Enhanced immune response in the urinary tract of the rat following vaginal immunization

Induction of protective immunity after escherichia coli bladder infection in primates. Dependence of the globoside-specific P-fimbrial tip adhesin and its cognate receptor

Clinical observations suggest that immune mechanisms affect etiology and course of recurrent cystitis. A primate infection model was used to show that primary bladder infection with a uropathogenic P-fimbriated strain (binding to globoside present in the bladder wall) protects against rechallenge with homologous as well as heterologous Escherichia coli strains for up to 5-6 mo. In contrast, mutant derivatives producing P-fimbriae either lacking the tip adhesin protein or carrying an adhesin for which no bladder receptor was present, were unable to induce protection, even though they generated bladder infections of similar duration as the wild type. Therefore, the protective effect mediated by the adhesin seemed to depend upon the presence of its cognate receptor. Since the wild strain also mediated protection against mutants that lacked the adhesin, our data suggest that the globoside-binding PapG adhesin acts as an adjuvant during infection to enhance a specific response against other bacterial antigens. In fact, the globoside-binding strain DS17, but not the mutant DS17-1, unable to bind to membrane-bound globoside, elicited a secretory IgA response to LPS in urine. These in vivo findings suggest that bacterial adhesin-ligand interactions may have signaling functions of importance for the immune response.

Secretory immunoglobulin A and inhibitory activity of bacterial adherence to epithelial cells in urine from patients with urinary tract infections

To assess the role of local immune response against bacterial invasion of the urinary tract we studied 168 patients with bacteriuria. Urinary secretory immunoglobulins A (sIgA) were measured using radial immunodiffusion or enzyme-linked immunosorbent assay (ELISA). In particular, ELISA is a very suitable assay for measuring the low levels of sIgA in urine. Furthermore, we used a quantitative in vitro adherence assay to investigate the attachment of Escherichia coli to human uroepithelial cells after incubation in urine from patients with urinary tract infection. Urine from patients with ileocystoplasty was significantly more potent in inhibiting bacterial adherence than was urine from other groups of patients with urinary tract infection. The presence of high urinary sIgA may help explain the increased antiadherence activity of urine in patients with ileocystoplasty. Mean urinary sIgA in patients with upper urinary tract infection was higher than in patients with uncomplicated infection in the lower urinary tract. Alterations in mucosal immune functions may account for the propensity toward bacterial colonization in women prone to uncomplicated urinary tract infection.

Decreased immunologic responsiveness following intensified vaginal immunization against urinary tract infection

In an attempt to further increase the protective effect of vaginal immunization against urinary tract infections in Cynomolgus monkeys, the immunogen of killed E. coli was given more times, in larger amounts, and with the adjuvant MDP. Instead of increasing the protective effect, no protective effect on induced cystitis was observed. In addition, rises in urinary and serum immunoglobulins previously observed after vaginal immunization and induced cystitis were lessened. These observations appear to correspond with the classical concepts of immunologic unresponsiveness.

Local and systemic antibody responses accompany spontaneous resolution of experimental cystitis in cynomolgus monkeys

Cynomolgus monkeys were infected intravesically with two different strains of uropathogenic Escherichia coli. A quantitative enzyme-linked immunosorbent assay method was used to monitor secretory and serum immune responses to the induced cystitis. Anti-E. coli secretory immunoglobulin A (sIgA) and IgG urinary antibodies were generated as a result of the cystitis. Urinary sIgA levels against the E. coli strains tested were highest at 25 to 31 days after cystitis induction, and urinary IgG levels were highest at 31 to 45 days after induction. Anti-E. coli IgM was not detected in the urine. The antibody response in serum was characterized by IgM, IgG, and IgA immunoglobulin production. IgM levels in serum rose at 14 days after cystitis induction and were sustained for another 1 to 2 weeks. Increases in serum IgG levels began at 7 to 21 days of infection and persisted in some cases for up to 70 days. Serum IgA to the infecting E. coli was produced within 1 week after cystitis induction and remained at elevated levels throughout the course of the cystitis. These results demonstrate the capacity of primates to spontaneously resolve a cystitis and to mount both local and systemic immune responses against the infecting bacteria.

Vaginal immunization against induced cystitis in monkeys

Cynomolgus monkeys received either vaginal immunization with formalin-killed E. coli or vaginal instillation of excipient without the bacteria. At 2, 7, 14 and 21 days after induction of a urinary tract infection with live E. coli, immunized monkeys showed enhanced clearance of bacteriuria compared to non-immunized controls. Immunized monkeys also showed increased levels of urinary anti-E. coli IgA and IgG after the immunizing and infecting procedures. Induction of heightened local immunity by vaginal immunization may lessen host susceptibility to urinary tract infections.

A quantitative in vivo assay for bacterial adherence to the urethra

Bacterial adherence to urinary tract mucosal surfaces is thought to be the initiating event in ascending urinary tract infection. To study this process, we have developed a physiologic, quantitative, in vivo assay for bacterial adherence to the urethra. The effect of local (vaginal mucosa) immunization on the adherence of E. coli to the urethra was studied. Local immunization with a formalinized E. coli vaccine significantly reduced the capacity of viable cells of the immunizing strain to adhere to the urethra. Immunization-induced decrease in bacterial adherence to urethral mucosa is in agreement with our previous observations that immunization of the vaginal mucosa decreases the adherence of E. coli to the rat bladder. These data provide further evidence of a protective effect from local immunization against ascending urinary tract infection. No obvious change in indigenous urethral flora occurred after mucosal immunization.