Detection of HBsAg mutants

Abstract

HBsAg screening is carried out routinely to detect hepatitis B virus (HBV) infection. The immunoassays used employ capture antibodies often having specificity for epitopes present on the antigenic (a) determinant of the HBsAg. Loss of detection may occur due to mutations within and/or outside of the a determinant that affect conformational epitope recognition or HBsAg secretion or expression. Most of the mutations associated with immune escape occur within the second loop of the a determinant. In order to detect these HBsAg mutants, antibodies to subdominant regions within the a determinant or outside of the HBsAg may be required, and this has been the focus of many recent studies. Any changes to immunoassay formulations should also address the possible effect of HBV genotypic polymorphisms on assay specificity and sensitivity. HBsAg mutants may also be identified through nucleic acid detection of HBV in serum. Various molecular analysis methods have been developed to provide specific and sensitive detection of HBsAg mutants, including sequencing, limiting dilution cloning PCR (LDC-PCR), gap ligase chain reaction (gLCR), and real time PCR. Sequencing the HBsAg coding region provides specific information on the nucleotide sequence; however, it is relatively insensitive for the detection of minority quasispecies. Other nucleic acid methods offer greater sensitivity for the detection of point mutations. To improve immunoassays, further research will be required to increase detection sensitivity and specificity. Ultimately, a better understanding of the structure of antibody-bound HBsAg will help identify the immunological targets required for the accurate detection of HBsAg in blood.

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

“…Whereas the potential significance of G145R point mutation in immune escape has been observed in some studies [Carman et al, 1990;Kalinina et al, 2003;Osiowy, 2006;Shahmoradi et al, 2012], this study did not show a high frequency of this specific mutation. G145R/A mutations were identified in two patients with occult hepatitis B while G145E was found in one patient with chronic hepatitis B.…”

“…G145 mutations were identified in 18% of patients with occult hepatitis B, which is comparable to the 23% frequency of G145R described in Chinese blood donors with occult hepatitis B reported by Yuan et al [2010]. In patients with chronic hepatitis B, a G145 mutation was identified in 3.6%, which was within the 3-8% range of G145R mutants detected in samples suspected of having an HBsAg mutant based on clinical and diagnostic information [Osiowy, 2006].…”

“…G145R is generally considered the main mutational site for HBV immune escape [Carman et al, 1990;Tabor, 2006;Shahmoradi et al, 2012]. Pre-S/S gene mutations which overlap the polymerase gene can contribute to immune escape and occult hepatitis B [Weber, 2005;Osiowy, 2006] by affecting the secretion and stability of the virus leading to a low circulating viral load [Kalinina et al, 2003;Khan et al, 2004]. These mutations also can lead to a failure in HBV clearance and reduced reactivity in routine serological tests.…”

Microarray for Hepatitis B Virus Genotyping and Detection of 994 Mutations along the Genome

“…As the assay is able to identify 994 mutations, it was not possible to assemble a panel of samples covering all of them. We established a short list of positions with the highest relevance for HBV biology and disease monitoring (10,23,37). The results obtained at these positions are presented in Table 4 and detailed below.…”

Occult Infection pada Anak Setelah 10 Tahun Mendapat Imunisasi Hepatitis B

“…Mutasi pada gen VHB dapat terjadi pada gen S, gen precore, gen core, dan gen polymerase. 4 Dampak OBI adalah hepatitis kronik, atypical alcoholic hepatitis dan KHS, reaktivasi virus, dan transmisi pada tranfusi dan transplantasi organ. 5 Di Tiongkok, ditemukan occult infection hepatitis B pada genotip C, Hsia dkk 6 mendapatkan bahwa 31 orang penderita KHS dengan OBI adalah 55%-56%, sedangkan Kiiree dkk 7 menemukan 17% di Sinegal.…”