HBV Vaccine Escape Mutations in a Chronic Hepatitis B Patient Treated with Nucleos(t)ide Analogues

Abstract

The hepatitis B virus (HBV) polymerase (pol) gene completely overlaps with the envelope (S) gene. Nucleos(t)ide analogue (NA) resistance mutations in the pol gene of HBV, either from selection of primary or secondary resistance mutations, typically result in changes in the overlapping hepatitis B surface antigen (HBsAg). Recent studies have conferred a new acronym to these HBV pol/S gene overlap mutants; ADAPVEMs, for antiviral drug-associated potential vaccine-escape mutants. The present report aimed to assess the determined multiple HBV vaccine-escape mutants in a Turkish patient with chronic hepatitis B (CHB), undergoing NAs treatment. The liver biopsy of HBsAg positive, HBeAg negative 53-year old female patient with CHB, revealed a score as histological activity index; 9 and fibrosis; 2 according to Ishak classification. NA treatment backgrounds consisted of 24 months lamivudine, followed by 18 months entacavir and lastly 3 months tenofovir monotherapies. Since HBV DNA load was determined as 7.030.000 IU/ml at the 4th month of tenofovir therapy, entecavir was added as current treatment regimen, and tenofovir + entecavir therapy decreased the HBV DNA load (400 IU/ml). Sequence analysis was performed for HBV pol/S gene and overlapping pol/S gene amino acid substitutions, primary/compensatory NA resistance mutations and antiviral drug-associated potential vaccine-escape mutations (ADAPVEM) were analysed. The patient isolate was identified as genotype D/subgenotype D1 of HBV. Primary drug resistance mutations (rtV173L + rtL180M + rtM204V) to lamivudine and telbivudine and a compensatory mutation (rtQ215H) to lamivudine and adefovir were described in the HBV pol gene sequence. However, multiple HBV vaccine-escape mutations (sS143T + sD144E + sG145R + sE164D + sI195M) have been determined on the HBV overlapping pol/S gene region. Lamivudine and telbivudine which are the frequently preferred drugs for the treatment of CHB in Turkey, have the potential to lead to ADAPVEMs. Thus ADAPVEMs should be monitored in infected and NA treated CHB patients and their public health risks should be assessed.