Gene-dose-dependent roles of DEFA1A3in the neutralization of uropathogenic Escherichia coli

Genetic polymorphisms of the human genome provide information about disease susceptibility and autoimmunity. Genetic variations involving the innate immune system have the potential to improve the effectiveness of diagnosis and treatment of urinary tract infections in children and adults. DNA copy number variations (CNVs) of DEFA1A3, which encodes for antimicrobial peptides α-defensin 1–3, have been associated with recurrent UTI risk in children with vesicoureteral reflux (VUR). α-Defensins 1–3 are pleiotropic antimicrobial peptides with bactericidal and immunomodulatory properties. Due to the absence of a gene ortholog in mice, traditional murine models to study the effect of DEFA1A3CNVs are lacking. Our objective is to explore the gene-dosage pleiotropic effects of the DEFA1A3locus by utilizing a UTI-challenged transgenic mouse model expressing variable copies of the human gene. To model murine UTIs, uropathogenic E. coli(UPEC) pyelonephritis strain (CFT073) or vehicle volume was injected transurethrally into DEFA4/4, DEFA4/0, and DEFA0/0mice. Urinary tract organs were analyzed for quantifiable bacterial growth, immune cell frequencies, and antimicrobial response gene expression array. Kidney bacterial clearance effects are proportional to gene-dosage; gradually decreasing colonization in mice between DEFA4/4(71%), DEFA4/0(57%), and DEFA0/0(43%) genotypes. The kidney immune cells displayed differential mRNA expression of pro-inflammatory genes Il1βand Il6genes as well as phagocytic genes Rac1and Lyz2between the infected mice genotypes. Our findings support pleiotropic gene-dosage protective roles of the human DEFA1A3gene in a murine model of UTI-induced pyelonephritis. Supported by the grants from NIH (R01 DK117934 & R01 DK106286 )