Fig. 5
Anti-F1 antigen IgG titres in mouse sera post-immunisation with human adenovirus vectors encoding signal sequence variants of the F1 antigen. Groups of 12 BALB/c mice were immunised with a sub-optimal dose of 1 × 107 infectious units of one of the human adenovirus serotype 5 (AdHu5) vectors encoding the Yersinia pestis F1 antigen with native signal sequence (SS), a heterologous N-terminal full-length (FL) SS, or a truncated form of the F1 antigen lacking any SS. Enzyme-linked immunosorbent assays were performed on serum samples taken at weeks A two and B four post-immunisation to determine the titres of anti-F1 antigen IgG in sera. The humoral response induced by the F1 antigen with native SS was superior to that induced by the incorporation of the heterologous FL SS to this antigen or its truncated form at both timepoints. Statistical comparisons were made using a Mann–Whitney U-test. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001