Protection against H. suis challenge after prophylactic intranasal immunization. Bacterial load is illustrated as log (10) of H. suis copies/mg stomach tissue. Individual mice are illustrated as dots around the mean (lines). DL: detection limit of 43.9 copies mg-1. Significant differences between immunized (rUreB, rNapA and lysate) and sham-immunized, infected animals are noted by *** p < 0.001. Results of negative controls were all situated below DL.