Nair T S, Prieskorn D M, Miller J M, Dolan D F, Raphael Y, Carey T E
Kresge Hearing Research Institute 6028, Department of Otolaryngology/Head and Neck Surgery, The University of Michigan, Ann Arbor 48109-0506, USA.
Hear Res. 1999 Mar;129(1-2):50-60. doi: 10.1016/s0378-5955(98)00220-2.
Intracochlear infusion of the KHRI-3 monoclonal antibody results in in vivo binding to guinea pig inner ear supporting cells, loss of hair cells and hearing loss. To further characterize the basis for KHRI-3-induced hearing loss, antibody was produced in a bioreactor in serum-free medium, affinity purified, and compared to conventionally prepared antibody by infusion into the scala tympani using mini-osmotic pumps. In vivo antibody binding was observed in 10 of 11 guinea pigs. A previously unreported pattern of KHRI-3 antibody binding to cells involved in scar formation was noted in five guinea pigs. All but one of the KHRI-3-infused animals demonstrated a hearing loss of > 10 dB in the treated ear. In five of 11 animals the threshold shift was 30 dB or more, and all had hair cell losses. In one guinea pig infused with 2 mg/ml of antibody, the organ of Corti was absent in the basal turn of the infused ear. This ear had a 45-50 dB threshold shift but, curiously, no detectable antibody binding in the residual organ of Corti. Organ of Corti tissue was fragile in antibody-infused ears. Breaks within the outer hair cell region occurred in 5/11 infused ears. The contralateral ears were normal except for one noise-exposed animal that demonstrated hair cell loss in the uninfused ear. Three animals were exposed to 6 kHz noise (108 dB) for 30 min on day 7. Antibody access to the organ of Corti may be increased in animals exposed to noise, since the strongest in vivo binding was observed in noise-exposed animals. Loss of integrity of the organ of Corti seems to be the primary mechanism of inner ear damage by KHRI-3 antibody. The binding of KHRI-3 antibody in new scars suggests a role of the antigen in scar formation. Antibodies with binding properties similar to KHRI-3 have been detected in 51% of patients diagnosed with autoimmune sensorineural hearing loss; thus, it seems likely that such autoantibodies also may have pathologic effects resulting in hearing loss in humans.
向豚鼠耳蜗内注射KHRI-3单克隆抗体可导致其在体内与内耳支持细胞结合，毛细胞丧失及听力损失。为进一步明确KHRI-3所致听力损失的机制，在无血清培养基的生物反应器中制备抗体，进行亲和纯化，并通过微型渗透泵向鼓阶内注射，将其与传统制备的抗体进行比较。11只豚鼠中有10只观察到体内抗体结合。在5只豚鼠中发现了KHRI-3抗体与参与瘢痕形成的细胞结合的一种此前未报道的模式。除1只动物外，所有接受KHRI-3注射的动物治疗耳的听力损失均>10 dB。11只动物中有5只的阈值偏移为30 dB或更高，且均有毛细胞丧失。在1只注射2 mg/ml抗体的豚鼠中，注射耳基底转的柯蒂氏器缺失。该耳的阈值偏移为45 - 50 dB，但奇怪的是，在残留的柯蒂氏器中未检测到抗体结合。注射抗体的耳中柯蒂氏器组织很脆弱。11只注射耳中有5只在外毛细胞区域出现断裂。对侧耳均正常，只有1只暴露于噪声的动物在未注射耳中出现毛细胞丧失。3只动物在第7天暴露于6 kHz噪声（108 dB）30分钟。在暴露于噪声的动物中观察到最强的体内结合，这可能会增加抗体进入柯蒂氏器的机会。柯蒂氏器完整性的丧失似乎是KHRI-3抗体导致内耳损伤的主要机制。KHRI-3抗体在新形成的瘢痕中的结合表明该抗原在瘢痕形成中起作用。在51%被诊断为自身免疫性感音神经性听力损失的患者中检测到具有与KHRI-3相似结合特性的抗体；因此，这类自身抗体似乎也可能具有导致人类听力损失的病理作用。
