Role of HBV DNA mutations in HBV recurrence in liver transplant recipients

End-stage liver disease due to HBV is an important indication for liver transplanation in Turkey. Re-infection of the greft tissue with HBV in patients who underwent orthotopic liver transplantation increases mortality and morbidity, and still remains an important problem. Hepatitis B immune globulin (HBIG) and reverse transriptase (RT) inhibitor agents, which are used as prophylactic measures to prevent greft re-infection, exert selective pressure on the HBV virus, which may lead to selection of viral mutants that are less sensitive to treatment, resulting in HBV recurrence.In this study, we aimed to reveal the mutation profile of HBV in liver transplant patients with recurrent HBV disease having positive plasma HBV DNA despite prophylaxis. The study population was consisted of patients who underwent orthotopic liver transplantation in Dokuz Eylül University Hospital between 01/02/1997 ? 06/08/2009 with positive plasma HBV DNA in post-transplantion period. PreS/S and RT regions of HBV DNA were obtained by PCR, and amplicons were sequenced using Sanger?s method. Mutations and variations were determined by comparing with reference sequences.Sequence analysis of HBV in 13 patients who had plasma HBV DNA positivity post transplant revealed anti-viral resistance mutations in five patients (38.5%), antibody escape mutations in the S gene in three patients (23.1%), and both type of mutations in three patients (23.1%). Two patients did not show any mutations (15.4%). Nine patients had HBsAg positivity along with HBV DNA positivity in the post-transplantation period. The evaluation of patients in this group revealed anti-viral resistance mutations in three patients (33.3%), antibody escape mutations of the S gene in three patients (33.3%), and both types of mutations in three patients (33.3%). All patients had at least one type of mutation that may be attributed to recurrence. It was possible to sequence pre-transplant samples of three patients among eight who showed anti-viral resistance and the sequences showed the presence of anti-viral resistance mutations before the transplantation.Mutations related to antibody escape found in this study are as follows: sY100C, sT118K, sP120T, sT123A, sT131N, sM133L, sD144A. One of the most frequently reported antibody escape mutations in the literature, sG145R, was not present in any of the patients. In one patient, sN146H was present within the ?a? determinant. Search of the literature did not reveal any information about this mutation.Resistance patterns post-transplantation period were rtL80I + L180M + A181V + M204V; rtL180M + S202G + M204V; rtL180M + M204V; rtM204I + L80V; rtM204I + L80I; rtM204I; rtA181V.Two patients (15,4%) had deletions in the PreS2 region. In one patient, there was a mutation in the S promoter of the preS1 region, located within the CCAAT box (CCAAT ? CCAAG).The antiviral resistance mutation rate found in the study population with HBV recurrence (66.6%) was comparable to similar studies in the literature (47-59%). Pre-transplant mutations mostly continued to be present in the post-transplant samples. Therefore, mutation analysis of patients with positive HBV DNA despite the use of anti-viral drugs, in the pre-transplantation period may help determine the right prophylaxis option after the tranplantation in order to prevent the HBV recurrence.