Adjuvant effect of cholera toxin on systemic and mucosal immune responses in chickens infected with E-tenella or given recombinant parasitic antigen per os

We investigated the adjuvant effect of cholera toxin (CT) on the intestinal and systemic immune systems of chickens. The CT was given orally, mixed wi th a non-replicating antigen, a recombinant Eimeria protein, 1PE1, or with a replicating one, Eimeria tenella parasite. There were increases in the sp ecific IgA and IgG responses to the recombinant protein 1PE1, with a signif icant anti-1PE1 IgG response in the duodenum (p < 0.05) and caecum (p < 0.0 5) 4 weeks after immunization and a specific IgA (p < 0.05) response in the duodenum after 3 weeks. A transient anti-1PE1 IgG (p < 0.05) response was detected in the serum week post-injection and an IgA response (p < 0.05) at 2 weeks. CT given with the replicative parasite caused no change in the in testinal and systemic immune responses with 1 or 3 immunizations although a specific antiparasitic in vitro proliferation of the spleen cells from inf ected chickens was observed. Nevertheless, 0.05 mg CT given per os to chick ens was strongly immunogenic in both experiments. A strong serum IgG (p < 0 .01) response was detected as soon as 1 week after the end of the immunizat ion protocol with 1PE1 and 2 weeks after infection with E. tenella. Strong anti-CT Ige responses were also detected by the second week post-immunizati on in the duodenum and caeca (p < 0.01). Hence. CT can be used as a mucosal adjuvant in chickens to improve the intestinal immune response. (C) 1999 E lsevier Science Ltd. All rights reserved.