg in PBS, with 4 week interval (KLH ‘High’). • Group VII: control (not vaccinated). Specific antibody, detected by GST-enzyme-linked immunosorbent assay (ELISA) and KLH-ELISA on the day after the last vaccination and 1, 2 and 3 weeks post-challenge, was found in all GST- or KLH-vaccinated groups. The same was found in F/T schistosomula-vaccinated groups against crude adult worm antigen (AWA). In Western blotting all GST-vaccinated sera recognized 26 kDa and 28 kDa bands on the challenge day and at 3 and 11 weeks post-challenge. Mean faecal egg counts between Weeks 6 and 10 post-challenge were reduced in a statistically significant way at five time points in the four groups, i.e. 83.38% ( P