title: Investigating the impact of hepatitis B virus surface gene polymorphism on antigenicity using ex vivo phenotyping.
abstract: The hepatitis B virus (HBV) surface antigen (HBsAg) is a complex protein, and understanding accurately the impact of amino acid changes on the antigenicity of the immunodominant a determinant must take this complexity into consideration. Epitope mapping with four mAbs was used to phenotype HBsAg directly from patients' sera to investigate the effect of mutations in their native genetic backbone. The expected mAb reactivity was established initially for samples harbouring 'wild-type' HBsAg sequences across genotypes A-E. The alteration of HBsAg antigenicity, defined by mAb epitope loss, was demonstrated in a number of samples with sequence-inferred amino acid changes. Individual mutations within the mapped epitopes to which the mAbs were directed usually affected their binding. However, the loss of more than one epitope was observed as the number of mutations within a sequence increased. Conversely, not all mutations occurring in the a determinant altered the HBsAg conformation. The genotype backbone, the specific amino acid substitution and amino acid changes occurring outside the major antigenic region appeared to be important in determining expression of the predicted epitope loss. These data clearly demonstrate that sequence-based methods alone may not accurately define HBsAg phenotype. This phenotyping methodology allows for the rapid and accurate identification of antigenically altered viruses and will greatly enhance current HBV surveillance, research and diagnostic activities. The data generated can be used to inform on public health issues relating to prevalence, transmission and impact of HBsAg mutants in HBV-infected populations.
authors.affiliation: Blood Borne Virus Unit, Virus Reference Department, Microbiology Services-Colindale, Health Protection Agency, 61 Colindale Avenue, London NW9 5EQ, UK.
authors.forename: Samreen
authors.initials: S
authors.lastname: Ijaz
authors.affiliation: Blood Borne Virus Unit, Virus Reference Department, Microbiology Services-Colindale, Health Protection Agency, 61 Colindale Avenue, London NW9 5EQ, UK.
authors.forename: Renata
authors.initials: R
authors.lastname: Szypulska
authors.affiliation: Statistics, Modelling and Economics Department, Health Protection Services-Colindale, Health Protection Agency, 61 Colindale Avenue, London NW9 5EQ, UK.
authors.forename: Nick
authors.initials: N
authors.lastname: Andrews
authors.affiliation: Division of Infection and Immunity, University College London, Gower Street, London WC1E 6BT, UK.|Transfusion Microbiology, NHS Blood and Transplant, Colindale Avenue, London NW9 5BG, UK.|Blood Borne Virus Unit, Virus Reference Department, Microbiology Services-Colindale, Health Protection Agency, 61 Colindale Avenue, London NW9 5EQ, UK.
authors.forename: Richard S
authors.initials: RS
authors.lastname: Tedder
mesh_terms: D000914:Antibodies, Viral; D018604:Epitope Mapping; D000939:Epitopes / Q000235:genetics; D005838:Genotype; D006514:Hepatitis B Surface Antigens / Q000235:genetics*; D006515:Hepatitis B virus / Q000235:genetics* / Q000378:metabolism*; D006825:Hybridomas; D009154:Mutation; D010641:Phenotype; D011110:Polymorphism, Genetic; D059467:Transcriptome
chemical_list: D000914:Antibodies, Viral; D000939:Epitopes; D006514:Hepatitis B Surface Antigens