Evolution and clinical significance of the T cell proliferative and cytokine response directed against the fibronectin binding antigen 85 complex of bacillus Calmette-Guerin during intravesical treatment of superficial bladder cancer

Purpose: The antitumorigenic effect of intravesical bacillus Calmette-Guerin (BCG) in superficial bladder cancer was reported to be initiated by the attachment of BCG to the bladder wall via fibronectin. The antigen 85 complex secreted in BCG culture filtrate binds specifically to fibronectin and is a powerful T cell stimulus. Therefore, we investigated the evolution and clinical significance of the cellular proliferative response and cytokine production during intravesical BCG therapy against this purified antigen 85 complex. Materials and Methods: Evolution of the lymphoproliferation, interleukin-2 and interferon-gamma production of peripheral blood lymphocytes against tuberculin (purified protein derivative), purified antigen 85, BCG culture filtrate, whole BCG bacilli and pokeweed mitogen was tested before and after 6 weekly intravesical BCG instillations in 29 patients with superficial bladder cancer at intermediate or high risk for recurrence. Results: A major increase in the lymphoproliferative response against purified protein derivative, antigen 85, BCG culture filtrate, whole BCG and pokeweed mitogen was observed in 69.0, 65.5, 79.3, 48.3 and 65.3% of the patients, respectively, analyzed after BCG therapy. Reactivity returned to baseline values at 6 months of followup. Of the patients who received a second BCG course because of tumor recurrence 66% had a novel increase in lymphoproliferation against antigen 85. An increase in the production of interleukin-2 and interferon-gamma by peripheral lymphocytes against antigen 85 was noted in 42.1 and 50% of the treated patients, respectively, after a single BCG course. During a mean followup of 23.11 months 48.5% of the patients remained tumor-free. No correlation could be found between the immunological response against any of the BCG antigens and the clinical evolution of the response. Conclusions: Intravesical BCG instillations induce a transient (less than 6 months) peripheral immune activation against several purified BCG antigens and among them the fibronectin binding antigen 85 complex. Reactivation is observed in most cases after additional BCG courses. The absence of long lasting immune activation after a single 6-week course of BCG could be related to the increased clinical efficacy observed with BCG maintenance instillations.