Analysis of absorption of Clostridium botulinum toxins from the small infestine

肉毒梭菌产生从A型到G型的7种免疫功能不同的神经毒素。所有类型的神经毒素的分子质量(MR)约为150 kDa。神经毒素与培养物或食品中的无毒成分有关，并成为被称为前体毒素的大复合体。B、C和D型菌株产生两种形式的祖细胞毒素，M(300 kDa，12S毒素)和L(500 kDa，16S毒素)，而A型菌株产生M，L和LL毒素。M毒素由一种神经毒素和一种没有血凝素(HA)活性的无毒成分组成，被描述为无毒的非HA。L毒素是由M毒素与透明质酸偶联而成。LL毒素是L毒素的二聚体。最近我们发现HA由四个亚组分组成，分别是HA1(~33 kDa)、HA2(~17 kDa)、HA3a(~23 kDa)和HA3b(~53 kDa)，而且C-L毒素比M毒素和神经毒素更能从小肠吸收。这一次，分析了A-L和-LL毒素(命名为HA^-PT)和重组的四个HA亚组分与红细胞或豚鼠小肠上皮细胞的结合。结果表明，HAβ-Ptx主要通过HA1与上皮细胞和红细胞结合，其受体为Galβ-1-4GlcNac。对于C型，L毒素似乎同时通过HA1和HA3b与细胞结合，HA1和HA3b的受体分别是唾液酸乳糖和唾液酸，通过对两个HA活性较低的突变株L毒素的分析和抗HA1单抗的制备，进一步证实了C-HA1对L毒素与细胞结合的重要性。

Clostridium botulinum strains produce seven immunologically distinct neurotoxins, from types A to G. The molecular mass (Mr) of all types of neurotoxins is approximately 150 kDa. The neurotoxins are associated with non-toxic component in cultures or in foods, and become large complexes designated progenitor toxins. Type, B, C, and D strains produce two forms of progenitor toxin, M (300 kDa, 12S toxin) and L (500 kDa, 16S toxin), and type A produces M, L, and LL toxins. The M toxin consists of a neurotoxin and a non-toxic component showing no haemagglutinin (HA) activity, which is described as non-toxic non-HA. The L toxin is formed by conjugation of M toxin with HA. The LL toxin is a dimer of L toxin. Recently we found that HA consists of four subcomponents designated HA1 (~33 kDa), HA2 (~17 kDa), HA3a (~23 kDa), and HA3b (~53 kDa), and that type C-L toxin is effectively absorbed from the small intestine than M toxin and neurotoxin. This time, binding of A-L and -LL toxins (designated HA^+-PT) and recombinant four HA subcomponents to erythrocytes or the epithelial cells of guinea pig-small intestine were analyzed. It became clear that HA^+-PTX bound epithelial cells and erythrocytes mainly via HA1, and its receptor was Galβ-1-4GlcNac. In case of type C, it seemed that L toxin bound to the cells via both HA1 and HA3b, and the receptor of HA1 and HA3b was sialyl lactose and sialic acid, respectively.The importance of C-HA1 for the binding of L toxin to the cells was further confirmed by analysing two mutant L toxins with low HA activity and by preparing monoclonal antibodies against HA1.