鼠李糖乳杆菌对河豚毒素的免疫活性消减作用方式

为探究鼠李糖乳杆菌（Lactobacillus rhamnosus）对河豚毒素（tetrodotoxin，TTX）免疫活性的消减作用方式和可能作用位点，分别采用活化、热灭活和破碎的鼠李糖乳杆菌以及去除胞外多糖、原生质体、细胞壁和肽聚糖的分离样品，与TTX标准品在37 ℃孵育1 h，使用竞争性酶联免疫吸附法分析作用前后TTX的免疫活性变化。通过化学处理掩蔽鼠李糖乳杆菌表面的羧基和氨基，采用傅里叶变换红外光谱（Fourier transform infrared spectroscopy，FTIR）分析菌体表面的化学键振动类型和官能团变化情况。结果发现，活化、热灭活和破碎后的鼠李糖乳杆菌均可消减TTX的免疫活性，因此TTX免疫活性的变化和鼠李糖乳杆菌的活性无关。各分离样品对TTX的消减作用表明肽聚糖成分对TTX免疫活性的消减率最高可达到47%。FTIR分析发现鼠李糖乳杆菌表面羧基掩蔽后可显著降低TTX免疫活性的消减率至18%，而掩蔽氨基则对作用前后的TTX消减率影响无显著差异（P＞0.05）。实验表明，消减TTX免疫活性的原因可能为TTX与鼠李糖乳杆菌表面肽聚糖上的羧基结合。

Immunosuppressive Effect and Mode of Action of Lactobacillus rhamnosus on Tetrodotoxin

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.