Mutation of the “a” Determinant of HBsAg with Discordant HBsAg Diagnostic Kits

Abstract

Sera from 1003 in- and out-patients were investigated for hepatitis B surface antigen (HBsAg) mutation at Siriraj Hospital, Bangkok, Thailand. Individual samples were screened using two commercial HBsAg kits on automatic machine-based assays set up in parallel. The first kit was a sandwich ELISA kit that used monoclonal capture/monoclonal conjugate and color detection whereas the second was a sandwich MEIA, using monoclonal capture/polyclonal indicator and fluorochrome determination. Six specimens were found discordant by negative EIA and positive MEIA; two specimens of which were detectable of HBV DNA. Three out of four discordant results were confirmed by an anti-HBs neutralization assay. Based on direct sequencing, one HBsAg/anti-HBs sample with multiple mutations in the S gene was found. The mutation included the common glycine to arginine escape mutation at amino acid position 145 of the "a" determinant. The observation should alert the blood bank to the necessity of using screening kits capable of detecting HBV mutant carriers as well as providing verification for the phenomenon of vaccine-escape mutation in Thailand.

Sensitivities of Four New Commercial Hepatitis B Virus Surface Antigen (HBsAg) Assays in Detection of HBsAg Mutant Forms

“…The need for such information was recently underscored by a panel of experts in the field (7). The impact of HBsAg amino acid changes on immunoassay detection has been reported by several authors (6,13,14,16,18,19,20,30). However, these studies used diluted natural samples or recombinant antigens to reflect mutations described in the literature, as sufficient volumes of the natural samples are difficult to obtain.…”

“…Natural variation and mutations can induce HBsAg conformational changes. Since many HBsAg immunoassays use monoclonal antibodies with epitopes directed against the major hydrophilic region, in particular against the "a" determinant, amino acid substitution in this region may account for false-negative results in immunoassays (6,14,18,19,30).…”

Molecular analysis of the hepatitis B virus presurface and surface gene in patients from eastern China with occult hepatitis B

“…Multiple mutations were detected in five out of 11 samples (B9, D3, D6, D7, and D9) in Group I, which may affect the immunological detection of HBsAg in multiple ways that are still undefined. There have been several studies reporting a high frequency of multiple mutations from clinically immune escape mutants [Louisirirotchanakul et al, 2004;Wagner et al, 2004]. A mixed infection of pre-S/S gene mutant and wild-type virus was found in four samples in Group I (C54, C118, D6, and D8).…”

Comparison of the technical and clinical performance of the Elecsys® HBsAg II assay with the Architect®, AxSym®, and Advia® Centaur HBsAg screening assays

“…The Elecsys 1 HBsAg II assay (Roche Diagnostics, Mannheim, Germany), which has evolved from the Elecsys 1 HBsAg assay, is a new screening assay with improved ability to detect HBsAg mutants [Mü hlbacher et al, 2008]. This assay uses both monoclonal and polyclonal antibodies for HBsAg detection, which may confer advantages for mutant detection over assays that use monoclonal capture and tracer antibodies alone [Weber et al, 1999;Louisirirotchanakul et al, 2004]. The present multicenter study was carried out in nine leading medical centers in Thailand, Korea, and Singapore.…”