Ravoahangimalala O, Charles J F, Schoeller-Raccaud J
Institut Pasteur, Paris.
Res Microbiol. 1993 May;144(4):271-8. doi: 10.1016/0923-2508(93)90011-p.
Fourth instar larvae of Anopheles gambiae were intoxicated with doses of purified crystals from Bacillus thuringiensis serovar israelensis (Bti) corresponding to 50-fold the LC50 after 24 h. Midguts were dissected after various contact times, then processed for immuno-light and -electron microscopy. Immunodetection on thin sections was performed using affinity-purified rabbit IgG against Bti crystal CryIVD or CytA polypeptides, in combination with anti-rabbit IgG/peroxidase. Both polypeptides were detected by optical and electron microscopy after 15 min of contact with Bti crystals on the apical brush border of midgut cells, but only in the gastric caeca and posterior stomach. No specific signal was detected in the other parts of the midgut, i.e. the cardia cells and the anterior stomach. These results confirm that mosquito midgut cells are the primary target for the toxins and that binding to specific receptors on the apical microvilli membrane is the initial step of delta-endotoxin action.
用苏云金芽孢杆菌以色列变种（Bti）纯化晶体剂量对冈比亚按蚊四龄幼虫进行中毒处理，该剂量相当于24小时后半数致死浓度（LC50）的50倍。在不同接触时间后解剖中肠，然后进行免疫光镜和免疫电镜处理。在超薄切片上进行免疫检测时，使用针对Bti晶体CryIVD或CytA多肽的亲和纯化兔IgG，结合抗兔IgG/过氧化物酶。与Bti晶体在中肠细胞顶端刷状缘接触15分钟后，通过光学显微镜和电子显微镜均检测到这两种多肽，但仅在胃盲囊和后胃中检测到。在中肠的其他部分，即贲门细胞和前胃中未检测到特异性信号。这些结果证实，蚊虫中肠细胞是毒素的主要靶标，并且与顶端微绒毛膜上特定受体的结合是δ-内毒素作用的起始步骤。
