Orally administered Giardia duodenalis extracts enhance an antigen-specific antibody response

We have identified novel adjuvant activity in specific cytosol fractions fr om trophozoites of Giardia isolate BRIS/95/HEPU/2041 (J. A. Upcroft, P. A. McDonnell, and P. Upcroft, Parasitol. Today, 14:281-284, 1998). Adjuvant ac tivity was demonstrated in the systemic and mucosal compartments when Giard ia extract was coadministered orally with antigen to mice. Enhanced antigen -specific serum antibody responses were demonstrated by enzyme-linked immun osorbent. assay to be comparable to those generated by the "gold standard," mucosal adjuvant cholera toxin. A source of adjuvant activity was localize d to the cytosolic component of the parasite. Fractionation of the cytosol produced fraction pools, some of which, when coadministered with antigen, s timulated an enhanced antigen-specific serum response. The toxic component of conventional mucosal adjuvants is associated with adjuvant activity; the refore, in a similar way, the toxin-like attributes of BRIS/95/HEPU/2041 ma y be responsible for its adjuvanticity. Complete characterization of the ad juvant is under way.