Cleaved Cochlin Sequesters Pseudomonas aeruginosa and Activates Innate Immunity in the Inner Ear

In the inner ear, endolymph fluid surrounds the organ of Corti, which is important for auditory function; notably, even slight environmental changes mediated by trauma or infection can have significant consequences. However, it is unclear how the immune response is modulated in these tissues. Here, we report the local immune surveillance role of cleaved cochlin LCCL (Limulus factor C, Cochlin, and Lgl1) during Pseudomonas aeruginosa infection in the cochlea. Upon infection, the LCCL domain is cleaved from cochlin and secreted into the perilymph. This cleaved fragment sequesters infiltrating bacteria in the scala tympani and subsequently recruits resident immune cells to eliminate the bacteria. Importantly, hearing loss in a cochlin knockout mouse model is remedied by treatment with a cochlin LCCL peptide. These findings suggest cleaved cochlin LCCL constitutes a critical factor in innate immunity and auditory function and may be a potential therapeutic target to treat chronic otitis media-induced hearing loss. [Display omitted] •Cleaved inner ear cochlin LCCL secretes to perilymph space post-bacterial infection•LCCL induces bacterial aggregation in the scala tympani•Spatiotemporal innate immune response by LCCL protects the sensory organ of Corti•LCCL rescues Coch−/− mouse post-Pseudomonas inner ear infection hearing loss Jung et al. show that the cleaved cochlin LCCL domain enhances innate immune responses in the inner ear by aggregating infiltrated bacteria and recruiting innate immune cells. This spatiotemporally protective function of LCCL protects hearing function in the organ of Corti against effects of bacterial invasion in the inner ear.