In vivo binding and hearing loss after intracochlear infusion of KHRI-3 antibody

Abstract

The IgG1 mouse monoclonal antibody (MAb) KHRI-3, binds to an antigen of 65–68 kDa expressed on inner ear supporting cells in guinea pigs. We previously showed [Nair et al. (1995) Monoclonal antibody induced hearing loss. Hear. Res. 83, 101–113] that mice carrying the KHRI-3 hybridoma develop high frequency hearing loss and loss of hair cells in the basal turn suggesting that this MAb causes immune-mediated sensorineural hearing loss. To evaluate the specificity of this effect, sterile KHRI-3 and control IgG1 preparations were infused directly into the guinea pig cochlea using Alzet® mini-osmotic pumps. Assessments included: (1) hearing, measured by click auditory brain stem responses (ABRs); (2) in vivo antibody binding; and (3) the structural integrity of the organ of Corti. Nine animals were infused with KHRI-3 preparations and 5 controls were infused with control IgG1. Four guinea pigs given KHRI-3 developed 25–55 dB hearing loss. Control animals showed no difference from baseline. In vivo binding of KHRI-3 was detected in the organ of Corti in 6 of the 9 animals, including all 4 that had hearing loss. No staining was observed with control antibody. Confocal microscopy revealed that the in vivo KHRI-3 antibody binding pattern was identical to that obtained by incubating fixed tissue in vitro with KHRI-3. Histologic examination revealed an increased frequency of hair cell loss in KHRI-3 treated ears when compared to either the contralateral ears of the same guinea pigs or the IgG1 treated ears of control animals. The lesions in the infused ears of guinea pigs were scattered throughout the cochlea from base to apex. These experiments demonstrate the following points: (1) Antibodies can be chronically infused directly into the cochlea of living animals. (2) The KHRI-3 antibody binds to live supporting cells within the organ of Corti. (3) Infusion of an inner ear specific antibody affects auditory function. (4) The infusion of irrelevant antibody had no effect on the structure or function of the ear. This system provides an animal model for further studies of antibody-induced sensorineural hearing loss.