Clinical cure in an occult hepatitis B virus infection patient on sequential therapy: a case report

Abstract Background Occult hepatitis B virus infection (OBI) is characterized by the presence of replication-competent hepatitis B virus DNA (HBV DNA) in the liver and/or blood of a individual who is currently negative for hepatitis B surface antigen (HBsAg) by standard tests. There is increasing evidence that occult HBV infection is associated with advanced chronic liver disease, especially hepatocellular carcinoma, and that people with occult HBV infection can transmit HBV infection. Despite growing concerns about its transmissibility and clinical impact, occult HBV infection has received limited attention in the hepatitis elimination agenda. While the pursuit of functional cure for hepatitis B may lead to the conversion from overt HBV infection to OBI, few cases of this have been reported to date. This case report presents a patient with chronic hepatitis B who initially converted to occult hepatitis B infection with sequential combination therapy and ultimately achieved clinical cure. Case presentation The patient is a 28-years old male from China diagnosed with hepatitis B virus infection. In 2012, he presented with abnormal liver function and was initially treated with short-acting interferon; however, this approach yielded poor results. Consequently, he was switched to Entecavir (ETV) antiviral therapy.In August 2019, laboratory tests indicated an HBsAg level of 255.35 IU/ml, while HBV DNA was below the lower limit of detection (<500 IU/ml). The patient hadno history of hypertension, cardiovascular disease, diabetes mellitus, or cerebrovascular disease, and was subsequently started on a combination therapy of ETV and pegylated interferon (PEG-IFN). By April 2020, follow-up tests revealed HBV DNA at 2.24 log10 IU/ml and HBsAg reduced to 0.42 IU/ml. At this point, the treatment regimen was adjusted to a combination therapy of tenofovir alafenamide (TAF) and PEG-IFN. Six months later, HBsAg turned negative, HBsAb rose to 52.18IU/L, and HBV DNA was measured at 1.28 log10 IU/ml. The patient was then transitioned to PEG-IFN monotherapy. In November 2021, the patient discontinued PEG-IFN therapy. One month later, laboratory tests confirmed that both HBV DNA (<10 IU/mL) and HBsAg were negative, and these results have been maitntained to date. Conclusion: This case demonstrates that sequential combination therapy can effectively treat chronic hepatitis B, even in patients with a long history of infection. This approach may lead to a shift to latent hepatitis B infection, and timely adjustments in treatment regimens based on monitoring indicators can ultimately result in a clinical cure.