Rolfe R D, Song W
Department of Microbiology and Immunology, School of Medicine, Texas Tech University Health Sciences Center, Lubbock 79430, USA.
J Med Microbiol. 1995 Jan;42(1):10-9. doi: 10.1099/00222615-42-1-10.
Clostridium difficile is isolated from the intestinal tracts of > 50% of healthy infants. The mechanism by which intestinal colonisation of infants by toxigenic C. difficile is generally asymptomatic is unknown but may reflect the presence in human milk of neutralising activity against C. difficile toxin A. On this basis, the ability of human milk to inhibit the binding of toxin A to a purified hamster brush border membrane receptor was determined. Ten milk samples from healthy volunteers in various stages of lactation inhibited the binding of toxin A to the receptor by an average of 90%. Heating and dialysis did not significantly alter the inhibitory activity of any of the milk samples. Human milk protected adult hamsters against a lethal challenge with toxin A but had no effect on the cytotoxic activity of the toxin. SDS-PAGE and ligand blot analyses showed that there were at least four distinct factors in human milk that specifically bound toxin A. Thiophilic adsorption chromatography was used to separate immunoglobulin from non-immunoglobulin components of human milk. IgA was the only immunoglobulin detected in human milk and > 90% of this immunoglobulin was recovered after purification by thiophilic adsorption. Both the unbound non-immunoglobulin and bound immunoglobulin fractions of human milk inhibited the binding of toxin A to the purified receptor. These results suggest that human milk may be important in protecting infants against C. difficile-associated intestinal disease.
在超过50%的健康婴儿肠道中可分离出艰难梭菌。产毒艰难梭菌在婴儿肠道中定植但通常无症状的机制尚不清楚，不过这可能反映出人乳中存在针对艰难梭菌毒素A的中和活性。基于此，测定了人乳抑制毒素A与纯化的仓鼠刷状缘膜受体结合的能力。来自处于不同泌乳阶段的健康志愿者的10份乳汁样本平均抑制毒素A与受体结合的比例达90%。加热和透析并未显著改变任何一份乳汁样本的抑制活性。人乳可保护成年仓鼠免受毒素A的致死性攻击，但对该毒素的细胞毒性活性没有影响。SDS - PAGE和配体印迹分析表明，人乳中至少有四种不同的因子可特异性结合毒素A。采用嗜硫吸附色谱法从人乳的非免疫球蛋白成分中分离出免疫球蛋白。IgA是在人乳中检测到的唯一免疫球蛋白，经嗜硫吸附纯化后，超过90%的该免疫球蛋白得以回收。人乳中未结合的非免疫球蛋白部分和结合的免疫球蛋白部分均抑制毒素A与纯化受体的结合。这些结果表明，人乳在保护婴儿免受艰难梭菌相关肠道疾病方面可能具有重要作用。
