Potential of a recombinant Schistosoma bovis-derived glutathione S-transferase to protect cattle against experimental and natural S. mattheei infection
J. DE BONT a1 , J. VERCRUYSSE a1 , J. M. GRZYCH a2 , P. F. M. MEEUS a3 and A. CAPRON a2
a1 Department of Parasitology, Faculty of Veterinary Medicine, University of Gent, Salisburylaan 133, B-9820 Merelbeke, Belgium
a2 Centre d'Immunologie et de Biologie Parasitaire, Unité Mixte INSERM-U167, IFR No. 17 Institut Pasteur de Lille, 1 rue du Pr Calmette, 59019 Lille, France
a3 Department of Clinical Studies, Samora Machel School of Veterinary Medicine, University of Zambia, Box 32379, Lusaka, Zambia
The potential of a recombinant Schistosoma bovis-derived glutathione S-transferase (rSb28GST) to protect cattle against S. mattheei infection was tested in Zambia. All animals were challenged 2 weeks after the second inoculation with either 0·250 mg rSb28GST in adjuvants (vaccinated calves, n=14) or adjuvants alone (controls, n=14). In a first experiment, 7 vaccinated and 7 control animals were exposed to 10000 S. mattheei cercariae percutaneously. All animals developed clinical schistosomiasis 7–8 weeks after challenge. At perfusion, 12 weeks after challenge, vaccinated and control groups had averages of 887 and 541 eggs per gramme (epg) faeces, 6515 and 5990 worms, and 4·2 and 3·4 million tissue eggs, respectively. These results indicate that the immunization protocol used did not protect these calves against the massive single experimental challenge. In a second experiment, another 2 groups (n=7) of vaccinated and control animals were challenged naturally over a period of 9 months on a farm known to be endemic for S. mattheei. The natural infections were much lighter in intensity, as indicated by the mean faecal egg count (13 epg), worm count (139) and tissue egg count (294000) in non-vaccinated controls. In vaccinated calves, significant reductions in female worm burdens (50%), faecal egg counts (89%) and miracidial counts (93%) were recorded. Total tissue egg counts were also reduced by 42% in vaccinated animals. It therefore appears that the rSb28GST can provide significant protection in cattle against S. mattheei under conditions of low to moderate natural infection.(Received November 18 1996)
(Revised February 26 1997)
(Accepted February 26 1997)
Key Words: Schistosoma mattheei; vaccination; glutathione S-transferase; cattle.
Corresponding author: Department of Parasitology, Faculty of Veterinary Medicine, University of Gent, Salisburylaan 133, B-9820 Merelbeke, Belgium. Tel: +32 9 264 74 03. Fax: +32 9 264 74 96. E-mail: Jean.DeBont@rug.ac.be.