Broadly reactive human CD4 + T cells against Enterobacteriaceae are found in the naïve repertoire and are clonally expanded in the memory repertoire

Abstract

Enterobacteriaceae are a large family of Gram-negative bacteria that includes both commensals and opportunistic pathogens. The latter can cause severe nosocomial infections, with outbreaks. This T cell subset was severely reduced in septic patients with K. pneumoniae bloodstream infection who also selectively lacked circulating K. pneumoniereactive to several Enterobacteriaceae species. These cross-reactive Th cell clones were expanded in vivo and a large fraction of them recognized the conserved outer membrane protein A (OmpA) antigen. Interestingly, Enterobacteriaceae broadly reactive T cells were also prominent among in vitro primed T cells. Collectively, these data point to the existence of immunodominant T cell epitopes shared among different Enterobacteriaceae species and targeted byT cells that are readily found in the pre-immune repertoire and are clonally expanded in the memory repertoire.