Soluble Programmed Cell Death-1 is a Novel Predictor of HBsAg Loss in Chronic Hepatitis B Patients When Long-Term Nucleos(t)ide Analog Treatment is Discontinued

Purpose: The immunoinhibitory receptor, programmed death 1 (PD-1), plays a critical role in immune suppression during chronic viral infection. The significance of circulating soluble PD-1 (sPD-1) in patients with chronic hepatitis B who have discontinued longterm nucleos(t)ide analog (NA) treatment remains unknown. Patients and Methods: A prospective cohort study was conducted using serial blood samples from chronic hepatitis B patients who discontinued long-term NA treatment. The current analysis included 115 non-cirrhotic patients with HBV DNA negative and HBsAg positive at the moment of NA discontinuation. Levels of sPD-1 were measured in all available samples using sandwich enzyme-linked immunoassay. Results: Sixty-two patients experienced a clinical relapse and 14 occurred HBsAg loss, with 8-year cumulative rates of 56.6% and 23.4%, respectively. Time-dependent receiver operating characteristic curve analysis for sPD-1 derived 156 pg/mL, which is equivalent to the detectable threshold, as an optimal cut-off value for predicting 8-year clinical relapse. Patients with detectable sPD-1 at end of treatment (EOT) had a significant lower incidence of clinical relapse (48% vs 67%, hazard ratio [HR] 0.454, p = 0.006), but a remarkable higher probability of HBsAg loss (33.7% vs 2.4%, HR 9.17, p = 0.038), compared to those who with undetectable sPD-1, respectively. Conclusion: EOT sPD-1 levels predicted clinical relapse and HBsAg loss after treatment discontinuation and may help to guide a finite NA treatment plan for patients with chronic hepatitis B virus infection.