NLRP3 mutation and cochlear autoinflammation cause syndromic and nonsyndromic hearing loss DFNA34 responsive to anakinra therapy.

The NLRP3 inflammasome is an intracellular innate immune sensor that is expressed in immune cells, including monocytes and macrophages. Activation of the NLRP3 inflammasome leads to IL-1ß secretion. Gain-of-function mutations of NLRP3 result in abnormal activation of the NLRP3 inflammasome, and cause the autosomal dominant systemic autoinflammatory disease spectrum, termed cryopyrin-associated periodic syndromes (CAPS). Here, we show that a missense mutation, p.Arg918Gln (c.2753G > A), of NLRP3 causes autosomal-dominant sensorineural hearing loss in two unrelated families. In family LMG446, hearing loss is accompanied by autoinflammatory signs and symptoms without serologic evidence of inflammation as part of an atypical CAPS phenotype and was reversed or improved by IL-1ß blockade therapy. In family LMG113, hearing loss segregates without any other target-organ manifestations of CAPS. This observation led us to explore the possibility that resident macrophage/monocyte-like cells in the cochlea can mediate local autoinflammation via activation of the NLRP3 inflammasome. The NLRP3 inflammasome can indeed be activated in resident macrophage/monocyte-like cells in the mouse cochlea, resulting in secretion of IL-1ß. This pathway could underlie treatable sensorineural hearing loss in DFNA34, CAPS, and possibly in a wide variety of hearing-loss disorders, such as sudden sensorineural hearing loss and Meniere's disease that are elicited by pathogens and processes that stimulate innate immune responses within the cochlea.

Identification and molecular characterization of EatA, an autotransporter protein of enterotoxigenic Escherichia coli.

Enterotoxigenic Escherichia coli (ETEC) strains remain a formidable cause of diarrheal disease. To identify novel surface proteins of ETEC, we performed TnphoA mutagenesis of prototype ETEC strain H10407 and discovered a secreted protein not previously recognized in ETEC. DNA sequencing of the interrupted locus in mutant TnphoA.977 revealed a candidate 4,095-bp open reading frame without significant homology to commensal E. coli K-12 genomic DNA. Translation of this sequence revealed that it encoded a predicted peptide of 147.7 kDa that bears significant homology to members of the autotransporter family of bacterial virulence factors, particularly the serine protease autotransporters of the Enterobacteriaceae proteins. The gene identified in H10407, eatA (ETEC autotransporter A), encodes a potential serine protease motif (GDSGSP) in the secreted amino-terminal domain, and the predicted peptide shows more than 80% homology with SepA, a virulence protein secreted by Shigella flexneri. DNA hybridization and PCR demonstrated that eatA resides on the 92-kDa pCS1 virulence plasmid of H10407 and that it is present in multiple clinical ETEC strains. Immunoblots with antisera directed against a recombinant EatA passenger protein fragment identified a 110-kDa protein in supernatants purified from H10407 but not from the TnphoA.977 mutant or H10407-P, which lacks pCS1. EatA possesses serine protease activity that is abolished by mutations within a serine protease catalytic triad formed by residues H(134), D(162), and S(267). Finally, interruption of the eatA gene retarded fluid accumulation in the rabbit ileal loop model, suggesting that this autotransporter contributes to the virulence of ETEC.