IMMUNE-RESPONSE IN MICE FOLLOWING IMMUNIZATION WITH DNA ENCODING FRAGMENT-C OF TETANUS TOXIN

Tetanus toxin is a potent neurotoxin synthesized by Clostridium tetani . Immunization with fragment C protein, the nontoxic C-terminal domain of tetanus toxin, will protect mice against lethal challenge with tet anus toxin. A synthetic gene encoding fragment C (tetC) had previously been shown to express high levels of fragment C in Saccharomyces cere visiae. A plasmid, pcDNA3/tetC, which encodes the synthetic tetC gene expressed under the control of the human cytomegalovirus major interme diate-early promoter/enhancer region, was constructed. Expression of f ragment C was observed in eukaryotic cells growing in vitro following transfection with pcDNA3/tetC. The immune response induced by intramus cular immunization with pure pcDNA3/tetC DNA was evaluated in a murine model. Anti-fragment C serum immunoglobulin and proliferative respons es in splenocytes were observed in BALB/c mice following two immunizat ions with pcDNA3/tetC. The major immunoglobulin G subclass that recogn ized fragment C was immunoglobulin G2a, and the stimulated splenocytes secreted high levels of gamma interferon. Immunity to tetanus is depe ndent on the presence of neutralizing serum antibodies against tetanus toxin. Sufficient anti-fragment C serum immunoglobulins were induced by DNA-mediated immunization to protect mice against lethal challenge with tetanus toxin.