title: Phosphate groups of lipid A are essential for Salmonella enterica serovar Typhimurium virulence and affect innate and adaptive immunity.
abstract: Lipid A is a key component of the outer membrane of Gram-negative bacteria and stimulates proinflammatory responses via the Toll-like receptor 4 (TLR4)-MD2-CD14 pathway. Its endotoxic activity depends on the number and length of acyl chains and its phosphorylation state. In Salmonella enterica serovar Typhimurium, removal of the secondary laurate or myristate chain in lipid A results in bacterial attenuation and growth defects in vitro. However, the roles of the two lipid A phosphate groups in bacterial virulence and immunogenicity remain unknown. Here, we used an S. Typhimurium msbB pagL pagP lpxR mutant, carrying penta-acylated lipid A, as the parent strain to construct a series of mutants synthesizing 1-dephosphorylated, 4'-dephosphorylated, or nonphosphorylated penta-acylated lipid A. Dephosphorylated mutants exhibited increased sensitivity to deoxycholate and showed increased resistance to polymyxin B. Removal of both phosphate groups severely attenuated the mutants when administered orally to BALB/c mice, but the mutants colonized the lymphatic tissues and were sufficiently immunogenic to protect the host from challenge with wild-type S. Typhimurium. Mice receiving S. Typhimurium with 1-dephosphorylated or nonphosphorylated penta-acylated lipid A exhibited reduced levels of cytokines. Attenuated and dephosphorylated Salmonella vaccines were able to induce adaptive immunity against heterologous (PspA of Streptococcus pneumoniae) and homologous antigens (lipopolysaccharide [LPS] and outer membrane proteins [OMPs]).
authors: Center for Infectious Diseases and Vaccinology, Biodesign Institute, Arizona State University, Tempe, Arizona, USA. Qingke.kong@asu.edu
authors: Qingke
authors: Q
authors: Kong
authors: David A
authors: DA
authors: Six
authors: Qing
authors: Q
authors: Liu
authors: Lillian
authors: L
authors: Gu
authors: Shifeng
authors: S
authors: Wang
authors: Praveen
authors: P
authors: Alamuri
authors: Christian R H
authors: CR
authors: Raetz
authors: Roy
authors: R
authors: Curtiss
mesh_terms: D056704:Adaptive Immunity; D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D007113:Immunity, Innate; D008050:Lipid A / Q000276:immunology / Q000633:toxicity*; D051379:Mice; D008807:Mice, Inbred BALB C; D010710:Phosphates / Q000378:metabolism / Q000633:toxicity*; D012480:Salmonella Infections / Q000276:immunology* / Q000382:microbiology / Q000473:pathology*; D022562:Salmonella Vaccines / Q000276:immunology; D012486:Salmonella typhimurium / Q000276:immunology* / Q000472:pathogenicity*; D013296:Streptococcus pneumoniae; D014613:Vaccines, Attenuated / Q000276:immunology; D014774:Virulence; D037521:Virulence Factors / Q000276:immunology / Q000633:toxicity*
chemical_list: D008050:Lipid A; D010710:Phosphates; D022562:Salmonella Vaccines; D014613:Vaccines, Attenuated; D037521:Virulence Factors