OUTER-MEMBRANE PROTEIN-A OF ESCHERICHIA-COLI CONTRIBUTES TO INVASION OF BRAIN MICROVASCULAR ENDOTHELIAL-CELLS

Escherichia coli is the most common gram-negative bacteria causing men ingitis during the neonatal period, but it is unclear what microbial f actors mediate traversal of E. coli across the blood-brain barrier. Ou ter membrane protein A (OmpA), a highly conserved 35-kDa protein, was examined for its role in E. coli K1 invasion of brain microvascular en dothelial cells (BMEC). The invasive capability of the OmpA(+) strains was 25- to 50-fold greater than that of OmpA(-) strains, and the inva sive capability of OmpA(-) strains was restored to the level of the Om pA(+) strain by complementation with the ompA gene. Purified OmpA prot eins and polyclonal anti-OmpA antibodies inhibited the invasion of Omp A(+) E. coli into BMEC. Two short synthetic peptides (a hexamer, Asn-2 7-Glu-32, and a pentamer, Gly-65-Asn-69) generated from the N-terminal amino acid sequence of OmpA exhibited significant inhibition of OmpA( +) E. coli invasion, suggesting that these two sequences represent the OmpA domains involved in E. coli invasion of BMEC. These findings sug gest that OmpA is the first microbial structure identified to enhance E. coli invasion of BMEC, an important event in the pathogenesis of E. coli meningitis.