Serum immunoglobulin response and protection from homologous challenge by Proteus mirabilis in a mouse model of ascending urinary tract infection

We tested the hypothesis that experimental Proteus mirabilis urinary tract infection in mice would protect against homologous bladder rechallenge. Des pite production of serum immunoglobulin G (IgG) and IgM (median titers of 1 :320 and 1:80, respectively), vaccinated (infected and antibiotic-cured) mi ce did not show a decrease in mortality upon rechallenge; the survivors exp erienced only modest protection from infection (mean log,, number of CFU of P. mirabilis Nal(r) HI4320 per milliliter or gram in vaccinated mice versu s sham-vaccinated mice: urine, 100-fold less [3.5 versus 5.5; P = 0.13]; bl adder, 100-fold less [3.1 versus 5.1; P = 0.066]; kidneys, 40-foId less [2. 7 versus 4.3; P = 0.016]). Western blots using protein from the wild-type s train and isogenic mutants demonstrated antibody responses to MR/P and PMF fimbriae and flagella. There was no correlation between serum IgG or IgM le vels and protection from mortality or infection. There was a trend toward e levated serum IgA titers and protection From subsequent challenge (P greate r than or equal to 0.09), although only a few mice developed significant se rum IgA levels. We conclude that prior infection with P. mirabilis does not protect significantly against homologous challenge.