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Abstract

The administration of immunosuppressive therapy is associated with reactivation of the hepatitis B virus (HBV) among individuals with chronic HBV infection. Screening for the hepatitis B surface antigen (HBsAg) is important prior to commencement of immunosuppressive therapy, and initiation of prophylactic antiviral therapy till 6-12 months after completion of immunosuppressive therapy is now advocated.HBV reactivation has also been reported in HBsAg-negative individuals, of which the only positive serologic marker is the antibody to the hepatitis B core antigen (anti-HBc), indicating past exposure to HBV. These individuals could have occult hepatitis B infection, defined as HBsAg-negative individuals with detectable HBV DNA in serum or liver. So far, �??occult�?� HBV reactivation has only been reported in certain types of immunosuppressive therapy: Anti-CD 20 (e.g. rituximab), anti-tumor necrosis factor therapy and hematopoietic stem cell transplantation. �??Occult�?� HBV reactivation rates vary, mainly because published studies are mainly retrospective with the lack frequent HBV DNA monitoring. Recent prospective data from our center showed a cumulative 40.5% HBV reactivation rate in 2 years among HBsAg-negative, anti-HBc positive lymphoma patients receiving rituximab-containing chemotherapy. Patients with a positive antibody to HBsAg (anti-HBs) at baseline had a lower rate of reactivation. Neverthless, these results cannot be extrapolated to all forms of immunosuppressive therapy; more prospective data would be needed. Prophylactic antiviral therapy for all HBsAg-negative, anti-HBc-positive individuals has also been suggested, but its cost-effectiveness in HBV-endemic countries, in which the seroprevalence of anti-HBc reaches 30-50%, needs further investigation.

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