The role of adult worms in suppressing functional protective immunity to Heligmosomoides polygyrus bakeri challenge infections.

Adult Heligmosomoides polygyrus bakeri, radiolabelled with [35S]-methionine were successfully transferred to naive NIH mice by oral gavage. Adult worms and radiolabel could be detected up to 45 days post-infection. Adult worms gavaged into immune NIH mice, immunized with a drug abbreviated larval infection, were rejected within 45 days. These adults worms were unable to ablate the development of a functional protective response to a larval challenge infection in the NIH strain. In fact 50 adult worms were sufficient to significantly immunize NIH mice against a larval challenge infection. However, adult worms were able to suppress the development of a functional protective response in an outbred CFLP strain. Although a protective immune response could not be elicited to a challenge infection in CBA mice, the presence of gavaged adult worms was shown to increase the susceptibility of mice to a challenge infection. For all mouse strains, no significant difference in levels of L4 antigen-specific serum IgG, IgG1, IgG2a, and IgA existed between immune mice and groups of mice immunosuppressed by adult worms. Levels of L4 antigen-specific serum IgG1 were significantly lower in the poorly immunizable CBA strain compared to CFLP and NIH strains. No correlation was found across mouse strains between the intensity of the antibody response and the mean worm burdens per animal group. In addition, no correlation was found between levels of L4 antigen-specific antibody within each mouse and the loss of worms by individual mice.