Novel immunoassay for the detection of hepatitis B surface 'escape' mutants and its application in liver transplant recipients

Hepatitis B virus (HBV) strains with mutations in the surface gene are resp onsible for the failure of prophylaxis with hepatitis B immunoglobulin (HBI G) in a proportion of patients transplanted for HBsAg positive cirrhosis. S o far, the emergence and evolution of these 'surface antibody escape' mutan ts have been studied by DNA sequencing. In this study the use of an immunoa ssay is described for diagnosis and characterisation of HBV recurrence afte r liver transplantation (OLT), based on a monoclonal antibody able to recog nise both wild-type and mutant HBsAg. Pre- and post-transplant samples from 22 patients transplanted for HBsAg positive cirrhosis were studied: Group A: 12 patients who reinfected the graft despite receiving HBIG; Group B: 6 patients with no HBV recurrence with continuous HBIG; Group C: 4 patients w ith HBV recurrence without prophylaxis. By running the new assay in paralle l with an immunoassay that is susceptible to HBsAg mutants, 4 of 12 cases w ere identified in Group A with HBV recurrence due to surface antibody escap e mutants, whereas in 8 patients this was due to the wild-type HBV. The res ults from the immunoassays were confirmed in all cases by HBV DNA sequencin g. The surface gene mutations in the 4 patients affected codons 144 and 145 and in one of these 4 patients HBV strains with mutations in both codons w ere detected before and after transplantation. The epitope recognised by th e new monoclonal antibody that reacts with both wild-type and mutant HBsAg seems to remain stable in the HBIG-induced HBV mutants. This serological ap proach allows rapid and cost-effective screening for HBsAg escape mutants i n the liver transplant setting and may be helpful in the selection of appro priate prophylaxis. J. Med. Virol. 63: 210-216, 2001. (C) 2001 Wiley-Liss, Inc.