Is occult Hepatitis B virus infection with detectable anti-HBs infectious or not?

In the recent issue of Middle East Journal of Digestive Diseases, we read with great interest the article by Bahari et al.1, “Significance of response to hepatitits B vaccine in subjects with isolated antibody to hepatitis B core antigen”. We wanted to specify some important matters related to the article. Initially, definition of occult hepatitis B virus infection is the existence of hepatitis B virus (HBV) deoxyribonucleic acid (DNA) in the liver of individuals negative for hepatitis B surface antigen (HBsAg) by currently available assays.2 Serum HBV DNA titres may be detectable (usually very low, <200 IU/ml) or undetectable, and may show fluctuation in occult hepatitis B virus infection patients. Also, occult hepatitis B virus infection may occur not only seropositive for antibodies to hepatitis B core antigen (anti-HBc) and/or antibodies to HBsAg (anti-HBs), but also seronegative.2 Isolated anti-HBc positivity or anti-HBc alone, most commonly associated with occult hepatitis B virus infection, develops particularly because of the reduction of corresponding antibodies to undetectable levels after the resolution of infection.3 In this case, with HBV vaccination as implemented in the article, anti-HBs levels increase in a short time.1 However, isolated anti-HBc positivity can be seen in the begining of the convalescene period of current infection or with the reduction of HBsAg to undetectable levels after long-term inactive HBV carriage. The reduction of HBsAg levels can be shown by only high sensitive HBsAg assays and may be with low HBV DNA titres. Moreover, false isolated anti-HBc positivity has been reported up to 35% via repetitive tests.4,5 The more important topic is whether occult hepatitis B virus infection with detectable anti-HBs is infectious or not. Theoretically, high anti-HBs titres can neutralize the infectivity of virus particles, on the other hand, infection can emerge if the product to be transfused is positive for HBV DNA. HBV transmission from patients with occult hepatitis B virus infection with antiHBs positivity to immunocompetent recipients has been shown.6 In addition, it has also been reported that anti-HBs titres lower than 100 IU/ml have insufficient protectivity in the presence of HBV DNA and products containing HBV DNA may be infectious and may cause serious clinical status in patients with severe immun deficiency even though anti-HBs levels are high.6 AntiHBc positive donations are accepted only if HBV DNA is negative and antiHBs titres are at least 100 IU/ml in European Union countries and at least 200 IU/ml in Japan.7,8 Consequently, serological tests and vaccination of solely anti-HBc donors 1. GATA Haydarpasa Training Hospital, First Step Examination, Family Health Center And The Naval Academy Clinic Tuzla / Istanbul, Turkey. 2. GATA Training and Research Hospital, Department of Infectious Diseases, Kecioren/Ankara, Turkey Murat Afyon1*, Cumhur Artuk2