Outer membrane protein A mediates Klebsiella pneumoniae penetration of the blood-brain barrier and induces bacterial meningitis

Klebsiella pneumoniae is an important meningeal pathogen. Penetration of the blood-brain barrier (BBB) is a prerequisite for K. pneumoniae meningitis, although the underlying mechanisms remain unclear. Our study found that outer membrane protein A (OmpA), a virulence factor of K. pneumoniae, facilitates BBB penetration and induces K. pneumoniae meningitis. Experimental results revealed that the mucoviscosity, biofilm formation, capsular polysaccharide production, serum resistance, in vitro competitiveness, and motarlity rates in Galleria mellonella were markedly reduced in an ompA deletion strain (FK3907 ΔompA). In a mouse meningitis model, significant reductions in bacterial loads, mortality rate, clinical symptoms, and brain tissue damage were observed in mice infected with FK3907 ΔompA compared to FK3907 (wild-type) and FK3907 ΔompA+ompA strains. Furthermore, the wild-type strain demonstrated a markedly enhanced ability to disrupt the BBB both in vitro and in vivo compared to the FK3907 ΔompA strain. This enhancement involved not only the rearrangement of F-actin in bEnd.3 cells but also the activation of an inflammatory cytokine storm. Importantly, the wild-type strain exhibited significantly enhanced adhesion, invasion, and intracellular proliferation within RAW264.7 cells. A wound healing assay indicated that wild-type strain promoted RAW264.7 cell migration. Collectively, we identified OmpA as a required virulence factor and essential pathogenic factor for K. pneumoniae. It promotes K. pneumoniae penetration BBB via transcellular pathway, trojan horse pathway, and pro-inflammatory pathway. Our study improves an in-depth understanding for K. pneumoniae penetration BBB from the perspective of bacterial-host interactions, highlighting OmpA as a potential target for intervention in K. pneumoniae meningitis.