Fig. 7
Fresh VoNPs elicited protective immunity in mice. a The bar represents the titers of the anti-Vo IgGs in the mice after vaccination with fresh VoNPs, Vo formulated with Al(OH)3 as a conventional adjuvant (Vo + Al), or soluble Vo alone. b The bar represents the titers of the anti-Vo IgG subtypes in the mice vaccinated with VoNPs. c Mice immunized with VoNPs, Vo + Al or Vo alone. The bar represents the survival of the mice after challenge with a lethal dose of E. coli K1 RS218. d The bar represents the percentage of initial body weight of the mice after challenge with a sublethal dose of E. coli K1 RS218. e The bar represents the number of bacteria per ml blood 48 h after challenge with a sublethal dose of E. coli K1 RS218. f The bar represents the number of bacteria per gram of spleen tissue 48 h after challenge with a sublethal dose of E. coli K1 RS218. BNP indicates the blank nanoparticle control. g Opsonophagocytic killing assay of anti-VoNP serum. The bar represents the percentage of killed bacteria in a series of dilutions. h The effects of anti-VoNP antibodies on bacterial attachment and invasion. The bar represents the mean value and the standard error of the number of total associated bacteria (left panel) and invading bacteria (right panel). n.s. no significant difference; *P < 0.05