1. Coexpression of the adjuvant mmCT with chromosomal RΔ-CTB attenuates the immune response to CTB. (A) Genotype of an O139 serotype vaccine strain in which the entire CTX phage, including the recombination sites, as well as the tcpA gene has been deleted.
Coexpression of the adjuvant mmCT with chromosomal RΔ-CTB attenuates the immune response to CTB. (A) Genotype of an O139 serotype vaccine strain in which the entire CTX phage, including the recombination sites, as well as the tcpA gene has been deleted. Constitutive expression of genes encoding mmCT is driven by the native, chromosomal lacZ promoter. CTB is genetically coupled to the 3′ end of rbmA carrying R116A and R234A mutations and placed under the native rbmA promoter on the chromosome (cRΔ-CTB). (B) Vaccination scheme for the live attenuated vaccine with chromosomal RΔ-CTB and constitutive expression of mmCT. Open triangles indicate vaccination. Arrows indicate blood and stool sample collection. (C and D) Nanograms of LPS-specific antibodies per milliliter of serum or micrograms per total IgA in stool (C) and nanograms of CTB-specific antibodies per milliliter of serum or per microgram of total IgA in stool (D) after immunization with a live attenuated vaccine strain expressing cRΔ-CTB and mmCT. Data were log transformed prior to calculation of statistical significance. n.s., not significant (P ≥ 0.05), *, P ≤ 0.05, **, P ≤ 0.01, ***, P ≤ 0.001, and ****, P ≤ , using one-way ANOVA and Dunnett’s multiple-comparison test. Horizontal bars mark the mean. Each vaccination group included 10 mice. (E and F) Comparison of (E) vibriocidal titers and (F) LPS-specific IgG1 and IgG2a for vaccines expressing cRΔ-CTB with or without mmCT at days 56 and 180. Differences were not statistically significant.
Julie Liao et al. mSphere 2018; doi: /mSphere