FIG. 4.
Vaccination against H. pylori with urease-expressing, recombinant Salmonella SL3261/pYZ97 is less protective in male than in female mice. (A) Mean ± standard errors of the means of urease-specific Ig levels in serially diluted serum prepared from male (diamonds) and female (circles) mice (n < 4) immunized with 107 (open symbols) or 109 CFU (solid symbols) of SL3261/pYZ97 3 weeks after infection with H. pylori. OD420nm, optical density at 420 nm. (B) H. pylori burden in vaccinated and control mice estimated as described for Fig. 2. Values correspond to means from individual determinations for four to six mice per group ± standard errors of the means. Statistical analysis of the difference between male and female mice by t tests yielded P values of 0.051 and 0.029 at the high- and low-dose inocula, respectively.