E2 Site Mutations in S Protein Strongly Affect Hepatitis B Surface Antigen Detection in the Occult Hepatitis B Virus

The mechanism of occult hepatitis B infection (OBI) has not yet been fully clarified. Our previous research found that novel OBI-related mutation within S protein, E2G, could cause the hepatitis B surface antigen (HBsAg) secretion impairment, which resulted in intracellular accumulation in OBI of ge...

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Autores principales:	Hao Wang, Fenfang Liao, Junmo Xie, Wenbo Gao, Min Wang, Jieting Huang, Ru Xu, Qiao Liao, Zhengang Shan, Yourong Zheng, Xia Rong, Chengyao Li, Yongshui Fu
Formato:	article
Lenguaje:	EN
Publicado:	Frontiers Media S.A. 2021
Materias:	hepatitis B virus occult hepatitis B infection mutation hepatitis B surface antigen HBsAg secretion impairment Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/7f984c56d06f440387a1e4408539d0a2
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spelling	oai:doaj.org-article:7f984c56d06f440387a1e4408539d0a22021-11-10T08:18:33ZE2 Site Mutations in S Protein Strongly Affect Hepatitis B Surface Antigen Detection in the Occult Hepatitis B Virus1664-302X10.3389/fmicb.2021.664833https://doaj.org/article/7f984c56d06f440387a1e4408539d0a22021-11-01T00:00:00Zhttps://www.frontiersin.org/articles/10.3389/fmicb.2021.664833/fullhttps://doaj.org/toc/1664-302XThe mechanism of occult hepatitis B infection (OBI) has not yet been fully clarified. Our previous research found that novel OBI-related mutation within S protein, E2G, could cause the hepatitis B surface antigen (HBsAg) secretion impairment, which resulted in intracellular accumulation in OBI of genotype B. Here, to further explore the role of E2 site mutations in the occurrence of OBI, we analyzed these site mutations among 119 OBI strains identified from blood donors. Meanwhile, 109 wild-type HBV strains (HBsAg positive/HBV DNA positive) were used as control group. Furthermore, to verify the E2 site mutations, two conservative 1.3-fold full-gene expression vectors of HBV genotype B and C (pHBV1.3B and pHBV1.3C) were constructed. Then, the E2 mutant plasmids on the basis of pHBV1.3B or pHBV1.3C were constructed and transfected into HepG2 cells, respectively. The extracellular and intracellular HBsAg were analyzed by electrochemical luminescence and cellular immunohistochemistry. The structural characteristics of S proteins with or without E2 mutations were analyzed using relevant bioinformatics software. E2 mutations (E2G/A/V/D) existed in 21.8% (26/119) of OBIs, while no E2 mutations were found in the control group. E2G/A/V/D mutations could strongly affect extracellular and intracellular level of HBsAg (p < 0.05). Notably, unlike E2G in genotype B that could cause HBsAg intracellular accumulation and secretion decrease (p < 0.05), E2G in genotype C could lead to a very significant HBsAg decrease both extracellularly (0.46% vs. pHBV1.3C) and intracellularly (11.2% vs. pHBV1.3C) (p < 0.05). Meanwhile, for E2G/A mutations, the relative intracellular HBsAg (110.7–338.3% vs. extracellular) and its fluorescence intensity (1.5–2.4-fold vs. with genotype-matched pHBV1.3B/C) were significantly higher (p < 0.05). Furthermore, N-terminal signal peptides, with a typical cleavage site for peptidase at positions 27 and 28, were exclusively detected in S proteins with secretion-defective mutants (E2G/A). Our findings suggest that: (1) E2G/A/V/D mutations were confirmed to significantly influence the detection of HBsAg, (2) the underlying mechanism of OBI caused by E2G mutation is quite different between genotype B and genotype C, and (3) E2G/A could produce a N-terminal truncated S protein, which might attribute to the HBsAg secretion impairment in the OBIs.Hao WangFenfang LiaoJunmo XieWenbo GaoMin WangJieting HuangRu XuQiao LiaoZhengang ShanYourong ZhengXia RongChengyao LiYongshui FuFrontiers Media S.A.articlehepatitis B virusoccult hepatitis B infectionmutationhepatitis B surface antigenHBsAg secretion impairmentMicrobiologyQR1-502ENFrontiers in Microbiology, Vol 12 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	hepatitis B virus occult hepatitis B infection mutation hepatitis B surface antigen HBsAg secretion impairment Microbiology QR1-502
spellingShingle	hepatitis B virus occult hepatitis B infection mutation hepatitis B surface antigen HBsAg secretion impairment Microbiology QR1-502 Hao Wang Fenfang Liao Junmo Xie Wenbo Gao Min Wang Jieting Huang Ru Xu Qiao Liao Zhengang Shan Yourong Zheng Xia Rong Chengyao Li Yongshui Fu E2 Site Mutations in S Protein Strongly Affect Hepatitis B Surface Antigen Detection in the Occult Hepatitis B Virus
description	The mechanism of occult hepatitis B infection (OBI) has not yet been fully clarified. Our previous research found that novel OBI-related mutation within S protein, E2G, could cause the hepatitis B surface antigen (HBsAg) secretion impairment, which resulted in intracellular accumulation in OBI of genotype B. Here, to further explore the role of E2 site mutations in the occurrence of OBI, we analyzed these site mutations among 119 OBI strains identified from blood donors. Meanwhile, 109 wild-type HBV strains (HBsAg positive/HBV DNA positive) were used as control group. Furthermore, to verify the E2 site mutations, two conservative 1.3-fold full-gene expression vectors of HBV genotype B and C (pHBV1.3B and pHBV1.3C) were constructed. Then, the E2 mutant plasmids on the basis of pHBV1.3B or pHBV1.3C were constructed and transfected into HepG2 cells, respectively. The extracellular and intracellular HBsAg were analyzed by electrochemical luminescence and cellular immunohistochemistry. The structural characteristics of S proteins with or without E2 mutations were analyzed using relevant bioinformatics software. E2 mutations (E2G/A/V/D) existed in 21.8% (26/119) of OBIs, while no E2 mutations were found in the control group. E2G/A/V/D mutations could strongly affect extracellular and intracellular level of HBsAg (p < 0.05). Notably, unlike E2G in genotype B that could cause HBsAg intracellular accumulation and secretion decrease (p < 0.05), E2G in genotype C could lead to a very significant HBsAg decrease both extracellularly (0.46% vs. pHBV1.3C) and intracellularly (11.2% vs. pHBV1.3C) (p < 0.05). Meanwhile, for E2G/A mutations, the relative intracellular HBsAg (110.7–338.3% vs. extracellular) and its fluorescence intensity (1.5–2.4-fold vs. with genotype-matched pHBV1.3B/C) were significantly higher (p < 0.05). Furthermore, N-terminal signal peptides, with a typical cleavage site for peptidase at positions 27 and 28, were exclusively detected in S proteins with secretion-defective mutants (E2G/A). Our findings suggest that: (1) E2G/A/V/D mutations were confirmed to significantly influence the detection of HBsAg, (2) the underlying mechanism of OBI caused by E2G mutation is quite different between genotype B and genotype C, and (3) E2G/A could produce a N-terminal truncated S protein, which might attribute to the HBsAg secretion impairment in the OBIs.
format	article
author	Hao Wang Fenfang Liao Junmo Xie Wenbo Gao Min Wang Jieting Huang Ru Xu Qiao Liao Zhengang Shan Yourong Zheng Xia Rong Chengyao Li Yongshui Fu
author_facet	Hao Wang Fenfang Liao Junmo Xie Wenbo Gao Min Wang Jieting Huang Ru Xu Qiao Liao Zhengang Shan Yourong Zheng Xia Rong Chengyao Li Yongshui Fu
author_sort	Hao Wang
title	E2 Site Mutations in S Protein Strongly Affect Hepatitis B Surface Antigen Detection in the Occult Hepatitis B Virus
title_short	E2 Site Mutations in S Protein Strongly Affect Hepatitis B Surface Antigen Detection in the Occult Hepatitis B Virus
title_full	E2 Site Mutations in S Protein Strongly Affect Hepatitis B Surface Antigen Detection in the Occult Hepatitis B Virus
title_fullStr	E2 Site Mutations in S Protein Strongly Affect Hepatitis B Surface Antigen Detection in the Occult Hepatitis B Virus
title_full_unstemmed	E2 Site Mutations in S Protein Strongly Affect Hepatitis B Surface Antigen Detection in the Occult Hepatitis B Virus
title_sort	e2 site mutations in s protein strongly affect hepatitis b surface antigen detection in the occult hepatitis b virus
publisher	Frontiers Media S.A.
publishDate	2021
url	https://doaj.org/article/7f984c56d06f440387a1e4408539d0a2
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E2 Site Mutations in S Protein Strongly Affect Hepatitis B Surface Antigen Detection in the Occult Hepatitis B Virus

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