A MUTANT PERTUSSIS TOXIN MOLECULE THAT LACKS ADP-RIBOSYLTRANSFERASE ACTIVITY, PT-9K 129G, IS AN EFFECTIVE MUCOSAL ADJUVANT FOR INTRANASALLYDELIVERED PROTEINS/

We examined the capacity of a genetically detoxified derivative of per tussis toxin (PTX), PT-9K/129G, to act as a mucosal adjuvant for an in tranasally (i.n.) administered tetanus vaccine. Groups of mice were im munized i.n. with the nontoxic C-terminal 50-kDa portion of tetanus to xin (fragment C [Frg C]) either alone or mixed with PT-9K/129G, PTX, o r cholera toxin (CT) or were immunized subcutaneously (s.c.) with an e quivalent amount of Frg C adsorbed to alhydrogel. In response to a sin gle immunization, mice receiving Frg C plus PT-9K/129G or CT i.n. and parenterally immunized mice developed high-titer (> 20,000) anti-Frg C antibodies, whereas mice immunized i.n. with Frg C plus PTX or with F rg C alone seroconverted only after being boosted. The serum anti-Frg C response was dominated by immunoglobulin G1 (IgG1) in mice immunized with Frg C plus PT-9K/129G, with Frg C plus PTS, or s.c. In contrast, IgG1, IgG2a, and IgG2b contributed almost equally to the Frg C respon se when CT was the adjuvant. Anti-Frg C IgE was detected only in the s era of mice immunized i.n. with Frg C plus PTX and immunized s.c. with Frg C plus alhydrogel. High levels ofIgA antibodies were present in n asal lavage fluid from mice immunized i.n. with Frg C plus PT-9K/129G, PTX, or CT but not in that from mice given Frg C atone i.n. or parent erally. The mucosal adjuvanticity of PT-9K/129G was manifested in inbr ed as well as outbred mice. A single i.n. dose of Frg C plus either PT -9K/129G or PTX (with high specific activity) was sufficient to protec t all immunized mice from tetanus toxin challenge, in contrast to the case for mice that received Frg C alone i.n. We conclude that the pert ussis toxin analog PT-9K/129G, which is devoid of ADP-ribosyltransfera se activity, is a potent mucosal adjuvant for vaccines delivered via t he respiratory tract.