Peripheral Purified Protein Derivate Specific T Cell Immunoreactivity Dynamics in Non-Muscle Invasive Bladder Cancer Patients Receiving Bacillus Calmette-Guerin Instillation Treatment

Abstract

Background : Intravesical Bacillus Calmette-Guerin (BCG) instillation is recommended as an adjuvant therapy for intermediate-risk and high-risk non-muscle invasive bladder cancer (NMIBC) after transurethral resection of bladder tumor (TURBt). The aim of this study was to investigate peripheral immune responses induced by intravesical BCG instillation and to figure out the putative indicators for predicting the recurrence of NMIBC. Methods: Thirty-six NMIBC patients receiving BCG instillation were recruited in the study among which 19 patients were followed up from the start of the instillation.  Whole blood was collected before BCG instillation. Peripheral blood mononuclear cells (PBMCs) were isolated and stimulated with purified protein derivate (PPD) in vitro. PPD-specific cellular responses were evaluated by an IFN-γ releasing assay. Cytokines-secreting CD4+ and CD8+ T cells were detected by flow cytometry. Findings: Intravesical BCG instillation evoked a dramatic increase in IFN-γ producing spot-forming units (SFUs) in PBMCs upon PPD stimulation when compared to those without BCG instillation, together with higher percentages of IFN-γ, IL-2 and IL-17A producing T cells in the periphery. In the follow-up study, IFN-γ producing SFUs elevated rapid after one instillation of BCG and maintained later. However, PPD-specific cytokine producing CCD4+ and CD8+ T cells reached the plateau after two times of BCG instillation. Interestingly, the frequencies of PPD-specific cytokine secreting CD4+ and CD8+ T cells decreased dramatically after induction treatment and restored after BCG re-instillation except IL-17A at the maintenance phase. Of note, more dramatic increase in PPD-specific IFN-γ and IL-2 releasing CCD4+ and CD8+ T cells after one and two BCG instillations was observed in refractory NMIBC patients. Interpretation: Regional BCG instillation can induce peripheral PPD-specific immune responses whereas attenuated after the termination of the instillation. The rapid and transient increase in peripheral PPD-specific Th1-type cytokine producing T cells, however, might be unfavorable indicators associated with the refractory of NMIBC. Funding Information: This work was supported by grants from Chinese National Mega Science and Technology Program on Infectious Diseases (2018ZX10731301-001-004, 2018ZX10302301-002-002 and 2013ZX10003007-003-003) and Shanghai Academic Research Leader Project (18XD1403300). Declaration of Interests: The authors report no conflict of interest. Ethics Approval Statement: All the patients have signed the informed consent forms. The study was approved by the Ethical Committee of Xinhua Hospital. The procedures performed in this study were in accordance with the 1964 Helsinki declaration.