The effect of immunization of pigs with Ascaris suum cuticle components on the development of resistance to parenteral migration during a challenge infection.

The development of immunity to Ascaris suum was studied in pigs immunized with isolated cuticle fragments from A. suum second and third stage larvae (L2/L3) and adult worms, and compared with other methods that stimulate a strong protective response in pigs. A significant protective response was seen in animals immunized with isolated cuticle fragments from A. suum L2/L3 and adults, but it was less than that seen in animals inoculated with UV-irradiated eggs or naturally exposed to eggs on a dirt lot. Significant IgG responses to 2-mercaptoethanol (2ME)-soluble cuticle components were seen in all groups, but the level of the antibody response did not relate to protection. Group differences in antibody and lymphocyte blastogenic responses to cuticle proteins indicated quantitative and qualitative stage specific differences in 2ME-soluble and insoluble cuticular proteins. Intestinal immunity was notably absent from cuticle immunized pigs because a marked liver white spot response was observed following the challenge inoculation. Thus, cuticle fragments from larval and adult A. suum are capable of inducing a protective response to larval migration; however, the development of intestinal immunity is not a direct function of exposure to these antigens.