Influence of carrier proteins on the immunologic response to haptenic antitetrodotoxin vaccine

Tetrodotoxin ( TTX) is a haptenic, highly toxic neurotoxin with no specific antidote available yet. Anti- TTX vaccine is being studied for antitoxin development. The effectiveness of the carrier protein in eliciting TTXspecific antibody response was comparatively studied. TTX was conjugated to Tachypleus tridentatus hemocyanin ( TTH), Limulus polyphemus hemocyanin ( LPH), tetanus toxoid ( TT), diphtheria toxoid ( DT), and bovine serum albumin ( BSA) chemically to form artificial antigens TTH- TTX, LPH- TTX, TT- TTX, DT- TTX, and BSATTX, respectively, with which BALB/ c mice were immunized, and the antibody response and antitoxic efficacy were detected. The serum anti- TTX antibody response and antitoxic efficacy varied markedly with adopted carrier protein. TTH- TTX elicited the best and BSA- TTX the worst TTX- specific antibody response. The proportion of the immunized mice surviving a 3 x lethal dose ( LD) dose of TTX challenge was 92%, 75%, 42%, 8%, and 0% for TTH-, TT-, LPH-, DT-, and BSA- TTX conjugates, respectively. The rank order of total efficacy of carrier protein for both anti- TTX antibody response and antitoxic effect was TTH > TT > LPH > DT > BSA. As a result of formaldehyde treatment in coupling of TTX carriers, the relative immunogenicity of TTX Vs carrier, that is, the ratio of TTX- to carrier- specific antibody response, evidently varied with respective carrier adopted, in a rank order of TT > BSA > TTH > DT > LPH. The results suggest that the carrier protein used in haptenic TTX vaccine is greatly important in eliciting potent anti- TTX antibody, and both TTH and TT are the preferred carriers for development of excellent experimental TTX vaccine.