Impacts of the G145R Mutation on the Structure and Immunogenic Activity of the Hepatitis B Surface Antigen: A Computational Analysis

Abstract

BackgroundVaccine-escaped hepatitis B virus (HBV) mutations occur within the “a” determinant area, which is located in the major hydrophilic region (MHR) of the hepatitis B surface antigen (HBsAg) protein. It is now well established that the common G145R mutation is highly capable of escaping from HBsAg immune recognition. However, the impacts of this mutation on the structure and immunogenic activity of HBsAg have been poorly investigated.ObjectivesThe present study analyzed the effects of the G145R mutation on the structure and immunogenic activity of the HBsAg.Materials and MethodsThree-dimensional (3D) structure of HBsAg for both the wild-type and G145R mutant were predicted and refined using several web tools. After quantitative evaluations, the effects of the G145R mutation on the secondary and 3D structures of the HBsAg were investigated. In parallel, the immunogenic activity of the wild-type and mutant HBsAg was also analyzed using a ClusPro docking server as well as the IEDB web tool. Further analyses were performed via molecular dynamics (MD) simulations using the GROMACS v5.0.2 simulation package.ResultsThe G145R mutation causes a considerable reduction in the immunogenic activity of the HBsAg through a conformational change in the HBsAg antigenic loops. This mutation inserts a new β-strand in the “a” determinant region of the HBsAg, leading to a reduced binding affinity to its monoclonal antibody, MAb12. The G145R mutation also increased the compactness and stability of the HBsAg by enhancing the rigidity of the “a” determinant.ConclusionsThese data will be beneficial for designing more advanced antibodies for the recognition of the HBsAg in diagnostics. In addition, the results of this study may assist in the design or development of more effective hepatitis B vaccines.

HBsAg mutations related to occult hepatitis B virus infection in HIV‐positive patients result in a reduced secretion and conformational changes of HBsAg

“…HBV vaccination imposes selection pressure on HBsAg leading on the development of MHR mutations, especially G145R [Carman et al, 1990;Alavian et al, 2013;Rezaee et al, 2016]. However, we did not find the G145R in our patients.…”

Genetic variation of hepatitis B surface antigen among acute and chronic hepatitis B virus infections in The Netherlands

“…The HBV genome is one of the most variable among DNA viruses. In particular, variation in the major hydrophobic region (MHR; amino acids 100 to 160) of the HBsAg has been related to reduced or absent immune/vaccine responses (immune/vaccine escape), may impact the detection of HBsAg, or lead to reactivation in persons with previously resolved infection or immunosuppressed persons (often receiving immunosuppressive treatment) with stable chronic infection . This study shows, for the first time, variation among acute HBV infections as well as a comparison of the HBsAg amino acid variation between acute and chronic infections.…”

“…Amino acid substitutions within the MHR can influence vaccine effectiveness as well as diagnostic sensitivity by affecting antibody binding either to the virus when infected or to antigens in a specific test . HBsAg substitutions have also been related to a decrease in antibody titers affecting test results or to reactivation in individuals with previously resolved infection or immunosuppressed individuals with stable chronic infection . As such, the circulation of variants, in particular, those affecting immune or vaccination response, is a major public health concern.…”

Analysis of Antigenic and Conformational Changes in Hepatitis B Surface Antigen (HBsAg) Identified in Iranian Patients with Chronic Hepatitis B

“…The G145R mutation was not observed in the current study. However, previous analyses of the G145R mutant indicated that this mutation inserted a new β-strand at the 121 to 124 position (24). The hydrophilic characteristic of the 'a' determinant provides flexibility of its antigenic loops for its interaction with antibodies.…”