*Purpose: Patients with Hepatitis B Core Antibody (anti-HBc Ab) positive are known to be at risk for Hepatitis B virus (HBV) reactivation during periods of immunosuppression, especially following CD20 depleting therapy such as Rituximab. Rituximab is increasingly used to treat highly sensitized transplant recipients. The incidence of HBV reactivation and the potential impact on transplant outcomes in Rituximab-treated kidney transplant recipients remain poorly understood. The objective of this study is to investigate the incidence of HBV reactivation in kidney transplant recipients (KTR) with positive anti-HBc Ab treated with Rituximab.

*Methods: This was a retrospective cohort study conducted at a large tertiary care transplant center. We studied Rituximab-treated KTR who were Anti-HBc Ab positive and Hepatitis B surface antigen (HBsAg) negative between January 2015 and June 2018. Data collection included demographics, HBV serologies, and ALT levels prior to and following Rituximab administration at intervals of 3, 6, 9 and 12 months.

*Results: A total of 55 patients were identified including 32 males and 23 females, with a median age of 52 years (range 21-75 years). The majority of the patients were African American (32, 58%), followed by Hispanic (12, 22%), and Caucasian (11, 20%). Prior to Rituximab, 49 patients were checked for Hepatitis surface antibody and only one patient tested negative. Most patients received Rituximab as part of antibody-mediated acute rejection protocol (50, 91%) for highly sensitized patients. Nine (16.3%) patients developed significant ALT elevation defined as more than 2 times the upper limit of normal with only 1 out of 9 patients treated with Hepatitis B prophylaxis (Emtricitabine). No single patient required treatment for HBV flare up. Nine patients had HBsAg checked at 6 months post Rituximab and 15 patients at 12 months post Rituximab; all negative. Only 1 patient had HBV DNA PCR checked post Rituximab at 12-month interval (undetectable).

*Conclusions: The overwhelming majority of patients included in the study did not undergo systematic monitoring for HBsAg or HBV DNA despite being at high risk for reactivation. Transplant clinicians need to be aware of the potential risk of HBV reactivation following Rituximab. Nonetheless, incidence of clinically significant HBV reactivation in Rituximab-treated KT patients seems lower than expected. Major limitation of the study included a variety of missing data due to its retrospective nature. Larger studies in this area are needed.

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