Primate Monocytes - CD14, CD16 - Ziegler-Heitbrock

Palmitoylation state impacts innate and acquired immunity in the Salmonella enterica serovar Typhimurium msbB mutant

Abstract

Lipopolysaccharide (LPS), composed of lipid A, core and O-antigen, is a major virulence factor of Salmonella enterica serovar Typhimurium, with lipid A being a major stimulator to induce the proinflammatory response via the TLR4/MD2/CD14 pathway. While Salmonella msbB mutants lacking the myristate chain in lipid A were investigated widely as an anti-cancer vaccine, inclusion of the msbB mutation in a Salmonella vaccine to deliver heterologous antigens has not yet been investigated. We introduced msbB mutation alone, or in combination with other lipid A acyl chain modification genes encoding PagL, PagP and LpxR into wild-type S. Typhimurium. msbB mutation reduced virulence while pagL, pagP and lpxR mutations did not affect virulence in the msbB mutant background when administered orally to BALB/c mice. Also, all mutants exhibited sensitivity to polymyxin B, but did not display sensitivity to deoxycholate. LPS derived from msbB mutants induced less inflammatory responses in human Mono Mac 6 and murine macrophage RAW264.7 cells in vitro. However, a msbB mutant did not decrease induction of inflammatory responses in mice compared to wild-type, whereas a msbB pagP mutant induced less inflammatory responses in vivo. The mutations were moved to an attenuated Salmonella vaccine strain to evaluate their effects on immunogenicity. Lipid A modification caused by the msbB mutation alone and in combination with pagL, pagP, and lpxR mutations led to higher IgA production in the vaginal tract, but still retained the same IgG titer level in serum to PspA, a testing antigen from Streptococcus pneumoniae, and to OMPs from Salmonella.