Wzi regulates host innate immunity to promote Klebsiella pneumoniae survival in a CPS-dependent and -independent manner

Klebsiella pneumoniae is a major pathogen that causes a variety of human infections, posing a significant public health threat. Understanding its pathogenesis is essential for devising effective treatment strategies. In this study, we aim to identify critical virulence factors in K. pneumoniae through analyzing virulence-associated genes that were identified in three transposon mutagenesis libraries. Two genes, wzi and kvrB, are consistently detected across these libraries, indicating their potential as critical virulence factors. While Wzi has usually been implicated in virulence through CPS, its actual function in K. pneumoniae pathogenicity has rarely been explored. Wzi deficiency reduces CPS production in K. pneumoniae, contrasting with its effect in Escherichia coli. Importantly, Wzi exerts a pivotal role in K. pneumoniae pathogenicity in vitro and in vivo, functioning through both CPS-dependent and -independent pathways. Wzi inhibits the secretion of IFN-γ-related cytokines at early infection stage to promote K. pneumoniae survival in the host. Wzi triggers sustained neutrophil recruitment during infection through the upregulation of CXCL1 expression, resulting in the pulmonary barrier damage and increased K. pneumoniae invasion into the bloodstream. Concurrently, Wzi confers K. pneumoniae to counteract neutrophil-mediated clearance in a CPS-dependent manner. Sequence polymorphisms of wzi significantly affect bacterial resistance to serum killing, with alleles frequently associated with hypervirulent K. pneumoniae exhibiting the highest resistance. Collectively, our findings highlight that the dual role of Wzi as a CPS-dependent and -independent virulence factor that combats host clearance during K. pneumoniae infection, representing a promising target for the development of anti-infective treatment against the bug.