Abstract: In order to explore the mode and possible sites of action of Lactobacillus rhamnosus in reducing the immunologic activity of tetrodotoxin (TTX), activated cells, heat-inactivated cells, broken cell debris, extracellular polysaccharide-deficient cells, protoplasts, cell walls and cell wall peptidoglycans of L. rhamnosus were separately incubated together with TTX standard at 37 ℃ for 1 h, and the changes in the immunologic activity of TTX before and after the treatment were analyzed by competitive enzyme linked immunosorbent assay (C-ELISA). The carboxyl and amino groups on the surface of L. rhamnosus cells were masked by chemical treatment, and Fourier transform infrared spectroscopy (FTIR) was used to analyze changes in the chemical bond vibration and functional groups on the cell surface. The results showed that activated, thermally inactivated and broken L. rhamnosus cells could reduce the immunologic activity of TTX, indicating no correlation between the cell activity and the changes in the immunologic activity of TTX. Extracellular polysaccharide-deficient cells, protoplasts, cell walls and cell wall peptidoglycans could reduce the immunologic activity of TTX by up to 47%. Masking of carboxyl groups on the cell surface of L. rhamnosus significantly decreased the percentage reduction in the immunologic activity of TTX to 18%, while masking of amino groups had no significant effect (P > 0.05). The binding of TTX to carboxyl groups of peptidoglycan in the cell wall of L. rhamnosus probably contributed to the reduction of TTX immunologic activity.

Key words: tetrodotoxin; Lactobacillus rhamnosus; reduction; immunologic activity