Immunologic protection of anti-tetrodotoxin vaccines against lethal activities of oral tetrodotoxin challenge in mice

Tetrodotoxin (TTX) is a high toxic small molecular neurotoxin. Haptenic vaccine for TTX was investigated and the carrier proteins were compared. TTX was conjugated to Tachypleus tridentatus hemocyanin (TTH) and tetanus toxoid (TT) via formaldehyde to form the artificial antigen TTX-TTH and TTX-TT. BALB/c mice were immunized with the artificial antigen, the TTX-specific antibody response were detected. The immunized animals were intragastrically challenged with increasing doses of TTX repeatedly. The mice which exposed to TTX in doses of 600, 630, 800, 1200, 1500, 2000 and 2400 μg/kg survived at rates of 100, 100, 90, 90, 80, 50 and 20%, with a LD50 value of 2020 μg/kg for TTH-TTX vaccine, and of 100%, 90.9%, 90.9%, 90.9%, 63.6%, 27.3% and 0%, with a LD50 value of 1410 μg/kg for TT-TTX vaccine, respectively. All control mice inoculated with carrier protein TTH or TT uniformly died of a dose of 600 μg/kg TTX i.g. challenge. Animals immunized with vaccines could antagonize repeated TTX challenge, half of them surviving about 6 mg/kg, and a few being able to bear a maximal accumulative dose as high as approximate 9 mg/kg of TTX challenges within eight months. The TTH-TTX vaccine was of the more excellent in protective effect from TTX oral intoxication, mainly resulted from the higher antibody affinity than that from TT-TTX vaccine. The present study for the first time demonstrated that the anti-TTX experimental vaccines would high effectively protect animal from multiple, oral TTX intoxication. Immunoprophylaxis would be the hopeful means against TTX poisoning.