1 μg/well) or PLY (0.2 μg/well) or PsaA (0.1 μg/well). ELISA titres were calculated as the reciprocal of the highest serum dilution, which gave an absorbance of 0.3 above the background. Background absorbance was approximately 0.1 units. The levels of anti-PLY and eGFP within the mucosal lavage samples were determined by ELISA as described above except biotinylated IgA (Sigma) was used as the detection antibody. ELISA titres were calculated as
the reciprocal of the highest dilution that gave an absorbance of 0.2 above the background. For comparison of antibody titres and bacterial loads, the mean and SD of specific responses for each vaccine treatment group were calculated and the statistical significance determined by Krusal–Wallis with Dunn’s post-test (Nonparametric ANOVA; GraphPad Instat). In all experiments,
Bcr-Abl inhibitor p ≤ 0.05 was considered significant. p values are reported in the figure legends. SB431542 mw Recombinant proteins eGFP, eGFPPLY, eGFPΔ6PLY, PsaA, PsaAPLY, PsaAΔ6PLY and PLY were expressed and purified from E. coli. In each case, analysis by gel electrophoresis revealed a single protein of the expected size (see Table 2) that reacted with either antisera to eGFP, PLY or PsaA respectively. Fusion proteins were recognised by antisera to both proteins. Analysis of LPS indicated that levels of contamination were low (less than 5 IU/dose) and were considered to be insufficient to stimulate the immune system non-specifically. To determine whether conjugation of a protein to
PLY influenced the ability of the toxin to bind to cells, the proteins were tested in a standard haemolytic assay . The results shown in Fig. 1 indicate that conjugation of eGFP to PLY does not affect the capacity of the protein to lyse red blood cells. PsaAPLY demonstrated similar levels of activity in this assay. As expected, fusion of eGFP and PsaA to the non-toxic form of PLY resulted in conjugated proteins (eGFPΔ6PLY and PsaΔ6PLY respectively) that demonstrated no detectable haemolytic activity. Intranasal almost administration of the conjugate protein eGFPPLY resulted in a very rapid production of a statistically significant (p < 0.001) high levels of antibodies to eGFP ( Fig. 2a), which were detectable after a single administration of a relatively small dose of antigen (200 ng). In contrast, no anti-eGFP response was observed when equimolar quantities of PLY and eGFP were given as an admixed formulation. Mice immunised with the non-toxic recombinant protein eGFPΔ6PLY also had detectable antibodies to eGFP in the blood. These became detectable after the second vaccination but further boosting did not result in the same magnitude of the response seen with eGFPPLY. As expected, animals immunised with LT generated systemic and mucosal antibodies to the codelivered eGFP.