Downregulation of bactericidal peptides in enteric infections: A novel immune escape mechanism with bacterial DNA as a potential regulator

Antibacterial peptides are active defense components of innate Immunity. Se veral studies confirm their importance at epithelial surfaces as immediate barrier effecters in preventing Infection. Here we report that early in Shi gella spp. infections, expression of the antibacterial peptides LL-37 and h uman beta -defensin-1. is reduced or turned off. The downregulation is dete cted in biopsies from patients with bacillary dysenteries and in Shigella- infected cell cultures of epithelial and monocyte origin. This downregulati on of immediate defense effecters might promote bacterial adherence and inv asion into host epithelium and could be an important virulence parameter. A nalyses of bacterial molecules causing the downregulation indicate Shigella plasmid DNA as one mediator.